AMSAT Fox-1 Systems Engineering Documentation
By Jerry Buxton, N0JY
Fox-1 Systems Engineer
n0jy@amsat.org
The AMSAT Fox program introduced a new engineering process for AMSAT in which
engineering documentation is provided at each stage of development. We are archiving all of thisdocumentation on an on-line, backed-up, version control server. When the satellite has been
completed, we will have an archive of traceable documentation. This can serve as the basis forplanning and executing future satellite programs and can be updated to apply the lessons learnedof what went well and what did not.
AMSAT is a truly unique organization in that we are a non-profit corporation that manufacturessatellites using a geographically distributed, all-volunteer engineering staff. There are nocommon or established guidelines to cover our situation. As such, the Fox program engineering
practices are themselves a work in progress. The practices used are drawn from industry
sources, especially NASA1 and IEEE.
AMSAT has adopted a common industry scheme known as numbered requirements. Eachindividual requirement has a unique number assigned to it. The number allows a very precise
reference to a specific requirement and this enhances the overall traceability of the specifications.
Design documents use these references to show which module or subsystem is responsible andhow they are meeting each of the requirements. The requirements are tracked throughout the
documents using requirements tracking software, from the ConOps down to the test results, inorder to verify that all requirements are properly implemented.
Due to US State Department ITAR2 restrictions, our document server is only available to project
members who have been vetted to meet the requirements for a "US-person." AMSAT, as an
educational organization, would like to publicly release the majority of our design
documentation to serve as a learning tool to anyone interested in satellite development. However,this must be done in a specific way to meet the ITAR requirements. The information must firstbe released via an openly available publication.
We would also like to be able to discuss our satellite projects with our own members, some ofwhom are not "US-persons" per ITAR. These AMSAT Space Symposium proceedings provide aconvenient mechanism for the needed publication in order to make this information publicdomain and allow us to communicate with our members.
While the Concept of Operations (ConOps) and System Requirements Specification were
published in the Proceedings of the AMSAT-NA 29th Space Symposium and AMSAT-NA Annual
Meeting, the System Requirements Specification has undergone changes and will be reproducedin these Space Symposium proceedings.

In addition these proceedings will also present new engineering documents including the System
Design Specification, Experiment Payload Requirements, IHU to RF System Interface Control
Document, IHU to PSU Interface Control Document, IHU to Battery Interface Control
Document, IHU to Attitude Determination Experiment Interface Control Document, and IHU
Software Architecture Specification. An introduction to each of these documents follows.
The System Requirements Specification is a document that provides the top level technicalspecifications derived from the ConOps. This document describes what the system should do.
The inputs, outputs, functions, mass, volume, environment and other external characteristics areincluded and specified in the system requirements. The level of detail for each requirement is
specifically chosen to provide a clear definition of what the systems will do without too muchspecific detail or declaring how it will be done. This allows the engineers latitude in designing
the best approach to satisfying the requirement.
The Avionics System Design Specification is a document that does provide specific details of
how the system will be designed. The specifications are based on best design choices
determined by the teams. The signals, connections, connectors, volume, and requirements
specific to each system are stated in this document so that each system will fit together andfunction with the other systems.
The Experiment Payload Requirements are a smaller level of system requirements written
specifically for the Penn State student designed attitude determination system. While the actual
system designed by the students was not constructed before their graduation, the experiment
payload system design itself will be incorporated onto the IHU board and this document
describes the necessary functions of the system although revised to remove the physicalrequirements of a separate printed circuit board.
The Interface Control Documents (ICD) for the IHU to RF System, IHU to PSU, IHU to Battery,and IHU to Attitude Determination Experiment set the requirements for connections andcommunication between the IHU and the various systems. Each of the systems sends telemetry
measurements and other signals to the IHU. The IHU sends telemetry audio and control signals
to the RF System. The ICD allows the systems teams to work independently, knowing that theirsystems will interface successfully.
The IHU Software Architecture Specification provides the design specifications needed for thesoftware design and operation of the Internal Housekeeping Unit.
The engineering documents published in these proceedings are what was available at timeneeded for inclusion and are intended to be interesting and informative. They may have changed
since publication. AMSAT intends to continue to make the majority of the final technicaldocuments, exclusive of satellite control information, available in future publications.
Some other documents are included in these proceedings because they contain additional
information about Fox-1 that may be of interest to our members.

Also included here are Antenna Details showing the EZNEC 5.0+ models of the 2 meter and 70
centimeter antennas used on the satellite. Thank you to David Ping, WB6DP.
The IHU Software Components is included to show a breakdown of the software systems thatwere developed and written for the STMicroelectronics STM32L151 ultra-low-power 32-bit
MCU, used for the IHU. Thank you to Bill Reed NX5R.
The Fox-1 Downlink Power Amplifier is a presentation of the findings during the prototype
testing of the 2 meter PA that will be used for RF downlink. Thank you to Marc Franco, N2UO.
Receiving FOX-1 Satellite on 2 meters is a link budget for the 2 meter downlink based on the
400 mW (minimum) output of the Fox-1 power amplifier. Thank you to Tony Monteiro,
AA2TX.
The Fox-1 Experimental Payload document is an IEEE presentation of their experiment given by
the Penn State students. Thank you to Mike Corona, Brandon Marvenko, and Edward Pizzella.

1

NASA Systems Engineering Handbook, NASA/SP-2007-6105 Rev1
International Traffic in Arms Regulations, see:
http://www.pmddtc.state.gov/regulations_laws/itar_official.html
2

AMSAT Fox-1
System Requirements
Date: September 4, 2012
Version: Version 1.12

AMSAT Fox-1
System Requirements Specification
1 Introduction
This document specifies the system level technical requirements for the AMSAT Fox-1
satellite project. This 1 Unit CubeSat is a part of the AMSAT Fox program and includes a
subset of the technical capabilities envisioned for the overall program.
Fox-1 is specifically intended as a replacement for the failing AMSAT Echo (i.e. AO-51)
satellite. Echo has been the most widely used amateur satellite due to its ability to provide
basic radio communications with very simple ground station equipment. Its FM repeater
provides very wide geographical coverage allowing amateur radio operators tocommunicate over substantial distances using just a handheld transceiver (i.e. a walkietalkie) and a small handheld antenna. This so called "EasySat" mode is extremely
valuable in providing an introduction to satellite communications and is often used fordemonstrations given at schools, to scouting organizations and at amateur radio publicity
events. Fox-1 will not duplicate all of the features and modes of Echo but its primary
mission is to provide an FM Transponder in order to allow continued access to thisEasySat mode of communications.
In addition to its mission as a communications satellite, Fox-1 will host an experiment
payload. The satellite will reserve mass and volume for the experiment and will provide
DC power and a communications facility. The experiment is expected to be provided by
students at Penn State University – Erie through an AMSAT sponsored senior design
project.

AMSAT Fox-1
System Requirements
1.1

Document History
DATE

VERSION

SUMMARY

October 5, 2011

1.0

From Draft E

October 8, 2011

1.01

Fix typos in sections 1.2 and 3.5

October 9, 2011

1.02

Add Requirements Tracking

October 23, 2011

1.03

Additional Requirements Tracking

February 21, 2012

1.04

Update Section 3 and Formatting changes

April 18, 2012

1.05

Correction in Section 4

April 22, 2012

1.06

Correct link in Section 1.4 item 2

April 29, 2012

1.1

Revised 3.12.3, 3.12.7, 3.12.8, 3.13.3,
3.13.4, figure 1 to remove RESET and add
IHU OFF and IHU ON commands

August 2, 2012

1.11

Added hidden text for requirements tracking
to be shown in System Design Specification

September 4, 2012

1.12

Added the previously missing “Table 6”
label

AMSAT Fox-1
System Requirements
1.2 Document Scope
The purpose of this document is to specify the technical requirements of the satellite at
the system (i.e. "black box") level. It is intended to be used by the hardware, software andmechanical designers to develop the architecture/high-level design specifications. It isalso intended to be used for test planning and development.
1.3 Document Format
This document provides the requirements in numbered format. Each requirement is
assigned a unique number. Additional information such as comments or examples thatare provided for guidance or clarity is italicized to distinguish them from requirements.
1.4 References
1. AMSAT Fox-1, Concept of Operations, Version 1.0, September 19, 2011
2. CubeSat Design Specification Rev. 12. by The CubeSat Program Cal Poly SLO
available from: http://www.cubesat.org/images/developers/cds_rev12.pdf
3. Launch Services Program, Program Level Poly Picosatellite Orbital Deployer(PPOD) and CubeSat Requirements Document LSP-REQ-317.01 Revision Basic(from NASA)
4. ITU Radio Regulations, Edition of 2008. available fromhttp://www.itu.int/publ/R-REG-RR-2008/en

AMSAT Fox-1
System Requirements

2 General Requirements
2.1

CubeSat Requirements

2.1.1 The satellite shall meet the requirements specified in the CubeSat Design
Specification Rev. 12.
2.1.2 The satellite shall meet the requirements specified in the NASA LSP-REQ317.01 Revision Basic.
2.1.3 The satellite shall meet the requirements for a 1 unit (single) CubeSat.
2.1.4 The satellite shall provide mass for an experiment payload up to 100 g.
2.1.5 The satellite shall provide volume for an experiment payload up to 95 x 95
x 15.7 mm.
2.2

Environmental Requirements

2.2.1 The satellite avionics shall be designed for -40C to +70C operating
temperature.
2.2.2 The satellite shall be designed to operate in a 650 km, sun-synchronous,
circular orbit.
2.2.3 The satellite shall be designed to tolerate the radiation environment inorbit.
2.3

Reliability Requirements

2.3.1 The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
2.4

RF Frequency Requirements

2.4.1 All RF transmitters shall meet or exceed the requirements specified in the
ITU Radio Regulations, Technical Characteristics, Volume 3, article 3.
2.4.2 All satellite uplinks shall be in the 70 cm band of the amateur satellite
service.
2.4.3 All satellite downlinks shall be in the 2 meter band within the amateur
satellite service.
2.4.4 All satellite transmitter and receiver frequencies shall deviate by no morethan 5 parts-per-million from the specified values including initial accuracy
and temperature variation.
2.4.5 All satellite frequencies shall be coordinated with the IARU.
Note that the band plan with the actual coordinated frequencies will be specified in a
separate document.

AMSAT Fox-1
System Requirements

3 Functional Requirements
3.1

Antenna System

3.1.1 The satellite shall include a deployable antenna system.
3.2

Attitude Control

3.2.1 The satellite shall incorporate passive magnetic stabilization to align the
deployed antennas with the magnetic field of the earth.
3.3

Access Ports

3.3.1 The satellite shall include a "Remove Before Flight" pin as per the CubeSat
Design Specification.
3.3.2 The satellite shall include an umbilical port as per the CubeSat Design
Specification.
3.4

Pre-launch Features

3.4.1 The satellite battery and photovoltaic panels shall be electronicallydisconnected from the avionics when the "Remove Before Flight" pin is
inserted, regardless of the state of the deployment switch(es).
3.4.2 The satellite shall provide the means to charge the battery via the umbilicalport while integrated with the P-POD.
3.4.3 The satellite shall provide the means to run diagnostic tests via theumbilical port while integrated with the P-POD.
3.5

Power

3.5.1 The satellite shall produce electrical power from sunlight.
3.5.2 The satellite shall produce electrical power while in sunlight regardless oforientation and while tumbling or spinning.
3.5.3 The satellite shall produce sufficient average electrical power to operatecontinuously in the orbit of maximum eclipse.
3.5.4 The satellite shall provide sufficient battery capacity to operatecontinuously in the orbit of maximum eclipse.
3.5.5 If the battery fails, including a short-circuit condition, the satellite shallcontinue to operate using only the photovoltaic panel power when insunlight.

AMSAT Fox-1
System Requirements
3.6

Experiment3.6.1 The satellite shall provide current limited DC power for an experiment
payload.
3.6.2 The satellite shall provide a means to activate and deactivate theexperiment payload.
3.6.3 The satellite shall provide a means to telemeter data from the experiment
payload.
Note that the experiment payload will be specified in a separate document.
3.7

RF Uplink

3.7.1 The satellite shall include an FM uplink receiver.
3.7.2 The

receiver

shall

have

specifications

as

shown

in

Table

Table 1

Sensitivity
FM Deviation
Audio Bandwidth
Input Frequency Acceptance

3.8-120 dBm for 12 dB SINAD (min.)
5 kHz
3 kHz
Receiver shall accept signals that are off
frequency by ±2.5 kHz (min.)

RF Downlink

3.8.1 The satellite shall include an FM downlink transmitter.
3.8.2 The transmitter shall have specifications as shown in Table 2.
Table 2

Power Output
400 mW (min.)FM Deviation
5 kHz
Audio Bandwidth 3 kHz

1.

AMSAT Fox-1
System Requirements
3.8.3 The transmitter shall provide a means to prevent over modulation.
3.9

FM Transponder

3.9.1 The satellite shall provide an FM transponder via the RF uplink and RF
downlink.
3.9.2 The transponder shall detect the presence of a 67 Hz CTCSS tone on the
uplink.
3.9.3 The downlink transmitter shall be keyed (i.e. PTT-on) for 2 minutes
following detection of the 67 Hz CTCSS tone.
3.9.4 The downlink transmitter shall stay on continuously as long as the 67 Hz
CTCSS tone is detected at least once every 2 minutes on the uplink.
3.9.5 The 67 Hz CTCSS tone is not required for a received signal to be repeatedon the downlink, once the transmitter has been keyed.
3.9.6 If the downlink transmitter has been un-keyed for a period of 5 minutes, thesatellite shall send " HI THIS IS AMSAT FOX " in Morse code via a keyedaudio tone on the downlink transmitter.
3.9.7 The satellite shall default to Transponder Mode in the event of an IHU
processor failure.
3.10 Telemetry Data
3.10.1 The satellite shall collect telemetry data.
3.10.2 The telemetry data shall include measured parameters as shown in Table
3.
Table 3

Parameter NameCELL VPANEL VTOTAL IPA I
BATTERY T
PANEL T
PA T
OSC T

Description
Voltages of battery cells
Voltages of solar panels
Total DC current out of power system
DC current into RF power amp
Temperature of battery
Temperatures of solar panels
Temperature of RF power amp
Temperature of RF oscillators

3.10.3 The measured parameters shall be sampled at least every 15 seconds.
3.10.4 The minimum and maximum values of each of the measured parameters
shall be saved in non-volatile memory.
3.10.5 The telemetry data shall also include calculated parameters as shown in
Table 4.

AMSAT Fox-1
System Requirements
Table 4

Parameter Name Description
UP TIME
Total seconds since avionics power-up or reset
SPIN
Satellite spin rate and direction
3.10.6 A telemetry frame shall include the current measured values, the saved
minimum and maximum values, and the current calculated values.
Note that the telemetry interface will be specified in a separate document.
3.11 Telemetry Transmission
3.11.1 The satellite shall send telemetry using FSK on the RF downlink.
3.11.2 The FSK shall use the frequency spectrum below the audible range.
3.11.3 The telemetry shall be transmitted simultaneously with any transponder
communications.
3.11.4 The telemetry transmission shall include telemetry frames.
3.11.5 The telemetry transmission shall include experiment data.
3.12 Command Capability
3.12.1 The satellite shall provide the means to process commands sent via the
RF uplink from a ground control station.
3.12.2 The commands received via the RF uplink shall not be repeated on the
RF downlink.
3.12.3 The following commands shall be provided, as shown in Table 5.
Table 5

CommandTESTINHIBITIHU OFFIHU ON
CLEAR
TRANSPONDER MODE
COMMAND MODE

Operation
Send test message
Inhibit RF transmission
Power off IHUPower on IHUClear stored telemetry
Enter Transponder Mode
Enter Command ModeAMSAT Fox-1
System Requirements
3.12.4 A TEST command shall cause the satellite to respond by sending " TESTTEST TEST " in Morse code via a keyed audio tone on the RF downlink.
3.12.5 An INHIBIT command shall cause the satellite to cease RF transmissions.
3.12.6 Any command other than INHIBIT shall remove a transmit inhibit
condition.
3.12.7 An IHU OFF command shall cause the IHU System to power off.
3.12.8 An IHU ON command shall cause the IHU System to power on.
3.12.9 A CLEAR command shall cause the satellite to clear the saved minimum
and maximum telemetry parameter values.
3.12.10 A TRANSPONDER MODE command shall cause the satellite to enter
the Transponder Mode.
3.12.11 A COMMAND MODE command shall cause the satellite to enter theCommand Mode.
Note that the control interface will be specified in a separate document.

AMSAT Fox-1
System Requirements
3.13 On-Orbit Operating Modes
3.13.1 The satellite shall provide on-orbit operating modes as shown in Table 6.
Table 6

Name
Startup Mode
Transponder Mode
Command Mode

Description
Wait 45 minutes and deploy antennas
FM transponder and telemetry active
Telemetry active, no FM transponder

3.13.2 The satellite shall transition between modes as shown in Figure 1.

Figure 1. On-Orbit Operating ModesAMSAT Fox-1
System Requirements
3.13.3 Upon power-up of the avionics, the satellite shall begin operation from the"Power-up" state as shown in Figure 1.
3.13.4 An IHU ON Command shall cause the satellite to begin operation from the"Power-up " state as shown in Figure 1.
3.13.5 If the antennas have been deployed, the satellite shall enter theTransponder Mode.
3.13.6 If the antennas have not been deployed, the satellite shall enter theStartup Mode.
3.13.7 In Startup Mode, the satellite shall wait 45 minutes, deploy the antennas
and then enter Transponder Mode.
3.13.8 In Transponder Mode, the transponder and the telemetry shall be active.
3.13.9 In Command Mode, the telemetry shall be active and the transponder
shall not be active. (i.e. signals that appear on the uplink shall not be
repeated on the downlink.)
3.13.10 If another Command Mode command is not received, the satellite shall
automatically enter Transponder Mode 24 hours after having entered
Command Mode.
3.13.11 The RF uplink shall be monitored for commands in all modes.

4 External Interface Documents
To fully specify the satellite technical requirements, the following documents
must also be provided;
1. IARU Coordinated Frequency Plan
2. Telemetry Interface Specification
3. Control Interface Specification
4. Experiment Payload Specification

5 Summary
The Fox-1 satellite will be AMSAT's first CubeSat. Its primary mission is toprovide an FM Transponder communications capability. The secondary mission
is to host a university-provided experiment payload.

AMSAT Fox-1
Avionics System Design Specification
Date: September 30, 2012
Version: 3.14

AMSAT Fox-1
Avionics System Design Specification
1 Introduction
This document contains the system level design specifications for the AMSAT Fox-1 satellite
avionics systems. It is driven by the System Requirements Specification and otherdocuments provided by the developers of the individual systems that make up the satellite
system.
1.1. Document History
DATE

VERSION

SUMMARY

February 21, 2012

1.0

From Draft F

April 9, 2012

1.1

Add signal characteristics, update bus pin connections per
System Team input

April 17, 2012

1.2

Add external connector specification in sections 2.6, 2.12
and 2.14 and references in section 6

April 18, 2012

1.21

Add MMCX connectors gender

April 22, 2012

1.3

Minor corrections in signal characteristics, remove +Z
antenna deploy and sensor connections

July 10, 2012

2.0

Many revisions from PDR

July 11, 2012

2.01

One RBF pin removed from bus pin assignments, updated
2.1 interconnect diagram, updated 2.1 signal characteristics

July 21, 2012

2.1

Revised bus signals, bus pin assignments
Updated RF block diagram

July 22, 2012

2.11

Revision to some RF signal descriptions, change
antenna/coax connectors to UMCC type, updated RF block
diagram, added driving and load system columns to signal
characteristics

September 9, 2012

3.0

Major changes.

September 11, 2012

3.01

Defunct IHU block diagram pending update

September 12, 2012

3.1

Added PCB volume requirements

September 23, 2012

3.11

Change TX PTT to RX PTT, -Z Deploy switches to TX,
update figures and tables accordingly

September 26, 2012

3.12

Update bus and pin assignment drawings

September 27, 2012

3.13

Update bus pin assignment drawings

September 30, 2012

3.14

Update RF block diagram to remove ITAR noticeAMSAT Fox-1
Avionics System Design Specification
1.2. Document Scope
The purpose of this document is to specify the avionics systems and their connections to eachother and to external components for the satellite. It is intended to be used by the hardware,
software, and mechanical designers to develop the architecture and interconnections for thesatellite avionics systems.
1.3. Document Format
This document provides these elements in a numbered format. The numbered sections
specify each major system in the satellite while numbered items for each system specify theexternal connections required and the number of lines for each connection. Satellite bus andexternal connections are further described in figures and tables.
Where System Requirements are reproduced their numbers are from the AMSAT Fox-1
System Requirements Specification.
1.4. References
1. AMSAT Fox-1 ConOps
2. AMSAT Fox-1 System Requirements Specification
3. AMSAT Fox-1 Bus Signal Connections Diagram
4. AMSAT Fox-1 Bus Pin Assignment
5. AMSAT Fox-1 Avionics System Design Specification Spreadsheet
6. AMSAT FOX-ME-112_PCB_ASSY.pdf
7. AMSAT FOX-ME-114_BATTERY_ASSY.pdf

AMSAT Fox-1
Avionics System Design Specification
Contents
1 Introduction ....................................................................................................................... 1
2 Avionics System Bus Signals, Characteristics, and Connections .......................................... 43 RF Transmitter System ....................................................................................................... 7
4 RF Receiver System .......................................................................................................... 13
5 Internal Housekeeping Unit (IHU) System ....................................................................... 17
6 Power Supply System (PSU) ............................................................................................. 22
7 Battery System .................................................................................................................. 34
8 Experiment Payload Systems 1 through 4 ......................................................................... 38
9 System Block Diagrams Reference .................................................................................... 43
10 System Interconnection References ................................................................................. 46

AMSAT Fox-1
Avionics System Design Specification

2 Avionics System Bus Signals, Characteristics, and Connections

Figure 1: Interconnect Diagram

AMSAT Fox-1
Avionics System Design Specification
Table 1: System Bus Signal Characteristics
Pin
Nomenclature
1
SPI1 NSS

Type
DigitalVoltage

Source System
IHU

Load Z

Load System
EXP 1-4

Notes
SPI Standard, IHU Master

2
3

TX PA Current
SPI1 SCK

AnalogDigital0 - 3.0 V

TX
IHU

30 - 60 kΩ

IHU
EXP 1-4

4
5

TX PA Temperature
SPI1 MISO

AnalogDigital100-2000 mVSPI Standard, IHU Master

TX
IHU

30 - 60 kΩ

IHU
EXP 1-4

Analog Devices TMP36FSPI Standard, IHU Master

6
7

TX Osc Temperature
SPI1 MOSI

AnalogDigital100-2000 mV

TX
IHU

30 - 60 kΩ

Note¹

IHU
EXP 1-4

Analog Devices TMP36FSPI Standard, IHU Master

8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23

RX Osc Temperature
Serial RXD*RESERVED*
Serial TXD
IHU Audio 1 Out
Experiment Enable 1
IHU Audio 2 Out
Experiment Enable 2
RX Command Data 8Experiment Enable 3
RX Command Data 9Experiment Enable 4
RX Command Data 10*RESERVED*RX Command Data 11
I²C1 SCL

AnalogDigital100-2000 mV
3.0 V

RX
EXP 1-430 - 60 kΩ

IHU
IHU

Analog Devices TMP36F
TTL, Async, Mark High

DigitalAnalogDigitalAnalogDigitalDigitalDigitalDigitalDigitalDigital

3.0 V
2 V p-p audio

IHU
IHU
IHU
IHU
IHU
RX
IHU
RX
IHU
RX

EXP 1-4
TX
EXP 1-4
TX
EXP 2
IHU
EXP 3
IHU
EXP 4
IHU

TTL, Async, Mark HighFor 5 kHz deviation, 10 Hz - 7 kHz bandwidth
HIGH = Enable EXP 1*RESERVED FOR FUTURE USE*
HIGH = Enable EXP 2

24
25

RX Command Strobe
I²C1 SDA

DigitalDigital

26
27
28
29
30
31
32
33
34
35
36
37

COMMAND Mode
*RESERVED*IHU PTT*RESERVED*RX PTT*RESERVED*RX CD*RESERVED*
RX Audio 1*RESERVED*
RX Audio 2
I²C2 SCL

DigitalIHU

TX

HIGH = Command Mode

DigitalIHU

TX

HIGH = TRANSMIT

DigitalTX

30 - 60 kΩ

IHU

HIGH = HANG TIMER ACTIVE

DigitalRX

30 - 60 kΩ

IHU

38
39

Comp Lim
I²C2 SDA

40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60

RBF 1
+Z Thermistor
RBF 2-Z Thermistor
TX Antenna Deploy+Z CICTX Antenna Sensor-Z CIC
RX Antenna Sensor
Umbilical USBP
RX Antenna Deploy
Umbilical USBM
-Z Deploy Switches
Umbilical Ext 5V Supply
Umbilical Ext 5V Supply
Umbilical Ext 5V Supply
Umbilical Ext 5V Supply
Vbatt
Vbatt
Vbatt
Vbatt

Note¹

Note¹

Note¹

N/A

DigitalDigital

Note¹

RX
IHU

Note¹

RX
IHU

600 Ω, Unbalanced
N/A

HIGH = Enable EXP 3
HIGH = Enable EXP 4TX
I²C Standard, IHU Master30 - 60 kΩ

IHU
I²C Standard, IHU Master

Analog2 V p-p audioRX

600 Ω, Unbalanced

IHU

10 Hz - 7 kHz bandwidth

AnalogDigital

N/A

RX
IHU

N/A

Note¹

IHU
PSU

*RESERVED FOR FUTURE USE*I²C Standard, IHU Master

RX
IHU

100 kΩTX
PSU

I²C Standard, IHU Master

RBF
EXT
RBF
EXT
IHU
EXT
IHU
EXT
IHU
USB
IHU
USB
EXT
USB
USB
USB
USB
BATT/PSU
BATT/PSU
BATT/PSU
BATT/PSU

N/A
N/A
N/A
N/A
TBR
N/A
N.O.
N/A
N.O.

PSU
PSU
PSU
PSU
PSU
PSU
PSU
PSU
PSU
IHU
PSU
IHU
PSU
IHU/PSUIHU/PSUIHU/PSUIHU/PSU
ALL
ALL
ALL
ALL

AnalogDigital

1.4 VDC

AnalogAnalogAnalogAnalogAnalogAnalogDigitalAnalogDigitalDigitalAnalogDigitalAnalog
USB
USB
USB
USB
Power BusPower BusPower BusPower Bus

N/A
N/A
N/A
N/A
TBR
0.1 - 3 VDC
N/A
0.1 - 3 VDC
N/A

Note¹

TBR
N/A
≤ 5.0 VDC
≤ 5.0 VDC
≤ 5.0 VDC
≤ 5.0 VDC
3.3 - 4.2 VDC
3.3 - 4.2 VDC
3.3 - 4.2 VDC
3.3 - 4.2 VDC

Note¹ All SPI and I²C signals are 3.0 V levels

TBR
N/A

N.O. for operation
NCP21XM472J03RA
N.O. for operation
NCP21XM472J03RA
Not designed yet
N.O. when deployed
N.O. when deployed
USB Standard
Not designed yet
USB Standard
TBR - (N.O. = OPERATE?)
Battery Charge Supply, USB Standard
Battery Charge Supply, USB Standard
Battery Charge Supply, USB Standard
Battery Charge Supply, USB Standard

All Digital signals are CMOS logic levels high impedance load unless otherwise noted

AMSAT Fox-1
Avionics System Design Specification

Figure 2: Complete Bus Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification

3 RF Transmitter System
3.1 System Requirements Applicable to RF Transmitter System
2.2.1 The satellite avionics shall be designed for -40C to +70C operating temperature.
2.2.3 The satellite shall be designed to tolerate the radiation environment in orbit.
2.3.1 The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
2.4.1 All RF transmitters shall meet or exceed the requirements specified in the ITURadio Regulations, Technical Characteristics, Volume 3, article 3.
2.4.3 All satellite downlinks shall be in the 2 meter band within the amateur satellite
service.
2.4.4 All satellite transmitter and receiver frequencies shall deviate by no more than 5parts-per-million from the specified values including initial accuracy and temperature
variation.
2.4.5 All satellite frequencies shall be coordinated with the IARU.
3.8.1 The satellite shall include an FM downlink transmitter.
3.8.2 The transmitter shall have specifications as shown in Table 2.
Power Output
400 mW (min.)FM Deviation
5 kHz
Audio Bandwidth 3 kHz
3.8.3 The transmitter shall provide a means to prevent over modulation.
3.9.1 The satellite shall provide an FM transponder via the RF uplink and RF downlink.
3.9.2 The transponder shall detect the presence of a 67 Hz CTCSS tone on the uplink.
3.9.3 The downlink transmitter shall be keyed (i.e. PTT-on) for 2 minutes following
detection of the 67 Hz CTCSS tone.
3.9.4 The downlink transmitter shall stay on continuously as long as the 67 Hz CTCSS
tone is detected at least once every 2 minutes on the uplink.
3.9.5 The 67 Hz CTCSS tone is not required for a received signal to be repeated on thedownlink, once the transmitter has been keyed.
3.9.6 If the downlink transmitter has been un-keyed for a period of 5 minutes, thesatellite shall send " HI THIS IS AMSAT FOX " in Morse code via a keyed audio toneon the downlink transmitter.
3.9.7 The satellite shall default to Transponder Mode in the event of an IHU processor
failure.
3.10.1 The satellite shall collect telemetry data.

AMSAT Fox-1
Avionics System Design Specification
3.10.2 The telemetry data shall include measured parameters as shown in Table 3.
Parameter Name Description
CELL V
Voltages of battery cells
PANEL V
Voltages of solar panels
TOTAL I
Total DC current out of power system
PA I
DC current into RF power amp
BATTERY T
Temperature of battery
PANEL T
Temperatures of solar panels
PA T
Temperature of RF power amp
OSC T
Temperature of RF oscillators
3.10.3 The measured parameters shall be sampled at least every 15 seconds.
3.11.1 The satellite shall send telemetry using FSK on the RF downlink.
3.11.2 The FSK shall use the frequency spectrum below the audible range.
3.11.3 The telemetry shall be transmitted simultaneously with any transponder
communications.
3.12.1 The satellite shall provide the means to process commands sent via the RF uplinkfrom a ground control station.
3.12.2 The commands received via the RF uplink shall not be repeated on the RF
downlink.
3.12.3 The following commands shall be provided, as shown in Table 5.
CommandOperation
TEST
Send test message
INHIBIT
Inhibit RF transmission
IHU OFFPower off IHUIHU ONPower on IHU
CLEAR
Clear stored telemetry
TRANSPONDER MODE
Enter Transponder Mode
COMMAND MODE
Enter Command Mode
3.12.4 A TEST command shall cause the satellite to respond by sending " TEST TESTTEST " in Morse code via a keyed audio tone on the RF downlink.
3.12.5 An INHIBIT command shall cause the satellite to cease RF transmissions.
3.12.6 Any command other than INHIBIT shall remove a transmit inhibit condition.
3.12.10 A TRANSPONDER MODE command shall cause the satellite to enter theTransponder Mode.
3.12.11 A COMMAND MODE command shall cause the satellite to enter the CommandMode.
3.13.1 The satellite shall provide on-orbit operating modes as shown in Table 6.
Name
Description
Startup Mode
Wait 45 minutes and deploy antennas
Transponder Mode
FM transponder and telemetry active
Command Mode
Telemetry active, no FM transponder
3.13.5 If the antennas have been deployed, the satellite shall enter the TransponderMode.
3.13.8 In Transponder Mode, the transponder and the telemetry shall be active.

AMSAT Fox-1
Avionics System Design Specification
3.13.9 In Command Mode, the telemetry shall be active and the transponder shall not be
active. (i.e. signals that appear on the uplink shall not be repeated on the downlink.)
3.2 Volume Requirements Applicable to RF Transmitter System
3.2.1 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 5 mmfrom the –Z surface of the PC board.
3.2.2 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 6.0 mm
from the +Z surface of the PC board.
3.3 Interface Control Documents Applicable to RF Transmitter System
AMSAT Fox-1 IHU to RF System Interface Control Document

AMSAT Fox-1
Avionics System Design Specification
3.4 RF Transmitter System PCB Bus Connections

Figure 3: RF Transmitter System Bus Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification
3.5 RF Transmitter System PCB External Connections
3.5.1 2 meter band RF output, coaxial cable to Transmit Antenna
3.5.2 Spacecraft deployment switches cable(s) TBR
3.5.3 Three connections via Samtec FSI-105-06-L-S-AD connector
3.5.3.1 1 contact -Z Solar Panel Thermistor
3.5.3.2 1 contact -Z Solar Panel CIC +3.5.3.3 1 contact common or - for above four connections
Table 2: External Connection Signal Characteristics

External
Connection

Nomenclature
2 meter Antenna ≈ 145.9
Coaxial Cable
MHz
Spacecraft Deployment
Cable TBR
SwitchesType
RF

Voltage/Power Source System
Load Z
0 to +30
2 meter
50 Ω unbal.
dBm
Antenna

AnalogN/A

SwitchN/A

Bus Pin
N/A
52

Table 3: -Z PCB face FSI-105-06-L-S-AD connector mates to pads on –Z Solar Panel
Pin

Nomenclature

1
2-Z Thermistor-Z Deploy Switches

3
4-Z Solar Panel Common
N/C

5-Z CIC (+)

Type

Voltage

Source System

Load Z

Load System

Bus Pin

AnalogAnalog

N/A
N/A

N/A
N/A

N/A
N/A

PSU
PSU

43
52
GroundPlane

Analog2.66 VDC
nominal

N/A

N/A

PSU

47

AMSAT Fox-1
Avionics System Design Specification

Figure 4: RF Transmitter System FSI-105-06-L-S-AD Connection Pin
Assignments

AMSAT Fox-1
Avionics System Design Specification

4 RF Receiver System
4.1 System Requirements Applicable to RF Receiver System
2.2.1 The satellite avionics shall be designed for -40C to +70C operating temperature.
2.2.3 The satellite shall be designed to tolerate the radiation environment in orbit.
2.3.1 The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
2.4.2 All satellite uplinks shall be in the 70 cm band of the amateur satellite service.
2.4.5 All satellite frequencies shall be coordinated with the IARU.
3.7.1 The satellite shall include an FM uplink receiver.
3.7.2 The receiver shall have specifications as shown in Table 1.
Sensitivity-120 dBm for 12 dB SINAD (min.)FM Deviation
5 kHz
Audio Bandwidth
3 kHz
Input Frequency Acceptance Receiver shall accept signals that are off
frequency by ±2.5 kHz (min.)3.8.3 The transmitter shall provide a means to prevent over modulation.
3.9.1 The satellite shall provide an FM transponder via the RF uplink and RF downlink.
3.9.2 The transponder shall detect the presence of a 67 Hz CTCSS tone on the uplink.
3.9.4 The downlink transmitter shall stay on continuously as long as the 67 Hz CTCSS
tone is detected at least once every 2 minutes on the uplink.
3.9.5 The 67 Hz CTCSS tone is not required for a received signal to be repeated on thedownlink, once the transmitter has been keyed.
3.9.7 The satellite shall default to Transponder Mode in the event of an IHU processor
failure.
3.10.1 The satellite shall collect telemetry data.
3.10.2 The telemetry data shall include measured parameters as shown in Table 3.
Parameter Name Description
CELL V
Voltages of battery cells
PANEL V
Voltages of solar panels
TOTAL I
Total DC current out of power system
PA I
DC current into RF power amp
BATTERY T
Temperature of battery
PANEL T
Temperatures of solar panels
PA T
Temperature of RF power amp
OSC T
Temperature of RF oscillators
3.10.3 The measured parameters shall be sampled at least every 15 seconds.
3.12.1 The satellite shall provide the means to process commands sent via the RF uplinkfrom a ground control station.
3.12.2 The commands received via the RF uplink shall not be repeated on the RF
downlink.

AMSAT Fox-1
Avionics System Design Specification
3.12.3 The following commands shall be provided, as shown in Table 5.
CommandOperation
TEST
Send test message
INHIBIT
Inhibit RF transmission
IHU OFFPower off IHUIHU ONPower on IHU
CLEAR
Clear stored telemetry
TRANSPONDER MODE
Enter Transponder Mode
COMMAND MODE
Enter Command Mode
3.12.10 A TRANSPONDER MODE command shall cause the satellite to enter theTransponder Mode.
3.12.11 A COMMAND MODE command shall cause the satellite to enter the CommandMode.
3.13.1 The satellite shall provide on-orbit operating modes as shown in Table 6.
3.13.5 If the antennas have been deployed, the satellite shall enter the TransponderMode.
3.13.8 In Transponder Mode, the transponder and the telemetry shall be active.
3.13.9 In Command Mode, the telemetry shall be active and the transponder shall not be
active. (i.e. signals that appear on the uplink shall not be repeated on the downlink.)
3.13.11 The RF uplink shall be monitored for commands in all modes.
4.2 Volume Requirements Applicable to RF Receiver System
4.2.1 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 1 mmfrom the –Z surface of the PC board.
4.2.2 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 6.0 mm
from the +Z surface of the PC board.
4.3 Interface Control Documents Applicable to RF Receiver System
AMSAT Fox-1 IHU to RF System Interface Control Document

AMSAT Fox-1
Avionics System Design Specification
4.4 RF Receiver System PCB Bus Connections

Figure 5: RF Receiver System Bus Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification
4.5 RF Receiver System PCB External Connections
4.5.1 70cm band RF input, coaxial cable to Receive Antenna
Table 4: RF Receiver System External Connection Signal Characteristics

External
Connection

Nomenclature

Type

Coaxial Cable

70 cm RF Input 437 MHz

RF

Voltage/P
ower
Source System
Load Z-60 dBmto -140 70 cm Antenna 50 Ω unbal.
dBm

Bus Pin
N/AAMSAT Fox-1
Avionics System Design Specification

5 Internal Housekeeping Unit (IHU) System
5.1 System Requirements Applicable to Internal Housekeeping Unit (IHU) System
2.2.1 The satellite avionics shall be designed for -40C to +70C operating temperature.
2.2.3 The satellite shall be designed to tolerate the radiation environment in orbit.
2.3.1 The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
3.3.2 The satellite shall include an umbilical port as per the CubeSat Design
Specification.
3.4.3 The satellite shall provide the means to run diagnostic tests via the umbilical port
while integrated with the P-POD.
3.6.2 The satellite shall provide a means to activate and deactivate the experiment
payload.
3.6.3 The satellite shall provide a means to telemeter data from the experiment
payload.
3.9.6 If the downlink transmitter has been un-keyed for a period of 5 minutes, thesatellite shall send " HI THIS IS AMSAT FOX " in Morse code via a keyed audio toneon the downlink transmitter.
3.9.7 The satellite shall default to Transponder Mode in the event of an IHU processor
failure.
3.10.1 The satellite shall collect telemetry data.
3.10.2 The telemetry data shall include measured parameters as shown in Table 3.
Parameter Name Description
CELL V
Voltages of battery cells
PANEL V
Voltages of solar panels
TOTAL I
Total DC current out of power system
PA I
DC current into RF power amp
BATTERY T
Temperature of battery
PANEL T
Temperatures of solar panels
PA T
Temperature of RF power amp
OSC T
Temperature of RF oscillators
3.10.3 The measured parameters shall be sampled at least every 15 seconds.
3.10.4 The minimum and maximum values of each of the measured parameters shall besaved in non-volatile memory.
3.10.5 The telemetry data shall also include calculated parameters as shown in Table 4.
Parameter Name Description
UP TIME
Total seconds since avionics power-up or reset
SPIN
Satellite spin rate and direction
3.10.6 A telemetry frame shall include the current measured values, the saved minimum
and maximum values, and the current calculated values.
3.11.1 The satellite shall send telemetry using FSK on the RF downlink.
3.11.2 The FSK shall use the frequency spectrum below the audible range.
3.11.3 The telemetry shall be transmitted simultaneously with any transponder
communications.
3.11.4 The telemetry transmission shall include telemetry frames.

AMSAT Fox-1
Avionics System Design Specification
3.11.5 The telemetry transmission shall include experiment data.
3.12.1 The satellite shall provide the means to process commands sent via the RF uplinkfrom a ground control station.
3.12.3 The following commands shall be provided, as shown in Table 5.
CommandOperation
TEST
Send test message
INHIBIT
Inhibit RF transmission
IHU OFFPower off IHUIHU ONPower on IHU
CLEAR
Clear stored telemetry
TRANSPONDER MODE
Enter Transponder Mode
COMMAND MODE
Enter Command Mode
3.12.4 A TEST command shall cause the satellite to respond by sending " TEST TESTTEST " in Morse code via a keyed audio tone on the RF downlink.
3.12.7 An IHU OFF command shall cause the IHU System to power off.
3.12.8 An IHU ON command shall cause the IHU System to power on.
3.12.9 A CLEAR command shall cause the satellite to clear the saved minimum andmaximum telemetry parameter values.
3.12.10 A TRANSPONDER MODE command shall cause the satellite to enter theTransponder Mode.
3.13.1 The satellite shall provide on-orbit operating modes as shown in Table 6.
Name
Description
Startup Mode
Wait 45 minutes and deploy antennas
Transponder Mode
FM transponder and telemetry active
Command Mode
Telemetry active, no FM transponderAMSAT Fox-1
Avionics System Design Specification
3.13.2 The satellite shall transition between modes as shown in Figure 1.

3.12.11 A COMMAND MODE command shall cause the satellite to enter the CommandMode.
3.13.3 Upon power-up of the avionics, the satellite shall begin operation from the"Power-up" state as shown in Figure 1.
3.13.4 An IHU ON Command shall cause the satellite to begin operation from the"Power-up " state as shown in Figure 1.
3.13.5 If the antennas have been deployed, the satellite shall enter the TransponderMode.
3.13.6 If the antennas have not been deployed, the satellite shall enter the Startup Mode.
3.13.7 In Startup Mode, the satellite shall wait 45 minutes, deploy the antennas and thenenter Transponder Mode.
3.13.8 In Transponder Mode, the transponder and the telemetry shall be active.
3.13.9 In Command Mode, the telemetry shall be active and the transponder shall not be
active. (i.e. signals that appear on the uplink shall not be repeated on the downlink.)
3.13.10 If another Command Mode command is not received, the satellite shall
automatically enter Transponder Mode 24 hours after having entered Command Mode.
3.13.11 The RF uplink shall be monitored for commands in all modes.

AMSAT Fox-1
Avionics System Design Specification
5.2 Volume Requirements Applicable to IHU System
5.2.1 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 1 mmfrom the –Z surface of the PC board.
5.2.2 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 6.0 mm
from the +Z surface of the PC board.
5.3 Interface Control Documents Applicable to IHU System
AMSAT Fox-1 IHU to RF System Interface Control Document
AMSAT Fox-1 IHU to PSU Interface Control Document
AMSAT Fox-1 IHU to Attitude Determination Experiment Interface Control Document

AMSAT Fox-1
Avionics System Design Specification
5.4 Internal Housekeeping Unit (IHU) System PCB Bus Connections

Figure 6: IHU System Bus Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification

6 Power Supply System (PSU)
6.1 System Requirements Applicable to Power Supply System (PSU)
2.2.1 The satellite avionics shall be designed for -40C to +70C operating temperature.
2.2.3 The satellite shall be designed to tolerate the radiation environment in orbit.
2.3.1 The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
3.3.1 The satellite shall include a "Remove Before Flight" pin as per the CubeSat Design
Specification.
3.4.1 The satellite battery and photovoltaic panels shall be electronically disconnected fromthe avionics when the "Remove Before Flight" pin is inserted, regardless of the state of the
deployment switch(es).
3.4.2 The satellite shall provide the means to charge the battery via the umbilical port while
integrated with the P-POD.
3.5.1 The satellite shall produce electrical power from sunlight.
3.5.2 The satellite shall produce electrical power while in sunlight regardless of orientation
and while tumbling or spinning.
3.5.3 The satellite shall produce sufficient average electrical power to operate continuously inthe orbit of maximum eclipse.
3.5.4 The satellite shall provide sufficient battery capacity to operate continuously in the orbitof maximum eclipse.
3.5.5 If the battery fails, including a short-circuit condition, the satellite shall continue tooperate using only the photovoltaic panel power when in sunlight.
3.6.1 The satellite shall provide current limited DC power for an experiment payload.
3.10.1 The satellite shall collect telemetry data.
3.10.2 The telemetry data shall include measured parameters as shown in Table 3.

Parameter NameCELL VPANEL VTOTAL IPA I
BATTERY T
PANEL T
PA T
OSC T

Description
Voltages of battery cells
Voltages of solar panels
Total DC current out of power system
DC current into RF power amp
Temperature of battery
Temperatures of solar panels
Temperature of RF power amp
Temperature of RF oscillators

3.10.3 The measured parameters shall be sampled at least every 15 seconds.
3.10.5 The telemetry data shall also include calculated parameters as shown in Table 4.

Parameter Name Description
UP TIME
Total seconds since avionics power-up or reset
SPIN
Satellite spin rate and direction
6.2 Volume Requirements Applicable to PSU System
6.2.1 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 1 mmfrom the –Z surface of the PC board.

AMSAT Fox-1
Avionics System Design Specification
6.2.2 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 3.0 mm
from the +Z surface of the PC board within the area 0 to 4.0 mm from the +Y and +Xedges of the board, and 6.0 mm from the +Z surface of the PC board in the rest of theboard area.
6.3 Interface Control Documents Applicable to PSU System
AMSAT Fox-1 IHU to PSU Interface Control Document

AMSAT Fox-1
Avionics System Design Specification
6.4 Power Supply System (PSU) PCB Bus Connections

Figure 7: PSU Bus Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification
6.5 Power Supply System (PSU) PCB External Connections
6.5.1 Three connections to +X Solar Panel using Samtec MEC1-105-02-L-D-NP-A
connector
6.5.1.1 1 contact +X Solar Panel Thermistor
6.5.1.2 1 contact +X Solar Panel CIC +6.5.1.3 1 contact common or - for above two connections
6.5.2 Three connections to -X Solar Panel using Samtec MEC1-105-02-L-D-NP-A
connector
6.5.2.1 1 contact -X Solar Panel Thermistor
6.5.2.2 1 contact -X Solar Panel CIC +6.5.2.3 1 contact common or - for above two connections
6.5.3 Five connections to +Y Solar Panel using Samtec MEC1-105-02-L-D-NP-A
connector
6.5.3.1 1 contact +Y Solar Panel Thermistor
6.5.3.2 1 contact +Y Solar Panel CIC +6.5.3.3 1 contact TX Antenna Deploy
6.5.3.4 1 contact TX Antenna Sensor
6.5.3.5 1 contact common or - for above connections
6.5.4 Five connections to -Y Solar Panel using Samtec MEC1-105-02-L-D-NP-A
connector
6.5.4.1 1 contact -Y Solar Panel Thermistor
6.5.4.2 1 contact -Y Solar Panel CIC +6.5.4.3 1 contact RX Antenna Deploy
6.5.4.4 1 contact RX Antenna Sensor
6.5.4.5 1 contact common or - for above connections
6.5.5 All PCB edges that connect to solar panel MEC1-105-02-L-D-NP-A connectors
shall have contact pads on the PCB for all connector pins, whether connected to a
trace or not.

AMSAT Fox-1
Avionics System Design Specification
Table 5: +X PCB edge mates to MEC1-105-02-L-D-NP-A connector on +X Solar Panel

Pin

Nomenclature

1
2
3
4
5

N/C
+X Solar Panel Thermistor
N/C
N/C
N/C

6

+X Solar Panel Common
N/C
N/C
N/C

7
8
9

10 +X Solar Panel CIC (+)

Type

Voltage

Source System

Load ZBus Pin

Analog

N/A

N/A

N/A

N/A

GroundPlane

Digital2.66 VDC
nominal

N/A

N/A

N/A

AMSAT Fox-1
Avionics System Design Specification

Figure 8: PSU System +X Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification
Table 6: -X PCB edge mates to MEC1-105-02-L-D-NP-A connector on -X Solar Panel

Pin

Nomenclature

1
2
3
4
5

N/C
-X Solar Panel Thermistor
N/C
N/C
N/C

6

-X Solar Panel Common
N/C
N/C
N/C

7
8
9

10 -X Solar Panel CIC (+)

Type

Voltage

Source System

Load ZBus Pin

Analog

N/A

N/A

N/A

N/A

GroundPlane

Digital2.66 VDC
nominal

N/A

N/A

N/A

AMSAT Fox-1
Avionics System Design Specification

Figure 9: PSU System -X Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification
Table 7: +Y PCB edge mates to MEC1-105-02-L-D-NP-A connector on +Y Solar Panel
Pin

Nomenclature

1
2
3
4
5

N/C
+Y Solar Panel Thermistor
N/C
TX Antenna Sensor
N/C

6+Y Solar Panel Common
N/C
TX Antenna Deploy
N/C

7
8
9

10 +Y Solar Panel CIC (+)

Type

Voltage

Source System

Load ZBus Pin

Analog

N/A

N/A

N/A

N/A

Analog

N/A

IHU

N.O.

46
GroundPlane

Analog

TBR

TBR

TBR

TBR

Digital2.66 VDC
nominal

N/A

N/A

N/A

AMSAT Fox-1
Avionics System Design Specification

Figure 10: PSU System +Y Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification
Table 8: -Y PCB edge mates to MEC1-105-02-L-D-NP-A connector on -Y Solar Panel

Pin

Nomenclature

1
2
3
4
5

N/C
-Y Solar Panel Thermistor
N/C
RX Antenna Sensor
N/C

6-Y Solar Panel Common
N/C
RX Antenna Deploy
N/C

7
8
9

10 -Y Solar Panel CIC (+)

Type

Voltage

Source System

Load ZBus Pin

Analog

N/A

N/A

N/A

N/A

Analog

N/A

IHU

N.O.

48
GroundPlane

Analog

TBR

TBR

TBR

TBR

Digital2.66 VDC
nominal

N/A

N/A

N/A

AMSAT Fox-1
Avionics System Design Specification

Figure 11: PSU System -Y Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification

7 Battery System
7.1 Volume Requirements Applicable to Battery PCB 1 System
7.1.1 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 4.0 mm
from the -Z surface of the PC board within the area 0 to 4.0 mm from the +Y and +Xedges of the board, and 1.0 mm from the -Z surface of the PC board in the rest of theboard area.
7.1.2 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 17.0 mm
from the +Z surface of the PC board.

AMSAT Fox-1
Avionics System Design Specification
7.2 Battery PCB 1 System Bus Connections

Figure 12: Battery 1 System Bus Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification
7.3 Battery PCB 1 System External Connections
7.3.1 Umbilical as USB mini type B receptacle
7.3.2 Remove Before Flight as 3.5mm normally open TS jack
Table 9: Battery 1 External Connection Signal Characteristics
External
Connection

Nomenclature

Type

USB 1

+5 VDC*

AnalogUSB 2

USB Data - (USBM)

DigitalUSB 3

USB Data + (USBP)

DigitalUSB 4Ground

RBF 1

RBF 1

Analog

RBF 2

RBF 2

AnalogVoltage/P
ower
Source System
USB
5 VDC
CONNECTOR
3.0 V
USB
CMOS
CONNECTOR
logic
3.0 V
USB
CMOS
CONNECTOR
logic
USB
CONNECTOR
3.5mm N.O. TS
N/Ajack
3.5mm N.O. TS
N/A
jack

*When external supply is connected to USB port

Load ZN/A

Bus Pin53, 54, 55,
56

N/A

51

N/A

49

N/A

Ground
Plane

N/A

40

N/A

42

AMSAT Fox-1
Avionics System Design Specification
7.4 Battery PCB 2 System Bus Connections

Figure 13: Battery 2 Bus Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification

8 Experiment Payload Systems 1 through 4
8.1 System Requirements Applicable to Experiment Payload Systems 1-4
2.1.4 The satellite shall provide mass for an experiment payload up to 100 g.
2.1.5 The satellite shall provide volume for an experiment payload up to 95 x 95 x 15.7mm.
2.2.1 The satellite avionics shall be designed for -40C to +70C operating temperature.
2.2.3 The satellite shall be designed to tolerate the radiation environment in orbit.
2.3.1 The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
3.6.2 The satellite shall provide a means to activate and deactivate the experiment
payload.
3.6.3 The satellite shall provide a means to telemeter data from the experiment
payload.
8.2 Volume Requirements Applicable to Experiment Payload System 1
8.2.1 No components, connections other than those connectors stipulated in section
10, and structures such as shielding or enclosures shall protrude from the –Z surfaceof the PC board.
8.2.2 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 6.0 mm
from the +Z surface of the PC board.
8.3 Volume Requirements Applicable to Experiment Payload Systems 2 and 3
8.3.1 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 1 mmfrom the –Z surface of the PC board.
8.3.2 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 6.0 mm
from the +Z surface of the PC board.
8.4 Volume Requirements Applicable to Experiment System 4
8.4.1 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 1 mmfrom the –Z surface of the PC board.
8.4.2 Components, connections other than those connectors stipulated in section 10,
and structures such as shielding or enclosures shall not protrude more than 5.0 mm
from the +Z surface of the PC board.

AMSAT Fox-1
Avionics System Design Specification
8.5 Experiment Payload 1-3 Systems PCB Bus Connections

Figure 14: Experiment Payload 1-3 Systems Bus Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification
8.6 Experiment Payload 4 System PCB Bus Connections

Figure 15: Experiment Payload 4 System Bus Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification
8.7 Experiment Payload 4 System PCB External Connections
8.7.1 Three connections using Samtec FSI-105-06-L-S-AD connector
8.7.1.1 1 contact +Z Solar Panel Thermistor
8.7.1.2 1 contact +Z Solar Panel CIC +8.7.1.3 1 contact common or - for above two connections
Table 10: +Z PCB face FSI-105-06-L-S-AD connector mates to pads on +Z Solar Panel
Pin
1
2
3
4
5

Nomenclature+Z Thermistor
N/C+Z Solar Panel Common
N/C+Z CIC (+)

Type

Voltage

Source System

Load Z

Load System

Bus Pin

Analog

N/A

N/A

N/A

PSU

41
GroundPlane

Analog2.66 VDC
nominal

N/A

N/A

PSU

45

AMSAT Fox-1
Avionics System Design Specification

Figure 16: Experiment Payload 4 System FSI-105-06-L-S-AD
Connection Pin Assignments

AMSAT Fox-1
Avionics System Design Specification

9 System Block Diagrams Reference
9.1 IHU System

DEFUNCT –PENDING UPDATEAMSAT Fox-1
Avionics System Design Specification
9.2 RF System

AMSAT Fox-1
Avionics System Design Specification
9.3 PSU System (TBR)AMSAT Fox-1
Avionics System Design Specification

10 System Interconnection References
10.1 Bus Connectors
10.1.1 Samtec QTH-030-02-L-D-A and QSH-030-01-L-D-A connectors
10.1.2 QTH connector shall be mounted on the +Z surface of each circuit board
except the Receive Antenna PCB / GPS Payload circuit board
10.1.3 QSH connector shall be mounted on the –Z surface of each circuit board
10.2 Bus Connector Documentation
10.2.1 Samtec QSH
10.2.2 Samtec QTH
10.2.3 Samtec QxH High Speed Characterization Report
10.2.4 Samtec QxH Single Ended Channel Properties
10.3 External Connectors
10.3.1 Samtec MEC1-105-02-L-D-NP-A connector mounted on +X, -X, +Y, -Y Solar
Panels
10.3.2 Samtec FSI-105-06-L-S-AD connector mounted on -Z face of RF Transmitter
System PCB and +Z face of Experiment Payload 4 System PCB
10.4 External Connector Documentation
10.4.1 Samtec MEC1
10.4.2 Samtec MEC1 Qualification Testing
10.4.3 Samtec FSI
10.5 PCB Connector Layout Documentation
10.5.1 FOX-ME-113_PCB.pdf

AMSAT Fox-1
Avionics System Design Specification
10.6 Systems PCB Connector Layout
10.6.1 Common to All Systems

AMSAT Fox-1
Avionics System Design Specification
10.6.2 RF Transmitter System

10.6.3 PSU System

AMSAT Fox-1
Avionics System Design Specification
10.6.4 Experiment 4 System

AMSAT Fox-1
Attitude Determination Experiment Payload System Requirements
Date: June 29, 2012
Version: 2.0

AMSAT Fox-1
Attitude Determination Experiment Payload System
Requirements Specification
1 Introduction
This document specifies the system level technical requirements for the AMSAT Fox-1
satellite project attitude determination experiment payload.
The Fox-1 satellite is a 1 Unit CubeSat with a primary mission of providing amateur
radio communications. In addition to its mission as a communications satellite, Fox-1
will host an experiment payload. The satellite will reserve mass and volume for theexperiment and will provide DC power and a communications facility. The experiment is
expected to be provided by students at Penn State University – Erie, through an AMSAT
sponsored senior design project.
The goal of the experiment will be to measure the spin rate and direction, about the Z axisof the satellite, and any off Z-axis “wobble”.
1.1

Document History
DATE

VERSION

SUMMARY

November 9, 2011

1.0

From Draft F

December 4, 2011

1.01

Fix formatting

December 23, 2011

1.03

Update references to other documents

December 27, 2011

1.04

Update 2.1.13 for QTH/QSH connectors

February 12, 2011

1.10

Change bus to SPI and add power signal
Removed references to multiple PCBs
and conflicting component placement
Adjust PCB stay out zone and otherrequirements per latest mechanicalrevisions

June 29, 2012

2.0

Modified extensively due to move ofexperiment equipment to the IHU card

1.2 Document Scope
The purpose of this document is to specify the technical requirements of the experiment
payload at the system (i.e. "black box") level. It is intended to be used to by the hardware,

AMSAT Fox-1
Attitude Determination Experiment Payload System Requirements
software and mechanical designers to develop the architecture/high-level design
specifications. It is also intended to be used for test planning and development.
1.3 Document Format
This document provides the requirements in numbered format. Each requirement is
assigned a unique number. Additional information such as comments or examples thatare provided for guidance or clarity are italicized to distinguish them from requirements.
1.4 References
1. AMSAT Fox-1, Concept of Operations, Version 1.03, September 19, 2011
2. AMSAT Fox-1, System Requirements Specification, Version 1.1, April 29, 2012
3. AMSAT Fox-1 IHU to Attitude Determination Experiment Interface Control
Document, Version 2.0, June 29, 2012

AMSAT Fox-1
Attitude Determination Experiment Payload System Requirements

2 General Requirements
2.1

Physical Requirements

2.1.1 The experiment payload shall be constructed on the satellite IHU system
PCB.
2.2

Environmental Requirements

2.2.1 The experiment payload shall be designed for -40C to +70C operating
temperature.

3 Functional Requirements
3.1

Experiment Data

3.1.1 The experiment payload shall measure the spin rate and direction about
the Z axis of the satellite.
3.1.2 The experiment payload shall measure any deviation (wobble) of the Z
axis of the satellite caused by the spin of the satellite.
3.1.3 The experiment payload data shall have an accuracy of 1 degree.
3.1.4 The experiment payload shall be able to resolve the rate of spin in therange of 0 to 50 degrees per second. The experiment payload shall beable to resolve the deviation of the Z axis (wobble) in the range of 0 to
50 degrees.
3.2

Satellite Interface

3.2.1 The experiment data shall be directly collected by the satellite IHU
system.
3.3

Power

3.3.1 The experiment payload shall receive electrical power from the satellite
battery and photovoltaic panels.
3.3.2 The electrical power voltage will be nominally DC 3.6 V.
3.3.3 The satellite IHU system will activate and deactivate the experiment
payload as necessary.
3.3.4 The electrical power drawn by the experiment payload shall not exceed
200 mW.

AMSAT Fox-1
Attitude Determination Experiment Payload System Requirements
3.4

Experiment Data

3.4.1 The IHU system shall process the experiment data for telemetrytransmission†.
3.4.2 The IHU system shall sample the experiment data at a rate sufficient toprovide telemetry data at least every 15 seconds.
3.4.3 The experiment payload data shall include the following measured andcalculated parameters:

Parameter Name

Description

SPIN RATE

Rate of spin of the satellite about the Z axis, in degrees per minute

SPIN DIRECTION Direction of spin of the satellite about the Z axis (+X or –X)
DEVIATION

Deviation (wobble) of +Z axis caused by satellite spin

UP TIME

Total seconds since experiment payload power-up or reset†Note that the telemetry data frame is specified in the AMSAT Fox-1 IHU to Attitude
Determination Experiment Interface Control Document.

4 External Interface Documents
To fully specify the experiment payload technical requirements, the following
documents must also be provided;
1. AMSAT Fox-1 IHU to Attitude Determination Experiment Interface Control
Document

5 Summary
The Fox-1 satellite attitude determination experiment payload will provide data on
the spin and wobble of the passive-magnetically stabilized satellite. This
includes the first known measurements of the wobble about the Z axis of amagnetically stabilized AMSAT satellite.

AMSAT Fox-1
IHU to RF ICD
Date: September 18, 2012
Version: Version 1.91

AMSAT Fox-1
IHU to RF System Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the RF System, as required per the AMSAT Fox-1 System Requirements
Specification document.
1.1 Document History
DATE

VERSION

March 24, 2012

1.0

SUMMARY
Initial versionndMarch 24, 2012

1.1

Add 2 RX Audio Out section 3.4.1

March 26, 2012

1.2

Section 3.2 rename Zombie to IHU Control,
rename Audio to Audio 1, Section 3.4 remove
RX Audio 2, section 4 removed entirely

March 26, 2012

1.3

Many updates using input from teams

March 30, 2012

1.4

Update 3.4.1.1 to clarify that receive signal
CTCSS is responsible for state

March 31, 2012

1.5

3.3.1.3 updated to read no less than 100 mS

April 24, 2012

1.6

Update impedances and voltages to match SDS

June 18, 2012

1.7

Update 3.3.1.5 per PDR change to SRS, remove
RESET add IHU OFF and IHU ON commands,
signal characteristic updates per PDR, 3.4.1.2 toindicate command station signal strength

September 13, 2012

1.8

Remove IHU CONTROL signal, match signal
characteristics to system design specification

September 16, 2012

1.9

Changes to 3.3.1.1 and Table 4 per Tony

September 18, 2012

1.91

Removed Command Table (section 3.3) and restated section 3.3 requirements accordingly

AMSAT Fox-1
IHU to RF ICD
1.2 Document Scope
The purpose of this document is to specify the signal types, levels, and direction forconnections between the IHU and the RF System as described in the AMSAT Fox-1
System Requirements Specification.
1.3 References
1. AMSAT Fox-1 System Requirements Specification
2. AMSAT Fox-1 System Design Specification
3. AMSAT Fox-1 IHU Software Architecture SpecificationAMSAT Fox-1
IHU to RF ICD

2 General Requirements
2.1 Telemetry
2.1.1 RF System Telemetry values shall be conveyed as analog voltage
levels sent from the RF System to the IHU System.
2.1.2 The IHU System shall convert the analog signals to digital
representations.
2.1.3 Audio signals for the purpose of conveying telemetry via sub-audible
audio frequencies shall be sent from the IHU System to the RF
System.
2.2 RF System Control
2.2.1 Control of the RF System shall be accomplished by means of digital
signals sent from the IHU System to the RF System.
2.3 Satellite System Command
2.3.1 Command data for the purpose of controlling the satellite shall beprocessed by the RF System and sent to the IHU System.
2.3.2 Command data shall be conveyed to the IHU via digital signals.
2.4 Operational Components
2.4.1 Demodulated baseband audio signals shall be passed from the RF
System to the IHU System for processing.
2.4.2 Baseband audio signals shall be passed from the IHU System to the
RF System for transmission.
2.4.3 Operational Status signals shall be conveyed as digital signals sentfrom the RF System to the IHU System.
2.5 Signal Transmission
2.5.1 Signals shall use the pin assignments shown in the Fox-1 System
Design Specification document.
2.5.2 Signal connections shall comply with the impedance and signal typeshown in the parameters for each type of signaling.
2.6 Signal Type Definitions and Levels
2.6.1 Analog: 0.1 – 3.5 VDC analog voltage.
2.6.2 Digital: 3.0 VDC logic levels.
2.6.2.1 Digital signals High State shall be ≥ 2.4 V.

AMSAT Fox-1
IHU to RF ICD
2.6.2.2 Digital signals Low State shall be ≤ 0.4 V.

AMSAT Fox-1
IHU to RF ICD

3 Signal Connection Requirements
3.1 Telemetry
3.1.1 The RF System shall provide raw telemetry values from the RF
System components as shown in Table 1.
Table 1
Pin
Nomenclature
2 TX PA Current
4 TX PA Temperature
6 TX Osc Temperature
8 RX Osc Temperature

Type
AnalogAnalogAnalogAnalogVoltage
Source System
0 - 3.0 V
TX
100-2000 mV
TX
100-2000 mV
TX
100-2000 mV
RX

Load Z
30 - 60 kΩ
30 - 60 kΩ
30 - 60 kΩ
30 - 60 kΩ

Load System
IHU
IHU
IHU
IHU

Notes
Analog Devices TMP36F
Analog Devices TMP36F
Analog Devices TMP36F

3.1.1.1 The values shall be updated at a rate to provide new samples
at least every 15 seconds.
3.2 RF System Control
3.2.1 The IHU System shall provide control and audio signals to the RF
System as shown in Table 2.
Table 2Pin
Nomenclature
12 IHU Audio 1 Out
26 COMMAND Mode
28 IHU PTT

Type
AnalogDigitalDigitalVoltage
Source System
Load Z
Load System
2 V p-p audio
IHU
600 Ω, Unbalanced
TX
IHU
TX
IHU
TX

Notes
For 5 kHz deviation, 10 Hz - 7 kHz bandwidth
HIGH = Command Mode
HIGH = TRANSMIT

3.2.1.1 COMMAND Mode signal when High shall inhibit received RF
audio retransmission (COMMAND MODE).
3.2.1.2 IHU PTT signal when High shall key the RF transmitter on.
3.3 Satellite System Command
3.3.1 The RF System shall provide ground station command signals to the
IHU System as shown in Table 3.
Table 3
Pin
Nomenclature
16 RX Command Data 818 RX Command Data 920 RX Command Data 10
22 RX Command Data 11
24 RX Command Strobe

Type
DigitalDigitalDigitalDigitalDigitalVoltage

Source System
RX
RX
RX
RX
RX

Load Z

30 - 60 kΩ

Load System
IHU
IHU
IHU
TX
IHU

Notes

AMSAT Fox-1
IHU to RF ICD
3.3.1.1 RX Command data shall be read on the rising edge of the RX
Command Strobe signal.
3.3.1.2 Upon an RX Command Strobe rising transition the IHU Systemshall read the signal values RX Command Data 8, RX
Command Data 9, and RX Command Data 10.
3.3.1.3 The duration of an RX Command Strobe signal High state shallbe no less than 500 mS.
3.3.1.4 RX Command Data 11 shall be the most significant bit, RX
Command Data 8 shall be the least significant bit.
Note that the control interface will be specified in a separate document.
3.4 Operational Components
3.4.1 The RF System shall provide operational and audio signals to the
IHU System as shown in Table 4.
Table 4
Pin
Nomenclature
30 RX PTT
32 RX CD
34 RX Audio 1

Type
DigitalDigitalAnalogVoltage

Source System
Load Z
Load System
TX
30 - 60 kΩ
IHU
RX
30 - 60 kΩ
IHU
2 V p-p audioRX
600 Ω, Unbalanced
IHU

Notes
HIGH = HANG TIMER ACTIVE
10 Hz - 7 kHz bandwidth

3.4.1.1 TX Active signal when High shall indicate that the transponder
uplink signal CTCSS hang timer is activating the RFtransmitter.
3.4.1.2 RX CD signal when High shall indicate that the RF receiver
detects a signal on the uplink.

AMSAT Fox-1
IHU to PSU ICD
Date: August 7, 2012
Version: Version 1.03

AMSAT Fox-1
IHU to PSU Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the Power Supply (PSU) System, as required per the AMSAT Fox-1 System
Requirements Specification document.
1.1

Document History
DATE

VERSION

SUMMARY

February 21, 2012

1.0

Initial version

February 21, 20121.01

Clarify I²C address

March 7, 2012

1.02

2.3.1 updated Vdd to 3.0V

August 7, 2012

1.03

Remove BATT1 data fields and adjust message
accordingly

1.2 Document Scope
The purpose of this document is to specify the message format and the I²C bus hardware
operation for the communications between the IHU and the PSU as described in the
AMSAT Fox-1 System Requirements Specification.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture SpecificationAMSAT Fox-1
IHU to PSU ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall be the I²C Master.
2.1.2 The PSU shall be the I²C Slave.
2.1.2.1 The IHU shall request the PSU to send.
2.1.2.2 The PSU shall send a single telemetry data message.
2.1.3 Each telemetry data message sent by the PSU shall be preceded by aheader containing the message version and the software version of thePSU.
2.1.4 Message byte order shall be Little Endian.
2.2

General Message Requirements

2.2.1 Each telemetry data message shall contain a header block, a data block,and a CRC block.
2.2.2 The PSU shall sample data at a rate sufficient to provide telemetry data to
the IHU at least every 15 seconds.
2.3

I²C Bus Hardware Interface Requirements

2.3.1 The I²C Vdd shall be 3.0V.
2.3.2 The bus speed shall be Fast (400kbit/s).
2.3.3 The PSU I²C 7 bit address shall be 0x10.

AMSAT Fox-1
IHU to PSU ICD

3 Message Content Requirements
3.1

Message Header Block3.1.1 The message header block shall be constructed as shown in table 1.
Table 1

Field

Size (Bytes)

Type

Value

Description

Message
Version2

Unsigned
integer

Variable

Message ICD version

SoftwareBuild

2

Unsigned
integer

Variable

Software Build version

3.1.1.1 The Message Version shall be an integer representing the IHU to PSU
ICD document version number from which the message format isderived, having the decimal point removed (e.g. version 1.03 would be
103 decimal or 0x67).
3.1.1.2 The Software Build shall be an integer representing the software build
version number of the PSU system, having the decimal point removed(e.g. version 1.03 would be 103 decimal or 0x67).
3.2

Message Data Block3.2.1 The message data block shall be constructed as shown in Table 2.
Table 2

Field
DATA

Size (Bytes)
28

Type

Value

Unsigned
integers

Variable

Description
Message data

AMSAT Fox-1
IHU to PSU ICD
3.2.2 The message data block shall contain the DATA fields as shown in Table 3.
Table 3Field

Size (Bytes)

TOTAL I2

+X PANEL V

2-X PANEL V

2+Y PANEL V

2-Y PANEL V

2+Z PANEL V

2-Z PANEL V

2+X PANEL T

2-X PANEL T

2+Y PANEL T

2-Y PANEL T

2+Z PANEL T

2- Z PANEL T

2

SPIN

2

Type
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer

Value

Description

Variable

Total system DC current raw value

Variable+X solar panel voltage raw value

Variable-X solar panel voltage raw value

Variable+Y solar panel voltage raw value

Variable-Y solar panel voltage raw value

Variable+Z solar panel voltage raw value

Variable-Z solar panel voltage raw value

Variable+X solar panel temperature raw value

Variable-X solar panel temperature raw value

Variable+Y solar panel temperature raw value

Variable-Y solar panel temperature raw value

Variable+Z solar panel temperature raw value

Variable-Z solar panel temperature raw value

Variable

Calculated spin rateAMSAT Fox-1
IHU to PSU ICD
3.3

CRC Block3.3.1 The CRC block shall be constructed as shown in Table 4.
Table 4Field

Size (Bytes)

Type

Value

Description

CRC

1

CRC

Variable

CRC-8-CCITT

3.3.1.1 The CRC shall be CRC-18-CCITT (0x07).

4 Message Integrity
4.1.1 If the CRC fails, the message shall be considered invalid.
4.1.2 If the Message Version does not match the message version in use for theconstruction of messages on the IHU system, the message shall beconsidered invalid.

AMSAT Fox-1
IHU to PSU ICD

5 Message Flow Diagrams
5.1

READ

IHU

PSU

START READ

TELEMETRY DATA MESSAGESTOPIHU HandlingEndAMSAT Fox-1
IHU to Battery ICD
Date: August 7, 2012
Version: Version 1.00

AMSAT Fox-1
IHU to Battery Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the Battery (BATT1) System, as required per the AMSAT Fox-1 System
Requirements Specification document.
1.1

Document History
DATE

VERSION

SUMMARY

August 7, 2012

1.00

Initial version

1.2 Document Scope
The purpose of this document is to specify the message format and the I²C bus hardware
operation for the communications between the IHU and the BATT1 as described in the
AMSAT Fox-1 System Requirements Specification.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture SpecificationAMSAT Fox-1
IHU to Battery ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall be the I²C Master.
2.1.2 The BATT1 shall be the I²C Slave.
2.1.2.1 The IHU shall request the BATT1 to send.
2.1.2.2 The BATT1 shall send a single telemetry data message.
2.1.3 Each telemetry data message sent by the BATT1 shall be preceded by aheader containing the message version and the software version of theBATT1.
2.1.4 Message byte order shall be Little Endian.
2.2

General Message Requirements

2.2.1 Each telemetry data message shall contain a header block, a data block,and a CRC block.
2.2.2 The BATT1 shall sample data at a rate sufficient to provide telemetry data
to the IHU at least every 15 seconds.
2.3

I²C Bus Hardware Interface Requirements

2.3.1 The I²C Vdd shall be 3.0V.
2.3.2 The bus speed shall be Fast (400kbit/s).
2.3.3 The BATT1 I²C 7 bit address shall be 0x1B.

AMSAT Fox-1
IHU to Battery ICD

3 Message Content Requirements
3.1

Message Header Block3.1.1 The message header block shall be constructed as shown in table 1.
Table 1

Field

Size (Bytes)

Type

Value

Description

Message
Version2

Unsigned
integer

Variable

Message ICD version

SoftwareBuild

2

Unsigned
integer

Variable

Software Build version

3.1.1.1 The Message Version shall be an integer representing the IHU to BATT1
ICD document version number from which the message format isderived, having the decimal point removed (e.g. version 1.03 would be
103 decimal or 0x67).
3.1.1.2 The Software Build shall be an integer representing the software build
version number of the BATT1 system, having the decimal point removed(e.g. version 1.03 would be 103 decimal or 0x67).
3.2

Message Data Block3.2.1 The message data block shall be constructed as shown in Table 2.
Table 2

Field
DATA

Size (Bytes)
14

Type

Value

Unsigned
integers

Variable

Description
Message data

AMSAT Fox-1
IHU to Battery ICD
3.2.2 The message data block shall contain the DATA fields as shown in Table 3.
Table 3Field

Size (Bytes)

CELL 1 V

2

CELL 2 V

2

CELL 3 V

2

CELL 4 V

2

CELL 5 V

2

CELL 6 V

2

CELL T

2

Type
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer
Unsigned
integer

Value

Description

Variable

Battery cell 1 voltage raw value

Variable

Battery cell 2 voltage raw value

Variable

Battery cell 3 voltage raw value

Variable

Battery cell 4 voltage raw value

Variable

Battery cell 5 voltage raw value

Variable

Battery cell 6 voltage raw value

Variable

Battery temperature raw value

AMSAT Fox-1
IHU to Battery ICD
3.3

CRC Block3.3.1 The CRC block shall be constructed as shown in Table 4.
Table 4Field

Size (Bytes)

Type

Value

Description

CRC

1

CRC

Variable

CRC-8-CCITT

3.3.1.1 The CRC shall be CRC-18-CCITT (0x07).

4 Message Integrity
4.1.1 If the CRC fails, the message shall be considered invalid.
4.1.2 If the Message Version does not match the message version in use for theconstruction of messages on the IHU system, the message shall beconsidered invalid.

AMSAT Fox-1
IHU to Battery ICD

5 Message Flow Diagrams
5.1

READ

IHU

BATT1

START READ

TELEMETRY DATA MESSAGESTOPIHU HandlingEndAMSAT Fox-1
IHU to Attitude Determination Experiment ICD
Date: June 29, 2012
Version: Version 2.0

AMSAT Fox-1
IHU to Attitude Determination Experiment Interface
Control Document
1 Introduction
This document specifies the message interface and the power activation interface
between the Internal Housekeeping Unit (IHU) system and the Experiment Payload, as
required per the AMSAT Fox-1 Attitude Determination Experiment Payload System
Requirements Specification document.
The experiment is expected to be provided by students at Penn State University – Eriethrough an AMSAT sponsored senior design project.
1.1

Document History
DATE

VERSION

SUMMARY

February 12, 2012

1.0

From Draft and now SPI

February 15, 2012

1.01

Add SPI Bus Hardware Interface Requirements
Change to DATA block types and values

February 20, 2012

1.02

Add SPI framing and CRC polynomial

February 20, 2012

1.03

Requirements Tracking Changes

February 21, 2012

1.04

Deviation corrected from 90 to 50 per
Experiment System Requirement 3.1.5

February 26, 2012

1.05

Corrected description of SPIN RATE field in
Table 6 to read seconds instead of minutes

March 7, 2012

1.06

Change 6.1.1.1 high state signal to ≥2.4V

April 5. 2012

1.07

Add new DATA field MEMS GYRO STATUS

April 9, 2012

1.08

Added requirement 2.2.4

April 11, 2012

1.1

Add bits to MEMS GYRO STATUS

April 24, 2012

1.11

Set logic level Low as ≤0.2V in 6.1.1.2

June 29, 2012

2.0

Modified extensively due to move of experimentequipment to the IHU card

1.2 Document Scope
The purpose of this document is to specify the data format for the communications
between the Attitude Determination Experiment and the IHU system, as described in the

AMSAT Fox-1
IHU to Attitude Determination Experiment ICD
AMSAT Fox-1 Attitude Determination Experiment Payload System Requirements
Specification.
1.3 References
1. AMSAT Fox-1 System Requirements Specification, Version 1.1, April 29, 2012
2. AMSAT Fox-1 Experiment Payload System Requirements Specification, Version
2.0, June 29, 2012
3. AMSAT Fox-1 IHU Software Architecture Specification, Draft E, January 19, 2012

AMSAT Fox-1
IHU to Attitude Determination Experiment ICD

2 Telemetry Content Requirements
2.1

Telemetry Data Block2.1.1 The telemetry data block shall contain the data fields as shown in Table 1.
Table 1

Field

Size (Bytes)

Type

SPIN RATE

2

Signedinteger

DEVIATION

2

Unsigned
integer

UP TIME

2

Unsigned
integer

Value

Description
Rate of spin of the satellite
about the Z axis, in degrees
Variableper second. Negative-50 toindicates -X spin direction,+50
positive indicates +X spin
direction.
Variable Deviation (wobble) of Z axis
0 to +50 in degrees.
Variable Total seconds since
0 toexperiment payload power65535 up or resetAMSAT Fox-1
IHU Software Architecture Specification
Date: January 19, 2012
Version: draft E

AMSAT Fox-1
IHU Software Architecture Specification
1 Introduction
This document specifies the software architecture design for the IHU of the AMSAT
Fox-1 satellite.
1.1

Document History
DATE

VERSION

SUMMARY

1.2 Document Notes
Procedures are described in this document using a "C-like" psuedocode syntax. This isintended to be a high-level description of the procedures and not compilable code.
1.3

References
1. AMSAT Fox-1, Concept of Operations, Version 1.03, OCT 19, 2011
2. AMSAT Fox-1, System Requirements Specification, Version 1.03, OCT 23, 2011

AMSAT Fox-1
IHU Software Architecture Specification

2 Interfaces
This section specifies the signals and information elements that interface with the IHUsoftware. This document provides the high-level semantics. An interface specification is
expected to be produced for each of these that provides the detailed syntax, bit patterns,
timing, levels etc. required to run the interfaces.
2.1 PSU Telemetry
These data elements come from the PSU via an I2C interface
Name
Battery Cell Volts
Solar Panel Volts
Solar Panel Temperature
Battery Temperature
Avionics Current
Calculated Spin rate

Number of parameters
6
6
6
1
1
1

2.2 IHU Telemetry
This is the telemetry information from the IHU card. It comes directly from the STM3
CPU itself.
NameType Description
CPU Temp A/D STM3 temperature
2.3 RF Telemetry
These are the telemetry elements from the RF card. They are sensed via analog levels thatare sent to the A/D converter channels on the CPU.
Name
PA Current
PA TempRx Osc Temp
Tx Osc Temp

Type
A/D
A/D
A/D
A/D

Description
Tx Power Amplifier Current
Tx Power Amp Temperature
Rx Oscillator Temperature
Tx Oscillator Temperature

AMSAT Fox-1
IHU Software Architecture Specification
2.4 RF Downlink
These are the signals needed to operate the RF downlink. These are via GPIO leads andD/A channels.
Name
Tx Active
RF ModePTT
Tx Narrow
Tx WideType
input
outputoutputD/A output
D/A output

Description
TRUE if 2-min CTCSS timer is active
Selects command or transponder mode
Turns on transmitter if not already on
Low-bit-rate PCM samples to transmit
High-bit-rate PCM samples to transmit

2.5 RF Uplink
These are the signals from RF uplink. These are via GPIO leads and an A/D channel on
the CPU. There is a hardware command decoder on the RF card and the decodedcommands are sent digitally to the IHU card on the GPIO leads. The carrier detect (RxCD) and received audio samples (Rx Audio) are not used on the initial Fox-1 mission.
Name
Rx CD
Rx AudioRx CMD

Type
input
A/D
input

Description
ON if Receiver has carrier - NOT USED
Receiver audio samples - NOT USED
Received command - 4-bits plus strobe

These are the received command values:
Bit Pattern
1xxx
0000
0001
0010
0011
0100
0101
0110
0111

CommandTx Inhibit - done in HW
Reset - done in HW
Test
Clear stored min/max telemetry values
Transponder Mode
Command Mode
- Reserved - Reserved - Reserved -AMSAT Fox-1
IHU Software Architecture Specification
2.6 Antenna System
These are GPIO leads. The antenna system has an active primary deployment mechanism
and a passive backup mechanism. The primary is under control of the IHU software. The
secondary mechanism uses UV radiation from the sun to deploy the antennas in the eventof a failure of the primary mechanism. The backup mechanism may take some time (i.e.
several weeks or months) to deploy the antennas should the primary fail. Therefore, theIHU software must always test the deployment status of the antenna system before
activating the RF transmitter PTT. This is to prevent inadvertent damage to the RFtransmitter if waiting for the secondary mechanism to deploy the antennas.
Since the antenna deployment mechanism has not yet been designed, information about
the precise sequencing and operation of these signals is unknown at this time.
Name
Antenna Deployed
Deploy Antenna1
Deploy Antenna2

Type
input
outputoutputDescription
TRUE if Antennas are deployedTurning ON deploys antenna 1
Turning ON deploys antenna 2

2.7 Zombie Detector
The Zombie detector is an external hardware device that checks the cpu for sanity andradiation-induced, CMOS latch-up conditions. The IHU software must pulse the Alive(GPIO) lead at least once per second. Failure to do this for any reason will cause the IHU
to be power-cycled.
Name Type Description
Alive output Pulse resets Zombie timer
2.8 GPS ReceiverPower is controlled via a GPIO lead. Data is via a serial (UART) port: 4800 bps, 8 data
bits, no parity bit, one stop bit. Uses National Marine Electronics Recommended
Minimum Sentence C format. The actual availability of the GPS receiver for the Fox-1
mission is currently unknown.
NameType Description
GPS Power output controls power to GPS receiver
GPS Data
UART time, longitude, latitude and altitudeAMSAT Fox-1
IHU Software Architecture Specification
2.9 ExperimentThis is the interface to the experiment subsystem. Power is controlled via a GPIO lead.
Data is via an SPI port.
Name
Spin Rate
WobbleEXP Power

Type
input
input
outputDescription
satellite spin rate and direction (signed)
satellite maximum deviation angle from axis
controls power to experiment2.10 Umbilical PortThe umbilical port is functionally a USB port. Unlike a standard USB port, the satellite
batteries can be charged directly from the +5 lead on the USB connector. Since battery
charging may require in excess of the standard USB current capability, a special power
adapter will be used when charging the batteries so the port will appear as a self-powered
device. To the USB host, the satellite will look like a COM port and will allow use of thestandard host USB COM driver. The intention is that the satellite can be easily used with
common terminal emulation programs such as PuTTY.
The Umbilical port is required for system test activities and during launch integration. It
is also available for general use in software development. Additional commands can be
added as needed. The only limitation is that there must not be any capability from thisport to directly activate the transmitter PTT without first testing to insure that theantennas have been deployed as this could accidentally damage the satellite.
The following commands are the minimal set that is required.
2.10.1 Umbilical Port Display Functions
1. Display Telemetry Data
2. Display Experiment Data
3. Display Satellite Mode (command or transponder mode)
4. Display RF Status (Tx active)
5. Display Antenna Status (antennas deployed or not)
6. Display Up Time
7. Display Reset Count
8. Display Software Version
9. Display CPU available

AMSAT Fox-1
IHU Software Architecture Specification

2.10.2 Umbilical Port Control Functions
1. Load the CPU Program (FLASH) Memory
2. Clear Telemetry Min/Max data
3. Clear Reset Count
4. Clear non-volatile memory error count
5. Transponder Mode
6. Command Mode
7. Send Test Message
8. Reset CPU (let Zombie detector fire)
9. Force Antenna Deployment - must be a multi-step command (i.e. always ask "Areyou sure?" !!!)
2.11 Non-volatile Memory
Certain satellite data is stored in non-volatile memory so that it will survive through a
CPU reset. This data needs to be protected to reduce the bit errors due to space radiation.
The protection must be at least double error detecting and single error correcting. The
data stored is as follows:
1.
2.
3.
4.

Telemetry Min/Max values
Experiment Data
CPU Reset countRunning total of non-volatile memory error count (reported in telemetry)

2.12 Debug PortThis is a serial port available for SW development use. It is not needed or used for the
mission. It is expected that a call to a debug "printf()" would direct the output string to
the debug port. It is expected this port would use asynchronous ASCII 8 Data bits, noparity, 1 stop bit, 19.2 k bps. As an alternative, the Umbilical port could be enhanced todisplay software debug messages rather than use a dedicated serial port. This port could
be used for a debugger such as GDB if desired.

AMSAT Fox-1
IHU Software Architecture Specification

3 IHU Start Up SequenceThis is the sequence of events after a CPU reset.
// Run Power On Self Test (POST)// Max duration must be less than one second or pulse the Zombie detector// Check the program FLASH and run some kind of CPU test - at the very// least, test the CPU internal RAM.
calculate checksum on program FLASH;
compare with stored value;if (no match) {halt and let Zombie detector fire;}check CPU;
if (CPU failed) {halt and let Zombie detector fire;}// POST passed. See if we need to deploy the antennas.
if ( (Umbilical Port is NOT active) AND (Antennas are NOT Deployed) ) {wait here 45 minutes while pulsing Zombie detector;
Activate antenna deployment mechanism;}
increment Reset Count in Non-Volatile Memory;boot up system;done;

AMSAT Fox-1
IHU Software Architecture Specification

4 Software ArchitectureThis shows the applications software subsystems and their interfaces after the start up
sequence has been executed (i.e. after system boot up.) The required functionality of eachsubsystem is specified in this section.

Experiment

Experiment
SubsystemGPS

GPS Bu ffer

Experiment
BufferDownlink
Subsystem

RF Down lin k

RF Telem

PSU Telem

Telemetry
Subsystem

Telemetry
BufferDownlink
Co mmands

IHU Telem
Clear
Min/Max

Data Fro m
Telemetry andExperiment
Buffers

Co mmandSubsystem

RF Uplink

Local
Co mmands
Umbilical
Subsystem

Umbilical
Port

CPU
Available

Idle

ZombieDetector

AMSAT Fox-1
IHU Software Architecture Specification
4.1 Telemetry Subsystem
This module is responsible for collecting all of the telemetry and GPS information fromall of the interfaces, doing the Min/Max telemetry processing and providing the data in
the Telemetry Buffer.
4.1.1 Telemetry Buffer Data
Telemetry Data = {CPU Up Time;CPU Reset Count;
GPS Time;
GPS Location;
NV memory error count;
Current Telemetry Values { PSU, IHU, RF }Min/Max Values;}
4.1.2 Telemetry Processing
Do this every 15 seconds;
Get all telemetry parameters from interfaces;
Get GPS data and save in GPS buffer;// Do MinMax processing
Read Min/Max Data from non-volatile memory;
if (Clear Min/Max command was received) {set Min/Max data to current telemetry values;}
else {
update Min/Max data using current values;}
Write new Min/Max data to non-volatile memory;
Get Up Time;
Get Reset Count;
Update data in Telemetry Buffer;
done;

AMSAT Fox-1
IHU Software Architecture Specification
4.2 Experiment Subsystem
The Experiment Subsystem is responsible for running the experiment, collecting the data,
and updating the Experiment Buffer. The functionality of this subsystem depends directlyon the experiment requirements and will likely be different for each the Fox-1 typesatellites.
The initial Fox-1 satellite mission will fly the Penn State Attitude Determination
Experiment. The required operation of this experiment is as follows. Once per day, theexperiment is activated. Experiment data is sampled by the IHU every 3 minutes for one
complete orbit. The orbit period will be approximately 100 minutes and a total of 34 data
samples will be collected. If the experiment successfully runs to completion, the newexperiment data is saved in non-volatile memory and the Experiment Buffer is updatedwith the latest values. In between experiment runs, the Experiment Buffer shall containthe data from the last successful experiment run or all 0's if it has not been run yet.
Note that the above description and following procedure is predicated on the assumptionthat the power system can provide enough power to run the experiment in both commandand transponder mode. Based on current satellite bus and experiment power estimates,
this is the case but should the situation change, this procedure may need to be modified.
4.2.1 Experiment Buffer Data// This is the contents of each experiment data record
type Experiment Record = {Spin Rate;
Wobble Angle;
GPS Location;};// This is the data stored in the Experiment Buffer
Experiment Data = {CPU Up Time;CPU Reset Count;
GPS Time;
Experiment Record[34];}AMSAT Fox-1
IHU Software Architecture Specification
4.2.2 Experiment Processing
Do this once at initialization {Get saved Experiment Data from non-volatile memory;if (data is valid) {copy data to Experiment Buffer;}else {
clear Experiment Buffer;}}
Do this {Wait 24 hours;
Power up experiment;
Get CPU Up Time;
Get CPU Reset Count;
Get GPS Time from GPS Buffer;
Save to a local data structure;// Note: not in non-volatile memory!

Do this every 3 minutes for 34 times{
Get data from experiment;
Get GPS location from GPS Buffer;
Save in a local experiment record;}
Power OFF experiment;
Copy saved local experiment data to non-volatile memory;
Update Experiment Buffer with saved local experiment data;}
done;

AMSAT Fox-1
IHU Software Architecture Specification
4.3 Command Subsystem
This subsystem is responsible for handling demodulation, decoding and execution ofcommands sent from a ground control station via the RF uplink or from a local user via
the Umbilical port. For the initial Fox-1 mission, only the commands decoded in
hardware on the RF card are needed so no additional software demodulation anddecoding is necessary. This capability is reserved for use in future missions.
The Command Subsystem is responsible for controlling the satellite mode. Most
commands are handled by just sending a message to the appropriate subsystem. However,if the satellite is in Command Mode, it must automatically switch to Transponder mode
after 24 hours unless a new Command Mode command has been received.
4.3.1 Command Subsystem Processing
Do this continuously {Monitor RF Uplink interface and Umbilical Subsystem for a new command;
if (Clear MinMax command is received) {send clear telemetry message to Telemetry Subsystem;}
else { // for. all other commands
send corresponding message to Downlink Subsystem;}
if (command was Command Mode) {Start or re-start the 24 hour timer;}
if (received command was Transponder Mode) {Stop the 24 hour timer;}if (24 hour timer expires) {send transponder mode message to Downlink Subsystem;
}
}
done;

AMSAT Fox-1
IHU Software Architecture Specification
4.4 Downlink Subsystem
This subsystem is responsible for generating all of the downlink signals from the IHU.
This includes telemetry and experiment data frames and CW messages.
To create a data frame, the Downlink Process will add framing information such as asatellite identifier, a data type field and frame number. The frame will have forward error
correction and interleaving (FEC) added and the resulting bits will be used to generate themodulation waveform. The data format, framing, FEC and modulation details will be
specified in the Telemetry Interface document.
The Downlink Subsystem has 2 modes of operation; transponder mode and commandmode. These are controlled by messages from the Command Subsystem. The Downlink
Subsystem starts up in transponder mode.
In transponder mode, the data frames are sent continuously as long as the RF transmitteris active. Data frames are sent at the low bit rate (~100 bps) to the RF card using the Tx
Narrow (narrow band) D/A channel. Telemetry and experiment frames are multiplexed at
a 5:1 ratio (i.e. 5 telemetry sent for each experiment frame.) If the RF transmitter isinactive for 5 minutes, a CW Beacon message is sent to the RF card using the Tx Wide
(wide band) D/A channel. This continues every 5 minutes as long as the RF transmitteris otherwise inactive.
In command mode, the RF transmitter is power-cycled at a 50% duty cycle to savepower. Approximately every 20 seconds, the transmitter is activated and the CW beacon
message is transmitted followed by one telemetry frame and one experiment frame. Dataframes are sent at the high bit rate (~10k bps.) The CW and data frames are sent to the RF
card using the Tx Wide (wide band) D/A channel.
In either mode, if a TEST command is received from the uplink subsystem, the IHU will
send the CW Test message and then revert to the prior mode operation.
As noted previously (see section 2.6 Antenna System,) it is essential that the IHUsoftware refrain from activating the RF transmitter if the antennas have not been
deployed. The IHU software will be needed for the launch integration activities while thesatellite is inside the P-POD. Turning on the RF transmitter inside the P-POD could cause
irreparable damage to the satellite. Similarly, should the primary antenna deployment
mechanism fail for whatever reason, the satellite must not activate the RF transmitter
until the backup (passive) mechanism has deployed the antennas.

AMSAT Fox-1
IHU Software Architecture Specification
4.4.1 Downlink Subsystem Processing
At initialization, enter Transponder Mode;
Continuously monitor interface to Uplink Subsystem for a command message;
In Transponder Mode {Put RF card in transponder mode;
While (Tx Active) {Send 5 Telemetry frames at low data rate;
Send 1 Experiment frame at low data rate;}
While (NOT Tx Active) {start 5 minute timer;
if (timer expires before Tx Active) {if (Antennas Deployed) {Put RF card in Command mode;
Turn on PTT;
Send CW beacon message;
Send 1 Telemetry frame at high data rate;
Send 1 Experiment frame at high data rate;
Turn off PTT;
Put RF card in Transponder mode;}}}}
In Command Mode {Put RF card in command mode;
Do this every 20 seconds {// Set time to for 50% RF Tx duty cycle
if (Antennas Deployed) {Turn on PTT;
Send CW beacon message;
Send 1 Telemetry frame at high data rate;
Send 1 Experiment frame at high data rate;
turn off PTT;}}}AMSAT Fox-1
IHU Software Architecture Specification// Downlink Subsystem Processing continued
In either mode {if (TEST command is received) {save current downlink mode;
if (Antennas Deployed) {Put RF card in Command mode;
Turn on PTT;
Send CW TEST message;
Turn off PTT;
Go back to previous downlink mode;
}
}
}
done;
4.5 Umbilical Subsystem
This implements a local user interface on the satellite. This is expected to be used forsystem testing and launch integration activities. The Umbilical Subsystem implements
the commands that are specified in the Umbilical Port section of this document (section
2.1 Umbilical Port.) It is also available for software development use. This subsystem is
not used in orbit.
4.6 Idle Subsystem
This subsystem handles the Zombie Detector and calculates the average available CPU. It
is intended that this Subsystem will run only when no other Subsystem has anything to
do. The Zombie detector is intended to detect transient CPU failures due to radiation
events that cause a system lockup. The Zombie Detector must not be serviced via aninterrupt as this could defeat the lockup protection.

AMSAT Fox-1
IHU Software Architecture Specification

5 System Considerations
5.1 Physical Device Drivers
This software is needed to access and control the IHU hardware.
1.
2.
3.
4.
5.
6.
7.

I2C
SPI
UART
A/D converter channels
D/A converter channels
GPIO inputs
GPIO outputs

5.2 Logical Device Drivers
This is the software needed to support the IHU interfaces. They may make use of one ormore underlying hardware drivers and provide the logical interfaces for the applications
software.
1. PSU Telemetry
2. IHU Telemetry
3. RF Telemetry
4. RF Downlink
5. RF Uplink
6. Antenna System
7. Zombie Detector
8. GPS Receiver
9. Experiment
10. Umbilical Port
11. Non-volatile (EDAC) Memory
12. Debug Port (i.e. "printf()" facility)
5.3 Operating System
The IHU software will use the free version of the FreeRTOS operating system.
5.3.1 OS Task List and Priorities
5.3.2 Inter-Task Communications

AMSAT Fox-1
IHU Software Architecture Specification
5.4 Performance Requirements
The Downlink Tx Audio D/A converters have hard real-time requirements. DMA should
be considered to offload the CPU for these interfaces.
5.5 CPU and Memory Constraints
Max CPU is 32 MHz.
Max RAM is 32K Bytes
Program FLASH is 128K bytes
5.6 Operational Constraints
System is intended to run on orbit but must also be able to run inside the P-Pod to support
the launch integration activities. Inside the P-POD, the antennas MUST NOT be
deployed automatically and the RF transmitter MUST NOT be activated!
5.7 Modularity and Maintainability
The experiment will likely be changed for each future Fox-1 type satellite mission. The
experiment processing software needs to be modularized so it is easy to change. New
experiments may have different up link and downlink requirements.

6 External Interface Specifications
Although not part of this document, detailed specifications are needed for each externalinterface:









PSU Interface
RF System Interfaces
Experiment Interface
RF Downlink (Telemetry)
Command Uplink
Umbilical Port
Antenna System
Zombie Detector

7 SummaryThis document specifies the Software Architecture for the AMSAT Fox-1 satellite. This
specification covers the initial mission flying the Penn State Attitude Experiment. Future
missions may require changes to this specification in order to support the experiment.

Fox1 Antenna Details 2012-08-05

Aug 5, 2012

Peak gain = +2.0 dBi

2m antenna pattern in XZ plane(theta cut at phi = 0 deg.)
Vertical Polarization (relative to satellite’s XY
plane), horizontal, and total polarization.

Aug 5, 2012

Peak gain = +2.0 dBi

2m antenna pattern in YZ plane(theta cut at phi = 90 deg.)
Vertical Polarization (relative to satellite’s XY
plane)

Aug 5, 2012

Peak gain = -3.4 dBi

2m antenna patternconical (phi) cut at theta = 30 deg. (60 deg.
Elevation); Vertical Polarization (relative tosatellite’s XY plane)

Aug 5, 2012

Peak gain = -0.7 dBi

2m antenna patternconical (phi) cut at theta = 45 deg. (45 deg.
Elevation); Vertical Polarization (relative tosatellite’s XY plane)

Aug 5, 2012

Peak gain = +1.0 dBi

2m antenna patternconical (phi) cut at theta = 60 deg. (30 deg.
Elevation); Vertical Polarization is relative tosatellite’s XY plane.

Aug 5, 2012

Peak gain = +1.8 dBi

2m antenna patternconical (phi) cut at theta = 75 deg. (15 deg.
Elevation); Vertical Polarization is relative tosatellite’s XY plane.

Aug 5, 2012

Peak gain = +2.0 dBi

2m antenna patternconical (phi) cut at theta = 90 deg. (0 deg.
Elevation); Vertical Polarization is relative tosatellite’s XY plane.

Aug 5, 2012

Peak gain = +1.9 dBi

2m antenna patternconical (phi) cut at theta = 105 deg. (-15 deg.
Elevation); Vertical Polarization is relative tosatellite’s XY plane.

Aug 5, 2012

Peak gain = +2.0 dBi

2m antenna patternconical (phi) cut at theta = 120 deg. (-30 deg.
Elevation); Vertical Polarization is relative tosatellite’s XY plane.

Aug 5, 2012

2m antenna pattern 3D

Peak gain = +2.0 dBi

Nadir

Aug 5, 2012

Base impedance of 598 mm 2 m antenna with the
437 MHz antenna floating (at 146 MHz)Aug 5, 2012
Aug 5, 2012

Base impedance of 597 mm 2 m antenna with the
437 MHz antenna grounded (at 146 MHz)Aug 5, 2012

Base impedance of 597 mm 2 m antenna with a 7 pF
shunt capacitor at base of antenna.
The 437 MHz antenna is grounded (at 146 MHz).

Aug 5, 2012

Slides that follow are for the 437 MHz antenna on the+Z edge of the +Y solar panel.

Peak gain = +2.3 dBi

70 cm antenna pattern in XZ plane(theta cut at phi = 0 deg.)
Vertical Polarization is relative to satellite’s XY
plane.

Aug 5, 2012

Peak gain = +3.3 dBi

70 cm antenna pattern in YZ plane(theta cut at phi = 90 deg.)
Vertical Polarization is relative to satellite’s XY
plane.

Aug 5, 2012

Peak gain = +2.3 dBi
Min. Gain = -1.6 dBi
3.9 dB variation

70 cm antenna patternconical (phi) cut at theta = 45 deg. (45 deg.
elevation)
Aug 5, 2012

Peak gain = +2.3 dBi
Min. Gain = -1.6 dBi
3.9 dB variation

70 cm antenna patternconical (phi) cut at theta = 60 deg. (30 deg.
elevation)
Aug 5, 2012

Peak gain = +2.3 dBi
Min. Gain = -1.6 dBi
3.9 dB variation

70 cm antenna patternconical (phi) cut at theta = 75 deg. (15 deg.
elevation)
Aug 5, 2012

Peak gain = +2.3 dBi
Min. Gain = -1.6 dBi
3.9 dB variation

70 cm antenna patternconical (phi) cut at theta = 90 deg. (0 deg.
elevation)
Aug 5, 2012

Peak gain = +2.3 dBi
Min. Gain = -1.6 dBi
3.9 dB variation

70 cm antenna patternconical (phi) cut at theta = 105 deg. (-15 deg.
elevation
Aug 5, 2012

Peak gain = +2.3 dBi
Min. Gain = -1.6 dBi
3.9 dB variation

70 cm antenna patternconical (phi) cut at theta = 120 deg. (-30 deg.
elevation
Aug 5, 2012

Peak gain = +2.3 dBi
Min. Gain = -1.6 dBi
3.9 dB variation

70 cm antenna patternconical (phi) cut at theta = 135 deg. (-45 deg.
elevation
Aug 5, 2012

Peak gain = +2.3 dBi
Min. Gain = -1.6 dBi
3.9 dB variation

70 cm antenna patternconical (phi) cut at theta = 150 deg. (-60 deg. Elevation)
Aug 5, 2012

Peak gain = +2.3 dBi
Min. Gain = -1.6 dBi
3.9 dB variation

70 cm antenna patternconical (phi) cut at theta = 165 deg. (-75 deg. Elevation)
Aug 5, 2012

Peak gain = -1.7 dBi
Min. Gain = -11.4 dBi
9.7 dB variation

70 cm RHCP and LHCP antenna patternconical (phi) cut at theta = 150 deg. (-60 deg. Elevation)
Aug 5, 2012

FOX1 IHU SOFTWARE COMPONENTS
Version 1.0, April 1, 2012F 1 Downlink
Fox‐1
Dli k PPower A
Amplifierlifi
Prototypeyp

Measurement results
Marc Franco, N2UO
August 17, 2012

Power supply voltage sweep
Frequency: 145.9 MHz
T
Temp.:
25°C
Pin: 12 dBm
Vcc

Current [mA]

Pout [dBm]

Pout [W]Pdc [W]

Eff [%]

3.2

169

26.32

0.429

0.541

79.2

3.3

174

26.56

0.453

0.574

78.9

3.4

179

26.81

0.480

0.609

78.8

3.5

184

27.05

0.507

0.644

78.7

3.6

190

27.28

0.535

0.684

78.2

3.7

195

27.51

0.564

0.722

78.1

3.8

200

27.7

0.589

0.760

77.5

3.9

206

27.92

0.619

0.803

77.1

4

211

28.13

0.650

0.844

77.0

4.1

215

28.29

0.675

0.882

76.5

4.2

221

28.49

0.706

0.928

76.1

Temperature testing

Frequency: 145.9 MHz
Vcc: 3.3 V
Pin: 12 dBm

Temp [°C]

2nd harm. [dBc]

Current [mA]

Pout [dBm]

Pout [W]Pdc [W]

Eff [%]

‐40

‐59 4
‐59.4

181

26 92
26.92

0 492
0.492

0 597
0.597

82 4
82.4

25

‐60.8

174

26.56

0.453

0.574

78.9

85

‐60

166

26.19

0.416

0.548

75.9

Output spectrum

Date: 17.AUG.2012

15:26:56• The third harmonic is guaranteed to be at least ‐75
75 dBc(below measurement capability)

Ruggedness and stability• Test conditions:– Vcc: 3.3 to 4.2 V– Pin: 12 dBm– Load mismatch: short circuit, open circuit, various
values in between• Results:– No failure or degradation in performance after tests– No oscillations or spurs observedFuture work
• Awaitingg exciter board to performpinterface with theamplifier• A driver stage may be needed• After
Aft integrationi t
ti iis complete,l t more environmentalit l anddperformance tests will be performed• Final PCB layout, schematic and bill of materials will be
generated after all the tests are complete• Hand assembled prototype using existing PC
boardsReceiving FOX-1 Satellite on 2 meters
Satellite Transmitter
PowerPower (dBm0)
Antenna Gain
EIRP

Path Loss
Orbit Altitude
Earth Radius
Elevation Angle
Slant Range @ 0º
Slant Range @ elevation angle
Slant Range @ 90º
Frequency
wavelength
Path Loss @ 0º elevation
Path Loss @ elevation angle
Path Loss @ 90º elevation

400.00 mW
26.02 dBm0
1.00 dBi
27.02 dBm0

minimum

650.00 Km
6378.00 Km
10.00 degrees= 0.174533 radians

2951.93 Km
2045.33 Km

10.00 degrees

650.00 Km
145.90 MHz
2.06E-03 Km

2 meters-145.13 dB-141.94 dB

10.00 degrees-131.98 dB

Ground Station
Antenna Gain
Rx Signal Level @ 0º elevation
Rx Signal Level @ elevation angle
Rx Signal Level @ 90º elevation

8.00 dBi-110.10 dB-106.92 dB-96.96 dBhand held "Arrow" antenna as measured by Central States VHF society

Noise
Antenna Temperature
Receiver Noise Figure
Receiver Noise Temperature
Total System Noise Temp
Receiver Bandwidth
Boltzmanns constant
Noise PowerRx Noise Level

1000 K
6.00 dB
864.51 K
1864.51 K
15000.00 Hz
1.38E-23 J/K
3.86E-16 W-124.13 dBm0

Kenwood D7 HT -122 dBm for 12 dB SINAD

Carrier to Noise Ratio
0º elevation@ elevation angle
90º elevation

14.03 dB
17.22 dB
27.17 dB

C/N for 12 dB SINAD

4.00 dB

10.00 degrees

Kenwood D7 HT -122 dBm for 12 dB SINAD

Link Margin
0º elevation@ elevation angle
90º elevation

10.03 dB
13.22 dB
23.17 dB

10.00 degrees

AMSAT

Faculty Advisor: Steven Strom
CoAdvisors: George Walters, Chris Coulston
Industrial Supervisor: Alexander Harvilchuck
Industry Sponsor: IBM

Mike Corona
Brandon Marvenko
Edward Pizzella What is AMSAT?

 What is the experimental payload?
 NASA accepted◦ Fox Satellite project participating in the ELaNa program

PCB 2

PCB 1

 Receive and interpret commands from theIHU (Internal Housekeeping Unit) via SPI
 Average power consumption will not exceed
200mW
 Measure Spin Rate, Deviation, Up Time Respond correctly to IHU commands: Resetand Send PCB will conform to the internal dimensionsof the 1U CubeSat chassis (10x10x10 cm)
 Withstand the launch and space conditions

 Completed Prototype  In Progress Flight Board
•
•
•
•
•
•

AT91SAM7 MCU
Various Interface Headers
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Indicator LEDs
Two MEMS Gyros
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Field

Size (Bytes)

Type

Value

SPIN RATE

2

Signedinteger

Variable-50 to +50

DEVIATION

2

Signedinteger

Variable-50 to +50

UP TIME2

Signedinteger

Variable 032767

Description

Rate of spin of the satellite about the Z
axis, in degrees per second. Negative
indicates -X spin direction, positive
indicates +X spin direction.
Deviation (wobble) of +Z axis indegrees.
Total seconds since experiment
payload power-up or reset[FOX1:XSR:3.4.3]~

|ω|AMSAT Fox-1 Systems Engineering Documentation
By Jerry Buxton, N0JY
Fox-1 Systems Engineer
n0jy@amsat.org
The AMSAT Fox program introduced a new engineering process for AMSAT in which
engineering documentation is provided at each stage of development. We are archiving all of thisdocumentation on an on-line, backed-up, version control server. When the satellite has been
completed, we will have an archive of traceable documentation. This can serve as the basis forplanning and executing future satellite programs and can be updated to apply the lessons learnedof what went well and what did not.
AMSAT is a truly unique organization in that we are a non-profit corporation that manufacturessatellites using a geographically distributed, all-volunteer engineering staff. There are no common
or established guidelines to cover our situation. As such, the Fox program engineering practices
are themselves an evolving process. The practices used are drawn from industry sources,
especially NASA1 and IEEE.
AMSAT has adopted a common industry scheme known as numbered requirements. Eachindividual requirement has a unique number assigned to it. The number allows a very precise
reference to a specific requirement and this enhances the overall traceability of the specifications.
The requirements are tracked throughout the documents using requirements tracking software,from the ConOps down to the test results, in order to verify that all requirements are properly
implemented by the various systems that make up the satellite.
Due to US State Department ITAR2 restrictions, our document server is only available to project
members who have been vetted to meet the requirements for a "US-person." AMSAT, as an
educational organization, would like to publicly release the majority of our design documentation
to serve as a learning tool to anyone interested in satellite development. However, this must be
done in a specific way to meet the ITAR requirements. The information must first be released via
an openly available publication. We would also like to be able to discuss our satellite projects
with our own members, some of whom are not "US-persons" per ITAR. These AMSAT Space
Symposium proceedings provide a convenient mechanism for the needed publication in order tomake this information public domain and allow us to communicate with our members.
While many of these documents were published in the Proceedings of the AMSAT-NA 30th Space
Symposium and AMSAT-NA Annual Meeting, most of these documents have undergone changes
as the satellite design has progressed and evolved and so they will be reproduced in these 2013
Space Symposium proceedings. In addition, these proceedings also present new engineering
documents that have been produced since the last publication.
An introduction to these documents follows.

The ConOps document is the original form describing the expectations of the satellite. It is thegoverning document from which all development is derived.
The System Requirements Specification is a document that provides the top level technicalspecifications derived from the ConOps. This document describes what the system should do.
The inputs, outputs, functions, mass, volume, environment and other external characteristics areincluded and specified in the system requirements. The level of detail for each requirement is
specifically chosen to provide a clear definition of what the systems will do without too muchspecific detail or declaring how it will be done. This allows the engineers latitude in designing thebest approach to satisfying the requirement.
The Avionics System Design Specification is a document that provides specific details of how theavionics system will be designed. The specifications are based on best design choices determinedby the teams. The signals, connections, connectors, volume, and requirements specific to eachsystem are stated in this document so that each system will fit together and function with the othersystems.
The Experiment Payload Requirements are requirements written for the Penn State student
designed attitude determination system. The actual system designed by the students was notconstructed before their graduation. The experiment payload system design is incorporated onto
the IHU board.
The Interface Control Documents (ICD) for the IHU to Attitude Determination Experiment, IHU
to RF System, IHU to PSU, IHU to Battery, IHU to Experiment 1, and IHU to Experiment 4 set
the requirements for connections and communication between the IHU and the various systems.
Each of the systems sends telemetry measurements and other signals to the IHU. The IHU sends
telemetry audio and control signals to the RF System and controls the experiments. The ICD
allows the systems teams to work on their systems knowing that their systems will interface
successfully.
The Downlink Specification Document sets the requirements for the downlink protocol and thedata to be sent in the slow and high speed downlinks. This allows the satellite and ground station
software teams to send the information to the ground and recover the data successfully.
The IHU Software Architecture Specification provides the design specifications needed for thesoftware design and operation of the Internal Housekeeping Unit.
The engineering documents published in these proceedings are what was available at time needed
for inclusion and we hope you find them interesting and informative. AMSAT intends to continue
to make the majority of the final technical documents, exclusive of satellite control information,
available in future publications.

1

NASA Systems Engineering Handbook, NASA/SP-2007-6105 Rev1
International Traffic in Arms Regulations, see:
http://www.pmddtc.state.gov/regulations_laws/itar_official.html

2

AMSAT Fox-1 Satellite
Concept of Operations
Date: October 19, 2011
Version: 1.03

AMSAT Fox-1 Satellite
Concept of Operations
1 Introduction
The AMSAT Echo satellite, also known as AO-51, has been the most widely usedamateur satellite due to its ability to provide basic radio communications with very
simple ground station equipment. It provides an FM repeater function that has very wide
geographical coverage allowing amateur radio operators to communicate over substantial
distances using just a handheld transceiver (i.e. a walkie-talkie) and a small handheld
antenna. This type of satellite operation is often referred to as the EasySat mode due to its
simplicity. It is extremely valuable in providing an introduction to satellite
communications and is often used for demonstrations given at schools, to scoutingorganizations and at amateur radio publicity events.
After 6 years of service, Echo is nearing the end of its life due to battery failure. For thesake of our space education and outreach activities, it is essential that AMSAT quickly
provide a replacement for Echo that can continue to provide access to the EasySat mode.
The Fox-1 satellite is intended as this replacement.
Building on a harsh lesson learned from Echo and inspired by the longevity of AO-71, theFox-1 satellite project will introduce the concept of designed-in, partial-failure operation.
The satellite will be specifically designed so that when the battery fails, the transponder
can continue to operate when the satellite is in sunlight. Similarly, the satellite will be
designed so that the FM transponder can operate without relying on ground control or afunctioning processor in the IHU. These modes are intended to extend the usable life of
the satellite.
In addition to its primary mission as a communications satellite, the Fox-1 satellite will
host an experiment payload. Over the past two academic years, AMSAT has sponsoredsenior design capstone projects to engage university students in a real-world engineeringexperience. The AMSAT projects have focused on aspects of CubeSat design andconstruction. Building on this success, one of the AMSAT sponsored student projects forthe 2011-2012 academic year at Penn State University will be to provide the experiment
payload that will be flown on the Fox-1 satellite. This experiment is a technology
investigation that is of interest to AMSAT.
Our previous spacecraft have often used passive magnetic attitude stabilization. While theresults have been satisfactory, we have no actual data on how well this mechanism works.
Large spacecraft with much higher power budgets have a substantially larger margin oferror with little ill effect. But the error in the stabilization of the antenna system on a
CubeSat is far more of a concern since the transmitter power is very limited.
Additionally, we have typically had to analyze the telemetry data on the ground to try toascertain the satellite spin rate about its magnetic axis. The objective of the student
Page 1 of 6

AMSAT Fox-1 Satellite
Concept of Operations
experiment is to directly measure the satellite spin rate and direction as well as the"wobble" about the magnetic axis using a 3-axis micro electro-magnetic gyroscope and toprovide this information in telemetry to the ground.
AMSAT expects to submit a proposal to the NASA ELaNa 2 program for a low-costlaunch of this satellite. Proposals will be due in November of this year. If accepted, thelaunch would be in the 2013 time frame. While AMSAT believes that this project would
nicely address the goals and objectives of the NASA program, there can be no guaranteethat the proposal will be accepted. However, AMSAT would still be free to purchase amarket-rate launch of this satellite through any of the CubeSat launch integrators such as
Cal-Poly.
1.1

Document History
DATE

VERSION

SUMMARY

Sept 20, 2011

1.00

Base Version
Req. 3.3 updated to 45 min. for NASA LSP-REQ-

October 8, 2011

1.01

317.01, added ref. to NASA LSP-REQ-317.01
in sec. 5, added document history in 1.1

October 9, 2011

1.02

Added Requirements Tracking

October 19, 2011

1.03

Update information on student experiment

1.2 Program Goals and Objectives
The AMSAT Fox-1 satellite program is intended to:
1. Provide an on-orbit FM transponder to allow wide-area communications between
amateur radio operators using simple ground-station equipment.
2. Develop a 1U CubeSat design that can host an experiment payload.
3. Promote closer relationships with universities including student development ofsatellite components and subsystems.
4. Implement a new engineering process that will improve AMSAT's ability to plan,manage and finance satellite projects.
5. Implement an engineering process that will meet the requirements for submissionof proposals to the NASA ELaNa program.
6. Provide required software needed by the AMSAT Operations team to operate thesatellite in orbit and to collect and archive telemetry and experiment data.
7. Complete the satellite development in time for a 2H 2013 launch.
1.3 Mission Overview
The primary mission of the satellite is to provide a wide-area, amateur radio
communications capability that can be accessed using very simple ground stationequipment such as a handheld FM transceiver paired with a small, handheld beamantenna. The satellite communications transponder will employ analog, narrow-band FM
Page 2 of 6

AMSAT Fox-1 Satellite
Concept of Operations
like that typically used on the amateur radio VHF and UHF bands. The satellite is
expected to support the primary mission for at least 5 years in orbit.
The secondary mission of the satellite is to host an experiment payload. The radio
communications capabilities of the satellite will be used to uplink control commands forthe experiment as needed and to downlink data collected from the experiment to groundstations.
1.4 Document Scope
The purpose of this Concept of Operations (CONOPS) document is to describe thesatellite system and how it will be used. This is not a requirements document but provides
operational context that should be helpful in developing and understanding system
requirements and interface specifications.

2 System Description
2.1 Spacecraft
The Fox-1 satellite is expected to have the following features and characteristics:
x
x
x
x
x
x
x
x
x
x
x
x
x
x

1 Unit CubeSat
650 km, sun-synchronous, circular orbit
FM analog transponder
400 mW or greater RF power output
Uplink on 70 cm band
Downlink on 2 meter band
Experiment payload
Permanent magnetic stabilization
Deployable antennas (no other deployables)
Fixed solar panels on all 6 sides for power
Rechargeable battery to support operation during eclipse
Simple IHU based on a 16-bit microcontroller
Proprietary scheme for control uplink
FSK for sending telemetry and experiment data

This list is preliminary and is subject to change. Please note that this CONOPS is not thecontrolling document for satellite technical specifications.
2.2 Telemetry and Experiment Data
Telemetry data consists of monitored points that provide a measure of the satellite health.
The satellite will autonomously measure these points and transmit them on the downlink.
Experiment data will be collected as per the requirements of the experiment and will be
stored and/or transmitted as needed.

Page 3 of 6

AMSAT Fox-1 Satellite
Concept of Operations
The telemetry and experiment data, will be transmitted in the clear allowing any groundstation to receive it. The information needed to demodulate and decode the downlink
signal will be placed in the public domain. An open-source, software package fordecoding the telemetry and experiment data will be made available by AMSAT.
2.3 Satellite Commands
The satellite will accept commands from a control station. These are used to control themode and operation of the satellite. Commands are intended to be limited to use byauthorized stations only. Private codes and/or unpublished information will be required tocommand the satellite.
2.4 Ground Control Stations
It is expected that control stations will not require any specialized radio equipment but
may need to be able to generate higher radiated power levels than typical for users inorder to gain control of the satellite. This could be accomplished with a high-gain Yagi
antenna and/or a high-power amplifier.
In order to command the satellite, specialized software will likely be required. This
software will be provided as part of the satellite development effort.
2.5 Amateur Radio User Stations
This satellite will use radio standards commonly used on the amateur radio VHF andUHF bands and will not require any specialized equipment for normal operation. A
handheld, dual-band FM transceiver paired with a small hand-held Yagi antenna should
be considered a typical user station. Operation with fixed, omni-directional antennas
should also be possible with typical amateur radio base and mobile transceivers.

3 Satellite Operational Modes
3.1 Quiescent Mode
This mode will be used when the satellite is flight ready but has not yet been integrated
into the deployer (P-POD.) A "Remove Before Flight" pin, inserted into its receptacle on
the satellite, will disconnect the battery and prevent any operation of the avionics.
3.2 Deployer (P-POD) Mode
After the satellite is integrated with the deployer, the "Remove Before Flight" pin will bepulled but deployment switches on the satellite will prevent power-up of the avionics. In
this mode, a test umbilical cable can be connected to a port on the satellite which willallow the avionics to be powered, the battery to be charged and diagnostic tests to be run.
Once a CubeSat has been integrated with its deployer and the launch acceptance tests
have been run, the only way to know if a satellite is still functional is via these diagnostic
tests. Therefore, the diagnostics should be as thorough as possible within the limitationsof the deployer environment.

Page 4 of 6

AMSAT Fox-1 Satellite
Concept of Operations
3.3 Startup Mode
When the satellite is released in orbit, the deployment switches on the satellite will be
activated allowing the satellite to power up. At this point, the satellite will enter Startup
Mode. The satellite will time a 45-minute interval and then deploy the antennas. Thisdelay is required by the CubeSat Design Specification. After deploying the antennas, thesatellite will enter Transponder Mode.
3.4 Transponder Mode
In Transponder Mode, signals appearing on the uplink will be repeated on the downlink.
Amateur radio user stations can use the satellite for general communications with eachother. The satellite will simultaneously send telemetry data on the downlink using thefrequency spectrum below the audible range so as not to interfere with transponder
communications.
The satellite will also monitor the uplink frequency for a command from a control station.
A control station can command the satellite to enter Command Mode.
3.5 Command Mode
Command Mode is intended to support experiments that require more satellite resources
than can be provided in Transponder Mode. This would include more power and higher
downlink data rates.
In Command Mode, signals appearing on the uplink will not be repeated on the downlink.
The satellite will use the downlink exclusively to send telemetry and experiment data. It
will also monitor the uplink for commands from a control station.
After 24 hours, the satellite will automatically return to Transponder Mode unless anothercommand is received. For multi-day experiments, a control station would need to send acommand at least once a day to the satellite to keep it in Command Mode. A control
station can also directly command the satellite to enter Transponder Mode.
3.6 Transmitter Inhibit
In order to meet FCC requirements, the satellite will accept a control station command to
inhibit the transmitter regardless of the operating mode. Once inhibited, the transmitter
will not be activated under any conditions but the satellite will continue to monitor the
uplink for commands. A control station can send a command to remove the inhibit andre-enable the transmitter.
3.7 Partial Failure Operation
Partial failure tolerance is intended to extend the usable life of the primary mission of thesatellite. An experiment may or may not be operable under a partial failure scenario.
3.7.1 Battery Failure
If the battery deteriorates or fails completely including a short circuit, the satellite willcontinue to operate on its solar panels while in the sun. In eclipse, the satellite may power
down. When back in sunlight, the satellite will automatically enter Transponder Mode.
Page 5 of 6

AMSAT Fox-1 Satellite
Concept of Operations
3.7.2 IHU Processor Failure
The satellite will operate in Transponder Mode by default and will not requireintervention from a ground control station. If the processor on the IHU fails, there may belimited control of the satellite and limited or no telemetry data available but thetransponder will continue to operate.

4 Mission Operations Overview
The AMSAT operations and engineering teams will work together to commission thesatellite after launch. Commissioning is expected to last for only a few days to insure thesatellite is operating nominally. After commissioning, the satellite will be turned over tothe operations team. It is expected that the operations team would then open the satellite
for general communications use by any licensed amateur radio station.
When required for experiment operation, an authorized control station can command thesatellite to enter Command Mode. This will turn off the repeater function and enable thetransmission of the telemetry and experiment data. When this data transfer has been
completed, the authorized control station can command the satellite to return toTransponder Mode.
It is expected that the AMSAT operations team will collect and archive all telemetry andexperiment data and make it freely available on the Internet.

5 Reference Documents
1. CubeSat Design Specification Rev. 12. by The CubeSat Program Cal Poly SLO
available from: http://www.cubesat.org/images/developers
2. ITU Radio Regulations, Edition of 2008. available fromhttp://www.itu.int/publ/R-REG-RR-2008/en
3. Launch Services Program, Program Level Poly Picosatellite Orbital Deployer(PPOD) and CubeSat Requirements Document LSP-REQ-317.01 Revision Basic(from NASA)
1

AMSAT OSCAR 7 (AO-7) was launched in 1974 and failed in orbit in 1981 when its battery shortcircuited. In 2002, at least one of the battery cells opened up allowing the satellite to resume operation
when the solar panels are illuminated. As of July 2011, after 37 years in space, AO-7 continues to be
operational in sunlight.
2
Information on the NASA Educational Launch of NanoSatellites (ELaNa) program can be found on theNASA web site: http://www.nasa.gov/offices/education/centers/kennedy/technology/elana_feature.html

Page 6 of 6

AMSAT Fox-1
System Requirements
Date: August 20, 2013
Version: Version 1.4

AMSAT Fox-1
System Requirements Specification
1 Introduction
This document specifies the system level technical requirements for the AMSAT Fox-1
satellite project. This 1 Unit CubeSat is a part of the AMSAT Fox program and includes a
subset of the technical capabilities envisioned for the overall program.
Fox-1 is specifically intended as a replacement for the failing AMSAT Echo (i.e. AO-51)
satellite. Echo has been the most widely used amateur satellite due to its ability to provide
basic radio communications with very simple ground station equipment. Its FM repeater
provides very wide geographical coverage allowing amateur radio operators tocommunicate over substantial distances using just a handheld transceiver (i.e. a walkietalkie) and a small handheld antenna. This so called "EasySat" mode is extremely
valuable in providing an introduction to satellite communications and is often used fordemonstrations given at schools, to scouting organizations and at amateur radio publicity
events. Fox-1 will not duplicate all of the features and modes of Echo but its primary
mission is to provide an FM Transponder in order to allow continued access to thisEasySat mode of communications.
In addition to its mission as a communications satellite, Fox-1 will host an experiment
payload. The satellite will reserve mass and volume for the experiment and will provide
DC power and a communications facility. The experiment is expected to be provided by
students at Penn State University – Erie through an AMSAT sponsored senior design
project.

Page 1 of 11

AMSAT Fox-1
System Requirements
1.1

Document History
DATE

VERSION

SUMMARY

October 5, 2011

1.0

From Draft E

October 8, 2011

1.01

Fix typos in sections 1.2 and 3.5

October 9, 2011

1.02

Add Requirements Tracking

October 23, 2011

1.03

Additional Requirements Tracking

February 21, 2012

1.04

Update Section 3 and Formatting changes

April 18, 2012

1.05

Correction in Section 4

April 22, 2012

1.06

Correct link in Section 1.4 item 2

April 29, 2012

1.1

Revised 3.12.3, 3.12.7, 3.12.8, 3.13.3,
3.13.4, figure 1 to remove RESET and add
IHU OFF and IHU ON commands

August 2, 2012

1.11

Added hidden text for requirements tracking
to be shown in System Design Specification

September 4, 2012

1.12

Added the previously missing “Table 6”label

October 17, 2012

1.2

Changed mode descriptions in 3.13.1 Table
6; changed 3.9.2, 3.9.3, 3.9.4, 3.9.5, 3.9.6,
3.9.7 to reflect IHU involvement; changed
COMMAND MODE to DATA MODE

April 25, 2013

1.3

3.10.2 Remove PA Temperature, add TX T
as RF Transmitter Temperature, OSC T as
referring to TX oscillator no longer
measured changed to read RX oscillator
only

August 20, 2013

1.4

Requirements 3.5.5, 3.6.1, 3.9.6, 3.10.2,
3.11.1, 3.12.4, 3.12.6, 3.13.7.1, 3.13.7.2,
3.13.8, 3.13.9 modified, removed or added
to reflect the evolving satellite design

Page 2 of 11

AMSAT Fox-1
System Requirements
1.2 Document Scope
The purpose of this document is to specify the technical requirements of the satellite at
the system (i.e. "black box") level. It is intended to be used by the hardware, software andmechanical designers to develop the architecture/high-level design specifications. It isalso intended to be used for test planning and development.
1.3 Document Format
This document provides the requirements in numbered format. Each requirement is
assigned a unique number. Additional information such as comments or examples thatare provided for guidance or clarity is italicized to distinguish them from requirements.
1.4 References
1. AMSAT Fox-1, Concept of Operations, Version 1.0, September 19, 2011
2. CubeSat Design Specification Rev. 12. by The CubeSat Program Cal Poly SLO
available from: http://www.cubesat.org/images/developers/cds_rev12.pdf
3. Launch Services Program, Program Level Poly Picosatellite Orbital Deployer(PPOD) and CubeSat Requirements Document LSP-REQ-317.01 Revision Basic(from NASA)
4. ITURadio
Regulations,
Editionof2008.
availablefrom
http://www.itu.int/publ/R-REG-RR-2008/en

Page 3 of 11

AMSAT Fox-1
System Requirements

2 General Requirements
2.1

CubeSat Requirements

2.1.1 The satellite shall meet the requirements specified in the CubeSat Design
Specification Rev. 12.
2.1.2 The satellite shall meet the requirements specified in the NASA LSP-REQ317.01 Revision Basic.
2.1.3 The satellite shall meet the requirements for a 1 unit (single) CubeSat.
2.1.4 The satellite shall provide mass for an experiment payload up to 100 g.
2.1.5 The satellite shall provide volume for an experiment payload up to 95 x 95
x 15.7 mm.
2.2

Environmental Requirements

2.2.1 The satellite avionics shall be designed for -40C to +70C operating
temperature.
2.2.2 The satellite shall be designed to operate in a 650 km, sun-synchronous,
circular orbit.
2.2.3 The satellite shall be designed to tolerate the radiation environment inorbit.
2.3

Reliability Requirements

2.3.1 The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
2.4

RF Frequency Requirements

2.4.1 All RF transmitters shall meet or exceed the requirements specified in the
ITU Radio Regulations, Technical Characteristics, Volume 3, article 3.
2.4.2 All satellite uplinks shall be in the 70 cm band of the amateur satellite
service.
2.4.3 All satellite downlinks shall be in the 2 meter band within the amateur
satellite service.
2.4.4 All satellite transmitter and receiver frequencies shall deviate by no morethan 5 parts-per-million from the specified values including initial accuracy
and temperature variation.
2.4.5 All satellite frequencies shall be coordinated with the IARU.
Note that the band plan with the actual coordinated frequencies will be specified in a
separate document.

Page 4 of 11

AMSAT Fox-1
System Requirements

3 Functional Requirements
3.1

Antenna System

3.1.1 The satellite shall include a deployable antenna system.
3.2

Attitude Control

3.2.1 The satellite shall incorporate passive magnetic stabilization to align the
deployed antennas with the magnetic field of the earth.
3.3

Access Ports

3.3.1 The satellite shall include a "Remove Before Flight" pin as per the CubeSat
Design Specification.
3.3.2 The satellite shall include an umbilical port as per the CubeSat Design
Specification.
3.4

Pre-launch Features

3.4.1 The satellite battery and photovoltaic panels shall be electronicallydisconnected from the avionics when the "Remove Before Flight" pin is
inserted, regardless of the state of the deployment switch(es).
3.4.2 The satellite shall provide the means to charge the battery via the umbilicalport while integrated with the P-POD.
3.4.3 The satellite shall provide the means to run diagnostic tests via theumbilical port while integrated with the P-POD.
3.5

Power

3.5.1 The satellite shall produce electrical power from sunlight.
3.5.2 The satellite shall produce electrical power while in sunlight regardless oforientation and while tumbling or spinning.
3.5.3 The satellite shall produce sufficient average electrical power to operatecontinuously in the orbit of maximum eclipse.
3.5.4 The satellite shall provide sufficient battery capacity to operatecontinuously in the orbit of maximum eclipse.

Page 5 of 11

AMSAT Fox-1
System Requirements
3.6

Experiment3.6.1 The satellite shall provide DC power for experiment payloads.
3.6.2 The satellite shall provide a means to activate and deactivate theexperiment payloads.
3.6.3 The satellite shall provide a means to telemeter data from the experiment
payloads.
Note that the experiment payloads will be specified in a separate documents.
3.7

RF Uplink

3.7.1 The satellite shall include an FM uplink receiver.
3.7.2 The

receiver

shall

have

specifications

as

shown

in

Table

Table 1

Sensitivity
FM Deviation
Audio Bandwidth
Input Frequency Acceptance

3.8-120 dBm for 12 dB SINAD (min.)
5 kHz
3 kHz
Receiver shall accept signals that are off
frequency by ±2.5 kHz (min.)

RF Downlink

3.8.1 The satellite shall include an FM downlink transmitter.
3.8.2 The transmitter shall have specifications as shown in Table 2.
Table 2

Power Output
400 mW (min.)FM Deviation
5 kHz
Audio Bandwidth 3 kHz

Page 6 of 11

1.

AMSAT Fox-1
System Requirements
3.8.3 The transmitter shall provide a means to prevent over modulation.
3.9

FM Transponder

3.9.1 The satellite shall provide an FM transponder via the RF uplink and RF
downlink.
3.9.2 In Transponder Mode, the IHU shall detect the presence of a 67 Hz CTCSS
tone on the uplink.
3.9.3 In Transponder Mode, the downlink transmitter shall be keyed (i.e. PTT-on)
by the IHU for 2 minutes following detection of the 67 Hz CTCSS tone.
3.9.4 In Transponder Mode, the downlink transmitter shall stay on continuously
as long as the 67 Hz CTCSS tone is detected at least once every 2
minutes on the uplink.
3.9.5 In Transponder Mode, the 67 Hz CTCSS tone is not required for a received
signal to be repeated on the downlink, once the transmitter has been
keyed.
3.9.6 In Transponder Mode, if the downlink transmitter has been un-keyed for aperiod of 3 minutes, the satellite shall send "HI THIS IS AMSAT FOX" as avoice announcement on the downlink transmitter.
3.9.7 In the event of shutdown or failure of the IHU, the satellite shall default tosimple carrier operated repeater operation.
3.10 Telemetry Data
3.10.1 The satellite shall collect telemetry data.
3.10.2 The telemetry data shall include at a minimum, measured parameters asshown in Table 3.
Table 3

Parameter NameCELL VPANEL VTOTAL IPA I
BATTERY T
PANEL T
TX T
RX T

Description
Voltages of battery cells
Voltages of solar panels
Total DC current out of power system
DC current into RF power amp
Temperature of battery
Temperatures of solar panels
Temperature of RF transmitter card
Temperature of RF receiver card

Page 7 of 11

AMSAT Fox-1
System Requirements
3.10.3 The measured parameters shall be sampled at least every 15 seconds.
3.10.4 The minimum and maximum values of each of the measured parameters
shall be saved in non-volatile memory.
3.10.5 The telemetry data shall also include at a minimum, calculated parameters
as shown in Table 4.
Table 4

Parameter Name Description
UP TIME
Total seconds since avionics power-up or reset
SPIN
Satellite spin rate and direction
3.10.6 A telemetry frame shall include the current measured values, the saved
minimum and maximum values, and the current calculated values.
Note that the telemetry interface will be specified in a separate document.
3.11 Telemetry Transmission
3.11.1 The satellite shall send slow speed telemetry using FSK on the RF
downlink.
3.11.2 The FSK shall use the frequency spectrum below the audible range.
3.11.3 The telemetry shall be transmitted simultaneously with any transponder
communications.
3.11.4 The telemetry transmission shall include telemetry frames.
3.11.5 The telemetry transmission shall include experiment data.
3.12 Command Capability
3.12.1 The satellite shall provide the means to process commands sent via the
RF uplink from a ground control station.
3.12.2 The commands received via the RF uplink shall not be repeated on the
RF downlink.
3.12.3 The following commands shall be provided, as shown in Table 5.
Table 5

CommandTESTINHIBITIHU OFFIHU ON
CLEAR
TRANSPONDER MODEDATA MODE

Operation
Send test message
Inhibit RF transmission
Power off IHU & PSU
Power on IHU & PSU
Clear stored telemetry
Enter Transponder Mode
Enter Data Mode
Page 8 of 11

AMSAT Fox-1
System Requirements
3.12.4 A TEST command shall cause the satellite to respond by sending a voiceannouncement on the RF downlink.
3.12.5 An INHIBIT command shall cause the satellite to cease RF transmissions.
3.12.6 An IHU OFF command shall cause the IHU and PSU Systems to power
off.
3.12.7 An IHU ON command shall cause the IHU and PSU Systems to poweron.
3.12.8 A CLEAR command shall cause the satellite to clear the saved minimum
and maximum telemetry parameter values.
3.12.9 A TRANSPONDER MODE command shall cause the satellite to enter theTransponder Mode.
3.12.10 A DATA MODE command shall cause the satellite to enter the Data
Mode.
Note that the control interface will be specified in a separate document.

Page 9 of 11

AMSAT Fox-1
System Requirements
3.13 On-Orbit Operating Modes
3.13.1 The satellite shall provide on-orbit operating modes as shown in Table 6.
Table 6

Name
Startup Mode
Transponder Mode
Data Mode

Description
Wait 45 minutes and deploy antennas
FM transponder; PTT and low speed
telemetry via IHUFM transmitter; PTT and high speed
telemetry via IHU

3.13.2 The satellite shall transition between modes as shown in Figure 1.

Figure 1. On-Orbit Operating Modes
Page 10 of 11

AMSAT Fox-1
System Requirements
3.13.3 Upon power-up of the avionics, the satellite shall begin operation from the"Power-up" state as shown in Figure 1.
3.13.4 An IHU ON Command shall cause the satellite to begin operation from the"Power-up" state as shown in Figure 1.
3.13.5 If the antennas have been deployed, the satellite shall enter theTransponder Mode.
3.13.6 If the antennas have not been deployed, the satellite shall enter theStartup Mode.
3.13.7 In Startup Mode, the satellite shall wait 45 minutes, deploy the antennas,
and then enter Transponder Mode.
3.13.7.1 During the 45 minute wait the IHU shall flash a red LED.
3.13.7.2 During the 45 minute wait the IHU shall sound a 1 kHz beeping tone.
3.13.8 In Transponder Mode, the transponder and the slow speed telemetry shallbe active.
3.13.9 In Data Mode, the high speed telemetry shall be active and thetransponder shall not be active. (i.e. signals that appear on the uplink shallnot be repeated on the downlink.)
3.13.10 If another Data Mode command is not received, the satellite shall
automatically enter Transponder Mode 24 hours after having entered Data
Mode.
3.13.11 The RF uplink shall be monitored for commands in all modes.

4 External Interface Documents
To fully specify the satellite technical requirements, the following documents
must also be provided;
1. IARU Coordinated Frequency Plan
2. Downlink Specification
3. Control Interface Specification
4. Experiment Payload Specifications

5 Summary
The Fox-1 satellite will be AMSAT's first CubeSat. Its primary mission is toprovide an FM Transponder communications capability. The secondary mission
is to host a university-provided experiment payload.

Page 11 of 11

AMSAT Fox-1
Avionics System Design Specification
Date: October 4, 2013
Version: 3.82

AMSAT Fox-1
Avionics System Design Specification
1 Introduction
This document contains the system level design specifications for the AMSAT Fox-1 satellite avionics
systems. It is driven by the System Requirements Specification and other documents provided by thedevelopers of the individual systems that make up the satellite system.
1.1. Document History
DATE

VERSION

SUMMARY

February 21, 2012

1.0

From Draft F

April 9, 2012

1.1

Add signal characteristics, update bus pin connections per System Team
input

April 17, 2012

1.2

Add external connector specification in sections 2.6, 2.12 and 2.14 andreferences in section 6

April 18, 2012

1.21

Add MMCX connectors gender

April 22, 2012

1.3

Minor corrections in signal characteristics, remove +Z antenna deploy
and sensor connections

July 10, 2012

2.0

Many revisions from PDR

July 11, 2012

2.01

One RBF pin removed from bus pin assignments, updated 2.1
interconnect diagram, updated 2.1 signal characteristics

July 21, 2012

2.1

Revised bus signals, bus pin assignments
Updated RF block diagram

July 22, 2012

2.11

Revision to some RF signal descriptions, change antenna/coax
connectors to UMCC type, updated RF block diagram, added driving andload system columns to signal characteristics

September 9, 2012

3.0

Major changes.

September 11, 2012

3.01

Defunct IHU block diagram pending update

September 12, 2012

3.1

Added PCB volume requirements

September 23, 2012

3.11

Change TX PTT to RX PTT, -Z Deploy switches to TX, update figures
and tables accordingly

September 26, 2012

3.12

Update bus and pin assignment drawings

September 27, 2012

3.13

Update bus pin assignment drawings

September 30, 2012

3.14

Update RF block diagram to remove ITAR notice

October 17, 2012

3.15

Import changes to requirements from System Requirements

February 17, 2013

3.2

Incorporate system bus signal nomenclature and pin assignmentchanges

February 28, 2013

3.3

MEC connector changed orientation (flipped) on +X -X +Y -Y panels.

Page 1 of 54

AMSAT Fox-1
Avionics System Design Specification
DATE

VERSION

SUMMARY

March 28, 2013

3.4

Add second –Z PPOD deploy switch (pin 54), PPOD deploy switches
now on TX system card

March 31, 2013

3.41

Updates to the TX, RX, IHU, and BUS pin diagrams.

March 31, 2013

3.42

Adjusted RESERVED pin colors only

April 21, 2013

3.43

Addition of RX Frequency Control, TX Frequency Control, and Sensor
Power signals
Pin reassignments:
Moved pins 52 and 54 to pins 33 and 35 respectively
Moved pins 40 and 42 to pins 29 and 42 respectively
Added the above new signals to pins 42, 40, and 38 respectively

April 25, 2013

3.5

Update per System Requirements 3.10.2 changes. Updated bus
connection pin assignments, bus interconnect diagram, and system bus
signal characteristics account removal of TX OSC Temp and TX PA
Temp and addition of TX Temperature

June 26, 2013

3.6

Add requirements for PSU and BATT1 CPU reset from RX Command
Data, updated IHU block diagram

July 24, 2013

3.7

Add ALERT signal, SENSOR POWER signal, remove RBF2, rename
RBF1 to Solar Safe N, remove RX Command Data connection fromBATT1, flip MEC connector orientation on +X, -X, +Y, -Y panels, update
ME-113 mechanical drawings

August 26, 2013

3.8

Rename RX OSC TEMP to RX Temperature, add Initial Surge Current
Limits for certain systems, move Command Decoder to IHU system (buspin changes), update some bus nomenclature, update System
Requirements for each system per changes to the System Requirements

August 27, 2013

3.81

Correct source and destination for RX Command Strobe in Table 1

September 17, 2013

3.82

Add (move) RSSI to Pin 10, rename Pin 32 as RX CD, add Solar Power
A and Solar Power B to pins 55 and 56, update TX Block Diagram,
remove RX Command Data connection from PSU, update hyperlinks.

1.2. Document Scope
The purpose of this document is to specify the avionics systems and their connections to each other and toexternal components for the satellite. It is intended to be used by the hardware, software, and mechanicaldesigners to develop the architecture and interconnections for the satellite avionics systems.
1.3. Document Format
This document provides these elements in a numbered format. The numbered sections specify each major
system in the satellite while numbered items for each system specify the external connections required andthe number of lines for each connection. Satellite bus and external connections are further described infigures and tables.
Where System Requirements are reproduced their numbers are from the AMSAT Fox-1 System
Requirements Specification.
1.4. References
1. AMSAT Fox-1 ConOps
2. AMSAT Fox-1 System Requirements Specification
3. AMSAT Fox-1 Bus (Signal Connections Diagram)
4. AMSAT Fox-1 Bus Pin Assignment
5. AMSAT Fox-1 Avionics System Design Specification Spreadsheet
6. AMSAT FOX-ME-120_Z_TOPBOTT_SOLAR_PANEL.pdf
7. AMSAT FOX-ME-127_Y_SIDE_SOLAR_PANEL.pdf
Page 2 of 54

AMSAT Fox-1
Avionics System Design Specification
Contents
1 Introduction ............................................................................................................................................. 1
2 Avionics System Bus Signals, Characteristics, and Connections ................................................................ 43 RF Transmitter System ............................................................................................................................. 7
4 RF Receiver System ................................................................................................................................ 13
5 Internal Housekeeping Unit (IHU) System .............................................................................................. 17
6 Power Supply System (PSU).................................................................................................................... 23
7 Battery System ........................................................................................................................................ 36
8 Experiment Payload Systems 1 through 4................................................................................................ 41
9 System Block Diagrams Reference .......................................................................................................... 47
10 System Interconnection References ....................................................................................................... 51

Page 3 of 54

AMSAT Fox-1
Avionics System Design Specification
2 Avionics System Bus Signals, Characteristics, and Connections

Figure 1: Interconnect Diagram

Page 4 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 1: System Bus Signal Characteristics
Pin
Nomenclature
SPI1 NSS
1

Type
DigitalVoltage

2
3

TX PA Current
SPI1 SCK

AnalogDigital0 - 3.0 V

4
5

TX Temperature
SPI1 MISO

AnalogDigital0 - 3.0 V

6
7

Experiment 4 Thermistor
SPI1 MOSI

AnalogDigital

8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23

RX Temperature
Serial RXD
RSSI
Serial TXD
IHU Audio 1 Out
Experiment Enable 1
IHU Audio 2 Out
Experiment Enable 2
RX Command Data 0
Experiment Enable 3
RX Command Data 1
Experiment Enable 4
RX Command Data 2
Not Used
RX Command Data 3
I²C1 SCL

AnalogDigitalAnalogDigitalAnalogDigitalAnalogDigitalDigitalDigitalDigitalDigitalDigitalDigitalDigital

Note¹

IHU
IHU

24
25

RX Command Strobe
I²C1 SDA

DigitalDigital

Note¹

IHU
IHU

26
27
28
29
30
31
32
33
34
35
36
37

IHU RF Control
Not Used
IHU PTT
Solar Safe N
RF TX Active
Alert Signal
RX CD-Z Deploy Switch 1
RX Audio 1-Z Deploy Switch 2
RX Audio 2
I²C2 SCL

DigitalDigitalSwitchDigitalDigitalDigitalSwitchAnalogSwitchAnalogDigital38
39

Sensor Power
I²C2 SDA

AnalogDigital

40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60

TX Frequency Control+Z Thermistor
RX Frequency Control-Z Thermistor-Y Antenna Deploy+Z CIC-Y Antenna Sensor-Z CIC+Y Antenna Sensor
Umbilical USBP+Y Antenna Deploy
Umbilical USBM
Not Used
Umbilical Power Active*RESERVED*
Solar Power A
Solar Power B
Vbatt
Vbatt
Vbatt
Vbatt
Version 2.95

DigitalAnalogDigitalAnalogAnalogPower
Switch
Power
SwitchDigitalAnalogDigital

Note¹

Note¹

Note¹

N/A
Note¹

0 - 3.0 V
3.0 V
0 - 3.0 V
3.0 V
0 - 3 V (audio)
0 - 3 V (audio)

Load Z

Load System
EXP 1-4

Notes
SPI Standard, IHU Master

TX
IHU

30 - 60 kΩ

IHU
EXP 1-4

SPI Standard, IHU Master

TX
IHU

30 - 60 kΩ

IHU
EXP 1-4

Thermistor Circuit
SPI Standard, IHU Master

EXP 4
IHU

N/A

IHU
EXP 1-4

Temperature from Experiment 4 position
SPI Standard, IHU MasterRX
EXP 1-4
RX
IHU
IHU
IHU
IHU
IHU
IHU
IHU
IHU
IHU
IHU

30 - 60 kΩ

IHU
IHU
IHU
EXP 1-4
TX
EXP 1-4

Thermistor Circuit
Async, Mark High
Received Signal Strength Indication
Async, Mark HighFor 5 kHz deviation, 10 Hz - 7 kHz bandwidth
HIGH = Enable EXP 1
IHU Audio 2 Out Not Used on Fox-1A
HIGH = Enable EXP 2(Least Significant Bit) Not Used on Fox-1A
HIGH = Enable EXP 3
Not Used on Fox-1A
HIGH = Enable EXP 4
HIGH = IHU off

30 - 60 kΩ
> 10 kΩ unbal.
> 10 kΩ unbal.

EXP 2
EXP 3
EXP 4

TX

IHU

HIGH = Command Data change
I²C Standard, IHU Master
HIGH = IHU Controls RF
LOW = Standalone Analog Transponder

Note¹

IHU

+3 VDCIHU
IHU

TX RX BATT EXP4
PSU/BATTPower for analog telemetry sensors
I²C Standard, IHU Master

TX
PSU
RX
PSU
PSU
PSU
IHU
PSU
IHU
IHU
PSU
IHU

Not Used on Fox-1A

N/A
0 - 3 V (audio)
N/A
0 - 3 V (audio)

Note¹

N/A
N/A
Vbatt
N/A
N/A
N/A
N/A
Vbatt

Vbatt
Vbatt
3.3 - 4.2 VDC
3.3 - 4.2 VDC
3.3 - 4.2 VDC
3.3 - 4.2 VDC

IHU
BATT
TX
IHU
RX
TX
RX
TX

TX

(Most Significan Bit) HIGH = Inhibit Transmit
I²C Standard, IHU Master

TX
PSU
IHU
BATT
TX IHU
PSU/BATTIHU
PSU/BATTIHU
PSU/BATT

N/A

DigitalPower
PowerPower BusPower BusPower BusPower Bus

Source System
IHU

IHU
EXP 4
IHU
TX
IHU
EXP 4
PSU
TX
PSU
BATT
IHU
BATT

N/A

N/A
> 10 kΩ unbal.
N/A> 10 kΩ unbal.

N/A
N/A
7 Ω resistor
N/A
N.O.
N/A
N.O.
7 Ω resistor

BATT

IHU

PSU
PSU
BATT/PSU
BATT/PSU
BATT/PSU
BATT/PSU

BATT
BATT
ALL
ALL
ALL
ALL

Note¹ All SPI and I²C signals are 3.0 V levels
All Digital signals are CMOS logic levels high impedance load unless otherwise noted

Page 5 of 54

HIGH = TRANSMIT
N.O. for operation
HIGH = RF TX on
HIGH = valid receive signal
N.O. when deployed
10 Hz - 7 kHz bandwidth
N.O. when deployed
RX Audio 2 Not Used on Fox-1A
I²C Standard, IHU Master

Not Used on Fox-1A

N.O. when deployed
N.O. when deployed
USB Standard
USB Standard
HIGH = Running on Umbilical Port Power
Must not use on v1 IHU CardAMSAT Fox-1
Avionics System Design Specification
Note¹ All SPI and I²C signals are 3.0 V levels

All Digital signals are 3.0 V CMOS logic levels high impedance load unless otherwise noted

Figure 2: Complete Bus Connection Pin Assignments

Page 6 of 54

AMSAT Fox-1
Avionics System Design Specification
3 RF Transmitter System
3.1 System Requirements Applicable to RF Transmitter System
2.2.1
2.2.3
2.3.1
2.4.1
2.4.3
2.4.4
2.4.5
3.8.1
3.8.2

The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
All RF transmitters shall meet or exceed the requirements specified in the ITU Radio Regulations,Technical Characteristics, Volume 3, article 3.
All satellite downlinks shall be in the 2 meter band within the amateur satellite service.
All satellite transmitter and receiver frequencies shall deviate by no more than 5 parts-per-million
from the specified values including initial accuracy and temperature variation.
All satellite frequencies shall be coordinated with the IARU.
The satellite shall include an FM downlink transmitter.
The transmitter shall have specifications as shown in Table 2.
Power Output
400 mW (min.)FM Deviation

5 kHz

Audio Bandwidth 3 kHz
3.8.3
3.9.1
3.9.3
3.9.5
3.9.7
3.10.1
3.10.2The transmitter shall provide a means to prevent over modulation.
The satellite shall provide an FM transponder via the RF uplink and RF downlink.
In Transponder Mode, the downlink transmitter shall be keyed (i.e. PTT-on) by the IHU for 2
minutes following detection of the 67 Hz CTCSS tone.
In Transponder Mode, the 67 Hz CTCSS tone is not required for a received signal to be repeated on
the downlink, once the transmitter has been keyed.
In the event of shutdown or failure of the IHU, the satellite shall default to simple carrier operated
repeater operation.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card
Page 7 of 54

AMSAT Fox-1
Avionics System Design Specification
RX T
3.10.33.11.1
3.11.2
3.11.33.12.1
3.12.2
3.12.33.12.43.12.53.12.93.12.103.13.1

3.13.53.13.83.13.9Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.
The satellite shall send slow speed telemetry using FSK on the RF downlink.
The FSK shall use the frequency spectrum below the audible range.
The telemetry shall be transmitted simultaneously with any transponder communications.
The satellite shall provide the means to process commands sent via the RF uplink from a groundcontrol station.
The commands received via the RF uplink shall not be repeated on the RF downlink.
The following commands shall be provided, as shown in Table 5.
CommandOperation
TEST

Send test message

INHIBIT

Inhibit RF transmission

IHU OFFPower off IHUIHU ONPower on IHU

CLEAR

Clear stored telemetry

TRANSPONDER MODE

Enter Transponder Mode

DATA MODE

Enter Data ModeA TEST command shall cause the satellite to respond by sending a voice announcement on the RF
downlink.
An INHIBIT command shall cause the satellite to cease RF transmissions.
A TRANSPONDER MODE command shall cause the satellite to enter the Transponder Mode.
A DATA MODE command shall cause the satellite to enter the Data Mode.
The satellite shall provide on-orbit operating modes as shown in Table 6.
Name
Description
Startup Mode

Wait 45 minutes and deploy antennas

Transponder Mode

FM transponder; PTT and low speed
telemetry via IHU

Data Mode

FM transmitter; PTT and high speed
telemetry via IHU

If the antennas have been deployed, the satellite shall enter the Transponder Mode.
In Transponder Mode, the transponder and the slow speed telemetry shall be active.
In Data Mode, the high speed telemetry shall be active and the transponder shall not be active. (i.e.
signals that appear on the uplink shall not be repeated on the downlink.)
Page 8 of 54

AMSAT Fox-1
Avionics System Design Specification
3.2 Initial Surge Current Limits
3.2.1 The RF Transmitter design shall limit initial inrush current to 2.5 Amperes.
3.3 Volume Requirements Applicable to RF Transmitter System
3.3.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 5 mm from the –Z surface of the PC
board.
3.3.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
3.4 Interface Control Documents Applicable to RF Transmitter System
AMSAT Fox-1 IHU to RF System Interface Control Document

Page 9 of 54

AMSAT Fox-1
Avionics System Design Specification
3.5 RF Transmitter System PCB Bus Connections

Figure 3: RF Transmitter System Bus Connection Pin Assignments

Page 10 of 54

AMSAT Fox-1
Avionics System Design Specification
3.6 RF Transmitter System PCB External Connections
3.6.1 2 meter band RF output, coaxial cable to Transmit Antenna
3.6.2 Spacecraft deployment switches cable(s) TBR
3.6.3 Three connections via Samtec FSI-105-06-L-S-AD connector
3.6.3.1 1 contact -Z Solar Panel Thermistor
3.6.3.2 1 contact -Z Solar Panel CIC +3.6.3.3 1 contact common or - for above four connections
Table 2: External Connection Signal Characteristics
External
Connection
CoaxialCable

Nomenclature
2 meter Antenna ≈ 145.9
MHz

Type
RF

Voltage/Power Source System Load Z
Bus Pin
0 to +30
2 meter
50 Ω unbal.
N/A
dBm
Antenna

Table 3: -Z PCB face FSI-105-06-L-S-AD connector mates to pads on –Z Solar Panel
Pin

Nomenclature

1-Z Thermistor

2

N/C

3

-Z Solar Panel Common

4

N/C

5

-Z CICType

Voltage

Source System

Load Z

Load System

Bus Pin

Analog

N/A

N/A

N/A

PSU

43
Ground
Plane

Power

N/A

N/A

Page 11 of 54

N/A

PSU

47

AMSAT Fox-1
Avionics System Design Specification

Figure 4: RF Transmitter System FSI-105-06-L-S-AD Connection Pin
Assignments

Page 12 of 54

AMSAT Fox-1
Avionics System Design Specification
4 RF Receiver System
4.1 System Requirements Applicable to RF Receiver System
2.2.1
2.2.3
2.3.1
2.4.2
2.4.5
3.7.1
3.7.2

The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
All satellite uplinks shall be in the 70 cm band of the amateur satellite service.
All satellite frequencies shall be coordinated with the IARU.
The satellite shall include an FM uplink receiver.
The receiver shall have specifications as shown in Table 1.
Sensitivity-120 dBm for 12 dB SINAD (min.)FM Deviation

5 kHz

Audio Bandwidth

3 kHz

Input Frequency Acceptance Receiver shall accept signals that are off
frequency by ±2.5 kHz (min.)
3.8.3
3.9.1
3.9.7
3.10.1
3.10.2

3.10.33.12.2
3.13.11

The transmitter shall provide a means to prevent over modulation.
The satellite shall provide an FM transponder via the RF uplink and RF downlink.
In the event of shutdown or failure of the IHU, the satellite shall default to simple carrier operated
repeater operation.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card

RX T

Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.
The commands received via the RF uplink shall not be repeated on the RF downlink.
The RF uplink shall be monitored for commands in all modes.
Page 13 of 54

AMSAT Fox-1
Avionics System Design Specification
4.2 Initial Surge Current Limits
4.2.1 The RF Receiver design shall limit initial inrush current to 0.1 Amperes.
4.3 Volume Requirements Applicable to RF Receiver System
4.3.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
4.3.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
4.4 Interface Control Documents Applicable to RF Receiver System
AMSAT Fox-1 IHU to RF System Interface Control Document

Page 14 of 54

AMSAT Fox-1
Avionics System Design Specification
4.5 RF Receiver System PCB Bus Connections

Figure 5: RF Receiver System Bus Connection Pin Assignments

Page 15 of 54

AMSAT Fox-1
Avionics System Design Specification
4.6 RF Receiver System PCB External Connections
4.6.1 70cm band RF input, coaxial cable to Receive Antenna
Table 4: RF Receiver System External Connection Signal Characteristics
External
Connection
CoaxialCable

NomenclatureType

70 cm RF Input 437 MHz

RF

Voltage/Power Source System
Load Z-60 dBmto -140 70 cm Antenna 50 Ω unbal.
dBm

Page 16 of 54

Bus Pin
N/AAMSAT Fox-1
Avionics System Design Specification
5 Internal Housekeeping Unit (IHU) System
5.1 System Requirements Applicable to Internal Housekeeping Unit (IHU) System
2.2.1
2.2.3
2.3.1
3.3.2
3.4.3
3.6.2
3.6.3
3.9.2
3.9.3
3.9.4
3.9.5
3.9.6

3.9.7
3.10.1
3.10.2

3.10.33.10.4The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
The satellite shall include an umbilical port as per the CubeSat Design Specification.
The satellite shall provide the means to run diagnostic tests via the umbilical port while integrated
with the P-POD.
The satellite shall provide a means to activate and deactivate the experiment payloads.
The satellite shall provide a means to telemeter data from the experiment payloads.
In Transponder Mode, the IHU shall detect the presence of a 67 Hz CTCSS tone on the uplink.
In Transponder Mode, the downlink transmitter shall be keyed (i.e. PTT-on) by the IHU for 2
minutes following detection of the 67 Hz CTCSS tone.
In Transponder Mode, the downlink transmitter shall stay on continuously as long as the 67 Hz
CTCSS tone is detected at least once every 2 minutes on the uplink.
In Transponder Mode, the 67 Hz CTCSS tone is not required for a received signal to be repeatedon the downlink, once the transmitter has been keyed.
In Transponder Mode, if the downlink transmitter has been un-keyed for a period of 3 minutes, thesatellite shall send "HI THIS IS AMSAT FOX" as a voice announcement on the downlink
transmitter.
In the event of shutdown or failure of the IHU, the satellite shall default to simple carrier operated
repeater operation.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card

RX T

Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.
The minimum and maximum values of each of the measured parameters shall be saved in nonvolatile memory.
Page 17 of 54

AMSAT Fox-1
Avionics System Design Specification
3.10.53.10.6
3.11.1
3.11.2
3.11.33.11.43.11.53.12.1
3.12.33.12.43.12.6
3.12.73.12.83.12.93.12.103.13.1

The telemetry data shall also include at a minimum, calculated parameters as shown in Table 4.
Parameter Name Description
UP TIME

Total seconds since avionics power-up or reset

SPIN

Satellite spin rate and direction

A telemetry frame shall include the current measured values, the saved minimum and maximum
values, and the current calculated values.
The satellite shall send slow speed telemetry using FSK on the RF downlink.
The FSK shall use the frequency spectrum below the audible range.
The telemetry shall be transmitted simultaneously with any transponder communications.
The telemetry transmission shall include telemetry frames.
The telemetry transmission shall include experiment data.
The satellite shall provide the means to process commands sent via the RF uplink from a groundcontrol station.
The following commands shall be provided, as shown in Table 5.
CommandOperation
TEST

Send test message

INHIBIT

Inhibit RF transmission

IHU OFFPower off IHUIHU ONPower on IHU

CLEAR

Clear stored telemetry

TRANSPONDER MODE

Enter Transponder Mode

DATA MODE

Enter Data ModeA TEST command shall cause the satellite to respond by sending a voice announcement on the RF
downlink.
An IHU OFF command shall cause the IHU System to power off.
An IHU ON command shall cause the IHU System to power on.
A CLEAR command shall cause the satellite to clear the saved minimum and maximum telemetry
parameter values.
A TRANSPONDER MODE command shall cause the satellite to enter the Transponder Mode.
A DATA MODE command shall cause the satellite to enter the Data Mode.
The satellite shall provide on-orbit operating modes as shown in Table 6.
Name
Description
Startup Mode

Wait 45 minutes and deploy antennas

Page 18 of 54

AMSAT Fox-1
Avionics System Design Specification

3.13.2
3.13.33.13.43.13.53.13.63.13.73.13.83.13.9Transponder Mode

FM transponder; PTT and low speed
telemetry via IHU

Data Mode

FM transmitter; PTT and high speed
telemetry via IHU

The satellite shall transition between modes as shown in Figure 1.
Upon power-up of the avionics, the satellite shall begin operation from the "Power-up" state as
shown in Figure 1.
An IHU ON Command shall cause the satellite to begin operation from the "Power-up" state as
shown in Figure 1.

If the antennas have been deployed, the satellite shall enter the Transponder Mode.
If the antennas have not been deployed, the satellite shall enter the Startup Mode.
In Startup Mode, the satellite shall wait 45 minutes, deploy the antennas, and then enterTransponder Mode.
In Transponder Mode, the transponder and the slow speed telemetry shall be active.
In Data Mode, the high speed telemetry shall be active and the transponder shall not be active. (i.e.
Page 19 of 54

AMSAT Fox-1
Avionics System Design Specification

3.13.103.13.113.13.7.1
3.13.7.2

signals that appear on the uplink shall not be repeated on the downlink.)
If another Data Mode command is not received, the satellite shall automatically enter Transponder
Mode 24 hours after having entered Data Mode.
The RF uplink shall be monitored for commands in all modes.
During the 45 minute wait the IHU shall flash a red LED.
During the 45 minute wait the IHU shall sound a 1 kHz beeping tone.

Page 20 of 54

AMSAT Fox-1
Avionics System Design Specification
5.3 Initial Surge Current Limits
5.3.1 The IHU design shall limit initial inrush current to 0.1 Amperes.
5.4 Volume Requirements Applicable to IHU System
5.4.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
5.4.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
5.5 Interface Control Documents Applicable to IHU System
AMSAT Fox-1 IHU to RF System Interface Control Document
AMSAT Fox-1 IHU to PSU Interface Control Document
AMSAT Fox-1 IHU to Battery Interface Control Document
AMSAT Fox-1 IHU to Attitude Determination Experiment Interface Control Document
AMSAT Fox-1 IHU to Experiment 1 Interface Control Document
AMSAT Fox-1 IHU to Experiment 4 Interface Control Document

Page 21 of 54

AMSAT Fox-1
Avionics System Design Specification
5.6 Internal Housekeeping Unit (IHU) System PCB Bus Connections

Figure 6: IHU System Bus Connection Pin Assignments

Page 22 of 54

AMSAT Fox-1
Avionics System Design Specification
6 Power Supply System (PSU)
6.1 System Requirements Applicable to Power Supply System (PSU)

2.2.1
2.2.3
2.3.1
3.3.1
3.4.1

3.4.2
3.5.1
3.5.2
3.5.3
3.5.4
3.6.1
3.10.1
3.10.2

3.10.33.10.5The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
The satellite shall include a "Remove Before Flight" pin as per the CubeSat Design Specification.
The satellite battery and photovoltaic panels shall be electronically disconnected from the avionics
when the "Remove Before Flight" pin is inserted, regardless of the state of the deployment
switch(es).
The satellite shall provide the means to charge the battery via the umbilical port while integrated
with the P-POD.
The satellite shall produce electrical power from sunlight.
The satellite shall produce electrical power while in sunlight regardless of orientation and whiletumbling or spinning.
The satellite shall produce sufficient average electrical power to operate continuously in the orbit ofmaximum eclipse.
The satellite shall provide sufficient battery capacity to operate continuously in the orbit ofmaximum eclipse.
The satellite shall provide DC power for experiment payloads.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card

RX T

Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.
The telemetry data shall also include at a minimum, calculated parameters as shown in Table 4.
Parameter Name Description

Page 23 of 54

AMSAT Fox-1
Avionics System Design Specification

3.12.33.13.7.1

UP TIME

Total seconds since avionics power-up or reset

SPIN

Satellite spin rate and direction

The following commands shall be provided, as shown in Table 5.
CommandOperation
TEST

Send test message

INHIBIT

Inhibit RF transmission

IHU OFFPower off IHU & PSU

IHU ONPower on IHU & PSU

CLEAR

Clear stored telemetry

TRANSPONDER MODE

Enter Transponder Mode

DATA MODE

Enter Data Mode

During the 45 minute wait the IHU shall flash a red LED.

Page 24 of 54

AMSAT Fox-1
Avionics System Design Specification
6.2 Initial Surge Current Limits
6.2.1 The PSU design shall limit initial inrush current to 0.1 Amperes.
6.3 Volume Requirements Applicable to PSU System
6.3.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
6.3.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 3.0 mm from the +Z surface of the PC
board within the area 0 to 4.0 mm from the +Y and +X edges of the board, and 6.0 mm from the +Z
surface of the PC board in the rest of the board area.
6.4 Interface Control Documents Applicable to PSU System
AMSAT Fox-1 IHU to PSU Interface Control Document

Page 25 of 54

AMSAT Fox-1
Avionics System Design Specification
6.5 Power Supply System (PSU) PCB Bus Connections

Figure 7: PSU Bus Connection Pin Assignments

Page 26 of 54

AMSAT Fox-1
Avionics System Design Specification
6.6 Power Supply System (PSU) PCB External Connections
6.6.1 Three connections to +X Solar Panel using Samtec MEC1-105-02-L-D-NP-A connector
6.6.1.1 1 contact +X Solar Panel Thermistor
6.6.1.2 1 contact +X Solar Panel CIC +6.6.1.3 1 contact common or - for above two connections
6.6.2 Three connections to -X Solar Panel using Samtec MEC1-105-02-L-D-NP-A connector
6.6.2.1 1 contact -X Solar Panel Thermistor
6.6.2.2 1 contact -X Solar Panel CIC +6.6.2.3 1 contact common or - for above two connections
6.6.3 Five connections to +Y Solar Panel using Samtec MEC1-105-02-L-D-NP-A connector
6.6.3.1 1 contact +Y Solar Panel Thermistor
6.6.3.2 1 contact +Y Solar Panel CIC +6.6.3.3 1 contact TX Antenna Deploy
6.6.3.4 1 contact TX Antenna Sensor
6.6.3.5 1 contact common or - for above connections
6.6.4 Five connections to -Y Solar Panel using Samtec MEC1-105-02-L-D-NP-A connector
6.6.4.1 1 contact -Y Solar Panel Thermistor
6.6.4.2 1 contact -Y Solar Panel CIC +6.6.4.3 1 contact RX Antenna Deploy
6.6.4.4 1 contact RX Antenna Sensor
6.6.4.5 1 contact common or - for above connections
6.6.5 All PCB edges that connect to solar panel MEC1-105-02-L-D-NP-A connectors shall havecontact pads on the PCB for all connector pins, whether connected to a trace or not.

Page 27 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 5: +X PCB edge mates to MEC1-105-02-L-D-NP-A connector on +X Solar Panel
Pin

Nomenclature

Type

Voltage

Source System

Load ZBus Pin

1

N/C

2
3

+X Solar Panel Thermistor
N/C

Analog

N/A

N/A

N/A

N/A

4
5

N/C
N/C

6

+X Solar Panel Common
N/C

7
8
9
10

Ground
Plane

N/C
N/C
+X Solar Panel CIC (+)

Power

N/A

Page 28 of 54

N/A

N/A

N/A

AMSAT Fox-1
Avionics System Design Specification

Figure 8: PSU System +X Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

Page 29 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 6: -X PCB edge mates to MEC1-105-02-L-D-NP-A connector on -X Solar Panel
Pin

Nomenclature

Type

Voltage

Source System

Load ZBus Pin

1

N/C

2
3

-X Solar Panel Thermistor
N/C

Analog

N/A

N/A

N/A

N/A

4
5

N/C
N/C

6

-X Solar Panel Common
N/C

7
8 N/C
9 N/C
10 -X Solar Panel CIC (+)

Ground
Plane

Power

N/A

N/A

Page 30 of 54

N/A

N/A

AMSAT Fox-1
Avionics System Design Specification

Figure 9: PSU System -X Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

Page 31 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 7: +Y PCB edge mates to MEC1-105-02-L-D-NP-A connector on +Y Solar Panel
Pin

Nomenclature

Type

Voltage

Source System

Load ZBus Pin

1

N/C

2
3

+Y Solar Panel Thermistor
N/C

Analog

N/A

N/A

N/A

N/A

4
5

+Y Antenna Sensor
N/C

Switch

N/A

PSU

N.O.

48

6

+Y Solar Panel Common
N/C

7
8 +Y Antenna Deploy
9 N/C
10 +Y Solar Panel CIC (+)

GroundPlane
AnalogVbatt

IHU

7 Ω resistor

50

Power

N/A

N/A

N/A

N/A

Page 32 of 54

AMSAT Fox-1
Avionics System Design Specification

Figure 10: PSU System +Y Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

Page 33 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 8: -Y PCB edge mates to MEC1-105-02-L-D-NP-A connector on -Y Solar Panel
Pin

Nomenclature

Type

Voltage

Source System

Load ZBus Pin

1

N/C

2
3

-Y Solar Panel Thermistor
N/C

Analog

N/A

N/A

N/A

N/A

4
5

-Y Antenna Sensor
N/C

Switch

N/A

PSU

N.O.

46

6

-Y Solar Panel Common
N/C

7
8 -Y Antenna Deploy
9 N/C
10 -Y Solar Panel CIC (+)

GroundPlane
AnalogVbatt

IHU

7 Ω resistor

44

Power

N/A

N/A

N/A

N/A

Page 34 of 54

AMSAT Fox-1
Avionics System Design Specification

Figure 11: PSU System -Y Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

Page 35 of 54

AMSAT Fox-1
Avionics System Design Specification
7 Battery System
7.1 System Requirements Applicable to Battery PCB 1 System (BATT1)

2.2.1
2.2.3
2.3.1
3.3.1
3.4.1
3.4.2
3.5.3
3.5.4
3.10.1
3.10.2

3.10.3The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
The satellite shall include a "Remove Before Flight" pin as per the CubeSat Design Specification.
The satellite battery and photovoltaic panels shall be electronically disconnected from the avionics
when the "Remove Before Flight" pin is inserted, regardless of the state of the deployment switch(es).
The satellite shall provide the means to charge the battery via the umbilical port while integrated with
the P-POD.
The satellite shall produce sufficient average electrical power to operate continuously in the orbit ofmaximum eclipse.
The satellite shall provide sufficient battery capacity to operate continuously in the orbit of maximum
eclipse.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card

RX T

Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.

Page 36 of 54

AMSAT Fox-1
Avionics System Design Specification
7.2 Volume Requirements Applicable to Battery PCB 1 System
7.2.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 4.0 mm from the -Z surface of the PC
board within the area 0 to 4.0 mm from the +Y and +X edges of the board, and 1.0 mm from the -Z
surface of the PC board in the rest of the board area.
7.2.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 17.0 mm from the +Z surface of the PC
board.
7.3 Interface Control Documents Applicable to Battery PCB 1 System
AMSAT Fox-1 IHU to Battery Interface Control Document

Page 37 of 54

AMSAT Fox-1
Avionics System Design Specification
7.4 Battery PCB 1 System Bus Connections

Figure 12: Battery 1 System Bus Connection Pin Assignments

Page 38 of 54

AMSAT Fox-1
Avionics System Design Specification
7.5 Battery PCB 1 System External Connections
7.5.1 Umbilical as USB mini type B receptacle
7.5.2 Remove Before Flight as 3.5mm normally open TS jack
Table 9: Battery 1 External Connection Signal Characteristics
External
Connection

Nomenclature

Type

USB 1

USB +5 VDC

AnalogUSB 2

USB Data - (USBM)

DigitalUSB 3

USB Data + (USBP)

DigitalUSB 4GroundRBF 1

Solar Safe N

AnalogVoltage/Power Source System
USB
5 VDC
CONNECTOR
3.0 V
USB
CMOS
CONNECTOR
logic
3.0 V
USB
CMOS
CONNECTOR
logic
USB
CONNECTOR
3.5mm N.O. TS
N/A
jack

*When external supply is connected to USB port

Page 39 of 54

Load ZBus Pin

N/A

N/A

N/A

51

N/A

49

N/A

Ground
Plane

N/A

40

AMSAT Fox-1
Avionics System Design Specification
7.6 Battery PCB 2 System Bus Connections

Figure 13: Battery 2 Bus Connection Pin Assignments

Page 40 of 54

AMSAT Fox-1
Avionics System Design Specification
8 Experiment Payload Systems 1 through 4
8.1 System Requirements Applicable to Experiment Payload Systems 1-4
2.1.4
2.1.5
2.2.1
2.2.3
2.3.1
3.6.1
3.6.2
3.6.3

The satellite shall provide mass for an experiment payload up to 100 g.
The satellite shall provide volume for an experiment payload up to 95 x 95 x 15.7 mm.
The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
The satellite shall provide DC power for experiment payloads.
The satellite shall provide a means to activate and deactivate the experiment payloads.
The satellite shall provide a means to telemeter data from the experiment payloads.
8.2 Initial Surge Current Limits
8.2.1 All Experiment designs shall limit initial inrush current to 0.1 Amperes.
8.3 Volume Requirements Applicable to Experiment Payload System 1
8.3.1 No components, connections other than those connectors stipulated in section 10, andstructures such as shielding or enclosures shall protrude from the –Z surface of the PC board.
8.3.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
8.4 Interface Control Documents Applicable to Experiment 1 Payload System
AMSAT Fox-1 IHU to Experiment 1 Interface Control Document

8.5 Volume Requirements Applicable to Experiment Payload Systems 2 and 3
8.5.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
8.5.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
8.6 Volume Requirements Applicable to Experiment System 4
8.6.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
Page 41 of 54

AMSAT Fox-1
Avionics System Design Specification

8.6.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 5.0 mm from the +Z surface of the PC
board.
8.7 Interface Control Documents Applicable to Experiment 4 Payload System
AMSAT Fox-1 IHU to Experiment 4 Interface Control Document

Page 42 of 54

AMSAT Fox-1
Avionics System Design Specification
8.8 Experiment Payload 1 Systems PCB Bus Connections

Figure 14: Experiment Payload 1-3 Systems Bus Connection Pin Assignments

Page 43 of 54

AMSAT Fox-1
Avionics System Design Specification
8.9 Experiment Payload 4 System PCB Bus Connections

Figure 15: Experiment Payload 4 System Bus Connection Pin Assignments

Page 44 of 54

AMSAT Fox-1
Avionics System Design Specification
8.10 Experiment Payload 4 System PCB External Connections
8.10.1 Three connections using Samtec FSI-105-06-L-S-AD connector
8.10.1.1 1 contact +Z Solar Panel Thermistor
8.10.1.2 1 contact +Z Solar Panel CIC +8.10.1.3 1 contact common or - for above two connections
Table 10: +Z PCB face FSI-105-06-L-S-AD connector mates to pads on +Z Solar Panel
Pin

Nomenclature

1+Z Thermistor

2

N/C

3

+Z Solar Panel Common

4

N/C

5

+Z CICType

Voltage

Source System

Load Z

Load System

Bus Pin

Analog

N/A

N/A

N/A

PSU

41
Ground
Plane

Power

N/A

N/A

Page 45 of 54

N/A

PSU

45

AMSAT Fox-1
Avionics System Design Specification

Figure 16: Experiment Payload 4 System FSI-105-06-L-S-AD
Connection Pin Assignments

Page 46 of 54

AMSAT Fox-1
Avionics System Design Specification
9 System Block Diagrams Reference
9.1 IHU System

Page 47 of 54

AMSAT Fox-1
Avionics System Design Specification
9.2 RF System
9.2.1 RF Transmitter Block Diagram

Page 48 of 54

AMSAT Fox-1
Avionics System Design Specification
9.2.2 RF Receiver Block Diagram (TBR)

Page 49 of 54

AMSAT Fox-1
Avionics System Design Specification
9.3 PSU System

Page 50 of 54

AMSAT Fox-1
Avionics System Design Specification
10 System Interconnection References
10.1 Bus Connectors
10.1.1 Samtec QTH-030-02-L-D-A and QSH-030-01-L-D-A connectors
10.1.2 QTH connector shall be mounted on the +Z surface of each circuit board except the Receive
Antenna PCB / GPS Payload circuit board
10.1.3 QSH connector shall be mounted on the –Z surface of each circuit board
10.2 Bus Connector Documentation
10.2.1 Samtec QSH
10.2.2 Samtec QTH
10.2.3 Samtec QxH High Speed Characterization Report
10.2.4 Samtec QxH Single Ended Channel Properties
10.3 External Connectors
10.3.1 Samtec MEC1-105-02-L-D-NP-A connector mounted on +X, -X, +Y, -Y Solar Panels
10.3.2 Samtec FSI-105-06-L-S-AD connector mounted on -Z face of RF Transmitter System PCB
and +Z face of Experiment Payload 4 System PCB
10.4 External Connector Documentation
10.4.1 Samtec MEC1
10.4.2 Samtec MEC1 Qualification Testing
10.4.3 Samtec FSI
10.5 PCB Connector Layout Documentation
10.5.1 FOX-ME-113_PCB.pdf

Page 51 of 54

AMSAT Fox-1
Avionics System Design Specification
10.6 Systems PCB Connector Layout
10.6.1 Common to All Systems

Page 52 of 54

AMSAT Fox-1
Avionics System Design Specification
10.6.2 RF Transmitter System

10.6.3 PSU System

Page 53 of 54

AMSAT Fox-1
Avionics System Design Specification
10.6.4 Experiment 4 System

Page 54 of 54

AMSAT Fox-1
Attitude Determination Experiment Payload System Requirements
Date: June 29, 2012
Version: 2.0

AMSAT Fox-1
Attitude Determination Experiment Payload System
Requirements Specification
1 Introduction
This document specifies the system level technical requirements for the AMSAT Fox-1
satellite project attitude determination experiment payload.
The Fox-1 satellite is a 1 Unit CubeSat with a primary mission of providing amateur
radio communications. In addition to its mission as a communications satellite, Fox-1
will host an experiment payload. The satellite will reserve mass and volume for theexperiment and will provide DC power and a communications facility. The experiment is
expected to be provided by students at Penn State University – Erie, through an AMSAT
sponsored senior design project.
The goal of the experiment will be to measure the spin rate and direction, about the Z axisof the satellite, and any off Z-axis “wobble”.
1.1

Document History
DATE

VERSION

SUMMARY

November 9, 2011

1.0

From Draft F

December 4, 2011

1.01

Fix formatting

December 23, 2011

1.03

Update references to other documents

December 27, 2011

1.04

Update 2.1.13 for QTH/QSH connectors

February 12, 2011

1.10

Change bus to SPI and add power signal
Removed references to multiple PCBs
and conflicting component placement
Adjust PCB stay out zone and otherrequirements per latest mechanicalrevisions

June 29, 2012

2.0

Modified extensively due to move ofexperiment equipment to the IHU card

1.2 Document Scope
The purpose of this document is to specify the technical requirements of the experiment
payload at the system (i.e. "black box") level. It is intended to be used to by the hardware,
Page 1 of 4

AMSAT Fox-1
Attitude Determination Experiment Payload System Requirements
software and mechanical designers to develop the architecture/high-level design
specifications. It is also intended to be used for test planning and development.
1.3 Document Format
This document provides the requirements in numbered format. Each requirement is
assigned a unique number. Additional information such as comments or examples thatare provided for guidance or clarity are italicized to distinguish them from requirements.
1.4 References
1. AMSAT Fox-1, Concept of Operations, Version 1.03, September 19, 2011
2. AMSAT Fox-1, System Requirements Specification, Version 1.1, April 29, 2012
3. AMSAT Fox-1 IHU to Attitude Determination Experiment Interface Control
Document, Version 2.0, June 29, 2012

Page 2 of 4

AMSAT Fox-1
Attitude Determination Experiment Payload System Requirements

2 General Requirements
2.1

Physical Requirements

2.1.1 The experiment payload shall be constructed on the satellite IHU system
PCB.
2.2

Environmental Requirements

2.2.1 The experiment payload shall be designed for -40C to +70C operating
temperature.

3 Functional Requirements
3.1

Experiment Data

3.1.1 The experiment payload shall measure the spin rate and direction about
the Z axis of the satellite.
3.1.2 The experiment payload shall measure any deviation (wobble) of the Z
axis of the satellite caused by the spin of the satellite.
3.1.3 The experiment payload data shall have an accuracy of 1 degree.
3.1.4 The experiment payload shall be able to resolve the rate of spin in therange of 0 to 50 degrees per second. The experiment payload shall beable to resolve the deviation of the Z axis (wobble) in the range of 0 to
50 degrees.
3.2

Satellite Interface

3.2.1 The experiment data shall be directly collected by the satellite IHU
system.
3.3

Power

3.3.1 The experiment payload shall receive electrical power from the satellite
battery and photovoltaic panels.
3.3.2 The electrical power voltage will be nominally DC 3.6 V.
3.3.3 The satellite IHU system will activate and deactivate the experiment
payload as necessary.
3.3.4 The electrical power drawn by the experiment payload shall not exceed
200 mW.

Page 3 of 4

AMSAT Fox-1
Attitude Determination Experiment Payload System Requirements
3.4

Experiment Data

3.4.1 The IHU system shall process the experiment data for telemetrytransmission†.
3.4.2 The IHU system shall sample the experiment data at a rate sufficient toprovide telemetry data at least every 15 seconds.
3.4.3 The experiment payload data shall include the following measured andcalculated parameters:

Parameter Name

Description

SPIN RATE

Rate of spin of the satellite about the Z axis, in degrees per minute

SPIN DIRECTION Direction of spin of the satellite about the Z axis (+X or –X)
DEVIATION

Deviation (wobble) of +Z axis caused by satellite spin

UP TIME

Total seconds since experiment payload power-up or reset†Note that the telemetry data frame is specified in the AMSAT Fox-1 IHU to Attitude
Determination Experiment Interface Control Document.

4 External Interface Documents
To fully specify the experiment payload technical requirements, the following
documents must also be provided;
1. AMSAT Fox-1 IHU to Attitude Determination Experiment Interface Control
Document

5 Summary
The Fox-1 satellite attitude determination experiment payload will provide data on
the spin and wobble of the passive-magnetically stabilized satellite. This
includes the first known measurements of the wobble about the Z axis of amagnetically stabilized AMSAT satellite.

Page 4 of 4

AMSAT Fox-1
IHU to Attitude Determination Experiment ICD
Date: June 29, 2012
Version: Version 2.0

AMSAT Fox-1
IHU to Attitude Determination Experiment Interface
Control Document
1 Introduction
This document specifies the message interface and the power activation interface
between the Internal Housekeeping Unit (IHU) system and the Experiment Payload, as
required per the AMSAT Fox-1 Attitude Determination Experiment Payload System
Requirements Specification document.
The experiment is expected to be provided by students at Penn State University – Eriethrough an AMSAT sponsored senior design project.
1.1

Document History
DATE

VERSION

SUMMARY

February 12, 2012

1.0

From Draft and now SPI

February 15, 2012

1.01

Add SPI Bus Hardware Interface Requirements
Change to DATA block types and values

February 20, 2012

1.02

Add SPI framing and CRC polynomial

February 20, 2012

1.03

Requirements Tracking Changes

February 21, 2012

1.04

Deviation corrected from 90 to 50 per
Experiment System Requirement 3.1.5

February 26, 2012

1.05

Corrected description of SPIN RATE field in
Table 6 to read seconds instead of minutes

March 7, 2012

1.06

Change 6.1.1.1 high state signal to ≥2.4V

April 5. 2012

1.07

Add new DATA field MEMS GYRO STATUS

April 9, 2012

1.08

Added requirement 2.2.4

April 11, 2012

1.1

Add bits to MEMS GYRO STATUS

April 24, 2012

1.11

Set logic level Low as ≤0.2V in 6.1.1.2

June 29, 2012

2.0

Modified extensively due to move of experimentequipment to the IHU card

1.2 Document Scope
The purpose of this document is to specify the data format for the communications
between the Attitude Determination Experiment and the IHU system, as described in the
Page 1 of 3

AMSAT Fox-1
IHU to Attitude Determination Experiment ICD
AMSAT Fox-1 Attitude Determination Experiment Payload System Requirements
Specification.
1.3 References
1. AMSAT Fox-1 System Requirements Specification, Version 1.1, April 29, 2012
2. AMSAT Fox-1 Experiment Payload System Requirements Specification, Version
2.0, June 29, 2012
3. AMSAT Fox-1 IHU Software Architecture Specification, Draft E, January 19, 2012

Page 2 of 3

AMSAT Fox-1
IHU to Attitude Determination Experiment ICD

2 Telemetry Content Requirements
2.1

Telemetry Data Block2.1.1 The telemetry data block shall contain the data fields as shown in Table 1.
Table 1

Field

Size (Bytes)

Type

SPIN RATE

2

Signedinteger

DEVIATION

2

Unsigned
integer

UP TIME

2

Unsigned
integer

Value

Description
Rate of spin of the satellite
about the Z axis, in degrees
Variableper second. Negative-50 toindicates -X spin direction,+50
positive indicates +X spin
direction.
Variable Deviation (wobble) of Z axis
0 to +50 in degrees.
Variable Total seconds since
0 toexperiment payload power65535 up or reset

Page 3 of 3

AMSAT Fox-1
IHU to RF ICD
Date: August 27, 2013
Version: Version 2.00

AMSAT Fox-1
IHU to RF System Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the RF System, as required per the AMSAT Fox-1 System Requirements
Specification document.
1.1 Document History
DATE

VERSION

March 24, 2012

1.0

SUMMARY
Initial versionndMarch 24, 2012

1.1

Add 2 RX Audio Out section 3.4.1

March 26, 2012

1.2

Section 3.2 rename Zombie to IHU Control,
rename Audio to Audio 1, Section 3.4 remove
RX Audio 2, section 4 removed entirely

March 26, 2012

1.3

Many updates using input from teams

March 30, 2012

1.4

Update 3.4.1.1 to clarify that receive signal
CTCSS is responsible for state

March 31, 2012

1.5

3.3.1.3 updated to read no less than 100 mS

April 24, 2012

1.6

Update impedances and voltages to match SDS

June 18, 2012

1.7

Update 3.3.1.5 per PDR change to SRS, remove
RESET add IHU OFF and IHU ON commands,
signal characteristic updates per PDR, 3.4.1.2 toindicate command station signal strength

September 13, 2012

1.8

Remove IHU CONTROL signal, match signal
characteristics to system design specification

September 16, 2012

1.9

Changes to 3.3.1.1 and Table 4 per Tony

September 18, 2012

1.91

Removed Command Table (section 3.3) and restated section 3.3 requirements accordingly

February 17, 2013

1.92

Incorporate system bus signal nomenclature andpin assignment changes

August 27, 2013

2.00

Move RX Command Decoder to IHU, give IHU
more responsibility for RF System control,
rename RSSI to RX CD, add RSSI to Pin 10

Page 1 of 5

AMSAT Fox-1
IHU to RF ICD
1.2 Document Scope
The purpose of this document is to specify the signal types, levels, and direction forconnections between the IHU and the RF System as described in the AMSAT Fox-1
System Requirements Specification.
1.3 References
1. AMSAT Fox-1 System Requirements Specification
2. AMSAT Fox-1 System Design Specification
3. AMSAT Fox-1 IHU Software Architecture Specification

Page 2 of 5

AMSAT Fox-1
IHU to RF ICD

2 General Requirements
2.1 Telemetry
2.1.1 RF System Telemetry values shall be conveyed as analog voltage
levels sent from the RF System to the IHU System.
2.1.2 The IHU System shall convert the analog signals to digital
representations.
2.1.3 Audio signals for the purpose of conveying telemetry via sub-audible
audio frequencies shall be sent from the IHU System to the RF
System.
2.2 RF System Control
2.2.1 Control of the RF System shall be accomplished by means of digital
signals sent from the IHU System to the RF System.
2.3 Satellite System Command
2.3.1 Command data for the purpose of controlling the satellite shall beprocessed by the IHU System and sent to the RF System.
2.3.2 Command data shall be conveyed to the RF System via digital
signals.
2.4 Operational Components
2.4.1 Demodulated baseband audio signals shall be passed from the RF
System to the IHU System for processing.
2.4.2 Baseband audio signals shall be passed from the IHU System to the
RF System for transmission.
2.4.3 Operational Status signals shall be conveyed as digital signals sentfrom the RF System to the IHU System.
2.5 Signal Transmission
2.5.1 Signals shall use the pin assignments shown in the Fox-1 System
Design Specification document.
2.5.2 Signal connections shall comply with the impedance and signal typeshown in the parameters for each type of signaling.
2.6 Signal Type Definitions and Levels
2.6.1 Analog: 0 – 3.0 VDC analog voltage.
2.6.2 Digital: 3.0 VDC CMOS logic levels.
Page 3 of 5

AMSAT Fox-1
IHU to RF ICD

3 Signal Connection Requirements
3.1 Telemetry
3.1.1 The RF System shall provide raw telemetry values from the RF
System components as shown in Table 1.
Table 1
Pin
Nomenclature
2 TX PA Current
4 TX Temperature
8 RX Temperature

Type
AnalogAnalogAnalogVoltage
0 - 3.0 V
0 - 3.0 V
0 - 3.0 V

Source System
TX
TX
RX

Load Z
30 - 60 kΩ
30 - 60 kΩ
30 - 60 kΩ

Load System
IHU
IHU
IHU

Notes
Thermistor Circuit
Thermistor Circuit

3.1.1.1 The values shall be updated at a rate to provide new samples
at least every 15 seconds.
3.2 RF System Control
3.2.1 The IHU System shall provide control and audio signals to the RF
System as shown in Table 2.
Table 2Pin
Nomenclature
12 IHU Audio 1 Out

TypeVoltage Source System
Analog 0 - 3 V (audio)
IHU

26 IHU RF Control
28 IHU PTTDigitalDigitalLoad Z> 10 kΩ unbal.

IHU
IHU

Load System
TX
TX
TX

Notes
For 5 kHz deviation, 10 Hz - 7 kHz bandwidth
HIGH = IHU Controls RF
LOW = Standalone Analog Transponder
HIGH = TRANSMIT

3.2.1.1 IHU RF Control when High shall indicate IHU presence andcontrol of the RF PTT and audio.
3.2.1.2 IHU RF Control when Low shall indicate loss of IHU control
causing the RF System to operate as a standalone carrier
operated transponder passing audio directly from the receiver
uplink to the transmitter downlink.
3.2.1.3 IHU PTT signal when High shall key the RF transmitter on.
3.3 Satellite System Command
3.3.1 The IHU System shall provide ground station command signals to
the RF System as shown in Table 3.
Table 3
Pin
Nomenclature
22 RX Command Data 3

Type
DigitalVoltage

Source System
IHU

Load Z

Page 4 of 5

Load System
TX

Notes
(Most Significan Bit) HIGH = Inhibit Transmit

AMSAT Fox-1
IHU to RF ICD
3.3.2 An INHIBIT Command (RX Command Data 3 = HIGH) shall cause
the RF System to cease RF transmissions without regard to thestate of any other RF System Control signals.
Note that the control interface will be specified in a separate document.
3.4 Operational Components
3.4.1 The RF System shall provide operational and audio signals to the
IHU System as shown in Table 4.
Table 4
Pin
Nomenclature
10 RSSI
30 RF TX Active
32 RX CD
34 RX Audio 1

Type
Voltage Source System
Analog0 - 3.0 V
RX
DigitalTX
Digital0RX
Analog 0 - 3 V (audio)
RX

Load Z
30 - 60 kΩ
0> 10 kΩ unbal.

Load System
IHU
IHU
TX IHU
IHU

Notes
Received Signal Strength Indication
HIGH = RF TX on
HIGH = valid receive signal
10 Hz - 7 kHz bandwidth

3.4.1.1 RSSI signal shall indicate the relative strength of the received
signal on the uplink.
3.4.1.2 RF TX Active signal when High shall indicate that thetransponder uplink signal CTCSS hang timer is activating the
RF transmitter.
3.4.1.3 RX CD signal shall indicate a valid received signal on the
uplink.

Page 5 of 5

AMSAT Fox-1
IHU to PSU ICD
Date: October 4, 2013
Version: Version 2.00

AMSAT Fox-1
IHU to PSU Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the Power Supply (PSU) System, as required per the AMSAT Fox-1 System
Requirements Specification document.
1.1

Document History
DATE

VERSION

SUMMARY

February 21, 2012

1.0

Initial version

February 21, 20121.01

Clarify I²C address

March 7, 2012

1.02

2.3.1 updated Vdd to 3.0V

August 7, 2012

1.03

Remove BATT1 data fields and adjust message
accordingly

November 7, 2012

1.04

Added PSU CPU Temperature

December 27, 2012

1.10

Change from Bytes to Bits in Message Header
Block, Message Data Block, Message Data (toallow for 12 bit ADC values)

January 2, 2013

1.11

Field sizes back to bytes account I²C
specifications

February 7, 2013

1.12

Correct typo in 3.3.1.1

August 22, 2013

1.13

Remove TOTAL I from Data block

August 22, 2013

1.14

Update I²C speed to 10 kHz

October 4, 2013

2.00

Rework to eliminate STM32L and replace with
ADS7828s

1.2 Document Scope
The purpose of this document is to specify the message format and the I²C bus hardware
operation for the communications between the IHU and the PSU as described in the
AMSAT Fox-1 System Requirements Specification.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification
Page 1 of 4

AMSAT Fox-1
IHU to PSU ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall be the I²C Master.
2.1.2 The PSU shall be the I²C Slave.
2.1.2.1 The IHU shall request the PSU to send the data for a specific Device andchannel.
2.1.2.2 The PSU shall send that specific Device and channel data.
2.1.3 The IHU shall test for the presence both PSU system Devices.
2.1.4 The IHU shall only poll the PSU system Device(s) present, for data.
2.2

General Message Requirements

2.2.1 The IHU shall sample data at a rate sufficient to provide downlink telemetry
data at least every 15 seconds.
2.2.2 For both Devices the ADS 7820 A/D converter shall always be commandedon (PD-0 bit = 1).
2.2.3 For both Devices the ADS 7820 Internal Reference shall always becommanded on (PD-1 bit = 1).
2.2.4 TFor both Devices the ADS 7820 shall always be commanded for singleended inputs.
2.3

I²C Bus Hardware Interface Requirements

2.3.1 The I²C Vdd shall be 3.0V.
2.3.2 The bus speed shall be Standard (10 kHz).
2.3.3 The PSU system Device 1 I²C 7 bit address shall be 0x49.
2.3.4 The PSU system Device 2 I²C 7 bit address shall be 0x4A.

Page 2 of 4

AMSAT Fox-1
IHU to PSU ICD

3 Message Content Requirements
3.1

Measured Values

3.1.1 The measured data fields for Device 1 and their associated ADS 7828
channels shall be as shown in Table 1.
Table 1

Field

ChannelType

Min Value Max Value

Description-X PANEL V

0

Unsigned

0x00

0xFFF

-X PANEL V-Y PANEL V

1

Unsigned

0x00

0xFFF

-Y PANEL V-Z PANEL V

2

Unsigned

0x00

0xFFF

-Z PANEL V-X PANEL T

3

Unsigned

0x00

0xFFF

-X PANEL T-Y PANEL T

4

Unsigned

0x00

0xFFF

-Y PANEL T-Z PANEL T

5

Unsigned

0x00

0xFFF

-Z PANEL T

Not used

6

-

-

-

-

Not used

7

-

-

-

-

3.1.2 The measured data fields for Device 2 and their associated ADS 7828
channels shall be as shown in Table 2.
Table 2Field

Channel

Type

Min
Value

Max
Value

Description+X PANEL V

0

Unsigned

0x00

0xFFF

+X PANEL V+Y PANEL V

1

Unsigned

0x00

0xFFF

+Y PANEL V+Z PANEL V

2

Unsigned

0x00

0xFFF

+Z PANEL V+X PANEL T

3

Unsigned

0x00

0xFFF

+X PANEL T+Y PANEL T

4

Unsigned

0x00

0xFFF

+Y PANEL T+Z PANEL T

5

Unsigned

0x00

0xFFF

+Z PANEL T

PSU PCB
Temperature

6

Unsigned

0x00

0xFFF

Temperature ofPSU card

Not used

7

-

-

-

-

Page 3 of 4

AMSAT Fox-1
IHU to PSU ICD
3.1.3 Measurements shall be made in relation to the 2.5 VDC internal voltage
reference for both ADS 7828 Devices.
3.1.4 For each Device the IHU shall poll each channel in channel number order.

Page 4 of 4

AMSAT Fox-1
IHU to Battery ICD
Date: September 17, 2013
Version: Version 2.03

AMSAT Fox-1
IHU to Battery Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the Battery (BATT1) System, as required per the AMSAT Fox-1 System
Requirements Specification document.
1.1

Document History
DATE

VERSION

SUMMARY

August 7, 2012

1.00

Initial version

November 7, 2012

1.01

Added BATT CPU Temperature

December 27, 2012

1.10

Add Battery Groups Temperature, change from
Bytes to Bits in Message Header Block,Message Data Block, Message Data

January 2, 2013

1.11

Field sizes back to bytes account I²C
specifications

February 7, 2013

1.12

Fix typo on 3.3.1.1

August 13, 2013

2.00

Updated for TI ADS 7828 replacing STM32L,
straight I2C query/answer from IHU now for 8channels of data.

August 22, 2013

2.01

Correct Battery Pair Temperature nomenclature

August 22, 2013

2.02

Update I²C speed to 10 kHz

September 17, 2013

2.03

Fix formatting error that hid requirement 2.2.2,
change type format to exclude code type, add
Min/Max Values

1.2 Document Scope
The purpose of this document is to specify the message format and the I²C bus hardware
operation for the communications between the IHU and the BATT1 as described in the
AMSAT Fox-1 System Requirements Specification.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification
4. Texas Instruments SBAS181C – NOVEMBER 2001 - REVISED MARCH 2005
Page 1 of 3

AMSAT Fox-1
IHU to Battery ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall be the I²C Master.
2.1.2 The BATT1 shall be the I²C Slave.
2.1.2.1 The IHU shall request the BATT1 to send the data for a specific channel.
2.1.2.2 The BATT1 shall send that specific channel data.
2.1.3 The IHU shall test for the presence of the BATT1 system.
2.1.3.1 If the presence of the BATT1 system is not detected, the IHU shall notpoll the system for data.
2.2

General Message Requirements

2.2.1 The IHU shall sample data at a rate sufficient to provide downlink telemetry
data at least every 15 seconds.
2.2.2 The ADS 7820 A/D converter shall always be commanded on (PD-0 bit =1).
2.2.3 The ADS 7820 Internal Reference shall always be commanded on (PD-1
bit = 1).
2.2.4 The ADS 7820 shall always be commanded for single-ended inputs.
2.3

I²C Bus Hardware Interface Requirements

2.3.1 The I²C Vdd shall be 3.0V.
2.3.2 The bus speed shall be Standard (10 kHz).
2.3.3 The BATT1 I²C 7 bit address shall be 0x48.

Page 2 of 3

AMSAT Fox-1
IHU to Battery ICD

3 Data Requirements
3.1

Measured Values

3.1.1 The measured data fields and their associated ADS 7828 channels shall be
as shown in Table 1.
Table 1

Field

Channel

Type

Min
Value

Max
Value

BATT I

0

Unsigned

0x00

0xFFF

BATT A V

1

Unsigned

0x00

0xFFF

BATT B V

2

Unsigned

0x00

0xFFF

BATT C V

3

Unsigned

0x00

0xFFF

BATT A T

4

Unsigned

0x00

0xFFF

BATT B T

5

Unsigned

0x00

0xFFF

BATT C T

6

Unsigned

0x00

0xFFF

BATT PCB
Temperature

7

Unsigned

0x00

0xFFF

Description
Battery current raw
value
Battery pair A voltage
raw value
Battery pair B voltage
raw value
Battery pair C voltage
raw value
Battery pair A
temperature raw value
Battery pair B
temperature raw value
Battery pair C
temperature raw value
Temperature of BATT
card

3.1.2 Measurements shall be in relation to the 2.5 VDC internal voltage referenceof the ADS 7828.
3.1.3 The IHU shall poll each channel in channel number order.

Page 3 of 3

AMSAT Fox-1A
IHU to Experiment 1 ICD
Date: September 17, 2013
Version: Version 1.06

AMSAT Fox-1A
IHU to Experiment 1 Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the Experiment System in Position 1 of the satellite, known as the Vanderbilt
University Vulcan Payload and abbreviated herein as EXP1.
1.1

Document History
DATE

VERSION

SUMMARY

March 3, 2013

1.00

Initial version

March 7, 2013

1.01

Correct use of I²C (1.2) and EXP1 (2.3.3)

March 31, 2013

1.02

Command Message CRC8 to include addressbyte, change to commands, modified figure 3,
deleted figure 4

March 31, 2013

1.03

Delete TYPE from message tables, add SET
TIME response return values

March 31, 2013

1.04

Add CMD_VERSION_ERR to Error Code table

April 2, 2013

1.05

Correct 6.5 Figure 3, remove 0x0005, 0x0201,
0x0210, 0x0281, 0x0300, and 0x0301
commands

September 17, 2013

1.06

Change type format to exclude code type, add
Min/Max Values

1.2 Document Scope
This document will specify the control of EXP1, the messaging format, and the I²C bus
hardware operation for the communications between the IHU and the EXP1.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification
4. Vanderbilt University Vulcan Payload Interface Control Document

Page 1 of 12

AMSAT Fox-1A
IHU to Experiment 1 ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall initiate a command to the EXP1.
2.1.2 The EXP1 shall send a reply to each IHU request.
2.1.3 Message bit order shall be Big Endian.
2.1.4 The IHU shall determine the action to be taken in the event of an invalid,
improper, or missing message from the EXP1.
2.1.5 The EXP1 shall take no action in the event of an invalid or improper
message from the IHU.
2.1.6 Message byte order shall be Big Endian.
2.2

General Message Requirements

2.2.1 Each message shall contain a header block.
2.2.2 Each message shall contain a packet error check (PEC) in the form of
CRC8.
2.2.2.1 The message address byte shall be included when calculating the
CRC8.
2.3

I²C 1 Bus Hardware Interface Requirements

2.3.1 The I²C Vdd shall be 3.0V.
2.3.2 The bus speed shall be Fast (400kbit/s).
2.3.3 The EXP1 I²C 7 bit address shall be 0x2A.

Page 2 of 12

AMSAT Fox-1A
IHU to Experiment 1 ICD

3 Experiment Operation
3.1

Experiment Power Control

3.1.1 The IHU shall exert control over the power state of the EXP1 by theExperiment Enable 1 pin on the satellite bus as shown in Table 1.
Table 1Pin State

Description

High

Power On Experiment

Low

Power Off Experiment

3.2

Experiment Power On Sequence

3.2.1 The IHU shall set and hold the Experiment Enable 1 pin HIGH.
3.2.2 The IHU shall not send any message to the EXP1 for a minimum of 100
milliseconds.
3.2.3 The IHU shall send a Set Time command to the EXP1.
3.3

Experiment Begin Operation Sequence

3.3.1 Upon completion of the Power On sequence the IHU shall send a Set Run
State Active command message to the EXP1.
3.4

Experiment Cease Operation Sequence

3.4.1 The IHU shall send a Set Run State Halt command message to the EXP1.
3.4.2 The IHU shall not send any message to the EXP1 for a minimum of 10000
milliseconds.
3.4.3 The IHU shall send a Set Run State Standby command message to the
EXP1.
3.5

Experiment Power Off Sequence

3.5.1 The IHU shall set and hold the Experiment Enable 1 pin LOW.

Page 3 of 12

AMSAT Fox-1A
IHU to Experiment 1 ICD

4 Message Content Requirements
4.1

Command Message

4.1.1 The message header block shall be constructed as shown in table 2.
4.1.2 The message header block shall be sent with each Command andResponse block.
Table 2

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

Message
Version2

Unsigned

0x01

0xFFFF

Message ICD
versionSoftware Build

2

Unsigned

0x01

0xFFFF

Software Buildversion

4.1.2.1 The Message Version shall be an integer representing the IHU to
EXP1 ICD document version number from which the message format
is derived, having the decimal point removed (e.g. version 1.03 would
be 103 decimal or 0x67).
4.1.2.2 The Software Build shall be an integer representing the software build
version number of the system originating the message, having any
decimal points removed (e.g. version 1.03 would be 103 decimal or0x67).
4.2

Command Message Block4.2.1 The command message block shall be constructed as shown in Table 3.
Table 3

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

COMMAND

2

Unsigned

0x00000x0280

Hexadecimal
Command

ARGUMENT

Variable

Unsigned--

Optional Arguments
As Required

The command message block shall contain one command in the COMMAND
COMMAND field as shown in Table 4.

Page 4 of 12

AMSAT Fox-1A
IHU to Experiment 1 ICD
Table 4

Command
Name

Size(Bytes)

Min
Value

Type

Max
Value

Description

0x0000No effect; response
undefined. Test for I²C
acknowledgement only.

Nop

2

Unsigned 0x0000

Echo

2

0x0001

Echo this byte stream

Resend2

Unsigned 0x0001
Unsigned 0x0002

0x0002

Resend last result

Get UID

2

Unsigned 0x0003

0x0003Controller 7 byte identifier

Get Status

2

Unsigned 0x0004

0x0004Controller statusindication

Get
Diagnostics

2

Unsigned 0x0006

0x0006

Self-check Diagnostic

Get
Telemetry

2

Unsigned 0x0010

0x0010Send telemetry data

Set RunState

2

Unsigned 0x0080

0x0080Enter specified Run State

Get RunState

2

Unsigned 0x0081

0x0081

Query current Run StateSet Time

2

Unsigned 0x0100

0x0100

Number of seconds sinceepoch

Get Time

2

Unsigned 0x0101

0x0101

Number of seconds sinceepoch

Get Data2

Unsigned 0x0280

0x0280Send (number of bytes)
data

4.2.3 The command message shall contain arguments for the Echo command,as shown in Table 5.
Table 5

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

ARGUMENT

4

Unsigned--

Data to beechoedPage 5 of 12

AMSAT Fox-1A
IHU to Experiment 1 ICD
4.2.4 The command message shall contain one argument for the Set Run State
command, as shown in Table 6.
Table 6Run State

Size(Bytes)

Type

Min
Value

Max
Value

Description

STANDBY

2

Unsigned

0x00010x0001Enter Standby StateACTIVE

2

Unsigned

0x00030x0003

Activate
Experiments

HALT

2

Unsigned

0x00040x0004

Terminate
Experiments

4.2.5 The command message shall contain arguments for the Set Timecommand, as shown in Table 7.
Table 7

Argument

Size(Bytes)

Type

Min
Value

Max
Value

IHU Reset
Counter

16

Unsigned

0x00

-

MET
Timestamp

32

Unsigned--

Description
Count of the number of
IHU resets from nonvolatile FRAM
MET timestamp (seconds
since last IHU reset)

4.2.6 The command message shall contain arguments for the Get Data
command, as shown in Table 8.
Table 8

Argument

Size(Bytes)

Type

Min
Value

Max
Value

Description

BYTES TO
SEND

2Unsigned

0x00

0xFFFF

Number of bytes tosend (1-256)

Page 6 of 12

AMSAT Fox-1A
IHU to Experiment 1 ICD
4.3

Response Message Block4.3.1 The response message block shall be constructed as shown in Table 9.
Table 9

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

RESERVED

1

Unsigned--

Reserved, ignore

ERROR
CODE

1

Unsigned

0x00000x0006

Response to
CommandLENGTH

2

Unsigned

0x00

0xFFFF

Length of Return
Value in Bytes

RETURN
VALUE

Variable

Variable--

Return Value

4.3.2 The Error Code shall contain one code as shown in table 10.
Table 10

Name

Size
(Bytes)

Type

Min
Value

Max
Value

Description

CMD_OK

1

Unsigned 0x0000

0x0000Commandinvokedsuccessfully

CMD_OP_ERR

1

Unsigned 0x0001

0x0001

Command notrecognized

CMD_FORMAT_ERR

1

Unsigned 0x0002

0x0002

Incorrect
commandargument
lengthCMD_RANGE_ERR

1

Unsigned 0x0003

0x0003

Argument(s)out of bounds

CMD_PEC_ERR

1

Unsigned 0x0004

0x0004

Error check(CRC)
mismatch

CMD_EXEC_ERR

1

Unsigned 0x0005

0x0005

Execution error

0X0006

HeaderMessage
Versionmismatch

CMD_VERSION_ERR

1

Unsigned 0x0006

Page 7 of 12

AMSAT Fox-1A
IHU to Experiment 1 ICD
4.3.3 The Status Flags for a GET STATUS response message shall be
represented as individual bit values of a 16 bit RETURN VALUE asshown in Table 11.
Table 11

Name

Bit
NumberDescription

REBOOTED0

1 = Experiment has rebooted – NOT USEDDATA READY

1

1 = Experiment data available

TIME REQUEST

2

1 = Request SET TIME

FAILED RUN STATE

3

1 = Failed the run state – NOT USEDCOMPLETED RUN STATE

4

1 = Completed the run state – NOT USEDRESERVED

5-15

Always 0

4.3.4 The response message to a Set Time command shall contain one of thevalues as shown in Table 12.
Table 12

Response
Name

Size(Bytes)

Type

Min
Value

Max
Value

SUCCESS

2

Signed0x00

0x00

Time Set
successfully

FAILURE

2

Signed0xFFFF

0xFFFFTime Set failed

Description

5 Message Integrity
5.1

Invalid Messages

5.1.1 If the PEC (CRC8) fails, the message shall be considered invalid.
5.1.2 If the Message Version does not match the message version in use forthe construction of messages on the receiving system, the message shallbe considered invalid.

Page 8 of 12

AMSAT Fox-1A
IHU to Experiment 1 ICD

6 Message Flow Diagrams
6.1

EXPERIMENT POWER ON SEQUENCE

IHU

EXP1
ASSERT EXPERIMENT 1 ENABLE

SET TIMERESPONSEIHU Handling

6.2

End

EXPERIMENT BEGIN OPERATION SEQUENCE

IHU

EXP1
SET RUN STATE: ACTIVERESPONSEIHU Handling

End

Page 9 of 12

AMSAT Fox-1A
IHU to Experiment 1 ICD
6.3

EXPERIMENT CEASE OPERATION SEQUENCE

IHU

EXP1
SET RUN STATE: HALTRESPONSESET RUN STATE: STANDBYRESPONSEIHU Handling

6.4

End

EXPERIMENT POWER OFF SEQUENCE

IHU

EXP1
DEASSERT EXPERIMENT 1 ENABLE

IHU Handling

End

Page 10 of 12

AMSAT Fox-1A
IHU to Experiment 1 ICD
6.5

SERVICING EXPERIMENT OPERATION

Figure 1

IHU

EXP1
GET STATUS

STATUS = REBOOTED or FAILED or COMPLETEDIHU HandlingEnd

Figure 2

IHU

EXP1
GET STATUS
STATUS = TIME REQUESTSET TIMERESPONSEIHU Handling

End

Page 11 of 12

AMSAT Fox-1A
IHU to Experiment 1 ICD

Figure 3

IHU

EXP1

GET DATADATAIHU Handling

End

Page 12 of 12

AMSAT Fox-1A
IHU to Experiment 4 ICD
Date: October 4, 2013
Version: Version 1.11

AMSAT Fox-1A
IHU to Experiment 4 Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the Experiment System in Position 4 of the satellite, known as the VT Camera
Experiment and abbreviated herein as EXP4.
1.1

Document History
DATE

VERSION

SUMMARY

January 24, 2013

1.00

Initial version

February 20, 2013

1.01

Specify byte order as little endian

May 21, 2013

1.10

Update data TYPE names

October 4, 2013

1.11

Change type format to exclude code type, add
Min/Max Values, add thermistor circuit

1.2 Document Scope
This document will specify the control of EXP4, the messaging format, and the serial bus
hardware operation for the communications between the IHU and the EXP4.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification

Page 1 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall initiate a command to the EXP4.
2.1.2 The EXP4 shall send a reply to each IHU request.
2.1.3 Message bit order shall be Little Endian.
2.1.4 The IHU shall determine the action to be taken in the event of an invalid,
improper, or missing message from the EXP4.
2.1.5 The EXP4 shall take no action in the event of an invalid or improper
message from the IHU.
2.1.6 Message byte order shall be Little Endian.
2.2

General Message Requirements

2.2.1 Each message shall contain a header block.
2.2.2 Each message shall contain one command, one reply, or one data block.
2.3

Serial Bus Hardware Interface Requirements

2.3.1 The bus levels shall be 3.0V.
2.3.2 The bus data speed shall be 38400 bit/s.
2.3.3 The serial bus communication shall be asynchronous.
2.3.4 The number of data bits shall be 8.
2.3.5 The number of stop bits shall be 1.
2.3.6 There shall be no parity bit.

Page 2 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

3 Experiment Operation
3.1

Experiment Power Control

3.1.1 The IHU shall exert control over the power state of the EXP4 by theExperiment Enable 4 pin on the satellite bus as shown in Table 1.
Table 1Pin State

Description

High

Power On Experiment

Low

Power Off Experiment3.1.2 Upon signaling Power On to the EXP4, the IHU shall not send any
message to the EXP4 for a minimum of 100 milliseconds.
3.2

Experiment Operation Sequence

3.2.1 Upon Power On the IHU shall determine the state of the EXP4 by sending
an Is Camera Ready command message.
3.2.2 The IHU shall not send a Transmit Data Block command message prior toreceiving a Camera Ready reply message from the EXP4.

4 Message Content Requirements
4.1

Message Header Block4.1.1 The message header block shall be constructed as shown in table 2.
4.1.2 The message header block shall be sent with each Command, Reply, andData block.
Table 2

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

Message
Version2

Unsigned

0x01

0xFFFF

Message ICD
versionSoftware Build

2

Unsigned

0x01

0xFFFF

Software Buildversion

4.1.2.1 The Message Version shall be an integer representing the IHU to
EXP4 ICD document version number from which the message format
is derived, having the decimal point removed (e.g. version 1.03 would
be 103 decimal or 0x67).
Page 3 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

4.1.2.2 The Software Build shall be an integer representing the software build
version number of the system originating the message, having any
decimal points removed (e.g. version 1.03 would be 103 decimal or0x67).
4.2

Command Message Block4.2.1 The command message block shall be constructed as shown in Table 3.
Table 3Field

Size (Bytes)

Type

COMMAND

2Alpha

Min Value Max Value Description
RR
TT

RR
TT

Command4.2.2 The command message block shall contain one command in the
COMMAND field as shown in Table 4.
Table 4

Command

Description

RR

Is Camera Ready?

TT

Transmit Data Block

4.3

Reply Message Block4.3.1 The reply message block shall be constructed as shown in Table 5.
Table 5

Field

Size (Bytes)

Type

REPLY

2

Alpha

Min Value Max Value Description
NN
YY
FF

NN
YY
FF

Reply

4.3.2 The reply message block shall contain one reply in the REPLY field asshown in table 6.

Page 4 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD
Table 6

Command

Description

NN

Camera Not Ready

YY

Camera ReadyFF

Camera Failed

Page 5 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

4.4

Message Data Block4.4.1 The message data block shall be constructed as shown in Table 7.
Table 7

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

DESCRIPTOR

2

Unsigned--

Line ID and Payload
LengthPAYLOAD

Variable

Unsigned--

Array of (Payload
Length) bytes

CHKSUM

2

Unsigned--

16 bit accumulator sum
of bytes in HEADER
and PAYLOAD

4.4.2 The bits of the message data block DESCRIPTOR bytes shall be
constructed as shown in Table 8.
Table 8

Field

Size
(Bits)

Type

Min
Value

Max
Value

Description

Line ID

6

Unsigned

0x01

0x3C

640 x 8 pixel picture line
number (1 is top, 60 isbottom)PayloadLength10

Unsigned

0x01

0x3FF

Total number of bytes in
PAYLOAD

4.4.2.1 The Line ID shall compose the 6 MSB and the Payload Length shallcompose the 10 LSB.

5 Message Integrity
5.1

Invalid Messages

5.1.1 If the DATA block CHKSUM fails, the message shall be consideredinvalid.
5.1.2 If the Message Version does not match the message version in use forthe construction of messages on the receiving system, the message shallbe considered invalid.

Page 6 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

6 Message Flow Diagrams
6.1

RR COMMAND

IHU

EXP4
COMMAND: RR

REPLY: NN, YY, OR FF

IHU Handling

End

Page 7 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD
6.2

TT COMMAND

IHU

EXP4
COMMAND: TT

MESSAGE DATA BLOCK OR REPLY:FF

IHU HandlingEnd

7 Experiment Card Temperature Telemetry
7.1

Thermistor

7.1.1 The experiment shall provide a DC voltage derived from a thermistor
circuit mounted on the experiment card, to the IHU via the system bus.
7.1.2 The voltage shall be the raw voltage value of the thermistor circuit.
Note: AMSAT shall provide the schematic and BOM for the thermistor circuit.

Page 8 of 8

AMSAT Fox-1A
Downlink Specification
Date: August 26, 2013
Version: Version 1.41

AMSAT Fox-1A
Downlink Specification
1 Introduction
This document specifies downlink frame formats for the Fox-1A telemetry andexperiment telemetry. This specification includes the both slow and high speed formats.
Document History
DATE

VERSION

SUMMARY

April 25, 2013

1.01

Remove TX PA Temperature and TX Osc
Temperature, add TX Temperature

May 21, 2013

1.2

High speed downlink details added

May 27, 2013

1.3

Remove Radiation Experiment Telemetry
Frame, resize Radiation Experiment Data
Frame, renumber Payload Types, added Slow
Speed Link Layer Transmission Scheduling,changed Reset Count to 16 bits

June 6, 2013

1.31

Reduce BATT CPU, PSU CPU, IHU CPU, TX
Temp, RX Osc Temp from 12 to 8 bit value, add
IHU Error Data field to Telemetry Minimum
Values Frame

June 26, 2013

1.32

Correct Payload Type numbers in Table 6

August 13, 2013

1.40

Changes due to new BATT telemetry values,
delete Type 4 from idle telemetry

August 26, 2013

1.41

Change Receiver Osc Temperature to Receiver
Card Temperature, remove TOTAL MPPT I,
update 2.2.9.1 and 2.2.9.1.1 to reflect variable
size of Radiation Experiment Data available

1.1 Document Scope
The purpose of this document is to specify the downlink protocol on the AMSAT Fox-1A
spacecraft.
1.2 References
1. Fox1 IHU to RF ICD
2. Fox1 IHU to Battery ICD
3. Fox1 IHU to PSU ICD
4. Fox1 IHU to Attitude Determination Experiment ICD
Page 1 of 14

AMSAT Fox-1A
Downlink Specification
5. Fox1 IHU Software Architecture Specification
6. Fox1 IHU to Experiment 1 ICD
7. Fox1 IHU to Experiment 4 ICD
1.3 Definitions
1.3.1 Slow Speed Downlink – Data transmitted at approximately 100 bits per
second in the audio portion below 300 Hz simultaneous with thetransponder audio.
1.3.2 High Speed Downlink – Data transmitted at approximately 9600 bits per
second using the entire downlink audio passband.
1.3.3 Spacecraft Telemetry – Downlink data containing specific information
about spacecraft systems and health as defined in the System
Requirements and related documents.
1.3.4 Experiment Telemetry – Downlink data containing specific information
about the various experiment platforms flown on the satellite.
1.3.5 Frame – A defined set of data with a specific overall size comprised offields of a specific bit or byte length.

Page 2 of 14

AMSAT Fox-1A
Downlink Specification

2 Protocol Structure
2.1 Physical Layer
2.1.1 The physical layer includes options for slow-speed and high speed
operation.
2.1.2 Slow speed operation uses frequency-shift keying and is transmitted in
the sub-audible part of the audio downlink below 300 Hz. It may betransmitted simultaneously with voice or other audio signals. The detailsof the physical layer are shown in Table 1.
Table 1

Bit Rate
Scrambler
Spectral efficiency
Modulation type
Signal bandwidth
FSK Deviation
Spectral Mask
RF Channel Bandwidth

100 bps
TBR
1 bps/Hz
Non-coherent Frequency Shift Keying (FSK)
10 Hz to 200 Hz (-3 dB points)
500 Hz-20 dB at 300 Hz
1200 Hz

2.1.3 High speed operation uses frequency-shift keying and is transmittedusing the entire RF downlink bandwidth. The details of the physical layer
are shown in Table 2. Note that this is the same as the G3RUH modem.
Table 2

Bit Rate
Scrambler
Spectral efficiency
Modulation type
Signal bandwidth
FSK Deviation
Spectral Mask
RF Channel Bandwidth

9600 bps
17 bit maximal length LFSR
2 bps/Hz
non-coherent frequency shift keying (FSK)
10 Hz to 4800 Hz (-3 dB points)
3 kHz-60 dB at 7500 Hz
20 kHz

2.2 Link Layer
2.2.1 The link layer protocol provides multiplexing, packet identification andforward error correction.
2.2.2 The link layer shall include a header and a trailer surrounding theapplications layer payload to form data packets as shown in Table 3.
Table 3Header

Applications Payload
Page 3 of 14

TrailerAMSAT Fox-1A
Downlink Specification
2.2.3 The applications payload layer shall include satellite telemetry,experiment telemetry, high speed data, and debug frames.
2.2.4 Debug frames may be used during ground testing but shall not betransmitted for flight.
2.2.5 Bits shall be transmitted in the order of least significant bit first.
2.2.6 Bytes shall be transmitted in Little Endian order.
2.2.7 The Slow Speed link layer header structure shall be as shown in Table 4.
Table 4Field

Size (Bits)

Fox ID

3

Reset
Count

16

Uptime

25

Type

4

Type
Unsignedchar
Unsigned
short
Unsignedint
Unsigned
char

Value
0x01
Variable
Variable
Variable

Description
0x01 specifies Fox-1A (each Fox
satellite will have a unique ID)
Total number of times IHU has reset
since initial on-orbit startup
This is the IHU uptime in seconds
since the last reset
This identifies the payload type2.2.7.1 Payload type shall be as specified in the application layer payload
data.
2.2.7.2 Each Slow Speed link layer structure shall contain only one payload
type.
2.2.8 The High Speed link layer header structure is shown in Table 5.
Table 5

Field

Size (Bits)

Fox ID

3

Reset
Count

14

Uptime25

Type
Unsignedchar
Unsigned
short
Unsigned
int

Value
0x01
Variable
Variable

Page 4 of 14

Description
0x01 specifies Fox-1A (each Fox
satellite will have a unique ID)
Total number of times IHU has reset
since initial on-orbit startup
This is the IHU uptime in seconds
since the last resetAMSAT Fox-1A
Downlink Specification
2.2.9 The High Speed link layer applications payload shall contain data fromall payload types, as shown in table 6.
Table 6

Payload Type

Size (Bytes)

Description

160Real-Time Telemetry Frame

2

60

Telemetry Maximum Values Frame

3

60

Telemetry Minimum Values Frame

5

Variable1 - 4300

Camera JPEG Data Frame

4

58

Radiation Experiment High Speed Data Frame

2.2.9.1 A varying number of Radiation Experiment Data bytes shall be sent tofill the applications payload size to a total of 4600 bytes if the payload
type 5 data is less than 4300 bytes.
2.2.9.1.1 When less than a sufficient number of bytes to contain a usefuldata frame remain to fill to 4600 bytes, the remaining bytes shallbe filled with zeros.
2.2.9.2 Real-Time Telemetry Frame, Telemetry Maximum Values Frame, andTelemetry Minimum Values Frame data shall be padded with zeros toequal 60 bytes length each.
2.2.10 Forward error correction (FEC) code words shall be sent in the link
layer trailer. The FEC shall be a Reed Solomon RS (TBR) code. (Thisprovides TBR error detection and correction capability.)

Page 5 of 14

AMSAT Fox-1A
Downlink Specification

3 Slow Speed Link Layer Transmission Scheduling
3.1 While IHU PTT is asserted Payload Types contained in the Link Layer
Applications Payload shall rotate, changing type with each successive
link layer transmitted, in the following order:
x
x
x
x
x
x
x
x
x
x
x
x

Type 1
Type 4
Type 1
Type 4
Type 1
Type 2Type 4
Type 1
Type 4
Type 1
Type 4
Type 33.1.1 The above order shall be repeated so long as IHU PTT is asserted.
3.2 While beacon message is sent during idle timer expired the Payload
Types contained in the Link Layer Applications Payload shall betransmitted only once in the following order:xType 1Page 6 of 14

AMSAT Fox-1A
Downlink Specification

4 Application Layer Payload Data
4.1 Payload Type 1 - Real-Time Telemetry Frame (Size = 334 bits)
Table 7

Field

Size (Bits)

BATT A V

12BATT B V

12BATT C V

12BATT A T

12

BATT B T

12BATT C T

12

TOTAL
BATT IBATT Board
Temperature

12
8+X PANEL V

12-X PANEL V

12+Y PANEL V

12-Y PANEL V

12+Z PANEL V

12-Z PANEL V

12+X PANEL T

12-X PANEL T

12+Y PANEL T

12-Y PANEL T

12+Z PANEL T

12- Z PANEL T

12

Type
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Signedshort
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short

Value

Description

Variable

Battery pair A voltage raw value

Variable

Battery pair B voltage raw value

Variable

Battery pair C voltage raw value

Variable

Battery pair A temperature raw value

Variable

Battery pair B temperature raw value

Variable

Battery pair C temperature raw value

Variable

Total Battery DC current raw value

Variable

PC Board Temperature of BATT

Variable+X solar panel voltage raw value

Variable-X solar panel voltage raw value

Variable+Y solar panel voltage raw value

Variable-Y solar panel voltage raw value

Variable+Z solar panel voltage raw value

Variable-Z solar panel voltage raw value

Variable+X solar panel temperature raw value

Variable-X solar panel temperature raw value

Variable+Y solar panel temperature raw value

Variable-Y solar panel temperature raw value

Variable+Z solar panel temperature raw value

Variable-Z solar panel temperature raw value

Page 7 of 14

AMSAT Fox-1A
Downlink Specification
Field

Size (Bits)

PSU CPU
Temperature

8

SPIN

12

TX PA
Current
TX
Temperature
RX
Temperature
IHU CPU
Temperature
Antenna
DeploySensors
Satellite X
Axis Angular
Velocity
Satellite Y
Axis Angular
Velocity
Satellite Z
Axis Angular
Velocity
Experiment
FailureIndication

12
8
8
8
2

Type
Unsigned
short
Signedchar
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
2x
Unsignedchar: 1

Value

Description

Variable

CPU Temperature of PSU

Variable

PSU calculated spin rate RPM

Variable

Transmit power amplifier current

Variable

Transmitter card temperature

Variable

Receiver card temperature

Variable

CPU Temperature of IHU

Variable

Bit 0 is RCV Bit 1 is XMT
0 = stowed 1 = deployed

12

Unsigned
short

Variable

Raw Angle

12

Unsigned
short

Variable

Raw Angle

12

Unsigned
short

Variable

Raw Angle

4

4xUnsignedchar: 1

Variable

Bit 0 is Experiment 1
Bit 1 is Experiment 2 (N/A on Fox-1A)
Bit 2 is Experiment 3 (N/A on Fox-1A)
Bit 3 is Experiment 4
State: 0 = Working, 1 = Failed

Page 8 of 14

AMSAT Fox-1A
Downlink Specification
4.2 Payload Type 2 - Telemetry Maximum Values Frame (Size = 342 bits)
Table 8Field

Size (Bits)

BATT A V

12BATT B V

12BATT C V

12BATT A T

12

BATT B T

12BATT C T

12

TOTAL
BATT IBATT Board
Temperature

12
8+X PANEL V

12-X PANEL V

12+Y PANEL V

12-Y PANEL V

12+Z PANEL V

12-Z PANEL V

12+X PANEL T

12-X PANEL T

12+Y PANEL T

12-Y PANEL T

12+Z PANEL T

12- Z PANEL T

12

Type
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Signedshort
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short

Value

Description

Variable

Battery pair A high voltage raw value

Variable

Battery pair B high voltage raw value

Variable

Battery pair C high voltage raw value

Variable
Variable
Variable

Battery pair A high temperature raw
value
Battery pair B high temperature raw
value
Battery pair C high temperature raw
value

Variable

Battery DC high current raw value

VariableHigh PC Board Temperature of BATT

Variable+X solar panel high voltage raw value

Variable-X solar panel high voltage raw value

Variable+Y solar panel high voltage raw value

Variable-Y solar panel high voltage raw value

Variable+Z solar panel high voltage raw value

Variable-Z solar panel high voltage raw value

Variable
Variable
Variable
Variable
Variable
Variable

Page 9 of 14+X solar panel high temperature raw
value-X solar panel high temperature raw
value+Y solar panel high temperature raw
value-Y solar panel high temperature raw
value+Z solar panel high temperature raw
value-Z solar panel high temperature raw
value

AMSAT Fox-1A
Downlink Specification
Field

Size (Bits)

PSU CPU
Temperature

8

SPIN

12

TX PA
Current
TX
Temperature
RX
Temperature
IHU CPU
Temperature(No Value)
Satellite X
Axis Angular
Velocity
Satellite Y
Axis Angular
Velocity
Satellite Z
Axis Angular
Velocity
MRAM Error
Count

12
8
8
8
2

Type
Unsigned
short
Signedchar
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
char

Value

Description

VariableHigh CPU Temperature of PSU

Variable

Highest PSU calculated spin rate

Variable

Transmit power amplifier high current

Variable

Transmitter card high temperature

Variable

Receiver card high temperature

VariableHigh CPU Temperature of IHU

Fixed

0x00 filler

12

Unsigned
short

Variable

Highest Raw Angle

12

Unsigned
short

Variable

Highest Raw Angle

12

Unsigned
short

Variable

Highest Raw Angle

12

Unsigned
short

Variable

Total MRAM Errors

Page 10 of 14

AMSAT Fox-1A
Downlink Specification
4.3 Payload Type 3 - Telemetry Minimum Values Frame (Size = 362 bits)
Table 9Field

Size (Bits)

BATT A V

12BATT B V

12BATT C V

12BATT A T

12

BATT B T

12BATT C T

12

TOTAL
BATT IBATT Board
Temperature

12
8+X PANEL V

12-X PANEL V

12+Y PANEL V

12-Y PANEL V

12+Z PANEL V

12-Z PANEL V

12+X PANEL T

12-X PANEL T

12+Y PANEL T

12-Y PANEL T

12+Z PANEL T

12- Z PANEL T

12

Type
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Signedshort
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short

Value

Description

Variable

Battery pair A low voltage raw value

Variable

Battery pair B low voltage raw value

Variable

Battery pair C low voltage raw value

Variable
Variable
Variable

Battery pair A low temperature raw
value
Battery pair B low temperature raw
value
Battery pair C low temperature raw
value

Variable

Battery DC low current raw value

VariableHigh PC Board Temperature of BATT

Variable+X solar panel low voltage raw value

Variable-X solar panel low voltage raw value

Variable+Y solar panel low voltage raw value

Variable-Y solar panel low voltage raw value

Variable+Z solar panel low voltage raw value

Variable-Z solar panel low voltage raw value

Variable
Variable
Variable
Variable
Variable
Variable

Page 11 of 14+X solar panel low temperature raw
value-X solar panel low temperature raw
value+Y solar panel low temperature raw
value-Y solar panel low temperature raw
value+Z solar panel low temperature raw
value-Z solar panel low temperature raw
value

AMSAT Fox-1A
Downlink Specification
Field

Size (Bits)

PSU CPU
Temperature

8

SPIN

12

TX PA
Current
TX
Temperature
RX
Temperature
IHU CPU
Temperature(No Value)
Satellite X
Axis Angular
Velocity
Satellite Y
Axis Angular
Velocity
Satellite Z
Axis Angular
VelocityIHU Error
Data

12
8
8
8
2

Type
Unsigned
short
Signedchar
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
short
Unsigned
char

Value

Description

Variable

Low CPU Temperature of PSU

Variable

Lowest PSU calculated spin rate

Variable

Transmit power amplifier low current

Variable

Transmitter card low temperature

Variable

Receiver card low temperature

Variable

Low CPU Temperature of IHU

Fixed

0x00 filler

12

Unsigned
short

Variable

Lowest Raw Angle

12

Unsigned
short

Variable

Lowest Raw Angle

12

Unsigned
short

Variable

Lowest Raw Angle

20

Unsigned
int

Variable

Data on Last IHU Error

Page 12 of 14

AMSAT Fox-1A
Downlink Specification
4.4 Payload Type 4 - Radiation Experiment Data Frame (Size = 464 bits)
Table 10Field

Size (Bytes)

Value

Description

Data

58

Variable

Experiment 1 Packets

4.5 Payload Type 5 - Camera JPEG Data Frame (Size is variable)
Table 11

Field

Size (Bytes)

Type

Value

Description

Picture Lines

4300

Unsigned
int

Variable

Picture Data1

1

See section 4 for Picture Data Structure

Page 13 of 14

AMSAT Fox-1A
Downlink Specification

5 Picture Data Structure
5.1 Scan Line Segment
Table 12Field

Size (Bits)

Type

Value

Description

PictureCounter4

Unsignedchar

Variable

0x00 through 0x0F, picture countindicator

Scan Line
Number5

Unsignedchar

Variable

0x00 through 0x3B, 0x00 = top scanline

Scan Line
Length10

Unsigned
short

Variable0x001 through 0x3FF, count of bytes inthe scan line

Scan Line
Data

Variable

Unsigned
int

Variable(Fragment Length) Scan Line Data

End of JPEG
Data

8

Unsigned
char

0xAA

Indicates end of Picture Data for use in
Applications Payload construction

5.1.1 Total Scan Line Segment data size for one Applications Payload frame
including end of JPEG data indicator byte shall not exceed 4300 bytes.

Page 14 of 14

AMSAT Fox-1
IHU Software Architecture Specification
Date: January 1, 2013
Version: draft H

AMSAT Fox-1
IHU Software Architecture Specification
1 Introduction
This software architecture document is a specification of the desired behavior of the IHUsoftware and guidance on an overall structure for the implementation.
1.1

Document History
DATE

VERSION

SUMMARY

1.2 Document Notes
Process specifications are described in this document using a "C-like" psuedocode
syntax. This is intended as high-level descriptions of the procedures and not compilable
code.
1.3

References
1. Concept of Operations, Version 1.03, OCT 19, 2011
2. System Requirements Specification, Version 1.2, OCT 17, 2012
3. IHU to Battery Interface Control Document, Version 1.01, November 7, 2012
4. IHU to PSU Interface Control Document, Version 1.04, November 7, 2012
5. Radiation Experiment Interface Control Document ???
6. Camera Interface Control Document ??
7. Downlink Protocol Specification ???

Page 1 of 19

AMSAT Fox-1
IHU Software Architecture Specification

2 Processing Environment
2.1 Microcontroller
The IHU software will run on an STMicroelectronics STM32L151VBT microcontroller.
The CPU is an ARM® Cortex™-M3 processor with a maximum clock speed of 32 MHz.
This is a 32-bit processor and it provides up to 33 MIPS of processing power. The
microcontroller includes 128K bytes of FLASH program memory, 4K bytes of nonvolatile EEPROM and 16K bytes of RAM.
2.2 MRAMThe IHU card includes an Everspin Technologies MR25H10 MRAM. This is a 128K
byte, non-volatile, read-write memory. The MR25H10 is highly tolerant of spaceradiation and is expected to be error-free during on-orbit operation. However, it isconnected to the microcontroller through an SPI bus interface which may be sensitive tospace radiation effects. Therefore, as a minimum, a single-bit-error detection scheme
should be used to detect errors that might be induced during SPI transfers. This can beeasily accommodated with a 16-bit checksum of 8-bit bytes for each data structure stored
in the memory. Writes to the MRAM should be immediately followed by a read-verify
operation to insure that the write was successful. A retry scheme should be used to handle
detected errors.
2.3 MicroSD Card
The IHU has the capability of hosting a microSD FLASH memory card. This is notexpected to be used for the initial Fox-1 satellite mission but is available for softwaredevelopment if desired.
2.4 I/O Interfaces
The IHU microcontroller includes the following types of on-chip I/O interfaces:
Type
A/D
D/A
I2C
GPI
GPO
Serial-I
Serial-O
SPI

Description
Analog to Digital Converter (input)
Digital to Analog Converter (output)
I2C busGeneral Purpose IO (used as input)
General Purpose IO (used as output)
Asynchronous serial input
Asynchronous serial output
SPI BusThe above "Type" codes are used in the next section to indicate how peripheral device
signals are interfaced with the IHU microcontroller.

Page 2 of 19

AMSAT Fox-1
IHU Software Architecture Specification

3 Peripheral Devices
This section describes the IHU peripherals and their interfaces to the microcontroller. See
the IHU card documentation for the specific port and pin information. It would probably
be very helpful to create a cross-reference between the Fox-1 bus signals and the STM32
port/pins.
3.1 MEMS Gyroscopes
The IHU card includes a pair of STMicroelectronics, LPY403AL, 2-axis MEMS
gyroscopes. They are physically arranged so that 3-axis of angular velocity can bemeasured. The GPIO outputs on the microcontroller are used to control the operation of
the gyros and the gyro outputs drive A/D inputs on the microcontroller.
The interface is as follows:
Name
Gyro HP
Gyro ST
Gyro_Vref_1
Gyro_Vref_2
Gyro_X_1
Gyro_Z_1
Gyro_X_2
Gyro_Z_2

Type
GPO
GPO
A/D
A/D
A/D
A/D
A/D
A/D

Note that the Gyro_Z_2 channel provides duplicate information and is not used.
Looking down at the top (+Z) of the satellite, a Gyro_Z_1 voltage above theGyro_Vref_1 voltage indicates a counter-clockwise rotation about the satellite's Z axis.
Looking straight at the +Y solar panel of the satellite, a Gyro_X_1 voltage above theGyro_Vref_1 voltage indicates a counter-clockwise rotation about the satellite's Y axis.
Looking straight at the +X solar panel of the satellite, a Gyro_X_2 voltage above theGyro_Vref_2 voltage indicates a clockwise rotation about the satellite's X axis. This is
opposite from the other axis and must be multiplied by -1 to be consistent when reported.
Refer to the LPY403AL spec sheet to understand how to test (for diagnostics) andoperate the MEMS gyro devices.

Page 3 of 19

AMSAT Fox-1
IHU Software Architecture Specification
3.2 Antenna Deployer Control
These signals activate the antenna deployment mechanisms and sense the deployment
status. The precise sequencing and operation of these signals is TBD.
Name
TX Antenna Sensor
RX Antenna Sensor
TX Antenna Deploy
RX Antenna Deploy

Type
GPI
GPI
GPO
GPO

3.3 Radio Control
These are the signals used to operate the RF up and down links.
Name
Command Mode
IHU_PTTIHU_Audio_1_Out
IHU_Audio_2_Out *RX_CD *RX PTT *Rx_Audio_1
Rx_Audio_2 *

Type
GPO
GPO
D/A
D/A
GPI
GPI
A/D
A/D

* For Fox-1, the IHU_Audio_2_Out, RX_CD, RX_PTT and Rx_Audio_2 signals are notused by the IHU software.
3.4 IHU Card Telemetry
These are the telemetry parameters from sensors on the IHU card.
Name
Type
IHU CPU Temperature A/D
3.5 External Watchdog Timer
In addition to the STM32 internal watchdog timer, the IHU card has an external
watchdog timer. The IHU software must pulse the "Watchdog" lead at least once persecond. Failure to do this will cause the IHU to be power-cycled.
Name
Type
Watchdog GPO

Page 4 of 19

AMSAT Fox-1
IHU Software Architecture Specification
3.6 Hardware Command Decoder
There is a 4-bit, hardware command decoder on the RF Rx card. The 4 output bits and adata valid strobe are available on the IHU card on GPIO leads. The decoder output bits 811 are latched. The data valid strobe is a rising edge and is not latched. At satellite powerup, all signals will be 0.
OutputRX Command Data11
RX Command Data10
RX Command Data9
RX Command Data8
RX Command Strobe

Type
GPI
GPI
GPI
GPI
GPI

The most significant bit (Data 11) is used to inhibit the RF transmitter. The second mostsignificant bit (Data 10) is used to inhibit the IHU (i.e. power off.) These are
implemented in hardware and operate without any software intervention. The commands
are coded as follows:
Bit Pattern
1xxx
0xxx
x1xx
x0xx
xx00
xx01
xx10
xx11

Command
Inhibit TX
Enable TX
Inhibit IHU (power off)
Enable IHU (power on)
Go To Transponder Mode
Go To Data Mode
Clear Telemetry Min/Max data
Send Test Message

3.7 RF System Telemetry
These are analog sensors on the RF cards that feed A/D inputs on the STM32.
Parameter
TX PA Current
TX PA Temperature
TX Osc Temperature
RX Osc Temperature

Type
A/D
A/D
A/D
A/D

Page 5 of 19

AMSAT Fox-1
IHU Software Architecture Specification
3.8 Battery Card Telemetry
These data elements come from the Battery card via an I2C interface that is shared with
the PSU card. See the IHU to Battery Interface Control Document for more details.
Parameter
Battery Cell 1 Volts
Battery Cell 2 Volts
Battery Cell 3 Volts
Battery Cell 4 Volts
Battery Cell 5 Volts
Battery Cell 6 Volts
Battery Pair 1 Temperature
Battery Pair 2 Temperature
Battery Pair 3 Temperature
Battery Card Current*
BAT CPU Temperature*Note: Total current into (charge) or out of (discharge) the card.
3.9 PSU Card Telemetry
These parameters come from the PSU card via an I2C interface that is shared with theBattery card. See the IHU to PSU Interface Control Document for more details.
Parameter+X Solar Panel Volts-X Solar Panel Volts+Y Solar Panel Volts-Y Solar Panel Volts+Z Solar Panel Volts-Z Solar Panel Volts+X Solar Panel Temperature-X Solar Panel Temperature+Y Solar Panel Temperature-Y Solar Panel Temperature+Z Solar Panel Temperature-Z Solar Panel Temperature
Satellite Spin Rate*
Total Output Current
PSU CPU Temperature*Note: the satellite spin rate is calculated on the PSU card from the solar panel voltages
and is only meaningful when the satellite is in sunlight.
Page 6 of 19

AMSAT Fox-1
IHU Software Architecture Specification
3.10 USB Umbilical PortThe umbilical port is functionally a USB port. The USB port can provide power to thesatellite avionics and can be used to charge the satellite batteries. Since battery charging
will exceed the standard USB current capability, a special power adapter will be used
when charging the batteries. A GPIO input lead will indicate that the USB port isproviding power to the satellite.
To the USB host, the satellite will look like a COM port and will allow use of thestandard host USB COM driver. The intention is that the satellite can be easily used with
common terminal emulation programs such as PuTTY. This port is used by the
Diagnostics Subsystem that is described later in the document.
3.11 Debug PortThis is a serial port available for SW development use. It is not needed or used for the
mission. It is expected that a call to a debug "printf()" would direct the output string to
the debug port. It is expected this port would use asynchronous ASCII 8 Data bits, noparity, 1 stop bit, 19.2 k bps. As an alternative, the Umbilical port could be enhanced todisplay software debug messages rather than use a dedicated serial port. This port could
be used for a debugger such as GDB if desired.
3.12 Radiation Experiment
Power to the radiation experiment cards is controlled via a GPIO output that drives the"Experiment Enable 1" bus signal.
An I2C bus is used to get the radiation experiment data. The specifics of this interface aredefined in the Fox-1 Experiment Interface Control Document.
3.13 Camera
Power to the camera card is controlled via a GPIO output that drives the "Experiment
Enable 4" bus signal.
A serial port is used to send commands to the camera and to get the camera image data.
The specifics of this interface are defined in the Fox-1 Camera Interface Control
Document.

Page 7 of 19

AMSAT Fox-1
IHU Software Architecture Specification

4 CPU Start Up SequenceThis is the sequence of events after a CPU reset or at power up.
// Run Power On Self Test (POST)// Check the program FLASH and run a CPU test// Remember to pulse the external watchdog timer!
Run POST;
if (POST Failed) {halt and let external watchdog timer fire to try again}// POST passed// See if we need to deploy the antennas
if (Umbilical Port is providing power) {break;// do NOT deploy antennas!
}
else if (Both antennas are already deployed) {break;// no need to deploy antennas}
else if (One antenna is already deployed) {Deploy remaining antenna;
break;}
else {// Just released from P-POD// Antennas not deployed
wait for 45 minutes;// remember to pulse Watchdog
Deploy RX antenna;
Deploy TX antenna;
break;}
increment IHU Reset Count in MRAM;
set Command Mode to HIGH;
boot up system;

Page 8 of 19

AMSAT Fox-1
IHU Software Architecture Specification

5 Application Software Data Flow Diagram
This shows the application software subsystems and their interfaces after the start up
sequence has been executed (i.e. after system boot up.) The required functionality of eachsubsystem is specified in this section.

Camera(Serial)

CameraSubsystem
1.0

CameraData

Radiation
Experiment(I2C)

Radiation
Experiment
Subsystem
2.0

Experiment
Data

SoftwareDebug
Subsystem
3.0

Debug
Port
(Serial)

Debug
Data

Low Battery
Co mmunications
Subsystem
8.0

Telemetry
Data

IHU Telem
Telemetry
Subsystem
5.0

PSU Telem

Test
Co mmandClear
Min/Max

BAT Telem

TRANSPONDER
or DATA mode
to all Subsystems

Radio
ControlInterface

FutureUplinkCo mmands

Co mmandSubsystem
6.0

Satellite
OperatingMode

HardwareCo mmand
DecoderLocal
Co mmands
Telemetry,camera andExperiment
Data

Umbilical
Function
Co mmands

Diagnostic
Subsystem
7.0

Force
Reset

Page 9 of 19

SanityCheck
Subsystem
4.0

USB
Umbilical
Port

External
Watchdog

AMSAT Fox-1
IHU Software Architecture Specification
5.1 Camera Subsystem (1.0)
This subsystem runs the camera. The Camera is only used in DATA mode.
// Camera Processing// Satellite in DATA mode
Turn ON power to Camera Card;
Initialize Camera parameters;
while (Satellite is in DATA mode) {Tell Camera to take a snapshot;
while( Camera has data to send) {Get data from Camera;Store in Camera Data Buffer}
Send Camera Data to Communications Subsystem;}// If Satellite switched to TRANSPONDER mode
Turn Camera card OFF;
Clear Camera Data Buffer;
Do nothing until satellite switches to DATA mode;
5.2 Radiation Experiment Subsystem (2.0)
This subsystem is responsible for running the experiment, collecting the experiment data ,putting the experiment data into the Experiment Data Buffer and sending it to theCommunications Subsystem. The experiment must be turned off and processing stopped
if the Low Battery indication is received from the Telemetry subsystem.
5.3 Software Debug Subsystem (3.0)
There are no flight requirements for this subsystem. It is available for softwaredevelopment purposes and will be disabled for flight. There is a serial debug port that
may be used for simple messages (printf.) There is also a debug data store available thatwill allow data to be transmitted along with the telemetry data on the downlink. This willallow non-flight parameters to be provided during software development.

Page 10 of 19

AMSAT Fox-1
IHU Software Architecture Specification
5.4 Sanity Check Subsystem (4.0)
This subsystem verifies the integrity of the running software and pulses the Watchdog
signal to reset the external watchdog timer. It will stop pulsing the Watchdog signal if it
detects a fault or if it receives a command from the Diagnostic subsystem to force a reset.
5.5 Telemetry Subsystem (5.0)
This module is responsible for collecting all of the telemetry information from theinterfaces, doing the Min/Max processing and providing the complete set of real-time,minimum and maximum telemetry parameters in the Telemetry Data Buffer. Note that
this data is to be in the packed binary format as specified in the Telemetry Data section of
the Downlink Protocol Specification.
5.5.1

Telemetry Subsystem Processing Specification// Telemetry Processing
Do this every 15 seconds;
Get all telemetry parameters;// Check Battery
If (Bus Voltage < 3.5 volts) {Send LOW BATTERY indication to Radiation Experiment Subsystem;}// Do MinMax processing
Read Min/Max Data from MRAM memory;
If (any errors) {Increment MRAM memory error counter;
Re-write data to clear errors;}
if (Clear Min/Max command was received) {Write current telemetry values to Min/Max;
Clear MRAM memory error counter;}else {// Normal Min/Max processing
Compare current values with stored Min/Max data;
Write any new Min/Max data to MRAM memory}
Send telemetry data to Communications Subsystem

Page 11 of 19

AMSAT Fox-1
IHU Software Architecture Specification
5.6 Command Subsystem (6.0)
This subsystem is responsible for interpreting and executing commands to the satellite.
The commands can come from ground control stations via the Hardware Command
Decoder interface or from the Diagnostics subsystem via the umbilical port. In the future,
the satellite will also accept commands from the communications subsystem via theuplink (not implemented for Fox-1.)
The Local Commands from the Diagnostics subsystem are:
1. Clear Telemetry Min/Max data
2. Got to Transponder Mode
3. Go to Data Mode
4. Send Test Message
The Command subsystem is responsible for setting the satellite operating mode. This isused by several subsystems to control their operation. If the satellite is commanded into
DATA Mode, it must automatically switch back to TRANSPONDER mode after 24hours unless a new DATA Mode command has been received.
5.6.1

Command Subsystem Processing Specification// Command Processing
Set Satellite Operating Mode to TRANSPONDER; // This is the default at power-up
Do this continuously {Wait for a new command;
switch(command) {case Clear Telemetry MinMax:
Send Clear Min/Max message to Telemetry subsystem
break;
case Transponder Mode:
Stop 24 Hour timer;
Set Satellite Operating Mode to TRANSPONDER;
break;
case Data Mode:
Start or re-start the 24 hour timer;
Set Satellite Operating Mode to DATA;
break;
case Send Test Message:
Send Test Command to Communications subsystem
break;
Page 12 of 19

AMSAT Fox-1
IHU Software Architecture Specification
default:// No processing for TX and IHU INHIBIT or ENABLE commands
Do nothing;}if (24 hour timer expires) {Set Satellite Operating Mode to TRANSPONDER;}}
5.7 Diagnostic Subsystem (7.0)
This subsystem implements a local user interface on the satellite through the UmbilicalUSB port. This is expected to be used for system testing and launch integration activities.
The Diagnostic Subsystem can read data from any Data buffer and can send commands to
the Command and Idle subsystems. It is also available for software development use.
This subsystem is not used in orbit. Note that if the satellite is being powered by the USB
Umbilical port, the antennas MUST NOT be deployed and the Communications
subsystem will prevent the transmitter power amp from being activated.
The following functions are the minimal set that is required. Additional commands can be
added as needed.
5.7.1
1.
2.
3.
4.
5.
6.

Umbilical Port Get Functions
Get Telemetry Data
Get Experiment Data (n= 1-4)
Get Satellite Mode (command or transponder mode)
Get Satellite Up time (MET)
Get IHU Reset Count
Get Software Versions (IHU, PSU, BAT)

5.7.2
1.
2.
3.
4.
5.
6.
7.
8.
9.

Umbilical Port Set Functions
Load the CPU Program (FLASH) Memory
Clear Telemetry Min/Max data
Clear IHU Reset Count
Clear MRAM error count
Got to Transponder Mode
Go to Data Mode
Send Test Message
Reset CPU (let external watchdog timer fire)
Force Antenna Deployment (only if NOT powered by USB port)

Page 13 of 19

AMSAT Fox-1
IHU Software Architecture Specification
5.8 Communications Subsystem (8.0)
This subsystem operates differently in TRANSPONDER and DATA modes.
5.8.1 Communications Subsystem TRANSPONDER Mode Operation
The diagram below shows the Communications subsystem data
TRANSPONDER mode.
Telemetry Data

Experiment Data

flow

in

Debug Data

Low-Speed
Downlink
ProtocolRx Audio
Samples

Low-Pass
FilterStoredAudio
Messages

Low-Speed
Modulator

High-Pass
FilterMixer

Samples

PL ToneDecoder

Downlink
Controller

IHU PTTIHU Audio Out

Test Command

The Low-Speed Downlink Protocol multiplexes the Telemetry, Experiment and Debug
Data and adds the header and forward error correction (FEC) fields as specified in the
Downlink Protocol Specification. The resulting bit-stream is fed to the Low Speed
Modulator which creates the audio samples for transmission.
Page 14 of 19

AMSAT Fox-1
IHU Software Architecture Specification
The Rx audio samples from the RF receiver are sent to a 3 kHz low-pass filter whichfeeds a 300 Hz high-pass filter and the PL Tone detector. The high-pass filter removes allof the audio components below 300 Hz so the spectrum is clean for the low-speed data
downlink signal. The filtered audio signal is sent to the Mixer.
The Mixer can select and combine the low-speed data downlink signal and the filtered Rx
audio signal or a Stored Audio Message under control of the Downlink Controller. The
Stored Audio Messages include the Beacon message, Test message and Silence.
The PL Tone decoder detects the presence of a 67 Hz PL tone and sends an indication ofthis to the Downlink Controller.
5.8.1.1 Downlink Controller - TRANSPONDER mode Processing Specification// Downlink Controller TRANSPONDER mode Processing
When satellite enters TRANSPONDER mode {Turn off IHU PTT;
Set Mixer source to Rx Audio and Low-Speed Modulator;}
do {if (PL Tone Detected) {if( NOT powered from USB port ) {Turn on IHU PTT;}
Start or restart 2-minute Hang Timer;
Stop Idle Timer;}if (Hang Timer Expires) {Turn off IHU PTT;
Start 2 minute Idle Timer;}// continued on next page

Page 15 of 19

AMSAT Fox-1
IHU Software Architecture Specification
if (Idle Timer Expires) {Set Mixer source to Silence;if( NOT powered from USB port ) {Turn on IHU PTT;}
Wait 5 seconds;// For Douglas!
Set Mixer source to Low-Speed Modulator and Beacon Message;
Wait until Beacon Message sent;
Set Mixer source to Low-Speed Modulator and Silence;
Wait 6 seconds;
Turn off IHU PTT;
Set Mixer source to Rx Audio and Low-Speed Modulator;
Re-start Idle Timer;}
if (Test Command received) {if( NOT powered from USB port ) {Turn on IHU PTT;}
Wait 1 second;
Set Mixer source to Test Message and Low-Speed Modulator;
Wait until Test Message sent;if (Hang Timer is not running) {Wait 1 seconds;
Turn off IHU PTT;}
Set Mixer source to Rx Audio and Low-Speed Modulator;}}// end of TRANSPONDER mode, downlink controller processing

Page 16 of 19

AMSAT Fox-1
IHU Software Architecture Specification
5.8.2 Communications Subsystem Data Mode Operation
The diagram below shows the Communications subsystem data flow in DATA mode.
Camera Data Telemetry Data

Experiment Data

Debug Data

High-Speed
Downlink
ProtocolStoredAudio
Messages

High-Speed
Modulator

IHU Audio Out

Rx Audio
Samples

UplinkDemodulator

Mixer

Samples

UplinkProtocolDownlink
Controller

IHU PTT

Uplink Co mmands

Test Command

The High-Speed Downlink Protocol multiplexes the Camera, Telemetry, Experiment andDebug Data and adds the header and forward error correction (FEC) fields to create
downlink frames. The resulting bit-stream is fed to the High-Speed Modulator which
creates the audio samples for transmission. The Mixer can select the Modulator samples
or a selected Stored Audio Message under control of the Downlink Controller. The
Stored Audio Messages include the Beacon message, Test message and silence. The
uplink demodulation and protocol functions are not implemented in Fox-1 but are shownfor completeness.
Page 17 of 19

AMSAT Fox-1
IHU Software Architecture Specification
5.8.2.1 Downlink Controller DATA mode Processing Specification// Downlink Controller DATA mode Processing
When Satellite enters DATA mode {Set Mixer Source to High-Speed Modulator only;
if( NOT powered by USB port ) {Turn on IHU PTT;}}do {if (Test Command received) {Set Mixer source to Silence;
Wait 1 second;
Set Mixer source to Test Message;
Wait until Test Message sent;
Set Mixer source to Silence;
Wait 1 second;}
Set Mixer Source to High-Speed Modulator;} while (satellite is in DATA mode)// Satellite switched to TRANSPONDER mode
Turn off IHU PTT;
Do nothing until satellite goes back into DATA mode;

Page 18 of 19

AMSAT Fox-1
IHU Software Architecture Specification

6

System Considerations

6.1 Operating System
The IHU software will use the free version of the FreeRTOS operating system.
6.2 Physical Device Drivers
These physical device drivers are needed to access and control the STM32 I/O interfaces.
1.
2.
3.
4.
5.
6.
7.

I2C Bus
SPI BusUART
A/D converter channels
D/A converter channels
GPIO inputs
GPIO outputs

6.3 Performance Requirements
The Rx Audio A/D and the IHU Audio D/A converters have hard real-time requirements.
DMA should be considered to offload the CPU for these interfaces.
6.4 Operational Constraints
The software is intended to run on orbit but must also be able to run inside the P-Pod to
support the launch integration activities. Inside the P-POD, the power for the satellite will
come from the USB Umbilical port. When powered from this port (i.e. inside the PPOD,) the antennas MUST NOT be deployed and the RF transmitter power amp MUSTNOT be turned on.
6.5 Modularity and Maintainability
The experiments will be different for each future Fox-1 type satellite mission. The
experiment and camera processing software needs to be modularized so that they are easy
to change.

7 Closing Notes
This document provides the desired behavior and a structure for the IHU software. It is
expected that appropriate design documentation will be provided in addition to thisdocument to describe the implementation details.

Page 19 of 19

Introduction to Fox1 Mechanical Drawings
Robert Davis, KF4KSS

The following 54 pages are the current drawings for AMSAT’s Fox1 cubesat. These aredraft, and in a few circumstances, the design has been modified slightly from thedrawings as currently updated. Some drawings use color, if meaningful information canbe shared, like material or circuit board layout. All drawings should be considered draft,as we have not committed to fabrication of flight units yet. However, in many instances,the drawings represent a very mature design.
We are just about to assemble engineering units, which would be available for
operational testing, mechanical fit checks, and prototype environmental tests. For someparts, earlier prototypes were also built. This year, prototypes were built that have helped
mature the design of the PCB Stack, sheetmetal Walls, and Solar Panel printed circuitboards. We now have many pieces on hand, and we’re looking out for things likeassembled tolerances. Significant prototype effort has also been placed in the +Y and –Y
Solar Panels, which share a common circuit board design but populated differently for the
RX and TX antennas. Long-term stow, vibration resistance, and deploy tests will bestarting soon on those antennas. A thermal vacuum test of the battery board is also
imminent.

Our progress has only been possible through the efforts of multiple people,
within our small mechanical team and across many disciples and components.
Please consider volunteering!

SIDE VIEW(SCALE 1 : 2)

TOP VIEW(SCALE 1 : 2)

100.0 B0.1

8.5 MINSPRINGS AND SWITCH(ES)ON RAILS OF -Z FACE,
SEE NOTE 2.

113.5 B0.1

8.5 MIN

56.5 MAX
56.5 MAX+Z

100.0 B0.1

+Y

+X

+X

6.5 MAX
4 SIDES
6.5 MIN
R

0
1.

M

+Z

IN

DATE

1:2

SIZE

SCALE

SHEET
UNLESS NOTED OTHERWISE:UNITS: mm [in] TOLERANCE: +/-0.5

DWG.NO.

REV.

1/1

FOX
1U ENVELOPE
A 2011-04-04 FOX-ME-101 0.2+X+Y

ISO VIEW(SCALE 1 : 2)AMSAT

DETAIL A(SCALE 1 : 1)

6.5 MINNOTES:
1) INTERPRETATION OF CUBESAT DESIGN SPECIFICATION REV 12.
2) ENVELOPE FOR ALL HARDWARE EXCEPT FREE STATE OF
A) PLUNGER OF TWO SEPARATION SPRINGSB) PLUNGER OF ONE OR TWO CONTACT SWITCH(ES)

6
0.
14

SEE
DETAIL A

-X FACE-Z FACE-Y FACE+Z FACEDEPLOYED+X FACESCALE 1 : 2

1:2

SHEET

FOX-ME-103

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-10-09

DATE

A

SIZE

SCALE

FOX
FOX1 ASSEMBLY+Y FACEAMSAT(ANTENNAS CROPPED)

0.4
1 OF 5

REV.

ISO +X+Y+Z
SCALE 3 : 4

3:4

SHEET

FOX-ME-103

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-10-09

DATE

A

SIZE

FOX
FOX1 ASSEMBLY

AMSAT
SCALE

ISO -X-Y-Z
SCALE 3 : 4

0.4
2 OF 5REV.

+X FACE
TRUE ANTENNA LENGTHSSCALE 0.2 : 1

1:5

SHEET

FOX-ME-103

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-10-09

DATE

A

SIZE

SCALE

FOX
FOX1 ASSEMBLY

AMSAT

0.4
3 OF 5REV.

-X FACE-Z FACE-Y FACE+Z FACE+X FACESCALE 1 : 2

DEPLOYED

1:2

SHEET

FOX-ME-103

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-10-09

DATE

A

SIZE

SCALE

FOX
FOX1 ASSEMBLYAMSAT+Y FACE

0.4
4 OF 5

REV.

ISO +X+Y+Z
SCALE 3 : 4

3:4

SHEET

FOX-ME-103

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-10-09

DATE

A

SIZE

FOX
FOX1 ASSEMBLY

AMSAT
SCALE

ISO -X-Y-Z
SCALE 3 : 4

0.4
5 OF 5

REV.

10

QTY

5

10

4

ITEM

2

10

1

3

100,00 [3.937]
SEE NOTE 1

Parts List

PART NUMBER

90945A705

MCMASTER-CARR 93085A017

NAS662C2R4 /MS21042-02

FOX-ME-111-03

DESCRIPTIONWASHER, #2 THIN, NAS620C2

FHCS, #2-56 X 1/4" X 100° SS

LOCK NUT, #2-56

WALLS, BENTNOTES:
1) AT ASSEMBLY, ALIGN BOTH DIMENSIONS.
TORQUE #2-56 NUTS TO 2.5 IN-LB, OR 40 IN-OZ.
2. CONFORMAL COAT OR EPOXY COAT
CAD-PLATED STEEL NUTS.

100,00 [3.937]
SEE NOTE 1

1:2

SHEET

FOX-ME-111

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-04-25

DATE

A

SIZE

SCALE

FOX
WALLS

AMSAT

-01 WALLS

0.6
1 OF 3REV.

6X P2,69 [0.106],
NO. 36 DRILL

12,00 [0.472]

9X P2,39 [0.094], 3/32" DRILL,

83,5 [3.29]

88,00 [3.465]

95,00 [3.740]

MIN 9,0 [0.35] WIDE STRIPSSEE NOTE 6
1.6

16,5 [0.65](R1,0 [0.04]
EXTERNAL)

73,20 [2.882]

73,20 [2.882]

104,00 [4.094]

98,00 [3.858]

2X R0,5 [0.02] x 10,0 [0.39] LONG,OPTIONAL CHAMFER 0,5 [0.20] X 45`

108,00 [4.252]

104,00 [4.094]

93,0 [3.66]

92,40 [3.638]

54,00 [2.126]

54,00 [2.126]

83,0 [3.27]

34,80 [1.370]

34,80 [1.370]

10,00 [0.394]

15,0 [0.59]
25,0 [0.98]

4,00 [0.157]

4,00 [0.157]
15,60 [0.614]

0,00 [0.000]

0,00 [0.000]

2X R0,5 [0.02] X 10,0 [0.39] LONG,OPTIONAL CHAMFER 0,5 [0.20] X 45`

2X R0,5 [0.02] X 10,0 [0.39] LONG,OPTIONAL CHAMFER 0,5 [0.20] X 45`

1.6

1.6

0,00 [0.000]

0,00 [0.000]

YP4,4 [0.17] X 100°
2X R0,5 [0.02], OPTIONALNOTES:CHAMFER 0,5 [0.20] X 45`
3) MATERIAL: ALUMINUM 5052-H32.
4) DO NOT SCUFF.
5) CHEMICAL CONVERSION COAT PER MIL-DTL-5541 CLASS 3, ELECTRICALLY CONDUCTIVE CLEAR.
6) HARD ANODIZE AREAS SHOWN PER MIL-A-8625 TYPE III, CLASS 1, CLEAR.
INCLUDE BEND/ROUND, CONSUMED HOLES AND SHEETMETAL EDGES.

4X R6,4 [0.25]

100,00 [3.937] +0/-0.1

1.6

90
°

16,5 [0.65]

68,5 [2.70]

99,00 [3.898]

88,00 [3.465]

31,5 [1.24]

6X P2,69 [0.106],
NO. 36 DRILL

YP4,4 [0.17] X 100°

4X P2,39 [0.094], 3/32" DRILL

135°

°
90

-03 WALLS, BENT

SCALE

1:2

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

SHEET

FOX-ME-111

DWG.NO.

WALLS
2013-04-25

DATE

0.6
2 OF 3REV.

BACKGROUND FEATURESNOT SHOWN FOR CLARITY
R0,5 [0.02], OPTIONAL
CHAMFER 0,5 [0.20] X 45`

A

SIZE

92,40 [3.638]
5X P2,69 [0.106],
NO. 36 DRILL

4X R6,4 [0.25]

73,20 [2.882]

54,00 [2.126]

34,80 [1.370]

15,60 [0.614]

0,00 [0.000]

R0,5 [0.02], OPTIONAL
CHAMFER 0,5 [0.20] X 45`(R1,0 [0.04]
EXTERNAL)

R0,0 [0.00](SHARP INTERNAL BEND)

83,5 [3.29]

R1,0 [0.04]

0,00 [0.000]

MIN 8,0 [0.32] WIDE STRIPSEE NOTE 6

5,00 [0.197]

MIN 9,0 [0.35] WIDE STRIPSEE NOTE 6

7,5 [0.30]

12,00 [0.472]

8X R6,4 [0.25]

0,00 [0.000]

4,00 [0.157]

10,00 [0.394]

15,0 [0.59]

15,60 [0.614]

25,0 [0.98]

34,80 [1.370]

54,00 [2.126]

73,20 [2.882]

83,0 [3.27]

92,40 [3.638]

93,0 [3.66]

98,0 [3.86]

104,00 [4.094]

130,19 [5.126]
115,19 [4.535]

110,69 [4.358]

88,00 [3.465]

83,50 [3.287]

REFERENCE DIMENSIONSPOSITION/TOLERANCE FROM BENDS-03 WALLS, FLAT PATTERN
SCALE

A

SIZE

1:2

186,69 [7.350]

203,88 [8.027]

201,38 [7.928]
UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

SHEET

FOX-ME-111

DWG.NO.

WALLS

182,19 [7.173]

2013-04-25

DATE

135°

167,19 [6.582]

108,00 [4.252]

4X R6,4 [0.25]

0.6
3 OF 3REV.

1,0 [0.04]

16,50 [0.650]

12,00 [0.472]

5,00 [0.197]

0,00 [0.000]

-Y VIEW

98,00 [3.858]
8,00 [0.315]
TYP 9 PL

+Z VIEW-Z VIEW-X VIEW

98,00 [3.858]

98,00 [3.858]
87,9 [3.46]

98,00 [3.858](4,6 [0.18])
4,5 [0.18]+Y VIEW

1:2

SHEET

FOX-ME-112

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2012-08-15

DATE

A

SIZE

SCALE

FOX
PCB ASSEMBLYAMSAT+X VIEW

0.3
1 OF 3

REV.

2

32

6

4

8

24

8

8

4

1

1

1

1

1

1

1

1

1

1

QTY

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

ITEM

1

20

Parts List

PART NUMBER

FOX-ME-113-01

FOX-ME-113-02

FOX-ME-113-03

FOX-ME-113-04

FOX-ME-113-05

FOX-ME-113-06

FOX-ME-113-07

FOX-ME-113-08

FOX-ME-113-09

FOX-ME-113-10

FOX-ME-123

MS21042-04

MCMASTER-CARR 90945A710

NAS620-C4L /FOX-ME-117-01

FOX-ME-117-03

FOX-ME-117-05

FOX-ME-118-01

MCMASTER 90792A312

FOX-ME-118-03

FOX-ME-124

TX PCBRX PCBIHU PCBDESCRIPTIONPSU PCBBATTERY #1

BATTERY #2 PCB

EXPERIMENT #1 PCB

EXPERIMENT #2 PCB

EXPERIMENT #3 PCB

EXPERIMENT #4 PCB

THREADED ROD

LOCKING NUT, #4-40

WASHER, #4 THIN

AL SPACER

CU SPACER FOR DELRIN

AL THREADED SPACERPCB DELRIN MOUNTSHIM WASHER, 3/16" ID X 0.010"

PCB DELRIN MOUNTMAGNET

THIS AREA SHOWN EXPLODEDFOR CLARITY OF SPACER INSIDE DELRINAND SHIM WASHERS ABOVE AND BELOW.

16

15

12

3X 14

19

20

2X 18

19

2X 18

1) LOCATE ITEM 12 ON ITEM 11 TO PROTRUDE 4,5 [0.18] FROM PCB.
2) STACK PCBS ITEMS 1-5 AS SHOWN USING SPACERS ITEMS 14-16.
CORNER -X-Y RECEIVES MAGNET BETWEEN 2X DELRIN ITEM 19.
CORNERS -X+Y, +X+Y, +X-Y RECEIVES 2X DELRIN ITEM 17.
VERTICAL SPACING BETWEEN DELRIN MOUNT SCREWS MAY BE ADJUSTEDBY MOVING SHIM WASHERS, ITEM 18.
3) TORQUE ITEM 16 TO TBD IN-LB.
4) ITEM 6 MAY BE PLACED BUT HAS NO HARDWARE.

ASSEMBLY OF AVIONICS PORTION OF PCB STACK

1
2

17

3

4

5

SCALE

A

SIZE

6

1:1

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

SHEET

FOX-ME-112

DWG.NO.

PCB ASSEMBLY
2012-08-15

DATE

4X 14

0.3
2 OF 3

REV.

17

17

17

3X 14

17

14

2X 12

5) STACK PCBS ITEMS 7-10 AS SHOWN USING SPACERS ITEMS 14-16.
SPACING BETWEEN DELRIN MOUNT SCREWS MAY BE ADJUSTEDBY MOVING SHIM WASHERS, ITEM 18.
6) TORQUE ITEM 16 TO TBD IN-LB.
7) VERIFY PROTRUSION OF THREADED ROD IS SAME TOP/BOTTOM +/- 1,0 [0.04].

ASSEMBLY OF AVIONICS PORTION OF PCB STACK

SCALE

A

SIZE

DATE

1:1

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

SHEET

FOX-ME-112

DWG.NO.

PCB ASSEMBLY
2012-08-15

REV.

0.3
3 OF 3

7

8

9

10

14,50 [0.571]

11,00 [0.433]

10,00 [0.394]

8,00 [0.315]

0,00 [0.000]

2X P1,02 [0.040] #60 DRILLALIGNMENT HOLES FORSAMTEC QSH-030-01-L-D-A
ON -Z BOTTOM SIDE.

0,00 [0.000]

8,00 [0.315]

10,00 [0.394]

11,00 [0.433]

14,50 [0.571]

80,50 [3.169]

84,00 [3.307]

85,00 [3.346]

87,00 [3.425]

95,00 [3.740]+Y AXIS

49,53 [1.950]

44,83 [1.765]

4X P3,18 [0.125]+Z TOP VIEW ( 1 : 1 )85,00 [3.346]

84,00 [3.307]

80,50 [3.169]

2X P1,02 [0.040] #60 DRILLALIGNMENT HOLES FORSAMTEC QTH-030-02-L-D-A
ON +Z TOP SIDE.

0,00 [0.000]

5,43 [0.214]

6,26 [0.246]

24,75 [0.974]

25,57 [1.007]+X AXISTYPICAL PCB

1,59 [0.063]

SCALE

A

SIZE

1:1

DATE

PCB
SHEET

FOX-ME-113

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-07-19

FOX

AMSAT
0.8
1 OF 11REV.

SEE CONTINUATION SHEETS FOR
SPECIFIC PCB ADDITIONS / EXCEPTIONS.

4X COMPONENT STAY-OUT ZONES,+Z TOP AND -Z BOTTOM SIDES.
PROVIDES 2,00 [0.079] CLEARANCEBETWEEN COMPONENTS

87,00 [3.425]

4X P6,35 [0.250]
PAD TO GROUND,+Z TOP AND -Z BOTTOM SIDES.

95,00 [3.740]

0,00 [0.000](15,50 [0.610])+Z TOP VIEW

(47,50 [1.870])

0,00 [0.000]

PIN 1 OFSAMTEC QTH-030-02-L-D-A

PIN 1 OFSAMTEC QSH-030-01-L-D-A

SCALE

A

SIZE

1:1

DATE

PCB
SHEET

FOX-ME-113

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-07-19

0.8
2 OF 11REV.

SEE CONTINUATION SHEETS FOR
SPECIFIC PCB ADDITIONS / EXCEPTIONS.

TYPICAL CONNECTORS2X 7,00 [0.276]

0,00 [0.000]

5,00 [0.197]

2X 0,50 [0.020]

31,00 [1.220]

24,00 [0.945]

0,00 [0.000]

2X P1,50 [0.059]

NOT USED IN FLIGHT.
MAY BE POPULATED FOR TEST UNITS.
FITS IN GAP TO -Z SOLAR PANEL.

COMPONENT STAYOUT ZONE(+Y SOLAR PANEL COAXIS HOVERING JUST OFF PCB)

SCALE

A

SIZE

DATE

1:1

PCB
SHEET

FOX-ME-113

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-07-19-01 TXPIN 1 OFSAMTEC FSI-105-06-S-S-AD

C&K HDT0004 MICRO MINI SURFACE MOUNT DETECT SWITCHESAT TWO CORNERS AS CUBESAT SEPARATION SWITCHESVIA PLUNGER THROUGH RAIL ENDS.
PLACE COMPONENT SO BLADE IS AS CLOSE AS FEASIBLE TO PCB CORNER,
BUT COMPONENT MAY NOT OVERHANG PCB EDGE.

0.8
3 OF 11REV.

COAX OVER THIS EDGE
TO -Y SOLAR PANEL

SCALE

A

SIZE

DATE

1:1

PCB
SHEET

FOX-ME-113

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-07-19-02 RX

0.8
4 OF 11REV.

SCALE

A

SIZE

1:1

DATE

PCB
SHEET

FOX-ME-113

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-07-19-03 IHU

0.8
5 OF 11

REV.

0,00 [0.000]

8,00 [0.315]

24,13 [0.950]

30,88 [1.216]

64,13 [2.525]

70,88 [2.790]

87,00 [3.425]

TO PIN 2 OFSAMTEC MEC1-105-02-NP-L-D-A
4 PLACES

64,13 [2.525]

24,13 [0.950]

8,00 [0.315]

0,00 [0.000]

4X CHAMFER 0,76 [0.030] X 45°
4 PLACES

70,88 [2.790]

8X 2,36 [0.093]

87,00 [3.425]

30,88 [1.216]

SCALE

A

SIZE

1:1

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

SHEET

FOX-ME-113

DWG.NO.

PCB-04 PSU

2013-07-19

DATE

2X CHAMFER 1,40 [0.055] X 0.20 [0.008]
4 PLACES

0.8
6 OF 11

REV.

0,00 [0.000]

14,75 [0.581]

22,50 [0.886]

45,50 [1.791]

53,40 [2.102]

64,50 [2.539]

66,00 [2.598]

67,25 [2.647]

72,00 [2.835]

83,00 [3.268]

90,00 [3.543]

90,50 [3.563]

2X R1,39 [0.055]
SLOT ON EDGE

12X P2,78 [0.109]

90,50 [3.563]

83,00 [3.268]

73,75 [2.903]
72,00 [2.835]

74,50 [2.933]

66,00 [2.598]

66,00 [2.598]
64,50 [2.539]

30,50 [1.201]

29,00 [1.142]
29,00 [1.142]

21,25 [0.837]

20,50 [0.807]
23,00 [0.906]

12,00 [0.472]

6,00 [0.236]

4,50 [0.177]

0,00 [0.000]

0,00 [0.000]

0,00 [0.000]

14,00 [0.551]

68,00 [2.677]

4X R1,39 [0.055]
ON EDGE

4X R1,39 [0.055]
ON SLOT

10X R0,64 [0.025] SLOT

SCALE

A

SIZE

1:1

DATE

PCB
SHEET

FOX-ME-113

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-07-19

REV.

0.8
7 OF 11-05 BATTERY #1

32,0 [1.26]

5,33 [0.210]

0,00 [0.000]

PIN 1 OFSAMTEC QTH-030-02-L-D-A

0,00 [0.000]

5,43 [0.214]

6,25 [0.246]

24,75 [0.974]

25,57 [1.007]+Z TOP VIEW

10,03 [0.395]

2X P1,02 [0.040] #60 DRILLALIGNMENT HOLES FORSAMTEC QSH-030-01-L-D-A
ON -Z BOTTOM SIDE.

16,0 [0.63]
WIDER UPON REQUESTPIN 1 OFSAMTEC QSH-030-01-L-D-A

1,59 [0.063]

2X P1,02 [0.040] #60 DRILLALIGNMENT HOLES FORSAMTEC QTH-030-02-L-D-A
ON +Z TOP SIDE.

SCALE

A

SIZE

1:1

DATE

PCB
SHEET

FOX-ME-113

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-07-19-06 BATTERY #2

0.8
8 OF 11REV.

SCALE

A

SIZE

1:1

DATE

PCB
SHEET

FOX-ME-113

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-07-19

REV.

0.8
9 OF 11-07 EXPERIMENT #1-08 EXPERIMENT #2

0,00 [0.000]

82,00 [3.228]

47,50 [1.870]

0,00 [0.000]

CAMERA BORESIGHT
AND VOLUME PLACEHOLDER

SCALE

A

SIZE

1:1

DATE

PCB
REV.

0.8
10 OF 11SHEET

FOX-ME-113

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-07-19-9 EXPERIMENT #3

0,00 [0.000]

69,00 [2.717]

60,50 [2.382]

HOLES MAY BE ADDED AROUND PERIMETER OF PCBFOR BALLAST MASSES

PIN 1 OFSAMTEC FSI-105-06-S-S-AD

SCALE

A

SIZE

0,00 [0.000]

5,00 [0.197]

1:1

DATE

PCB
REV.

0.8
11 OF 11SHEET

FOX-ME-113

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-07-19-10 EXPERIMENT #4

2X P1,50 [0.059]

0,00 [0.000]
64,00 [2.520]

71,00 [2.795]

34,50 [1.358]

0,00 [0.000]

76,00 [2.992]

SIGNAL RELAY
REPRESENTATIVE POSITION/ORIENTATIONTOP SIDE DUE TO 8.2MM HEIGHTSAFE RBF JACK
2.5MM AUDIO, 4-CONDUCTOR

1,54 [0.061]

UMBILICAL JACKMINI USB B, 5 CONDUCTOR

15,60 [0.614]

3:4

SHEET

FOX-ME-114

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-09-11

DATE

A

SIZE

SCALE

0.3
1 OF 4REV.

FOX
BATTERY ASSEMBLYAMSAT

POTENTIAL LED POSITIONSVISIBILE THRU HOLES IN X SOLAR PANELS

2X FOX-ME-125 HYSTERESIS RODS

17,20 [0.677]
3,54 [0.139]

6X SANYO KR1700AU "A" CELLS

76,00 [2.992]

DESIRED BONDS

MIN 5,55 [0.219]

9 [0.4]

MAX 5,00 [0.197]

NOTES:
1) SOLDER REFLOW COMPONENTS ON PCB BEFORE BONDING BATTERIES.
DESIRED BONDS
2) DO NOT BEND BATTERY TABS UNDER PCB UNTIL ASSEMBLY SOLDER STEP.
3) REMOVE MANUFACTURER'S SHRINK-WRAP LABEL.
APPLY KAPTON TAPE TO POSITIVE TAB TO PREVENT SHORTING TO CASE AFTER BENDING.
CAUTION: TERMINAL SHORTING HAZARD. REMOVE COMPOSITE WASHER ON POSITIVE END.
BEND BOTH TABS 180° FOR STRAIGHT RELIEF.
9 [0.4]
WIPE WITH ISOPROPYL ALCOHOL.
4) APPLY KAPTON HEATER OMEGA KHLV-102/5-P. WRAPS APPROX 1/2 OF SURFACE AREA.
DO NOT APPLY BETWEEN CELLS OR BETWEEN CELLS AND PCB.
CLOCKING AROUND PERIMETER TBD. ORIENTATION OF LEADS TBD.
5) WRAP CELL WITH 1 LAYER OF 2 INCH WIDE 1 MIL PERMACEL P224 KAPTON POLYIMIDE TAPE WITH ACRYLIC ADHESIVE.
6) PREPARE KAPTON WRAPPED SURFACE OF CELL FOR BONDING BY ACETONE SOLVENT CLEANING.
7) USE HYSOL/LOCTITE EPOXI-PATCH 9340 TO BOND PAIRS OF CELLS, AND CELLS TO PCB. WET BOTH MATING SURFACES.
SECURE WITH LACTING TAPE BREYDEN 104-3 IF POT LIFE PERMITS, OTHERWISE USE TEMPORARY 0.032" WIDE X 4" LONG ZIP TIES.
KEEP HOLES CLEAR OF EPOXY.
PRESS LEADED THERMISTOR INTO EPXOY. DIRECTION OF LEADS AS SHOWN.
CURE ROOM TEMPERATURE FOR 24 HOURS, OR 50°C (122°F) FOR 6 HOURS.

SANYO KR1700AU "A" CELL
WITH WELDED TABSSEE NOTES 2-4.

KAPTON TAPE TO PREVENT SHORT.
SEE NOTE 2.

R0,75 [0.030]
STRAIN RELIEF BEND
BOTH TERMINALS

50 [2.0]50,80 [2.000]
HEATER/TAPE WRAP
47,50 [1.870]
BARE CELL

34 [1.4]

SCALE

A

SIZE

3:4

DATE

SHEET

FOX-ME-114

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-09-11

0.3
2 OF 4REV.

BATTERY ASSEMBLY

50 [2.0]

POSITIVE TERMINALSDIRECTION OF THERMISTOR LEADSPOSITIVE TERMINALS

SCALE

A

SIZE

1:1

DATE

SHEET

FOX-ME-114

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-09-11

0.3
3 OF 4REV.

BATTERY ASSEMBLY

LACING TAPE KNOTS SHOULD NOT ADD
TO WIDTH OR HEIGHT OF BATTERY.

POSITIVE TERMINALS

12,5 [0.49]

92,5 [3.64]

SCALE

A

SIZE

VARIES

DATE

SHEET

FOX-ME-114

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-09-11

0.3
4 OF 4REV.

NOTES:
8) WRAP PERIMETER OF 2X FOX-ME-125 HYSTERESIS RODS WITH 1 LAYER OF 1 MIL PERMACEL P224 KAPTON POLYIMIDE TAPE WITH ACRYLIC ADHESIVE.
9) PREPARE KAPTON WRAPPED SURFACE OF RODS FOR BONDING BY ACETONE SOLVENT CLEANING.
10) BOND RODS USING HYSOL/LOCTITE EPOXI-PATCH 9340. SECURE WITH BREYDEN 204-3 LACING TAPE.
PLACE KNOT TO PREVENT INCREASING HEIGHT ABOVE PCB.
CURE ROOM TEMPERATURE FOR 24 HOURS, OR 50°C (122°F) FOR 6 HOURS.
BATTERY ASSEMBLY
11) SECURE ALL KNOTS WITH TBD URALANE.

0,0 [0.00]

12,5 [0.49]

82,5 [3.25]

92,5 [3.64]

82,5 [3.25]

LACING TAPE KNOTS SHOULD NOTADD TO HEIGHT OR WIDTH.

0,0 [0.00]

#31 DRILL#31 DRILL

MAT'L: BLACK DELRIN
MAKE FROM MCMASTER-CARR 8576K11 ROD.

MAT'L: BLACK DELRIN
MAKE FROM MCMASTER-CARR 8576K11 ROD.

-09 DELRIN SPACER FOR MOUNT

2:1

SHEET

FOX-ME-117

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-08-24

DATE

A

SIZE

SCALE

FOX
PCB SPACER

AMSAT

0.5
1 OF 1REV.

MAT'L: ALUMINUM 6061-T6
MAKE FROM MCMASTER-CARR 91780A427 STANDOFF.
CHEMICAL CONVERSION COAT PER MIL-C-5541
CLASS 3, ELECTRICALLY CONDUCTIVE CLEAR.

MAT'L: COPPER ALLOY 110 H04 (HARD)
MAKE FROM MCMASTER-CARR 8966K88 ROD.
GOLD PLATE.

-07 DELRIN SPACER-05 AL THREADED SPACER-03 CU SPACER FOR MOUNT

MAT'L: ALUMINUM 6061-T6
MAKE FROM MCMASTER-CARR 8974K31 ROD.
CHEMICAL CONVERSION COAT PER MIL-C-5541
CLASS 3, ELECTRICALLY CONDUCTIVE CLEAR.

9,75 B0,05 [0.384 B0.002](#4-40 THRU)-01 AL SPACER

8,15 B0,05 [0.321 B0.002]

P3,05 [0.120]

P3,05 [0.120]

8,15 B0,05 [0.321 B0.002](P4,76 [0.188])(P6,35 [0.250])(6,35 [0.250])

7,00 [0.276]

11,0 [0.43]

1,0 [0.04]
KERF WIDTH

14,0 [0.55]

1,0 [0.04]
KERF WIDTH-01

R8,5 [0.33]

P2,44 -8,0 DEEPY P 2,5 X 120°

SEE NOTE 2.

P2,44 -8,0 DEEPY P 2,5 X 120°

SEE NOTE 2.

11,00 [0.433]

9,50 [0.374]

11,00 [0.433]

3,0 [0.12]

4,00 [0.157]

2) STI TAP #2-56 MIN Z4,0 [0.16] , USING HELICOIL BOTTOMING TAP 02CBB.
INSTALL HELICOIL #2-56 X 1 DIA 3585-02CN0086,
USING HELICOIL INSTALLATION TOOL 551-02.
REMOVE TANG USING HELICOIL TANG-BREAKOFF TOOL 3695-02.

NOTES:
1) MATERIAL: BLACK DELRIN

0,5 [0.02] X 45°

0,00 [0.000]

4,00 [0.157]

9,50 [0.374]

11,0 [0.433]

14,0 [0.55]

BOTH ENDS

0,00 [0.000]

3,50 [0.138]

YP5.8 X 120`

P4,78 THRU

3,0 [0.12]

3,50 [0.138]

0,5 [0.02] X 45°

2:1

SHEET

FOX-ME-118

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-03-27

DATE

A

SIZE

SCALE

0.6
1 OF 2REV.

FOX
PCB DELRIN MOUNT

AMSAT

7,00 [0.276]

0,5 [0.02] X 45°

4,00 [0.157]
4,50 [0.177]

9,50 [0.374]

11,0 [0.43]

14,00 [0.551]

SEE NOTE 2.

-03

SEE NOTE 2.

11,00 [0.433]

6,8 [0.27]

11,00 [0.433]

P2,44 -8,0 DEEPY P 2,5 X 120°

CIRCULAR POCKET

P6,35 [0.250] 5,5 [0.22] DEEP

2,68 [0.105]

0,00 [0.000]

2,5 [0.10]

4,50 [0.177]

6,8 [0.27]

P2,0 [0.08]

1,0 [0.04]
KERF WIDTH

P2,44 -8,0 DEEPY P 2,5 X 120°

2,5 [0.10]

3,50 [0.138]

3,0 [0.12]

1,0 [0.04]
KERF WIDTH

0,00 [0.000]

0,50 [0.020]

4,00 [0.157]

9,50 [0.374]

11,0 [0.43]

14,00 [0.551]

BOTH ENDS

0,00 [0.000]
0,00 [0.000]

YP5,8 X 120`

2,68 [0.105]

P4,78 THRU

3,0 [0.12]

3,50 [0.138]

SCALE

A

SIZE

0,5 [0.02] X 45°

2:1

DATE

SHEET

FOX-ME-118

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2013-03-27

0.6
2 OF 2REV.

PCB DELRIN MOUNT1ST SURF METAL TAPE
SpaceQuest UTJ

1

2

2

QTY

4

7

ITEM
Parts List

PART NUMBER

FOX-ME-122(70,61 [2.780])

DESCRIPTIONTHERMISTOR, 0805

EDGE CARD CONNECTOR

PCB

5

MEC1-105-02-S-D-NP-A

SAMTEC

FOX-ME-119-05

1

TOP SIDE

10,00 [0.000]

31,50 [0.059]

1

0,00 [0.000]

2,30 [0.091](42,00 [1.654])

TAPE OVER
HOLE FORMINI-USB,
SEE FOX-ME-130(63,00 [2.480])

102,70 [4.043]

TAPE OVER
HOLE FOR
AUDIO JACK,SEE FOX-ME-130-01 +/-X

49 [1.9]

DATE

1:1

SHEET

FOX-ME-119

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-11

SIZE

A

0,00 [0.000]

39,38 [1.550]

83 [3.3]

0.8
1 OF 3REV.

FOX
X SIDE SOLAR PANEL

AMSAT
SCALE

BOTTOM SIDETHERMISTOR

0,00 [0.000]

60,50 [2.382]

6X P2,69 [0.106]

TOP SIDE

P9,53 [0.375]

69,00 [2.717]

16,45 [0.647]

7,56 [0.297]

2,50 [0.098]

0,00 [0.000]

NOTES:
1) FLASH GOLD TOP AND BOTTOM SIDES, ANY AVAILABLE AREA.

0,00 [0.000]

4,00 [0.157]

48,83 [1.922]

52,60 [2.071]

54,00 [2.126]

55,18 [2.172]

104,00 [4.094]

108,00 [4.252]

81,00 [3.189]
78,50 [3.091]

1,59 [0.063]-05 PCB

1:1

SHEET

FOX-ME-119

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-11

DATE

A

SIZE

SCALE

0.8
3 OF 3REV.

FOX
X SIDE SOLAR PANELAMSATBOTTOM SIDETHERMISTOR, 0805
IR FILTER

1

QTY

9

ITEM
Parts List

PART NUMBER

DESCRIPTIONSpaceQuest UTJ

1

PCB

7

FOX-ME-122

FOX-ME-120-03

0,00 [0.000]26,30 [0.248]

1(46,00 [1.811])

6(51,00 [2.008])

1

0,00 [0.000]

13,95 [0.549](83,06 [3.270])

TOP SIDE-01+Z TOPTHERMISTOR

25 [1.0]
SQUARE

1:1

SHEET

FOX-ME-120

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-12

DATE

A

SIZE

SCALE

0.9
1 OF 3REV.

FOX
Z TOP/BOTT SOLAR PANEL

AMSAT

0,00 [0.000]

35,00 [1.378]

COVER HOLE WITH TBD IR FILTERUSING TBD COMPOUND

28,00 [1.102]

BOTTOM SIDE

0,00 [0.000]
90,70 [3.571]

THERMISTOR, 0805
1ST SURF METAL TAPE

1

QTY

8

ITEM
Parts List

PART NUMBER

DESCRIPTIONSpaceQuest UTJ

1

PCB

7

FOX-ME-122

2

FOX-ME-120-03

1

6

TOP SIDE]1

TBD 1ST SURF METAL TAPE

19
SQ , 0 5
U [0
AR .7
E 50

-03
-Z BOTTOM

1:1

SHEET

FOX-ME-120

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-12

DATE

A

SIZE

SCALE

0.9
2 OF 3REV.

FOX
Z TOP/BOTT SOLAR PANELAMSATBOTTOM SIDETHERMISTOR

14,00 [0.551]
3,09 [0.122](INTERSECT
3,75 [0.148])
0,00 [0.000]

0,00 [0.000]

3,00 [0.118]

6,00 [0.236]

17,50 [0.689]

79,50 [3.130]

83,00 [3.268]

94,00 [3.701]

97,00 [3.819]

A(1:1)

A

P12,00 [0.472]

17,50 [0.689]

3,00 [0.118]

0,00 [0.000]
3,09 [0.122](INTERSECT
3,75 [0.148])
14,00 [0.551]

0,00 [0.000]

8X P2,39 [0.094]

TOP SIDE

48,50 [1.909]

94,00 [3.701]

79,50 [3.130]

72,00 [2.835]

65,00 [2.559]

-05
PCB

1,59 [0.063]

NOTES:
1) PLATING FINISH: GOLD-ENIG TOP & BOTTOM SIDES.
2) BOTTOM SIDE, SELECTIVE GOLD FIVE PADS OF CONNECTOR 30 MILS.

2X P1,50 [0.059]

97,00 [3.819]

,0

8

[4

.4
12
]

)

1:1

SHEET

FOX-ME-120

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-12

DATE

A

SIZE

SCALE

0.9
3 OF 3REV.

FOX
Z TOP/BOTT SOLAR PANEL

AMSAT

PADS, PIN 1 OFSAMTEC FSI-105-06-S-S-AD ON PCB STACK.
THICKER GOLD, SEE NOTE 2.

(1
12

BOTTOM SIDE

11,00 [0.433]

0,00 [0.000]
4,00 [0.157]

0,00 [0.000]
4,00 [0.157]

3,50 [0.138]

R1,6 [0.06]

CHAMFER 1,0 [0.04] X 45°

SEE NOTE 2.

P2,39 -5,0 DEEPY P 2,5 X 120°

7,0 [0.28]

3,33 [0.131]

0,00 [0.000]

1,0 [0.04]

3,00 [0.118]

0,00 [0.000]

3,50 [0.138]

4,0 [0.16]

5,0 [0.20]

SEE NOTE 2.

2X P2,39 THRU
Y P2,5 X 120°

CIRCULAR POCKET

P6,35 -5,0 DEEP

18,00 [0.709]

1,00 [0.039]

1:1

SHEET

FOX-ME-121

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-06

DATE

A

SIZE

SCALE

FOX
RAIL ENDS

CHAMFER 1,0 [0.04] X 45°

AMSATCHAMFER 1,0 [0.04] X 45°-01 +Z

2) STI TAP #2-56 MIN Z4, USING HELICOIL BOTTOMING TAP 02CBB.
INSTALL HELICOIL #2-56 X 1 DIA 358502CN0086,
USING HELICOIL INSTALLATION TOOL 551-02.
REMOVE TANG USING HELICOIL TANG-BREAKOFF TOOL 3695-02.
3) -01, -03, -09: CHEMICAL CONVERSION COAT PER MIL-DTL-5541 CLASS 3, ELECTRICALLY CONDUCTIVE CLEAR.

9,50 [0.374]

0,00 [0.000]

R1,0 [0.04]

R1,0 [0.04]

0,00 [0.000]

7,50 [0.295]

14,00 [0.551]

18,00 [0.709]

8,00 [0.315]

21,00 [0.827]

R1,0 [0.04]

NOTES:
1) -01, -03, -09 MATERIAL: 6061-T6

SEE NOTE 2.

P2,39 -5,0 DEEPY P 2,5 X 120°

1,00 [0.039]

4,0 [0.16]
7,50 [0.295]
11,00 [0.433]

CHAMFER 1,0 [0.04] X 45°

0,00 [0.000]

0,00 [0.000]
0,00 [0.000]
0,00 [0.000]
0,00 [0.000]

1,00 [0.039]

5,0 [0.20]
14,00 [0.551]

9,50 [0.374]

21,00 [0.827]

1.1
1 OF 6

REV.

1

1

QTY

1

2

ITEM
Parts List

PART NUMBERMCMASTER 84985A76

FOX-ME-121-03

DESCRIPTION#8-36 LONGSPRING PLUNGER W/LOCK,RAIL END, -Z W/SPRING

0,00 [0.000]

NO SIDE RECESSTAP #8-36 THRUSEE NOTE 4.

P3,45 THRU
Y P4,06 X 120°

0,00 [0.000]

3,75 [0.148]

3,75 [0.148]-03 -Z W/SPRING

SCALE

A

SIZE

1:1

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

SHEET

FOX-ME-121

DWG.NO.

RAIL ENDS
2013-06-06

DATE

MAKE SIMILAR TO -01 EXCEPT AS NOTEDNOTES:
4) INSTALL MCMASTER-CARR 84985A76
SPRING PLUNGER W/LOCK ELEMENT,
USING SPANNER WRENCH 3382A12.
SPRING HOUSING FLUSH WITH ALUMINUM;
BUTTON PROTRUDES ABOVE TOP,AND TAIL PROTRUDES OUT BOTTOM.

0,00 [0.000]

1,00 [0.039]

2,50 [0.098]

1.1
2 OF 6

REV.

R1,60 [0.063]

0,00 [0.000]

8,00 [0.315]

3,75 [0.148]

0,00 [0.000]

P2,69 [0.106]
DEBUR/C'SINK

0,00 [0.000]
0,00 [0.000]
0,00 [0.000]

3,75 [0.148]

3,75 [0.148]
3,75 [0.148]

CHAMFER 1,0 [0.04] X 45°

R4,76 [0.188] SLOT
2,60 [0.102] DEEP

DEBUR/C'SINK

1,00 [0.039]

0,00 [0.000]

1,00 [0.039]

2,50 [0.098]

SCALE

A

SIZE

1:1

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

SHEET

FOX-ME-121

DWG.NO.

RAIL ENDS
2013-06-06

DATE

MAKE SIMILAR TO -01 EXCEPT AS NOTED-09 -Z W/ PLUNGER HOLE

1.1
5 OF 6REV.

NOTES:5) -11 MATERIAL: BALCK DELRIN

0,00 [0.000]

0,80 [0.031]

9,10 [0.358]

P2,36 [0.093]

P5,00 [0.197]

SCALE

A

SIZE

1:1

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

SHEET

FOX-ME-121

DWG.NO.

RAIL ENDS
2013-06-06

DATE-11 SWITCH PLUNGER

1.1
6 OF 6REV.

16,23 [0.639]

8,61 [0.339]

0,00 [0.000]

38,46 [1.514]

30,84 [1.214]

NOTES:
1) SOURCE: SPACEQUEST, LTD. FAIRFAX, VA.
2) MATERIALS/PRODUCTS:
SOLAR CELL: SPECTROLAB UTJ, 28.3% 26.62CM^2
RTV: TBD
COVERGLASS: CERIA-DOPED GLASSINTERCONNECT: INVAR/KOVAR
3) APPLICATION NOTES:KEEP-OUT ZONE 1MM ALL SIDES TO PANEL EDGE, SOLDER PAD OR TRACE.
BONDED TO PCB USING NUSIL CV-2289-1 RTV OR EQUIVALENT.
FLOATING POSITIVE (+) INTERCONNECTS AN BE ADDED TO ANY OTHER EDGE.

FIXED NEGATIVE (-) INTERCONNECT,
OUT-OF-PLANE STRAIN RELIEF.

4,65 [0.183]

0,00 [0.000]

7,87 [0.310]

39,70 [1.563]

7,87 [0.310]-01 CIC

7,87 [0.310]

60,63 [2.387]

7,87 [0.310]

FIXED NEGATIVE (-) INTERCONNECT,
OUT-OF-PLANE STRAIN RELIEF,
BYPASS DIODE UNDERNEATH CELL.

69,11 [2.721]

53,01 [2.087]

1:1

SHEET

FOX-ME-122

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-04

DATE

A

SIZE

SCALE

FOX
UTJ CELL ICD

AMSAT

0.2
1 OF 2

REV.

-03 CIC W/ POSITIVE INTERCONNECT

4,65 [0.183]

0,00 [0.000]

0,00 [0.000]

12,00 [0.472]

19,62 [0.772]

POSITIVE (+) INTERCONNECT
IN-PLANE STRAIN RELIEF

DATE

1:1

SHEET

FOX-ME-122

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-04

SIZE

SCALE

A

FOX
UTJ CELL ICD

AMSAT-04 CIC W/ POSITIVE INTERCONNECT

0.2
2 OF 2REV.

NOTES:
1) MATERIAL: 316 STAINLESS STEEL
2) MAKE FROM GRAINGER 21YN73 OR EQUIVALENT.

MINIMAL CHAMFERAS REQ'D FOR THREAD

98,0 [3.86]

FOX
THREADED ROD
1:1

SHEET

FOX-ME-123

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-08-16

DATE

A

SIZE

SCALE

AMSAT

(#4-40 FIT CLASS 2A FULL LENGTH)

0.2
1 OF 1

REV.

19,05 [0.750]

P6,35 [0.250]

1:1

SHEET

FOX-ME-124

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-05-22

DATE

A

SIZE

SCALE

FOX
MAGNET

AMSAT

0.1
1 OF 1

REV.

70,00 [2.756]

P3,18 [0.125]

1:1

SHEET

FOX-ME-125

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-05-22

DATE

A

SIZE

SCALE

FOX
HYSTERESIS ROD

AMSAT

0.1
1 OF 1

REV.

-05
DIMS SAME AS -03 EXCEPT AS NOTED.
COPPER ALLOY 110 H04 (HARD),MCMASTER-CARR 8966K423.
GOLD PLATED.

-03

D

-07

D-D ( 2 : 1 )

D

2:1

SHEET

FOX-ME-126

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-05-04

DATE

A

SIZE

SCALE

FOX
ANTENNA POSTAMSATDIMS SAME AS -03 EXCEPT AS NOTED.
G10/FR4 ROD,MCMASTER-CARR 8669K891
OR EQUIVALENT.

P2,38 [0.094]

1,50 [0.059]

P2,38 [0.094]

0,00 [0.000]

0,00 [0.000]
1,50 [0.059]

BLACK DELRIN,MCMASTER-CARR 8576K11

20°C

C-C ( 2 : 1 )C-01

B-B ( 2 : 1 )B

DELETED

P4,0 [0.16]
P5,0 [0.20]

0,00 [0.000]

1,75 [0.069]

3,25 [0.128]

4,00 [0.157]

B

P2,39 THRU
Y P4,76 X 100°0.4
1 OF 1

REV.

TOP SIDE

FOX-ME-126-05
ANTENNA POST, COPPERSOLDERED INTO THRU HOLE

DEPLOY RESISTOR
VISHAY-DALE
RWR81S6R98FRB12

FOX-ME-126-07
ANTENNA POST, G10/FR4
BONDED INTO THRU HOLE

ISO VIEWANTENNA AREASCALE 2 : 1

P1mm BC WIREANTENNA STOP,

6,00 [0.236]

60,49 [2.382]

64,9 [2.56]

BOTTOM SIDE

-01 +Y (437MHZ RX ANTENNA POINTING +Z)
FOX-ME-128-01
ANTENNA, RX
LENGTH SHOWN CROPPED

DATE

1:1

SHEET

FOX-ME-127

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-11

SIZE

27,50 [1.083]
SCALE

A

0,00 [0.000]

39,38 [1.550]
CL OF PSU PCB

75,0 [2.95]

101,6 [4.00]
MMCX

0.7
1 OF 4REV.

FOX
Y SIDE SOLAR PANEL

AMSAT

0,00 [0.000]

TOP SIDE

FOX-ME-126-07
ANTENNA POST, DELRIN
BONDED INTO THRU HOLE

FOX-ME-128-03
ANTENNA, TX
LENGTH SHOWN CROPPEDP1MM BC WIRE

DEPLOY RESISTOR
VISHAY-DALE
RWR81S6R98FRB12ANTENNA STOP,

FOX-ME-126-05
ANTENNA POST, COPPERSOLDERED INTO THRU HOLE

6,00 [0.236]

60,49 [2.382]
64,9 [2.56]

DATE

1:1

SHEET

FOX-ME-127

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-11

SIZE

A

0,00 [0.000]

6,4 [0.25]
MMCX

39,38 [1.550]
CL OF PSU PCB

75,0 [2.95]
TEMP SENSOR

0.7
2 OF 4REV.

FOX
Y SIDE SOLAR PANEL

AMSAT
SCALE

BOTTOM SIDEISO VIEWANTENNA AREASCALE 2 : 1

53,50 [2.106]-03 -Y (144 TX ANTENNA POINTING IN -Z)

0,00 [0.000]

ANTENNA STOP

FOX-ME-122

1

1

1

1

1

1

2

2

QTY

5

6

7

8

9

10

20

21

ITEM
Parts List

PART NUMBER

DESCRIPTIONSpaceQuest UTJ

Ø1MM BC WIRETORSION SPRING ANTENNA

OHM

FOX-ME-128

WIREWOUND RESISTOR, 6.98

RWR81S6R98FRB12MMCX JACK, 50 OHM SMD

ANTENNA POST, G10/FR4

ANTENNA POST, COPPER

THERMISTOR, 0805

EDGE CARD CONNECTOR

PCB

VISHAY-DALE

MOLEX 73415-2061

FOX-ME-126-07

FOX-ME-126-05

MEC1-105-02-S-D-NP-A

SAMTEC

1

4

FOX-ME-127-05

1

1

1:1

SHEET

FOX-ME-127

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-11

DATE

A

SIZE

0.7
3 OF 4REV.

FOX
Y SIDE SOLAR PANEL

AMSAT
SCALE

1) SOLDER CONNECTOR, MMCX, RESISTOR, RF SMD COMPONENTS, THERMISTOR AND COPPER ANTENNA POST.
2) BOND G10/FR4 ANTENNA POSTS.
3) FILL CONNECTOR ALIGNMENT HOLES AS NECESSARY TO PREVENT VOID UNDER CIC.
4) BOND & SOLDER CICS.
5) SOLDER TORSION SPRING ANTENNA (ENTIRE LENGTH OF BENT LEG AND INTO THRU HOLE BUT NOT COIL)
AND STOP WIRE (BEND AS REQUIRED FOR PROPER DEPLOYED ANGLE).

ASSEMBLY INSTRUCTIONS-01 +Y (437MHZ RX ANTENNA POINTING +Z) OR -03 -Y (144 TX ANTENNA POINTING IN -Z)

0,00 [0.000]

4,00 [0.157]

P1,30 [0.051]

54,00 [2.126]

P2,69 [0.106]

8X

104,00 [4.094]

108,00 [4.252]

58,00 [2.283] SPRING LEG

78,50 [3.091]

50,25 [1.978] ANTENNA VIARESISTOR 50,52 [1.989]

44,00 [1.732] RESISTORPOST 40,50 [1.594]

40,50 [1.594] POSTRESISTOR 37,00 [1.457]

30,48 [1.200] RESISTOR
STOP 30,00 [1.181]

SPRING LEG 23,00 [0.906]

2,50 [0.098]

0,00 [0.000]

0,00 [0.000]

0,00 [0.000]

1,50 [0.059]

2,75 [0.108]

4,40 [0.173]

6,40 [0.252]

8,40 [0.331]

P1,30 [0.051]

99,60 [3.921]

101,60 [4.000]

103,60 [4.079]

105,25 [4.144]

106,50 [4.193]-05 PCB

1,59 [0.063]
BOTTOM SIDENOTES:
1) FLASH GOLD TOP & BOTTOM SIDES, ANY AVAILABLE AREAS.

TOP SIDE

81,00 [3.189]

51,00 [2.008] STOPANTENNA VIA 30,75 [1.211]

1:1

SHEET

FOX-ME-127

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-11

DATE

A

SIZE

SCALE

0.7
4 OF 4REV.

FOX
Y SIDE SOLAR PANELAMSATSEE DETAIL B

0,50 [0.020]

MATERIAL: BERYLLIUM COPPERFINISH: NO FINISH
COIL: RIGHT HAND, 3.875 WINDS.

-05 TORSION SPRING

6

35

5]
[2

±

5

P5,85 [0.230]

R0,75 [0.030]

5,27 [0.207]

DETAIL B
SCALE 2 : 1

]
.2
[0

SIDE VIEWSCALE 2 : 1

AUX VIEWSCALE 2 : 1

SCALE

A

SIZE

1,78 [0.070]

1:1

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

SHEET

FOX-ME-128

DWG.NO.

ANTENNA
2013-05-29

DATE

TIGHT AS POSSIBLE
R0,35 [0.014]

2,50 [0.098]

10,97 [0.432]

0.2
2 OF 3

REV.

11,00 [0.433]

3,30 [0.130]

0,00 [0.000]

P1,80 [0.071]

0,75 [0.030]

P4,45 [0.175]

17,00 [0.669]

P2,50 [0.098]

2,90 [0.114]

P2,31 [0.091]

P0,99 [0.039]

NOTES:
1) MATERIAL: NICKEL ALLOY 200/201
2) A FINGER-SIZED LOOP OF RED WIRE OR LACING CORD (NOT SHOWN) MAY BE USED THRU HOLE.

18,00 [0.709]

P1,00 [0.039]

1:1

SHEET

FOX-ME-130

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XXB0,1

2013-06-06

DATE

A

SIZE

SCALE

FOX
SAFE RBF

AMSAT

0.1
1 OF 4REV.

NOTES:
3) TO SAFE (DISABLE) ELECTRONICS:
FULLY INSERT INTO AUDIO JACK ON +X SIDE OF BATTERY BOARD(ROUND HOLE IN +X SOLAR PANEL).
4) TO ARM (ENABLE) ELECTRONICS:
FULLY REMOVE.

2.5MM STEREO AUDIO JACKOF BATTERY PCB

ON PCB-STACK(+X EDGE OF BATTERY PCB)

SAFE RBF

SCALE

A

SIZE

1:2

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

SHEET

0.1
2 OF 4REV.

SAFE RBF

FOX-ME-130

DWG.NO.

SAFE RBF
2013-06-06

DATE

ON FOX-1(ROUND HOLE IN +X SOLAR PANEL)NOTES:
5) COMPATIBLE WITH P-POD ALLOWABLE ENVELOPE.
6) REMOVE BEFORE FLIGHT (RBF) ITEM.

-Y FACE+Z FACEPROTRUDES 4,5 [0.18]
INTO 6,50 [0.256]
ALLOWABLE ENVELOPE
INSIDE P-POD+X FACE

SCALE

A

SIZE

1:2

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

SHEET

FOX-ME-130

DWG.NO.

SAFE RBF
2013-06-06

DATE

21,5 [0.85]
FULLY VISIBLE IN
P-POD ACCESS PORT
13.75 MM FROM RAIL,
WHETHER CUBESAT LOADEDINTO P-POD -Z OR +Z END FIRST

0.1
3 OF 4

REV.

12,7 [0.50](STOCK)TAPE OVERROUND HOLE
(UNUSED)TAPESCALE: 1:1

TAPE OVER
SQUARE CUTOUT(UNUSED)NOTES:
7) UMBILICAL HOLES TO BE COVERED FOR FLIGHT USING APPROVED 1ST SURF METAL TAPE.
FOR SAFE RBF, AND POSSIBLY ALSO THE MINI-USB, THIS MAY HAVE TO BE PERFORMED
THROUGH ACCESS PORT(S) INSIDE P-POD.

TAPE OVER
SQUARE CUTOUT(MINI-USB UMBILICAL)-X FACE

10 [0.4]+X FACE

SCALE

A

SIZE

1:2

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

SHEET

FOX-ME-130

DWG.NO.

SAFE RBF
2013-06-06

DATE

TAPE OVERROUND HOLE
(SAFE JACK)

0.1
4 OF 4REV.

AMSAT Fox-1 Engineering Documentation Update
Compiled by Jerry Buxton, N0JY
AMSAT Vice President - Engineeringn0jy@amsat.org
AMSAT, as an educational organization, would like to publicly release the majority of our design
documentation to serve as a learning tool to anyone interested in satellite development. However,this must be done in a specific way to meet the ITAR requirements. The information must first be
released via an openly available publication. We would also like to be able to discuss our satellite
projects with our own members, some of whom are not "US-persons" per ITAR. These AMSATSpace Symposium proceedings provide a convenient mechanism for the needed publication inorder to make this information public domain and allow us to communicate with our members.
While many of the Fox-1 documents were published in the Proceedings of the AMSAT-NA 30thSpace Symposium and AMSAT-NA Annual Meeting and the Proceedings of the AMSAT-NA 31stSpace Symposium and AMSAT-NA Annual Meeting, some of these documents have undergonechanges as the satellite design has progressed and evolved therefore the updated versions will be
reproduced in these 2014 Space Symposium proceedings. In addition, these proceedings alsopresent any new engineering documents that have been produced since the last publication.
Through publication in the three proceedings, the majority of the design documentation has now
been introduced to the public domain.

AMSAT Fox-1
System Requirements
Date: September 29, 2014
Version: Version 1.82

AMSAT Fox-1
System Requirements Specification
1 Introduction
This document specifies the system level technical requirements for the AMSAT Fox-1
satellite project. This 1 Unit CubeSat is a part of the AMSAT Fox program and includes a
subset of the technical capabilities envisioned for the overall program.
Fox-1 is specifically intended as a replacement for the failing AMSAT Echo (i.e. AO-51)
satellite. Echo has been the most widely used amateur satellite due to its ability to provide
basic radio communications with very simple ground station equipment. Its FM repeater
provides very wide geographical coverage allowing amateur radio operators tocommunicate over substantial distances using just a handheld transceiver (i.e. a walkietalkie) and a small handheld antenna. This so called "EasySat" mode is extremely
valuable in providing an introduction to satellite communications and is often used fordemonstrations given at schools, to scouting organizations and at amateur radio publicity
events. Fox-1 will not duplicate all of the features and modes of Echo but its primary
mission is to provide an FM Transponder in order to allow continued access to thisEasySat mode of communications.
In addition to its mission as a communications satellite, Fox-1 will host an experiment
payload. The satellite will reserve mass and volume for the experiment and will provide
DC power and a communications facility. The experiment is expected to be provided by
students at Penn State University – Erie through an AMSAT sponsored senior design
project.

Page 1 of 13

AMSAT Fox-1
System Requirements
1.1

Document History
DATE

VERSION

SUMMARY

October 5, 2011

1.0

From Draft E

October 8, 2011

1.01

Fix typos in sections 1.2 and 3.5

October 9, 2011

1.02

Add Requirements Tracking

October 23, 2011

1.03

Additional Requirements Tracking

February 21, 2012

1.04

Update Section 3 and Formatting changes

April 18, 2012

1.05

Correction in Section 4

April 22, 2012

1.06

Correct link in Section 1.4 item 2

April 29, 2012

1.1

Revised 3.12.3, 3.12.7, 3.12.8, 3.13.3,
3.13.4, figure 1 to remove RESET and add
IHU OFF and IHU ON commands

August 2, 2012

1.11

Added hidden text for requirements tracking
to be shown in System Design Specification

September 4, 2012

1.12

Added the previously missing “Table 6”label

October 17, 2012

1.2

Changed mode descriptions in 3.13.1 Table
6; changed 3.9.2, 3.9.3, 3.9.4, 3.9.5, 3.9.6,
3.9.7 to reflect IHU involvement; changed
COMMAND MODE to DATA MODE

April 25, 2013

1.3

3.10.2 Remove PA Temperature, add TX T
as RF Transmitter Temperature, OSC T as
referring to TX oscillator no longer
measured changed to read RX oscillator
only

August 20, 2013

1.4

Requirements 3.5.5, 3.6.1, 3.9.6, 3.10.2,
3.11.1, 3.12.4, 3.12.6, 3.13.7.1, 3.13.7.2,
3.13.8, 3.13.9 modified, removed or added
to reflect the evolving satellite design

January 10, 2014

1.5

Changes to 3.12.3, 3.12.4, 3.13.2, 3.13.5,
3.13.5.1, 3.13.5.2, 3.13.7, 3.13.7.3,
3.13.7.3.1, 3.13.7.3.2, 3.13.11, 3.13.12 to
add Safe Mode

January 20, 2014

1.6

Change 3.13.7.3 to go directly to Safe
Mode, remove 3.13.7.3.1 and 3.13.7.3.2

January 23, 2014

1.7

Modified 3.13.2 (figure 1), 3.13.11, added
3.13.11.1

February 10, 2014

1.71

Added “Experiments are powered off” toTable 6 under Safe Mode
Page 2 of 13

AMSAT Fox-1
System Requirements

DATE

VERSION

SUMMARY

April 17, 2014

1.72

Bring Table 5 commands in line with
Command and Control Document, remove
PSU reference from 3.12.8 and 3.12.9

August 16, 2014

1.8

Update to actual operating values 3.13.11,
3.13.11.1, 3.12.3, 3.13.1, 3.13.7, 3.13.7.1,
3.13.7.2

September 8, 2014

1.81

Update to actual operating values 3.9.3,
3,9,6, update Table 5, add 3.12.12 and3.12.13

September 29, 2014

1.82

Update 3.9.3, 3.9.4 to allow for variablehang timer

1.2 Document Scope
The purpose of this document is to specify the technical requirements of the satellite at
the system (i.e. "black box") level. It is intended to be used by the hardware, software andmechanical designers to develop the architecture/high-level design specifications. It isalso intended to be used for test planning and development.
1.3 Document Format
This document provides the requirements in numbered format. Each requirement is
assigned a unique number. Additional information such as comments or examples thatare provided for guidance or clarity is italicized to distinguish them from requirements.
1.4 References
1. AMSAT Fox-1, Concept of Operations, Version 1.0, September 19, 2011
2. CubeSat Design Specification Rev. 12. by The CubeSat Program Cal Poly SLO
available from: http://www.cubesat.org/images/developers/cds_rev12.pdf
3. Launch Services Program, Program Level Poly Picosatellite Orbital Deployer(PPOD) and CubeSat Requirements Document LSP-REQ-317.01 Revision Basic(from NASA)
4. ITURadio
Regulations,
Editionof2008.
availablefrom
http://www.itu.int/publ/R-REG-RR-2008/en

Page 3 of 13

AMSAT Fox-1
System Requirements

2 General Requirements
2.1

CubeSat Requirements

2.1.1 The satellite shall meet the requirements specified in the CubeSat Design
Specification Rev. 12.
2.1.2 The satellite shall meet the requirements specified in the NASA LSP-REQ317.01 Revision Basic.
2.1.3 The satellite shall meet the requirements for a 1 unit (single) CubeSat.
2.1.4 The satellite shall provide mass for an experiment payload up to 100 g.
2.1.5 The satellite shall provide volume for an experiment payload up to 95 x 95
x 15.7 mm.
2.2

Environmental Requirements

2.2.1 The satellite avionics shall be designed for -40C to +70C operating
temperature.
2.2.2 The satellite shall be designed to operate in a 650 km, sun-synchronous,
circular orbit.
2.2.3 The satellite shall be designed to tolerate the radiation environment inorbit.
2.3

Reliability Requirements

2.3.1 The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
2.4

RF Frequency Requirements

2.4.1 All RF transmitters shall meet or exceed the requirements specified in the
ITU Radio Regulations, Technical Characteristics, Volume 3, article 3.
2.4.2 All satellite uplinks shall be in the 70 cm band of the amateur satellite
service.
2.4.3 All satellite downlinks shall be in the 2 meter band within the amateur
satellite service.
2.4.4 All satellite transmitter and receiver frequencies shall deviate by no morethan 5 parts-per-million from the specified values including initial accuracy
and temperature variation.
2.4.5 All satellite frequencies shall be coordinated with the IARU.
Note that the band plan with the actual coordinated frequencies will be specified in a
separate document.

Page 4 of 13

AMSAT Fox-1
System Requirements

3 Functional Requirements
3.1

Antenna System

3.1.1 The satellite shall include a deployable antenna system.
3.2

Attitude Control

3.2.1 The satellite shall incorporate passive magnetic stabilization to align the
deployed antennas with the magnetic field of the earth.
3.3

Access Ports

3.3.1 The satellite shall include a "Remove Before Flight" pin as per the CubeSat
Design Specification.
3.3.2 The satellite shall include an umbilical port as per the CubeSat Design
Specification.
3.4

Pre-launch Features

3.4.1 The satellite battery and photovoltaic panels shall be electronicallydisconnected from the avionics when the "Remove Before Flight" pin is
inserted, regardless of the state of the deployment switch(es).
3.4.2 The satellite shall provide the means to charge the battery via the umbilicalport while integrated with the P-POD.
3.4.3 The satellite shall provide the means to run diagnostic tests via theumbilical port while integrated with the P-POD.
3.5

Power

3.5.1 The satellite shall produce electrical power from sunlight.
3.5.2 The satellite shall produce electrical power while in sunlight regardless oforientation and while tumbling or spinning.
3.5.3 The satellite shall produce sufficient average electrical power to operatecontinuously in the orbit of maximum eclipse.
3.5.4 The satellite shall provide sufficient battery capacity to operatecontinuously in the orbit of maximum eclipse.

Page 5 of 13

AMSAT Fox-1
System Requirements
3.6

Experiment3.6.1 The satellite shall provide DC power for experiment payloads.
3.6.2 The satellite shall provide a means to activate and deactivate theexperiment payloads.
3.6.3 The satellite shall provide a means to telemeter data from the experiment
payloads.
Note that the experiment payloads will be specified in a separate documents.
3.7

RF Uplink

3.7.1 The satellite shall include an FM uplink receiver.
3.7.2 The

receiver

shall

have

specifications

as

shown

in

Table

Table 1

Sensitivity
FM Deviation
Audio Bandwidth
Input Frequency Acceptance

3.8-120 dBm for 12 dB SINAD (min.)
5 kHz
3 kHz
Receiver shall accept signals that are off
frequency by ±2.5 kHz (min.)

RF Downlink

3.8.1 The satellite shall include an FM downlink transmitter.
3.8.2 The transmitter shall have specifications as shown in Table 2.
Table 2

Power Output
400 mW (min.)FM Deviation
5 kHz
Audio Bandwidth 3 kHz

Page 6 of 13

1.

AMSAT Fox-1
System Requirements
3.8.3 The transmitter shall provide a means to prevent over modulation.
3.9

FM Transponder

3.9.1 The satellite shall provide an FM transponder via the RF uplink and RF
downlink.
3.9.2 In Transponder Mode, the IHU shall detect the presence of a 67 Hz CTCSS
tone on the uplink.
3.9.3 In Transponder Mode, the downlink transmitter shall be keyed (i.e. PTT-on)
by the IHU for a minimum of 30 seconds following detection of the 67 Hz
CTCSS tone.
3.9.4 In Transponder Mode, the downlink transmitter shall stay on continuously
as long as the 67 Hz CTCSS tone is detected at least once during theperiod the transmitter is being keyed (i.e. PTT-on).
3.9.5 In Transponder Mode, the 67 Hz CTCSS tone is not required for a received
signal to be repeated on the downlink, once the transmitter has been
keyed.
3.9.6 In Transponder Mode, if the downlink transmitter has been un-keyed for aperiod of 2 minutes, the satellite shall send "HI THIS IS AMATEUR RADIOSATELLITE FOX 1" as a voice announcement on the downlink transmitter.
3.9.7 In the event of shutdown or failure of the IHU, the satellite shall default tosimple carrier operated repeater operation.
3.10 Telemetry Data
3.10.1 The satellite shall collect telemetry data.
3.10.2 The telemetry data shall include at a minimum, measured parameters asshown in Table 3.
Table 3

Parameter NameCELL VPANEL VTOTAL IPA I
BATTERY T
PANEL T
TX T
RX T

Description
Voltages of battery cells
Voltages of solar panels
Total DC current out of power system
DC current into RF power amp
Temperature of battery
Temperatures of solar panels
Temperature of RF transmitter card
Temperature of RF receiver card

Page 7 of 13

AMSAT Fox-1
System Requirements
3.10.3 The measured parameters shall be sampled at least every 15 seconds.
3.10.4 The minimum and maximum values of each of the measured parameters
shall be saved in non-volatile memory.
3.10.5 The telemetry data shall also include at a minimum, calculated parameters
as shown in Table 4.
Table 4

Parameter Name Description
UP TIME
Total seconds since avionics power-up or reset
SPIN
Satellite spin rate and direction
3.10.6 A telemetry frame shall include the current measured values, the saved
minimum and maximum values, and the current calculated values.
Note that the telemetry interface will be specified in a separate document.
3.11 Telemetry Transmission
3.11.1 The satellite shall send slow speed telemetry using FSK on the RF
downlink.
3.11.2 The FSK shall use the frequency spectrum below the audible range.
3.11.3 The telemetry shall be transmitted simultaneously with any transponder
communications.
3.11.4 The telemetry transmission shall include telemetry frames.
3.11.5 The telemetry transmission shall include experiment data.
3.12 Command Capability
3.12.1 The satellite shall provide the means to process commands sent via the
RF uplink from a ground control station.
3.12.2 The commands received via the RF uplink shall not be repeated on the
RF downlink.
3.12.3 The following commands shall be provided, as shown in Table 5.

Page 8 of 13

AMSAT Fox-1
System Requirements
Table 5

Command
SAFE MODE
INHIBIT TX
ENABLE TX
IHU OFFIHU ON
CLEAR
TRANSPONDER MODEDATA MODE
ENABLE AUTO-SAFE
DISABLE AUTO-SAFE

Operation
Enter Safe Mode
Inhibit RF transmission
Enable RF transmission
Power off IHUPower on IHUClear stored telemetry
Enter Transponder Mode
Enter Data Mode
Enable Auto-Safe Mode
Disable Auto-Safe Mode

3.12.4 A SAFE MODE command shall cause the satellite to enter the Safe Mode.
3.12.5 An INHIBIT TX command shall disable the RF transmitter.
3.12.6 An ENABLE TX command shall enable the RF transmitter.
3.12.7 An IHU OFF command shall cause the IHU System to power off.
3.12.8 An IHU ON command shall cause the IHU System to power on.
3.12.9 A CLEAR command shall cause the satellite to clear the saved minimum
and maximum telemetry parameter values.
3.12.10 A TRANSPONDER MODE command shall cause the satellite to enter
the Transponder Mode.
3.12.11 A DATA MODE command shall cause the satellite to enter the Data
Mode.
3.12.12 An ENABLE AUTO-SAFE command shall enable the auto-safe mode
state.
3.12.13 A DISABLE AUTO-SAFE command shall disable the auto-safe mode
state.
Note that the control interface will be specified in a separate document.
3.13 On-Orbit Operating Modes
3.13.1 The satellite shall provide on-orbit operating modes as shown in Table 6.
Table 6

Name
Startup Mode
Safe Mode

Description
Wait 50 minutes and deploy antennas
Wait 120 seconds then begin 10 second
beacon sequence
Experiments are powered off
Page 9 of 13

AMSAT Fox-1
System Requirements
Transponder Mode
Data Mode

FM transponder; PTT and low speed
telemetry via IHUFM transmitter; PTT and high speed
telemetry via IHUPage 10 of 13

AMSAT Fox-1
System Requirements

3.13.2 The satellite shall transition between modes as shown in Figure 1.

Figure 1. On-Orbit Operating Modes

Page 11 of 13

AMSAT Fox-1
System Requirements
3.13.3 Upon power-up of the avionics, the satellite shall begin operation from the"Power-up" state as shown in Figure 1.
3.13.4 An IHU ON Command shall cause the satellite to begin operation from the"Power-up" state as shown in Figure 1.
3.13.5 If the antennas have been deployed, the satellite shall determine whether
the last state was Safe Mode.
3.13.5.1 If the last state was Safe Mode the satellite shall enter Safe Mode.
3.13.5.2 If the last state was not Safe Mode the satellite shall enterTransponder Mode.
3.13.6 If the antennas have not been deployed, the satellite shall enter theStartup Mode.
3.13.7 In Startup Mode, the satellite shall wait 50 minutes, then deploy theantennas.
3.13.7.1 During the 50 minute wait the IHU shall flash a red LED.
3.13.7.2 During the 50 minute wait the IHU shall sound a 1 kHz beeping tone.
3.13.7.3 After the antennas have been deployed the satellite shall enter Safe
Mode.
3.13.8 In Transponder Mode, the transponder and the slow speed telemetry shallbe active.
3.13.9 In Data Mode, the high speed telemetry shall be active and thetransponder shall not be active. (i.e. signals that appear on the uplink shallnot be repeated on the downlink.)
3.13.10 If another Data Mode command is not received, the satellite shall
automatically enter Transponder Mode 24 hours after having entered Data
Mode.
3.13.11 In Safe Mode the satellite shall wait 120 seconds then transmit a 10
second beacon.
3.13.11.1 The 120 second wait and 10 second beacon cycle will be repeatedas long as the satellite is in Safe Mode.
3.13.12 The RF uplink shall be monitored for commands in all modes.

4 External Interface Documents
To fully specify the satellite technical requirements, the following documents
must also be provided;
1. IARU Coordinated Frequency Plan
2. Downlink Specification
3. Control Interface Specification
4. Experiment Payload Specifications
Page 12 of 13

AMSAT Fox-1
System Requirements

5 Summary
The Fox-1 satellite will be AMSAT's first CubeSat. Its primary mission is toprovide an FM Transponder communications capability. The secondary mission
is to host a university-provided experiment payload.

Page 13 of 13

AMSAT Fox-1
Avionics System Design Specification
Date: September 29, 2014
Version: 3.92

AMSAT Fox-1
Avionics System Design Specification
1 Introduction
This document contains the system level design specifications for the AMSAT Fox-1 satellite avionics
systems. It is driven by the System Requirements Specification and other documents provided by thedevelopers of the individual systems that make up the satellite system.
1.1. Document History
DATE

VERSION

SUMMARY

February 21, 2012

1.0

From Draft F

April 9, 2012

1.1

Add signal characteristics, update bus pin connections per System Team
input

April 17, 2012

1.2

Add external connector specification in sections 2.6, 2.12 and 2.14 andreferences in section 6

April 18, 2012

1.21

Add MMCX connectors gender

April 22, 2012

1.3

Minor corrections in signal characteristics, remove +Z antenna deploy
and sensor connections

July 10, 2012

2.0

Many revisions from PDR

July 11, 2012

2.01

One RBF pin removed from bus pin assignments, updated 2.1
interconnect diagram, updated 2.1 signal characteristics

July 21, 2012

2.1

Revised bus signals, bus pin assignments
Updated RF block diagram

July 22, 2012

2.11

Revision to some RF signal descriptions, change antenna/coax
connectors to UMCC type, updated RF block diagram, added driving andload system columns to signal characteristics

September 9, 2012

3.0

Major changes.

September 11, 2012

3.01

Defunct IHU block diagram pending update

September 12, 2012

3.1

Added PCB volume requirements

September 23, 2012

3.11

Change TX PTT to RX PTT, -Z Deploy switches to TX, update figures
and tables accordingly

September 26, 2012

3.12

Update bus and pin assignment drawings

September 27, 2012

3.13

Update bus pin assignment drawings

September 30, 2012

3.14

Update RF block diagram to remove ITAR notice

October 17, 2012

3.15

Import changes to requirements from System Requirements

February 17, 2013

3.2

Incorporate system bus signal nomenclature and pin assignmentchanges

February 28, 2013

3.3

MEC connector changed orientation (flipped) on +X -X +Y -Y panels.

Page 1 of 54

AMSAT Fox-1
Avionics System Design Specification
DATE

VERSION

SUMMARY

March 28, 2013

3.4

Add second –Z PPOD deploy switch (pin 54), PPOD deploy switches
now on TX system card

March 31, 2013

3.41

Updates to the TX, RX, IHU, and BUS pin diagrams.

March 31, 2013

3.42

Adjusted RESERVED pin colors only

April 21, 2013

3.43

Addition of RX Frequency Control, TX Frequency Control, and Sensor
Power signals
Pin reassignments:
Moved pins 52 and 54 to pins 33 and 35 respectively
Moved pins 40 and 42 to pins 29 and 42 respectively
Added the above new signals to pins 42, 40, and 38 respectively

April 25, 2013

3.5

Update per System Requirements 3.10.2 changes. Updated bus
connection pin assignments, bus interconnect diagram, and system bus
signal characteristics account removal of TX OSC Temp and TX PA
Temp and addition of TX Temperature

June 26, 2013

3.6

Add requirements for PSU and BATT1 CPU reset from RX Command
Data, updated IHU block diagram

July 24, 2013

3.7

Add ALERT signal, SENSOR POWER signal, remove RBF2, rename
RBF1 to Solar Safe N, remove RX Command Data connection fromBATT1, flip MEC connector orientation on +X, -X, +Y, -Y panels, update
ME-113 mechanical drawings

August 26, 2013

3.8

Rename RX OSC TEMP to RX Temperature, add Initial Surge Current
Limits for certain systems, move Command Decoder to IHU system (buspin changes), update some bus nomenclature, update System
Requirements for each system per changes to the System Requirements

August 27, 2013

3.81

Correct source and destination for RX Command Strobe in Table 1

September 17, 2013

3.82

Add (move) RSSI to Pin 10, rename Pin 32 as RX CD, add Solar Power
A and Solar Power B to pins 55 and 56, update TX Block Diagram,
remove RX Command Data connection from PSU, update hyperlinks.

October 8, 2013

3.83

Remove IHU AUDIO OUT 2, RX AUDIO 2 signals, rename IHU AUDIOOUT 1 to IHU AUDIO OUT, RX AUDIO 1 to RX AUDIO.

November 11, 2013

3.84

Updated IHU Block Diagram

January 23, 2014

3.85

Add Sensor Power connection to PSU

January 23, 2014

3.86

Several text (requirements) changes to match recent System
Requirements change for Safe Mode.

April 27, 2014

3.87

Add PCB plating requirements for TX, RX, IHU, PSU, BATT, EXP
systems

May 29, 2014

3.88

Correct 6.7 to read PSU System

August 16, 2014

3.9

Updates to 5.1, 6.1 to match updated system requirements

August 20, 2014

3.91

Correct 5.1 to show 120 seconds for Safe Mode beacon

September 29, 2014

3.92

Update PSU block diagram, add receiver block diagram, update
commands in 5.1, update instances of system requirements 3.9.3, 3.9.4,
3.9.6

Page 2 of 54

AMSAT Fox-1
Avionics System Design Specification
1.2. Document Scope
The purpose of this document is to specify the avionics systems and their connections to each other and toexternal components for the satellite. It is intended to be used by the hardware, software, and mechanicaldesigners to develop the architecture and interconnections for the satellite avionics systems.
1.3. Document Format
This document provides these elements in a numbered format. The numbered sections specify each major
system in the satellite while numbered items for each system specify the external connections required andthe number of lines for each connection. Satellite bus and external connections are further described infigures and tables.
Where System Requirements are reproduced their numbers are from the AMSAT Fox-1 System
Requirements Specification.
1.4. References
1. AMSAT Fox-1 ConOps
2. AMSAT Fox-1 System Requirements Specification
3. AMSAT Fox-1 Bus (Signal Connections Diagram)
4. AMSAT Fox-1 Bus Pin Assignment
5. AMSAT Fox-1 Avionics System Design Specification Spreadsheet
6. AMSAT FOX-ME-120_Z_TOPBOTT_SOLAR_PANEL.pdf
7. AMSAT FOX-ME-127_Y_SIDE_SOLAR_PANEL.pdf

Page 3 of 54

AMSAT Fox-1
Avionics System Design Specification
Contents
1 Introduction ............................................................................................................................................. 1
2 Avionics System Bus Signals, Characteristics, and Connections ................................................................ 5
3 RF Transmitter System ............................................................................................................................. 8
4 RF Receiver System ................................................................................................................................ 14
5 Internal Housekeeping Unit (IHU) System .............................................................................................. 18
6 Power Supply System (PSU).................................................................................................................... 24
7 Battery System ........................................................................................................................................ 36
8 Experiment Payload Systems 1 through 4................................................................................................ 41
9 System Block Diagrams Reference .......................................................................................................... 47
10 System Interconnection References ....................................................................................................... 51

Page 4 of 54

AMSAT Fox-1
Avionics System Design Specification
2 Avionics System Bus Signals, Characteristics, and Connections

Figure 1: Interconnect Diagram

Page 5 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 1: System Bus Signal Characteristics
Type

Voltage

Source System

1

Pin

SPI1 NSS

Nomenclature

Digital

Note¹

IHU

2

TX PA Current

Analog0 - 3.0 V

TX

3

SPI1 SCK

Digital

Note¹

IHU

4

TX Temperature

Analog0 - 3.0 V

TX

5

SPI1 MISO

Digital

Note¹

IHU

6

Experiment 4 Thermistor

Analog

N/A

EXP 4

7

SPI1 MOSI

Digital

Note¹

IHU

8

RX Temperature

Analog0 - 3.0 V

RX

9Serial RXD

Digital

3.0 V

EXP 1-4

10

RSSI

Analog0 - 3.0 V

RX

11Serial TXD

Digital

3.0 V

IHU

12

IHU Audio Out

Analog0 - 3 V (audio)

IHU

13

Experiment Enable 1

Digital14

Not Used

15

Experiment Enable 2

16

RX Command Data 0

17
18

Load Z
30 - 60 kΩ

Load System

Notes

EXP 1-4

SPI Standard, IHU Master

IHU
EXP 1-430 - 60 kΩ
N/A
30 - 60 kΩ
30 - 60 kΩ

SPI Standard, IHU Master

IHU

Thermistor Circuit

EXP 1-4

SPI Standard, IHU Master

IHU

Temperature from Experiment 4 position

EXP 1-4

SPI Standard, IHU Master

IHU

Thermistor Circuit

IHU

Async, Mark HighIHU

Received Signal Strength Indication

EXP 1-4

Async, Mark HighTX

For 5 kHz deviation, 10 Hz - 7 kHz bandwidth

IHU

EXP 1-4

HIGH = Enable EXP 1

Digital

IHU

EXP 2

Digital

IHU

Experiment Enable 3

DigitalIHURX Command Data 1

DigitalIHU

19Experiment Enable 4

DigitalIHU

20RX Command Data 2

DigitalIHU

21Not Used22

RX Command Data 3
I²C1 SCL

DigitalRX Command Strobe
I²C1 SDA

Digital25
26

IHU RF Control

Digital27

Not Used28

IHU PTT

Digital29

Solar Safe N

Switch30

RF TX Active

Digital31

Alert Signal

Digital32

RX CD

Digital33-Z Deploy Switch 1

Switch

N/A

TX

34

RX Audio

Analog0 - 3 V (audio)35-Z Deploy Switch 2

SwitchN/A36

Not Used
I²C2 SCL

23
24

37

DigitalDigital> 10 kΩ unbal.

Note¹

HIGH = Enable EXP 3

EXP 4

HIGH = Enable EXP 4
HIGH = IHU off

IHU

TX

(Most Significan Bit) HIGH = Inhibit Transmit
I²C Standard, IHU Master

IHU

HIGH = Command Data change

IHU

I²C Standard, IHU Master
HIGH = IHU Controls RF
LOW = Standalone Analog Transponder

IHU

TX

IHU
N/A

EXP 3

Not Used on Fox-1A

IHU
Note¹

HIGH = Enable EXP 2(Least Significant Bit) Not Used on Fox-1A

TX

HIGH = TRANSMIT

PSU

N.O. for operation

TX

IHU

HIGH = RF TX on

IHU

BATT

BATT

N/A

RX

TX IHUHIGH = valid receive signal

PSU/BATT

N.O. when deployedRX

N/A> 10 kΩ unbal.

IHU

10 Hz - 7 kHz bandwidth

TX

N/A

PSU/BATT

N.O. when deployed

Digital

Note¹

IHU

PSU/BATTI²C Standard, IHU Master

Analog+3 VDCIHU

TX RX BATT EXP4

Power for analog telemetry sensors

39

Sensor Power
I²C2 SDA

Digital

Note¹

IHU

PSU/BATTI²C Standard, IHU Master40

TX Frequency Control

DigitalIHU

TX

Not Used on Fox-1A

41+Z Thermistor

Analog42

RX Frequency Control

Digital

43-Z Thermistor

AnalogN/A

44-Y Antenna Deploy

AnalogVbatt

45+Z CIC

Power

N/A

46

-Y Antenna Sensor

Switch47-Z CIC

48
49

38

N/A

EXP 4

N/A

PSU
PSU

IHU

N/A
7 Ω resistor

EXP 4

N/A

PSU

N/A

PSU

N.O.

IHU

Power

N/A

TX

N/A

PSU

+Y Antenna Sensor

Switch

N/A

PSU

N.O.

Umbilical USBP

Digital50+Y Antenna Deploy

Analog51

Umbilical USBM

DigitalBATT

IHU

USB Standard

52

Not Used

53

Umbilical Power Active

DigitalBATT

IHU

HIGH = Running on Umbilical Port Power54

Not Used

55

Solar Power A

Power

Vbatt

PSU

BATT

56

Solar Power B

Power

Vbatt

PSU

BATT

57

Vbatt

Power Bus 3.3 - 4.2 VDC

BATT/PSU

ALL

58

Vbatt

Power Bus 3.3 - 4.2 VDC

BATT/PSU

ALL

59

Vbatt

Power Bus 3.3 - 4.2 VDC

BATT/PSU

ALL

60

Vbatt

Power Bus 3.3 - 4.2 VDC

BATT/PSU

ALL

IHU
TX

RX

BATT
Vbatt

IHU

7 Ω resistor

Not Used on Fox-1A

PSU
N.O. when deployed

IHU

N.O. when deployed

IHU

USB Standard

PSU

Version 2.96
Note¹ All SPI and I²C signals are 3.0 V levels

All Digital signals are 3.0 V CMOS logic levels high impedance load unless otherwise noted

Page 6 of 54

AMSAT Fox-1
Avionics System Design Specification

Figure 2: Complete Bus Connection Pin Assignments

Page 7 of 54

AMSAT Fox-1
Avionics System Design Specification
3 RF Transmitter System
3.1 System Requirements Applicable to RF Transmitter System
2.2.1
2.2.3
2.3.1
2.4.1
2.4.3
2.4.4
2.4.5
3.8.1
3.8.2

The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
All RF transmitters shall meet or exceed the requirements specified in the ITU Radio Regulations,Technical Characteristics, Volume 3, article 3.
All satellite downlinks shall be in the 2 meter band within the amateur satellite service.
All satellite transmitter and receiver frequencies shall deviate by no more than 5 parts-per-million
from the specified values including initial accuracy and temperature variation.
All satellite frequencies shall be coordinated with the IARU.
The satellite shall include an FM downlink transmitter.
The transmitter shall have specifications as shown in Table 2.
Power Output
400 mW (min.)FM Deviation

5 kHz

Audio Bandwidth 3 kHz
3.8.3
3.9.1
3.9.3
3.9.5
3.9.7
3.10.1
3.10.2The transmitter shall provide a means to prevent over modulation.
The satellite shall provide an FM transponder via the RF uplink and RF downlink.
In Transponder Mode, the downlink transmitter shall be keyed (i.e. PTT-on) by the IHU for aminimum of 30 seconds following detection of the 67 Hz CTCSS tone.
In Transponder Mode, the 67 Hz CTCSS tone is not required for a received signal to be repeated on
the downlink, once the transmitter has been keyed.
In the event of shutdown or failure of the IHU, the satellite shall default to simple carrier operated
repeater operation.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card
Page 8 of 54

AMSAT Fox-1
Avionics System Design Specification
RX T
3.10.33.11.1
3.11.2
3.11.33.12.1
3.12.2
3.12.33.12.53.13.83.13.9Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.
The satellite shall send slow speed telemetry using FSK on the RF downlink.
The FSK shall use the frequency spectrum below the audible range.
The telemetry shall be transmitted simultaneously with any transponder communications.
The satellite shall provide the means to process commands sent via the RF uplink from a groundcontrol station.
The commands received via the RF uplink shall not be repeated on the RF downlink.
The following commands shall be provided, as shown in Table 5.
CommandOperation
SAFE MODE

Enter Safe Mode

INHIBIT

Inhibit RF transmission

IHU OFFPower off IHU & PSU

IHU ONPower on IHU & PSU

CLEAR

Clear stored telemetry

TRANSPONDER MODE

Enter Transponder Mode

DATA MODE

Enter Data Mode

An INHIBIT command shall cause the satellite to cease RF transmissions.
In Transponder Mode, the transponder and the slow speed telemetry shall be active.
In Data Mode, the high speed telemetry shall be active and the transponder shall not be active. (i.e.
signals that appear on the uplink shall not be repeated on the downlink.)

Page 9 of 54

AMSAT Fox-1
Avionics System Design Specification
3.2 Initial Surge Current Limits
3.2.1 The RF Transmitter design shall limit initial inrush current to 2.5 Amperes.
3.3 Volume Requirements Applicable to RF Transmitter System
3.3.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 5 mm from the –Z surface of the PC
board.
3.3.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
3.4 Interface Control Documents Applicable to RF Transmitter System
AMSAT Fox-1 IHU to RF System Interface Control Document
3.5 PCB Plating Requirements Applicable to RF Transmitter System
3.5.1 ENIG then selective flash gold four mounting pads.

Page 10 of 54

AMSAT Fox-1
Avionics System Design Specification
3.6 RF Transmitter System PCB Bus Connections

Figure 3: RF Transmitter System Bus Connection Pin Assignments

Page 11 of 54

AMSAT Fox-1
Avionics System Design Specification
3.7 RF Transmitter System PCB External Connections
3.7.1 2 meter band RF output, coaxial cable to Transmit Antenna
3.7.2 Spacecraft deployment switches cable(s) TBR
3.7.3 Three connections via Samtec FSI-105-06-L-S-AD connector
3.7.3.1 1 contact -Z Solar Panel Thermistor
3.7.3.2 1 contact -Z Solar Panel CIC +3.7.3.3 1 contact common or - for above four connections
Table 2: External Connection Signal Characteristics
External
Connection
CoaxialCable

Nomenclature
2 meter Antenna ≈ 145.9
MHz

Type
RF

Voltage/Power Source System Load Z
Bus Pin
0 to +30
2 meter
50 Ω unbal.
N/A
dBm
Antenna

Table 3: -Z PCB face FSI-105-06-L-S-AD connector mates to pads on –Z Solar Panel
Pin

Nomenclature

1-Z Thermistor

2

N/C

3

-Z Solar Panel Common

4

N/C

5

-Z CICType

Voltage

Source System

Load Z

Load System

Bus Pin

Analog

N/A

N/A

N/A

PSU

43
Ground
Plane

Power

N/A

N/A

Page 12 of 54

N/A

PSU

47

AMSAT Fox-1
Avionics System Design Specification

Figure 4: RF Transmitter System FSI-105-06-L-S-AD Connection Pin
Assignments

Page 13 of 54

AMSAT Fox-1
Avionics System Design Specification
4 RF Receiver System
4.1 System Requirements Applicable to RF Receiver System
2.2.1
2.2.3
2.3.1
2.4.2
2.4.5
3.7.1
3.7.2

The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
All satellite uplinks shall be in the 70 cm band of the amateur satellite service.
All satellite frequencies shall be coordinated with the IARU.
The satellite shall include an FM uplink receiver.
The receiver shall have specifications as shown in Table 1.
Sensitivity-120 dBm for 12 dB SINAD (min.)FM Deviation

5 kHz

Audio Bandwidth

3 kHz

Input Frequency Acceptance Receiver shall accept signals that are off
frequency by ±2.5 kHz (min.)
3.8.3
3.9.1
3.9.7
3.10.1
3.10.2

3.10.33.12.2
3.13.12

The transmitter shall provide a means to prevent over modulation.
The satellite shall provide an FM transponder via the RF uplink and RF downlink.
In the event of shutdown or failure of the IHU, the satellite shall default to simple carrier operated
repeater operation.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card

RX T

Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.
The commands received via the RF uplink shall not be repeated on the RF downlink.
The RF uplink shall be monitored for commands in all modes.
Page 14 of 54

AMSAT Fox-1
Avionics System Design Specification
4.2 Initial Surge Current Limits
4.2.1 The RF Receiver design shall limit initial inrush current to 0.1 Amperes.
4.3 Volume Requirements Applicable to RF Receiver System
4.3.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
4.3.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
4.4 Interface Control Documents Applicable to RF Receiver System
AMSAT Fox-1 IHU to RF System Interface Control Document
4.5 PCB Plating Requirements Applicable to RF Receiver System
4.5.1 ENIG then selective flash gold four mounting pads.

Page 15 of 54

AMSAT Fox-1
Avionics System Design Specification
4.6 RF Receiver System PCB Bus Connections

Figure 5: RF Receiver System Bus Connection Pin Assignments

Page 16 of 54

AMSAT Fox-1
Avionics System Design Specification
4.7 RF Receiver System PCB External Connections
4.7.1 70cm band RF input, coaxial cable to Receive Antenna
Table 4: RF Receiver System External Connection Signal Characteristics
External
Connection
CoaxialCable

NomenclatureType

70 cm RF Input 437 MHz

RF

Voltage/Power Source System
Load Z-60 dBmto -140 70 cm Antenna 50 Ω unbal.
dBm

Page 17 of 54

Bus Pin
N/AAMSAT Fox-1
Avionics System Design Specification
5 Internal Housekeeping Unit (IHU) System
5.1 System Requirements Applicable to Internal Housekeeping Unit (IHU) System
2.2.1
2.2.3
2.3.1
3.3.2
3.4.3
3.6.2
3.6.3
3.9.2
3.9.3
3.9.4

3.9.5
3.9.6

3.9.7
3.10.1
3.10.2

3.10.33.10.4The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
The satellite shall include an umbilical port as per the CubeSat Design Specification.
The satellite shall provide the means to run diagnostic tests via the umbilical port while integrated
with the P-POD.
The satellite shall provide a means to activate and deactivate the experiment payloads.
The satellite shall provide a means to telemeter data from the experiment payloads.
In Transponder Mode, the IHU shall detect the presence of a 67 Hz CTCSS tone on the uplink.
In Transponder Mode, the downlink transmitter shall be keyed (i.e. PTT-on) by the IHU for aminimum of 30 seconds following detection of the 67 Hz CTCSS tone.
In Transponder Mode, the downlink transmitter shall stay on continuously as long as the 67 Hz
CTCSS tone is detected at least once during the period the transmitter is being keyed (i.e. PTTon).
In Transponder Mode, the 67 Hz CTCSS tone is not required for a received signal to be repeatedon the downlink, once the transmitter has been keyed.
In Transponder Mode, if the downlink transmitter has been un-keyed for a period of 2 minutes, thesatellite shall send "HI THIS IS AMATEUR RADIO SATELLITE FOX 1" as a voiceannouncement on the downlink transmitter.
In the event of shutdown or failure of the IHU, the satellite shall default to simple carrier operated
repeater operation.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card

RX T

Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.
The minimum and maximum values of each of the measured parameters shall be saved in nonPage 18 of 54

AMSAT Fox-1
Avionics System Design Specification

3.10.53.10.6
3.11.1
3.11.2
3.11.33.11.43.11.53.12.1
3.12.33.12.43.12.53.12.6
3.12.73.12.83.12.93.12.10

volatile memory.
The telemetry data shall also include at a minimum, calculated parameters as shown in Table 4.
Parameter Name Description
UP TIME

Total seconds since avionics power-up or reset

SPIN

Satellite spin rate and direction

A telemetry frame shall include the current measured values, the saved minimum and maximum
values, and the current calculated values.
The satellite shall send slow speed telemetry using FSK on the RF downlink.
The FSK shall use the frequency spectrum below the audible range.
The telemetry shall be transmitted simultaneously with any transponder communications.
The telemetry transmission shall include telemetry frames.
The telemetry transmission shall include experiment data.
The satellite shall provide the means to process commands sent via the RF uplink from a groundcontrol station.
The following commands shall be provided, as shown in Table 5.
CommandOperation

SAFE MODE

Enter Safe Mode

INHIBIT TX

Inhibit RF transmission

ENABLE TX

Enable RF transmission

IHU OFFPower off IHUIHU ONPower on IHU

CLEAR

Clear stored telemetry

TRANSPONDER MODE

Enter Transponder Mode

DATA MODE

Enter Data Mode

ENABLE AUTO-SAFE

Enable Auto-Safe Mode

DISABLE AUTO-SAFE

Disable Auto-Safe Mode

A SAFE MODE command shall cause the satellite to enter the Safe Mode.
An INHIBIT TX command shall disable the RF transmitter.
An ENABLE TX command shall enable the RF transmitter.
An IHU OFF command shall cause the IHU System to power off.
An IHU ON command shall cause the IHU System to power on.
A CLEAR command shall cause the satellite to clear the saved minimum and maximum telemetry
parameter values.
A TRANSPONDER MODE command shall cause the satellite to enter the Transponder Mode.
Page 19 of 54

AMSAT Fox-1
Avionics System Design Specification
3.12.113.12.123.12.133.13.1

3.13.2
3.13.33.13.4A DATA MODE command shall cause the satellite to enter the Data Mode.
An ENABLE AUTO-SAFE command shall enable the auto-safe mode state.
A DISABLE AUTO-SAFE command shall disable the auto-safe mode state.
The satellite shall provide on-orbit operating modes as shown in Table 6.
Name
Description
Startup Mode

Wait 45 minutes and deploy antennas

Safe Mode

Wait 120 seconds then begin 10 second
beacon sequence

Transponder Mode

FM transponder; PTT and low speed
telemetry via IHU

Data Mode

FM transmitter; PTT and high speed
telemetry via IHU

The satellite shall transition between modes as shown in Figure 1.
Upon power-up of the avionics, the satellite shall begin operation from the "Power-up" state as
shown in Figure 1.
An IHU ON Command shall cause the satellite to begin operation from the "Power-up" state as
shown in Figure 1.

Page 20 of 54

AMSAT Fox-1
Avionics System Design Specification

3.13.53.13.5.1
3.13.5.2
3.13.63.13.73.13.7.1
3.13.7.2
3.13.7.3
3.13.83.13.93.13.103.13.113.13.11.1
3.13.12

If the antennas have been deployed, the satellite shall determine whether the last state was Safe
Mode.
If the last state was Safe Mode the satellite shall enter Safe Mode
If the last state was not Safe Mode the satellite shall enter Transponder Mode.
If the antennas have not been deployed, the satellite shall enter the Startup Mode.
In Startup Mode, the satellite shall wait 50 minutes, then deploy the antennas.
During the 50 minute wait the IHU shall flash a red LED.
During the 50 minute wait the IHU shall sound a 1 kHz beeping tone.
After the antennas have been deployed the satellite shall enter Safe Mode.
In Transponder Mode, the transponder and the slow speed telemetry shall be active.
In Data Mode, the high speed telemetry shall be active and the transponder shall not be active. (i.e.
signals that appear on the uplink shall not be repeated on the downlink.)
If another Data Mode command is not received, the satellite shall automatically enter Transponder
Mode 30 minutes after having entered Data Mode.
In Safe Mode the satellite shall wait 120 seconds then transmit a 10 second beacon.
The 120 second wait and 10 second beacon cycle will be repeated as long as the satellite is in Safe
Mode.
The RF uplink shall be monitored for commands in all modes.

Page 21 of 54

AMSAT Fox-1
Avionics System Design Specification
5.3 Initial Surge Current Limits
5.3.1 The IHU design shall limit initial inrush current to 0.1 Amperes.
5.4 Volume Requirements Applicable to IHU System
5.4.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
5.4.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
5.5 Interface Control Documents Applicable to IHU System
AMSAT Fox-1 IHU to RF System Interface Control Document
AMSAT Fox-1 IHU to PSU Interface Control Document
AMSAT Fox-1 IHU to Battery Interface Control Document
AMSAT Fox-1 IHU to Attitude Determination Experiment Interface Control Document
AMSAT Fox-1 IHU to Experiment 1 Interface Control Document
AMSAT Fox-1 IHU to Experiment 4 Interface Control Document
5.6 PCB Plating Requirements Applicable to IHU System
5.6.1 ENIG then selective flash gold four mounting pads.

Page 22 of 54

AMSAT Fox-1
Avionics System Design Specification
5.7 Internal Housekeeping Unit (IHU) System PCB Bus Connections

Figure 6: IHU System Bus Connection Pin Assignments

Page 23 of 54

AMSAT Fox-1
Avionics System Design Specification
6 Power Supply System (PSU)
6.1 System Requirements Applicable to Power Supply System (PSU)

2.2.1
2.2.3
2.3.1
3.3.1
3.4.1

3.4.2
3.5.1
3.5.2
3.5.3
3.5.4
3.6.1
3.10.1
3.10.2

3.10.33.13.7.1

The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
The satellite shall include a "Remove Before Flight" pin as per the CubeSat Design Specification.
The satellite battery and photovoltaic panels shall be electronically disconnected from the avionics
when the "Remove Before Flight" pin is inserted, regardless of the state of the deployment
switch(es).
The satellite shall provide the means to charge the battery via the umbilical port while integrated
with the P-POD.
The satellite shall produce electrical power from sunlight.
The satellite shall produce electrical power while in sunlight regardless of orientation and whiletumbling or spinning.
The satellite shall produce sufficient average electrical power to operate continuously in the orbit ofmaximum eclipse.
The satellite shall provide sufficient battery capacity to operate continuously in the orbit ofmaximum eclipse.
The satellite shall provide DC power for experiment payloads.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card

RX T

Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.
During the 45 minute wait the IHU shall flash a red LED.

Page 24 of 54

AMSAT Fox-1
Avionics System Design Specification
6.2 Initial Surge Current Limits
6.2.1 The PSU design shall limit initial inrush current to 0.1 Amperes.
6.3 Volume Requirements Applicable to PSU System
6.3.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
6.3.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 3.0 mm from the +Z surface of the PC
board within the area 0 to 4.0 mm from the +Y and +X edges of the board, and 6.0 mm from the +Z
surface of the PC board in the rest of the board area.
6.4 Interface Control Documents Applicable to PSU System
AMSAT Fox-1 IHU to PSU Interface Control Document
6.5 PCB Plating Requirements Applicable to PSU System
6.5.1 ENIG then selective flash hard gold 30 micro-inch four mounting pads and four edge fingers.

Page 25 of 54

AMSAT Fox-1
Avionics System Design Specification
6.6 Power Supply System (PSU) PCB Bus Connections

Figure 7: PSU Bus Connection Pin Assignments

Page 26 of 54

AMSAT Fox-1
Avionics System Design Specification
6.7 Power Supply System (PSU) PCB External Connections
6.7.1 Three connections to +X Solar Panel using Samtec MEC1-105-02-L-D-NP-A connector
6.7.1.1 1 contact +X Solar Panel Thermistor
6.7.1.2 1 contact +X Solar Panel CIC +6.7.1.3 1 contact common or - for above two connections
6.7.2 Three connections to -X Solar Panel using Samtec MEC1-105-02-L-D-NP-A connector
6.7.2.1 1 contact -X Solar Panel Thermistor
6.7.2.2 1 contact -X Solar Panel CIC +6.7.2.3 1 contact common or - for above two connections
6.7.3 Five connections to +Y Solar Panel using Samtec MEC1-105-02-L-D-NP-A connector
6.7.3.1 1 contact +Y Solar Panel Thermistor
6.7.3.2 1 contact +Y Solar Panel CIC +6.7.3.3 1 contact TX Antenna Deploy
6.7.3.4 1 contact TX Antenna Sensor
6.7.3.5 1 contact common or - for above connections
6.7.4 Five connections to -Y Solar Panel using Samtec MEC1-105-02-L-D-NP-A connector
6.7.4.1 1 contact -Y Solar Panel Thermistor
6.7.4.2 1 contact -Y Solar Panel CIC +6.7.4.3 1 contact RX Antenna Deploy
6.7.4.4 1 contact RX Antenna Sensor
6.7.4.5 1 contact common or - for above connections
6.7.5 All PCB edges that connect to solar panel MEC1-105-02-L-D-NP-A connectors shall havecontact pads on the PCB for all connector pins, whether connected to a trace or not.

Page 27 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 5: +X PCB edge mates to MEC1-105-02-L-D-NP-A connector on +X Solar Panel
Pin

Nomenclature

Type

Voltage

Source System

Load ZBus Pin

1

N/C

2
3

+X Solar Panel Thermistor
N/C

Analog

N/A

N/A

N/A

N/A

4
5

N/C
N/C

6

+X Solar Panel Common
N/C

7
8
9
10

Ground
Plane

N/C
N/C
+X Solar Panel CIC (+)

Power

N/A

Page 28 of 54

N/A

N/A

N/A

AMSAT Fox-1
Avionics System Design Specification

Figure 8: PSU System +X Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

Page 29 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 6: -X PCB edge mates to MEC1-105-02-L-D-NP-A connector on -X Solar Panel
Pin

Nomenclature

Type

Voltage

Source System

Load ZBus Pin

1

N/C

2
3

-X Solar Panel Thermistor
N/C

Analog

N/A

N/A

N/A

N/A

4
5

N/C
N/C

6

-X Solar Panel Common
N/C

7
8 N/C
9 N/C
10 -X Solar Panel CIC (+)

Ground
Plane

Power

N/A

N/A

Page 30 of 54

N/A

N/A

AMSAT Fox-1
Avionics System Design Specification

Figure 9: PSU System -X Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

Page 31 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 7: +Y PCB edge mates to MEC1-105-02-L-D-NP-A connector on +Y Solar Panel
Pin

Nomenclature

Type

Voltage

Source System

Load ZBus Pin

1

N/C

2
3

+Y Solar Panel Thermistor
N/C

Analog

N/A

N/A

N/A

N/A

4
5

+Y Antenna Sensor
N/C

Switch

N/A

PSU

N.O.

48

6

+Y Solar Panel Common
N/C

7
8 +Y Antenna Deploy
9 N/C
10 +Y Solar Panel CIC (+)

GroundPlane
AnalogVbatt

IHU

7 Ω resistor

50

Power

N/A

N/A

N/A

N/A

Page 32 of 54

AMSAT Fox-1
Avionics System Design Specification

Figure 10: PSU System +Y Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

Page 33 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 8: -Y PCB edge mates to MEC1-105-02-L-D-NP-A connector on -Y Solar Panel
Pin

Nomenclature

Type

Voltage

Source System

Load ZBus Pin

1

N/C

2
3

-Y Solar Panel Thermistor
N/C

Analog

N/A

N/A

N/A

N/A

4
5

-Y Antenna Sensor
N/C

Switch

N/A

PSU

N.O.

46

6

-Y Solar Panel Common
N/C

7
8 -Y Antenna Deploy
9 N/C
10 -Y Solar Panel CIC (+)

GroundPlane
AnalogVbatt

IHU

7 Ω resistor

44

Power

N/A

N/A

N/A

N/A

Page 34 of 54

AMSAT Fox-1
Avionics System Design Specification

Figure 11: PSU System -Y Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

Page 35 of 54

AMSAT Fox-1
Avionics System Design Specification
7 Battery System
7.1 System Requirements Applicable to Battery PCB 1 System (BATT1)

2.2.1
2.2.3
2.3.1
3.3.1
3.4.1
3.4.2
3.5.3
3.5.4
3.10.1
3.10.2

3.10.3The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
The satellite shall include a "Remove Before Flight" pin as per the CubeSat Design Specification.
The satellite battery and photovoltaic panels shall be electronically disconnected from the avionics
when the "Remove Before Flight" pin is inserted, regardless of the state of the deployment switch(es).
The satellite shall provide the means to charge the battery via the umbilical port while integrated with
the P-POD.
The satellite shall produce sufficient average electrical power to operate continuously in the orbit ofmaximum eclipse.
The satellite shall provide sufficient battery capacity to operate continuously in the orbit of maximum
eclipse.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card

RX T

Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.

Page 36 of 54

AMSAT Fox-1
Avionics System Design Specification
7.2 Volume Requirements Applicable to Battery PCB 1 System
7.2.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 4.0 mm from the -Z surface of the PC
board within the area 0 to 4.0 mm from the +Y and +X edges of the board, and 1.0 mm from the -Z
surface of the PC board in the rest of the board area.
7.2.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 17.0 mm from the +Z surface of the PC
board.
7.3 Interface Control Documents Applicable to Battery PCB 1 System
AMSAT Fox-1 IHU to Battery Interface Control Document
7.4 PCB Plating Requirements Applicable to Battery PCB 1 System
7.4.1 ENIG then selective flash gold four mounting pads.

Page 37 of 54

AMSAT Fox-1
Avionics System Design Specification
7.5 Battery PCB 1 System Bus Connections

Figure 12: Battery 1 System Bus Connection Pin Assignments

Page 38 of 54

AMSAT Fox-1
Avionics System Design Specification
7.6 Battery PCB 1 System External Connections
7.6.1 Umbilical as USB mini type B receptacle
7.6.2 Remove Before Flight as 3.5mm normally open TS jack
Table 9: Battery 1 External Connection Signal Characteristics
External
Connection

Nomenclature

Type

USB 1

USB +5 VDC

AnalogUSB 2

USB Data - (USBM)

DigitalUSB 3

USB Data + (USBP)

DigitalUSB 4GroundRBF 1

Solar Safe N

AnalogVoltage/Power Source System
USB
5 VDC
CONNECTOR
3.0 V
USB
CMOS
CONNECTOR
logic
3.0 V
USB
CMOS
CONNECTOR
logic
USB
CONNECTOR
3.5mm N.O. TS
N/A
jack

*When external supply is connected to USB port

Page 39 of 54

Load ZBus Pin

N/A

N/A

N/A

51

N/A

49

N/A

Ground
Plane

N/A

40

AMSAT Fox-1
Avionics System Design Specification
7.7 Battery PCB 2 System Bus Connections

Figure 13: Battery 2 Bus Connection Pin Assignments

Page 40 of 54

AMSAT Fox-1
Avionics System Design Specification
8 Experiment Payload Systems 1 through 4
8.1 System Requirements Applicable to Experiment Payload Systems 1-4
2.1.4
2.1.5
2.2.1
2.2.3
2.3.1
3.6.1
3.6.2
3.6.3

The satellite shall provide mass for an experiment payload up to 100 g.
The satellite shall provide volume for an experiment payload up to 95 x 95 x 15.7 mm.
The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
The satellite shall provide DC power for experiment payloads.
The satellite shall provide a means to activate and deactivate the experiment payloads.
The satellite shall provide a means to telemeter data from the experiment payloads.
8.2 Initial Surge Current Limits
8.2.1 All Experiment designs shall limit initial inrush current to 0.1 Amperes.
8.3 Volume Requirements Applicable to Experiment Payload System 1
8.3.1 No components, connections other than those connectors stipulated in section 10, andstructures such as shielding or enclosures shall protrude from the –Z surface of the PC board.
8.3.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
8.4 Interface Control Documents Applicable to Experiment 1 Payload System
AMSAT Fox-1 IHU to Experiment 1 Interface Control Document

8.5 Volume Requirements Applicable to Experiment Payload Systems 2 and 3
8.5.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
8.5.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
8.6 Volume Requirements Applicable to Experiment System 4
8.6.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
Page 41 of 54

AMSAT Fox-1
Avionics System Design Specification

8.6.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 5.0 mm from the +Z surface of the PC
board.
8.7 Interface Control Documents Applicable to Experiment 4 Payload System
AMSAT Fox-1 IHU to Experiment 4 Interface Control Document
8.8 PCB Plating Requirements Applicable to Experiment 1 Payload System
8.8.1 ENIG then selective flash gold four mounting pads. ENIG only will also be accepted if alreadyfabricated.
8.9 PCB Plating Requirements Applicable to Experiment 2 Payload System
8.9.1 ENIG then selective flash gold four mounting pads. ENIG only will also be accepted if alreadyfabricated.
8.10 PCB Plating Requirements Applicable to Experiment 3 Payload System
8.10.1 ENIG then selective flash gold four mounting pads. ENIG only will also be accepted if
already fabricated.
8.11 PCB Plating Requirements Applicable to Experiment 4 Payload System
8.11.1 ENIG then selective flash gold four mounting pads..

Page 42 of 54

AMSAT Fox-1
Avionics System Design Specification
8.12 Experiment Payload 1 Systems PCB Bus Connections

Figure 14: Experiment Payload 1-3 Systems Bus Connection Pin Assignments

Page 43 of 54

AMSAT Fox-1
Avionics System Design Specification
8.13 Experiment Payload 4 System PCB Bus Connections

Figure 15: Experiment Payload 4 System Bus Connection Pin Assignments

Page 44 of 54

AMSAT Fox-1
Avionics System Design Specification
8.14 Experiment Payload 4 System PCB External Connections
8.14.1 Three connections using Samtec FSI-105-06-L-S-AD connector
8.14.1.1 1 contact +Z Solar Panel Thermistor
8.14.1.2 1 contact +Z Solar Panel CIC +8.14.1.3 1 contact common or - for above two connections
Table 10: +Z PCB face FSI-105-06-L-S-AD connector mates to pads on +Z Solar Panel
Pin

Nomenclature

1+Z Thermistor

2

N/C

3

+Z Solar Panel Common

4

N/C

5

+Z CICType

Voltage

Source System

Load Z

Load System

Bus Pin

Analog

N/A

N/A

N/A

PSU

41
Ground
Plane

Power

N/A

N/A

Page 45 of 54

N/A

PSU

45

AMSAT Fox-1
Avionics System Design Specification

Figure 16: Experiment Payload 4 System FSI-105-06-L-S-AD
Connection Pin Assignments

Page 46 of 54

AMSAT Fox-1
Avionics System Design Specification
9 System Block Diagrams Reference
9.1 IHU System

Page 47 of 54

AMSAT Fox-1
Avionics System Design Specification
9.2 RF System
9.2.1 RF Transmitter Block Diagram

Page 48 of 54

AMSAT Fox-1
Avionics System Design Specification
9.2.2 RF Receiver Block Diagram

Page 49 of 54

AMSAT Fox-1
Avionics System Design Specification
9.3 PSU System

Page 50 of 54

AMSAT Fox-1
Avionics System Design Specification
10 System Interconnection References
10.1 Bus Connectors
10.1.1 Samtec QTH-030-02-L-D-A and QSH-030-01-L-D-A connectors
10.1.2 QTH connector shall be mounted on the +Z surface of each circuit board except the Receive
Antenna PCB / GPS Payload circuit board
10.1.3 QSH connector shall be mounted on the –Z surface of each circuit board
10.2 Bus Connector Documentation
10.2.1 Samtec QSH
10.2.2 Samtec QTH
10.2.3 Samtec QxH High Speed Characterization Report
10.2.4 Samtec QxH Single Ended Channel Properties
10.3 External Connectors
10.3.1 Samtec MEC1-105-02-L-D-NP-A connector mounted on +X, -X, +Y, -Y Solar Panels
10.3.2 Samtec FSI-105-06-L-S-AD connector mounted on -Z face of RF Transmitter System PCB
and +Z face of Experiment Payload 4 System PCB
10.4 External Connector Documentation
10.4.1 Samtec MEC1
10.4.2 Samtec MEC1 Qualification Testing
10.4.3 Samtec FSI
10.5 PCB Connector Layout Documentation
10.5.1 FOX-ME-113_PCB.pdf

Page 51 of 54

AMSAT Fox-1
Avionics System Design Specification
10.6 Systems PCB Connector Layout
10.6.1 Common to All Systems

Page 52 of 54

AMSAT Fox-1
Avionics System Design Specification
10.6.2 RF Transmitter System

10.6.3 PSU System

Page 53 of 54

AMSAT Fox-1
Avionics System Design Specification
10.6.4 Experiment 4 System

Page 54 of 54

AMSAT Fox-1
IHU to Battery ICD
Date: November 18, 2013
Version: Version 2.06

AMSAT Fox-1
IHU to Battery Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the Battery (BATT1) System, as required per the AMSAT Fox-1 System
Requirements Specification document.
1.1

Document History
DATE

VERSION

SUMMARY

August 7, 2012

1.00

Initial version

November 7, 2012

1.01

Added BATT CPU Temperature

December 27, 2012

1.10

Add Battery Groups Temperature, change from
Bytes to Bits in Message Header Block,Message Data Block, Message Data

January 2, 2013

1.11

Field sizes back to bytes account I²C
specifications

February 7, 2013

1.12

Fix typo on 3.3.1.1

August 13, 2013

2.00

Updated for TI ADS 7828 replacing STM32L,
straight I2C query/answer from IHU now for 8channels of data.

August 22, 2013

2.01

Correct Battery Pair Temperature nomenclature

August 22, 2013

2.02

Update I²C speed to 10 kHz

September 17, 2013

2.03

Fix formatting error that hid requirement 2.2.2,
change type format to exclude code type, add
Min/Max Values

November 7, 2013

2.04

Add battery voltage scaling in Table 1

November 7, 2013

2.05

Add verbiage about power bus voltage on
Battery Pair C to Table 1

November 18, 2013

2.06

Revise battery voltage scale verbiage in Table 1,
add raw value notation to BATT PCB Temp

Page 1 of 4

AMSAT Fox-1
IHU to Battery ICD
1.2 Document Scope
The purpose of this document is to specify the message format and the I²C bus hardware
operation for the communications between the IHU and the BATT1 as described in the
AMSAT Fox-1 System Requirements Specification.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification
4. Texas Instruments SBAS181C – NOVEMBER 2001 - REVISED MARCH 2005

Page 2 of 4

AMSAT Fox-1
IHU to Battery ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall be the I²C Master.
2.1.2 The BATT1 shall be the I²C Slave.
2.1.2.1 The IHU shall request the BATT1 to send the data for a specific channel.
2.1.2.2 The BATT1 shall send that specific channel data.
2.1.3 The IHU shall test for the presence of the BATT1 system.
2.1.3.1 If the presence of the BATT1 system is not detected, the IHU shall notpoll the system for data.
2.2

General Message Requirements

2.2.1 The IHU shall sample data at a rate sufficient to provide downlink telemetry
data at least every 15 seconds.
2.2.2 The ADS 7820 A/D converter shall always be commanded on (PD-0 bit =1).
2.2.3 The ADS 7820 Internal Reference shall always be commanded on (PD-1
bit = 1).
2.2.4 The ADS 7820 shall always be commanded for single-ended inputs.
2.3

I²C Bus Hardware Interface Requirements

2.3.1 The I²C Vdd shall be 3.0V.
2.3.2 The bus speed shall be Standard (10 kHz).
2.3.3 The BATT1 I²C 7 bit address shall be 0x48.

Page 3 of 4

AMSAT Fox-1
IHU to Battery ICD

3 Data Requirements
3.1

Measured Values

3.1.1 The measured data fields and their associated ADS 7828 channels shall be
as shown in Table 1.
Table 1

Field

Channel

Type

Min
Value

Max
Value

Description

BATT I

0

Unsigned

0x00

0xFFF

Battery current raw value

BATT A V

1

Unsigned

0x00

0xFFF

BATT B V

2

Unsigned

0x00

0xFFF

BATT C V

3

Unsigned

0x00

0xFFF

BATT A T

4

Unsigned

0x00

0xFFF

BATT B T

5

Unsigned

0x00

0xFFF

BATT C T

6

Unsigned

0x00

0xFFF

BATT PCB
Temperature

7

Unsigned

0x00

0xFFF

Battery pair A voltage raw
value (0-2.5V scale)Battery pairs A+B voltage
raw value (0-3.3V scale)Battery pairs A+B+C
voltage raw value (0-5.0V
scale)
This value also represents
the power bus voltage(VBATT)
Battery pair A
temperature raw value
Battery pair B
temperature raw value
Battery pair C
temperature raw value
Temperature of BATT
card raw value

3.1.2 Measurements shall be in relation to the 2.5 VDC internal voltage referenceof the ADS 7828.
3.1.3 The IHU shall poll each channel in channel number order.

Page 4 of 4

AMSAT Fox-1
IHU to PSU ICD
Date: June 11, 2014
Version: Version 2.21

AMSAT Fox-1
IHU to PSU Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the Power Supply (PSU) System, as required per the AMSAT Fox-1 System
Requirements Specification document.
1.1

Document History
DATE

VERSION

SUMMARY

February 21, 2012

1.0

Initial version

February 21, 20121.01

Clarify I²C address

March 7, 2012

1.02

2.3.1 updated Vdd to 3.0V

August 7, 2012

1.03

Remove BATT1 data fields and adjust message
accordingly

November 7, 2012

1.04

Added PSU CPU Temperature

December 27, 2012

1.10

Change from Bytes to Bits in Message Header
Block, Message Data Block, Message Data (toallow for 12 bit ADC values)

January 2, 2013

1.11

Field sizes back to bytes account I²C
specifications

February 7, 2013

1.12

Correct typo in 3.3.1.1

August 22, 2013

1.13

Remove TOTAL I from Data block

August 22, 2013

1.14

Update I²C speed to 10 kHz

October 4, 2013

2.00

Rework to eliminate STM32L and replace with
ADS7828s

November 18, 2013

2.01

Change telemetry sample rate in 2.2.1 to 4
seconds

April 21, 2014

2.1

Table 1 and Table 2 redone to use actual
connections from PSU construction, 3.1.3
changed to show use of regulated Sensor Power
source as 7828 voltage reference

June 10, 2014

2.2

Added PSU Output Current to Table 2

June 11, 2014

2.21

Swap Device 1 and Device 2 addresses toaccount for construction error

Page 1 of 5

AMSAT Fox-1
IHU to PSU ICDDATEVERSION

SUMMARY

June 30, 2014

2.22

Modify 2.2.3 to command OFF rather than ON
account internal reference not used on actual
hardware build

1.2 Document Scope
The purpose of this document is to specify the message format and the I²C bus hardware
operation for the communications between the IHU and the PSU as described in the
AMSAT Fox-1 System Requirements Specification.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification

Page 2 of 5

AMSAT Fox-1
IHU to PSU ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall be the I²C Master.
2.1.2 The PSU shall be the I²C Slave.
2.1.2.1 The IHU shall request the PSU to send the data for a specific Device andchannel.
2.1.2.2 The PSU shall send that specific Device and channel data.
2.1.3 The IHU shall test for the presence both PSU system Devices.
2.1.4 The IHU shall only poll the PSU system Device(s) present, for data.
2.2

General Message Requirements

2.2.1 The IHU shall sample data at a rate sufficient to provide downlink telemetry
data every 4 seconds.
2.2.2 For both Devices the ADS 7820 A/D converter shall always be commandedon (PD-0 bit = 1).
2.2.3 For both Devices the ADS 7820 Internal Reference shall always becommanded off (PD-1 bit = 0).
2.2.4 TFor both Devices the ADS 7820 shall always be commanded for singleended inputs.
2.3

I²C Bus Hardware Interface Requirements

2.3.1 The I²C Vdd shall be 3.0V.
2.3.2 The bus speed shall be Standard (10 kHz).
2.3.3 The PSU system Device 1 I²C 7 bit address shall be 0x4A.
2.3.4 The PSU system Device 2 I²C 7 bit address shall be 0x49.

Page 3 of 5

AMSAT Fox-1
IHU to PSU ICD

3 Message Content Requirements
3.1

Measured Values

3.1.1 The measured data fields for Device 1 and their associated ADS 7828
channels shall be as shown in Table 1.
Table 1

Field

ChannelType

Min Value Max Value

Description+X PANEL V

0

Unsigned

0x00

0xFFF

+X PANEL V-X PANEL V

1

Unsigned

0x00

0xFFF

-X PANEL V+Y PANEL V

2

Unsigned

0x00

0xFFF

+Y PANEL V-Y PANEL V

3

Unsigned

0x00

0xFFF

-Y PANEL V+Z PANEL V

4

Unsigned

0x00

0xFFF

+Z PANEL V-Z PANEL V

5

Unsigned

0x00

0xFFF

-Z PANEL V

Not used

6

-

-

-

-

Not used

7

-

-

-

-

3.1.2 The measured data fields for Device 2 and their associated ADS 7828
channels shall be as shown in Table 2.
Table 2Field

Channel

Type

Min
Value

Max
Value

Description

PSU PCB
Temperature0

Unsigned

0x00

0xFFF

Temperature ofPSU card+X PANEL T

1

Unsigned

0x00

0xFFF

+X PANEL T-X PANEL T

2

Unsigned

0x00

0xFFF

-X PANEL T+Y PANEL T

3

Unsigned

0x00

0xFFF

+Y PANEL T-Y PANEL T

4

Unsigned

0x00

0xFFF

-Y PANEL T+Z PANEL T

5

Unsigned

0x00

0xFFF

+Z PANEL T-Z PANEL T

6

Unsigned

0x00

0xFFF

-Z PANEL TPSU Current

7

Unsigned

0x00

0xFFF

PSU Output Current

Page 4 of 5

AMSAT Fox-1
IHU to PSU ICD
3.1.3 Measurements shall be made in relation to the v_regulated voltage on the
IHU.
3.1.4 For each Device the IHU shall poll each channel in channel number order.

Page 5 of 5

AMSAT Fox-1A
IHU to Experiment 1 ICD
Date: May 21, 2014
Version: Version 1.09

AMSAT Fox-1A
IHU to Experiment 1 Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the Experiment System in Position 1 of the satellite, known as the Vanderbilt
University Vulcan Payload and abbreviated herein as EXP1.
1.1

Document History
DATE

VERSION

SUMMARY

March 3, 2013

1.00

Initial version

March 7, 2013

1.01

Correct use of I²C (1.2) and EXP1 (2.3.3)

March 31, 2013

1.02

Command Message CRC8 to include addressbyte, change to commands, modified figure 3,
deleted figure 4

March 31, 2013

1.03

Delete TYPE from message tables, add SET
TIME response return values

March 31, 2013

1.04

Add CMD_VERSION_ERR to Error Code table

April 2, 2013

1.05

Correct 6.5 Figure 3, remove 0x0005, 0x0201,
0x0210, 0x0281, 0x0300, and 0x0301
commands

September 17, 2013

1.06

Change type format to exclude code type, add
Min/Max Values

October 7, 2013

1.07

Revised Table 1 and 3.2.1 added 3.5.1.1 forclarification on Experiment Enable 1 states

November 7, 2013

1.08

Added 3.1.2 and 3.1.3 regarding minimum
power levels for experiment operation

May 21, 2014

1.09

Revised 3.1.2 and 3.1.3 to read <= 3.3V

Page 1 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
1.2 Document Scope
This document will specify the control of EXP1, the messaging format, and the I²C bus
hardware operation for the communications between the IHU and the EXP1.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification
4. Vanderbilt University Vulcan Payload Interface Control Document

Page 2 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall initiate a command to the EXP1.
2.1.2 The EXP1 shall send a reply to each IHU request.
2.1.3 Message bit order shall be Big Endian.
2.1.4 The IHU shall determine the action to be taken in the event of an invalid,
improper, or missing message from the EXP1.
2.1.5 The EXP1 shall take no action in the event of an invalid or improper
message from the IHU.
2.1.6 Message byte order shall be Big Endian.
2.2

General Message Requirements

2.2.1 Each message shall contain a header block.
2.2.2 Each message shall contain a packet error check (PEC) in the form of
CRC8.
2.2.2.1 The message address byte shall be included when calculating the
CRC8.
2.3

I²C 1 Bus Hardware Interface Requirements

2.3.1 The I²C Vdd shall be 3.0V.
2.3.2 The bus speed shall be Fast (400kbit/s).
2.3.3 The EXP1 I²C 7 bit address shall be 0x2A.

Page 3 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD

3 Experiment Operation
3.1

Experiment Power Control

3.1.1 The IHU shall exert control over the power state of the EXP1 by theExperiment Enable 1 pin on the satellite bus as shown in Table 1.
Table 1Pin State

Description

High

Power On Experiment

Low or highimpedancePower Off Experiment3.1.2 The IHU shall not power on the experiment if the power bus voltage(VBATT) is less than or equal to 3.3 Volts.
3.1.3 The IHU shall perform the Experiment Cease Operation Sequence andthe Experiment Power Off Sequence if the power bus voltage (VBATT)
falls to less than or equal to 3.3 Volts while the experiment is powered on.
3.2

Experiment Power On Sequence

3.2.1 The IHU shall set and hold the Experiment Enable 1 pin HIGH.
3.2.2 The IHU shall not send any message to the EXP1 for a minimum of 100
milliseconds.
3.2.3 The IHU shall send a Set Time command to the EXP1.
3.3

Experiment Begin Operation Sequence

3.3.1 Upon completion of the Power On sequence the IHU shall send a Set Run
State Active command message to the EXP1.
3.4

Experiment Cease Operation Sequence

3.4.1 The IHU shall send a Set Run State Halt command message to the EXP1.
3.4.2 The IHU shall not send any message to the EXP1 for a minimum of 10000
milliseconds.
3.4.3 The IHU shall send a Set Run State Standby command message to the
EXP1.
3.5

Experiment Power Off Sequence

3.5.1 The IHU shall set the Experiment Enable 1 pin LOW.
3.5.1.1 The absence of a HIGH state on the Experiment Enable 1 pin shall be
construed as a LOW state whether the pin is actually LOW, or in ahigh-impedance state.
Page 4 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD

4 Message Content Requirements
4.1

Command Message

4.1.1 The message header block shall be constructed as shown in table 2.
4.1.2 The message header block shall be sent with each Command andResponse block.
Table 2

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

Message
Version2

Unsigned

0x01

0xFFFF

Message ICD
versionSoftware Build

2

Unsigned

0x01

0xFFFF

Software Buildversion

4.1.2.1 The Message Version shall be an integer representing the IHU to
EXP1 ICD document version number from which the message format
is derived, having the decimal point removed (e.g. version 1.03 would
be 103 decimal or 0x67).
4.1.2.2 The Software Build shall be an integer representing the software build
version number of the system originating the message, having any
decimal points removed (e.g. version 1.03 would be 103 decimal or0x67).
4.2

Command Message Block4.2.1 The command message block shall be constructed as shown in Table 3.
Table 3

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

COMMAND

2

Unsigned

0x00000x0280

Hexadecimal
Command

ARGUMENT

Variable

Unsigned--

Optional Arguments
As Required

The command message block shall contain one command in the COMMAND
COMMAND field as shown in Table 4.

Page 5 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
Table 4

Command
Name

Size(Bytes)

Min
Value

Type

Max
Value

Description

0x0000No effect; response
undefined. Test for I²C
acknowledgement only.

Nop

2

Unsigned 0x0000

Echo

2

0x0001

Echo this byte stream

Resend2

Unsigned 0x0001
Unsigned 0x0002

0x0002

Resend last result

Get UID

2

Unsigned 0x0003

0x0003Controller 7 byte identifier

Get Status

2

Unsigned 0x0004

0x0004Controller statusindication

Get
Diagnostics

2

Unsigned 0x0006

0x0006

Self-check Diagnostic

Get
Telemetry

2

Unsigned 0x0010

0x0010Send telemetry data

Set RunState

2

Unsigned 0x0080

0x0080Enter specified Run State

Get RunState

2

Unsigned 0x0081

0x0081

Query current Run StateSet Time

2

Unsigned 0x0100

0x0100

Number of seconds sinceepoch

Get Time

2

Unsigned 0x0101

0x0101

Number of seconds sinceepoch

Get Data2

Unsigned 0x0280

0x0280Send (number of bytes)
data

4.2.3 The command message shall contain arguments for the Echo command,as shown in Table 5.
Table 5

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

ARGUMENT

4

Unsigned--

Data to beechoedPage 6 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
4.2.4 The command message shall contain one argument for the Set Run State
command, as shown in Table 6.
Table 6Run State

Size(Bytes)

Type

Min
Value

Max
Value

Description

STANDBY

2

Unsigned

0x00010x0001Enter Standby StateACTIVE

2

Unsigned

0x00030x0003

Activate
Experiments

HALT

2

Unsigned

0x00040x0004

Terminate
Experiments

4.2.5 The command message shall contain arguments for the Set Timecommand, as shown in Table 7.
Table 7

Argument

Size(Bytes)

Type

Min
Value

Max
Value

IHU Reset
Counter

16

Unsigned

0x00

-

MET
Timestamp

32

Unsigned--

Description
Count of the number of
IHU resets from nonvolatile FRAM
MET timestamp (seconds
since last IHU reset)

4.2.6 The command message shall contain arguments for the Get Data
command, as shown in Table 8.
Table 8

Argument

Size(Bytes)

Type

Min
Value

Max
Value

Description

BYTES TO
SEND

2Unsigned

0x00

0xFFFF

Number of bytes tosend (1-256)

Page 7 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
4.3

Response Message Block4.3.1 The response message block shall be constructed as shown in Table 9.
Table 9

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

RESERVED

1

Unsigned--

Reserved, ignore

ERROR
CODE

1

Unsigned

0x00000x0006

Response to
CommandLENGTH

2

Unsigned

0x00

0xFFFF

Length of Return
Value in Bytes

RETURN
VALUE

Variable

Variable--

Return Value

4.3.2 The Error Code shall contain one code as shown in table 10.
Table 10

Name

Size
(Bytes)

Type

Min
Value

Max
Value

Description

CMD_OK

1

Unsigned 0x0000

0x0000Commandinvokedsuccessfully

CMD_OP_ERR

1

Unsigned 0x0001

0x0001

Command notrecognized

CMD_FORMAT_ERR

1

Unsigned 0x0002

0x0002

Incorrect
commandargument
lengthCMD_RANGE_ERR

1

Unsigned 0x0003

0x0003

Argument(s)out of bounds

CMD_PEC_ERR

1

Unsigned 0x0004

0x0004

Error check(CRC)
mismatch

CMD_EXEC_ERR

1

Unsigned 0x0005

0x0005

Execution error

0X0006

HeaderMessage
Versionmismatch

CMD_VERSION_ERR

1

Unsigned 0x0006

Page 8 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
4.3.3 The Status Flags for a GET STATUS response message shall be
represented as individual bit values of a 16 bit RETURN VALUE asshown in Table 11.
Table 11

Name

Bit
NumberDescription

REBOOTED0

1 = Experiment has rebooted – NOT USEDDATA READY

1

1 = Experiment data available

TIME REQUEST

2

1 = Request SET TIME

FAILED RUN STATE

3

1 = Failed the run state – NOT USEDCOMPLETED RUN STATE

4

1 = Completed the run state – NOT USEDRESERVED

5-15

Always 0

4.3.4 The response message to a Set Time command shall contain one of thevalues as shown in Table 12.
Table 12

Response
Name

Size(Bytes)

Type

Min
Value

Max
Value

SUCCESS

2

Signed0x00

0x00

Time Set
successfully

FAILURE

2

Signed0xFFFF

0xFFFFTime Set failed

Description

5 Message Integrity
5.1

Invalid Messages

5.1.1 If the PEC (CRC8) fails, the message shall be considered invalid.
5.1.2 If the Message Version does not match the message version in use forthe construction of messages on the receiving system, the message shallbe considered invalid.

Page 9 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD

6 Message Flow Diagrams
6.1

EXPERIMENT POWER ON SEQUENCE

IHU

EXP1
ASSERT EXPERIMENT 1 ENABLE

SET TIMERESPONSEIHU Handling

6.2

End

EXPERIMENT BEGIN OPERATION SEQUENCE

IHU

EXP1
SET RUN STATE: ACTIVERESPONSEIHU Handling

End

Page 10 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
6.3

EXPERIMENT CEASE OPERATION SEQUENCE

IHU

EXP1
SET RUN STATE: HALTRESPONSESET RUN STATE: STANDBYRESPONSEIHU Handling

6.4

End

EXPERIMENT POWER OFF SEQUENCE

IHU

EXP1
DEASSERT EXPERIMENT 1 ENABLE

IHU Handling

End

Page 11 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
6.5

SERVICING EXPERIMENT OPERATION

Figure 1

IHU

EXP1
GET STATUS

STATUS = REBOOTED or FAILED or COMPLETEDIHU HandlingEnd

Figure 2

IHU

EXP1
GET STATUS
STATUS = TIME REQUESTSET TIMERESPONSEIHU Handling

End

Page 12 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD

Figure 3

IHU

EXP1

GET DATADATAIHU Handling

End

Page 13 of 13

AMSAT Fox-1A
IHU to Experiment 4 ICD
Date: June 26, 2014
Version: Version 1.20

AMSAT Fox-1A
IHU to Experiment 4 Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the Experiment System in Position 3 of the satellite, known as the VT Camera
Experiment and abbreviated herein as EXP3.
1.1

Document History
DATE

VERSION

SUMMARY

January 24, 2013

1.00

Initial version

February 20, 2013

1.01

Specify byte order as little endian

May 21, 2013

1.10

Update data TYPE names

October 4, 2013

1.11

Change type format to exclude code type, add
Min/Max Values, add thermistor circuit

October 7, 2013

1.12

Modify Table 1 to clarify Experiment Enable 4
pin states

1.20

Add “No Earth Image Available” to NN
description in Table 6, remove section 7
thermistor requirement no longer applicable,change all references to EXP4 to read EXP3
reflecting proper location of experiment

June 26, 2014

1.2 Document Scope
This document will specify the control of EXP3, the messaging format, and the serial bus
hardware operation for the communications between the IHU and the EXP3.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification

Page 1 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall initiate a command to the EXP3.
2.1.2 The EXP3 shall send a reply to each IHU request.
2.1.3 Message bit order shall be Little Endian.
2.1.4 The IHU shall determine the action to be taken in the event of an invalid,
improper, or missing message from the EXP3.
2.1.5 The EXP3 shall take no action in the event of an invalid or improper
message from the IHU.
2.1.6 Message byte order shall be Little Endian.
2.2

General Message Requirements

2.2.1 Each message shall contain a header block.
2.2.2 Each message shall contain one command, one reply, or one data block.
2.3

Serial Bus Hardware Interface Requirements

2.3.1 The bus levels shall be 3.0V.
2.3.2 The bus data speed shall be 38400 bit/s.
2.3.3 The serial bus communication shall be asynchronous.
2.3.4 The number of data bits shall be 8.
2.3.5 The number of stop bits shall be 1.
2.3.6 There shall be no parity bit.

Page 2 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

3 Experiment Operation
3.1

Experiment Power Control

3.1.1 The IHU shall exert control over the power state of the EXP3 by theExperiment Enable 4 pin on the satellite bus as shown in Table 1.
Table 1Pin State

Description

High

Power On Experiment

Low or high-impedance Power Off Experiment3.1.2 Upon signaling Power On to the EXP3, the IHU shall not send any
message to the EXP3 for a minimum of 100 milliseconds.
3.2

Experiment Operation Sequence

3.2.1 Upon Power On the IHU shall determine the state of the EXP3 by sending
an Is Camera Ready command message.
3.2.2 The IHU shall not send a Transmit Data Block command message prior toreceiving a Camera Ready reply message from the EXP3.

4 Message Content Requirements
4.1

Message Header Block4.1.1 The message header block shall be constructed as shown in table 2.
4.1.2 The message header block shall be sent with each Command, Reply, andData block.
Table 2

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

Message
Version2

Unsigned

0x01

0xFFFF

Message ICD
versionSoftware Build

2

Unsigned

0x01

0xFFFF

Software Buildversion

4.1.2.1 The Message Version shall be an integer representing the IHU to
EXP3 ICD document version number from which the message format
is derived, having the decimal point removed (e.g. version 1.03 would
be 103 decimal or 0x67).
Page 3 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

4.1.2.2 The Software Build shall be an integer representing the software build
version number of the system originating the message, having any
decimal points removed (e.g. version 1.03 would be 103 decimal or0x67).
4.2

Command Message Block4.2.1 The command message block shall be constructed as shown in Table 3.
Table 3Field

Size (Bytes)

Type

COMMAND

2Alpha

Min Value Max Value Description
RR
TT

RR
TT

Command4.2.2 The command message block shall contain one command in the
COMMAND field as shown in Table 4.
Table 4

Command

Description

RR

Is Camera Ready?

TT

Transmit Data Block

4.3

Reply Message Block4.3.1 The reply message block shall be constructed as shown in Table 5.
Table 5

Field

Size (Bytes)

Type

REPLY

2

Alpha

Min Value Max Value Description
NN
YY
FF

NN
YY
FF

Reply

4.3.2 The reply message block shall contain one reply in the REPLY field asshown in table 6.

Page 4 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD
Table 6

Command

Description

NN

Camera Not Ready or No
Earth Image Available

YY

Camera ReadyFF

Camera Failed

Page 5 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

4.4

Message Data Block4.4.1 The message data block shall be constructed as shown in Table 7.
Table 7

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

DESCRIPTOR

2

Unsigned--

Line ID and Payload
LengthPAYLOAD

Variable

Unsigned--

Array of (Payload
Length) bytes

CHKSUM

2

Unsigned--

16 bit accumulator sum
of bytes in HEADER
and PAYLOAD

4.4.2 The bits of the message data block DESCRIPTOR bytes shall be
constructed as shown in Table 8.
Table 8

Field

Size
(Bits)

Type

Min
Value

Max
Value

Description

Line ID

6

Unsigned

0x01

0x3C

640 x 8 pixel picture line
number (1 is top, 60 isbottom)PayloadLength10

Unsigned

0x01

0x3FF

Total number of bytes in
PAYLOAD

4.4.2.1 The Line ID shall compose the 6 MSB and the Payload Length shallcompose the 10 LSB.

5 Message Integrity
5.1

Invalid Messages

5.1.1 If the DATA block CHKSUM fails, the message shall be consideredinvalid.
5.1.2 If the Message Version does not match the message version in use forthe construction of messages on the receiving system, the message shallbe considered invalid.

Page 6 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

6 Message Flow Diagrams
6.1

RR COMMAND

IHU

EXP4
COMMAND: RR

REPLY: NN, YY, OR FF

IHU Handling

End

Page 7 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD
6.2

TT COMMAND

IHU

EXP4
COMMAND: TT

MESSAGE DATA BLOCK OR REPLY:FF

IHU Handling

End

Page 8 of 8

AMSAT Fox-1A
Downlink Specification
Date: September 30, 2014
Version: Version 2.00

AMSAT Fox-1A
Downlink Specification
1 Introduction
This document specifies downlink frame formats for the Fox-1A telemetry andexperiment telemetry. This specification includes the both slow and high speed formats.
Document History
DATE

VERSION

SUMMARY

April 25, 2013

1.01

Remove TX PA Temperature and TX Osc
Temperature, add TX Temperature

May 21, 2013

1.2

High speed downlink details added

May 27, 2013

1.3

Remove Radiation Experiment Telemetry
Frame, resize Radiation Experiment Data
Frame, renumber Payload Types, added Slow
Speed Link Layer Transmission Scheduling,changed Reset Count to 16 bits

June 6, 2013

1.31

Reduce BATT CPU, PSU CPU, IHU CPU, TX
Temp, RX Osc Temp from 12 to 8 bit value, add
IHU Error Data field to Telemetry Minimum
Values Frame

June 26, 2013

1.32

Correct Payload Type numbers in Table 6

August 13, 2013

1.40

Changes due to new BATT telemetry values,
delete Type 4 from idle telemetry

August 26, 2013

1.41

Change Receiver Osc Temperature to Receiver
Card Temperature, remove TOTAL MPPT I,
update 2.2.9.1 and 2.2.9.1.1 to reflect variable
size of Radiation Experiment Data available

September 14, 2013

September 16, 2013

1.42

1.43

Added 3.1.2, Payload type 0 debug frame, madeScan Line Segment – Picture Count size 8 bits,
add RSSI to Payloads 1, 2, and 3, change typeformat to exclude code type, add Min/Max
ValuesAdded EXP4 temperature to Payloads 1, 2, and3, changed PSU CPU temp to PSU card temp

Page 1 of 20

AMSAT Fox-1A
Downlink Specification

DATE

VERSION

SUMMARY

October 15, 2013

1.44

Correct bit count for frame Type 3, change
calculated spin rate to remove PSU reference

November 18, 2013

1.45

Expanded all temperature fields to 12 bits, redo
3.1 payload order, add 2.2.7.3 and 2.2.7.4,
update SPIN to show bit pattern, add System I²C
Failure indications, add Ground Command TLM
reset count, add IHU Soft Error Data, add IHUHard Error Data, increase IHU Error Data to 32
bits, clarify which fields are raw values, added
2.2.7 5 padding slow speed frames, 2.2.8 forslow speed trailer info

January 13, 2014

1.50

Redo 3.2 beacon payloads

January 13, 2014

1.51

Change 3.2.1 to allow payload type 2 and 3 onlywith the voice ID

January 13, 2014

1.52

Correct 2.2.9 high speed link layer header
structure to show 16 bits on the Reset Count

January 14, 2014

1.53

Correct Table 4 and Table 5 Reset Count Max
Value to 0xFFFF to match use of 16 bits

February 10, 2014

1.54

Modify Table 11 to read “Experiment 1 Data” inthe description, added Safe Mode Indication bit
to payload 2 and 3, changed Filler bit size to 1 inpayload 2 and 3.

March 19, 2014

1.55

Move IHU Soft Error Data to Payload Type 3,
Move IHU Error Data to Payload Type 1 andrename to IHU Diagnostic Data, update Table 1
Bit Rate to 200 bps and Spectral Efficiency to 2
bps/Hz, remove Scrambler reference from Table
1 and Table 2.

March 24, 2014

1.56

Add timestamp elements to Payload 2 andPayload 3 for specific MAX or MIN last changed

April 23, 2014

1.57

Fix 4.4 BATT Board Temperature description toread Low instead of High

June 10, 2014

1.58

Remove Payload Type 2 MRAM Error
Count, Add PSU DC current, PSU DC highcurrent, PSU DC low current to Payload
Type 1, 2, 3 respectively

September 30, 2014

2.00

Reorder fields in Payload Type 1, 2, 3,
delete filler fields, add filler bits to Table 5
Page 2 of 20

AMSAT Fox-1A
Downlink Specification
1.1 Document Scope
The purpose of this document is to specify the downlink protocol on the AMSAT Fox-1A
spacecraft.
1.2 References
1. Fox1 IHU to RF ICD
2. Fox1 IHU to Battery ICD
3. Fox1 IHU to PSU ICD
4. Fox1 IHU to Attitude Determination Experiment ICD
5. Fox1 IHU Software Architecture Specification
6. Fox1 IHU to Experiment 1 ICD
7. Fox1 IHU to Experiment 4 ICD
1.3 Definitions
1.3.1 Slow Speed Downlink – Data transmitted at approximately 100 bits per
second in the audio portion below 300 Hz simultaneous with thetransponder audio.
1.3.2 High Speed Downlink – Data transmitted at approximately 9600 bits per
second using the entire downlink audio passband.
1.3.3 Spacecraft Telemetry – Downlink data containing specific information
about spacecraft systems and health as defined in the System
Requirements and related documents.
1.3.4 Experiment Telemetry – Downlink data containing specific information
about the various experiment platforms flown on the satellite.
1.3.5 Frame – A defined set of data with a specific overall size comprised offields of a specific bit or byte length.

Page 3 of 20

AMSAT Fox-1A
Downlink Specification

2 Protocol Structure
2.1 Physical Layer
2.1.1 The physical layer includes options for slow-speed and high speed
operation.
2.1.2 Slow speed operation uses frequency-shift keying and is transmitted in
the sub-audible part of the audio downlink below 300 Hz. It may betransmitted simultaneously with voice or other audio signals. The detailsof the physical layer are shown in Table 1.
Table 1

Bit Rate
Spectral efficiency
Modulation type
Signal bandwidth
FSK Deviation
Spectral Mask
RF Channel Bandwidth

200 bps
2 bps/Hz
Non-coherent Frequency Shift Keying (FSK)
10 Hz to 200 Hz (-3 dB points)
500 Hz-20 dB at 300 Hz
1200 Hz

2.1.3 High speed operation uses frequency-shift keying and is transmittedusing the entire RF downlink bandwidth. The details of the physical layer
are shown in Table 2. Note that this is the same as the G3RUH modem.
Table 2

Bit Rate
Spectral efficiency
Modulation type
Signal bandwidth
FSK Deviation
Spectral Mask
RF Channel Bandwidth

9600 bps
2 bps/Hz
non-coherent frequency shift keying (FSK)
10 Hz to 4800 Hz (-3 dB points)
3 kHz-60 dB at 7500 Hz
20 kHz

2.2 Link Layer
2.2.1 The link layer protocol provides multiplexing, packet identification andforward error correction.
2.2.2 The link layer shall include a header and a trailer surrounding theapplications layer payload to form data packets as shown in Table 3.
Table 3Header

Applications Payload

Page 4 of 20

TrailerAMSAT Fox-1A
Downlink Specification
2.2.3 The applications payload layer shall include satellite telemetry,experiment telemetry, high speed data, and debug frames.
2.2.4 Debug frames may be used during ground testing but shall not betransmitted for flight.
2.2.5 Bits shall be transmitted in the order of most significant bit first.
2.2.6 Bytes shall be transmitted in Little Endian order.
2.2.7 The Slow Speed link layer header structure shall be as shown in Table 4.
Table 4

Field

Size
(Bits)

Type

Min
Value

Max Value

Fox ID

3

Unsigned

0x01

0x01

Reset
Count

16

Unsigned

0x00

0xFFFF

Uptime25

Unsigned

0x00

0x1FFFFFF

Type

4

Unsigned

0x00

0x0F

Description
0x01 specifies Fox-1A (eachFox satellite will have aunique ID)
Total number of times IHU
has reset since initial on-orbit
startupThis is the IHU uptime inseconds since the last reset
This identifies the payload
type

2.2.7.1 Payload type shall be as specified in the application layer payload
data.
2.2.7.2 Each Slow Speed link layer structure shall contain only one payload
type.
2.2.7.3 Reset Count and Uptime shall reflect the time at which the payload
data was collected.
2.2.7.4 Reset Count and Uptime shall not be changed if the payload data has
not been updated.
2.2.7.5 Real-Time Telemetry Frame, Telemetry Maximum Values Frame, andTelemetry Minimum Values Frame data shall be padded with zeros toequal 58 bytes length for each.
2.2.8 Forward error correction (FEC) code words shall be sent in the link layer
trailer. The FEC shall be a Reed Solomon RS 255,223 code. (Thisprovides 32 parity bytes per code word allowing error detection andcorrection capability.)
2.2.9 The High Speed link layer header structure is shown in Table 5.

Page 5 of 20

AMSAT Fox-1A
Downlink Specification
Table 5

Field

Size
(Bits)

Type

Min
Value

Max Value

Fox ID

3

Unsigned

0x01

0x01

Reset
Count

16

Unsigned

0x00

0xFFFF

Uptime25

Unsigned

0x00

0x1FFFFFF(No
Value)

4

Unsigned

0x00

0x00

Description
0x01 specifies Fox-1A (eachFox satellite will have aunique ID)
Total number of times IHU
has reset since initial on-orbit
startupThis is the IHU uptime inseconds since the last reset
4 bit filler

2.2.10 The High Speed link layer applications payload shall contain data fromall payload types, as shown in table 6.
Table 6

Payload Type

Size (Bytes)

Description

160Real-Time Telemetry Frame

2

60

Telemetry Maximum Values Frame

3

60

Telemetry Minimum Values Frame

5

Variable1 - 4300

Camera JPEG Data Frame

4

58

Radiation Experiment High Speed Data Frame

2.2.10.1 A varying number of Radiation Experiment Data bytes shall be sent
to fill the applications payload size to a total of 4600 bytes if the
payload type 5 data is less than 4300 bytes.
2.2.10.1.1 When less than a sufficient number of bytes to contain a usefuldata frame remain to fill to 4600 bytes, the remaining bytes shallbe filled with zeros.
2.2.10.2 Real-Time Telemetry Frame, Telemetry Maximum Values Frame,
and Telemetry Minimum Values Frame data shall be padded withzeros to equal 60 bytes length for each.
2.2.11 Forward error correction (FEC) code words shall be sent in the link
layer trailer. The FEC shall be a Reed Solomon RS 255,223 code. (Thisprovides 32 parity bytes per code word allowing error detection andcorrection capability.) Twenty one code words will be populated inparallel, with 1 byte being added to each code word in sequence until all
Page 6 of 20

AMSAT Fox-1A
Downlink Specification
bytes have been processed. The last code word will be partially filled
and should be virtually padded with 77 bytes. The data will then be sent
sequentially with 8b10b coding. Twenty one sets of 32 parity bytes will
follow after all data has been sent for the high speed frame.

3 Slow Speed Link Layer Transmission Scheduling
3.1 While IHU PTT is asserted Payload Types contained in the Link Layer
Applications Payload shall rotate, changing type with each successive
link layer transmitted, in the following order:
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x

Type 1
Type 4
Type 4
Type 1
Type 4
Type 4
Type 1
Type 4
Type 4
Type 1
Type 2Type 4
Type 1
Type 4
Type 4
Type 1
Type 4
Type 4
Type 1
Type 4
Type 4
Type 1
Type 3
Type 43.1.1 The above order shall be repeated so long as IHU PTT is asserted.
3.1.2 Each time IHU PTT is asserted the order shall begin at the top.
3.1.3 The IHU PTT shall not be de-asserted during transmission of a Link
Layer.

Page 7 of 20

AMSAT Fox-1A
Downlink Specification
3.2 While beacon message is sent during idle timer expired the Payload
Types contained in the Link Layer Applications Payload shall betransmitted in alternating sets, one set per beacon message:
Set 1:x Type 1
x Type 2
Set 2:x Type 1
x Type 3
3.2.1 The payload type 2 or 3 data shall be sent simultaneously with the voiceID.

Page 8 of 20

AMSAT Fox-1A
Downlink Specification

4 Application Layer Payload Data
4.1 Payload Type 0 – Debug Frame (NOT TO BE TRANSMITTED FOR
FLIGHT)
Table 7

Field

Size
(Bits)

Type

Min
Value

Max
Value

Description

UNDEFINED

1 - 464

Undefined--

Debug data for groundtesting

Page 9 of 20

AMSAT Fox-1A
Downlink Specification
4.2 Payload Type 1 - Real-Time Telemetry Frame (Size = 429 bits)
Table 8

Field

Size
(Bits)

Type

Min
Value

Max
Value

BATT A V

12

Unsigned

0x00

0xFFF

BATT B V

12

Unsigned

0x00

0xFFF

BATT C V

12

Unsigned

0x00

0xFFF

BATT A T

12

Unsigned

0x00

0xFFF

BATT B T

12

Unsigned

0x00

0xFFF

BATT C T

12

Unsigned

0x00

0xFFF

12

Signed

0x00

0xFFF

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

-X PANEL V

12

Unsigned

0x00

0xFFF

+Y PANELV

12

Unsigned

0x00

0xFFF

-Y PANEL V

12

Unsigned

0x00

0xFFF

+Z PANEL V

12

Unsigned

0x00

0xFFF

-Z PANEL V

12

Unsigned

0x00

0xFFF

+X PANEL T

12

Unsigned

0x00

0xFFF

-X PANEL T

12

Unsigned

0x00

0xFFF

+Y PANEL T

12

Unsigned

0x00

0xFFF

-Y PANEL T

12

Unsigned

0x00

0xFFF

+Z PANEL T

12

Unsigned

0x00

0xFFF

TOTAL
BATT IBATT Board
Temperature+X PANEL
V

Page 10 of 20

Description
Battery pair A voltage raw
value (0-2.5V scale)Battery pairs A+B voltage
raw value (0-3.3V scale)Battery pairs A+B+C
voltage raw value (0-5.0V
scale)
This value also represents
the power bus voltage(VBATT)
Battery pair A temperature
raw value
Battery pair B temperature
raw value
Battery pair C temperature
raw value
Total Battery DC current
raw value
PC Board Temperature of
BATT raw value+X solar panel voltage raw
value-X solar panel voltage raw
value+Y solar panel voltage raw
value-Y solar panel voltage raw
value+Z solar panel voltage raw
value-Z solar panel voltage raw
value+X solar panel temperature
raw value-X solar panel temperature
raw value+Y solar panel temperature
raw value-Y solar panel temperature
raw value+Z solar panel temperature
raw value

Bit
Offset
0
12

24

36
48
60
72
84
96
108
120
132
144
156
168
180
192
204
216

AMSAT Fox-1A
Downlink Specification
Bit
OffsetField

Size(Bits)

Type

Min
Value

Max
Value

-Z PANEL T

12

Unsigned

0x00

0xFFF

PSU
Temperature

12

Unsigned

0x00

0xFFF

SPIN

12

Signed

0x00

0xFFF

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

Raw Angle

324

12

Unsigned

0x00

0xFFF

Raw Angle

336

12

Unsigned

0x00

0xFFF

Raw Angle

348

12

Unsigned

0x00

0xFFF

Experiment 4 card
temperature raw value

360

PSU Current

12

Unsigned

0x00

0xFFF

PSU DC current

372

IHU
Diagnostic
Data

32

Unsigned--

Diagnostic Data on IHU
Performance

384

0x01
0x09

Bit 0 is Experiment 1
Bit 1 is Experiment 2 (N/A
on Fox-1A)
Bit 2 is Experiment 3 (N/A
on Fox-1A)
Bit 3 is Experiment 4
State: 0 = Working, 1 =Failed416

TX PA
Current
TX
Temperature
RX
Temperature
RSSI
IHU CPU
Temperature
Satellite X
Axis Angular
Velocity
Satellite Y
Axis Angular
Velocity
Satellite Z
Axis Angular
Velocity
EXP 4
Temperature

Experiment
FailureIndication

4

Unsigned

0x00
0x08

Page 11 of 20

Description-Z solar panel temperature
raw value
PSU card temperature raw
value
Calculated spin rate RPM
using solar cells
Bit 11 = sign
Bits 10 to 8 = integer
Bits 7 to 0 = fraction
Transmit power amplifier
current raw value
Transmitter card
temperature raw value
Receiver card temperature
raw value
Received Signal Strength
Indication raw value
CPU Temperature of IHU
raw value

228
240

252

264
276
288
300
312

AMSAT Fox-1A
Downlink Specification

Field
System I2C
FailureIndications
Number of
GroundCommanded
TLM Resets
Antenna
DeploySensors

Size(Bits)

Type

Min
Value

Max
Value

Description

Bit
Offset420

3

Unsigned

0x00

0x07

Bit 0 is BATT
Bit 1 is PSU Device 1
Bit 2 is PSU Device 2
State: 0 = Working, 1 =Failed4

Unsigned

0x00

0x0F

Number of times command
stations reset stored
telemetry423

2

Unsigned

0x00

0x03

Bit 0 is RCV Bit 1 is XMTState: 0 = stowed 1 =deployed

427

Page 12 of 20

AMSAT Fox-1A
Downlink Specification
4.3 Payload Type 2 - Telemetry Maximum Values Frame (Size = 458 bits)
Table 9

Field

Size
(Bits)

Type

Min
Value

Max Value

BATT A V

12

Unsigned

0x00

0xFFF

BATT B V

12

Unsigned

0x00

0xFFF

BATT C V

12

Unsigned

0x00

0xFFF

BATT A T

12

Unsigned

0x00

0xFFF

BATT B T

12

Unsigned

0x00

0xFFF

BATT C T

12

Unsigned

0x00

0xFFF

TOTAL
BATT I

12

Signed

0x00

0xFFF

BATT Board
Temperature

12

Unsigned

0x00

0xFFF

+X PANEL V

12

Unsigned

0x00

0xFFF

-X PANEL V

12

Unsigned

0x00

0xFFF

+Y PANEL V

12

Unsigned

0x00

0xFFF

-Y PANEL V

12

Unsigned

0x00

0xFFF

+Z PANEL V

12

Unsigned

0x00

0xFFF

-Z PANEL V

12

Unsigned

0x00

0xFFF

+X PANEL T

12

Unsigned

0x00

0xFFF

Page 13 of 20

Description
Battery pair A highvoltage raw value (02.5V scale)Battery pairs A+B
high voltage raw
value (0-3.3V scale)Battery pairs A+B+C
high voltage raw
value (0-5.0V scale)This value also
represents the powerbus voltage (VBATT)
Battery pair A hightemperature raw
value
Battery pair B hightemperature raw
value
Battery pair C hightemperature raw
value
Battery DC highcurrent raw value
High PC Board
Temperature of
BATT raw value+X solar panel highvoltage raw value-X solar panel highvoltage raw value+Y solar panel highvoltage raw value-Y solar panel highvoltage raw value+Z solar panel highvoltage raw value-Z solar panel highvoltage raw value+X solar panel hightemperature raw
value

Bit
Offset
0

12

24

36

48

60
72
84
96
108
120
132
144
156
168

AMSAT Fox-1A
Downlink Specification
Bit
OffsetField

Size(Bits)

Type

Min
Value

Max Value-X PANEL T

12

Unsigned

0x00

0xFFF

+Y PANEL T

12

Unsigned

0x00

0xFFF

-Y PANEL T

12

Unsigned

0x00

0xFFF

+Z PANEL T

12

Unsigned

0x00

0xFFF

-Z PANEL T

12

Unsigned

0x00

0xFFF

PSU
Temperature

12

Unsigned

0x00

0xFFF

SPIN

12

Signed

0x00

0xFFF

TX PA
Current

12

Unsigned

0x00

0xFFF

TX
Temperature

12

Unsigned

0x00

0xFFF

RX
Temperature

12

Unsigned

0x00

0xFFF

RSSI

12

Unsigned

0x00

0xFFF

IHU CPU
Temperature

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

Highest Raw Angle

324

12

Unsigned

0x00

0xFFF

Highest Raw Angle

336

12

Unsigned

0x00

0xFFF

Highest Raw Angle

348

Satellite X
Axis Angular
Velocity
Satellite Y
Axis Angular
Velocity
Satellite Z
Axis Angular
Velocity

Page 14 of 20

Description-X solar panel hightemperature raw
value+Y solar panel hightemperature raw
value-Y solar panel hightemperature raw
value+Z solar panel hightemperature raw
value-Z solar panel hightemperature raw
value
PSU card hightemperature raw
value
Highest calculated
spin rate RPM using
solar cells
Transmit power
amplifier high current
raw value
Transmitter card hightemperature raw
value
Receiver card hightemperature raw
valueHigh Received Signal
Strength Indication
raw valueHigh CPU
Temperature of IHU
raw value

180

192

204

216

228

240

252

264

276

288

300

312

AMSAT Fox-1A
Downlink Specification

Description

Bit
Offset0xFFF

Experiment 4 cardhigh temperature raw
value

360

0x00

0xFFF

PSU DC high current

372

Unsigned--

16

Unsigned

0x00

0xFFFF

25

Unsigned

0x00

0x1FFFFFF

1

Unsigned

0x00

0x01

Field

Size
(Bits)

Type

Min
Value

Max Value

EXP 4
Temperature

12

Unsigned

0x00

PSU Current

12

Unsigned

IHU Hard
Error Data

32

MAX
Timestamp
Reset CountMAX
Timestamp
UptimeSafe Mode
Indication

Page 15 of 20

Diagnostic Data on
IHU Hard Errors
At last MAX, total
number of times IHU
has reset since initial
on-orbit startup
At last MAX, the IHU
uptime in seconds
since the last reset
State: 1 = Safe Mode
Active

384

416

432
457

AMSAT Fox-1A
Downlink Specification
4.4 Payload Type 3 - Telemetry Minimum Values Frame (Size = 458 bits)
Table 10

Field

Size
(Bits)

Type

Min
Value

Max Value

BATT A V

12

Unsigned

0x00

0xFFF

BATT B V

12

Unsigned

0x00

0xFFF

BATT C V

12

Unsigned

0x00

0xFFF

BATT A T

12

Unsigned

0x00

0xFFF

BATT B T

12

Unsigned

0x00

0xFFF

BATT C T

12

Unsigned

0x00

0xFFF

TOTAL BATTI

12Signed

0x00

0xFFF

BATT Board
Temperature

12

Unsigned

0x00

0xFFF

+X PANEL V

12

Unsigned

0x00

0xFFF

-X PANEL V

12

Unsigned

0x00

0xFFF

+Y PANEL V

12

Unsigned

0x00

0xFFF

-Y PANEL V

12

Unsigned

0x00

0xFFF

+Z PANEL V

12

Unsigned

0x00

0xFFF

-Z PANEL V

12

Unsigned

0x00

0xFFF

+X PANEL T

12

Unsigned

0x00

0xFFF

Page 16 of 20

Description
Battery pair A low
voltage raw value (02.5V scale)Battery pair A+B low
voltage raw value (03.3V scale)Battery pair A+B+C
low voltage raw value(0-5.0V scale)This value also
represents the powerbus voltage (VBATT)
Battery pair A low
temperature raw
value
Battery pair B low
temperature raw
value
Battery pair C low
temperature raw
value
Battery DC low
current raw value
Low PC Board
Temperature of
BATT raw value+X solar panel low
voltage raw value-X solar panel low
voltage raw value+Y solar panel low
voltage raw value-Y solar panel low
voltage raw value+Z solar panel low
voltage raw value-Z solar panel low
voltage raw value+X solar panel lowtemperature raw
value

Bit
Offset
0

12

24

36

48

60
72
84
96
108
120
132
144
156
168

AMSAT Fox-1A
Downlink Specification
Bit
OffsetField

Size(Bits)

Type

Min
Value

Max Value-X PANEL T

12

Unsigned

0x00

0xFFF

+Y PANEL T

12

Unsigned

0x00

0xFFF

-Y PANEL T

12

Unsigned

0x00

0xFFF

+Z PANEL T

12

Unsigned

0x00

0xFFF

-Z PANEL T

12

Unsigned

0x00

0xFFF

PSU
Temperature

12

Unsigned

0x00

0xFFF

SPIN

12

Signed

0x00

0xFFF

TX PA
Current

12

Unsigned

0x00

0xFFF

TX
Temperature

12

Unsigned

0x00

0xFFF

RX
Temperature

12

Unsigned

0x00

0xFFF

RSSI

12

Unsigned

0x00

0xFFF

IHU CPU
Temperature

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

Lowest Raw Angle

324

12

Unsigned

0x00

0xFFF

Lowest Raw Angle

336

12

Unsigned

0x00

0xFFF

Lowest Raw Angle

348

Satellite X
Axis Angular
Velocity
Satellite Y
Axis Angular
Velocity
Satellite Z
Axis Angular
Velocity

Page 17 of 20

Description-X solar panel lowtemperature raw
value+Y solar panel lowtemperature raw
value-Y solar panel lowtemperature raw
value+Z solar panel lowtemperature raw
value-Z solar panel lowtemperature raw
value
PSU card low
temperature raw
value
Lowest calculated
spin rate RPM using
solar cells
Transmit power
amplifier low current
raw value
Transmitter card low
temperature raw
value
Receiver card low
temperature raw
value
Low Received Signal
Strength Indication
raw value
Low CPU
Temperature of IHU
raw value

180

192

204

216

228

240

252

264

276

288

300

312

AMSAT Fox-1A
Downlink Specification

Field

Size
(Bits)

Type

Min
Value

Max Value

Description

Bit
Offset

EXP 4
Temperature

12

Unsigned

0x00

0xFFF

Experiment 4 card
low temperature raw
value

360

PSU Current

12

Unsigned

0x00

0xFFF

PSU DC low current

372

IHU Soft
Error Data

32

Unsigned--

MIN
Timestamp
Reset Count

16

Unsigned

0x00

0xFFFF

25

Unsigned

0x00

0x1FFFFFF

1

Unsigned

0x00

0x01

MIN
Timestamp
UptimeSafe Mode
Indication

Page 18 of 20

Diagnostic Data on
IHU Soft Errors
At last MIN, total
number of times IHU
has reset since initial
on-orbit startup
At last MIN, the IHU
uptime in seconds
since the last reset
State: 1 = Safe Mode
Active

384

416

432
457

AMSAT Fox-1A
Downlink Specification
4.5 Payload Type 4 - Radiation Experiment Data Frame (Size = 464 bits)
Table 11

Field Size (Bytes)
Data

58

Type

Min Value Max Value

Unsigned--

Description
Experiment 1 Data

4.6 Payload Type 5 - Camera JPEG Data Frame (Size is variable)
Table 12

Field
Picture Lines
1

Size(Bytes)8Type

Min Value Max Value

Unsigned-

See section 5 for Picture Data Structure

Page 19 of 20-

Description
Picture Data1

AMSAT Fox-1A
Downlink Specification

5 Picture Data Structure
5.1 Scan Line Segment
Table 13

Field

Size
(Bits)

Type

Min
Value

Max
Value

Description

PictureCounter8

Unsigned

0x00

0xFF

Picture count indicator

Scan Line
Number6

Unsigned

0x00

0x3B

0x00 = top scan line

Scan Line
Length10

Unsigned

0x001

0x3FF

Count of bytes in the scan line

Scan Line
Data

Variable

Unsigned--(Fragment Length) Scan LineData

End of
JPEG Data

8

Unsigned

0xAA

0xAA

Indicates end of Picture Datafor use in Applications Payload
construction

5.1.1 Total Scan Line Segment data size for one Applications Payload frame
including end of JPEG data indicator byte shall not exceed 4300 bytes.

Page 20 of 20

-X FACE-Z FACE-Y FACE+Z FACEDEPLOYED+X FACESCALE 1 : 2

SCALE

A

SIZE

1:2

SHEET

FOX-ME-103

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2014-7-16

DATE

FOX
FOX1 ASSEMBLY+Y FACEAMSAT(ANTENNAS CROPPED)

0.5
1 OF 5

REV.

ISO +X+Y+Z
SCALE 3 : 4

3:4

SHEET

FOX-ME-103

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2014-7-16

DATE

FOX
FOX1 ASSEMBLY

AMSAT
SCALE

A

SIZE

ISO -X-Y-Z
SCALE 3 : 4

0.5
2 OF 5REV.

+X FACE
TRUE ANTENNA LENGTHSSCALE 0.2 : 1

SCALE

A

SIZE

1:5

SHEET

FOX-ME-103

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2014-7-16

DATE

FOX
FOX1 ASSEMBLY

AMSAT

0.5
3 OF 5REV.

-X FACE-Z FACE-Y FACE+Z FACE+X FACESCALE 1 : 2

STOWED

SCALE

A

SIZE

1:2

SHEET

FOX-ME-103

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2014-7-16

DATE

FOX
FOX1 ASSEMBLYAMSAT+Y FACE

0.5
4 OF 5

REV.

ISO +X+Y+Z
SCALE 3 : 4

3:4

SHEET

FOX-ME-103

DWG.NO.

UNLESS NOTED OTHERWISE:
mm [in]; TOL X.X B0,2 X.XX B0,1

2014-7-16

DATE

FOX
FOX1 ASSEMBLY

AMSAT
SCALE

A

SIZE

ISO -X-Y-Z
SCALE 3 : 4

0.5
5 OF 5REV.

AMSAT Fox-1 Engineering Documentation Update
Compiled by Jerry Buxton, N0JY
AMSAT Vice President - Engineeringn0jy@amsat.org
AMSAT, as an educational organization, would like to publicly release the majority of our design
documentation to serve as a learning tool to anyone interested in satellite development. However,in order to avoid complications with ITAR and Export Administration Rules, the information mustfirst be released via an openly available publication. We would also like to be able to discuss oursatellite projects with our own members, some of whom are not "US-persons" per thoseregulations. These AMSAT Space Symposium proceedings provide a convenient mechanism forthe needed publication in order to make this information public domain and allow us tocommunicate with our members.
While many of the Fox-1 documents were published in previous Proceedings, some of these
documents have undergone changes as the satellite design has progressed and evolved therefore
the updated versions will be reproduced in these 2015 Space Symposium proceedings. In addition,these proceedings also present any new engineering documents that have been produced since thelast publication which include some of the documentation for the Fox-1Cliff and Fox-1D satellites.
Through publication in the three proceedings, the majority of the Fox-1A documentation has now
been introduced to the public domain.

AMSAT Fox-1
Avionics System Design Specification
Date: September 29, 2014
Version: 3.92

AMSAT Fox-1
Avionics System Design Specification
1 Introduction
This document contains the system level design specifications for the AMSAT Fox-1 satellite avionics
systems. It is driven by the System Requirements Specification and other documents provided by thedevelopers of the individual systems that make up the satellite system.
1.1. Document History
DATE

VERSION

SUMMARY

February 21, 2012

1.0

From Draft F

April 9, 2012

1.1

Add signal characteristics, update bus pin connections per System Team
input

April 17, 2012

1.2

Add external connector specification in sections 2.6, 2.12 and 2.14 andreferences in section 6

April 18, 2012

1.21

Add MMCX connectors gender

April 22, 2012

1.3

Minor corrections in signal characteristics, remove +Z antenna deploy
and sensor connections

July 10, 2012

2.0

Many revisions from PDR

July 11, 2012

2.01

One RBF pin removed from bus pin assignments, updated 2.1
interconnect diagram, updated 2.1 signal characteristics

July 21, 2012

2.1

Revised bus signals, bus pin assignments
Updated RF block diagram

July 22, 2012

2.11

Revision to some RF signal descriptions, change antenna/coax
connectors to UMCC type, updated RF block diagram, added driving andload system columns to signal characteristics

September 9, 2012

3.0

Major changes.

September 11, 2012

3.01

Defunct IHU block diagram pending update

September 12, 2012

3.1

Added PCB volume requirements

September 23, 2012

3.11

Change TX PTT to RX PTT, -Z Deploy switches to TX, update figures
and tables accordingly

September 26, 2012

3.12

Update bus and pin assignment drawings

September 27, 2012

3.13

Update bus pin assignment drawings

September 30, 2012

3.14

Update RF block diagram to remove ITAR notice

October 17, 2012

3.15

Import changes to requirements from System Requirements

February 17, 2013

3.2

Incorporate system bus signal nomenclature and pin assignmentchanges

February 28, 2013

3.3

MEC connector changed orientation (flipped) on +X -X +Y -Y panels.

Page 1 of 54

AMSAT Fox-1
Avionics System Design Specification
DATE

VERSION

SUMMARY

March 28, 2013

3.4

Add second –Z PPOD deploy switch (pin 54), PPOD deploy switches
now on TX system card

March 31, 2013

3.41

Updates to the TX, RX, IHU, and BUS pin diagrams.

March 31, 2013

3.42

Adjusted RESERVED pin colors only

April 21, 2013

3.43

Addition of RX Frequency Control, TX Frequency Control, and Sensor
Power signals
Pin reassignments:
Moved pins 52 and 54 to pins 33 and 35 respectively
Moved pins 40 and 42 to pins 29 and 42 respectively
Added the above new signals to pins 42, 40, and 38 respectively

April 25, 2013

3.5

Update per System Requirements 3.10.2 changes. Updated bus
connection pin assignments, bus interconnect diagram, and system bus
signal characteristics account removal of TX OSC Temp and TX PA
Temp and addition of TX Temperature

June 26, 2013

3.6

Add requirements for PSU and BATT1 CPU reset from RX Command
Data, updated IHU block diagram

July 24, 2013

3.7

Add ALERT signal, SENSOR POWER signal, remove RBF2, rename
RBF1 to Solar Safe N, remove RX Command Data connection fromBATT1, flip MEC connector orientation on +X, -X, +Y, -Y panels, update
ME-113 mechanical drawings

August 26, 2013

3.8

Rename RX OSC TEMP to RX Temperature, add Initial Surge Current
Limits for certain systems, move Command Decoder to IHU system (buspin changes), update some bus nomenclature, update System
Requirements for each system per changes to the System Requirements

August 27, 2013

3.81

Correct source and destination for RX Command Strobe in Table 1

September 17, 2013

3.82

Add (move) RSSI to Pin 10, rename Pin 32 as RX CD, add Solar Power
A and Solar Power B to pins 55 and 56, update TX Block Diagram,
remove RX Command Data connection from PSU, update hyperlinks.

October 8, 2013

3.83

Remove IHU AUDIO OUT 2, RX AUDIO 2 signals, rename IHU AUDIOOUT 1 to IHU AUDIO OUT, RX AUDIO 1 to RX AUDIO.

November 11, 2013

3.84

Updated IHU Block Diagram

January 23, 2014

3.85

Add Sensor Power connection to PSU

January 23, 2014

3.86

Several text (requirements) changes to match recent System
Requirements change for Safe Mode.

April 27, 2014

3.87

Add PCB plating requirements for TX, RX, IHU, PSU, BATT, EXP
systems

May 29, 2014

3.88

Correct 6.7 to read PSU System

August 16, 2014

3.9

Updates to 5.1, 6.1 to match updated system requirements

August 20, 2014

3.91

Correct 5.1 to show 120 seconds for Safe Mode beacon

September 29, 2014

3.92

Update PSU block diagram, add receiver block diagram, update
commands in 5.1, update instances of system requirements 3.9.3, 3.9.4,
3.9.6

Page 2 of 54

AMSAT Fox-1
Avionics System Design Specification
1.2. Document Scope
The purpose of this document is to specify the avionics systems and their connections to each other and toexternal components for the satellite. It is intended to be used by the hardware, software, and mechanicaldesigners to develop the architecture and interconnections for the satellite avionics systems.
1.3. Document Format
This document provides these elements in a numbered format. The numbered sections specify each major
system in the satellite while numbered items for each system specify the external connections required andthe number of lines for each connection. Satellite bus and external connections are further described infigures and tables.
Where System Requirements are reproduced their numbers are from the AMSAT Fox-1 System
Requirements Specification.
1.4. References
1. AMSAT Fox-1 ConOps
2. AMSAT Fox-1 System Requirements Specification
3. AMSAT Fox-1 Bus (Signal Connections Diagram)
4. AMSAT Fox-1 Bus Pin Assignment
5. AMSAT Fox-1 Avionics System Design Specification Spreadsheet
6. AMSAT FOX-ME-120_Z_TOPBOTT_SOLAR_PANEL.pdf
7. AMSAT FOX-ME-127_Y_SIDE_SOLAR_PANEL.pdf

Page 3 of 54

AMSAT Fox-1
Avionics System Design Specification
Contents
1 Introduction ............................................................................................................................................. 1
2 Avionics System Bus Signals, Characteristics, and Connections ................................................................ 5
3 RF Transmitter System ............................................................................................................................. 8
4 RF Receiver System ................................................................................................................................ 14
5 Internal Housekeeping Unit (IHU) System .............................................................................................. 18
6 Power Supply System (PSU).................................................................................................................... 24
7 Battery System ........................................................................................................................................ 36
8 Experiment Payload Systems 1 through 4................................................................................................ 41
9 System Block Diagrams Reference .......................................................................................................... 47
10 System Interconnection References ....................................................................................................... 51

Page 4 of 54

AMSAT Fox-1
Avionics System Design Specification
2 Avionics System Bus Signals, Characteristics, and Connections

Figure 1: Interconnect Diagram

Page 5 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 1: System Bus Signal Characteristics
Type

Voltage

Source System

1

Pin

SPI1 NSS

Nomenclature

Digital

Note¹

IHU

2

TX PA Current

Analog0 - 3.0 V

TX

3

SPI1 SCK

Digital

Note¹

IHU

4

TX Temperature

Analog0 - 3.0 V

TX

5

SPI1 MISO

Digital

Note¹

IHU

6

Experiment 4 Thermistor

Analog

N/A

EXP 4

7

SPI1 MOSI

Digital

Note¹

IHU

8

RX Temperature

Analog0 - 3.0 V

RX

9Serial RXD

Digital

3.0 V

EXP 1-4

10

RSSI

Analog0 - 3.0 V

RX

11Serial TXD

Digital

3.0 V

IHU

12

IHU Audio Out

Analog0 - 3 V (audio)

IHU

13

Experiment Enable 1

Digital14

Not Used

15

Experiment Enable 2

16

RX Command Data 0

17
18

Load Z
30 - 60 kΩ

Load System

Notes

EXP 1-4

SPI Standard, IHU Master

IHU
EXP 1-430 - 60 kΩ
N/A
30 - 60 kΩ
30 - 60 kΩ

SPI Standard, IHU Master

IHU

Thermistor Circuit

EXP 1-4

SPI Standard, IHU Master

IHU

Temperature from Experiment 4 position

EXP 1-4

SPI Standard, IHU Master

IHU

Thermistor Circuit

IHU

Async, Mark HighIHU

Received Signal Strength Indication

EXP 1-4

Async, Mark HighTX

For 5 kHz deviation, 10 Hz - 7 kHz bandwidth

IHU

EXP 1-4

HIGH = Enable EXP 1

Digital

IHU

EXP 2

Digital

IHU

Experiment Enable 3

DigitalIHURX Command Data 1

DigitalIHU

19Experiment Enable 4

DigitalIHU

20RX Command Data 2

DigitalIHU

21Not Used22

RX Command Data 3
I²C1 SCL

DigitalRX Command Strobe
I²C1 SDA

Digital25
26

IHU RF Control

Digital27

Not Used28

IHU PTT

Digital29

Solar Safe N

Switch30

RF TX Active

Digital31

Alert Signal

Digital32

RX CD

Digital33-Z Deploy Switch 1

Switch

N/A

TX

34

RX Audio

Analog0 - 3 V (audio)35-Z Deploy Switch 2

SwitchN/A36

Not Used
I²C2 SCL

23
24

37

DigitalDigital> 10 kΩ unbal.

Note¹

HIGH = Enable EXP 3

EXP 4

HIGH = Enable EXP 4
HIGH = IHU off

IHU

TX

(Most Significan Bit) HIGH = Inhibit Transmit
I²C Standard, IHU Master

IHU

HIGH = Command Data change

IHU

I²C Standard, IHU Master
HIGH = IHU Controls RF
LOW = Standalone Analog Transponder

IHU

TX

IHU
N/A

EXP 3

Not Used on Fox-1A

IHU
Note¹

HIGH = Enable EXP 2(Least Significant Bit) Not Used on Fox-1A

TX

HIGH = TRANSMIT

PSU

N.O. for operation

TX

IHU

HIGH = RF TX on

IHU

BATT

BATT

N/A

RX

TX IHUHIGH = valid receive signal

PSU/BATT

N.O. when deployedRX

N/A> 10 kΩ unbal.

IHU

10 Hz - 7 kHz bandwidth

TX

N/A

PSU/BATT

N.O. when deployed

Digital

Note¹

IHU

PSU/BATTI²C Standard, IHU Master

Analog+3 VDCIHU

TX RX BATT EXP4

Power for analog telemetry sensors

39

Sensor Power
I²C2 SDA

Digital

Note¹

IHU

PSU/BATTI²C Standard, IHU Master40

TX Frequency Control

DigitalIHU

TX

Not Used on Fox-1A

41+Z Thermistor

Analog42

RX Frequency Control

Digital

43-Z Thermistor

AnalogN/A

44-Y Antenna Deploy

AnalogVbatt

45+Z CIC

Power

N/A

46

-Y Antenna Sensor

Switch47-Z CIC

48
49

38

N/A

EXP 4

N/A

PSU
PSU

IHU

N/A
7 Ω resistor

EXP 4

N/A

PSU

N/A

PSU

N.O.

IHU

Power

N/A

TX

N/A

PSU

+Y Antenna Sensor

Switch

N/A

PSU

N.O.

Umbilical USBP

Digital50+Y Antenna Deploy

Analog51

Umbilical USBM

DigitalBATT

IHU

USB Standard

52

Not Used

53

Umbilical Power Active

DigitalBATT

IHU

HIGH = Running on Umbilical Port Power54

Not Used

55

Solar Power A

Power

Vbatt

PSU

BATT

56

Solar Power B

Power

Vbatt

PSU

BATT

57

Vbatt

Power Bus 3.3 - 4.2 VDC

BATT/PSU

ALL

58

Vbatt

Power Bus 3.3 - 4.2 VDC

BATT/PSU

ALL

59

Vbatt

Power Bus 3.3 - 4.2 VDC

BATT/PSU

ALL

60

Vbatt

Power Bus 3.3 - 4.2 VDC

BATT/PSU

ALL

IHU
TX

RX

BATT
Vbatt

IHU

7 Ω resistor

Not Used on Fox-1A

PSU
N.O. when deployed

IHU

N.O. when deployed

IHU

USB Standard

PSU

Version 2.96
Note¹ All SPI and I²C signals are 3.0 V levels

All Digital signals are 3.0 V CMOS logic levels high impedance load unless otherwise noted

Page 6 of 54

AMSAT Fox-1
Avionics System Design Specification

Figure 2: Complete Bus Connection Pin Assignments

Page 7 of 54

AMSAT Fox-1
Avionics System Design Specification
3 RF Transmitter System
3.1 System Requirements Applicable to RF Transmitter System
2.2.1
2.2.3
2.3.1
2.4.1
2.4.3
2.4.4
2.4.5
3.8.1
3.8.2

The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
All RF transmitters shall meet or exceed the requirements specified in the ITU Radio Regulations,Technical Characteristics, Volume 3, article 3.
All satellite downlinks shall be in the 2 meter band within the amateur satellite service.
All satellite transmitter and receiver frequencies shall deviate by no more than 5 parts-per-million
from the specified values including initial accuracy and temperature variation.
All satellite frequencies shall be coordinated with the IARU.
The satellite shall include an FM downlink transmitter.
The transmitter shall have specifications as shown in Table 2.
Power Output
400 mW (min.)FM Deviation

5 kHz

Audio Bandwidth 3 kHz
3.8.3
3.9.1
3.9.3
3.9.5
3.9.7
3.10.1
3.10.2The transmitter shall provide a means to prevent over modulation.
The satellite shall provide an FM transponder via the RF uplink and RF downlink.
In Transponder Mode, the downlink transmitter shall be keyed (i.e. PTT-on) by the IHU for aminimum of 30 seconds following detection of the 67 Hz CTCSS tone.
In Transponder Mode, the 67 Hz CTCSS tone is not required for a received signal to be repeated on
the downlink, once the transmitter has been keyed.
In the event of shutdown or failure of the IHU, the satellite shall default to simple carrier operated
repeater operation.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card
Page 8 of 54

AMSAT Fox-1
Avionics System Design Specification
RX T
3.10.33.11.1
3.11.2
3.11.33.12.1
3.12.2
3.12.33.12.53.13.83.13.9Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.
The satellite shall send slow speed telemetry using FSK on the RF downlink.
The FSK shall use the frequency spectrum below the audible range.
The telemetry shall be transmitted simultaneously with any transponder communications.
The satellite shall provide the means to process commands sent via the RF uplink from a groundcontrol station.
The commands received via the RF uplink shall not be repeated on the RF downlink.
The following commands shall be provided, as shown in Table 5.
CommandOperation
SAFE MODE

Enter Safe Mode

INHIBIT

Inhibit RF transmission

IHU OFFPower off IHU & PSU

IHU ONPower on IHU & PSU

CLEAR

Clear stored telemetry

TRANSPONDER MODE

Enter Transponder Mode

DATA MODE

Enter Data Mode

An INHIBIT command shall cause the satellite to cease RF transmissions.
In Transponder Mode, the transponder and the slow speed telemetry shall be active.
In Data Mode, the high speed telemetry shall be active and the transponder shall not be active. (i.e.
signals that appear on the uplink shall not be repeated on the downlink.)

Page 9 of 54

AMSAT Fox-1
Avionics System Design Specification
3.2 Initial Surge Current Limits
3.2.1 The RF Transmitter design shall limit initial inrush current to 2.5 Amperes.
3.3 Volume Requirements Applicable to RF Transmitter System
3.3.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 5 mm from the –Z surface of the PC
board.
3.3.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
3.4 Interface Control Documents Applicable to RF Transmitter System
AMSAT Fox-1 IHU to RF System Interface Control Document
3.5 PCB Plating Requirements Applicable to RF Transmitter System
3.5.1 ENIG then selective flash gold four mounting pads.

Page 10 of 54

AMSAT Fox-1
Avionics System Design Specification
3.6 RF Transmitter System PCB Bus Connections

Figure 3: RF Transmitter System Bus Connection Pin Assignments

Page 11 of 54

AMSAT Fox-1
Avionics System Design Specification
3.7 RF Transmitter System PCB External Connections
3.7.1 2 meter band RF output, coaxial cable to Transmit Antenna
3.7.2 Spacecraft deployment switches cable(s) TBR
3.7.3 Three connections via Samtec FSI-105-06-L-S-AD connector
3.7.3.1 1 contact -Z Solar Panel Thermistor
3.7.3.2 1 contact -Z Solar Panel CIC +3.7.3.3 1 contact common or - for above four connections
Table 2: External Connection Signal Characteristics
External
Connection
CoaxialCable

Nomenclature
2 meter Antenna ≈ 145.9
MHz

Type
RF

Voltage/Power Source System Load Z
Bus Pin
0 to +30
2 meter
50 Ω unbal.
N/A
dBm
Antenna

Table 3: -Z PCB face FSI-105-06-L-S-AD connector mates to pads on –Z Solar Panel
Pin

Nomenclature

1-Z Thermistor

2

N/C

3

-Z Solar Panel Common

4

N/C

5

-Z CICType

Voltage

Source System

Load Z

Load System

Bus Pin

Analog

N/A

N/A

N/A

PSU

43
Ground
Plane

Power

N/A

N/A

Page 12 of 54

N/A

PSU

47

AMSAT Fox-1
Avionics System Design Specification

Figure 4: RF Transmitter System FSI-105-06-L-S-AD Connection Pin
Assignments

Page 13 of 54

AMSAT Fox-1
Avionics System Design Specification
4 RF Receiver System
4.1 System Requirements Applicable to RF Receiver System
2.2.1
2.2.3
2.3.1
2.4.2
2.4.5
3.7.1
3.7.2

The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
All satellite uplinks shall be in the 70 cm band of the amateur satellite service.
All satellite frequencies shall be coordinated with the IARU.
The satellite shall include an FM uplink receiver.
The receiver shall have specifications as shown in Table 1.
Sensitivity-120 dBm for 12 dB SINAD (min.)FM Deviation

5 kHz

Audio Bandwidth

3 kHz

Input Frequency Acceptance Receiver shall accept signals that are off
frequency by ±2.5 kHz (min.)
3.8.3
3.9.1
3.9.7
3.10.1
3.10.2

3.10.33.12.2
3.13.12

The transmitter shall provide a means to prevent over modulation.
The satellite shall provide an FM transponder via the RF uplink and RF downlink.
In the event of shutdown or failure of the IHU, the satellite shall default to simple carrier operated
repeater operation.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card

RX T

Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.
The commands received via the RF uplink shall not be repeated on the RF downlink.
The RF uplink shall be monitored for commands in all modes.
Page 14 of 54

AMSAT Fox-1
Avionics System Design Specification
4.2 Initial Surge Current Limits
4.2.1 The RF Receiver design shall limit initial inrush current to 0.1 Amperes.
4.3 Volume Requirements Applicable to RF Receiver System
4.3.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
4.3.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
4.4 Interface Control Documents Applicable to RF Receiver System
AMSAT Fox-1 IHU to RF System Interface Control Document
4.5 PCB Plating Requirements Applicable to RF Receiver System
4.5.1 ENIG then selective flash gold four mounting pads.

Page 15 of 54

AMSAT Fox-1
Avionics System Design Specification
4.6 RF Receiver System PCB Bus Connections

Figure 5: RF Receiver System Bus Connection Pin Assignments

Page 16 of 54

AMSAT Fox-1
Avionics System Design Specification
4.7 RF Receiver System PCB External Connections
4.7.1 70cm band RF input, coaxial cable to Receive Antenna
Table 4: RF Receiver System External Connection Signal Characteristics
External
Connection
CoaxialCable

NomenclatureType

70 cm RF Input 437 MHz

RF

Voltage/Power Source System
Load Z-60 dBmto -140 70 cm Antenna 50 Ω unbal.
dBm

Page 17 of 54

Bus Pin
N/AAMSAT Fox-1
Avionics System Design Specification
5 Internal Housekeeping Unit (IHU) System
5.1 System Requirements Applicable to Internal Housekeeping Unit (IHU) System
2.2.1
2.2.3
2.3.1
3.3.2
3.4.3
3.6.2
3.6.3
3.9.2
3.9.3
3.9.4

3.9.5
3.9.6

3.9.7
3.10.1
3.10.2

3.10.33.10.4The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
The satellite shall include an umbilical port as per the CubeSat Design Specification.
The satellite shall provide the means to run diagnostic tests via the umbilical port while integrated
with the P-POD.
The satellite shall provide a means to activate and deactivate the experiment payloads.
The satellite shall provide a means to telemeter data from the experiment payloads.
In Transponder Mode, the IHU shall detect the presence of a 67 Hz CTCSS tone on the uplink.
In Transponder Mode, the downlink transmitter shall be keyed (i.e. PTT-on) by the IHU for aminimum of 30 seconds following detection of the 67 Hz CTCSS tone.
In Transponder Mode, the downlink transmitter shall stay on continuously as long as the 67 Hz
CTCSS tone is detected at least once during the period the transmitter is being keyed (i.e. PTTon).
In Transponder Mode, the 67 Hz CTCSS tone is not required for a received signal to be repeatedon the downlink, once the transmitter has been keyed.
In Transponder Mode, if the downlink transmitter has been un-keyed for a period of 2 minutes, thesatellite shall send "HI THIS IS AMATEUR RADIO SATELLITE FOX 1" as a voiceannouncement on the downlink transmitter.
In the event of shutdown or failure of the IHU, the satellite shall default to simple carrier operated
repeater operation.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card

RX T

Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.
The minimum and maximum values of each of the measured parameters shall be saved in nonPage 18 of 54

AMSAT Fox-1
Avionics System Design Specification

3.10.53.10.6
3.11.1
3.11.2
3.11.33.11.43.11.53.12.1
3.12.33.12.43.12.53.12.6
3.12.73.12.83.12.93.12.10

volatile memory.
The telemetry data shall also include at a minimum, calculated parameters as shown in Table 4.
Parameter Name Description
UP TIME

Total seconds since avionics power-up or reset

SPIN

Satellite spin rate and direction

A telemetry frame shall include the current measured values, the saved minimum and maximum
values, and the current calculated values.
The satellite shall send slow speed telemetry using FSK on the RF downlink.
The FSK shall use the frequency spectrum below the audible range.
The telemetry shall be transmitted simultaneously with any transponder communications.
The telemetry transmission shall include telemetry frames.
The telemetry transmission shall include experiment data.
The satellite shall provide the means to process commands sent via the RF uplink from a groundcontrol station.
The following commands shall be provided, as shown in Table 5.
CommandOperation

SAFE MODE

Enter Safe Mode

INHIBIT TX

Inhibit RF transmission

ENABLE TX

Enable RF transmission

IHU OFFPower off IHUIHU ONPower on IHU

CLEAR

Clear stored telemetry

TRANSPONDER MODE

Enter Transponder Mode

DATA MODE

Enter Data Mode

ENABLE AUTO-SAFE

Enable Auto-Safe Mode

DISABLE AUTO-SAFE

Disable Auto-Safe Mode

A SAFE MODE command shall cause the satellite to enter the Safe Mode.
An INHIBIT TX command shall disable the RF transmitter.
An ENABLE TX command shall enable the RF transmitter.
An IHU OFF command shall cause the IHU System to power off.
An IHU ON command shall cause the IHU System to power on.
A CLEAR command shall cause the satellite to clear the saved minimum and maximum telemetry
parameter values.
A TRANSPONDER MODE command shall cause the satellite to enter the Transponder Mode.
Page 19 of 54

AMSAT Fox-1
Avionics System Design Specification
3.12.113.12.123.12.133.13.1

3.13.2
3.13.33.13.4A DATA MODE command shall cause the satellite to enter the Data Mode.
An ENABLE AUTO-SAFE command shall enable the auto-safe mode state.
A DISABLE AUTO-SAFE command shall disable the auto-safe mode state.
The satellite shall provide on-orbit operating modes as shown in Table 6.
Name
Description
Startup Mode

Wait 45 minutes and deploy antennas

Safe Mode

Wait 120 seconds then begin 10 second
beacon sequence

Transponder Mode

FM transponder; PTT and low speed
telemetry via IHU

Data Mode

FM transmitter; PTT and high speed
telemetry via IHU

The satellite shall transition between modes as shown in Figure 1.
Upon power-up of the avionics, the satellite shall begin operation from the "Power-up" state as
shown in Figure 1.
An IHU ON Command shall cause the satellite to begin operation from the "Power-up" state as
shown in Figure 1.

Page 20 of 54

AMSAT Fox-1
Avionics System Design Specification

3.13.53.13.5.1
3.13.5.2
3.13.63.13.73.13.7.1
3.13.7.2
3.13.7.3
3.13.83.13.93.13.103.13.113.13.11.1
3.13.12

If the antennas have been deployed, the satellite shall determine whether the last state was Safe
Mode.
If the last state was Safe Mode the satellite shall enter Safe Mode
If the last state was not Safe Mode the satellite shall enter Transponder Mode.
If the antennas have not been deployed, the satellite shall enter the Startup Mode.
In Startup Mode, the satellite shall wait 50 minutes, then deploy the antennas.
During the 50 minute wait the IHU shall flash a red LED.
During the 50 minute wait the IHU shall sound a 1 kHz beeping tone.
After the antennas have been deployed the satellite shall enter Safe Mode.
In Transponder Mode, the transponder and the slow speed telemetry shall be active.
In Data Mode, the high speed telemetry shall be active and the transponder shall not be active. (i.e.
signals that appear on the uplink shall not be repeated on the downlink.)
If another Data Mode command is not received, the satellite shall automatically enter Transponder
Mode 30 minutes after having entered Data Mode.
In Safe Mode the satellite shall wait 120 seconds then transmit a 10 second beacon.
The 120 second wait and 10 second beacon cycle will be repeated as long as the satellite is in Safe
Mode.
The RF uplink shall be monitored for commands in all modes.

Page 21 of 54

AMSAT Fox-1
Avionics System Design Specification
5.3 Initial Surge Current Limits
5.3.1 The IHU design shall limit initial inrush current to 0.1 Amperes.
5.4 Volume Requirements Applicable to IHU System
5.4.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
5.4.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
5.5 Interface Control Documents Applicable to IHU System
AMSAT Fox-1 IHU to RF System Interface Control Document
AMSAT Fox-1 IHU to PSU Interface Control Document
AMSAT Fox-1 IHU to Battery Interface Control Document
AMSAT Fox-1 IHU to Attitude Determination Experiment Interface Control Document
AMSAT Fox-1 IHU to Experiment 1 Interface Control Document
AMSAT Fox-1 IHU to Experiment 4 Interface Control Document
5.6 PCB Plating Requirements Applicable to IHU System
5.6.1 ENIG then selective flash gold four mounting pads.

Page 22 of 54

AMSAT Fox-1
Avionics System Design Specification
5.7 Internal Housekeeping Unit (IHU) System PCB Bus Connections

Figure 6: IHU System Bus Connection Pin Assignments

Page 23 of 54

AMSAT Fox-1
Avionics System Design Specification
6 Power Supply System (PSU)
6.1 System Requirements Applicable to Power Supply System (PSU)

2.2.1
2.2.3
2.3.1
3.3.1
3.4.1

3.4.2
3.5.1
3.5.2
3.5.3
3.5.4
3.6.1
3.10.1
3.10.2

3.10.33.13.7.1

The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
The satellite shall include a "Remove Before Flight" pin as per the CubeSat Design Specification.
The satellite battery and photovoltaic panels shall be electronically disconnected from the avionics
when the "Remove Before Flight" pin is inserted, regardless of the state of the deployment
switch(es).
The satellite shall provide the means to charge the battery via the umbilical port while integrated
with the P-POD.
The satellite shall produce electrical power from sunlight.
The satellite shall produce electrical power while in sunlight regardless of orientation and whiletumbling or spinning.
The satellite shall produce sufficient average electrical power to operate continuously in the orbit ofmaximum eclipse.
The satellite shall provide sufficient battery capacity to operate continuously in the orbit ofmaximum eclipse.
The satellite shall provide DC power for experiment payloads.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card

RX T

Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.
During the 45 minute wait the IHU shall flash a red LED.

Page 24 of 54

AMSAT Fox-1
Avionics System Design Specification
6.2 Initial Surge Current Limits
6.2.1 The PSU design shall limit initial inrush current to 0.1 Amperes.
6.3 Volume Requirements Applicable to PSU System
6.3.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
6.3.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 3.0 mm from the +Z surface of the PC
board within the area 0 to 4.0 mm from the +Y and +X edges of the board, and 6.0 mm from the +Z
surface of the PC board in the rest of the board area.
6.4 Interface Control Documents Applicable to PSU System
AMSAT Fox-1 IHU to PSU Interface Control Document
6.5 PCB Plating Requirements Applicable to PSU System
6.5.1 ENIG then selective flash hard gold 30 micro-inch four mounting pads and four edge fingers.

Page 25 of 54

AMSAT Fox-1
Avionics System Design Specification
6.6 Power Supply System (PSU) PCB Bus Connections

Figure 7: PSU Bus Connection Pin Assignments

Page 26 of 54

AMSAT Fox-1
Avionics System Design Specification
6.7 Power Supply System (PSU) PCB External Connections
6.7.1 Three connections to +X Solar Panel using Samtec MEC1-105-02-L-D-NP-A connector
6.7.1.1 1 contact +X Solar Panel Thermistor
6.7.1.2 1 contact +X Solar Panel CIC +6.7.1.3 1 contact common or - for above two connections
6.7.2 Three connections to -X Solar Panel using Samtec MEC1-105-02-L-D-NP-A connector
6.7.2.1 1 contact -X Solar Panel Thermistor
6.7.2.2 1 contact -X Solar Panel CIC +6.7.2.3 1 contact common or - for above two connections
6.7.3 Five connections to +Y Solar Panel using Samtec MEC1-105-02-L-D-NP-A connector
6.7.3.1 1 contact +Y Solar Panel Thermistor
6.7.3.2 1 contact +Y Solar Panel CIC +6.7.3.3 1 contact TX Antenna Deploy
6.7.3.4 1 contact TX Antenna Sensor
6.7.3.5 1 contact common or - for above connections
6.7.4 Five connections to -Y Solar Panel using Samtec MEC1-105-02-L-D-NP-A connector
6.7.4.1 1 contact -Y Solar Panel Thermistor
6.7.4.2 1 contact -Y Solar Panel CIC +6.7.4.3 1 contact RX Antenna Deploy
6.7.4.4 1 contact RX Antenna Sensor
6.7.4.5 1 contact common or - for above connections
6.7.5 All PCB edges that connect to solar panel MEC1-105-02-L-D-NP-A connectors shall havecontact pads on the PCB for all connector pins, whether connected to a trace or not.

Page 27 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 5: +X PCB edge mates to MEC1-105-02-L-D-NP-A connector on +X Solar Panel
Pin

Nomenclature

Type

Voltage

Source System

Load ZBus Pin

1

N/C

2
3

+X Solar Panel Thermistor
N/C

Analog

N/A

N/A

N/A

N/A

4
5

N/C
N/C

6

+X Solar Panel Common
N/C

7
8
9
10

Ground
Plane

N/C
N/C
+X Solar Panel CIC (+)

Power

N/A

Page 28 of 54

N/A

N/A

N/A

AMSAT Fox-1
Avionics System Design Specification

Figure 8: PSU System +X Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

Page 29 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 6: -X PCB edge mates to MEC1-105-02-L-D-NP-A connector on -X Solar Panel
Pin

Nomenclature

Type

Voltage

Source System

Load ZBus Pin

1

N/C

2
3

-X Solar Panel Thermistor
N/C

Analog

N/A

N/A

N/A

N/A

4
5

N/C
N/C

6

-X Solar Panel Common
N/C

7
8 N/C
9 N/C
10 -X Solar Panel CIC (+)

Ground
Plane

Power

N/A

N/A

Page 30 of 54

N/A

N/A

AMSAT Fox-1
Avionics System Design Specification

Figure 9: PSU System -X Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

Page 31 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 7: +Y PCB edge mates to MEC1-105-02-L-D-NP-A connector on +Y Solar Panel
Pin

Nomenclature

Type

Voltage

Source System

Load ZBus Pin

1

N/C

2
3

+Y Solar Panel Thermistor
N/C

Analog

N/A

N/A

N/A

N/A

4
5

+Y Antenna Sensor
N/C

Switch

N/A

PSU

N.O.

48

6

+Y Solar Panel Common
N/C

7
8 +Y Antenna Deploy
9 N/C
10 +Y Solar Panel CIC (+)

GroundPlane
AnalogVbatt

IHU

7 Ω resistor

50

Power

N/A

N/A

N/A

N/A

Page 32 of 54

AMSAT Fox-1
Avionics System Design Specification

Figure 10: PSU System +Y Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

Page 33 of 54

AMSAT Fox-1
Avionics System Design Specification
Table 8: -Y PCB edge mates to MEC1-105-02-L-D-NP-A connector on -Y Solar Panel
Pin

Nomenclature

Type

Voltage

Source System

Load ZBus Pin

1

N/C

2
3

-Y Solar Panel Thermistor
N/C

Analog

N/A

N/A

N/A

N/A

4
5

-Y Antenna Sensor
N/C

Switch

N/A

PSU

N.O.

46

6

-Y Solar Panel Common
N/C

7
8 -Y Antenna Deploy
9 N/C
10 -Y Solar Panel CIC (+)

GroundPlane
AnalogVbatt

IHU

7 Ω resistor

44

Power

N/A

N/A

N/A

N/A

Page 34 of 54

AMSAT Fox-1
Avionics System Design Specification

Figure 11: PSU System -Y Edge MEC1-105-02-L-D-NP-A Connection Pin Assignments

Page 35 of 54

AMSAT Fox-1
Avionics System Design Specification
7 Battery System
7.1 System Requirements Applicable to Battery PCB 1 System (BATT1)

2.2.1
2.2.3
2.3.1
3.3.1
3.4.1
3.4.2
3.5.3
3.5.4
3.10.1
3.10.2

3.10.3The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
The satellite shall include a "Remove Before Flight" pin as per the CubeSat Design Specification.
The satellite battery and photovoltaic panels shall be electronically disconnected from the avionics
when the "Remove Before Flight" pin is inserted, regardless of the state of the deployment switch(es).
The satellite shall provide the means to charge the battery via the umbilical port while integrated with
the P-POD.
The satellite shall produce sufficient average electrical power to operate continuously in the orbit ofmaximum eclipse.
The satellite shall provide sufficient battery capacity to operate continuously in the orbit of maximum
eclipse.
The satellite shall collect telemetry data.
The telemetry data shall include at a minimum, measured parameters as shown in Table 3.
Parameter Name Description
CELL V

Voltages of battery cells

PANEL V

Voltages of solar panels

TOTAL I

Total DC current out of power system

PA I

DC current into RF power amp

BATTERY T

Temperature of battery

PANEL T

Temperatures of solar panels

TX T

Temperature of RF transmitter card

RX T

Temperature of RF receiver card

The measured parameters shall be sampled at least every 15 seconds.

Page 36 of 54

AMSAT Fox-1
Avionics System Design Specification
7.2 Volume Requirements Applicable to Battery PCB 1 System
7.2.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 4.0 mm from the -Z surface of the PC
board within the area 0 to 4.0 mm from the +Y and +X edges of the board, and 1.0 mm from the -Z
surface of the PC board in the rest of the board area.
7.2.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 17.0 mm from the +Z surface of the PC
board.
7.3 Interface Control Documents Applicable to Battery PCB 1 System
AMSAT Fox-1 IHU to Battery Interface Control Document
7.4 PCB Plating Requirements Applicable to Battery PCB 1 System
7.4.1 ENIG then selective flash gold four mounting pads.

Page 37 of 54

AMSAT Fox-1
Avionics System Design Specification
7.5 Battery PCB 1 System Bus Connections

Figure 12: Battery 1 System Bus Connection Pin Assignments

Page 38 of 54

AMSAT Fox-1
Avionics System Design Specification
7.6 Battery PCB 1 System External Connections
7.6.1 Umbilical as USB mini type B receptacle
7.6.2 Remove Before Flight as 3.5mm normally open TS jack
Table 9: Battery 1 External Connection Signal Characteristics
External
Connection

Nomenclature

Type

USB 1

USB +5 VDC

AnalogUSB 2

USB Data - (USBM)

DigitalUSB 3

USB Data + (USBP)

DigitalUSB 4GroundRBF 1

Solar Safe N

AnalogVoltage/Power Source System
USB
5 VDC
CONNECTOR
3.0 V
USB
CMOS
CONNECTOR
logic
3.0 V
USB
CMOS
CONNECTOR
logic
USB
CONNECTOR
3.5mm N.O. TS
N/A
jack

*When external supply is connected to USB port

Page 39 of 54

Load ZBus Pin

N/A

N/A

N/A

51

N/A

49

N/A

Ground
Plane

N/A

40

AMSAT Fox-1
Avionics System Design Specification
7.7 Battery PCB 2 System Bus Connections

Figure 13: Battery 2 Bus Connection Pin Assignments

Page 40 of 54

AMSAT Fox-1
Avionics System Design Specification
8 Experiment Payload Systems 1 through 4
8.1 System Requirements Applicable to Experiment Payload Systems 1-4
2.1.4
2.1.5
2.2.1
2.2.3
2.3.1
3.6.1
3.6.2
3.6.3

The satellite shall provide mass for an experiment payload up to 100 g.
The satellite shall provide volume for an experiment payload up to 95 x 95 x 15.7 mm.
The satellite avionics shall be designed for -40C to +70C operating temperature.
The satellite shall be designed to tolerate the radiation environment in orbit.
The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
The satellite shall provide DC power for experiment payloads.
The satellite shall provide a means to activate and deactivate the experiment payloads.
The satellite shall provide a means to telemeter data from the experiment payloads.
8.2 Initial Surge Current Limits
8.2.1 All Experiment designs shall limit initial inrush current to 0.1 Amperes.
8.3 Volume Requirements Applicable to Experiment Payload System 1
8.3.1 No components, connections other than those connectors stipulated in section 10, andstructures such as shielding or enclosures shall protrude from the –Z surface of the PC board.
8.3.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
8.4 Interface Control Documents Applicable to Experiment 1 Payload System
AMSAT Fox-1 IHU to Experiment 1 Interface Control Document

8.5 Volume Requirements Applicable to Experiment Payload Systems 2 and 3
8.5.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
8.5.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 6.0 mm from the +Z surface of the PC
board.
8.6 Volume Requirements Applicable to Experiment System 4
8.6.1 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 1 mm from the –Z surface of the PC
board.
Page 41 of 54

AMSAT Fox-1
Avionics System Design Specification

8.6.2 Components, connections other than those connectors stipulated in section 10, and structures
such as shielding or enclosures shall not protrude more than 5.0 mm from the +Z surface of the PC
board.
8.7 Interface Control Documents Applicable to Experiment 4 Payload System
AMSAT Fox-1 IHU to Experiment 4 Interface Control Document
8.8 PCB Plating Requirements Applicable to Experiment 1 Payload System
8.8.1 ENIG then selective flash gold four mounting pads. ENIG only will also be accepted if alreadyfabricated.
8.9 PCB Plating Requirements Applicable to Experiment 2 Payload System
8.9.1 ENIG then selective flash gold four mounting pads. ENIG only will also be accepted if alreadyfabricated.
8.10 PCB Plating Requirements Applicable to Experiment 3 Payload System
8.10.1 ENIG then selective flash gold four mounting pads. ENIG only will also be accepted if
already fabricated.
8.11 PCB Plating Requirements Applicable to Experiment 4 Payload System
8.11.1 ENIG then selective flash gold four mounting pads..

Page 42 of 54

AMSAT Fox-1
Avionics System Design Specification
8.12 Experiment Payload 1 Systems PCB Bus Connections

Figure 14: Experiment Payload 1-3 Systems Bus Connection Pin Assignments

Page 43 of 54

AMSAT Fox-1
Avionics System Design Specification
8.13 Experiment Payload 4 System PCB Bus Connections

Figure 15: Experiment Payload 4 System Bus Connection Pin Assignments

Page 44 of 54

AMSAT Fox-1
Avionics System Design Specification
8.14 Experiment Payload 4 System PCB External Connections
8.14.1 Three connections using Samtec FSI-105-06-L-S-AD connector
8.14.1.1 1 contact +Z Solar Panel Thermistor
8.14.1.2 1 contact +Z Solar Panel CIC +8.14.1.3 1 contact common or - for above two connections
Table 10: +Z PCB face FSI-105-06-L-S-AD connector mates to pads on +Z Solar Panel
Pin

Nomenclature

1+Z Thermistor

2

N/C

3

+Z Solar Panel Common

4

N/C

5

+Z CICType

Voltage

Source System

Load Z

Load System

Bus Pin

Analog

N/A

N/A

N/A

PSU

41
Ground
Plane

Power

N/A

N/A

Page 45 of 54

N/A

PSU

45

AMSAT Fox-1
Avionics System Design Specification

Figure 16: Experiment Payload 4 System FSI-105-06-L-S-AD
Connection Pin Assignments

Page 46 of 54

AMSAT Fox-1
Avionics System Design Specification
9 System Block Diagrams Reference
9.1 IHU System

Page 47 of 54

AMSAT Fox-1
Avionics System Design Specification
9.2 RF System
9.2.1 RF Transmitter Block Diagram

Page 48 of 54

AMSAT Fox-1
Avionics System Design Specification
9.2.2 RF Receiver Block Diagram

Page 49 of 54

AMSAT Fox-1
Avionics System Design Specification
9.3 PSU System

Page 50 of 54

AMSAT Fox-1
Avionics System Design Specification
10 System Interconnection References
10.1 Bus Connectors
10.1.1 Samtec QTH-030-02-L-D-A and QSH-030-01-L-D-A connectors
10.1.2 QTH connector shall be mounted on the +Z surface of each circuit board except the Receive
Antenna PCB / GPS Payload circuit board
10.1.3 QSH connector shall be mounted on the –Z surface of each circuit board
10.2 Bus Connector Documentation
10.2.1 Samtec QSH
10.2.2 Samtec QTH
10.2.3 Samtec QxH High Speed Characterization Report
10.2.4 Samtec QxH Single Ended Channel Properties
10.3 External Connectors
10.3.1 Samtec MEC1-105-02-L-D-NP-A connector mounted on +X, -X, +Y, -Y Solar Panels
10.3.2 Samtec FSI-105-06-L-S-AD connector mounted on -Z face of RF Transmitter System PCB
and +Z face of Experiment Payload 4 System PCB
10.4 External Connector Documentation
10.4.1 Samtec MEC1
10.4.2 Samtec MEC1 Qualification Testing
10.4.3 Samtec FSI
10.5 PCB Connector Layout Documentation
10.5.1 FOX-ME-113_PCB.pdf

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AMSAT Fox-1
Avionics System Design Specification
10.6 Systems PCB Connector Layout
10.6.1 Common to All Systems

Page 52 of 54

AMSAT Fox-1
Avionics System Design Specification
10.6.2 RF Transmitter System

10.6.3 PSU System

Page 53 of 54

AMSAT Fox-1
Avionics System Design Specification
10.6.4 Experiment 4 System

Page 54 of 54

AMSAT Fox-1
System Requirements
Date: September 29, 2014
Version: Version 1.82

AMSAT Fox-1
System Requirements Specification
1 Introduction
This document specifies the system level technical requirements for the AMSAT Fox-1
satellite project. This 1 Unit CubeSat is a part of the AMSAT Fox program and includes a
subset of the technical capabilities envisioned for the overall program.
Fox-1 is specifically intended as a replacement for the failing AMSAT Echo (i.e. AO-51)
satellite. Echo has been the most widely used amateur satellite due to its ability to provide
basic radio communications with very simple ground station equipment. Its FM repeater
provides very wide geographical coverage allowing amateur radio operators tocommunicate over substantial distances using just a handheld transceiver (i.e. a walkietalkie) and a small handheld antenna. This so called "EasySat" mode is extremely
valuable in providing an introduction to satellite communications and is often used fordemonstrations given at schools, to scouting organizations and at amateur radio publicity
events. Fox-1 will not duplicate all of the features and modes of Echo but its primary
mission is to provide an FM Transponder in order to allow continued access to thisEasySat mode of communications.
In addition to its mission as a communications satellite, Fox-1 will host an experiment
payload. The satellite will reserve mass and volume for the experiment and will provide
DC power and a communications facility. The experiment is expected to be provided by
students at Penn State University – Erie through an AMSAT sponsored senior design
project.

Page 1 of 13

AMSAT Fox-1
System Requirements
1.1

Document History
DATE

VERSION

SUMMARY

October 5, 2011

1.0

From Draft E

October 8, 2011

1.01

Fix typos in sections 1.2 and 3.5

October 9, 2011

1.02

Add Requirements Tracking

October 23, 2011

1.03

Additional Requirements Tracking

February 21, 2012

1.04

Update Section 3 and Formatting changes

April 18, 2012

1.05

Correction in Section 4

April 22, 2012

1.06

Correct link in Section 1.4 item 2

April 29, 2012

1.1

Revised 3.12.3, 3.12.7, 3.12.8, 3.13.3,
3.13.4, figure 1 to remove RESET and add
IHU OFF and IHU ON commands

August 2, 2012

1.11

Added hidden text for requirements tracking
to be shown in System Design Specification

September 4, 2012

1.12

Added the previously missing “Table 6”label

October 17, 2012

1.2

Changed mode descriptions in 3.13.1 Table
6; changed 3.9.2, 3.9.3, 3.9.4, 3.9.5, 3.9.6,
3.9.7 to reflect IHU involvement; changed
COMMAND MODE to DATA MODE

April 25, 2013

1.3

3.10.2 Remove PA Temperature, add TX T
as RF Transmitter Temperature, OSC T as
referring to TX oscillator no longer
measured changed to read RX oscillator
only

August 20, 2013

1.4

Requirements 3.5.5, 3.6.1, 3.9.6, 3.10.2,
3.11.1, 3.12.4, 3.12.6, 3.13.7.1, 3.13.7.2,
3.13.8, 3.13.9 modified, removed or added
to reflect the evolving satellite design

January 10, 2014

1.5

Changes to 3.12.3, 3.12.4, 3.13.2, 3.13.5,
3.13.5.1, 3.13.5.2, 3.13.7, 3.13.7.3,
3.13.7.3.1, 3.13.7.3.2, 3.13.11, 3.13.12 to
add Safe Mode

January 20, 2014

1.6

Change 3.13.7.3 to go directly to Safe
Mode, remove 3.13.7.3.1 and 3.13.7.3.2

January 23, 2014

1.7

Modified 3.13.2 (figure 1), 3.13.11, added
3.13.11.1

February 10, 2014

1.71

Added “Experiments are powered off” toTable 6 under Safe Mode
Page 2 of 13

AMSAT Fox-1
System Requirements

DATE

VERSION

SUMMARY

April 17, 2014

1.72

Bring Table 5 commands in line with
Command and Control Document, remove
PSU reference from 3.12.8 and 3.12.9

August 16, 2014

1.8

Update to actual operating values 3.13.11,
3.13.11.1, 3.12.3, 3.13.1, 3.13.7, 3.13.7.1,
3.13.7.2

September 8, 2014

1.81

Update to actual operating values 3.9.3,
3,9,6, update Table 5, add 3.12.12 and3.12.13

September 29, 2014

1.82

Update 3.9.3, 3.9.4 to allow for variablehang timer

1.2 Document Scope
The purpose of this document is to specify the technical requirements of the satellite at
the system (i.e. "black box") level. It is intended to be used by the hardware, software andmechanical designers to develop the architecture/high-level design specifications. It isalso intended to be used for test planning and development.
1.3 Document Format
This document provides the requirements in numbered format. Each requirement is
assigned a unique number. Additional information such as comments or examples thatare provided for guidance or clarity is italicized to distinguish them from requirements.
1.4 References
1. AMSAT Fox-1, Concept of Operations, Version 1.0, September 19, 2011
2. CubeSat Design Specification Rev. 12. by The CubeSat Program Cal Poly SLO
available from: http://www.cubesat.org/images/developers/cds_rev12.pdf
3. Launch Services Program, Program Level Poly Picosatellite Orbital Deployer(PPOD) and CubeSat Requirements Document LSP-REQ-317.01 Revision Basic(from NASA)
4. ITURadio
Regulations,
Editionof2008.
availablefrom
http://www.itu.int/publ/R-REG-RR-2008/en

Page 3 of 13

AMSAT Fox-1
System Requirements

2 General Requirements
2.1

CubeSat Requirements

2.1.1 The satellite shall meet the requirements specified in the CubeSat Design
Specification Rev. 12.
2.1.2 The satellite shall meet the requirements specified in the NASA LSP-REQ317.01 Revision Basic.
2.1.3 The satellite shall meet the requirements for a 1 unit (single) CubeSat.
2.1.4 The satellite shall provide mass for an experiment payload up to 100 g.
2.1.5 The satellite shall provide volume for an experiment payload up to 95 x 95
x 15.7 mm.
2.2

Environmental Requirements

2.2.1 The satellite avionics shall be designed for -40C to +70C operating
temperature.
2.2.2 The satellite shall be designed to operate in a 650 km, sun-synchronous,
circular orbit.
2.2.3 The satellite shall be designed to tolerate the radiation environment inorbit.
2.3

Reliability Requirements

2.3.1 The satellite shall be designed for a minimum 5-year, on-orbit lifetime.
2.4

RF Frequency Requirements

2.4.1 All RF transmitters shall meet or exceed the requirements specified in the
ITU Radio Regulations, Technical Characteristics, Volume 3, article 3.
2.4.2 All satellite uplinks shall be in the 70 cm band of the amateur satellite
service.
2.4.3 All satellite downlinks shall be in the 2 meter band within the amateur
satellite service.
2.4.4 All satellite transmitter and receiver frequencies shall deviate by no morethan 5 parts-per-million from the specified values including initial accuracy
and temperature variation.
2.4.5 All satellite frequencies shall be coordinated with the IARU.
Note that the band plan with the actual coordinated frequencies will be specified in a
separate document.

Page 4 of 13

AMSAT Fox-1
System Requirements

3 Functional Requirements
3.1

Antenna System

3.1.1 The satellite shall include a deployable antenna system.
3.2

Attitude Control

3.2.1 The satellite shall incorporate passive magnetic stabilization to align the
deployed antennas with the magnetic field of the earth.
3.3

Access Ports

3.3.1 The satellite shall include a "Remove Before Flight" pin as per the CubeSat
Design Specification.
3.3.2 The satellite shall include an umbilical port as per the CubeSat Design
Specification.
3.4

Pre-launch Features

3.4.1 The satellite battery and photovoltaic panels shall be electronicallydisconnected from the avionics when the "Remove Before Flight" pin is
inserted, regardless of the state of the deployment switch(es).
3.4.2 The satellite shall provide the means to charge the battery via the umbilicalport while integrated with the P-POD.
3.4.3 The satellite shall provide the means to run diagnostic tests via theumbilical port while integrated with the P-POD.
3.5

Power

3.5.1 The satellite shall produce electrical power from sunlight.
3.5.2 The satellite shall produce electrical power while in sunlight regardless oforientation and while tumbling or spinning.
3.5.3 The satellite shall produce sufficient average electrical power to operatecontinuously in the orbit of maximum eclipse.
3.5.4 The satellite shall provide sufficient battery capacity to operatecontinuously in the orbit of maximum eclipse.

Page 5 of 13

AMSAT Fox-1
System Requirements
3.6

Experiment3.6.1 The satellite shall provide DC power for experiment payloads.
3.6.2 The satellite shall provide a means to activate and deactivate theexperiment payloads.
3.6.3 The satellite shall provide a means to telemeter data from the experiment
payloads.
Note that the experiment payloads will be specified in a separate documents.
3.7

RF Uplink

3.7.1 The satellite shall include an FM uplink receiver.
3.7.2 The

receiver

shall

have

specifications

as

shown

in

Table

Table 1

Sensitivity
FM Deviation
Audio Bandwidth
Input Frequency Acceptance

3.8-120 dBm for 12 dB SINAD (min.)
5 kHz
3 kHz
Receiver shall accept signals that are off
frequency by ±2.5 kHz (min.)

RF Downlink

3.8.1 The satellite shall include an FM downlink transmitter.
3.8.2 The transmitter shall have specifications as shown in Table 2.
Table 2

Power Output
400 mW (min.)FM Deviation
5 kHz
Audio Bandwidth 3 kHz

Page 6 of 13

1.

AMSAT Fox-1
System Requirements
3.8.3 The transmitter shall provide a means to prevent over modulation.
3.9

FM Transponder

3.9.1 The satellite shall provide an FM transponder via the RF uplink and RF
downlink.
3.9.2 In Transponder Mode, the IHU shall detect the presence of a 67 Hz CTCSS
tone on the uplink.
3.9.3 In Transponder Mode, the downlink transmitter shall be keyed (i.e. PTT-on)
by the IHU for a minimum of 30 seconds following detection of the 67 Hz
CTCSS tone.
3.9.4 In Transponder Mode, the downlink transmitter shall stay on continuously
as long as the 67 Hz CTCSS tone is detected at least once during theperiod the transmitter is being keyed (i.e. PTT-on).
3.9.5 In Transponder Mode, the 67 Hz CTCSS tone is not required for a received
signal to be repeated on the downlink, once the transmitter has been
keyed.
3.9.6 In Transponder Mode, if the downlink transmitter has been un-keyed for aperiod of 2 minutes, the satellite shall send "HI THIS IS AMATEUR RADIOSATELLITE FOX 1" as a voice announcement on the downlink transmitter.
3.9.7 In the event of shutdown or failure of the IHU, the satellite shall default tosimple carrier operated repeater operation.
3.10 Telemetry Data
3.10.1 The satellite shall collect telemetry data.
3.10.2 The telemetry data shall include at a minimum, measured parameters asshown in Table 3.
Table 3

Parameter NameCELL VPANEL VTOTAL IPA I
BATTERY T
PANEL T
TX T
RX T

Description
Voltages of battery cells
Voltages of solar panels
Total DC current out of power system
DC current into RF power amp
Temperature of battery
Temperatures of solar panels
Temperature of RF transmitter card
Temperature of RF receiver card

Page 7 of 13

AMSAT Fox-1
System Requirements
3.10.3 The measured parameters shall be sampled at least every 15 seconds.
3.10.4 The minimum and maximum values of each of the measured parameters
shall be saved in non-volatile memory.
3.10.5 The telemetry data shall also include at a minimum, calculated parameters
as shown in Table 4.
Table 4

Parameter Name Description
UP TIME
Total seconds since avionics power-up or reset
SPIN
Satellite spin rate and direction
3.10.6 A telemetry frame shall include the current measured values, the saved
minimum and maximum values, and the current calculated values.
Note that the telemetry interface will be specified in a separate document.
3.11 Telemetry Transmission
3.11.1 The satellite shall send slow speed telemetry using FSK on the RF
downlink.
3.11.2 The FSK shall use the frequency spectrum below the audible range.
3.11.3 The telemetry shall be transmitted simultaneously with any transponder
communications.
3.11.4 The telemetry transmission shall include telemetry frames.
3.11.5 The telemetry transmission shall include experiment data.
3.12 Command Capability
3.12.1 The satellite shall provide the means to process commands sent via the
RF uplink from a ground control station.
3.12.2 The commands received via the RF uplink shall not be repeated on the
RF downlink.
3.12.3 The following commands shall be provided, as shown in Table 5.

Page 8 of 13

AMSAT Fox-1
System Requirements
Table 5

Command
SAFE MODE
INHIBIT TX
ENABLE TX
IHU OFFIHU ON
CLEAR
TRANSPONDER MODEDATA MODE
ENABLE AUTO-SAFE
DISABLE AUTO-SAFE

Operation
Enter Safe Mode
Inhibit RF transmission
Enable RF transmission
Power off IHUPower on IHUClear stored telemetry
Enter Transponder Mode
Enter Data Mode
Enable Auto-Safe Mode
Disable Auto-Safe Mode

3.12.4 A SAFE MODE command shall cause the satellite to enter the Safe Mode.
3.12.5 An INHIBIT TX command shall disable the RF transmitter.
3.12.6 An ENABLE TX command shall enable the RF transmitter.
3.12.7 An IHU OFF command shall cause the IHU System to power off.
3.12.8 An IHU ON command shall cause the IHU System to power on.
3.12.9 A CLEAR command shall cause the satellite to clear the saved minimum
and maximum telemetry parameter values.
3.12.10 A TRANSPONDER MODE command shall cause the satellite to enter
the Transponder Mode.
3.12.11 A DATA MODE command shall cause the satellite to enter the Data
Mode.
3.12.12 An ENABLE AUTO-SAFE command shall enable the auto-safe mode
state.
3.12.13 A DISABLE AUTO-SAFE command shall disable the auto-safe mode
state.
Note that the control interface will be specified in a separate document.
3.13 On-Orbit Operating Modes
3.13.1 The satellite shall provide on-orbit operating modes as shown in Table 6.
Table 6

Name
Startup Mode
Safe Mode

Description
Wait 50 minutes and deploy antennas
Wait 120 seconds then begin 10 second
beacon sequence
Experiments are powered off
Page 9 of 13

AMSAT Fox-1
System Requirements
Transponder Mode
Data Mode

FM transponder; PTT and low speed
telemetry via IHUFM transmitter; PTT and high speed
telemetry via IHUPage 10 of 13

AMSAT Fox-1
System Requirements

3.13.2 The satellite shall transition between modes as shown in Figure 1.

Figure 1. On-Orbit Operating Modes

Page 11 of 13

AMSAT Fox-1
System Requirements
3.13.3 Upon power-up of the avionics, the satellite shall begin operation from the"Power-up" state as shown in Figure 1.
3.13.4 An IHU ON Command shall cause the satellite to begin operation from the"Power-up" state as shown in Figure 1.
3.13.5 If the antennas have been deployed, the satellite shall determine whether
the last state was Safe Mode.
3.13.5.1 If the last state was Safe Mode the satellite shall enter Safe Mode.
3.13.5.2 If the last state was not Safe Mode the satellite shall enterTransponder Mode.
3.13.6 If the antennas have not been deployed, the satellite shall enter theStartup Mode.
3.13.7 In Startup Mode, the satellite shall wait 50 minutes, then deploy theantennas.
3.13.7.1 During the 50 minute wait the IHU shall flash a red LED.
3.13.7.2 During the 50 minute wait the IHU shall sound a 1 kHz beeping tone.
3.13.7.3 After the antennas have been deployed the satellite shall enter Safe
Mode.
3.13.8 In Transponder Mode, the transponder and the slow speed telemetry shallbe active.
3.13.9 In Data Mode, the high speed telemetry shall be active and thetransponder shall not be active. (i.e. signals that appear on the uplink shallnot be repeated on the downlink.)
3.13.10 If another Data Mode command is not received, the satellite shall
automatically enter Transponder Mode 24 hours after having entered Data
Mode.
3.13.11 In Safe Mode the satellite shall wait 120 seconds then transmit a 10
second beacon.
3.13.11.1 The 120 second wait and 10 second beacon cycle will be repeatedas long as the satellite is in Safe Mode.
3.13.12 The RF uplink shall be monitored for commands in all modes.

4 External Interface Documents
To fully specify the satellite technical requirements, the following documents
must also be provided;
1. IARU Coordinated Frequency Plan
2. Downlink Specification
3. Control Interface Specification
4. Experiment Payload Specifications
Page 12 of 13

AMSAT Fox-1
System Requirements

5 Summary
The Fox-1 satellite will be AMSAT's first CubeSat. Its primary mission is toprovide an FM Transponder communications capability. The secondary mission
is to host a university-provided experiment payload.

Page 13 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
Date: November 7, 2014
Version: Version 1.10

AMSAT Fox-1A
IHU to Experiment 1 Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the Experiment System in Position 1 of the satellite, known as the Vanderbilt
University Vulcan Payload and abbreviated herein as EXP1.
1.1

Document History
DATE

VERSION

SUMMARY

March 3, 2013

1.00

Initial version

March 7, 2013

1.01

Correct use of I²C (1.2) and EXP1 (2.3.3)

March 31, 2013

1.02

Command Message CRC8 to include addressbyte, change to commands, modified figure 3,
deleted figure 4

March 31, 2013

1.03

Delete TYPE from message tables, add SET
TIME response return values

March 31, 2013

1.04

Add CMD_VERSION_ERR to Error Code table

April 2, 2013

1.05

Correct 6.5 Figure 3, remove 0x0005, 0x0201,
0x0210, 0x0281, 0x0300, and 0x0301
commands

September 17, 2013

1.06

Change type format to exclude code type, add
Min/Max Values

October 7, 2013

1.07

Revised Table 1 and 3.2.1 added 3.5.1.1 forclarification on Experiment Enable 1 states

November 7, 2013

1.08

Added 3.1.2 and 3.1.3 regarding minimum
power levels for experiment operation

May 21, 2014

1.09

Revised 3.1.2 and 3.1.3 to read <= 3.3V

November 7, 2014

1.10

Update HALT value to 0x05 in Table 6

Page 1 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
1.2 Document Scope
This document will specify the control of EXP1, the messaging format, and the I²C bus
hardware operation for the communications between the IHU and the EXP1.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification
4. Vanderbilt University Vulcan Payload Interface Control Document

Page 2 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall initiate a command to the EXP1.
2.1.2 The EXP1 shall send a reply to each IHU request.
2.1.3 Message bit order shall be Big Endian.
2.1.4 The IHU shall determine the action to be taken in the event of an invalid,
improper, or missing message from the EXP1.
2.1.5 The EXP1 shall take no action in the event of an invalid or improper
message from the IHU.
2.1.6 Message byte order shall be Big Endian.
2.2

General Message Requirements

2.2.1 Each message shall contain a header block.
2.2.2 Each message shall contain a packet error check (PEC) in the form of
CRC8.
2.2.2.1 The message address byte shall be included when calculating the
CRC8.
2.3

I²C 1 Bus Hardware Interface Requirements

2.3.1 The I²C Vdd shall be 3.0V.
2.3.2 The bus speed shall be Fast (400kbit/s).
2.3.3 The EXP1 I²C 7 bit address shall be 0x2A.

Page 3 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD

3 Experiment Operation
3.1

Experiment Power Control

3.1.1 The IHU shall exert control over the power state of the EXP1 by theExperiment Enable 1 pin on the satellite bus as shown in Table 1.
Table 1Pin State

Description

High

Power On Experiment

Low or highimpedancePower Off Experiment3.1.2 The IHU shall not power on the experiment if the power bus voltage(VBATT) is less than or equal to 3.3 Volts.
3.1.3 The IHU shall perform the Experiment Cease Operation Sequence andthe Experiment Power Off Sequence if the power bus voltage (VBATT)
falls to less than or equal to 3.3 Volts while the experiment is powered on.
3.2

Experiment Power On Sequence

3.2.1 The IHU shall set and hold the Experiment Enable 1 pin HIGH.
3.2.2 The IHU shall not send any message to the EXP1 for a minimum of 100
milliseconds.
3.2.3 The IHU shall send a Set Time command to the EXP1.
3.3

Experiment Begin Operation Sequence

3.3.1 Upon completion of the Power On sequence the IHU shall send a Set Run
State Active command message to the EXP1.
3.4

Experiment Cease Operation Sequence

3.4.1 The IHU shall send a Set Run State Halt command message to the EXP1.
3.4.2 The IHU shall not send any message to the EXP1 for a minimum of 10000
milliseconds.
3.4.3 The IHU shall send a Set Run State Standby command message to the
EXP1.
3.5

Experiment Power Off Sequence

3.5.1 The IHU shall set the Experiment Enable 1 pin LOW.
3.5.1.1 The absence of a HIGH state on the Experiment Enable 1 pin shall be
construed as a LOW state whether the pin is actually LOW, or in ahigh-impedance state.
Page 4 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD

4 Message Content Requirements
4.1

Command Message

4.1.1 The message header block shall be constructed as shown in table 2.
4.1.2 The message header block shall be sent with each Command andResponse block.
Table 2

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

Message
Version2

Unsigned

0x01

0xFFFF

Message ICD
versionSoftware Build

2

Unsigned

0x01

0xFFFF

Software Buildversion

4.1.2.1 The Message Version shall be an integer representing the IHU to
EXP1 ICD document version number from which the message format
is derived, having the decimal point removed (e.g. version 1.03 would
be 103 decimal or 0x67).
4.1.2.2 The Software Build shall be an integer representing the software build
version number of the system originating the message, having any
decimal points removed (e.g. version 1.03 would be 103 decimal or0x67).
4.2

Command Message Block4.2.1 The command message block shall be constructed as shown in Table 3.
Table 3

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

COMMAND

2

Unsigned

0x00000x0280

Hexadecimal
Command

ARGUMENT

Variable

Unsigned--

Optional Arguments
As Required

The command message block shall contain one command in the COMMAND
COMMAND field as shown in Table 4.

Page 5 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
Table 4

Command
Name

Size(Bytes)

Type

Nop

2

Unsigned

Echo

2

Resend

Min
Value

Max
Value

Description

0x00000x0000No effect; response
undefined. Test for I²C
acknowledgement only.

Unsigned

0x00010x0001

Echo this byte stream

2

Unsigned

0x00020x0002

Resend last result

Get UID

2

Unsigned

0x00030x0003Controller 7 byte identifier

Get Status

2

Unsigned

0x00040x0004Controller statusindication

Get
Diagnostics

2

Unsigned

0x00060x0006

Self-check Diagnostic

Get
Telemetry

2

Unsigned

0x00100x0010Send telemetry data

Set RunState

2

Unsigned

0x00800x0080Enter specified Run State

Get RunState

2

Unsigned

0x00810x0081

Query current Run StateSet Time

2

Unsigned

0x01000x0100

Number of seconds sinceepoch

Get Time

2

Unsigned

0x01010x0101

Number of seconds sinceepoch

Get Data2

Unsigned

0x02800x0280Send (number of bytes)
data

4.2.3 The command message shall contain arguments for the Echo command,as shown in Table 5.
Table 5

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

ARGUMENT

4

Unsigned--

Data to beechoedPage 6 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
4.2.4 The command message shall contain one argument for the Set Run State
command, as shown in Table 6.
Table 6Run State

Size(Bytes)

Type

Min
Value

Max
Value

Description

STANDBY

2

Unsigned

0x01

0x01

Enter Standby StateACTIVE

2

Unsigned

0x03

0x03

Activate Experiments

HALT

2

Unsigned

0x05

0x05

Terminate
Experiments

4.2.5 The command message shall contain arguments for the Set Timecommand, as shown in Table 7.
Table 7

Argument

Size(Bytes)

Min
Value

Type

Max
Value

IHU Reset
Counter

16

Unsigned

0x00

-

MET
Timestamp

32

Unsigned--

Description
Count of the number of
IHU resets from nonvolatile FRAM
MET timestamp (seconds
since last IHU reset)

4.2.6 The command message shall contain arguments for the Get Data
command, as shown in Table 8.
Table 8

Argument

Size(Bytes)

Type

Min
Value

Max
Value

Description

BYTES TO
SEND

2Unsigned

0x00

0xFFFF

Number of bytes tosend (1-256)

Page 7 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
4.3

Response Message Block4.3.1 The response message block shall be constructed as shown in Table 9.
Table 9

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

RESERVED

1

Unsigned--

Reserved, ignore

ERROR
CODE

1

Unsigned

0x00000x0006

Response to
CommandLENGTH

2

Unsigned

0x00

0xFFFF

Length of Return
Value in Bytes

RETURN
VALUE

Variable

Variable--

Return Value

4.3.2 The Error Code shall contain one code as shown in table 10.
Table 10

Name

Size
(Bytes)

Type

Min
Value

Max
Value

Description

CMD_OK

1

Unsigned 0x0000

0x0000Commandinvokedsuccessfully

CMD_OP_ERR

1

Unsigned 0x0001

0x0001

Command notrecognized

CMD_FORMAT_ERR

1

Unsigned 0x0002

0x0002

Incorrect
commandargument
lengthCMD_RANGE_ERR

1

Unsigned 0x0003

0x0003

Argument(s)out of bounds

CMD_PEC_ERR

1

Unsigned 0x0004

0x0004

Error check(CRC)
mismatch

CMD_EXEC_ERR

1

Unsigned 0x0005

0x0005

Execution error

0X0006

HeaderMessage
Versionmismatch

CMD_VERSION_ERR

1

Unsigned 0x0006

Page 8 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
4.3.3 The Status Flags for a GET STATUS response message shall be
represented as individual bit values of a 16 bit RETURN VALUE asshown in Table 11.
Table 11

Name

Bit
NumberDescription

REBOOTED0

1 = Experiment has rebooted – NOT USEDDATA READY

1

1 = Experiment data available

TIME REQUEST

2

1 = Request SET TIME

FAILED RUN STATE

3

1 = Failed the run state – NOT USEDCOMPLETED RUN STATE

4

1 = Completed the run state – NOT USEDRESERVED

5-15

Always 0

4.3.4 The response message to a Set Time command shall contain one of thevalues as shown in Table 12.
Table 12

Response
Name

Size(Bytes)

Type

Min
Value

Max
Value

SUCCESS

2

Signed0x00

0x00

Time Set
successfully

FAILURE

2

Signed0xFFFF

0xFFFFTime Set failed

Description

5 Message Integrity
5.1

Invalid Messages

5.1.1 If the PEC (CRC8) fails, the message shall be considered invalid.
5.1.2 If the Message Version does not match the message version in use forthe construction of messages on the receiving system, the message shallbe considered invalid.

Page 9 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD

6 Message Flow Diagrams
6.1

EXPERIMENT POWER ON SEQUENCE

IHU

EXP1
ASSERT EXPERIMENT 1 ENABLE

SET TIMERESPONSEIHU Handling

6.2

End

EXPERIMENT BEGIN OPERATION SEQUENCE

IHU

EXP1
SET RUN STATE: ACTIVERESPONSEIHU Handling

End

Page 10 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
6.3

EXPERIMENT CEASE OPERATION SEQUENCE

IHU

EXP1
SET RUN STATE: HALTRESPONSESET RUN STATE: STANDBYRESPONSEIHU Handling

6.4

End

EXPERIMENT POWER OFF SEQUENCE

IHU

EXP1
DEASSERT EXPERIMENT 1 ENABLE

IHU Handling

End

Page 11 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD
6.5

SERVICING EXPERIMENT OPERATION

Figure 1

IHU

EXP1
GET STATUS

STATUS = REBOOTED or FAILED or COMPLETEDIHU HandlingEnd

Figure 2

IHU

EXP1
GET STATUS
STATUS = TIME REQUESTSET TIMERESPONSEIHU Handling

End

Page 12 of 13

AMSAT Fox-1A
IHU to Experiment 1 ICD

Figure 3

IHU

EXP1

GET DATADATAIHU Handling

End

Page 13 of 13

AMSAT Fox-1A
IHU to Experiment 4 ICD
Date: June 26, 2014
Version: Version 1.20

AMSAT Fox-1A
IHU to Experiment 4 Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the Experiment System in Position 3 of the satellite, known as the VT Camera
Experiment and abbreviated herein as EXP3.
1.1

Document History
DATE

VERSION

SUMMARY

January 24, 2013

1.00

Initial version

February 20, 2013

1.01

Specify byte order as little endian

May 21, 2013

1.10

Update data TYPE names

October 4, 2013

1.11

Change type format to exclude code type, add
Min/Max Values, add thermistor circuit

October 7, 2013

1.12

Modify Table 1 to clarify Experiment Enable 4
pin states

1.20

Add “No Earth Image Available” to NN
description in Table 6, remove section 7
thermistor requirement no longer applicable,change all references to EXP4 to read EXP3
reflecting proper location of experiment

June 26, 2014

1.2 Document Scope
This document will specify the control of EXP3, the messaging format, and the serial bus
hardware operation for the communications between the IHU and the EXP3.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification

Page 1 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall initiate a command to the EXP3.
2.1.2 The EXP3 shall send a reply to each IHU request.
2.1.3 Message bit order shall be Little Endian.
2.1.4 The IHU shall determine the action to be taken in the event of an invalid,
improper, or missing message from the EXP3.
2.1.5 The EXP3 shall take no action in the event of an invalid or improper
message from the IHU.
2.1.6 Message byte order shall be Little Endian.
2.2

General Message Requirements

2.2.1 Each message shall contain a header block.
2.2.2 Each message shall contain one command, one reply, or one data block.
2.3

Serial Bus Hardware Interface Requirements

2.3.1 The bus levels shall be 3.0V.
2.3.2 The bus data speed shall be 38400 bit/s.
2.3.3 The serial bus communication shall be asynchronous.
2.3.4 The number of data bits shall be 8.
2.3.5 The number of stop bits shall be 1.
2.3.6 There shall be no parity bit.

Page 2 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

3 Experiment Operation
3.1

Experiment Power Control

3.1.1 The IHU shall exert control over the power state of the EXP3 by theExperiment Enable 4 pin on the satellite bus as shown in Table 1.
Table 1Pin State

Description

High

Power On Experiment

Low or high-impedance Power Off Experiment3.1.2 Upon signaling Power On to the EXP3, the IHU shall not send any
message to the EXP3 for a minimum of 100 milliseconds.
3.2

Experiment Operation Sequence

3.2.1 Upon Power On the IHU shall determine the state of the EXP3 by sending
an Is Camera Ready command message.
3.2.2 The IHU shall not send a Transmit Data Block command message prior toreceiving a Camera Ready reply message from the EXP3.

4 Message Content Requirements
4.1

Message Header Block4.1.1 The message header block shall be constructed as shown in table 2.
4.1.2 The message header block shall be sent with each Command, Reply, andData block.
Table 2

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

Message
Version2

Unsigned

0x01

0xFFFF

Message ICD
versionSoftware Build

2

Unsigned

0x01

0xFFFF

Software Buildversion

4.1.2.1 The Message Version shall be an integer representing the IHU to
EXP3 ICD document version number from which the message format
is derived, having the decimal point removed (e.g. version 1.03 would
be 103 decimal or 0x67).
Page 3 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

4.1.2.2 The Software Build shall be an integer representing the software build
version number of the system originating the message, having any
decimal points removed (e.g. version 1.03 would be 103 decimal or0x67).
4.2

Command Message Block4.2.1 The command message block shall be constructed as shown in Table 3.
Table 3Field

Size (Bytes)

Type

COMMAND

2Alpha

Min Value Max Value Description
RR
TT

RR
TT

Command4.2.2 The command message block shall contain one command in the
COMMAND field as shown in Table 4.
Table 4

Command

Description

RR

Is Camera Ready?

TT

Transmit Data Block

4.3

Reply Message Block4.3.1 The reply message block shall be constructed as shown in Table 5.
Table 5

Field

Size (Bytes)

Type

REPLY

2

Alpha

Min Value Max Value Description
NN
YY
FF

NN
YY
FF

Reply

4.3.2 The reply message block shall contain one reply in the REPLY field asshown in table 6.

Page 4 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD
Table 6

Command

Description

NN

Camera Not Ready or No
Earth Image Available

YY

Camera ReadyFF

Camera Failed

Page 5 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

4.4

Message Data Block4.4.1 The message data block shall be constructed as shown in Table 7.
Table 7

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

DESCRIPTOR

2

Unsigned--

Line ID and Payload
LengthPAYLOAD

Variable

Unsigned--

Array of (Payload
Length) bytes

CHKSUM

2

Unsigned--

16 bit accumulator sum
of bytes in HEADER
and PAYLOAD

4.4.2 The bits of the message data block DESCRIPTOR bytes shall be
constructed as shown in Table 8.
Table 8

Field

Size
(Bits)

Type

Min
Value

Max
Value

Description

Line ID

6

Unsigned

0x01

0x3C

640 x 8 pixel picture line
number (1 is top, 60 isbottom)PayloadLength10

Unsigned

0x01

0x3FF

Total number of bytes in
PAYLOAD

4.4.2.1 The Line ID shall compose the 6 MSB and the Payload Length shallcompose the 10 LSB.

5 Message Integrity
5.1

Invalid Messages

5.1.1 If the DATA block CHKSUM fails, the message shall be consideredinvalid.
5.1.2 If the Message Version does not match the message version in use forthe construction of messages on the receiving system, the message shallbe considered invalid.

Page 6 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD

6 Message Flow Diagrams
6.1

RR COMMAND

IHU

EXP4
COMMAND: RR

REPLY: NN, YY, OR FF

IHU Handling

End

Page 7 of 8

AMSAT Fox-1A
IHU to Experiment 4 ICD
6.2

TT COMMAND

IHU

EXP4
COMMAND: TT

MESSAGE DATA BLOCK OR REPLY:FF

IHU Handling

End

Page 8 of 8

AMSAT Fox-1A
Downlink Specification
Date: May 6, 2015
Version: Version 2.10

AMSAT Fox-1A
Downlink Specification
1 Introduction
This document specifies downlink frame formats for the Fox-1A telemetry andexperiment telemetry. This specification includes the both slow and high speed formats.
Document History
DATE

VERSION

SUMMARY

April 25, 2013

1.01

Remove TX PA Temperature and TX Osc
Temperature, add TX Temperature

May 21, 2013

1.2

High speed downlink details added

May 27, 2013

1.3

Remove Radiation Experiment Telemetry
Frame, resize Radiation Experiment Data
Frame, renumber Payload Types, added Slow
Speed Link Layer Transmission Scheduling,changed Reset Count to 16 bits

June 6, 2013

1.31

Reduce BATT CPU, PSU CPU, IHU CPU, TX
Temp, RX Osc Temp from 12 to 8 bit value, add
IHU Error Data field to Telemetry Minimum
Values Frame

June 26, 2013

1.32

Correct Payload Type numbers in Table 6

August 13, 2013

1.40

Changes due to new BATT telemetry values,
delete Type 4 from idle telemetry

August 26, 2013

1.41

Change Receiver Osc Temperature to Receiver
Card Temperature, remove TOTAL MPPT I,
update 2.2.9.1 and 2.2.9.1.1 to reflect variable
size of Radiation Experiment Data available

September 14, 2013

September 16, 2013

1.42

1.43

Added 3.1.2, Payload type 0 debug frame, madeScan Line Segment – Picture Count size 8 bits,
add RSSI to Payloads 1, 2, and 3, change typeformat to exclude code type, add Min/Max
ValuesAdded EXP4 temperature to Payloads 1, 2, and3, changed PSU CPU temp to PSU card temp

Page 1 of 20

AMSAT Fox-1A
Downlink Specification

DATE

VERSION

SUMMARY

October 15, 2013

1.44

Correct bit count for frame Type 3, change
calculated spin rate to remove PSU reference

November 18, 2013

1.45

Expanded all temperature fields to 12 bits, redo
3.1 payload order, add 2.2.7.3 and 2.2.7.4,
update SPIN to show bit pattern, add System I²C
Failure indications, add Ground Command TLM
reset count, add IHU Soft Error Data, add IHUHard Error Data, increase IHU Error Data to 32
bits, clarify which fields are raw values, added
2.2.7 5 padding slow speed frames, 2.2.8 forslow speed trailer info

January 13, 2014

1.50

Redo 3.2 beacon payloads

January 13, 2014

1.51

Change 3.2.1 to allow payload type 2 and 3 onlywith the voice ID

January 13, 2014

1.52

Correct 2.2.9 high speed link layer header
structure to show 16 bits on the Reset Count

January 14, 2014

1.53

Correct Table 4 and Table 5 Reset Count Max
Value to 0xFFFF to match use of 16 bits

February 10, 2014

1.54

Modify Table 11 to read “Experiment 1 Data” inthe description, added Safe Mode Indication bit
to payload 2 and 3, changed Filler bit size to 1 inpayload 2 and 3.

March 19, 2014

1.55

Move IHU Soft Error Data to Payload Type 3,
Move IHU Error Data to Payload Type 1 andrename to IHU Diagnostic Data, update Table 1
Bit Rate to 200 bps and Spectral Efficiency to 2
bps/Hz, remove Scrambler reference from Table
1 and Table 2.

March 24, 2014

1.56

Add timestamp elements to Payload 2 andPayload 3 for specific MAX or MIN last changed

April 23, 2014

1.57

Fix 4.4 BATT Board Temperature description toread Low instead of High

June 10, 2014

1.58

Remove Payload Type 2 MRAM Error Count,
Add PSU DC current, PSU DC high current,
PSU DC low current to Payload Type 1, 2, 3
respectively

September 30, 2014

2.00

Reorder fields in Payload Type 1, 2, 3, delete
filler fields, add filler bits to Table 5

Page 2 of 20

AMSAT Fox-1A
Downlink Specification
DATE

VERSION

SUMMARY

May 6, 2015

2.10

Revised Payload Type 5 and Picture Data
Structure to conform with actual implementation

Page 3 of 20

AMSAT Fox-1A
Downlink Specification
1.1 Document Scope
The purpose of this document is to specify the downlink protocol on the AMSAT Fox-1A
spacecraft.
1.2 References
1. Fox1 IHU to RF ICD
2. Fox1 IHU to Battery ICD
3. Fox1 IHU to PSU ICD
4. Fox1 IHU to Attitude Determination Experiment ICD
5. Fox1 IHU Software Architecture Specification
6. Fox1 IHU to Experiment 1 ICD
7. Fox1 IHU to Experiment 4 ICD
1.3 Definitions
1.3.1 Slow Speed Downlink – Data transmitted at approximately 100 bits per
second in the audio portion below 300 Hz simultaneous with thetransponder audio.
1.3.2 High Speed Downlink – Data transmitted at approximately 9600 bits per
second using the entire downlink audio passband.
1.3.3 Spacecraft Telemetry – Downlink data containing specific information
about spacecraft systems and health as defined in the System
Requirements and related documents.
1.3.4 Experiment Telemetry – Downlink data containing specific information
about the various experiment platforms flown on the satellite.
1.3.5 Frame – A defined set of data with a specific overall size comprised offields of a specific bit or byte length.

Page 4 of 20

AMSAT Fox-1A
Downlink Specification

2 Protocol Structure
2.1 Physical Layer
2.1.1 The physical layer includes options for slow-speed and high speed
operation.
2.1.2 Slow speed operation uses frequency-shift keying and is transmitted in
the sub-audible part of the audio downlink below 300 Hz. It may betransmitted simultaneously with voice or other audio signals. The detailsof the physical layer are shown in Table 1.
Table 1

Bit Rate
Spectral efficiency
Modulation type
Signal bandwidth
FSK Deviation
Spectral Mask
RF Channel Bandwidth

200 bps
2 bps/Hz
Non-coherent Frequency Shift Keying (FSK)
10 Hz to 200 Hz (-3 dB points)
500 Hz-20 dB at 300 Hz
1200 Hz

2.1.3 High speed operation uses frequency-shift keying and is transmittedusing the entire RF downlink bandwidth. The details of the physical layer
are shown in Table 2. Note that this is the same as the G3RUH modem.
Table 2

Bit Rate
Spectral efficiency
Modulation type
Signal bandwidth
FSK Deviation
Spectral Mask
RF Channel Bandwidth

9600 bps
2 bps/Hz
non-coherent frequency shift keying (FSK)
10 Hz to 4800 Hz (-3 dB points)
3 kHz-60 dB at 7500 Hz
20 kHz

2.2 Link Layer
2.2.1 The link layer protocol provides multiplexing, packet identification andforward error correction.
2.2.2 The link layer shall include a header and a trailer surrounding theapplications layer payload to form data packets as shown in Table 3.
Table 3Header

Applications Payload

Page 5 of 20

TrailerAMSAT Fox-1A
Downlink Specification
2.2.3 The applications payload layer shall include satellite telemetry,experiment telemetry, high speed data, and debug frames.
2.2.4 Debug frames may be used during ground testing but shall not betransmitted for flight.
2.2.5 Bits shall be transmitted in the order of most significant bit first.
2.2.6 Bytes shall be transmitted in Little Endian order.
2.2.7 The Slow Speed link layer header structure shall be as shown in Table 4.
Table 4

Field

Size
(Bits)

Type

Min
Value

Max Value

Fox ID

3

Unsigned

0x01

0x01

Reset
Count

16

Unsigned

0x00

0xFFFF

Uptime25

Unsigned

0x00

0x1FFFFFF

Type

4

Unsigned

0x00

0x0F

Description
0x01 specifies Fox-1A (eachFox satellite will have aunique ID)
Total number of times IHU
has reset since initial on-orbit
startupThis is the IHU uptime inseconds since the last reset
This identifies the payload
type

2.2.7.1 Payload type shall be as specified in the application layer payload
data.
2.2.7.2 Each Slow Speed link layer structure shall contain only one payload
type.
2.2.7.3 Reset Count and Uptime shall reflect the time at which the payload
data was collected.
2.2.7.4 Reset Count and Uptime shall not be changed if the payload data has
not been updated.
2.2.7.5 Real-Time Telemetry Frame, Telemetry Maximum Values Frame, andTelemetry Minimum Values Frame data shall be padded with zeros toequal 58 bytes length for each.
2.2.8 Forward error correction (FEC) code words shall be sent in the link layer
trailer. The FEC shall be a Reed Solomon RS 255,223 code. (Thisprovides 32 parity bytes per code word allowing error detection andcorrection capability.)
2.2.9 The High Speed link layer header structure is shown in Table 5.

Page 6 of 20

AMSAT Fox-1A
Downlink Specification
Table 5

Field

Size
(Bits)

Type

Min
Value

Max Value

Fox ID

3

Unsigned

0x01

0x01

Reset
Count

16

Unsigned

0x00

0xFFFF

Uptime25

Unsigned

0x00

0x1FFFFFF(No
Value)

4

Unsigned

0x00

0x00

Description
0x01 specifies Fox-1A (eachFox satellite will have aunique ID)
Total number of times IHU
has reset since initial on-orbit
startupThis is the IHU uptime inseconds since the last reset
4 bit filler

2.2.10 The High Speed link layer applications payload shall contain data fromall payload types, as shown in table 6.
Table 6

Payload Type

Size (Bytes)

Description

160Real-Time Telemetry Frame

2

60

Telemetry Maximum Values Frame

3

60

Telemetry Minimum Values Frame

5

Variable1 - 4300

Camera JPEG Data Frame

4

58

Radiation Experiment High Speed Data Frame

2.2.10.1 A varying number of Radiation Experiment Data bytes shall be sent
to fill the applications payload size to a total of 4600 bytes if the
payload type 5 data is less than 4300 bytes.
2.2.10.1.1 When less than a sufficient number of bytes to contain a usefuldata frame remain to fill to 4600 bytes, the remaining bytes shallbe filled with zeros.
2.2.10.2 Real-Time Telemetry Frame, Telemetry Maximum Values Frame,
and Telemetry Minimum Values Frame data shall be padded withzeros to equal 60 bytes length for each.
2.2.11 Forward error correction (FEC) code words shall be sent in the link
layer trailer. The FEC shall be a Reed Solomon RS 255,223 code. (Thisprovides 32 parity bytes per code word allowing error detection andcorrection capability.) Twenty one code words will be populated inparallel, with 1 byte being added to each code word in sequence until all
Page 7 of 20

AMSAT Fox-1A
Downlink Specification
bytes have been processed. The last code word will be partially filled
and should be virtually padded with 77 bytes. The data will then be sent
sequentially with 8b10b coding. Twenty one sets of 32 parity bytes will
follow after all data has been sent for the high speed frame.

3 Slow Speed Link Layer Transmission Scheduling
3.1 While IHU PTT is asserted Payload Types contained in the Link Layer
Applications Payload shall rotate, changing type with each successive
link layer transmitted, in the following order:
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x

Type 1
Type 4
Type 4
Type 1
Type 4
Type 4
Type 1
Type 4
Type 4
Type 1
Type 2Type 4
Type 1
Type 4
Type 4
Type 1
Type 4
Type 4
Type 1
Type 4
Type 4
Type 1
Type 3
Type 43.1.1 The above order shall be repeated so long as IHU PTT is asserted.
3.1.2 Each time IHU PTT is asserted the order shall begin at the top.
3.1.3 The IHU PTT shall not be de-asserted during transmission of a Link
Layer.

Page 8 of 20

AMSAT Fox-1A
Downlink Specification
3.2 While beacon message is sent during idle timer expired the Payload
Types contained in the Link Layer Applications Payload shall betransmitted in alternating sets, one set per beacon message:
Set 1:x Type 1
x Type 2
Set 2:x Type 1
x Type 3
3.2.1 The payload type 2 or 3 data shall be sent simultaneously with the voiceID.

Page 9 of 20

AMSAT Fox-1A
Downlink Specification

4 Application Layer Payload Data
4.1 Payload Type 0 – Debug Frame (NOT TO BE TRANSMITTED FOR
FLIGHT)
Table 7

Field

Size
(Bits)

Type

Min
Value

Max
Value

Description

UNDEFINED

1 - 464

Undefined--

Debug data for groundtesting

Page 10 of 20

AMSAT Fox-1A
Downlink Specification
4.2 Payload Type 1 - Real-Time Telemetry Frame (Size = 429 bits)
Table 8

Field

Size
(Bits)

Type

Min
Value

Max
Value

BATT A V

12

Unsigned

0x00

0xFFF

BATT B V

12

Unsigned

0x00

0xFFF

BATT C V

12

Unsigned

0x00

0xFFF

BATT A T

12

Unsigned

0x00

0xFFF

BATT B T

12

Unsigned

0x00

0xFFF

BATT C T

12

Unsigned

0x00

0xFFF

12

Signed

0x00

0xFFF

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

-X PANEL V

12

Unsigned

0x00

0xFFF

+Y PANELV

12

Unsigned

0x00

0xFFF

-Y PANEL V

12

Unsigned

0x00

0xFFF

+Z PANEL V

12

Unsigned

0x00

0xFFF

-Z PANEL V

12

Unsigned

0x00

0xFFF

+X PANEL T

12

Unsigned

0x00

0xFFF

-X PANEL T

12

Unsigned

0x00

0xFFF

+Y PANEL T

12

Unsigned

0x00

0xFFF

-Y PANEL T

12

Unsigned

0x00

0xFFF

+Z PANEL T

12

Unsigned

0x00

0xFFF

TOTAL
BATT IBATT Board
Temperature+X PANEL
V

Page 11 of 20

Description
Battery pair A voltage raw
value (0-2.5V scale)Battery pairs A+B voltage
raw value (0-3.3V scale)Battery pairs A+B+C
voltage raw value (0-5.0V
scale)
This value also represents
the power bus voltage(VBATT)
Battery pair A temperature
raw value
Battery pair B temperature
raw value
Battery pair C temperature
raw value
Total Battery DC current
raw value
PC Board Temperature of
BATT raw value+X solar panel voltage raw
value-X solar panel voltage raw
value+Y solar panel voltage raw
value-Y solar panel voltage raw
value+Z solar panel voltage raw
value-Z solar panel voltage raw
value+X solar panel temperature
raw value-X solar panel temperature
raw value+Y solar panel temperature
raw value-Y solar panel temperature
raw value+Z solar panel temperature
raw value

Bit
Offset
0
12

24

36
48
60
72
84
96
108
120
132
144
156
168
180
192
204
216

AMSAT Fox-1A
Downlink Specification
Bit
OffsetField

Size(Bits)

Type

Min
Value

Max
Value

-Z PANEL T

12

Unsigned

0x00

0xFFF

PSU
Temperature

12

Unsigned

0x00

0xFFF

SPIN

12

Signed

0x00

0xFFF

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

Raw Angle

324

12

Unsigned

0x00

0xFFF

Raw Angle

336

12

Unsigned

0x00

0xFFF

Raw Angle

348

12

Unsigned

0x00

0xFFF

Experiment 4 card
temperature raw value

360

PSU Current

12

Unsigned

0x00

0xFFF

PSU DC current

372

IHU
Diagnostic
Data

32

Unsigned--

Diagnostic Data on IHU
Performance

384

0x01
0x09

Bit 0 is Experiment 1
Bit 1 is Experiment 2 (N/A
on Fox-1A)
Bit 2 is Experiment 3 (N/A
on Fox-1A)
Bit 3 is Experiment 4
State: 0 = Working, 1 =Failed416

TX PA
Current
TX
Temperature
RX
Temperature
RSSI
IHU CPU
Temperature
Satellite X
Axis Angular
Velocity
Satellite Y
Axis Angular
Velocity
Satellite Z
Axis Angular
Velocity
EXP 4
Temperature

Experiment
FailureIndication

4

Unsigned

0x00
0x08

Page 12 of 20

Description-Z solar panel temperature
raw value
PSU card temperature raw
value
Calculated spin rate RPM
using solar cells
Bit 11 = sign
Bits 10 to 8 = integer
Bits 7 to 0 = fraction
Transmit power amplifier
current raw value
Transmitter card
temperature raw value
Receiver card temperature
raw value
Received Signal Strength
Indication raw value
CPU Temperature of IHU
raw value

228
240

252

264
276
288
300
312

AMSAT Fox-1A
Downlink Specification

Field
System I2C
FailureIndications
Number of
GroundCommanded
TLM Resets
Antenna
DeploySensors

Size(Bits)

Type

Min
Value

Max
Value

Description

Bit
Offset420

3

Unsigned

0x00

0x07

Bit 0 is BATT
Bit 1 is PSU Device 1
Bit 2 is PSU Device 2
State: 0 = Working, 1 =Failed4

Unsigned

0x00

0x0F

Number of times command
stations reset stored
telemetry423

2

Unsigned

0x00

0x03

Bit 0 is RCV Bit 1 is XMTState: 0 = stowed 1 =deployed

427

Page 13 of 20

AMSAT Fox-1A
Downlink Specification
4.3 Payload Type 2 - Telemetry Maximum Values Frame (Size = 460 bits)
Table 9

Field

Size
(Bits)

Type

Min
Value

Max Value

BATT A V

12

Unsigned

0x00

0xFFF

BATT B V

12

Unsigned

0x00

0xFFF

BATT C V

12

Unsigned

0x00

0xFFF

BATT A T

12

Unsigned

0x00

0xFFF

BATT B T

12

Unsigned

0x00

0xFFF

BATT C T

12

Unsigned

0x00

0xFFF

TOTAL
BATT I

12

Signed

0x00

0xFFF

BATT Board
Temperature

12

Unsigned

0x00

0xFFF

+X PANEL V

12

Unsigned

0x00

0xFFF

-X PANEL V

12

Unsigned

0x00

0xFFF

+Y PANEL V

12

Unsigned

0x00

0xFFF

-Y PANEL V

12

Unsigned

0x00

0xFFF

+Z PANEL V

12

Unsigned

0x00

0xFFF

-Z PANEL V

12

Unsigned

0x00

0xFFF

+X PANEL T

12

Unsigned

0x00

0xFFF

Page 14 of 20

Description
Battery pair A highvoltage raw value (02.5V scale)Battery pairs A+B
high voltage raw
value (0-3.3V scale)Battery pairs A+B+C
high voltage raw
value (0-5.0V scale)This value also
represents the powerbus voltage (VBATT)
Battery pair A hightemperature raw
value
Battery pair B hightemperature raw
value
Battery pair C hightemperature raw
value
Battery DC highcurrent raw value
High PC Board
Temperature of
BATT raw value+X solar panel highvoltage raw value-X solar panel highvoltage raw value+Y solar panel highvoltage raw value-Y solar panel highvoltage raw value+Z solar panel highvoltage raw value-Z solar panel highvoltage raw value+X solar panel hightemperature raw
value

Bit
Offset
0

12

24

36

48

60
72
84
96
108
120
132
144
156
168

AMSAT Fox-1A
Downlink Specification
Bit
OffsetField

Size(Bits)

Type

Min
Value

Max Value-X PANEL T

12

Unsigned

0x00

0xFFF

+Y PANEL T

12

Unsigned

0x00

0xFFF

-Y PANEL T

12

Unsigned

0x00

0xFFF

+Z PANEL T

12

Unsigned

0x00

0xFFF

-Z PANEL T

12

Unsigned

0x00

0xFFF

PSU
Temperature

12

Unsigned

0x00

0xFFF

SPIN

12

Signed

0x00

0xFFF

TX PA
Current

12

Unsigned

0x00

0xFFF

TX
Temperature

12

Unsigned

0x00

0xFFF

RX
Temperature

12

Unsigned

0x00

0xFFF

RSSI

12

Unsigned

0x00

0xFFF

IHU CPU
Temperature

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

Highest Raw Angle

324

12

Unsigned

0x00

0xFFF

Highest Raw Angle

336

12

Unsigned

0x00

0xFFF

Highest Raw Angle

348

Satellite X
Axis Angular
Velocity
Satellite Y
Axis Angular
Velocity
Satellite Z
Axis Angular
Velocity

Page 15 of 20

Description-X solar panel hightemperature raw
value+Y solar panel hightemperature raw
value-Y solar panel hightemperature raw
value+Z solar panel hightemperature raw
value-Z solar panel hightemperature raw
value
PSU card hightemperature raw
value
Highest calculated
spin rate RPM using
solar cells
Transmit power
amplifier high current
raw value
Transmitter card hightemperature raw
value
Receiver card hightemperature raw
valueHigh Received Signal
Strength Indication
raw valueHigh CPU
Temperature of IHU
raw value

180

192

204

216

228

240

252

264

276

288

300

312

AMSAT Fox-1A
Downlink Specification

Description

Bit
Offset0xFFF

Experiment 4 cardhigh temperature raw
value

360

0x00

0xFFF

PSU DC high current

372

Unsigned--

16

Unsigned

0x00

0xFFFF

25

Unsigned

0x00

0x1FFFFFF

1

Unsigned

0x00

0x01

1

Unsigned

0x00

0x01

1

Unsigned

0x00

0x01

Field

Size
(Bits)

Type

Min
Value

Max Value

EXP 4
Temperature

12

Unsigned

0x00

PSU Current

12

Unsigned

IHU Hard
Error Data

32

MAX
Timestamp
Reset CountMAX
Timestamp
UptimeSafe Mode
Indication
Auto-Safe
Mode
Indication
Auto-Safe
EnabledPage 16 of 20

Diagnostic Data on
IHU Hard Errors
At last MAX, total
number of times IHU
has reset since initial
on-orbit startup
At last MAX, the IHU
uptime in seconds
since the last reset
State: 1 = Safe Mode
ActiveState: 1 = Safe Mode
activated by AutoSafe
State: 1 = Auto-Safe
Mode enabled

384

416

432
457
458
459

AMSAT Fox-1A
Downlink Specification
4.4 Payload Type 3 - Telemetry Minimum Values Frame (Size = 460 bits)
Table 10

Field

Size
(Bits)

Type

Min
Value

Max Value

BATT A V

12

Unsigned

0x00

0xFFF

BATT B V

12

Unsigned

0x00

0xFFF

BATT C V

12

Unsigned

0x00

0xFFF

BATT A T

12

Unsigned

0x00

0xFFF

BATT B T

12

Unsigned

0x00

0xFFF

BATT C T

12

Unsigned

0x00

0xFFF

TOTAL BATTI

12Signed

0x00

0xFFF

BATT Board
Temperature

12

Unsigned

0x00

0xFFF

+X PANEL V

12

Unsigned

0x00

0xFFF

-X PANEL V

12

Unsigned

0x00

0xFFF

+Y PANEL V

12

Unsigned

0x00

0xFFF

-Y PANEL V

12

Unsigned

0x00

0xFFF

+Z PANEL V

12

Unsigned

0x00

0xFFF

-Z PANEL V

12

Unsigned

0x00

0xFFF

+X PANEL T

12

Unsigned

0x00

0xFFF

Page 17 of 20

Description
Battery pair A low
voltage raw value (02.5V scale)Battery pair A+B low
voltage raw value (03.3V scale)Battery pair A+B+C
low voltage raw value(0-5.0V scale)This value also
represents the powerbus voltage (VBATT)
Battery pair A low
temperature raw
value
Battery pair B low
temperature raw
value
Battery pair C low
temperature raw
value
Battery DC low
current raw value
Low PC Board
Temperature of
BATT raw value+X solar panel low
voltage raw value-X solar panel low
voltage raw value+Y solar panel low
voltage raw value-Y solar panel low
voltage raw value+Z solar panel low
voltage raw value-Z solar panel low
voltage raw value+X solar panel lowtemperature raw
value

Bit
Offset
0

12

24

36

48

60
72
84
96
108
120
132
144
156
168

AMSAT Fox-1A
Downlink Specification
Bit
OffsetField

Size(Bits)

Type

Min
Value

Max Value-X PANEL T

12

Unsigned

0x00

0xFFF

+Y PANEL T

12

Unsigned

0x00

0xFFF

-Y PANEL T

12

Unsigned

0x00

0xFFF

+Z PANEL T

12

Unsigned

0x00

0xFFF

-Z PANEL T

12

Unsigned

0x00

0xFFF

PSU
Temperature

12

Unsigned

0x00

0xFFF

SPIN

12

Signed

0x00

0xFFF

TX PA
Current

12

Unsigned

0x00

0xFFF

TX
Temperature

12

Unsigned

0x00

0xFFF

RX
Temperature

12

Unsigned

0x00

0xFFF

RSSI

12

Unsigned

0x00

0xFFF

IHU CPU
Temperature

12

Unsigned

0x00

0xFFF

12

Unsigned

0x00

0xFFF

Lowest Raw Angle

324

12

Unsigned

0x00

0xFFF

Lowest Raw Angle

336

12

Unsigned

0x00

0xFFF

Lowest Raw Angle

348

Satellite X
Axis Angular
Velocity
Satellite Y
Axis Angular
Velocity
Satellite Z
Axis Angular
Velocity

Page 18 of 20

Description-X solar panel lowtemperature raw
value+Y solar panel lowtemperature raw
value-Y solar panel lowtemperature raw
value+Z solar panel lowtemperature raw
value-Z solar panel lowtemperature raw
value
PSU card low
temperature raw
value
Lowest calculated
spin rate RPM using
solar cells
Transmit power
amplifier low current
raw value
Transmitter card low
temperature raw
value
Receiver card low
temperature raw
value
Low Received Signal
Strength Indication
raw value
Low CPU
Temperature of IHU
raw value

180

192

204

216

228

240

252

264

276

288

300

312

AMSAT Fox-1A
Downlink Specification

Field

Size
(Bits)

Type

Min
Value

Max Value

Description

Bit
Offset

EXP 4
Temperature

12

Unsigned

0x00

0xFFF

Experiment 4 card
low temperature raw
value

360

PSU Current

12

Unsigned

0x00

0xFFF

PSU DC low current

372

IHU Soft
Error Data

32

Unsigned--

MIN
Timestamp
Reset Count

16

Unsigned

0x00

0xFFFF

25

Unsigned

0x00

0x1FFFFFF

1

Unsigned

0x00

0x01

1

Unsigned

0x00

0x01

1

Unsigned

0x00

0x01

MIN
Timestamp
UptimeSafe Mode
Indication
Auto-Safe
Mode
Indication
Auto-Safe
EnabledPage 19 of 20

Diagnostic Data on
IHU Soft Errors
At last MIN, total
number of times IHU
has reset since initial
on-orbit startup
At last MIN, the IHU
uptime in seconds
since the last reset
State: 1 = Safe Mode
ActiveState: 1 = Safe Mode
activated by AutoSafe
State: 1 = Auto-Safe
Mode enabled

384

416

432
457
458
459

AMSAT Fox-1A
Downlink Specification
4.5 Payload Type 4 - Radiation Experiment Data Frame (Size = 464 bits)
Table 11

Field Size (Bytes)
Data

Type

58

Min Value Max Value

Unsigned--

Description
Experiment 1 Data

4.6 Payload Type 5 - Camera JPEG Data Frame (Size is variable)
Table 12

Field

Size
(Bits)

Type

Min
Value

Max
Value

Description

Scan LineCount

8

Unsigned

0x00

0xFF

Count of scan lines in
payloadPicture Data

Variable

Unsigned----

Picture Data Structure(Section 5)

Type

Min
Value

Max
Value

Description

5 Picture Data Structure
5.1 Scan Line Segment
Table 13

Field

Size
(Bits)

PictureCounter8

Unsigned

0x00

0xFF

Picture count indicator

Scan Line
Number6

Unsigned

0x00

0x3B

0x00 = top scan line

Scan Line
Length10

Unsigned

0x001

0x3FF

Count of bytes in thescan line

Scan Line
Data

Variable

Unsigned--(Fragment Length) ScanLine Data

5.1.1 Total Scan Line Segment data size for one Applications Payload frame
shall not exceed 4299 bytes.

Page 20 of 20

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD
Date: February 21, 2015
Version: Version 1.04

AMSAT Fox-1D
IHU to Experiment 1 Interface Control Document
1 Introduction
This document specifies the message interface between the InternalHousekeeping Unit (IHU) and the University of Iowa Experiment System, EXP 1of the satellite, known as the High-Energy Radiation CubeSat Instrument andabbreviated as HERCI.

Page 1 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD
1.1

Document History
DATE

VERSION

SUMMARY

November 13, 2014

0.5

Draft version

November 14, 2014

0.6

Draft update

November 30, 2014

0.6

Draft update #2

December 2, 2014

0.7

Changed source template to reflect SPI,
replaced EXP4 with EXP1

December 2, 2014

0.7

Changed CAMERA to DETECTOR (provisional)
throughout and added “No Detector Data

Available” reply in Table 6
December 15, 2014

0.8

Incorporated changes from U of I, renamed EXP
to HERCI, etc..

January 1, 2015

0.81

Changed Experiment Enable 4 to Experiment
Enable 1

January 9, 2015

0.9

Added CLOCK field to Table 3, added STATUS
field to Table 5, CUT LINE ID from Table 7, 8

January 14, 2015

0.91

Added HOUSEKEEPING to op sequence, HK,
EE (provisional) to command message blockand flow diagrams.

January 19, 2015

0.92

Cut 4.4.2 – LINE ID + Length descriptor bits

January 22, 2015

0.95

Changed Reply to Failure

February 10, 2015

0.97

Swapped CLOCK field in favor of separate time
fields, temp add “PP” command

February 13, 2015

0.98

Cleaned up formatting, added ZZ command,
diagram, expanded on STATUS codes

February 13, 2015

0.99

Added RR command text & flows, added DD
message block, Power On sequence flows,
added draft power cycle criteria.

February 16, 2015

1.00

Revised message header, added Safe Mode
exception to Power Off sequence, added ICD
version code (later removed).

February 17, 2015

1.01

Added subrequirements for compound cases.

February 17, 2015

1.02

Deleted text from Power On diagram.

February 19, 2015

1.03

Deleted DD and EE commands,
STATUS code. Cleaned up formatting.

February 21, 2015

1.04

Changed bus voltage to 3.3 (based on email
thread), reordered message header information
for clarity, reformatted, renumbered.

Page 2 of 15

deletedAMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD

1.2 Document Scope
This document will specify the control of HERCI, the messaging format, and theserial bus hardware operation for the communications between the IHU andHERCI.
References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification

Page 3 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall initiate a command to HERCI.
2.1.2 HERCI shall send a reply to each IHU request.
2.1.3 Message bit order shall be least significant bit first.
2.1.4 The IHU shall determine the action to be taken in the event of an invalid,
improper, or missing message from the HERCI.
2.1.5 HERCI shall take no action in the event of an invalid or improper message
from the IHU.
2.1.6 Message byte order shall be Little Endian.
2.2

General Message Requirements

2.2.1 Each message shall contain a header block.
2.2.2 Each message shall contain one command, one reply, or one data block.
2.3

Serial Bus Hardware Interface Requirements

2.3.1 The bus levels shall be 3.3V.
2.3.2 The bus data speed shall be 38400 bit/s.
2.3.3 The serial bus communication shall be asynchronous.
2.3.4 The number of data bits shall be 8.
2.3.5 The number of stop bits shall be 1.
2.3.6 There shall be no parity bit.

Page 4 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD

3 Experiment Operation
3.1

Experiment Power Control

3.1.1 The IHU shall exert control over the power state of HERCI by theExperiment Enable 1 pin on the satellite bus as shown in Table 1.
Table 1Pin State

Description
High
Power On Experiment
Low or high-impedance Power Off Experiment

Page 5 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD
3.1.2 Upon signaling Power On to HERCI, the IHU shall not power down
HERCI for a minimum of 90 seconds
3.1.2.1 If the satellite is commanded into Safe Mode during the 90
second interval, the IHU shall not wait for the remainder ofthe interval before signaling Power Off.
3.1.3 Upon signaling Power On to HERCI, IHU will wait up to 45 seconds for an
unsolicited FF reply message block, indicating HERCI has failed self-test.
After waiting the 45 seconds, IHU will send HH housekeeping request
messages every 10 seconds for an additional 50 seconds. If HERCI does
not respond to one of those HH request messages with a housekeeping
data reply message, HERCI shall be considered failed and the IHU shallperform the following Power Cycle Sequence:
3.1.3.1 The IHU shall signal Power Off to HERCI.
3.1.3.2 The IHU shall wait 30 seconds.
3.1.3.3 The IHU shall signal Power On to HERCI.
3.1.3.4 The IHU shall perform this Power Cycle (3.1.3.1 to 3.1.3.3)
up to three total cycles.
3.1.3.5 This state shall be reset when the IHU is reset (power cycle)
and HERCI will be powered up again using the cycle in
3.1.3.1 to 3.1.3.4.
3.1.4 If at any time after 90 seconds following Power On HERCI exhibits any of
the following behaviors, the IHU shall perform a Power Cycle Sequence.
3.1.4.1 Failure to respond to three consecutive Data Blockcommands.
3.1.4.2 DETECTOR Not Ready (NN)consecutive Data Block commands.

responses

to

three

3.1.4.3 DETECTOR Failed (FF) responses to three consecutive
Data Block commands.
3.1.5 When entering Safe Mode, the IHU shall perform the following actions:3.1.5.1 The IHU shall send a Safe Mode Notification command to
HERCI.
3.1.5.2 The IHU shall wait 5 seconds.
3.1.5.3 The IHU will signal Power Off to HERCI.
3.2

Experiment Operation Sequence

3.2.1 The IHU shall request housekeeping telemetry by sending a Transmit
HOUSEKEEPING Data Block command message at least once every 30
seconds while in transponder mode, but no more than once every 10
seconds.
3.2.2 The IHU shall send updated time in the CLOCK fields of each commandmessage.
Page 6 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD

4 Message Content Requirements
4.1

Message Header Block4.1.1 The message header block shall be constructed as shown in table 2.
4.1.2 The message header block shall precede each command message.
Table 2

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

Message
Version2

Unsigned

0x01

0xFFFF

Message ICD
versionSoftware Build

2

Unsigned

0x01

0xFFFF

Software Buildversion

4.1.2.1 The Message Version shall be an integer representing the
IHU to HERCI ICD document version number from which themessage format is derived, having the decimal point
removed (e.g. version 1.03 would be 103 decimal or 0x67.
4.1.2.2 The Software Build shall be an integer representing thesoftware build version number of the system originating themessage, having any decimal points removed (e.g. version
1.03 would be 103 decimal or 0x67).

Page 7 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD
4.2

Reply Message Block4.2.1 The Reply Message block shall be constructed as shown in Table 3.

4.2.2 The Reply Message Block shall precede each command message.
Table 3

Field

Size
(Bytes)

Type

Min
Value

Max
Value

Description

MESSAGEVERSION

2

Unsigned

0x01

0xFFFF

Message ICD version

SOFTWARE
BUILD

2

Unsigned

0x01

0xFFFF

Software Build version

Alpha

YY
NN
FF
UU

YY
NN
FF
UU

REPLY CODE

0xFFFF

Number of bytes
following this reply
message block

REPLY
CODE
PAYLOADSIZE

2

2

Unsigned

0x00

4.2.2.1 The Message Version shall be an integer representing the
IHU to HERCI ICD document version number from which themessage format is derived, having the decimal point
removed (e.g. version 1.03 would be 103 decimal or 0x67).
4.2.2.2 The Software Build shall be an integer representing thesoftware build version number of the system originating themessage, having any decimal points removed (e.g. version
1.03 would be 103 decimal or 0x67).
4.2.2.3 The Reply Message block shall contain one REPLY CODEin the REPLY CODE field as shown in table 4.
Table 4

Reply CodeDescription

NN

DETECTOR Not Ready or No Detector Data Available

FF

DETECTOR Failed

YY

EE, ZZ Command message acknowledged

UU

Message from IHU unexpected or otherwise malformed

Page 8 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD
4.3

Command Message Block4.3.1 The command message block shall be constructed as shown in Table 5.
Table 5

Field

COMMAND

Size(Bytes)
2

Type

Alpha

Min
Value
HH
PP
RR
ZZ

RESET
COUNT

2

Unsigned

0x00

UPTIMEWHOLE
SECONDS

4

Unsigned

0x00002

Unsigned

0x00002

Unsigned

0x0000UPTIMEFRACTIONALSECONDSCHECKSUM

Max Value

Description

HH
PP
RR
ZZ

Command

Total number oftimes IHU has reset
0xFFFF
since initial on-orbit
startup
Uptime in seconds
0xFFFFFFFF since the last IHU
reset
This is the fractional
seconds since thelast
IHU
reset.
(Note: this value
0xFFFF
may be slightly
delayed based on
its position in thetask queue)
0xFFFF

16
bit
rolloveraccumulator

4.3.2 The command message block shall contain one command in the
COMMAND field as shown in Table 6.
Table 6

Command

Description

HH

Transmit HOUSEKEEPING Data Block

PP

Transmit PACKET (of DETECTOR) Data BlockRR

RESEND previous PACKET Data Block

ZZ

Safe Mode Notification

Page 9 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD
4.4

Message Data Block4.4.1 The message data block for HOUSEKEEPING and PACKET Data Blocks
shall be constructed as shown in Table 7.
Table 7

Field

Size (Bytes)

Type

Min Value

Max
Value

Description

DD
HH

Data
or
Housekeeping
Data Block-

Payload0xFFFF

16 bit rollover
accumulator
sum of bytes in
HEADER andPAYLOAD

TYPE

2

Alpha

DD
HH

PAYLOAD

Variable - maxof 58 bytes forHousekeeping,
868 bytes for
Detector Data

Unsigned-

CHKSUM

2

Unsigned

0x00

5 Message Integrity
5.1

Invalid Messages

5.1.1 If the DATA block CHKSUM fails in a response to a Transmit
HOUSEKEEPING Data Block command, the message shall beconsidered invalid.
5.1.2 If the Message Version does not match the message version in use forthe construction of messages on the receiving system, the message shallbe considered invalid.
5.1.3 The IHU shall consider a UU response an “invalid” message.
5.1.4 In the event of 3 consecutive invalid messages, the IHU shall power cycle
HERCI as described in 3.1.3.1 to 3.1.3.4
5.1.5 If the DATA block CHKSUM fails in a response to a Transmit Packet Data
Block command, the IHU shall send a Resend Packet command. After 3
consecutive failed responses to a PP or RR command, the IHU shallpower cycle HERCI as described in 3.1.3.1 – 3.1.3.4

Page 10 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD

6 Message Flow Diagrams
6.1 HH COMMANDHERCI responds to the HH command by returning a housekeeping record
embedded in the response. HH command may occur at any time.

IHU

HERCI
COMMAND: HH, (CLOCK FIELDS)MESSAGE DATA BLOCK OR FAIL:FF, NN

IHU Handling

End

Page 11 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD

6.2 PP COMMANDHERCI responds to the PP command by returning a telemetry transport frame
embedded in the response.

IHU

HERCI
COMMAND: PP, (CLOCK FIELDS)MESSAGE DATA BLOCK or FAIL: FF, NN

IHU Handling

End

Page 12 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD

6.3

RR COMMANDHERCI responds to the RR command by returning the last telemetry transport
frame sent to IHU embeddedin the response. The RR command will only occur
immediately following a PP command.

IHU

HERCI
COMMAND: RR, (CLOCK FIELDS)MESSAGE DATA BLOCK or FAIL: FF, NN

IHU Handling

End

Page 13 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD

6.4 ZZ COMMANDHERCI responds to the ZZ command by stopping data collection and closing its
data file system.The ZZ command may occur at any time.

IHU

HERCI
COMMAND: ZZ, (CLOCK FIELDS)PREP FOR IHU SAFEMODE
REPLY MESSAGEIHU Handling

End

Page 14 of 15

AMSAT Fox-1D
IHU to Experiment 1 (HERCI) ICD

7 Power On Diagram
Power On Sequence

IHU

HERCI
SIGNAL POWER ON

45 seconds
HH COMMAND MESSAGE EVERY 1O - 30 SECONDS

50 seconds

7.1

If no response
after 50 seconds

Possible Boot Failure Message

MESSAGE DATA BLOCK OR FAIL:FF, NN

SIGNAL POWER OFF

Page 15 of 15

Boot Up
30 – 60
seconds

AMSAT Fox-1
IHU to PSU ICD
Date: March 2, 2015
Version: Version 2.11

AMSAT Fox-1
IHU to MPPT PSU Interface Control Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the MPPT Power Supply (PSU) System, as required per the AMSAT Fox-1
System Requirements Specification document.
1.1

Document History
DATE

VERSION

SUMMARY

February 21, 2012

1.0

Initial version

February 21, 20121.01

Clarify I²C address

March 7, 2012

1.02

2.3.1 updated Vdd to 3.0V

August 7, 2012

1.03

Remove BATT1 data fields and adjust message
accordingly

November 7, 2012

1.04

Added PSU CPU Temperature

December 27, 2012

1.10

Change from Bytes to Bits in Message Header
Block, Message Data Block, Message Data (toallow for 12 bit ADC values)

January 2, 2013

1.11

Field sizes back to bytes account I²C
specifications

February 7, 2013

1.12

Correct typo in 3.3.1.1

August 22, 2013

1.13

Remove TOTAL I from Data block

August 22, 2013

1.14

Update I²C speed to 10 kHz

October 4, 2013

2.00

Rework to eliminate STM32L and replace with
ADS7828s

November 18, 2013

2.01

Change telemetry sample rate in 2.2.1 to 4
seconds

June 10, 2014

2.1

Update Table 1 and Table 2 to reflect actual
construction, add PSU Output Current to Table
1, swap addresses for Device 1 and Device 2 toaccount for construction error

March 2, 2015

2.11

Updated ADC Channel tables

Page 1 of 4

AMSAT Fox-1
IHU to PSU ICD
1.2 Document Scope
The purpose of this document is to specify the message format and the I²C bus hardware
operation for the communications between the IHU and the MPPT PSU as described in
the AMSAT Fox-1 System Requirements Specification.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification

2 General Messaging Requirements
2.1

Link Protocol Requirements

2.1.1 The IHU shall be the I²C Master.
2.1.2 The MPPT PSU shall be the I²C Slave.
2.1.2.1 The IHU shall request the MPPT PSU to send the data for a specific
Device and channel.
2.1.2.2 The MPPT PSU shall send that specific Device and channel data.
2.1.3 The IHU shall test for the presence both MPPT PSU system Devices.
2.1.4 The IHU shall only poll the MPPT PSU system Device(s) present, for data.
2.2

General Message Requirements

2.2.1 The IHU shall sample data at a rate sufficient to provide downlink telemetry
data every 4 seconds.
2.2.2 For both Devices the ADS 7820 A/D converter shall always be commandedon (PD-0 bit = 1).
2.2.3 For both Devices the ADS 7820 Internal Reference shall always becommanded on (PD-1 bit = 1).
2.2.4 TFor both Devices the ADS 7820 shall always be commanded for singleended inputs.
2.3

I²C Bus Hardware Interface Requirements

2.3.1 The I²C Vdd shall be 3.0V.
2.3.2 The bus speed shall be Standard (10 kHz).
2.3.3 The MPPT PSU system Device 1 I²C 7 bit address shall be 0x4A.
2.3.4 The MPPT PSU system Device 2 I²C 7 bit address shall be 0x49.

Page 2 of 4

AMSAT Fox-1
IHU to PSU ICD

3 Message Content Requirements
3.1

Measured Values

3.1.1 The measured data fields for Device 1 and their associated ADS 7828
channels shall be as shown in Table 1.
Table 1

Field

ChannelType

Min Value Max Value

Description+X PANEL V

0

Unsigned

0x00

0xFFF

+X PANEL V-X PANEL V

1

Unsigned

0x00

0xFFF

-X PANEL V+Y PANEL V

2

Unsigned

0x00

0xFFF

+Y PANEL V-Y PANEL V

3

Unsigned

0x00

0xFFF

-Y PANEL V+Z PANEL V

4

Unsigned

0x00

0xFFF

+Z PANEL V-Z PANEL V

5

Unsigned

0x00

0xFFF

-Z PANEL V

MPPT VOUT

6

Unsigned

0x00

0xFFF

MPPT VBATT V

Not used

7

-

-

-

-

3.1.2 The measured data fields for Device 2 and their associated ADS 7828
channels shall be as shown in Table 2.
Table 2Field

Channel

Type

Min
Value

Max
Value

Description

MPPT PCB
Temperature0

Unsigned

0x00

0xFFF

Temperature of
MPPT card-Y PANEL T

1

Unsigned

0x00

0xFFF

-Y PANEL T+Z PANEL T

2

Unsigned

0x00

0xFFF

+Z PANEL T+X PANEL T

3

Unsigned

0x00

0xFFF

+X PANEL TMPPT Current

4

Unsigned

0x00

0xFFF

MPPT Output
Current+Y PANEL T

5

Unsigned

0x00

0xFFF

+Y PANEL T-X PANEL T

6

Unsigned

0x00

0xFFF

-X PANEL T-Z PANEL T

7

Unsigned

0x00

0xFFF

-Z PANEL T

Page 3 of 4

AMSAT Fox-1
IHU to PSU ICD
3.1.3 Measurements shall be made in relation to the 2.5 VDC internal voltage
reference for both ADS 7828 Devices.
3.1.4 For each Device the IHU shall poll each channel in channel number order.

Page 4 of 4

AMSAT Fox-1C/D
IHU to DOWNSHIFTER ICD
Date: June 9, 2015
Version: Version 1.10

AMSAT Fox-1C/D
IHU to “L-Band DOWNSHIFTER” Interface Control
Document
1 Introduction
This document specifies the message interface between the Internal Housekeeping Unit
(IHU) and the payload in Experiment Position 4 of the satellite, known as the L-Band
DOWNSHIFTER and abbreviated herein as EXP4.
1.1

Document History
DATE

VERSION

SUMMARY

June 7, 2015

1.00

Initial version

June 9, 2015

1.10

Added 2.1.2

1.2 Document Scope
This document will specify the control of EXP4, and the IHU operation of EXP4.
1.3 References
1. AMSAT Fox-1, System Requirements Specification
2. AMSAT Fox-1, System Design Specification
3. AMSAT Fox-1, IHU Software Architecture Specification

Page 1 of 2

AMSAT Fox-1C/D
IHU to DOWNSHIFTER ICD

2 EXP4 Operation
2.1

EXP4 Power Control
The IHU shall exert control over the power state of the EXP4 by theExperiment Enable 3 pin on the satellite bus as shown in Table 1.

Table 1Pin State

Voltage

Description

High

≥ 2.4

Power On ExperimentLow, or high-impedance< 2.4

Power Off Experiment

EXP4 may draw current from the system bus while in the OFF state in orderto power the antenna path switching circuits required for its operation.
2.2

EXP4 Power On Sequence
Upon receiving an L-BAND MODE command the IHU shall set and hold theExperiment Enable 3 pin HIGH.

2.3

EXP4 Operation
Upon receiving an L-BAND MODE command the IHU shall perform thefollowing actions.

2.3.1.1 Operating mode shall be set to TRANSPONDER MODE.
2.3.1.2 A software timer shall be started to count down 86400 seconds.

2.3.1.2.1 At the expiration of the timer, the IHU shall perform the EXP4
Power Off Sequence.
Upon receiving an L-BAND MODE command while the software timer isrunning, the software timer shall begin counting down from 86400 seconds.
Upon receiving any command other than an L-BAND MODE command the
IHU shall perform the EXP4 Power Off Sequence.
The default power state for EXP4 on IHU restart shall be OFF.
2.4

EXP4 Power Off Sequence
The IHU shall set the Experiment Enable 3 pin LOW.

2.4.1.1 The absence of a HIGH state on the Experiment Enable 3 pin shall be
construed as a LOW state whether the pin is actually LOW, or in a highimpedance state.
The software timer shall be stopped.

Page 2 of 2

June 7, 2015
Version 3.11

1

SPI1 NSSSPI1 SCK
57

TX Temperature

SPI1 MISO

9

13

6

RX Temperature

Serial2 RXD

8

RSSI

Serial2 TXD

11

4

Experiment 4 Thermistor

SPI1 MOSI

2

BUS

3

TX PA Current

10

IHU Audio Out

12

Experiment Enable 1
15

14

Experiment Enable 2
17

19

Experiment Enable 3
Experiment Enable 4

21

Serial1 RXD
23

25

Serial1 TXD
29

31Solar Safe N
Alert Signal

33-Z Deploy Switch 1
35

37-Z Deploy Switch 2
I²C2 SCL

39

43

C
O
N
N
E
C
T
O
R

26

IHU PTT

28

RF TX Active

30
RX CD

32

RX Audio

34
36

Sensor Power38

TX Frequency Control

40

RX Frequency Control

42-Y Antenna Deploy

44-Y Antenna Sensor-Z CIC46+Y Antenna Sensor

Umbilical USBP
51

24

IHU RF Control+Z CIC

49

22

RX Command Strobe-Z Thermistor

47

20

RX Command Data 3+Z Thermistor

45

18

RX Command Data 2

I²C2 SDA
41

16

RX Command Data 1

Q
S
H

I²C1 SCL
I²C1 SDA

27

RX Command Data 0

48+Y Antenna Deploy

50

Umbilical USBM
53

55

52

Umbilical Power Active

54

Solar Power A

Solar Power B

Vbatt

57
59

56

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 7, 2015
Version 3.11

1

SPI1 NSSSPI1 SCK
57

TX Temperature

SPI1 MISO

9

13

6

RX Temperature

Serial2 RXD

8

RSSI

Serial2 TXD

11

4

Experiment 4 Thermistor

SPI1 MOSI

2

IHU

3

TX PA Current

10

IHU Audio Out

12

Experiment Enable 1
15

14

Experiment Enable 2
17

19

Experiment Enable 3
Experiment Enable 4

21

Serial1 RXD
23

25

Serial1 TXD
29

31Alert Signal
33
35

37

I²C2 SCL
39

16

RX Command Data 1

Q
S
H

18

RX Command Data 2

20

RX Command Data 3

I²C1 SCL
I²C1 SDA

27

RX Command Data 0

22

RX Command Strobe

C
O
N
N
E
C
T
O
R

24

IHU RF Control

26

IHU PTT

28

RF TX Active

30
RX CD

32

RX Audio

34
36

Sensor Power

I²C2 SDA38

TX Frequency Control

41

40

RX Frequency Control

43

42-Y Antenna Deploy
45

44-Y Antenna Sensor
47

49+Y Antenna Sensor
Umbilical USBP

51

46
48

+Y Antenna Deploy

50

Umbilical USBM
53

52

Umbilical Power Active

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 7, 2015
Version 3.11

1

2
4
5

PSU

3
6

7

8
9

10
11

12

13

14
15

16
17

18

Q
S
H

19
21

20
22

23

24

25
27
29
31

Solar Safe N
Alert Signal

33-Z Deploy Switch 1
35

37-Z Deploy Switch 2
I²C2 SCL

39

C
O
N
N
E
C
T
O
R

26
28
30
32
34
36
Sensor Power38

I²C2 SDA
41

43

40

+Z Thermistor

42-Z Thermistor
45-Y Antenna Deploy+Z CIC
47

44-Y Antenna Sensor-Z CIC46+Y Antenna Sensor

49

48+Y Antenna Deploy

50

51

52
53

55

54
Solar Power A

Solar Power B

Vbatt

57
59

56

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 7, 2015
Version 3.11

1

2

BATT 1

3

4
5

6

7

8
9

10
11

12

13

14
15

16
17

18

Q
S
H

19
21

20
22

23

24

25
27
29
31

Solar Safe N
Alert Signal

33-Z Deploy Switch 1
35

37-Z Deploy Switch 2
I²C2 SCL

39

C
O
N
N
E
C
T
O
R

26
28
30
32
34
36
Sensor Power38

I²C2 SDA

40

41

42

43

44
45

46
47

49

48
Umbilical USBP

51

50

Umbilical USBM
53

55

52

Umbilical Power Active

54

Solar Power A

Solar Power B

Vbatt

57
59

56

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 7, 2015
Version 3.11

2
3

RF Receiver

1
4
5

6

7

RX Temperature
9

8

RSSI

10

11

12

13

14
15

16
17

18

Q
S
H

19
21

20
22

23

24

C
O
N
N
E
C
T
O
R

25
27
29
31
33
35
37

26
28
RF TX Active

30
RX CD

32

RX Audio

34
36

Sensor Power

38

39

40
41

RX Frequency Control

42

43

44
45

46
47

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 7, 2015
Version 3.11

1

TX PA Current
TX Temperature

RF Xmtr

3

2
4

5

6

7

8
9

10
11

IHU Audio Out

12

13

14
15

16
17

18

Q
S
H

19
21

20
RX Command Data 3

22

23

24

25
27
29
31
33

-Z Deploy Switch 1
35-Z Deploy Switch 2

37

C
O
N
N
E
C
T
O
R

IHU RF Control

26

IHU PTT

28

RF TX Active

30
RX CD

32

RX Audio

34
36

Sensor Power

39

38

TX Frequency Control

40

41
43

42
-Z Thermistor

44

45

46
47

-Z CIC

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 7, 2015
Version 3.11

2
1

10
9

28
27

30
29

32
31

34
33

36
35

38
37

22
21

26

C
O
N
N
E
C
T
O
R
25

20

Q
S
H
19

12
11

16
15

18
17

24
23

40
39

42
41

46
45

48
47

52
51

54
53

58

57

60

59

BATT 2

4
3

6
5

8
7

14
13

44
43

50
49

56

55

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 7, 2015
Version 3.11

1

2
4
5

VUC

3
6

7

8
9

10
11

13

12
Experiment Enable 1

14

15

16
17

18

Q
S
H

19
21
23
25

20
22

I²C1 SCL
I²C1 SDA

27
29
31
33
35
37

24

C
O
N
N
E
C
T
O
R

26
28
30
32
34
36
38

39

40
41

42

43

44
45

46
47

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 7, 2015
Version 3.11

2
1

10
9

30
29

32
31

34
33

36
35

38
37

60

Vbatt

Vbatt

59

28
27

22
21

26

C
O
N
N
E
C
T
O
R
25

20

Q
S
H
19

58

Vbatt

Vbatt

57

12
11

16
15

18
17

24
23

40
39

42
41

46
45

48
47

52
51

54
53

EXP 2

4
3

6
5

8
7

14
13

44
43

50
49

56

55

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 7, 2015
Version 3.11

1

2

VT CAM

3

4
5

6

7

8
9

Serial2 RXD

10Serial2 TXD

11

12

13

14
15

16
17

19

18
Experiment Enable 4

21

Q
S
H

20
22

23

24

C
O
N
N
E
C
T
O
R

25
27
29
31
33
35
37

26
28
30
32
34
36
38

39

40
41

42

43

44
45

46
47

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 7, 2015
Version 3.11

1

2

L BAND

3

4
5

Experiment 4 Thermistor

6

7

8
9

10
11

12

13

14
15

16
17

Experiment Enable 3

18

Q
S
H

19
21

20
22

23

24

C
O
N
N
E
C
T
O
R

25
27
29
31
33
35
37

26
28
30
32
34
36
Sensor Power

38

39

40
41

+Z Thermistor

42

43

44
45

+Z CIC

46

47

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 6, 2015
Version 3.10

1

SPI1 NSSSPI1 SCK
57

TX Temperature

SPI1 MISO

9

13

6

RX Temperature

Serial2 RXD

8

RSSI

Serial2 TXD

11

4

Experiment 4 Thermistor

SPI1 MOSI

2

BUS

3

TX PA Current

10

IHU Audio Out

12

Experiment Enable 1
15

14

Experiment Enable 2
17

19

Experiment Enable 3
Experiment Enable 4

21

Serial1 RXD
23

25

Serial1 TXD
29

31Solar Safe N
Alert Signal

33-Z Deploy Switch 1
35

37-Z Deploy Switch 2
I²C2 SCL

39

43

C
O
N
N
E
C
T
O
R

26

IHU PTT

28

RF TX Active

30
RX CD

32

RX Audio

34
36

Sensor Power38

TX Frequency Control

40

RX Frequency Control

42-Y Antenna Deploy

44-Y Antenna Sensor-Z CIC46+Y Antenna Sensor

Umbilical USBP
51

24

IHU RF Control+Z CIC

49

22

RX Command Strobe-Z Thermistor

47

20

RX Command Data 3+Z Thermistor

45

18

RX Command Data 2

I²C2 SDA
41

16

RX Command Data 1

Q
S
H

I²C1 SCL
I²C1 SDA

27

RX Command Data 0

48+Y Antenna Deploy

50

Umbilical USBM
53

55

52

Umbilical Power Active

54

Solar Power A

Solar Power B

Vbatt

57
59

56

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 6, 2015
Version 3.10

1

SPI1 NSSSPI1 SCK
57

TX Temperature

SPI1 MISO

9

13

6

RX Temperature

Serial2 RXD

8

RSSI

Serial2 TXD

11

4

Experiment 4 Thermistor

SPI1 MOSI

2

IHU

3

TX PA Current

10

IHU Audio Out

12

Experiment Enable 1
15

14

Experiment Enable 2
17

19

Experiment Enable 3
Experiment Enable 4

21

Serial1 RXD
23

25

Serial1 TXD
29

31Alert Signal
33
35

37

I²C2 SCL
39

16

RX Command Data 1

Q
S
H

18

RX Command Data 2

20

RX Command Data 3

I²C1 SCL
I²C1 SDA

27

RX Command Data 0

22

RX Command Strobe

C
O
N
N
E
C
T
O
R

24

IHU RF Control

26

IHU PTT

28

RF TX Active

30
RX CD

32

RX Audio

34
36

Sensor Power

I²C2 SDA38

TX Frequency Control

41

40

RX Frequency Control

43

42-Y Antenna Deploy
45

44-Y Antenna Sensor
47

49+Y Antenna Sensor
Umbilical USBP

51

46
48

+Y Antenna Deploy

50

Umbilical USBM
53

52

Umbilical Power Active

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 6, 2015
Version 3.10

1

2
4
5

PSU

3
6

7

8
9

10
11

12

13

14
15

16
17

18

Q
S
H

19
21

20
22

23

24

25
27
29
31

Solar Safe N
Alert Signal

33-Z Deploy Switch 1
35

37-Z Deploy Switch 2
I²C2 SCL

39

C
O
N
N
E
C
T
O
R

26
28
30
32
34
36
Sensor Power38

I²C2 SDA
41

43

40

+Z Thermistor

42-Z Thermistor
45-Y Antenna Deploy+Z CIC
47

44-Y Antenna Sensor-Z CIC46+Y Antenna Sensor

49

48+Y Antenna Deploy

50

51

52
53

55

54
Solar Power A

Solar Power B

Vbatt

57
59

56

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 6, 2015
Version 3.10

1

2

BATT 1

3

4
5

6

7

8
9

10
11

12

13

14
15

16
17

18

Q
S
H

19
21

20
22

23

24

25
27
29
31

Solar Safe N
Alert Signal

33-Z Deploy Switch 1
35

37-Z Deploy Switch 2
I²C2 SCL

39

C
O
N
N
E
C
T
O
R

26
28
30
32
34
36
Sensor Power38

I²C2 SDA

40

41

42

43

44
45

46
47

49

48
Umbilical USBP

51

50

Umbilical USBM
53

55

52

Umbilical Power Active

54

Solar Power A

Solar Power B

Vbatt

57
59

56

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 6, 2015
Version 3.10

2
3

RF Receiver

1
4
5

6

7

RX Temperature
9

8

RSSI

10

11

12

13

14
15

16
17

18

Q
S
H

19
21

20
22

23

24

C
O
N
N
E
C
T
O
R

25
27
29
31
33
35
37

26
28
RF TX Active

30
RX CD

32

RX Audio

34
36

Sensor Power

38

39

40
41

RX Frequency Control

42

43

44
45

46
47

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 6, 2015
Version 3.10

1

TX PA Current
TX Temperature

RF Xmtr

3

2
4

5

6

7

8
9

10
11

IHU Audio Out

12

13

14
15

16
17

18

Q
S
H

19
21

20
RX Command Data 3

22

23

24

25
27
29
31
33

-Z Deploy Switch 1
35-Z Deploy Switch 2

37

C
O
N
N
E
C
T
O
R

IHU RF Control

26

IHU PTT

28

RF TX Active

30
RX CD

32

RX Audio

34
36

Sensor Power

39

38

TX Frequency Control

40

41
43

42
-Z Thermistor

44

45

46
47

-Z CIC

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 6, 2015
Version 3.10

2
1

10
9

28
27

30
29

32
31

34
33

36
35

38
37

22
21

26

C
O
N
N
E
C
T
O
R
25

20

Q
S
H
19

12
11

16
15

18
17

24
23

40
39

42
41

46
45

48
47

52
51

54
53

58

57

60

59

BATT 2

4
3

6
5

8
7

14
13

44
43

50
49

56

55

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 6, 2015
Version 3.10

1

2

HERCI

3

4
5

6

7

8
9

10
11

13

12
Experiment Enable 1

14

15

16
17

18

19
21

Serial1 RXD

Q
S
H

20
22

23

24

25
27

Serial1 TXD
29

31
33
35
37

C
O
N
N
E
C
T
O
R

26
28
30
32
34
36
38

39

40
41

42

43

44
45

46
47

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 6, 2015
Version 3.10

2
1

10
9

30
29

32
31

34
33

36
35

38
37

60

Vbatt

Vbatt

59

28
27

22
21

26

C
O
N
N
E
C
T
O
R
25

20

Q
S
H
19

58

Vbatt

Vbatt

57

12
11

16
15

18
17

24
23

40
39

42
41

46
45

48
47

52
51

54
53

EXP 2

4
3

6
5

8
7

14
13

44
43

50
49

56

55

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 6, 2015
Version 3.10

1

2

VT CAM

3

4
5

6

7

8
9

Serial2 RXD

10Serial2 TXD

11

12

13

14
15

16
17

19

18
Experiment Enable 4

21

Q
S
H

20
22

23

24

C
O
N
N
E
C
T
O
R

25
27
29
31
33
35
37

26
28
30
32
34
36
38

39

40
41

42

43

44
45

46
47

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED

June 6, 2015
Version 3.10

1

2

L BAND

3

4
5

Experiment 4 Thermistor

6

7

8
9

10
11

12

13

14
15

16
17

Experiment Enable 3

18

Q
S
H

19
21

20
22

23

24

C
O
N
N
E
C
T
O
R

25
27
29
31
33
35
37

26
28
30
32
34
36
Sensor Power

38

39

40
41

+Z Thermistor

42

43

44
45

+Z CIC

46

47

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

LEGEND

SystemANTENNAS

EXPERIMENTSALL

PSU/BATTUMBILICALRF

Connections

CONNECTEDIN USECONNECTEDNOT IN USE

NOTCONNECTEDNOT USED



"

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AMSAT Fox-1
Maximum Power Point Tracker
Date: October 2, 2015
Version: 1.1
Author: Bryce Salmi, KB1LQC

AMSAT Fox-1 Maximum Power Point Tracker
Introduction
The Radio Amateur Satellite Corporation, AMSAT, has designed and built a series of 1U Cubesats
referred to as Fox-1. Starting with these 1U Cubesats, AMSAT will build up intellectual property to leverage
onto future satellite designs. A requirement for the Fox-1 satellites is an efficient way to maximize power
generation from solar cells with a scalable Maximum Power Point Tracker, MPPT. Based on the Fox-2
design originally conceived by the P13271 senior design team1 at the Rochester Institute of Technology
AMSAT has developed a radiation tolerant analog MPPT for use on the Fox-1 satellites. Lessons learnedbuilding the Fox-1 MPPT detailed in this document can also be rolled into any future Fox-2 MPPT design.

Document History
DATE

VERSION

SUMMARY

January 21, 2015

1.0

Initial creation of document

October 2, 2015

1.1

Updated with flight design

Document Scope
The purpose of this document is to clearly explain how the Fox-1 MPPT has been designed, how
it operates, and to how any known failure modes or risks affect the spacecraft. Only PCB Revision 1.1 of
the Fox-1 MPPT is detailed in this document. It also assumes a basic level of electrical knowledge andleaves some calculations up to the reader with reference material noted.

Figure 1: Fox-1 MPPT Rev 1.1

1

Bryce Salmi (KB1LQC), Brenton Salmi (KB1LQD), Ian MacKenzie (KB3OCF), Dan Corriero

Page 1 of 35

AMSAT Fox-1
Maximum Power Point Tracker
Contents

Introduction ............................................................................................................................................... 1
Document History ................................................................................................................................. 1
Document Scope ................................................................................................................................... 1
Overview ....................................................................................................................................................... 3
Specifications ............................................................................................................................................ 3
Spectrolab UTJ Solar Cells ......................................................................................................................... 4
MPPT PCB Configuration........................................................................................................................... 5
PCB Block Diagram ................................................................................................................................ 5
PCB Design ................................................................................................................................................ 6
PCB Stackup .......................................................................................................................................... 7
Maximum Power Point Tracker Design......................................................................................................... 8
MPPT Overview ......................................................................................................................................... 8
MPPT Schematics ...................................................................................................................................... 9
Resistive Temperature Detector Circuitry .......................................................................................... 10
Totem Pole MOSFET Driver ................................................................................................................. 15
Buck Converter.................................................................................................................................... 16
MPPT Feedback ................................................................................................................................... 17
Output Voltage Regulation Feedback ................................................................................................. 18
TL1451A Pulse-Width Modulation Controller ..................................................................................... 20
Ideal Diode .......................................................................................................................................... 23
Telemetry Circuitry ............................................................................................................................. 25
RTD Panel Temperature Scaling .......................................................................................................... 30
Test Results ................................................................................................................................................. 30
MPPT Operation...................................................................................................................................... 30
Oscilloscope Captures ............................................................................................................................. 32
Appendix ..................................................................................................................................................... 33
Fox-1 Solar Panel Calculations ................................................................................................................ 33
Maximum Power Point Tracking Theory................................................................................................. 34

Page 2 of 35

AMSAT Fox-1
Maximum Power Point Tracker

Overview
The Fox-1 MPPT PCB contains six set-point constant voltage MPPT circuits2 with a single MPPT
dedicated to each side of the spacecraft. Every side of Fox-1 contains two Spectrolab UTJ solar cells
connected in series. All six MPPTs are combined through ideal diodes which allows for power sharing as
the satellite rotates in orbit. The common diode OR’d output node then delivers the combined power ofall sufficiently illuminated solar panels to the spacecraft main voltage bus. The Fox-1 MPPT also contains
a telemetry circuit able to communicate with the Internal Housekeeping Unit, IHU, via I2C
communications. It’s important to note that each of the six MPPTs is a zero fault tolerant design.

Specifications
Parameter

Value

Units

Maximum Input Voltage

50

Volts

Minimum Input Voltage

3.6

Volts

Maximum Input Current (Per MPPT)

0.443

Amperes

Maximum Input Power (Per MPPT)

2.57

Watts

Maximum Output Current (Per MPPT)

0.780

Amps @ 3.3V Vout

Maximum Output Voltage

4.33V

Volts

Maximum Switching Efficiency~88%

Maximum Tracking Error+-5%

Temperature Range of Components-40° to +125°

Celsius

Solar Cell Operating Temperature Range-60° to +60°

Celsius

Table 1: Overall Fox-1 MPPT Specifications

Careful use of radiation tested components, shielding, and a stateless design in the critical MPPT
feedback loops on Fox-1 has been implemented in order to promote a 5 year mission timeline and an
estimated 30kRad TID exposure. The stateless design hardens the MPPT to Single Event Upsets, SEU, andSingle Event Latch-ups, SEL, which are expected during the mission. Table 1 documents the general
specifications achieved as supported by engineering bring-up data.
2

http://cdn.intechopen.com/pdfs-wm/37984.pdf

Page 3 of 35

AMSAT Fox-1
Maximum Power Point Tracker

Spectrolab UTJ Solar Cells
Fox-1 was designed for use with two SpectroLab UTJ solar cells in series on each solar panel witheach cell having 27 cm2 of area as shown in Figure 2. Table 11 in the Appendix shows the calculations of
the maximum power point thermal drift. This information was used to design the MPPT as well as predict
the amount of power available to Fox-1 at any panel temperature expected in orbit. The RTD measuring
panel temperature is mounted to the back side of the solar panels out of direct sunlight.

Figure 2: Solar panels on Fox-1, a stowed antenna is shown on the closest facing solar panel

Page 4 of 35

AMSAT Fox-1
Maximum Power Point Tracker

MPPT PCB Configuration
PCB Block Diagram

Figure 3: Fox-1 MPPT PCB block diagram containing six individual MPPT circuits combined together

Six Individual Maximum Power Point Trackers obtain power from their respective solar panels andif sufficient power is available then combine the generated power onto a common output
node through ideal diodes. The combined power is then fed through a current sense circuit before being
sent to the Fox-1 “VBATT” node to power the satellite and charge the batteries. A telemetry systemcomprised of voltage dividers, RC low pass filters, and ADC’s gather engineering data for transmission to
the IHU via I2C communications.
The design of the Fox-1 MPPT does not require a battery on the output of the PCB for proper
operation. In the event of a battery failure where a properly designed circuit will disconnect the battery
from the satellite power bus, the MPPT is fully capable of operation. The requirement for this operation
however is that no more than maximum power available from the MPPT can be requested from thepayload. This means that if the satellite can operate by never drawing more power than the lowest power
available from solar panels then indefinite operation without a battery is possible.

Page 5 of 35

AMSAT Fox-1
Maximum Power Point Tracker
Power is obtained from the X and Y axis panels through PCB edge connectors (Samtec MEC1-10502-L-D-NP-A) and through the board-to-board connectors (Samtec QSH-030-01-L-D-A and QTH-030-02-LD-A). Besides solar power, signals passing through these PCB edge connectors are the RTD connections(ground referenced) for measurement of each solar panel temperature as well as two antenna deploy andsense channels on the Y panels. The antenna deploy and sense connections are not thoroughly coveredin this document, please refer to the schematic. All copper planes have been pulled back from theconnector and a maximum of 20 mil traces were used to the connectors themselves to prevent heat loss
to space from the MPPT PCB which is necessary for proper operation

Figure 4: Samtec QTH-030-02-L-D-A board to board connector shown on left side of image, Samtec MEC1-105-02-L-D-NP-A edge
connector shown near middle of image with male portion of connector made of PCB material

PCB Design
Each PCB is a four layer board developed in the open source KiCad EDA (Build: 2013-07-07 BZR4022)-stable on Windows. Gerber files were exported and sent to Advanced Circuits for fabrication. Since
Gerbers are very portable file formats, AMSAT has the ability to use almost any manufacturer they choose.
All relevant PCB processes have been documented in the “Drawings” Layer of the Gerbers.

Page 6 of 35

AMSAT Fox-1
Maximum Power Point Tracker
PCB Stackup

Figure 5: Four layer PCB stackup used on the Fox-1 MPPT Rev 1.1 PCB

Figure 6: Fox-1 MPPT Rev 1.1 PCB with top layer visible, all components other than stacking connector located on top layer

Page 7 of 35

AMSAT Fox-1
Maximum Power Point Tracker

Maximum Power Point Tracker Design
MPPT Overview
The Fox-1 MPPT is designed as a temperature based set-point constant voltage MPPT and is
implemented with analog circuitry to mitigate radiation events associated with holding state. There are
two discrete feedback loops implemented in the design, the MPPT feedback loop and an output voltage
regulation feedback loop. Both MPPT feedback loop and MPPT as a PCB will be referred to in thisdocument and the context will determine the subject. The output voltage regulation circuitry limits the
MPPT channel output voltage to 4.33V prior to the ideal diodes in order to protect the Fox-1 payload andbatteries from overvoltage conditions. Using temperature based MPPT allowed power to be maximized
without computational resources such as a microcontroller which requires state.

Figure 7: Fox-1 MPPT & voltage regulation feedback block diagram

As shown in Figure 7, there are two feedback loops used to control the TL1451A PWM
controller. The internal TL1451A error amplifier is used as a unity gain buffer to directly pass the
combined ܸ௘௥௥௢௥ signal from the external error amplifiers into the internal comparator used to generate
the PWM signal. The inversions from the TL1451A open collector PWM output and PMOS gate create
the following ܸ௘௥௥௢௥ to duty cycle relationship shown in Table 2.
ࢂࢋ࢘࢘࢕࢘ Change

PWM Duty Cycle

Increasing

Decreasing

Decreasing

Increasing

Table 2: Error voltage effect on the PWM duty cycle

Page 8 of 35

AMSAT Fox-1
Maximum Power Point Tracker
Therefore, a simple diode-OR is used to combine both the MPPT error amplifier and output
voltage regulation error amplifier signals. This results in the highest voltage error signal applied to the
TL1451A winning control of the buck converter and forcing the lowest duty cycle of the two feedback loops
to be implemented. This is extremely advantageous as shown later in this document.

MPPT Schematics
The latest version of the schematics for the Fox-1 MPPT are located in the AMSAT SVN MPPT
folder. Using KiCad to open “TL1451_MPPT_Flight_Rev1.pro” one has access to the schematics and PCB
files within the KiCad EDA. An important note is that the libraries and footprints used for KiCad live in the
SVN Power KiCad folder so those must be checked out too and Kicad may need to be told where they areon your computer to display properly. An annotated PDF version of the schematics is provided with thisdocument.

Figure 8: Main schematic page of the Fox-1 MPPT closely resembling the block diagram in Figure 3

The schematics are built up in a hierarchical arrangement as shown in Figure 8 much like block
diagrams that contain sub-circuits within individual blocks. This makes understanding signal flows mucheasier and is very different from how EAGLE presents schematics. The main schematic page looks a lot likethe overview block diagram shown in Figure 3. Hierarchical design results in a large number of schematics
sheets due to channelization of the design. An annotated schematic included with this document at the2015 AMSAT Symposium details all unique MPPT PCB circuits without duplication.

Page 9 of 35

AMSAT Fox-1
Maximum Power Point Tracker
Resistive Temperature Detector Circuitry

Figure 9: RTD drive and sensing block diagram

The AMSAT MPPT uses resistive temperature detectors, RTDs, to accurately measure solar panel
temperature which is then used to predict the Maximum Power Point Voltage, MPPV. A constant current
source forces exactly 1 mA into the RTD leaving only voltage to change with varying resistance as the RTDchanges temperature. Both voltage and resistance are directly correlated as governed by Ohms law whenusing a constant current source. The measured voltage developed across the RTD is conditioned andamplified using a simultaneous equation based op-amp circuit implementing analog mathematics. This
produces a voltage mimicking the solar panel voltage at MPPV and can be referenced by the MPPT error
amplifier as it compares real panel voltage against this predicted reference voltage. This scaled voltage
produced by the amplifier is referred to as ܸ௧௘௠௣ . The RTD used for each panel is a PT100 type device,
nominally 100Ω at 0°C (PTS080501B100RP100). RTDs are not thermistors, they use a pure metal such as
nickel or platinum which have very accurate and predictable changes in resistance over temperature andnearly linear responses over the temperature ranges used.

Figure 10: Fox-1 MPPT RTD constant current driverPage 10 of 35

AMSAT Fox-1
Maximum Power Point Tracker
U3A of Figure 10 is a LM6144A op-amp configured as a constant 1 mA source. Its sole purpose is
to force exactly 1 mA of current through the RTD. ͳͳ shows a LTSpice schematic of the 1 mA RTD
driver and is used to describe the RTD circuit for the remainder of this description. The following equation
determines the output voltage of the op-amp U1:
ܸ‫ ݐݑ݋‬ൌ ܸଶ ൬ܴସܴଶ ൅ ܴଵܴଵ൰ൈ൬൰ െ ܸଵ ൈܴଷ ൅ ܴସ
ܴଶܴଶ

Where ܸଶ is the reference voltage and ܸଵ is the grounded pad of ܴଵ . However, sinceܴଵ ǡ ܴଶ ǡ ܴଷ ǡ and ܴସ are
all 249KΩ we simplify the equation down to:ܸை௎் ൌ ܸଶ െ  ܸଵ ൌ ʹǤͷV

Figure 11: LTSpice 1mA RTD drive simulation schematic, capacitors not simulated.

Knowing we have 2.5V across R7 due to op-amp laws the following relationship for drive current is made.
ܴ଻ ൌܸଶ‫ܫ‬஽௥௜௩௘ൌʹǤͷܸൌ ʹǤͷ‫ܭ‬πͳ݉‫ܣ‬With 1 mA of drive current being forced into R8 (a 100Ω RTD) the voltage across it is predictable
thanks to Ohms Law. 1 mA of drive current will dissipate about 100uW of power in the RTD and therefore
cause minimal internal self-heating of the device and allows for accurate measurements. Table 3 shows
several data points along the operating conditions expected in orbit for the solar panels and the respective
RTD circuit voltage.

Page 11 of 35

AMSAT Fox-1
Maximum Power Point Tracker
RTD Temperature Voltage Across RTD-60°C

0.076V

0°C

0.100V

28°C

0.111V+60°C

0.124V

Table 3: Expected RTD voltages at 1mA drive current

The voltage across the RTD is very small (between 76mV and 124mV) and exhibits a positive
thermal coefficient. This means the voltage increases as the temperature increases. However, the solar
cells exhibit a negative temperature coefficient since the MPPT voltage decreases with a temperature
increase. An op-amp configured to follow a polynomial equation is used to amplify the measured RTD
voltage and flip the RTD voltage thermal coefficient. Essentially the op-amp performs the function ‫ ݕ‬ൌെ݉ܺ ൅ ܾ as covered in SLOA076 from Texas Instruments. The flight conditioning circuit implementing
analog mathematics is shown in Figure 12. Note that the feedback capacitor C162 is not accounted for in
the PCB layout and on MPPT Rev 1.1 was soldered in parallel across the feedback resistor by physicallystacking the capacitor onto of R18.

Figure 12: Scaling amplifier implemented on the Fox-1 MPPT panel temperature circuit which mimics solar panel MPPV

Page 12 of 35

AMSAT Fox-1
Maximum Power Point Tracker

Figure 13: An LTSpice simulation of the RTD scaling amplifier, capacitors not simulated

Figure 13 shows the LTSpice simulation of the RTD conditioning amplifier referenced in thefollowing description. Voltage source V1 represents the RTD voltage being measured and V3 represents
the 2.5V reference from the TL1451A. A capacitor is added in the flight circuit across R6 to ground to low
pass filter the voltage reference as shown in Figure 12. Another capacitor has been placed across R8 in
the flight circuit to reduce the bandwidth of the circuit for stability also shown in Figure 12. A differential
amplifier was not used to buffer the RTD since the solar panel PCBs have already been produced and were
designed for thermistors which have one of the pins grounded and therefore the RTDs have a grounded
pin too, rendering a differential amplifier not effective.
The TL1451A recommended error amplifier input voltage range is 1.05V to 1.45V so thepanel voltage has been scaled by 0.245 using voltage dividers before being measured. The RTD predicted
panel voltage must mimic this scaled voltage. The voltages in the Fox-1 Solar Panel Calculations in the
Appendix show that minimum MPPV is obtained when high temperature panels are tracked at 4.28V andthe maximum MPPV is 5.84V when the panels are tracked at low temperatures. This results in a MPPV
voltage range of 1.048V to 1.430V present at the MPPT error amplifier during nominal power point
tracking. These voltages are used as part of the simultaneous equations solved in SLOA076 and are given
in Table 4 which are used to translate RTD measured voltages into the predicted MPPV reference voltageܸ௧௘௠௣ . The predicted voltage is also telemetered to sense panel temperature remotely from Earth via RF
telemetry. With some basic mathematics described in the ADC section of this document the panel
temperature can be resolved back from this voltage as measured by the ADC.

Page 13 of 35

AMSAT Fox-1
Maximum Power Point Tracker
RTD Temperature

RTD Voltage

Vout Desired

60°C

0.124V

1.048V-60°C

0.076V

1.430V

Table 4: Voltages used to solve for the scaling amplifiers component values

The values used for the output voltage of the scaling amplifier were chosen based on obtainable resistor
values resulting in the following equation relating Vout of Figure 13 to RTD voltage:
ܸை௎் ൌ  െͺǤͳͶʹʹͺ ή ܸூே ൅ ʹǤͲͷʹ͵
Figure 14 shows the RTD voltage versus scaling amplifier output voltage (predicted MPPV). The
amplifier clearly amplifies the voltage as well as flips the temperature coefficient to match the Spectrolab
solar cell based panel temperature coefficient.

Figure 14: Simulated RTD voltage input to the amplifier and output voltage representing the scaled panel voltage desired. The
top graph shows the RTD voltage over the expected operating range while the bottom graph shows the resulting op-amp output
voltage for the

Page 14 of 35

AMSAT Fox-1
Maximum Power Point Tracker
Totem Pole MOSFET Driver
The PWM output from the TL1451A is an open collector circuit and cannot provide a low
impedance drive signal into the switching MOSFET gate. A low impedance drive signal is necessary toquickly turn the MOSFET on and off. A pull-up resistor, R11 in Figure 15, is connected to the open collector
pin of the TL1451A where the PWM signal is output. More information can be found regarding MOSFET
drivers in SLUP169 from TI.

Figure 15: Open collector PWM output and totem pole MOSFET driver

The TL1451A output open collector stage inverts the signal produced by the PWM generator
which is then fed into the totem pole driver (Q2 in Figure 15) which is a non-inverting circuit. The totem
pole operates by pulling the MOSFET gate close to ground or close to the solar panel voltage, well into
saturation or cutoff of the switching MOSFET. When the TL1451A open collector output pulls towards
ground this will cause the PNP transistor base of Q2 (pin 5) to be a lower voltage than its emitter (pin 4
assumed at Vpanel) forcing the device into conduction and draining the MOSFET gate (GATE-DRIVE) into
ground. Panel voltage from the open collector when it is open circuit will cause the PNP of Q2 to go into
cutoff (base is higher voltage than emitter near ground) and then drive the NPN base (pin 2) to a higher
voltage than the NPN emitter (pin 1) also near ground. This puts the NPN device into conduction andconnects the solar panel voltage to the gate of the MOSFET. The voltage of the MOSFET gate will always
be around a VBE below panel voltage or above ground during cutoff and saturation respectively.

Page 15 of 35

AMSAT Fox-1
Maximum Power Point Tracker
Buck Converter

Figure 16: Fox-1 MPPT buck converter switching circuitry

A standard buck converter has been implemented on the Fox-1 MPPT as shown in Figure 16. The
output of the totem pole MOSFET driver (GATE-DRIVE) is fed into PMOS_PWM which drives the gate of
the P-channel device (PMOS) through a 6.04Ω resistor to dampen ringing. Standard buck converter design
techniques were followed (SLVA477) to derive initial component values. The values in Table 5 show theparameters used to initially design the buck converter stage, these are assumptions about operating
conditions prior to actually building the converter.
50mA was assumed to be the lowest current the buck converter would see when operating toguarantee continuous conduction mode and 780mA is the amount of current the coldest solar panel
operating at MPPT would dump into a fully discharged battery at 3.3V. These are bounds which create adesign capable of operating at all times in Fox-1. The design is non-synchronous and uses a catch diode asshown in Figure 16Error! Reference source not found.. Increased efficiency could be realized with asynchronous design in the future. Additionally, snubbing and boot RC circuits have been added to allow
the control of ringing and edge rise time if necessary from the switching node to ground and the source
to drain of the switching MOSFET. In the event that the series resistance to the gate is disconnected, apullup resistor R61 has been implemented to provide fault tolerance by forcing the MOSFET off in that
failure mode.

Page 16 of 35

AMSAT Fox-1
Maximum Power Point Tracker
Parameter

Value

Unit

Minimum Input Voltage

4.284

Volts

Maximum Input Voltage

6.464

Volts

Minimum Output Voltage

3.3

Volts

Maximum Output Voltage

4.33

Volts

Minimum Current

0.050

A

Maximum Current

0.780

A

Assumed Efficiency

90%

Minimum Duty Cycle

0.5

Ratio

Maximum Duty Cycle

0.98

Ratio

Table 5: Basic buck converter parameters used for the Fox-1 MPPT design

MPPT Feedback
Maximum Power Point Tracking on Fox-1 is achieved by predicting the expected MPPV
determined by the measured solar panel temperature using an RTD as previously described. The solar
panel voltage, ܸ௣௔௡௘௟ , and predicted MPPV, ܸ௧௘௠௣ , are fed into a dedicated MPPT error amplifier built
using an LM6144A op-amp as shown in Figure 17.

Figure 17: Maximum Power Point Tracking error amplifier

In Figure 17 the solar panel voltage is applied to the voltage divider created by R7 and R8 scaling
the panel voltage by 0.245 and driving the inverting input of the op-amp U3C while the RTD measured

Page 17 of 35

AMSAT Fox-1
Maximum Power Point Tracker்ܸ௘௠௣ signal is applied to the non-inverting input as the reference voltage for the error amplifier. The opamp output voltage,ܸ௘௥௥௢௥ , is determined by the following equationܸை௎் ൌ ‫ ܣ‬ή ሺܸூேା െ ܸூேି ሻ ൌ ‫ ܣ‬ή ሺ்ܸ௘௠௣ െ ܸ௣௔௡௘௟ ή ͲǤʹͶͷሻThis means that given a large gain A from U3C, the output of of the error amplifier will decrease towards
ground whenever the panel voltage is greater than the predicted ்ܸ௘௠௣ . Likewise, when ܸ௉௔௡௘௟ is lower
than ்ܸ௘௠௣ the output voltage increases towards the VCC voltage rail (panel voltage). The following
relationship can be determined:ࢂࢋ࢘࢘࢕࢘ Change

PWM Duty Cycle Change

Panel Voltage

Output Voltage

Increasing

Decreasing

Increasing Voltage

Decreasing Voltage

Decreasing

Increasing

Decreasing Voltage

Increasing Voltage

Table 6: MPPT error amplifier output effect on solar panel and MPPT output voltage

Type-III compensation has been implemented due to the use of ceramic capacitors which exhibit
a high frequency resonance with the buck converter and cause a near 180° phase-lag at the crossover
frequency: a recipe for switch-mode converter instability. More information about compensating buckconverters can be found in SLVA301 from TI and specifically for Type-III in AN-1162 from International
Rectifier.
A crossover frequency of 25 KHz was chosen after building the MPPT and performing engineering
tests. It was discovered that the TL1451A could not change the output voltage quick enough at its
switching frequency when the bandwidth of the error amplifier was set much higher. Therefore, 25KHz
was empirically chosen but cannot be drastically increased without instability. This bandwidth is fasterthan necessary to respond to a spinning Cubesat and provides adequate transient performance.

Output Voltage Regulation Feedback
The purpose of the output voltage regulation error amplifier is to limit the maximum output
voltage allowed to 4.33V at all times to protect the payload. A maximum of 4.33V accounts for somevoltage drop from the ideal diode resulting in about 4.2V maximum at the battery. When this error
amplifier is in control of the buck converter the maximum power of the solar panel is disregarded. Thismeans the operating point is indeterminate but also unnecessary to know since full power is not needed.
This occurs when the output voltage is close to 4.33V due to a fully charged battery and enough powerfrom the panels is available to not discharge the batteries. Moving away from the maximum power pointcauses the extra power to dissipate as heat in the solar cells, radiating into space.
Much like the MPPT feedback error amplifier, the output voltage regulation error amplifier isimplemented with a discrete LM6144A op-amp and compensated with a Type-III compensator. A 25KHz
crossover frequency of the compensation network was also chosen to play nice with the TL1451A PWM
controller. Refer to Figure 18 for the schematic of the voltage regulation error amplifier.

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AMSAT Fox-1
Maximum Power Point Tracker

Figure 18: Output voltage regulation error amplifier

The output voltage regulation error amplifier is configured such that the 2.5V voltage reference(from the TL1451A) is applied to the inverting error amplifier input and the buck converter output voltage,
ܸை௨௧௣௨௧ (VMPPT), is applied to the non-inverting input. This is a classic voltage regulation error amplifier
scheme. Notice that in Figure 18 C33 is DNP’d and a note to remove it is present. During engineering bringup testing it was determined that C33 caused a low frequency oscillation of the converter and should be
removed (along with respective capacitors in other MPPT channels).
The op-amp output voltage is determined by the following equation where A is the open loop gain
and the output voltage is scaled to regulate to 4.33V. The resulting duty cycle characteristics can beobserved in Table 7. Notice how the effects of the voltage regulation error amplifier signal are exactly thesame as the MPPT error signal. The schematic in Figure 18 shows the Type-III compensation modified
slightly to invert the output of the LM6144A used as a voltage regulator and match the necessary ܸ௘௥௥௢௥
polarity for implementation of the overall circuit characteristics detailed in Table 2.
ܸ௘௥௥௢௥ ൌ ‫ ܣ‬ή ሺܸூேା െ ܸூேି ሻ ൌ ‫ ܣ‬ή ሺͲǤͷ͹͹ ή  ܸை௨௧௣௨௧ െ ܸ௥௘௙ ሻ
Whenever the output voltage ܸை௨௧௣௨௧ is larger than the 2.5V reference, the error amplifier
increases its output voltage and PWM duty cycle will trend towards 0% in an effort to reduce ܸை௨௧௣௨௧ .
Consequently, whenever ܸை௨௧௣௨௧ is lower than the 2.5V reference, the error amplifier signal will trend
towards ground and the duty cycle will trend up towards 100% in an effort to increase the output voltage.

Page 19 of 35

AMSAT Fox-1
Maximum Power Point Trackerࢂࢋ࢘࢘࢕࢘ Change

PWM Duty Cycle Change

Panel Voltage

Output Voltage

Increasing

Decreasing

Increasing Voltage

Decreasing Voltage

Decreasing

Increasing

Decreasing Voltage

Increasing Voltage

Table 7: Output voltage regulation duty cycle characteristics

TL1451A Pulse-Width Modulation Controller
Converting error signals into Pulse-Width Modulation, PWM, signals is the job of the Texas
Instruments TL1451A PWM controller shown in Figure 19. This IC provides two synchronized PWM circuits
but only one is used on Fox-1, coupling of failure modes of a single TL1451A removing two MPPTs fromservice was unwarranted. It was also the only PWM controller IC found to operate at the low voltages
required and most ASIC MPPTs could not operate above panel voltage of 5V. The TL1451A obtains power
directly from the panel it’s controlling and therefore it turns on when the panel reaches 3.6V, well above
the LM6144A op-amp providing the input error signals which turns on at 1.8V. Thus ensuring valid input
signals when powered on. The PWM generator uses an RC oscillator comprised of C2 and R5 running thecircuit at a nominal 500 KHz. Frequency stability is not critical but thermal stability is highly recommended.
The internal error amplifier is setup in a unity-gain configuration and simply buffers the externallygenerated error signals coming from the MPPT and voltage regulation error amplifiers detailed earlier.

Figure 19: The TL1451 circuitry on Fox-1 used to convert error signals into PWM signals controlling the buck converter

Page 20 of 35

AMSAT Fox-1
Maximum Power Point Tracker
As shown in Figure 20, the TL1451A uses the error signal from Error Amplifier 1 to compare witha triangle wave generated by the oscillator. The dead time control, DTC, pin is grounded in Figure 19 as it
is disabled. Short-circuit protection, SCP, is also grounded and therefore disabled since solar panels
effectively limit the short circuit current. The error signal from Error Amplifier 1 (unity gain) is sent into
the PWM comparator and then into an AND gate (always passes due to DTC pin configuration) which
drives an open-collector NPN output transistor. Figure 21 shows the error signal and corresponding
waveforms related to the TL1451A.

Figure 20: TL1451 block diagram from TI's datasheet SLVS024E

Figure 21: Example error amplifier to PWM open collector output signal path from TI’s datasheet SLVS024E

Page 21 of 35

AMSAT Fox-1
Maximum Power Point Tracker
The magic inside the Fox-1 MPPT happens at the output of the MPPT and voltage feedback error
amplifiers shown in Error! Reference source not found.. Both error signals are combined in a diode-OR
configuration with D8, a common cathode Schottky diode array. This combined error signal is sent directly
into the TL1451A error amplifier. R1 is a pull down resistor necessary to allow proper operation bydischarging the node slightly.

Figure 22: MPPT and output voltage regulation error amplifiers diode-OR connection into TL1451A error amplifier

The resulting effect of the diode-OR circuit combining the error signals in Figure 22 is that thehighest voltage error amplifier always wins control of the TL1451A. As noted in Table 2, an increasing error
signal demands a lower duty cycle which means this circuit properly interfaces with the PWM controller.
Once an error amplifier voltage drops below the other, D8 will reverse bias for that amplifier. The voltage
drop across D8 does not matter because the error amplifiers will force up to the solar panel voltage out
in an effort to decrease duty cycle (4.28V “lowest” maximum voltage during operation) and automaticallycompensate for this loss as regulation is maintained.
How MPPT and Voltage Regulation Coexist
It’s important to remember the overall interaction of the MPPT and voltage regulation feedback
loops must coexist with the input and output power scenarios presented to Fox-1. When the Fox-1
payload is not transmitting and has just finished charging its batteries in full sunlight the panels will becapable of delivering maximum power to the satellite which is no longer using all the power generated.
At this point the MPPT feedback loop is in control. Since more power is delivered to the output thanneeded the output voltage rises and attempts to go above 4.33V. At this point the voltage regulation error
amplifier output rises quickly and overtakes the MPPT voltage, reverse biasing D8 for the MPPT error
signal, in an effort to reduce the duty cycle and maintain output regulation at 4.33V. This causes the solar
panel voltage to rise towards open circuit voltage as less current is being pulled from it, delivering lessPage 22 of 35

AMSAT Fox-1
Maximum Power Point Tracker
power to the payload. Meanwhile, the MPPT feedback loop rails low in an effort to increase the duty cycle,
trying to reduce the panel voltage towards MPPV but the output voltage regulation error signal will remain
in control since highest error amplifier voltage wins control of the TL1451A. Saturation of the op-amps as
they rail towards ground in any case is not really an issue since spacecraft rotation is on the order of a few
rotations per minute which allows the op-amps ample time to desaturate.
When Fox-1 enters eclipse with fully charged batteries it will discharge them during the eclipse
period. The MPPT is off during this time, however when Fox-1 just comes out of eclipse into sunlight thebatteries will be discharged which forces the MPPT output voltage lower than 4.33V. The output voltageof the converter is governed by the battery voltage. The output voltage regulation error amplifierattempts to increase duty cycle to increase the output voltage and increases charging current into thebatteries, pulling more current from the solar panels. This continues until the MPPT error amplifier senses
that the solar panel voltage has decreased to the predicted MPPV. At this point the voltage regulation
error signal has decreased in an effort to increase duty cycle as the panel voltage lowered; delivering moreenergy to the output in order to maintain 4.33V. However, the MPPT error signal has also started toincrease and will eventually be higher than the voltage regulation error signal, forward biasing the D8 forthe voltage regulation error signal, causing the maximum power point to be tracked. This remains true
until the converter output voltage rises towards 4.33V when the batteries have fully charged and thevoltage regulation loop regains control.
The end result is a feedback loop configuration on Fox-1 that only delivers maximum power tothe satellite when the satellite demands it; otherwise the MPPT circuitry uses its voltage regulator
feedback loop to protect the downstream electronics and moves the solar panels away from MPPT. The
MPPT is not expected to properly charge the batteries, which is the job of the battery PCB and circuitry.

Ideal Diode
Each of the six MPPTs has an ideal diode immediately following the buck converter as shown in
Figure 23. This provides an efficient power diode-OR function and permits power sharing between MPPTs.
Each ideal diode connects to a common output node that is fed into a current sense amplifier before
sending power to the Fox-1 payload. The LTC4411 (U1) provides the ideal diode function with only 140mΩ
of resistance which equates to 85mW of loss at the maximum output current of 780 mA. The output status
pin is not used and the control pin which is active low is pulled up to the solar panel voltage whenever thesolar safe circuit is enabled (remove before flight pin inserted); disabling the MPPT from powering Fox-1
at all. This is a launch vehicle safety feature demanded by some launch providers.

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AMSAT Fox-1
Maximum Power Point Tracker

Figure 23: The LTC4411 ideal diode and accompanying solar safe circuitry shown with the MPPT converter circuitry

Solar Safe
In an effort to comply with PPOD and launch vehicle integration needs, the solar safe circuit isused to disconnect all MPPT circuits from the satellite, thus ensuring there is no way the satellite canobtain power while the remove before flight, RBF, pin is inserted. The solar safe signal is active low and isessentially a shorting bar to ground. Therefore while the RBF pin is inserted into its hole on Fox-1 the gateof Q4, is pulled to ground and turned off. This forces the ideal diode U1 in Error! Reference source notfound. to turn off because the control pin is pulled high when the MPPT circuit turns on in sunlight.
Since the gate of Q4 is pulled up through R190 and D7, the shorting RBF pin will conduct throughthe respective devices to ground. R190 limits the current and D7 is used to prevent a reverse conduction
path between each panel. When the RBF pin is the gate of Q4 is pulled up when the solar panel is in
sunlight causing Q4 to conduct, pulling the LTC4411 control pin to ground and enabling the flow of current
onto the satellite power bus from each MPPT.

Solar Safe is a common node among all six MPPT’s of Fox-1. A single piece ofForeign Object Debris, FOD, or other fault pulling this node to ground in flight willcompletely disable all MPPT’s. Disconnecting all MPPTs will cause the satellite to
fail once the batteries have been depleted as they can no longer charge.

Page 24 of 35

AMSAT Fox-1
Maximum Power Point Tracker
Telemetry Circuitry
The telemetry circuitry on the Fox-1 MPPT consists of analog voltage, current, and temperaturesensing which are digitized by two 12-bit ADS7828 ADC’s. Power for all sensing circuitry is obtained fromthe IHU which is disabled when an IHU failure occurs. Sensor Power is provided from the PCB stackconnector and is a regulated 3V. The idea for obtaining power from the IHU is that if/when the IHU
gracefully fails it will go into a safe state which disconnects all telemetry power turning off the ADCs andsupport circuitry for them. This is largely a legacy requirement due to original Fox-1A circuitry designs.
PCB Temperature Thermistor Scaling
PCB temperature is measured by a thermistor powered by sensor power (3V) and attached to alinearizing circuit. The thermistor, TH1, is shown in Figure 24 and is linearize by R37, R38, and R39 whilestabilized by C16. The resulting voltage is connected to Channel 0 of ADC 2. The linearizing circuit is basedon the output from the Vishay Resistor/Thermistor Netsim Tool.

Figure 24: NTC thermistor linearizing circuit used to measure PCB temperature

Page 25 of 35

AMSAT Fox-1
Maximum Power Point Tracker
Output Current Sense

Figure 25: All MPPTs combine and feed through a current sense circuit for telemetry purposes

The common I_SENSE+ node is a combination of all six MPPT outputs following their respective
ideal diodes. The INA195 from Texas Instruments is a 100V/V current shunt monitor measuring thevoltage across a parallel combination of R22 and R185 shown in Figure 25. The shunt resistors are dual
redundant to protect against a bad solder or vibration damage on one resistor causing complete current
path loss and consequently mission failure.
In a parallel configuration the current shunt is nominally 0.0255Ω and will drop 19.9mV at the
maximum output current of 780mA which is amplified by the INA195 to 1.989V. This dissipates about
15.5mW of power between both resistors at maximum current. In a fault case of either shunt resistor, asingle 0.051Ω resistor will dissipate 31mW and the INA195 will attempt to amplify the signal up to 3.9V at
maximum current but the output will be saturated at 3V from sensor power provided by the IHU. Table 8shows the nominal and fault operation characteristics of the amplifier. Since the maximum output current
from a single MPPT is 780mA, a failure of R22 or R185 will be observable as 980 mA whenever the current
is expected to go over 490mA due to ground telemetry scaling coefficients. This should be obvious whencompared to nominal operation data as full scale operation should not be common.
Shunt Resistance

ADC Full Scale Current

Mode0.0255Ω

980mA

Nominal

0.051Ω

490mA

Fault

Table 8: Current shunt and amplifier values in nominal and fault modes of R22 and R185

Following the current sense amplifier is a capacitive input PI filter used to provide a low passfilter for MPPT voltage powering Fox-1. The parallel capacitor across L7 provides a deep null at theswitching frequency.

Page 26 of 35

AMSAT Fox-1
Maximum Power Point Tracker
Voltage Scaling Circuitry
The voltage dividers shown in Figure 26 scale all panel voltages by 0.428. This scaled voltage isthen input into the low pass filters of the ADCs detailed next.

Figure 26: Voltage dividers used to scale solar panel voltages

Analog-to-Digital Converters
The ADS7828 ADCs communicate to the IHU via the I2C protocol over the PCB stack connectors.
These 12-bit ADCs are powered from 3V sensor power provided by the Fox-1 IHU card. The reasoning forthis power configuration is to ensure that the ADC’s are only turned ON/OFF when the microcontroller isoperating correctly. Internal 2.5V references are used by the ADS7828 ADCs as commanded by the Fox-1
IHU via I2C. This means each bit represents 610.4 uV on the ADC input, providing adequate resolution.
Figure 27 and Figure 28 show the ADCs as implemented on the Fox-1 MPPT PCB.
16 Hz low pass filters are used to filter out high frequency content as telemetry is only sampled
once every 15 seconds. This was deemed a suitable and realistic filter value. On-board IHU oversampling
could be used to prevent aliasing but most signals of interest are so low frequency that avoiding aliasing
is not a huge concern and that topic is outside the scope of this document. The filters also provide current
limiting functionality for ADC protection. The series 10KΩ resistors limit current into the ADC to no morethan about 320uA per channel when the ADC is on and about 650uA per channel when the ADC is off. It
is important to remember that this only occurs during fault cases if signal conditioning circuits short panel
voltage to the low pass filters. The limiting resistance works in conjunction with internal protection diodes
inside the ADS7828 which conduct into the sensor power rail and ground.

Page 27 of 35

AMSAT Fox-1
Maximum Power Point Tracker

Figure 27: ADC 1 used to obtain PCB temperature, solar panel temperature, and output current telemetry.

Figure 28: ADC 2 used to obtain solar panel and MPPT output voltage telemetry.

Page 28 of 35

AMSAT Fox-1
Maximum Power Point Tracker
The I2C communications defined in the AMSAT PSU to IHU ICD states that the IHU will be the I2C
master while the MPPT PCB ADCs will be slaves and that communications are established at 10 KHz. For
more I2C details please refer to the AMSAT PSU to IHU ICD.
ADC 1 (I2C Address = 0x49)
ADC Channel

Telemetry Signal

Bit Scaling (Y = mX + b)

0

PCB Temperature

Same as LDO PCB on Fox-1A

1-Y Solar Panel RTD Resistancem = -0.074961, b = 252.1

2+Z Solar Panel RTD Resistancem = -0.074961, b = 252.1

3+X Solar Panel RTD Resistancem = -0.074961, b = 252.1

4

MPPT Output Current

m = 2.3935E-4, b = 0

5+Y Solar Panel RTD Resistancem = -0.074961, b = 252.1

6-X Solar Panel RTD Resistancem = -0.074961, b = 252.1

7-Z Solar Panel RTD Resistancem = -0.074961, b = 252.1

Table 9: ADC 1 telemetry signals and scaling factors

ADC 2 (I2C Address = 0x4A)
ADC Channel

Telemetry Signal

Bit Scaling (Y = mX + b)

0

+X Solar Panel Voltage

m = 0.001647, b = 0

1-X Solar Panel Voltage

m = 0.001647, b = 0

2+Y Solar Panel Voltage

m = 0.001647, b = 0

3-Y Solar Panel Voltage

m = 0.001647, b = 0

4+Z Solar Panel Voltage

m = 0.001647, b = 0

5-Z Solar Panel Voltage

m = 0.001647, b = 0

6

MPPT Output Voltage

m = 0.001647, b = 0

7

UNUSED (Grounded)

NONE

Table 10: ADC 2 telemetry signals and scaling factors

Page 29 of 35

AMSAT Fox-1
Maximum Power Point Tracker
RTD Panel Temperature Scaling
Solar panel temperature is measured by a RTD on each solar panel and analog mathematics
performed by op-amps condition this voltage to mimic the solar panel MPPV. These mathematics can bereversed to directly calculate RTD resistance. Table 9 contains the RTD scaling values which compute theresistance in Ohms from the bit value of the ADC. The ADC scaling values implement a simplified form of
the equation belowܴோ்஽ ሺπሻ ൌ  ቎ʹǤͷܸ‫ ݏݐ݅ܤܥܦܣ‬ൈ ቀͶͲͻ͸ቁ െ ʹǤͲͷʹ͵െͺǤͳͶʹʹͺͳ൰቏ൈ൬ͲǤͲͲͳ‫ܣ‬All values used to determine the RTD scaling values were rounded to the 6th decimal place as thisequation is pure mathematics and considered ideal. The TL1451A reference voltage has a pretty loose
initial tolerance and essentially must be calibrated out to make the temperature sensing via ADCs very
accurate. This is an MPPT specific process that results in six calibration values for each satellite and isoutside the scope of this document. A cubic fit is used to convert RTD resistance into degrees Celsius. The
basic formula for a cubic fit of a PT100 RTD is:ܶ݁݉‫݁ݎݑݐܽݎ݁݌‬ሺ‫ܥ‬ሻ ൌ  െʹͶ͹Ǥʹͻ ൅ ʹǤ͵ͻͻʹ ൈ ܴ ൅ ͲǤͲͲͲ͸͵ͻ͸ʹ ൈ ܴ ଶ ൅ ͳǤͲʹͶͳ‫ ܧ‬െ ͸ ൈ ܴ ଷ

Test Results
Testing was performed using a combination of digital multimeters, an active load, an ArduinoTM
with a current sense circuit and I2C communications, and a digital oscilloscope. Various other tools wereused but are not relevant to this document. Circuit operation as well as performance data will beshowcased in an annotated form.

MPPT Operation
Operation of the MPPT is clearly shown in Figure 29. A 2.5 Farad super capacitor was used as abattery simulator to hold up the output voltage and allow plotting of a nice graph. As shown, thecapacitor started fully charged at about 4.25V and was constant current discharged down to 3.3V where
the load was removed. More power was demanded from the MPPT PCB than the maximum power thesolar panel simulators could provide causing a slow but linear decrease in panel voltage. The super
capacitor was then allowed to charge back up. It’s obvious to see that the panel voltage was near the
open circuit voltage when the capacitor was fully charged but as the capacitor voltage decreased the
MPPT feedback loop kicked in and forced the panel down to about 4.8V to operate at maximum power(+-5% error at 0C). When the capacitor charged back up the MPPT feedback loop lost control and thevoltage regulation feedback loop took over limiting capacitor voltage but allowing panel voltage to rise.

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AMSAT Fox-1
Maximum Power Point Tracker

Figure 29: -X Panel operation as obtained by ADC telemetry through an Arduino TM test setup and an external current sense tocomputer input and output power for efficiency calculations

Figure 30 nicely plots the input and output power of the MPPT and the resulting efficiency.
Numbers are only valid during the time the test is occurring. The output power has a linear decreasing
slope which is caused by series resistance from the buck converter, ideal diode, and current sense
circuits. Ohm’s law! The power reaching the MPPT output drops as I2R losses increase when output
current increases as the capacitor voltage decreased and conservation of power must be maintained.

Figure 30: -Z panel operation showing solar panel power output, MPPT output power, and resulting efficiency over a super
capacitor discharge test

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AMSAT Fox-1
Maximum Power Point Tracker

Oscilloscope Captures
To showcase some of the MPPT operations Figure 31 is an oscilloscope capture of an MPPT load
test. Channel 1 (top) is the simulated solar panel voltage, Channel 2 (middle) is the output voltage, andChannel 3 (bottom) is the switching node of the buck converter. A 50mA constant current load was thesteady state operation condition the test started in. This means the MPPT was actually in voltage
regulation mode to begin the test. A 1A constant current transient was immediately placed onto the
output of the MPPT (super capacitor) as a large load causing the capacitor voltage to sag slightly as
shown in channel 2 when the test occurred about 100us from the left edge of the screen. Please note
this test is extremely unforgiving and unrealistic in orbit but a great example non-the-less.
Transitioning from voltage regulation mode into MPPT mode, the solar panel voltage dipped a
bit below the maximum power point and then rose back up to maintain MPPT. Channel 3 clearly shows
the duty cycle of the buck converter changing as the feedback loops maintain regulation. The switchingnode duty cycle is the important observation and absolute voltage of the switching node will track withthe panel voltage as shown. Complete tradeoff of voltage regulation to MPPT regulation is observed inthis oscilloscope capture. This event occurred in about 1ms from beginning to end which is more thansufficient for on-orbit performance since spacecraft rotation is much slower.

Figure 31: MPPT Operating with a charged super capacitor simulating a battery experiencing a load transient. Load was intense
50mA to 1A transient.

Page 32 of 35

AMSAT Fox-1
Maximum Power Point Tracker

Appendix
Fox-1 Solar Panel Calculations
Fox-1 Solar Panel
PV Temp (C)
-60
-55
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
28
30
35
40
45
50
55
60

VOC (V)
6.464
6.399
6.334
6.269
6.204
6.139
6.074
6.009
5.944
5.879
5.814
5.749
5.684
5.619
5.554
5.489
5.424
5.359
5.320
5.294
5.229
5.164
5.099
5.034
4.969
4.904

VMPP (V)
5.844
5.779
5.714
5.649
5.584
5.519
5.454
5.389
5.324
5.259
5.194
5.129
5.064
4.999
4.934
4.869
4.804
4.739
4.700
4.674
4.609
4.544
4.479
4.414
4.349
4.284

IMPP (A)
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440
0.440

PMPP (W)

Table 11: Estimated operating parameters of the Fox-1 solar panel using two Spectrolab UTJ cells in series

Page 33 of 35

2.571
2.543
2.514
2.486
2.457
2.428
2.400
2.371
2.343
2.314
2.286
2.257
2.228
2.200
2.171
2.143
2.114
2.086
2.068
2.057
2.028
2.000
1.971
1.943
1.914
1.886

AMSAT Fox-1
Maximum Power Point Tracker

Maximum Power Point Tracking Theory
Solar Panels convert the Sun’s energy into electrical power for use by Fox-1. Due to the highimpedance nature of solar cells, the payload can drastically affect the amount of power extracted fromthe cells by changing the voltage of panels with current draw from them. There is a specific voltage at
which the maximum amount of power may be extracted which is called the Maximum Power Point
Voltage, MPPV. This voltage varies with temperature and solar irradiance. An MPPT follows the maximum
power point as it moves due to environmental disturbances.
The standard view of solar cell performance is by that of a current-voltage curve or IV curve asshown in Figure 32 from the Spectrolab UTJ solar cells used on Fox-1. To understand how to obtain
information from the chart start with the two extremes. An open-circuit conducts no current and will
operate the solar cell at the maximum voltage of about 2.66V on the bottom right of the IV curve. As
current drawn from the solar cell is increased by the payload, the operating point of the solar cell moves
from right to left along the plotted line. Under a short circuit condition the solar cell shows zero volts ofpotential and deliver about 17.05 mA/cm2 of solar cell area to the load.

Figure 32: Spectrolab UTJ 28.3% efficiency solar cell IV curve

These two extremes both produce zero power in the ideal world.
ܲ‫ ݎ݁ݓ݋‬ൌ ʹǤ͸͸ܸ ൈ Ͳ‫ ܣ‬ൌ Ͳܹܽ‫ݏݐݐ‬ሺ‫ݐ݅ݑܿݎ݅ܿ݊݁݌݋‬ሻܲ‫ ݎ݁ݓ݋‬ൌ Ͳܸ ൈ ͳ͸Ǥ͵ ݉‫ܣ‬ൗ ଶ ൌ Ͳܹܽ‫ݏݐݐ‬ሺ‫ݐ݅ݑܿݎ݅ܿݐݎ݋݄ݏ‬ሻܿ݉The “knee” of the IV curve shown at about 2.35V on the x-axis is the maximum power point where
the most energy can be extracted from the solar cell and delivered to the payload. Figure 33 shows
example power curves and IV curves are as the values vary with temperature and irradiance of the solar
cells. Notice how temperature is a huge contributor to changing the maximum power point.

Page 34 of 35

AMSAT Fox-1
Maximum Power Point Tracker

Figure 33: Solar panel MPPT versus temperature and irradiance changes. Image used from http://www.electronicproducts.com

A maximum Power Point Tracker is an intermediate circuit between the solar panels and thebattery/satellite which isolates the source from the load in order to maintain the solar panel voltage at
the MPPV. MPPTs are implemented with DC/DC converters and can be seen as impedance converters
which match the high impedance of the solar panel (about 13Ω on Fox-1) to the payload which is usuallymuch higher (low power needs) or much lower (high power needs) impedance. Used as an intermediatetranslator of impedances, the MPPT serves to decouple payload needs from solar panel operating point.

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(B\WHV)

&200$1'MLQ
9DOXHMD[9DOXH

DHVFULSWLRQ

8QVLJQHG [

[

+H[DGHFLPDO&RPPDQG

2SWLRQDO$UJXPHQWV
$V5HTXLUHG

T\SH$5*80(17 9DULDEOH 8QVLJQHG
7KH FRPPDQG PHVVDJH EORFN VKDOO FRQWDLQ RQH FRPPDQG LQ WKH &200$1'
ILHOGDVVKRZQLQ7DEOH
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62

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3DJHRIAMSAT)R[% 5DG)[6DW 
I+8WR([SHULPHQWICD
TDEOH

CRPPDQG
1DPH

SL]H
(B\WHV)

MLQ
9DOXH

T\SH

MD[9DOXH

DHVFULSWLRQ

1RS



(FKR



1RHIIHFWUHVSRQVH
8QVLJQHG [ [ XQGHILQHG7HVWIRU,ð&
DFNQRZOHGJHPHQWRQO\8QVLJQHG [ [ (FKRWKLVE\WHVWUHDP

5HVHQG

8QVLJQHG [ [ 5HVHQGODVWUHVXOW*HW8,'

8QVLJQHG [ [ &RQWUROOHUE\WH
LGHQWLILHU

*HW6WDWXV

8QVLJQHG [ [ &RQWUROOHUVWDWXVLQGLFDWLRQ*HW'LDJQRVWLFV

8QVLJQHG [ [ 6HOIFKHFN'LDJQRVWLF

*HW
7HOHPHWU\

8QVLJQHG [ [ 6HQGWHOHPHWU\GDWD

6HW5XQ
6WDWH

8QVLJQHG [ [ (QWHUVSHFLILHG5XQ
6WDWH

*HW5XQ
6WDWH

8QVLJQHG [ [ 4XHU\FXUUHQW5XQ
6WDWH

6HW7LPH

8QVLJQHG [ [ 1XPEHURIVHFRQGVVLQFHHSRFK*HW7LPH

8QVLJQHG [ [ 1XPEHURIVHFRQGVVLQFHHSRFK*HW'DWD

8QVLJQHG [ [ 6HQG QXPEHURIE\WHV 
GDWD7KHFRPPDQGPHVVDJHVKDOOFRQWDLQDUJXPHQWVIRUWKH (FKRFRPPDQG
DVVKRZQLQ7DEOH

TDEOH

)LHOG

SL]H
(B\WHV)

T\SH

MLQ
9DOXHMD[9DOXH

DHVFULSWLRQ

$5*80(17

8QVLJQHG'DWDWREH
HFKRHG

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3DJHRI63

AMSAT)R[% 5DG)[6DW 
I+8WR([SHULPHQWICD
7KHFRPPDQGPHVVDJHVKDOOFRQWDLQRQHDUJXPHQWIRUWKH6HW5XQ6WDWHFRPPDQGDVVKRZQLQ7DEOH
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TDEOH

5XQSWDWH

SL]H
(B\WHV)

T\SH

MLQ
9DOXHMD[9DOXH

DHVFULSWLRQ

67$1'%<

8QVLJQHG[

[(QWHU6WDQGE\
6WDWH

$&7,9(

8QVLJQHG[

[

$FWLYDWH
([SHULPHQWV

+$/7



8QVLJQHG[

[

7HUPLQDWH([SHULPHQWV
7KH FRPPDQG PHVVDJH VKDOO FRQWDLQ DUJXPHQWV IRU WKH 6HW 7LPH
FRPPDQGDVVKRZQLQ7DEOH
TDEOH

SL]H
(B\WHV)

AUJXPHQW

T\SH

MLQ
9DOXHMD[9DOXH

,+85HVHW
&RXQWHU

8QVLJQHG

[



0(7
7LPHVWDPS

8QVLJQHG

DHVFULSWLRQ&RXQWRIWKHQXPEHURI
,+8UHVHWVIURPQRQYRODWLOH)5$0
0(7WLPHVWDPSVHFRQGVVLQFHODVW,+8
UHVHW 
7KH FRPPDQG PHVVDJH VKDOO FRQWDLQ DUJXPHQWV IRU WKH *HW 'DWD
FRPPDQGDVVKRZQLQ7DEOH
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TDEOHAUJXPHQWSL]H(B\WHV)

T\SH

MLQ
9DOXHMD[9DOXH

DHVFULSWLRQ

%<7(672
6(1'



8QVLJQHG[[))

1XPEHURIE\WHVWR
VHQG  

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64

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3DJHRIAMSAT)R[% 5DG)[6DW 
I+8WR([SHULPHQWICD 5HVSRQVH0HVVDJH%ORFN
7KHUHVSRQVHPHVVDJHEORFNVKDOOEHFRQVWUXFWHGDVVKRZQLQ7DEOH

TDEOH)LHOG

SL]H
(B\WHV)

T\SH

MLQ
9DOXHMD[9DOXH

DHVFULSWLRQ

5(6(59('

8QVLJQHG

5HVHUYHGLJQRUH

(5525
&2'(

8QVLJQHG [

[

5HVSRQVHWR
&RPPDQG

/(1*7+

8QVLJQHG[[))))

/HQJWKRI5HWXUQ
9DOXHLQ%\WHV

5(7851
9$/8(

9DULDEOH

9DULDEOH

5HWXUQ9DOXH
7KH(UURU&RGHVKDOOFRQWDLQRQHFRGHDVVKRZQLQWDEOH
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3DJHRI65

AMSAT)R[% 5DG)[6DW 
I+8WR([SHULPHQWICD
TDEOH

SL]H
(B\WHV)

1DPH
&0'B2.

&0'B23B(55MLQ
9DOXHMD[9DOXH

DHVFULSWLRQ

8QVLJQHG [ [

&RPPDQGLQYRNHG
VXFFHVVIXOO\

8QVLJQHG [ [

&RPPDQGQRWUHFRJQL]HG

T\SH&0'B)250$7B(55

8QVLJQHG [ [,QFRUUHFWFRPPDQGDUJXPHQWOHQJWK

&0'B5$1*(B(55

8QVLJQHG [ [$UJXPHQW V 
RXWRIERXQGV

&0'B3(&B(55

8QVLJQHG [ [

(UURUFKHFN
&5& 
PLVPDWFK

&0'B(;(&B(55

8QVLJQHG [ [([HFXWLRQHUURU

8QVLJQHG [ ;

+HDGHU
0HVVDJH
9HUVLRQPLVPDWFK&0'B9(56,21B(557KH 6WDWXV )ODJV IRU D *(7 67$786 UHVSRQVH PHVVDJH VKDOO EH
UHSUHVHQWHGDVLQGLYLGXDOELWYDOXHVRIDELW5(78519$/8(DVVKRZQLQ7DEOH

TDEOH

1DPH

BLW
1XPEHU

DHVFULSWLRQ

5(%227(' ([SHULPHQWKDVUHERRWHG–12786(''$7$5($'< ([SHULPHQWGDWDDYDLODEOH

7,0(5(48(67 5HTXHVW6(77,0()$,/('58167$7( )DLOHGWKHUXQVWDWH–12786('&203/(7('58167$7( &RPSOHWHGWKHUXQVWDWH–12786('

5(6(59('$OZD\V

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66

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3DJHRIAMSAT)R[% 5DG)[6DW 
I+8WR([SHULPHQWICD
7KHUHVSRQVHPHVVDJHWRD6HW7LPHFRPPDQGVKDOOFRQWDLQRQHRIWKH
YDOXHVDVVKRZQLQ7DEOH

TDEOH

5HVSRQVH
1DPH

SL]H
(B\WHV)

T\SH

MLQ
9DOXH

68&&(66



6LJQHG[)$,/85(

6LJQHG [)))) [))))

MD[
9DOXH[DHVFULSWLRQ
7LPH6HWVXFFHVVIXOO\
7LPH6HWIDLOHG 0HVVDJH,QWHJULW\1 ,QYDOLG0HVVDJHV,IWKH3(& &5& IDLOVWKHPHVVDJHVKDOOEHFRQVLGHUHGLQYDOLG,IWKH0HVVDJH9HUVLRQGRHVQRWPDWFKWKHPHVVDJHYHUVLRQLQXVHIRUWKH
FRQVWUXFWLRQRIPHVVDJHVRQWKHUHFHLYLQJV\VWHPWKHPHVVDJHVKDOOEHFRQVLGHUHGLQYDOLG

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3DJHRI
67

AMSAT)R[% 5DG)[6DW 
I+8WR([SHULPHQWICD

 0HVVDJH)ORZ'LDJUDPV1 (;3(5,0(1732:(5216(48(1&(

IHU

EXP1
ASSERT EXPERIMENT 1 ENABLE

SET TIMERESPONSEIHU HandlingEnd (;3(5,0(17%(*,123(5$7,216(48(1&(

IHU

EXP1
SET RUN STATE: ACTIVERESPONSEIHU Handling

End



68

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3DJHRIAMSAT)R[% 5DG)[6DW 
I+8WR([SHULPHQWICD (;3(5,0(17&($6(23(5$7,216(48(1&(


IHU

EXP1
SET RUN STATE: HALTRESPONSESET RUN STATE: STANDBYRESPONSEIHU HandlingEnd (;3(5,0(1732:(52))6(48(1&(


IHU

EXP1
DEASSERT EXPERIMENT 1 ENABLE

IHU HandlingEnd 6(59,&,1*(;3(5,0(1723(5$7,21

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3DJHRI69



AMSAT)R[% 5DG)[6DW 
I+8WR([SHULPHQWICD)LJXUH

IHU

EXP1
GET STATUS

STATUS = REBOOTED or FAILED or COMPLETEDIHU Handling

End




)LJXUH

IHU

EXP1
GET STATUS
STATUS = TIME REQUESTSET TIMERESPONSEIHU Handling

End



70

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

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3DJHRI

AMSAT)R[% 5DG)[6DW 
I+8WR([SHULPHQWICD)LJXUH

IHU

EXP1

GET DATADATAIHU Handling

End



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3DJHRI
71

72

73
November 16, 2015
Version 1.00

1

SPI1 NSSSPI1 SCKSPI1 MISOSPI1 MOSI
Serial 2 RXD
Serial 2 TXDExperiment Enable 1
Experiment Enable 2
Experiment Enable 3
Experiment Enable 4
Serial 1 RXD

Q
S
H

I²C1 SCL
I²C1 SDA
Serial 1 TXD
Solar Safe N
Alert Signal-Z Deploy Switch 1-Z Deploy Switch 2
I²C2 SCLTX PA Current
TX Temperature
Experiment 4 Thermistor

8
10
12
14
16
18
20
22
24

IHU RF Control

26

IHU PTT
RF TX Active

28
30

RX CD

32

RX Audio
Not Used2
4

6

RX Temperature
RSSI
IHU Audio Out
Not Used
RX Command Data 0
RX Command Data 1
RX Command Data 2
RX Command Data 3
RX Command Strobe

C
O
N
N
E
C
T
O
R

I²C2 SDA

34
36

Sensor Power38

TX Frequency Control+Z Thermistor

RX Frequency Control-Z Thermistor

40
42-Y Antenna Deploy+Z CIC44-Y Antenna Sensor-Z CIC+Y Antenna Sensor

Umbilical USBP

46
48

+Y Antenna Deploy

Umbilical USBM

50

Not Used

Umbilical Power Active

Not Used

Solar Power A

52
54

Solar Power B

56

Vbatt

Vbatt

BUS

3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
49
51
53
55

Vbatt

57
59

58

Vbatt

60

NOT
CONNECTEDNOT USEDCONNECTEDNOT IN USE

CONNECTEDIN USE

Connections

RF

UMBILICAL

PSU/BATTALL

EXPERIMENTSANTENNAS

SystemLEGEND

SPI1 NSS

Not Used

Alert Signal

TX PA Current
TX Temperature
Experiment 4 Thermistor

2
4

6

RX Temperature

8

RSSI
IHU Audio Out

IHUSPI1 SCKSPI1 MISOSPI1 MOSI
Serial RXD
Serial TXD

10
12Experiment Enable 1
Experiment Enable 2
Experiment Enable 3
Experiment Enable 4
Serial 1 RXD

Q
S
H

I²C1 SCL
I²C1 SDA

27
29
31
33

I²C2 SCL

14RX Command Data 0
RX Command Data 1

16
18

RX Command Data 2

20

RX Command Data 3
RX Command Strobe

I²C2 SDA

22
24

IHU RF Control

26

IHU PTT
RF TX Active

28
30

RX CD

32

RX Audio

34
36

Sensor Power38

TX Frequency Control
RX Frequency Control

40
42-Y Antenna Deploy

44-Y Antenna Sensor+Y Antenna Sensor
Umbilical USBP

November 16, 2015
Version 1.00

1
3
5
7
9
11
13
15
17
19
21
23
25

C
O
N
N
E
C
T
O
R

35
37
39
41
43
45
47
49
51

46
48

+Y Antenna Deploy

50

Umbilical USBM
53

74
52

Umbilical Power Active

54

55

56

Vbatt

57

Vbatt

Vbatt

59

58

Vbatt

60

NOT
CONNECTEDNOT USEDCONNECTEDNOT IN USE

CONNECTEDIN USE

Connections

RF

UMBILICAL

PSU/BATTALL

EXPERIMENTSANTENNAS

SystemLEGEND75
November 16, 2015
Version 1.00

1

2
4

PSU

3
5

6

7

8
9

10
11

12

13

14
15

16
17

18

Q
S
H

19
21
23
25
27
29
31

Solar Safe N
Alert Signal

33-Z Deploy Switch 1
35

37-Z Deploy Switch 2
I²C2 SCL

39

20
22
24

C
O
N
N
E
C
T
O
R

26
28
30
32
34
36
Sensor Power38

I²C2 SDA
41

43

40

+Z Thermistor

42-Z Thermistor
45-Y Antenna Deploy+Z CIC
47

44-Y Antenna Sensor-Z CIC+Y Antenna Sensor

49

46
48

+Y Antenna Deploy

50

51

52
53

55

54
Solar Power A

Solar Power B

Vbatt

57
59

56

Vbatt

Vbatt

58

Vbatt

60

NOT
CONNECTEDNOT USEDCONNECTEDNOT IN USE

CONNECTEDIN USE

Connections

RF

UMBILICAL

PSU/BATTALL

EXPERIMENTSANTENNAS

SystemLEGENDNovember 16, 2015
Version 1.00

1

2

BATT 1

3
5

4
6

7

76
8
9

10
11

12

13

14
15

16
17

18

Q
S
H

19
21
23
25
27
29
31

Solar Safe N
Alert Signal

33-Z Deploy Switch 1
35

37-Z Deploy Switch 2
I²C2 SCL

39

20
22
24

C
O
N
N
E
C
T
O
R

26
28
30
32
34
36
Sensor Power38

I²C2 SDA

40

41

42

43

44
45

46
47

49

48
Umbilical USBP

51

50

Umbilical USBM
53

55

52

Umbilical Power Active

54

Solar Power A

Solar Power B

Vbatt

57
59

56

Vbatt

Vbatt

58

Vbatt

60

NOT
CONNECTEDNOT USEDCONNECTEDNOT IN USE

CONNECTEDIN USE

Connections

RF

UMBILICAL

PSU/BATTALL

EXPERIMENTSANTENNAS

SystemLEGEND77
November 16, 2015
Version 1.00

2
4
6
RX Temperature

RF Receiver

1
3
5
7
9

8

RSSI
11

10
12

13

14
15

16
17

18

Q
S
H

19
21

20
22

23
25
27
29
31
33
35
37

24

C
O
N
N
E
C
T
O
R

26
28
RF TX Active

30
RX CD

32

RX Audio

34
36

Sensor Power

38

39

40
41

RX Frequency Control

42

43

44
45

46
47

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

NOT
CONNECTEDNOT USEDCONNECTEDNOT IN USE

CONNECTEDIN USE

Connections

RF

UMBILICAL

PSU/BATTALL

EXPERIMENTSANTENNAS

SystemLEGEND

TX PA Current

2

RF Xmtr

TX Temperature

November 16, 2015
Version 1.00

1
3
5

4
6

7

78
8
9

10
11

IHU Audio Out

12

13

14
15

16
17

Q
S
H

19
21

18
20
RX Command Data 3

23
25
27
29
31
33

-Z Deploy Switch 1
35-Z Deploy Switch 2

37

22
24

C
O
N
N
E
C
T
O
R

39

IHU RF Control

26

IHU PTT
RF TX Active

28
30

RX CD

32

RX Audio

34
36

Sensor Power38

TX Frequency Control
41

43

40
42

-Z Thermistor

44

45

46
47

-Z CIC

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

58

Vbatt

60

NOT
CONNECTEDNOT USEDCONNECTEDNOT IN USE

CONNECTEDIN USE

Connections

RF

UMBILICAL

PSU/BATTALL

EXPERIMENTSANTENNAS

SystemLEGEND

79

November 16, 2015
Version 1.00

52
51

50
49

46
45

44
43

40
39

16
15

14
13

10
9

8
7

BATT 2

56
55

2

1

58
57

4

3

6

5

12
11

18
17

26
25

20
19

28
27

22

Q
S
H
21

30
29

24
23

32
31

42
41

34
33

48
47

36
35

54
53

38

C
O
N
N
E
C
T
O
R
37

60
59

NOT
CONNECTEDNOT USEDCONNECTEDNOT IN USE

CONNECTEDIN USE

Connections

RF

UMBILICAL

PSU/BATTALL

EXPERIMENTSANTENNAS

SystemLEGENDNovember 16, 2015
Version 1.00

1

2

EXP 1

3
5

4
6

7

80
8
9

10
11

13

12
Experiment Enable 1

14

15

16
17

18

Q
S
H

19
21
23
25

I²C1 SCL
I²C1 SDA

27
29
31
33
35
37

20
22
24

C
O
N
N
E
C
T
O
R

26
28
30
32
34
36
38

39

40
41

42

43

44
45

46
47

48

49

50
51

52
53

54

55

56

Vbatt

57
59

Vbatt

Vbatt

Vbatt

58
60

NOT
CONNECTEDNOT USEDCONNECTEDNOT IN USE

CONNECTEDIN USE

Connections

RF

UMBILICAL

PSU/BATTALL

EXPERIMENTSANTENNAS

SystemLEGEND81

November 16, 2015
Version 1.00

52
51

50
49

46
45

44
43

40
39

16
15

14
13

10
9

8
7

EXP 2

56
55

2

1

58
57

4

3

6

5

12
11

18
17

26
25

20
19

28
27

22

Q
S
H
21

30
29

24
23

32
31

42
41

34
33

48
47

36
35

54
53

38

C
O
N
N
E
C
T
O
R
37

60
59

NOT
CONNECTEDNOT USEDCONNECTEDNOT IN USE

CONNECTEDIN USE

Connections

RF

UMBILICAL

PSU/BATTALL

EXPERIMENTSANTENNAS

SystemLEGEND

50
49

46
45

44
43

40
39

16
15

14
13

10
9

8
7

EXP 3

52
51

November 16, 2015
Version 1.00

56
55

2

1

58
57

4

3

6

5

12
11

18
17

26
25

20
19

28
27

22

Q
S
H
21

30
29

24
23

32
31

42
41

34
33

48
47

36
35

54
53

38

C
O
N
N
E
C
T
O
R
37

60
59

82
NOT
CONNECTEDNOT USEDCONNECTEDNOT IN USE

CONNECTEDIN USE

Connections

RF

UMBILICAL

PSU/BATTALL

EXPERIMENTSANTENNAS

SystemLEGEND83
November 16, 2015
Version 1.00

1Experiment 4 Thermistor

2

EXP4

3
5

4
6

7

8
9

10
11

12

13

14
15

16
17

18

Q
S
H

19
21

20
22

23
25
27
29
31
33
35
37

24

C
O
N
N
E
C
T
O
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26
28
30
32
34
36
Sensor Power

38

39

40
41

+Z Thermistor

42

43

44
45

+Z CIC

46

47

48

49

50
51

52
53

54

55

56
57

58
59

60

NOT
CONNECTEDNOT USEDCONNECTEDNOT IN USE

CONNECTEDIN USE

Connections

RF

UMBILICAL

PSU/BATTALL

EXPERIMENTSANTENNAS

SystemLEGEND84

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86

87

Goal:
 Determine Resolution of Camera at Perigee
in VGA (640x480 pixels) Mode.
 Determine Resolution of Camera at Perigee
in QVGA (320x240 pixels) Mode.

Assumptions: Flat Earth: When accounting for curve ofearth, resolution will decrease.

Given Data: Orbital Altitude = 450 km
 Calculation done for Perigee

88

VGA Image:

640 pixels

320 pixels

Camera to Measuring Tape
Distance (d): 26.75 inches

480 pixels

QVGA Image:240 pixels

89

320pixels, 2X = 7.5 in, X = 3.75 in

QVGA Image:

640 pixels, 2X = 9.25 in, X = 4.625 in

VGA Image:240 pixels
2Y = 5.625 in
Y = 2.8125 in

480 pixels
2Y = 6.9375 in
Y = 3.46875 in

d = 26.75 inߠுைோ

d = 26.75 inߠ௏ாோ்

d = 26.75 inߠுைோ

d = 26.75 in

ߠ௏ாோ்

͵Ǥ͹ͷ
ʹ͸Ǥ͹ͷ
ߠொ௏ீ஺ǡுைோ ൌ ͹ǤͻͺͲͳͳ ࣐݀݁݃ࡽࢂࡳ࡭ǡࡴࡻࡾ ൌ ૛ࣂࡽࢂࡳ࡭ǡࡴࡻࡾ ൌ ૚૞Ǥ ૢ૟૙ ࢊࢋࢍߠொ௏ீ஺ǡுைோ ൌ ିଵ

ߠொ௏ீ஺ǡ௏ாோ் ൌ ିଵ

ߠ௏ீ஺ǡுைோ ൌ ିଵʹǤͺͳʹͷ
ʹ͸Ǥ͹ͷߠொ௏ீ஺ǡ௏ாோ் ൌ ͸ǤͲͲʹͲͶ ࣐݀݁݃ࡽࢂࡳ࡭ǡࢂࡱࡾࢀ ൌ ૛ࣂࡽࢂࡳ࡭ǡࢂࡱࡾࢀ ൌ ૚૛Ǥ ૙૙૝ ࢊࢋࢍ͵ǤͶ͸ͺ͹ͷ
ʹ͸Ǥ͹ͷߠ௏ீ஺ǡ௏ாோ் ൌ ͹Ǥ͵ͺͺͶͺ ࣐݀݁݃ࢂࡳ࡭ǡࢂࡱࡾࢀ ൌ ૛ࣂࢂࡳ࡭ǡࢂࡱࡾࢀ ൌ ૚૝Ǥ ૠૠૠ ࢊࢋࢍߠ௏ீ஺ǡ௏ாோ் ൌ ିଵ

ͶǤ͸ʹͷ
ʹ͸Ǥ͹ͷ
ߠ௏ீ஺ǡுைோ ൌ ͻǤͺͲͻ͵ ࣐݀݁݃ࢂࡳ࡭ǡࡴࡻࡾ ൌ ૛ࣂࢂࡳ࡭ǡࡴࡻࡾ ൌ ૚ૢǤ ૟૚ૢ ࢊࢋࢍ

Y = 3.46875 in
X = 4.625 in
Y = 2.8125 in
X = 3.75 in

320pixels, 2X = 7.5 in

QVGA Image:

640 pixels, 2X = 9.25 in

VGA Image:240 pixels
2Y = 5.625 in

480 pixels
2Y = 6.9375 in

320 Pixels, 7.5 in

240 Pixels
5.625 in

640 Pixels, 9.25 in

480 Pixels
6.9375 inͶǤ͸ͺ͹ͷ
ʹ͸Ǥ͹ͷߠொ௏ீ஺ǡ஽ூ஺ீ ൌ ͻǤͻ͵ͻʹ ࣐݀݁݃ࡽࢂࡳ࡭Ǥࡰࡵ࡭ࡳ ൌ ૛ࣂࡽࢂࡳ࡭ǡࡰࡵ࡭ࡳ ൌ ૚ૢǤ ૡૠૢ ࢊࢋࢍߠொ௏ீ஺ǡ஽ூ஺ீ ൌ ିଵ

࣐ࢂࡳ࡭ߠ௏ீ஺ d=26.75 inͷǤ͹ͺͳʹͷʹ͸Ǥ͹ͷߠ௏ீ஺ǡ஽ூ஺ீ ൌ ͳʹǤͳͻͷ͵ ࣐݀݁݃ࢂࡳ࡭ǡࡰࡵ࡭ࡳ ൌ ૛ࣂࢂࡳ࡭ǡࡰࡵ࡭ࡳ ൌ ૛૝Ǥ ૜ૢ૚ ࢊࢋࢍߠ௏ீ஺ǡ஽ூ஺ீ ൌ ିଵ

࣐ࢂࡳ࡭ߠ௏ீ஺ d=26.75 in

11.5625 in

9.375 in90

91

450,000 [m]450,000 [m]߮ொ௏ீ஺ǡ௏ாோ் ൌ ͳʹǤͲͲͶ ݀݁݃߮ொ௏ீ஺

QVGA Image:߮௏ீ஺ǡ௏ாோ் ൌ ͳͶǤ͹͹͹ ݀݁݃߮௏ீ஺

VGA Image:

X

X

X

X

ܴ‫ܱܰܫܷܶܮܱܵܧ‬ொ௏ீ஺ǡ௏ாோ் ൌͻͶǡ͸ʹͷǤ͸ ݉؆ ૜ૢ૝Ǥ ૛ૠ૜ ࢓ൗ࢖࢏࢞ࢋ࢒
ʹͶͲ ‫ݏ݈݁ݔ݅݌‬߮ொ௏ீ஺ǡ௏ாோ்ൗʹ

CAM pixel res: 320 x 240 pixels
Vertical: ʹͶͲ ‫ݏ݈݁ݔ݅݌‬THUS:ܺ ൌ ͶͷͲǡͲͲͲ ሾ݉ሿ ‫ כ‬ൌ Ͷ͹ǡ͵ͳʹǤͺ ݉ʹܺ ൌ ͻͶǡ͸ʹͷǤ͸ ܴ݉‫ܱܰܫܷܶܮܱܵܧ‬௏ீ஺ǡ௏ாோ் ൌͳͳ͸ǡ͹Ͳ͸ ݉؆ ૛૝૜Ǥ ૚૜ૡ ࢓ൗ࢖࢏࢞ࢋ࢒ͶͺͲ ‫ݏ݈݁ݔ݅݌‬߮௏ீ஺ǡ௏ாோ்
ൗʹ

CAM pixel res: 640 x 480 pixels
Vertical: ͶͺͲ ‫ݏ݈݁ݔ݅݌‬THUS:ܺ ൌ ͶͷͲǡͲͲͲ ሾ݉ሿ ‫ כ‬ൌ ͷͺǡ͵ͷ͵ ݉ʹܺ ൌ ͳͳ͸ǡ͹Ͳ͸ ݉

92

450,000 [m]450,000 [m]߮ொ௏ீ஺ǡுைோ ൌ ͳͷǤͻ͸Ͳ ݀݁݃߮ொ௏ீ஺

QVGA Image:߮௏ீ஺ǡுைோ ൌ ͳͻǤ͸ͳͻ ݀݁݃߮௏ீ஺

VGA Image:

X

X

X

X

ܴ‫ܱܰܫܷܶܮܱܵܧ‬ொ௏ீ஺ǡுைோ ൌͳʹ͸ǡͳ͸͸ ݉؆ ૜ૢ૝Ǥ ૛ૠ૙ ࢓ൗ࢖࢏࢞ࢋ࢒
͵ʹͲ ‫ݏ݈݁ݔ݅݌‬߮ொ௏ீ஺ǡ஽ூ஺ீൗʹ

CAM pixel res: 320 x 240 pixels
Horizontal: ͵ʹͲ ‫ݏ݈݁ݔ݅݌‬THUS:ܺ ൌ ͶͷͲǡͲͲͲ ሾ݉ሿ ‫ כ‬ൌ ͸͵ǡͲͺ͵Ǥʹ ݉ʹܺ ൌ ͳʹ͸ǡͳ͸͸ ܴ݉‫ܱܰܫܷܶܮܱܵܧ‬௏ீ஺ǡுைோ ൌͳͳͷǡ͸ͳͳ ݉؆ ૛૝૜Ǥ ૚૝૛ ࢓ൗ࢖࢏࢞ࢋ࢒͸ͶͲ ‫ݏ݈݁ݔ݅݌‬߮௏ீ஺ǡ஽ூ஺ீ
ൗʹ

CAM pixel res: 640 x 480 pixels
Horizontal: ͸ͶͲ ‫ݏ݈݁ݔ݅݌‬THUS:ܺ ൌ ͶͷͲǡͲͲͲ ሾ݉ሿ ‫ כ‬ൌ ͹͹ǡͺͲͷǤ͵ ݉ʹܺ ൌ ͳͷͷǡ͸ͳͳ ݉

93

450,000 [m]450,000 [m]߮ொ௏ீ஺ǡ஽ூ஺ீ ൌ ͳͻǤͺ͹ͻ ݀݁݃߮ொ௏ீ஺

QVGA Image:߮௏ீ஺ǡ஽ூ஺ீ ൌ ʹͶǤ͵ͻͳ ݀݁݃߮௏ீ஺

VGA Image:

X

X

X

X

߮௏ீ஺ǡ஽ூ஺ீ
ൗʹ߮ொ௏ீ஺ǡ஽ூ஺ீൗʹ

CAM pixel res: 320 x 240 pixels
Diagonal: ͵ʹͲ ଶ ൅ ʹͶͲ ଶ ൌ ͶͲͲ ‫ݏ݈݁ݔ݅݌‬THUS:
ͳͷ͹ǡ͹ͳͷ ݉؆ ૜ૢ૝Ǥ ૛ૡ૟ ࢓ൗ࢖࢏࢞ࢋ࢒
ܴ‫ܱܰܫܷܶܮܱܵܧ‬ொ௏ீ஺ǡ஽ூ஺ீ ൌͶͲͲ ‫ݏ݈݁ݔ݅݌‬ܺ ൌ ͶͷͲǡͲͲͲ ሾ݉ሿ ‫ כ‬ൌ ͹ͺǡͺͷ͹Ǥ͵ ݉ʹܺ ൌ ͳͷ͹ǡ͹ͳͷ ݉

CAM pixel res: 640 x 480 pixels
Diagonal: ͸ͶͲ ଶ ൅ ͶͺͲ ଶ ൌ ͺͲͲ ‫ݏ݈݁ݔ݅݌‬THUS:
ͳͻͶǡͷͲͻ ݉؆ ૛૝૜Ǥ ૚૝૚ ࢓ൗ࢖࢏࢞ࢋ࢒
ܴ‫ܱܰܫܷܶܮܱܵܧ‬௏ீ஺ǡ஽ூ஺ீ ൌͺͲͲ ‫ݏ݈݁ݔ݅݌‬ܺ ൌ ͶͷͲǡͲͲͲ ሾ݉ሿ ‫ כ‬ൌ ͻ͹ǡʹͷ͸ǤͶ ݉ʹܺ ൌ ͳͻͶǡͷͳ͵ ݉94ܴ‫ܱܰܫܷܶܮܱܵܧ‬௏ீ஺ǡ஽ூ஺ீ ؆ ૛૝૜Ǥ ૚૝૚ ࢓ൗ࢖࢏࢞ࢋ࢒

ܴ‫ܱܰܫܷܶܮܱܵܧ‬௏ீ஺ǡுைோ ؆ ૛૝૜Ǥ ૚૝૛ ࢓ൗ࢖࢏࢞ࢋ࢒

ܴ‫ܱܰܫܷܶܮܱܵܧ‬ொ௏ீ஺ǡ஽ூ஺ீ ؆ ૜ૢ૝Ǥ ૛ૡ૟ ࢓ൗ࢖࢏࢞ࢋ࢒

ܴ‫ܱܰܫܷܶܮܱܵܧ‬ொ௏ீ஺ǡ௏ாோ் ؆ ૜ૢ૝Ǥ ૛ૠ૜ ࢓ൗ࢖࢏࢞ࢋ࢒
ܴ‫ܱܰܫܷܶܮܱܵܧ‬ொ௏ீ஺ǡுைோ ؆ ૜ૢ૝Ǥ ૛ૠ૙ ࢓ൗ࢖࢏࢞ࢋ࢒

ܴ‫ܱܰܫܷܶܮܱܵܧ‬௏ீ஺ǡ௏ாோ் ؆ ૛૝૜Ǥ ૚૜ૡ ࢓ൗ࢖࢏࢞ࢋ࢒

QVGA
࣐ࡽࢂࡳ࡭ǡࢂࡱࡾࢀ ൌ ૚૛Ǥ ૙૙૝ ࢊࢋࢍ࣐ࡽࢂࡳ࡭ǡࡴࡻࡾ ൌ ૚૞Ǥ ૢ૟૙ ࢊࢋࢍ࣐ࡽࢂࡳ࡭Ǥࡰࡵ࡭ࡳ ൌ ૚ૢǤ ૡૠૢ ࢊࢋࢍ

VGA࣐ࢂࡳ࡭ǡࢂࡱࡾࢀ ൌ ૚૝Ǥ ૠૠૠ ࢊࢋࢍ࣐ࢂࡳ࡭ǡࡴࡻࡾ ൌ ૚ૢǤ ૟૚ૢ ࢊࢋࢍ࣐ࢂࡳ࡭ǡࡰࡵ࡭ࡳ ൌ ૛૝Ǥ ૜ૢ૚ ࢊࢋࢍ

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TIME(r 5%)

FUNCTION|4
seconds| 20
seconds| 90
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seconds| 50
minutesBurn Resistor Activation
Burn Resistors RE-activation
Deployment Switch
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IHU Boot-Up/POST
Antenna/RF Initiation Delay
Beacon (Safe Mode) Duty
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Telemetry Period

OPERATIIONAL CONDITIONSTime allotted for the (activated) burn resistors’ initial melting of the
deployable antenna restrainers
Time allotted for the (RE-activated) burn resistors’ subsequentmelting of the deployable antenna restrainers
Delay time from deployment switch physical activation toelectronic activation report.
Time for the Internal Housekeeping Unit (IHU) to boot-up and run
Power On System Tests (POST)
Antenna deployment and transmission inhibit time after
dispenser launch
Elapsed time from end of beacon telemetry transmission to start| 2 minutes of next beacon transmission while in SAFE MODE
RF transmit carrier time after the uplink passband (aggregate)| 30
signal(s) no longer satisfy the threshold criteria.
seconds| 15
Sampling period for all telemetry parameters
seconds
Time after receipt of ENABLE TX command before transmitting a

ENABLE TX Confirm| 3 minutes telemetry beacon
If IHU-directed tasks do not report back within this time period, the| 10satellite will reset.
seconds

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Power1
Power2
Power3
Power4
REM1
REM2_RESETS

NONE
NONE
NONE
NONE
mW
mW
mW
mW
NONE
NONE

13 REM2_UPTIME

16 s

14 REM2_CORE_VOL
TAGE
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16 REM2_UPSETS

8 mV





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CONVERSION SHORT_NAME DESCRIPTION
27 Status
Status of the Vanderbilt
University Controller
1 Restarts
Number of restarts by the
Vanderbilt University
Controller
25 Uptime
Uptime of the Vanderbilt
University Controller
27 State
Vulcan Experiment 1 State
27 State
Vulcan Experiment 2 State
27 State
Vulcan Experiment 3 State
27 State
Vulcan Experiment 4 State
0 Power
Vulcan Experiment 1 Power
0 Power
Vulcan Experiment 2 Power
0 Power
Vulcan Experiment 3 Power
0 Power
Vulcan Experiment 4 Power
0 NONENONE
1 Resets
Number of times the REM2
Experiment has reset
25 Uptime
Uptime of the REM2
Experiment
25 Core Voltage
REM2 Core Voltage

32 s

1 SEU Livetime

REM2 SEU Livetime

16 NONE

1 Memory

Cumulative number of

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Errors17 REM3_RESETS

8 NONE

1 Resets

18 REM3_UPTIME

16 s

25 Uptime

19 REM3_CORE_VOL
TAGE
20 REM3_SEU_LIVETI
ME
21 REM3_UPSETS

8 mV

25 Core Voltage

memory upsets in REM2
Experiment
Number of times the REM3
Experiment has reset
Uptime of the REM3
Experiment
REM3 Core Voltage

32 s

1 SEU Livetime

REM3 SEU Livetime

16 NONE

1 Memory
Errors22 REM4_RESETS

8 NONE

1 Resets

23 REM4_UPTIME

16 s

25 Uptime

24 REM4_CORE_VOL
TAGE
25 REM4_SEU_LIVETIME
26 REM4_UPSETS

8 mV

25 Core Voltage

Cumulative number ofmemory upsets in REM3
Experiment
Number of times the REM4
Experiment has reset
Uptime of the REM4
Experiment
REM4 Core Voltage

32 s

1 SEU Livetime

REM4 SEU Livetime

16 NONE

1 Memory
ErrorsCumulative number ofmemory upsets in REM4
Experiment












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

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3DJHRI

121

122

Fox 1-E Linear Transponder Average Power Tracking
Marc Franco, N2UO – Dan Habecker, W9EQMay 2016

The distribution of this document is restricted by ITARFox 1-E is the first satellite of the Fox series to feature a linear transponder. The downlink will beon the 70 cm band. The preliminary design goals are as follows:
Frequency: 435.8 MHz (nominal).
Bandwidth: 30 KHz.
Output power: 250 mW.
IMD: -20 dBc.
Harmonics: meet FCC.
Supply voltage: satellite battery, nominal 3.6 V.
We have chosen the RFPA0133 integrated circuit made by Qorvo (formerly RFMD) using their
GaAs HBT process. This power amplifier provides more than 30 dB of gain. The output match isexternal, allowing for the use of low loss components. The power added efficiency of the PA is
greater than 60%.
Linear transponders can be reasonably efficient when operated as close to saturation as possible
while maintaining the required linearity. However, when relaying weak signals or the satellite’s
beacon, their efficiency will be severely degraded. This is true for any linear amplifier; since theload resistance 5/ is related to the supply voltage 9FF and the output power 3R by the following
equation,ܸܿܿ ଶܴ‫ ܮ‬ൌʹܲ‫݋‬

any decrease in output power will result in a load resistance that is higher than that for maximum
power, where the amplifier operates efficiently. One approach to maintain the efficiency high is
to adjust the Vcc according to the output power in order to maintain 5/ constant. This will
minimize the amount of energy wasted in heat. Three methods to control the Vcc are shown in
Fig. 1: fixed Vcc, envelope tracking, and average power tracking.

123

In the fixed Vcc case, the amount of wasted energy is very large. No matter what the output
power is, the Vcc is adjusted to provide the maximum peak power, and it is not varied when the
power is lowered. Envelope tracking (ET), on the other hand, does exactly the opposite: it adjusts
the Vcc following the envelope of the signal, so the Vcc value is optimum at all times. This issimilar to the HELAPS or Envelope Elimination and Restoration methods used in past satellites.
The advantage of ET over EER is that it is simpler to implement and it is easier to achieve good
linearity. However, it takes a significant amount of energy to implement ET; there is a minimum
amount of current that needs to be drawn, no matter what the power amplifier power is, for theenvelope processing. In the case of a large amplifier, let’s say, above 5 W, the current needed to
implement ET is negligible, but at much lower RF power levels, the complexity and current
needed are hard to justify.
Another way to improve the efficiency of a power amplifier when operated at a significant backoff level is to use Average Power Tracking (APT). In this case, the value of the Vcc does not follow
the instantaneous amplitude of the envelope, but it follows its average value. The complexity
required in the modulator is a fraction of what is needed for ET, since now the Vcc envelope
frequency is much lower. Although the efficiency achieved with this method is not as high as withET, it is very convenient for small power amplifiers since the overhead current needed is much
lower than with ET.

Fixed

WastedEnvelope

WastedAPT

WastedFig. 1 – Time domain waveforms showing wasted power in fixed Vcc, average power tracking
and envelope tracking
124

In APT, the output of the power amplifier is sampled and applied to a peak power detector. The
output of the detector drives a high efficiency dc to dc converter that reduces the Vcc applied to
the PA directly proportionally to the time average of the peak output power. Ideally, the peakdetector should be placed at the input of the amplifier, but since the gain of this PA is not affectedsignificantly by the change in Vcc value, the detector can be placed at the output without causing
any instability.
Fig. 2 shows the schematic diagram of a practical implementation of the APT method. The
detector is a Linear Technology LTC5533, and the dc to dc converter is a Linear Technology
LTC1772. The Vcc of both stages in the RFPA0133 is controlled by the dc to dc converter.
The peak/hold function is implemented by adding some capacitance to ground after diode D1(not shown in the schematic). The time constant should be found experimentally using real SSB
and CW signals in the passband, but we have determined that between 1 to 2 seconds issatisfactory.
The current savings of the APT method can be seen in Fig. 3. Here, the current drawn by the
amplifier is plotted both with the APT system on or by simply applying a fixed Vcc to the amplifier.
The difference is quite significant at low power levels. In fact, if the satellite is to transmit only
the beacon, the current needed will be minimized. Implementing a “squelch” type circuit for
weak SSB and CW signals is not straightforward, as it is on FM.
The peak power detector used for the APT control can also be used for telemetry and to
implement an automatic gain control in the transponder. The total current drawn by the amplifierbiasing and power control circuit is 14 mA at 2.9 V.

Fig. 2 – Schematic of the Average Power Tracking125PA current vs. output power
200
180
160

Current (mA)

140

120
100

APT
Fixed Vcc

80
60
40
20
0
10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

Output Power (dBm)

Fig. 3 – Measured current draw of the power amplifier using APT or a fixed Vcc

The linearity of the amplifier is maintained at all voltages. As an example, the measured two-tone
spectrum at 10 dBm average power is shown in Fig. 4, whereas the two-tone spectrum at 23.7
dBm is shown in Fig. 5. Fig. 6 shows the 12-tone spectrum at 21.8 dBm total average power.

Fig. 4 – Measured two-tone spectrum at 21.8 dBm using APT
126

Fig. 5 – Measured two-tone spectrum at 23.7 dBm using APT

Fig. 6 – Measured twelve-tone spectrum spread out 30 KHz at 21.8 dBm using APT

127

128

129

D

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8/31/2016
C:\Users\..\Mixers and IF.SchDoc

Number

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6
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5
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Date:
File:

A

2

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130

FOX1E 1200 BPS BPSK modulator
John Klingelhoeffer, WB4LNM
Current revision: 27 August 2016

Introduction: The AMSAT FOX1E has been discussed as providing a 1200 BPS
BPSK downlink telemetry channel with a carrier outside of the user transponder
bandwidth. This would increase the bandwidth of the telemetry downlink
bandwidth compared with FOX1A-D, providing for a higher speed continuous
scientific data downlink, and making the satellite compatible with legacy AMSAT
telemetry downlink ground stations.
Discussion of the generation of this signal has previously been mentioned both as
firmware-based in the IHU and hardware-based in the transponder transmitter.
This document will address the later generation method ŽŶůǇ. This document
proposes an approach to generate BPSK that requires significantly less system
power, which is critical on small satellites. This is a concept document and is not adetailed design which is left to the AMSAT volunteer.

Requirements: The FOX1E transponder requires an approximately 45 MHz, lowlevel, 1200 BPS BPSK signal that can be combined into the transponder after user
bandwidth filtering and prior to up-conversion to 70 cm.

This document contains Technical Data whose export is restricted by the Arms Export Control Act (Title 22,
U.S.C., Sec 2751, et seq.). Violations of these export laws are subject to severe criminal penalties.

131

Approach: The hardware modulator subsystem proposed consists of two main
blocks, a carrier generator and the BPSK modulator itself.
The carrier generator would be a conventional, third-overtone, Colpitts crystal
oscillator. The oscillator may or may not be temperature-compensateddepending upon the desire to stabilize the frequency over long periods of time. In
the short term, after mixing with the up-converter local oscillator and amplified,
this signals frequency drift will be overwhelmingly dominated by short-term
Doppler shift which will be many orders of magnitude more than the long-term
temperature-induced drift. The continuous carrier wave output of this oscillator
is at a frequency close to the 45 MHz center frequency of the linear transponderIF, but outside the user passband.
The second block of the BPSK function is the modulator itself. What is proposed
herein is to use a quadruple analog switch instead of the more traditional double
balanced mixer. This minimizes the interfacing drive needs from the NRZ data
stream control input and therefore power. It allows the BPSK stream to begenerated with much lower power levels than traditional methods.
Quad bilateral analog switches (QBS) have progressed in performance significantly
since the days of the original CD4066, which was only functional to several
megahertz at best. In this instance, the switch proposed for this application is the
Texas Instruments TS112A44513DR:
http://www.ti.com/lit/ds/symlink/ts12a44514.pdf.
This IC has a 530 MHz high frequency cutoff at 5V operation, although it isoperable down to 2.7 Volts. There may be better quad analog switches available
for this specific application – no extensive survey was made. A morecomprehensive search by the AMSAT detail designer is recommended during
detail design.
The input and output signal processing to the quad bilateral analog switch bybaluns allows the ~45 MHz signal to be split and combined in-phase and out ofThis page contains ITAR Restricted Data.

132

phase 180 degrees. One such balun is the Pulse Electronics CX2074NL unit,
although as with the QBS, other devices are available.
http://www.digikey.com/product-detail/en/pulse-electronicscorporation/CX2074NL/553-1655-ND/2265447
This combination of parts is shown in the block diagrams on the following pages
to help visualize the action of the modulator. For this discussion, the four
switches of the QBS are designated as switches A,B,C and D.
The control signal for the QBS is the 1200 BPS NRZ telemetry output stream of the
IHU. This is a CMOS level digital signal. The non-inverted version of the control
signal comes directly from the IHU, while an inverted version of the same signal is
produced by the inverter shown in the diagram. The inverted and not-inverted
signals each control two of the switches at a time, leaving the other two in the
opposite state.

This page contains ITAR Restricted Data.

133

In the diagram shown, there are two states for the QBS IC; one is with the NRZ
input signal in the logic zero state and one for the logic one state. In one state,switches A and C will be closed and B and D open, and in the other state A and C
will be open and B and D will be closed.
As a visual aid, if the telemetry NRZ output of the IHU is in the “one” state, logic
high, switches A and C close and B and D remain open:

This allows the zero phase output pin of the input balun to be connected to thezero degree phase input pin on the output balun via switch A. Simultaneously, it
connects the 180 degree output pin of the input balun to be connected to the 180
degree input pin on the output balun. In this state, the output RF carrier is inphase with the input RF carrier.

This page contains ITAR Restricted Data.

134

If the NRZ telemetry output of the IHU changes to the zero logic state, thenswitches B and D close, and A and C open, resulting in the following signal path:

In this state, the zero phase output pin from the input balun is connected to the
180 degree input pin on the output balun via switch B. Simultaneously, the 180
degree output pin on the input balun is connected to the zero degree input pin on
the output balun via switch D. In this state, the RF output signal is 180 degrees
out of phase with the RF input signal.

This page contains ITAR Restricted Data.

135

The relative change in output phase relative to the input signal impresses the
BPSK modulation on the input carrier. In the ‘ONE’ state, the output is in phasewith the input, and in the ‘ZERO’ state, the output is 180 degrees out of phasewith the input carrier. This resulting ~45 MHz BPSK modulated carrier can thenbe combined with the user transponder bandwidth, mixed up to 70 cm andfurther amplified by the power amplifier.
The output of this BPSK modulator would be united with the user signals with theaid of an RF combiner. The RF combiner could be in the form of a directional
coupler or a 3 dB, zero degree hybrid, whichever is more appropriate to matchother constraints on signal level and PCB real estate area.
The keying of the BPSK signal is not synchronous with the carrier in this approach.
Synchronicity is not critical when the carrier frequency is several orders ofmagnitude higher than the keying rate, which it is in this case. The ratio of keyedto carrier frequency in this instance is approximately 37,500 to 1.

Summary: This approach is proposed because traditional high level double
balanced diode mixers require significant power to operate due to high current
level signals to make the diodes conduct to switch the RF signal. With the QBS,
the signal drive levels can be quite low which is more desirable for low powersatellite circuitry.

This page contains ITAR Restricted Data.

136

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