# Presentation: 514182

## Section 19

_***Section 19***_
***Command & Data Handling (C&DH)***

*** ******. . . Steve Schumacher***
*Swales Aerospace, Inc.*

*** ******. . . Philip Luers***
*NASA/GSFC*

## ACDS Contents

***ACDS Contents***

***Overview of ACDS Design***
***Summary of Requirements***
***Single-Point Failures***
***Test and Verification Program***
***Technical Review History***
***Operating Time***
***Configuration Changes***
***Special Topic -- Timekeeping***

## ACDS Box Block Diagram

- C&DH

- Power System Electronics (PSE)

- 1773 Fiber Optic Data Bus

- Inertial Reference Unit (IRU)

- Umbilical and APTS Racks

- Coarse Sun Sensors (4x)

- Three-Axis Magnetometer (TAM)

- Autonomous Star Tracker (AST)

- Reaction Wheels (RWA, 3x)

- Magnetic Torquer Bars (MTB, 3x)

- Reaction Control System (RCS)

- Pulsed Plasma Thruster (PPT)

- Solar Array Drive (SADA/ECU)

- Solar Array (Dep HTR and pot)

- GPS Receiver (GPS)

- HOP Actuators (HOPS)

- Light Flex Solar Array (LFSA)

- WARP Science Data Recorder

- S-band Transponder

- Spacecraft Heaters (Bays 1-6)

- Spacecraft Temperature Sensors

- Solar Array (Hinge pots and Htr)

- Solar Array Drive Temperature

***ACDS Box Block Diagram***

## C&DH Overview 

***C&DH Overview ***

***C&DH Boards:  C&DH LVPC, MV Processor, H/K RSN, Comm RSN***
***C&DH LVPC Board***
*Unswitched: +5V, +15V, and -15V to MV Processor and H/K RSN*
*Switched: 28V to GPS, Bay Heaters, and HOP Deployment*
*Unswitched: 28V, +5V, +15V, and -15V to LFSA via H/K RSN*
***MV Flight Computer***
*S/C processor runs ACS and C&DH flight software*
*AS1773 Spacecraft Bus Controller*
*SSR stores up to 1.8G bits of spacecraft housekeeping data*
*Up to 32 Mbytes additional memory available for program/command storage*
*Serial output to Comm RSN for data downlink*
*Input multiplexer to send science data to Comm RSN in backup mode*
***H/K RSN Board***
*Embedded UT69R000 controller and AS1773 interface as remote terminal*
*Controls C&DH LVPC via backplane*
*Interfaces to GPS, S/A, LFSA and S/C for telemetry collection*
*Interface to separation switches*
*Provides WARP pulse command*
***Comm RSN Board***
*Embedded UT69R000 controller and AS1773 interface as remote terminal*
*Provides interface with S-band transponder*
*Unswitched 28V from PSE Output Module#1*

## C&DH Block Diagram

**C&DH LVPC**

**HK RSN**

**Surv. Htrs**

**Comm RSN**

- RSN Backplane Control with +5V,  ±15V, and +28V Power

**LFSA**

**PSE**

**GPS**

**HOPS**

**Separation**

**Thermistors**

**Array Pots**

**WARP**

**Comm**

**ACE**

## Mongoose V Flight Computer Requirements Met 

***Mongoose V Flight Computer Requirements Met ***

***Perform 1773 bus controller functionality***
***Distribute spacecraft commands via 1773 ***
***Receive and store all spacecraft housekeeping telemetry***
***Perform housekeeping telemetry processing for fixed frame format***
***Downlink housekeeping data to Comm RSN via high-speed RS-422 link with no gaps in between downlink frames***
***Perform ACS flight software calculations***
***Use real-time operating system***
***Perform spacecraft time calculations***
***Distribute spacecraft time via 1773 bus***
***Process & issue X-band phased array antenna pointing commands via 1773***
***Downlink real-time housekeeping data to Comm RSN via 1773 interface during ground station contact***
***In the event the X-band phased array antenna is not functional, the Mongoose V Flight Computer will multiplex science data to Comm RSN***

## Housekeeping RSN Card Electrical Requirements Met

***Housekeeping RSN Card Electrical Requirements Met***

***Control and process spacecraft thermistors***
***Control solar array deployment***
***Process solar array hinge status***
***Control flexible solar array deployment***
***Control & process flexible solar array housekeeping telemetry***
***Process separation indicator status***
***Distribute housekeeping packets to MV via 1773 interface***
***Receive 1pps from GPS via RS-422 interface***
***Receive & process GPS telemetry via RS-422 interface***
***Control C&DH LVPC switched services via backplane***

## C&DH LVPC Requirements Met

***C&DH LVPC Requirements Met***

***Draw +28 VDC Power from PSE Output Module #1 ***
***Provide unswitched +5V, +15V and -15V power to Housekeeping RSN and Mongoose V ***
***Provide unswitched +28 VDC to H/K RSN for LFSA deployment***
***Provide switched +28 VDC, 1-amp services ***
***Control LVPC switched services via RSN backplane***
***Provide current, temp and status telemetry***

## C&DH Interfaces

## Attitude Control Electronics Overview

***Four ACE Boards: ACE RSN, ACE I/O, Propulsion I/O, ACE LVPC ***
***ACE RSN***
*Embedded UT69R00 controller and 1773 interface.*
*Backplane I/O interface and control of other 3 ACE boards.*
*Interfaces to ACS subsystems: TAM, CSS, Reaction Wheels.*
***ACE I/O***
*Interfaces to IRU, MTB’s, PPT, AST, SADE/ECU.*
***Prop I/O***
*Controls, Heaters, and Telemetry interface to tank, lines, valves, and thrusters.*
***ACE LVPC Board***
*Provides +5V, *_*+*_*15V, and +28V power to ACE half of ACDS box*
*Provides switched power to IRU, AST, TAM, MTB, Latch Valve, and Heaters*

## ACE Block Diagram

**ACE LVPC**

**ACE RSN**

**IRU**

**CSS (4x)**

**Magnetic Torquer Bars**

**1773 to MV**

**+28 VDC from PSE OPM**
**(10-A switched service)**

**UART to GSE**

**SADE/ECU**

**RW**

**RW**

**RW**

**PROP I/O**

**PROP**** (Tank, Valves,                       CB Heaters, Thrusters)**

**AST**

**TAM Electronics**

**PPT**** (Pulsed Plasma                       Thruster)**

**+28 VDC from PSE OPM**
**(10-A switched service to**
** ****CB Heaters, Hydrazine **
**Thrusters, and PPT.)**

- RSN Backplane Control with +5V,  ±15V, and +28V Power

**SAD**

**TAM Head**

## ACE Functional Requirements

***ACE Functional Requirements***

***1773 Remote Terminal bus I/F***
***Power Distribution for ACS boards, sensors, actuators and heaters***
***Command and Data interface to:***
***Coarse Sun Sensors (CSS)***
***Three Axis Magnetometer (TAM)***
***Inertial Reference Unit (IRU)***
***Reaction Wheel Assy’s (RWA’s)***
***Magnetic Torquer Bars (MTB)***
***Autonomous Star Tracker (AST)***
***Solar Array Drive  Electronics and Control Unit (SADA/ECU)***
***RCS Valves, Thrusters, CB Heaters, Lines, and Tank***
***Pulsed Plasma Thruster***

## ACDS Test and Verification Program

***ACDS Test and Verification Program***

## Verification Matrix

**19 - **

## ACDS Problem Reporting (1/2)

***ACDS Problem Reporting (1/2)***

***11 PRs have been opened since 10/1/99, all are closed***
***1 Critical PR***
***Flight Software limitation***
*WOA 825-20-2 False command. Ingest error reported by ACDS immediately after sending warm restart command.  Use as-is, added to constraint manual.*
***10 Non-critical PRs***
***4 Procedural Errors***
*WOA 684-20-3 Misunderstanding of how MV HS Warm Restart Counter operates.*
*WOA 684-20-18 Misunderstanding of how FDC Violation Counter operates.*
*WOA 723-20-15 Commands to enable memory scrubbing left out of procedure.  Procedure was modified.*
*WOA 790-30-2 EFF software patch was loaded, checksumming was enabled and a warm start occurred, due to new code with old checksum.  Procedure was modified.*

## ACDS Problem Reporting (2/2)

***ACDS Problem Reporting (2/2)***

***2 Flight Software Problems***
*WOA 682-20-1 loaded new X-band RSN A/D code without loading new FDC trip points.  Next load of X-band RSN code also loaded new FDC trip points.*
*WOA 767-20-2 HKRSN warm restart did not preserve run-time counters.  Fixed in next HKRSN sofware load.*
***1 Ground Software Problem***
*WOA 723-20-6 FEDS software sent bogus telemetry values through even with sequence gaps caused by drop-out.  Fixed in next release of FSDecode.*
***2 Ground Hardware Limitations***
*WOA 816-20-2 Timing GSE termination resistor made Star Tracker sync pulse too small in amplitude to measure.  Was already verified during earlier testing.*
*WOA 797-70-2 Bus Buster was run with minimal system traffic, so fewer than expected retries were observed.  Retest during CPT showed expected results.*
***1 Personnel Communication Issue***
*WOA 818-20-2 MOC issued commands when not enabled for commanding.  MOC and I&T were encouraged to communicate more openly and clearly.*

## ACDS Trending

***ACDS Trending***

***Thermal Vacuum Trending Effort***
***4 voltages, 4 currents and 4 temperatures recorded every 5 minutes throughout 14 days of thermal vacuum for a total of 98,730 telemetry points recorded***
***No correlation found between voltages and temperature***
***No correlation found between currents and temperature ***

## ACDS Reviews

***ACDS Reviews***

***Technical (Peer) Reviews***
***CDR Peer Review June 1998***
***Box-level Reviews***
***Manufacturing Readiness Review Fall 97***
***Integration Readiness Review April 98***
***Pre-ship Readiness Review Nov 98***

## ACDS Operating Time

***ACDS Operating Time***

***Prior to delivery to SAI, 400 hours***
***From Beginning of S/C Environmental Test on 7/31/99 to 3/13/00, operating time 1813 hours***
***From Beginning of S/C Integration on 3/3/99 to 3/13/00, operating time 2820 hours***
***Projected minimum operating time between now and 5/27/00 ship to VAFB 274 hours***
***Total projected operating time by shipment: 400 + 2820 + 274 = 3494 hours***

## ACDS Configuration Changes

***ACDS Configuration Changes***

***No changes made to ACDS hardware. However, several changes have been made to external interfaces that have been test verified ***
***Hardware***
*Fusing of all C&DH LVPC services (see Special Topic)*
*LFSA power interface logic (+5, -15V, +15V) changed to accept unregulated 28V input (see Special Topic)*
***Software***
*Deployment code upgrades to HK RSN*
*Simplified TSM / RTS system*
*Improvement of timing software in HKRSN, Mongoose V, and Comm RSN*
*Other minor ones *

## ACDS Summary

***ACDS Summary***

***The ACDS is ready for launch, all residual risk is acceptable***
***Only open issue (Reference Open PR 829-30-2 & 30-3) is Ground Station PTP reliably time-tagging downlink data for time correlation functions (mentioned in Special Topic)***

## Special Topic:

***Timing Update Issues***

*** ******. . . Harry Culver***
*EO-1 C&DH Systems Lead*

## Special Topic -- Timekeeping

***In September, AETD (Code 561) was asked to verify the EO-1 on-board timing***
***Solved Problems:***
***When GPS was ON, spacecraft time was randomly changing with a maximum increment of 2 seconds due to incorrect UART configuration***
*Fixed with a software change to the H/K RSN*
***Leap seconds were not accounted for consistently on the spacecraft***
*All subsystems are handling leap seconds in an understood and documented manner*
***Subsequently, determined that the H/K RSN was not time tagging the GPS pulse properly ***
*Fixed with another software change to the H/K RSN and the Comm RSN*
***Random changing of exactly 1 second ***
*Fixed with another software change to the H/K RSN*
***Verified proper operation of S/C timekeeping 12/99***

## Special Topic:

***Timing Without GPS***

*** ******. . . Harry Culver***
*EO-1 C&DH Systems Lead*

## Special Topic -- Timekeeping

***Special Topic -- Timekeeping***

***Findings with solutions:***
***When GPS is OFF, the spacecraft time drifts at 10-15 microseconds / second which would exceed the 10 millisecond spec in about 10-15 minutes***
*Measured drift vs. temperature during Observatory Level Thermal/Vacuum Test, showed very high degree of correlation*
*Verified proper operation of Flight Software Drift Compensation Feature*
***Unsolved Problems***
***Timing correlation using the Ground Station Hardware has not been yet verified to meet specifications***
*Consistent results have not yet been achieved*
*Problems are mainly of a procedural nature*
*Retest scheduled for 3/21/00*