**[Section 2]{.smallcaps}**

**Table of Contents**

2\. THE HITCHHIKER CARRIER SYSTEM 2-[2](#the-hitchhiker-carrier-system)

2.1 Mechanical Support Systems 2-[3](#mechanical-support-systems)

2.1.1 HH Canister 2-[10](#hh-canister)

2.1.2 Plate Mounting 2-[24](#plate-mounting)

2.1.3 Direct Mounting of Experiment Package
2-[26](#direct-mounting-of-experiment-package)

2.1.4 HH-C Structure 2-[26](#hh-c-structure)

2.1.5 HH Side Mounting Plates 2-[36](#hh-side-mounting-plates)

2.2 Thermal Considerations 2-[39](#thermal-considerations)

2.2.1 Thermal Design Requirements 2-[39](#thermal-design-requirements)

2.2.2 Thermal Safety Requirements 2-[40](#thermal-safety-requirements)

2.2.3 Flammability Requirements for MLI Construction
2-[40](#flammability-requirements-for-mli-construction)

2.2.4 Thermal System Design for a HH Canister
2-[40](#thermal-system-design-for-a-hh-canister)

2.2.5 Thermal System Design for Pallet and Plate Mounting
2-[47](#thermal-system-design-for-pallet-and-plate-mounting)

2.2.6 Thermistors 2-[47](#thermistors)

2.3 Electrical/Power Support Systems
2-[50](#electricalpower-support-systems)

2.3.1 Electrical Design 2-[50](#electrical-design)

2.3.2 Power Characteristics 2-[50](#power-characteristics)

2.3.3 DC Power Ripple and Transient Limits (For Payload Main Circuit
Only)
2-[59](#dc-power-ripple-and-transient-limits-for-payload-main-circuit-only)

2.3.4 Thermal Power Characteristics
2-[63](#thermal-power-characteristics)

2.3.5 Signal Characteristics 2-[63](#signal-characteristics)

2.3.6 Standard Connectors for Customers
2-[63](#standard-connectors-for-customers)

2.3.7 Shield Grounding 2-[63](#shield-grounding)

2.4 Command And Communication Support System
2-[66](#command-and-communication-support-system)

2.4.1 Transparent Data System 2-[66](#transparent-data-system)

2.4.2 Bi-Level Command System 2-[71](#bi-level-command-system)

2.4.3 Asynchronous Uplink 2-[74](#asynchronous-uplink)

2.4.4 Asynchronous Downlink 2-[80](#asynchronous-downlink)

2.4.5 Medium-Rate Ku-Band Downlink 2-[82](#medium-rate-ku-band-downlink)

2.4.6 Analog Data -2-[87](#analog-data)

2.4.7 Temperature Data 2-[89](#temperature-data)

2.4.8 Inter-Range Instrumentation Group, Type B (IRIG-B) MET Signal
2-[89](#inter-range-instrumentation-group-type-b-irig-b-met-signal)

2.4.9 ACCESS/CGSE Interface 2-[92](#accesscgse-interface)

2.4.10 Crew Control 2-[111](#__RefHeading___Toc456763558)

2.4.11 Undedicated Connections in Standard Interface
2-[111](#undedicated-connections-in-standard-interface)

2.4.12 Orbiter CCTV Interface 2-[116](#orbiter-cctv-interface)

2.4.13 Hitchhiker Video Interface Unit
2-[116](#hitchhiker-video-interface-unit)

2.5 Hitchhiker-JR (HH-J) 2-[116](#hitchhiker-jr-hh-j)

2.5.1 Hitchhiker-JR Overview 2-[116](#hitchhiker-jr-overview)

2.5.2 Hitchhiker-J Electrical Interfaces
2-[119](#hitchhiker-j-electrical-interfaces)

2.6 Hitchhiker Ejection Capabilities Specification
2-[125](#hitchhiker-ejection-capabilities-specification)

**List of Figures**

Figure 2.1 Hitchhiker-S Carrier Components
[4](#__RefHeading___Toc457875841)

Figure 2.2 Hitchhiker-s Available Sidewall Mounting Locations
[5](#__RefHeading___Toc457875842)

Figure 2.3 Hitchhiker-S Typical Structural Configuration
[6](#__RefHeading___Toc457875843)

Figure 2.4 Hitchhiker-S Payload Mounting Concept (Sideview)
[7](#__RefHeading___Toc457875844)

Figure 2.5 Orbiter Coordinate System [8](#__RefHeading___Toc457875845)

Figure 2.6 Maximum Payload Static and Dynamic Envelopes
[9](#__RefHeading___Toc457875846)

Figure 2.7 Hitchhiker Sealed Canister [11](#__RefHeading___Toc457875847)

Figure 2.8 Hitchhiker Motorized Door Canister
[12](#__RefHeading___Toc457875848)

Figure 2.9 Hitchhiker canister [13](#__RefHeading___Toc457875849)

Figure 2.10 Hitchhiker-S Canister Mounting to Orbiter
[14](#__RefHeading___Toc457875850)

Figure 2.11 Hitchhiker Sealed Canister (Upper End Plate)
[16](#__RefHeading___Toc457875851)

Figure 2.12 Hitchhiker Sealed Canister -- Battery Vent Turret Interface
[17](#__RefHeading___Toc457875852)

Figure 2.13 Opening Lid Canister -- Experiment Mounting Plate
[20](#__RefHeading___Toc457875853)

Figure 2.14 Canister CG Envelope-Adapter Beam or Bridge Mounting
[21](#__RefHeading___Toc457875854)

Figure 2.15 Hitchhiker Motorized Door Canister -- Battery Vent Assembly
[22](#__RefHeading___Toc457875855)

Figure 2.16 Bumper Design Example [23](#__RefHeading___Toc457875856)

Figure 2.17 Hitchhiker-S Experiment Mounting Plate
[25](#__RefHeading___Toc457875857)

Figure 2.18 Adapter Beam Mounting Interfaces
[27](#__RefHeading___Toc457875858)

Figure 2.19 Hitchhiker-C Payload [28](#__RefHeading___Toc457875859)

Figure 2.20 HHBA Upper Structure on Shipping Dolly
[29](#__RefHeading___Toc457875860)

Figure 2.21 Hitchhiker-C Canister Locations
[31](#__RefHeading___Toc457875861)

Figure 2.22 Hitchhiker-C Canister and Mounting Plates
[32](#__RefHeading___Toc457875862)

Figure 2.23 Hitchhiker-C Canister [33](#__RefHeading___Toc457875863)

Figure 2.24 Hitchhiker-C Mounting Plate Locations
[34](#__RefHeading___Toc457875864)

Figure 2.25 Hitchhiker-C Mounting Plate
[35](#__RefHeading___Toc457875865)

Figure 2.26 CG Envelope & Positions [37](#__RefHeading___Toc457875866)

Figure 2.27 Hitchhiker-C Experiment Mounting Interface
[38](#__RefHeading___Toc457875867)

Figure 2.28 Fully Insulated Canister (Option1)
[42](#__RefHeading___Toc457875868)

Figure 2.29 Typical Orbital Thermal Attitudes
[43](#__RefHeading___Toc457875869)

Figure 2.30 Insulated Canister without Insulated Endcap (Option 2)
[44](#__RefHeading___Toc457875870)

Figure 2.31 Uninsulated Canister (Option 3)
[45](#__RefHeading___Toc457875871)

Figure 2.32 YSI Precision Thermistor [48](#__RefHeading___Toc457875872)

Figure 2.33 Thermistor Interface To Carrier
[49](#__RefHeading___Toc457875873)

Figure 2.34 Hitchhiker Standard Interface Cables
[51](#__RefHeading___Toc457875874)

Figure 2.35 Hitchhiker Standard Interface Cables
[54](#__RefHeading___Toc457875875)

Figure 2.36 Hitchhiker Motorized Door Canister
[55](#__RefHeading___Toc457875876)

Figure 2.37 Customer Power Interface [61](#__RefHeading___Toc457875877)

Figure 2.38 Hitchhiker Avionics Unit -- Power Distribution
[62](#__RefHeading___Toc457875878)

Figure 2.39 Digital Signal Shield [64](#__RefHeading___Toc457875879)

Figure 2.40 Shield Grounding of Logic Level and Analog Signals
[64](#__RefHeading___Toc457875880)

Figure 2.41 Shield Grounding of Power Line
[64](#__RefHeading___Toc457875881)

Figure 2.42 Double Shielding Significantly Varying Current and Voltage
Lines [65](#__RefHeading___Toc457875882)

Figure 2.43 Hitchhiker Transparent Data System
[66](#__RefHeading___Toc457875883)

Figure 2.44 Hitchhiker Command Flow [67](#__RefHeading___Toc457875884)

Figure 2.45 Hitchhiker Low Rate Data Flow
[68](#__RefHeading___Toc457875885)

Figure 2.46 Hitchhiker Medium Rate Data Flow
[69](#__RefHeading___Toc457875886)

Figure 2.47 Hitchhiker Signal Port to Customer Interface
[70](#__RefHeading___Toc457875887)

Figure 2.48 Customer Bi-Level Command Interface
[71](#__RefHeading___Toc457875888)

Figure 2.49 Customer Message Format for 28 Volt Bi-Level Commands
[72](#__RefHeading___Toc457875889)

Figure 2.50 Customer Message Format for 28 Volt Pulse Commands
2-[73](#__RefHeading___Toc457875890)

Figure 2.51 Customer Asynchronous Message Format -- General
2-[75](#__RefHeading___Toc457875891)

Figure 2.52 Customer Format for Asynchronous Commands
2-[76](#__RefHeading___Toc457875892)

Figure 2.53 Customer Message For MET
2-[77](#__RefHeading___Toc457875893)

Figure 2.54 Customer Message Format for Synchronized MET
2-[78](#__RefHeading___Toc457875894)

Figure 2.55 Customer Asynchronous RD Interface
2-[79](#__RefHeading___Toc457875895)

Figure 2.56 Customer Asynchronous SD Interface
2-[81](#__RefHeading___Toc457875896)

Figure 2.57 Medium Rate Customer Interface
2-[84](#__RefHeading___Toc457875897)

Figure 2.58 Medium Rate Customer Data
2-[85](#__RefHeading___Toc457875898)

Figure 2.59 Medium Rate Customer Clock
2-[86](#__RefHeading___Toc457875899)

Figure 2.60 Customer Analog Data Interfaces
2-[88](#__RefHeading___Toc457875900)

Figure 2.61 Customer Interfaces for Time
2-[90](#__RefHeading___Toc457875901)

Figure 2.62 MET Output Format 2-[91](#__RefHeading___Toc457875902)

Figure 2.63 Hitchhiker/Customer Communications
2-[93](#__RefHeading___Toc457875903)

Figure 2.64 ACCESS Low Rate Data Processing
2-[94](#__RefHeading___Toc457875904)

Figure 2.65 ACCESS Medium Rate Data Processing Unit
2-[95](#__RefHeading___Toc457875905)

Figure 2.65 Switch Panels 2-[112](#__RefHeading___Toc457875906)

Figure 2.66 SPASP or SSP Switch and Indicator Characteristics
2-[113](#__RefHeading___Toc457875907)

Figure 2.67 SSP Cargo Element Switching and Fusing Interface Schematic
(1of 2) 2-[114](#__RefHeading___Toc457875908)

Figure 2.68 SSP Cargo Element Switching and Fusing Interface Schematic
(2 of 2) 2-[115](#__RefHeading___Toc457875909)

Figure 2.69 HH-J Control Concept 2-[117](#__RefHeading___Toc457875910)

Figure 2.70 HH-J Power Distribution
2-[118](#__RefHeading___Toc457875911)

Figure 2.71 HH-J Bi-level command electrical interface
2-[120](#__RefHeading___Toc457875912)

Figure 2.72 Malfunction Input Circuitry
2-[122](#__RefHeading___Toc457875913)

Figure 2.73 Ejection System Overview
2-[127](#__RefHeading___Toc457875914)

Figure 2.74 Payload Interface Plate
2-[128](#__RefHeading___Toc457875915)

Figure 2.75 Hitchhiker Ejection System with Door
2-[129](#__RefHeading___Toc457875916)

Figure 2.76 Hitchhiker Carrier Ejection System with Open Canister
2-[130](#__RefHeading___Toc457875917)

Figure 2.77 Pallet Ejection System with Door
2-[131](#__RefHeading___Toc457875918)

Figure 2.78 Pallet Ejection System with Open Canister
2-[132](#__RefHeading___Toc457875919)

Figure 2.79 Pallet Ejection System on Single Bay Pallet
2-[133](#__RefHeading___Toc457875920)

**List of Tables**

Table 2.1 HH Carrier Equipment Capacities
2-[2](#__RefHeading___Toc456763650)

Table 2.2 Container And Payload Flight Steady State Thermal Results
2-[46](#__RefHeading___Toc456763651)

Table 2.3 GAS Container External Thermal Levels at Steady State
2-[46](#__RefHeading___Toc456763652)

Table 2.4 Plate Electrical Interface Connectors
2-[52](#__RefHeading___Toc456763653)

Table 2.5 Canister Electrical Interface Connectors
2-[56](#__RefHeading___Toc456763654)

Table 2.6 Circuit Protection Requirements
2-[59](#__RefHeading___Toc456763655)

Table 2.7 Customer Electrical Interfaces And Service Summary
2-[59](#__RefHeading___Toc456763656)

Table 2.8 Hitchhiker Electrical Accommodations
2-[60](#__RefHeading___Toc456763657)

Table 2.9 ACCESS ‑ CGSE Communications Line
2-[97](#__RefHeading___Toc456763658)

Table 2.10 Pin Designation For RS-232 Asynchronous Data
2-[98](#__RefHeading___Toc456763659)

Serial Formatted Data 2-[98](#__RefHeading___Toc456763660)

Table 2.11 Pin Designation for RS-422 Asynchronous Data
2-[99](#__RefHeading___Toc456763661)

Table 2.12 Pin Designation For Customer RS-422 Medium Rate Data
2-[100](#__RefHeading___Toc456763662)

(ACCESS to CGSE) 2-[100](#__RefHeading___Toc456763663)

Table 2.13 Access Formatted Asynchronous Data Message Structure
2-[102](#__RefHeading___Toc456763664)

Table 2.14 Access Formatted Payload Analog Data Structure
2-[103](#__RefHeading___Toc456763665)

Table 2.15 Access Ancillary Data Message Structure
2-[104](#__RefHeading___Toc456763666)

Table 2.16 Shuttle Orbit And Attitude Data Message Structure
2-[105](#__RefHeading___Toc456763667)

Table 2.17 Access Command Completion Status Message Structure
2-[109](#__RefHeading___Toc456763668)

Table 2.18 Access Data Link Status Message Structure
2-[110](#__RefHeading___Toc456763669)

Table 2.20 Hitchhiker-Jr Electrical Interface Connections
2-[123](#__RefHeading___Toc456763670)

Table 2.21 Characteristics Of Hitchhiker Launcher Systems
2-[126](#__RefHeading___Toc456763671)

# THE HITCHHIKER CARRIER SYSTEM

The HH carrier system implements various modular hardware in mounting
customer equipment in the payload bay. HH-S customer equipment is
mounted in canisters, on small mounting plates, or directly to the
Orbiter adapter beams. HH-C customer hardware is mounted to the HH
bridge using standard canister hardware, small experiment mounting
plates, or custom-mounting equipment. The standard avionics unit forms a
part of both the HH-S and HH-C configurations. This unit provides the
electrical interface between the Orbiter and up to six customer units.
The weights of the various carrier units and their maximum customer
weight capacities are shown in Table 2.1. Actual allowable customer
weight depends on detailed analysis of actual mounting configuration and
center of gravity. Table 2.1. also shows the weights of the GAS-type
beam (attachment hardware for HH-S) and Keel Trunnion attachment
hardware (used with HH-C). The attachment hardware weight is not counted
in determining reimbursement to NASA for transportation cost.

Customer interfaces for the side-mount and cross-bay versions of HH have
been designed to be as similar as possible allowing many customer
payloads to be accommodated on either carrier. This results in maximum
manifesting flexibility.

An additional HH version, Hitchhiker-JR (HH-J) is available for small
instruments which require only canister mounting and do not require
real-time ground command or data services. HH-J has customer electrical
interfaces similar to GAS and can be accommodated on Shuttle missions
where Orbiter electrical services required by the standard HH carrier
are not available. HH-J customers are not required to support the
control center operations required by the other HH versions and can
avoid the cost and effort associated with the necessary equipment and
personnel.

[]{#__RefHeading___Toc456763650 .anchor}Table 2.1 HH Carrier Equipment
Capacities

+------------------------------------+----------+---------+-----------+
| Carrier Equipment                  | Maximum  | C       | Mounting  |
|                                    | Carrier  | ustomer | Surface   |
|                                    | Weight   |         |           |
|                                    | (lbs)    | Weight  |           |
|                                    |          | (lbs)   |           |
+------------------------------------+----------+---------+-----------+
| Sealed Canister (insulated top     | 160      | 200     | 19.75\"   |
| plate)                             |          |         | Dia.      |
+------------------------------------+----------+---------+-----------+
| Sealed Canister (uninsulated top   | 140      | 200     | 19.75\"   |
| plate)                             |          |         | Dia.      |
+------------------------------------+----------+---------+-----------+
| Motorized Door Canister            | 235      | 170     | 19.75\"   |
|                                    |          |         | Dia.      |
+------------------------------------+----------+---------+-----------+
| HH-S Small EMP                     | 55       | 300     | 25\" x    |
|                                    |          |         | 39\"      |
+------------------------------------+----------+---------+-----------+
| HH-S Direct Mount                  | \-       | 700     | 20\" x    |
|                                    |          |         | 40\"      |
+------------------------------------+----------+---------+-----------+
| HH-C Side Mounting Plate           | 61       | 250\*   | 25.6\" x  |
| (Experiment)                       |          |         | 39.5\"    |
+------------------------------------+----------+---------+-----------+
| (No Brackets)                      |          |         |           |
+------------------------------------+----------+---------+-----------+
| HH-C Small Top Mounting Pallet     | 90       | 600\*   | 33.38\" x |
| (Exp.)                             |          |         | 27.45\"   |
+------------------------------------+----------+---------+-----------+
| HH-C Large Top Mounting Pallet     | 207      | 600\*   | 55.65\" x |
| (Exp.)                             |          |         | 33.38\"   |
+------------------------------------+----------+---------+-----------+
| (No Brackets)                      |          |         |           |
+------------------------------------+----------+---------+-----------+
| Avionics Unit (includes mounting   | 236      | \--     | \--       |
| plate & mounting hardware)         |          |         |           |
+------------------------------------+----------+---------+-----------+
| HH-C (includes avionics unit,      | 2165     | 1200    | Custo     |
| mounting plate and standard MPE)   |          |         | m-mounted |
+------------------------------------+----------+---------+-----------+

[Attachment Hardware]{.underline} [Weight]{.underline}

HH-S GAS Beam, Bays 2-8, 12, 13 70 lbs.

HH-C Bridge Attachment Fittings for Bay 2 365 lbs.

HH-C Bridge Attachment Fittings for Bay 3 418 lbs.

\*Specific center of gravity envelope limits weight capability.

## Mechanical Support Systems

HH-S and customer hardware will be side-mounted to the Orbiter payload
bay longeron and frame attachment points using GAS-type adapter beams.
HH-S carrier components are illustrated in Figure 2.1. HH-C payloads are
carried on an across-the-bay structures as described in section 2.1.4.

Existing HH-S equipment is designed to be mounted on the starboard side
of the cargo bay in bay locations 2 or 3. These locations are indicated
in Figure 2.2 which shows the forward-most available positions in the
bay for the GAS adapter beam mounting as well as the X-axis station
numbers associated with these positions.

Figure 2.3 depicts an example of a typical structural configuration for
HH-S payloads. Figure 2.4 shows a sideview of a typical HH-S payload
mounting.

All plates that are to be side-mounted to the Orbiter are parallel to
the X-Z plane. The X axis is along the long axis of the Orbiter;
positive towards the tail. The Y axis is across the payload bay positive
towards the starboard (right) wing. The Z axis completes the coordinate
system and is positive moving \"up\" from the bottom of the Orbiter
payload bay. See Figure 2.5.

The dynamic envelope of the cargo bay defines the maximum permitted
extent of thermal and dynamic distortions of payload equipment. A
maximum static design radius of 88 inches has been established for
customer hardware (Figure 2.6). The maximum dynamic envelope radius is
90\" (Figure 2.6). The maximum extent of payload equipment out from the
sides of the mounting plates (along the Orbiter + X directions) is
mission-dependent. It will normally, however, be restricted to the width
of the mounting plate to prevent interference with Orbiter integration
Ground Support Equipment (GSE).

The following subsections describe the various mechanical accommodations
available with the HH-S system.

![](media/image1.png)

[]{#__RefHeading___Toc457875841 .anchor}Figure 2.1 Hitchhiker-S Carrier
Components

![](media/image2.png){width="4.75625in" height="8.188194444444445in"}

[]{#__RefHeading___Toc457875842 .anchor}Figure 2.2 Hitchhiker-s
Available Sidewall Mounting Locations

![](media/image3.png){width="6.295138888888889in"
height="7.588888888888889in"}

[]{#__RefHeading___Toc457875843 .anchor}Figure 2.3 Hitchhiker-S Typical
Structural Configuration

![](media/image4.png){width="6.295833333333333in"
height="7.843055555555556in"}

[]{#__RefHeading___Toc457875844 .anchor}Figure 2.4 Hitchhiker-S Payload
Mounting Concept (Sideview)

![](media/image5.png){width="5.452083333333333in"
height="6.898611111111111in"}

[]{#__RefHeading___Toc457875845 .anchor}Figure 2.5 Orbiter Coordinate
System

![](media/image6.png)

[]{#__RefHeading___Toc457875846 .anchor}Figure 2.6 Maximum Payload
Static and Dynamic Envelopes

### HH Canister

The HH canister is an adaptation of the canister developed by the GAS
Program. It is mechanically very similar to a GAS canister and offers
the customer the simplest mechanical accommodation in the HH‑S system.
It is available as a completely closed canister (Figure 2.7) or with an
opening lid known as the Hitchhiker Motorized Door Assembly (HMDA)
(Figure 2.8). Figure 2.9 shows the canister mechanical and electrical
components. Figure 2.10 illustrates the field-of-view restrictions for
payloads using the HMDA. Canister extensions to facilitate additional
payload volume are available as an optional service and will be
considered on a case-by-case basis.

Use of the standard container facilitates safety. The container provides
for internal pressure which can be varied from near vacuum to about 1
atmosphere absolute. It also provides thermal protection for the
experimental apparatus. The sides of the container may be thermally
insulated or may be uninsulated with a white paint surface. The top may
be insulated or not, depending upon the customer requirements. The
bottom of the container is always insulated.

The experiment mounting plate, which is also the upper end plate of the
canister, provides a standardized mounting surface for customer
hardware. Any experiment venting will be through the experiment mounting
plate. The lower end plate contains ports through which a payload may
vent. The HMDA uses a different experiment mounting plate and similar,
but different, payload venting.

The weight the canister can support depends upon whether it is mounted
for a HH-S or HH-C configuration. For the HH-S configuration, the
canister is qualified to support 200 lbs. of payload weight. The HH-C
configuration is qualified to carry a total of 400 lbs. for the canister
carrier weight and payload weight. If the canister carrier weight to
support a payload increases, then the payload weight that can be flown
is reduced. For example, a standard insulated canister with an
uninsulated top plate weighs about 140 lbs., this would limit the
payload to 260 lbs. If the payload required the HMDA, then the payload
weight allowed would be reduced by the weight of the HMDA.

#### Container Construction

The standard container is made of aluminum. There is white paint or
multilayer insulation on the exterior. The top may or may not be
insulated depending on the particular Shuttle mission and needs of the
experimenter. The circular top and bottom end plates are 5/8\" thick
aluminum.

The bottom 3\" of the container is reserved for HH‑S interface equipment
such as interface harnesses and venting systems. This volume is in
addition to the 5-cubic foot space available to the experimenter.

The container is a pressurized container capable of:

a\. maintaining about 1 atmosphere absolute pressure at all times, (dry
nitrogen or dry air),

b\. evacuation during launch and repressurization during re‑entry
(vented).

c\. evacuation prior to launch.

d\. evacuation on orbit with vacuum being maintained through re-entry.

![](media/image7.png){width="6.159027777777778in"
height="8.140277777777778in"}

[]{#__RefHeading___Toc457875847 .anchor}Figure 2.7 Hitchhiker Sealed
Canister

![](media/image8.png){width="5.846527777777778in"
height="8.297916666666667in"}

[]{#__RefHeading___Toc457875848 .anchor}Figure 2.8 Hitchhiker Motorized
Door Canister

![](media/image9.png){width="6.489583333333333in" height="7.44375in"}

[]{#__RefHeading___Toc457875849 .anchor}Figure 2.9 Hitchhiker canister

![](media/image10.png){width="5.277777777777778in"
height="8.628472222222221in"}

[]{#__RefHeading___Toc457875850 .anchor}Figure 2.10 Hitchhiker-S
Canister Mounting to Orbiter

#### Sealed Canister Experiment Mounting Plate 

The sealed canister upper end plate (see Figure 2.11) serves four
purposes:

a\. it seals the upper end of the standard container,

b\. it provides a mounting surface for the experimental equipment,

c\. it can act as a thermal absorption or radiation surface, and

d\. it provides accommodations for experiment box venting when required.

The inner surface of the plate has a hole pattern adaptable for mounting
a variety of hardware. Forty-five stainless steel, internally threaded
inserts exist for experiment mounting purposes. The experimenter may use
any of them in any combination required. The inserts do not go through
the plate. They will accept #10 ‑ 32 UNF machine screws to a depth of
0.31 inches. The project is responsible for approving the structural
dimensions of the experiment interface and the number and location of
mounting screws.

The line from the center of the plate through the two purge ports will
always be positioned toward the starboard (right) side of the Orbiter,
perpendicular to the Orbiter centerline.

The canister will be purged with dry nitrogen, or dry air, as specified
by the customer. Two purge ports are shown on the experiment mounting
plate (see Figure 2.11). At least one of these must be unobstructed to
allow purged gas to flow through the canister.

The customer must provide a grounding strap from the payload to the
experiment mounting plate. Any mounting hole on the experiment mounting
plate may be used for grounding.

If safety considerations require that a battery box or other component
be vented, it can be plumbed to a special pressure-relief valve turret
(illustrated in Figure 2.12). Since the turret can be rotated 360^o^,
the experimenter can pick the most convenient orientation within the
plumbing circle shown in Figure 2.11. If no turret is required for the
payload, this area will be completely clear and will not affect payload
mounting.

The customer must provide attachment points on the bottom of the payload
structure for lifting in the inverted orientation by means of a crane
and sling. The sling must be provided by the customer. Customers may not
alter the mounting plate unless changes have been negotiated with the HH
Project Office. As an optional service to be individually negotiated,
the top mounting plate may be modified to provide apertures or customer
electrical connectors. Customer equipment may be mounted to the top
(external) surface of the mounting plate.

![](media/image11.png){width="6.290972222222222in"
height="7.291666666666667in"}

[]{#__RefHeading___Toc457875851 .anchor}Figure 2.11 Hitchhiker Sealed
Canister (Upper End Plate)

![](media/image12.png){width="5.7868055555555555in"
height="7.310416666666667in"}

[]{#__RefHeading___Toc457875852 .anchor}Figure 2.12 Hitchhiker Sealed
Canister -- Battery Vent Turret Interface

#### Opening Lid Canister

A canister may be fitted with a HMDA if the customer payload requires a
field of view or exposure to the space environment. The door is opened
and closed by ground command as required. The HMDA is capable of
maintaining a 15 psi differential (psid) pressure or evacuated
environment similar to the standard canister. It is possible to eject
packages from a HMDA canister; however, the interface and safety
requirements are considerably beyond the scope of this document and must
be defined and approved on a case-by-case basis.

HMDA canisters are normally equipped with redundant pressure-relief
valves which act to reduce the pressure to less than 1 psid during
ascent. Once in orbit, a ground command may be used to open a vent valve
and reduce the pressure to less than 0.1 psid prior to opening the door.
HMDA canisters normally return with internal vacuum.

The mounting provisions for the opening lid canister are shown in Figure
2.13. Because the contents of the canister are exposed when the door is
open, the materials, safety, and Electro-Magnetic Interference (EMI)
considerations are essentially the same as for plate-mounted hardware.

For safety considerations, a pressure-relief valve turret designed for
use on the HMDA Mounting Plate is available to vent battery boxes or
other components (see Figure 2.15). Four venting locations have been
provided to accommodate battery box orientation requirements. An
experiment may use any one of these four locations. If no turret is
required for the payload, this area will be completely clear and will
not affect payload mounting.

Multiple interlocks are provided to prevent the door from opening prior
to or during ascent. However, in the event of an in-flight door failure,
the contents of the canister must be designed to allow safe descent and
landing with the door open. The customer is responsible for designing
and providing any thermal treatment of exposed surfaces.

#### Canister Orientation

A canister will always be mounted with the experiment mounting plate
facing out of the payload bay. There are, however, two different
container ground handling orientations. First, during insertion of a
payload into the container and the subsequent checkout and
transportation, the container\'s major axis will be vertical. Second,
after the container is installed in the Orbiter bay, the container\'s
orientation will become Orbiter dependent, i.e., the major axis of the
container will be perpendicular to that of the Shuttle.

Care should be taken in experiment design to assure that systems that
are sensitive to ground orientations, such as wet cell batteries, are
properly oriented in the experiment. The customer should inform the HH
staff of any special payload orientation requirements which must be met
prior to installation in the Orbiter.

#### Lateral Load Support 

Because the experiment structure will be cantilevered from the
experiment mounting plate, radial loads at the free end of the
experiment structure must be supported by at least three equally spaced
bumpers between the experiment structure and the canister. Figure 2.16
illustrates one possible bumper design configuration.

The customer is responsible for providing bumpers as part of the
experiment hardware. Bumper design should be in accordance with the
following guidelines:

> a\. A minimum surface area of 4 in^2^ (2\" x 2\") should be used for
> each bumper pad.
>
> b\. The bumper face should have a 10-inch radius so that it will fit
> snugly when adjusted against the 20-inch diameter container.
>
> c\. Where the bumper contacts the container wall, it should be faced
> with a resilient material at least 1/8 inch thick to protect the
> container. If the container is to be evacuated, select a
> non‑outgassing material such as viton. If the bumper face is not
> round, every corner should have a minimum radius of 0.40 inches.

d\. It is very important to provide a positive locking device for the
bumpers. Do not depend on friction or a set screw alone to hold them in
place.

> e\. After installing the payload in the container, bumper adjustment
> should be easily accessible from the open lower end of the container.

#### Center of Gravity (CG) Considerations 

To minimize the amount of analysis required for a particular mission,
the composite CG of a canister and payload must be constrained within
certain limits. The CG envelope is shown in Figure 2.14.

![](media/image13.png){width="6.289583333333334in"
height="7.618055555555555in"}

[]{#__RefHeading___Toc457875853 .anchor}Figure 2.13 Opening Lid Canister
-- Experiment Mounting Plate

![](media/image14.png){width="6.292361111111111in"
height="7.875694444444444in"}

[]{#__RefHeading___Toc457875854 .anchor}Figure 2.14 Canister CG
Envelope-Adapter Beam or Bridge Mounting

![](media/image15.png)

[]{#__RefHeading___Toc457875855 .anchor}Figure 2.15 Hitchhiker Motorized
Door Canister -- Battery Vent Assembly

![](media/image16.png){width="6.086805555555555in"
height="7.259027777777778in"}

[]{#__RefHeading___Toc457875856 .anchor}Figure 2.16 Bumper Design
Example

#### Customer Emblems

HH customers may attach a logo or emblem to the exterior of their
equipment. Emblems may also be attached to the exterior of canisters
containing customer equipment. The canister emblems should be on a .010
inch Lexan sheet 11 inches square. Emblem artwork must be submitted to
GSFC for NASA approval. Materials used for emblems must meet all Space
Shuttle payload bay materials requirements.

### Plate Mounting

Experiment packages which are not best suited for the canister approach
may be mounted on a plate (see Figure 2.17). A small HH-S plate is
capable of supporting experiment packages of up to 300 pounds, mounted
on an area 25\" x 39\". Customer equipment is attached to the core plate
using a grid hole pattern on 2.756\" (70-mm) centers with 3/8\" - 24 UNF
stainless steel bolts. The bolts are supplied by the HH Project. A
similar matrix of #10 - 32 mounting bolt locations will be used by the
HH staff to route interface cables as well as intercomponent harnessing
and plumbing. The experiment structural dimensions and attachment points
at the mounting plate interface must be reviewed for acceptance by the
HH Project.

####  Experiment Package Integrity

The package must be designed, fabricated, inspected, analyzed, and
tested to demonstrate the ability to constrain, or to contain, the
elements of the experiment package during launch, flight, and landing.
All customer equipment shall be designed to withstand limit acceleration
load factor limits as stated in Section 3.1.1.3.2. Also refer to Random
Vibration Verification Levels given in Section 3.1.1.5.3 (Table 3.6).

####  Experiment Package Volume

Specific volume restrictions other than those provided in Section 2.1
are not generally placed on customer equipment since the equipment mass
and CG location are the controlling factors. In general, the experiment
CG should be located as close to the mounting interface as practical.
The complexity of the weight/CG relationship, the possibility of
multiple customers per plate, manifesting considerations, and other
factors require that the HH-S staff perform accommodation assessments on
a case-by-case basis. Guidance will be provided to determine specific
equipment design and accommodation details as part of the normal
mechanical interface documentation exchange.

![](media/image17.png){width="5.989583333333333in" height="8.0875in"}

[]{#__RefHeading___Toc457875857 .anchor}Figure 2.17 Hitchhiker-S
Experiment Mounting Plate

#### Mounting Bolt Loading Limitations

The mounting bolts must be included in the payload stress and fracture
analysis (see Section 3.0). Bolt strength and material data will be
supplied by the HH Project.

### Direct Mounting of Experiment Package

The maximum weight-carrying configuration in the current HH-S system is
accomplished by mounting the customer\'s flight unit directly to the
Adapter Beam Assembly (ABA). This mode will accommodate up to 700 pounds
but requires detailed case-by-case analysis and approval. The mounting
hardware between the experiment package and the ABA will be supplied by
the HH Project. The available experiment mounting locations are noted in
Figure 2.18.

#### Experiment Package Integrity

See 2.1.2.1 for design considerations.

#### Experiment Package Volume and Mounting Limitations 

The experiment volume in the direct mount configuration can be somewhat
higher than in the plate mount setup; however, it is similarly
restricted as described in subsections 2.1.2.2 and 2.1.2.3. The HH staff
provides assistance in adapting customer hardware to the ABA interface
and defining CG and volume restrictions. Direct-mount payloads are
normally designed to be mounted on the adapter beam after the beam is
installed in the Orbiter. The mounting scheme must be simple and involve
captive fasteners. In the event that a payload is designed to mount on
the beam prior to Orbiter installation, adequate access to the longeron
bolts must exist. Special lifting equipment for hoisting the
payload/beam combination must also be provided.

### HH-C Structure

The HH-C cross-bay carrier is implemented using a truss structure
(Figure 2.19) called the Hitchhiker Bridge Assembly (HHBA). The HHBA is
similar to other Mission Peculiar Experiment Support Structure (MPESS)
structures used on Spartan, GAS, Materials Science Laboratory (MSL), and
other NASA payload programs and consists of an upper support structure
and a lower support structure. The lower structure is normally attached
to the upper structure at the launch site. During integration and
transportation to the launch site, the upper structure is mounted on a
special dolly (see Figure 2.20) which allows easier access and handling.

![](media/image18.png){width="6.293055555555555in"
height="8.220833333333333in"}

[]{#__RefHeading___Toc457875858 .anchor}Figure 2.18 Adapter Beam
Mounting Interfaces

![](media/image19.png){width="6.295833333333333in"
height="7.9430555555555555in"}

[]{#__RefHeading___Toc457875859 .anchor}Figure 2.19 Hitchhiker-C Payload

![](media/image20.png){width="4.573611111111111in"
height="7.333333333333333in"}

[]{#__RefHeading___Toc457875860 .anchor}Figure 2.20 HHBA Upper Structure
on Shipping Dolly

#### Standard HHBA

Attachment of payload equipment to the HHBA is done by means of special
Mission Peculiar Equipment (MPE), structure elements which can be
attached to the HHBA in five different locations spaced 28.20 inches
apart across the top and sides of the structure. The standard MPE has
eight positions on the sides of the HHBA for side experiment mounting
plates and canisters. However, one experiment mounting plate position is
reserved for the HH avionics. Of the remaining seven positions, three
can be used for side experiment mounting plates or canisters. The other
four positions can only be used for canisters. The HHBA and MPE are
un-insulated and can experience large temperature deviations during a
mission. For this reason, special mounting brackets are used to attach
the plates and canisters to the MPE. The brackets provide thermal
isolation and allow for thermal expansion when plates or canisters are
temperature controlled.

The top of the MPE structure has positions for two sizes of top plates.
It will accommodate two large top plates, four small top plates or
combination thereof. Customers considering accommodation on the HHBA
should request drawing number GE1550253 from the HH Project for
additional detailed information beyond what is listed in the following
sections.

#### HH-C Canisters

Canisters identical to those specified for HH-S can be used with the
HH-C. The canister is rotated 90 degrees about the Z axis in the HH-C
case. All possible canister locations are shown in Figures 2.21, 2.22,
and 2.23. Figure 2.21 shows the HH-C Canister Locations. Figure 2.22
shows the HH-C Canister and Mounting Plates, and Figure 2.23 shows the
HH-C Canister highlighting the Y-Axis Coordinates and Field-of-View
Restrictions

#### HH-C Side Mounting Plates

The HH-C side mounting plates (shown in Figure 2.24) are functionally
identical to, although not interchangeable with, the small HH-S mounting
plates. The plates are 25\" x 39\" and can support up to 250 pounds. The
\"Y\" and \"Z\" axis coordinates of these plates and the field-of-view
restrictions are shown in Figure 2.25.

![](media/image21.png){width="6.293055555555555in"
height="7.440277777777778in"}

[]{#__RefHeading___Toc457875861 .anchor}Figure 2.21 Hitchhiker-C
Canister Locations

![](media/image22.png){width="6.294444444444444in"
height="8.221527777777778in"}

[]{#__RefHeading___Toc457875862 .anchor}Figure 2.22 Hitchhiker-C
Canister and Mounting Plates

![](media/image23.png){width="6.309722222222222in"
height="8.090277777777779in"}

[]{#__RefHeading___Toc457875863 .anchor}Figure 2.23 Hitchhiker-C
Canister

![](media/image24.png){width="6.29375in" height="7.613888888888889in"}

[]{#__RefHeading___Toc457875864 .anchor}Figure 2.24 Hitchhiker-C
Mounting Plate Locations

![](media/image25.png){width="6.298611111111111in"
height="8.318055555555556in"}

[]{#__RefHeading___Toc457875865 .anchor}Figure 2.25 Hitchhiker-C
Mounting Plate

#### HH-C Top Mounting Pallets

The HH-C top mounting pallets are also shown in Figure 2.24. Their
field-of-view restrictions are shown in Figure 2.25. The small pallet is
roughly 33\" by 27\". The large pallet is roughly 33\" by 56\". Both
pallets can handle up to 600 pounds, provided the center of gravity of
the experiment hardware is within the design envelopes as shown in
Figure 2.26.

#### HH-C Direct Mounting

Large/heavy customer equipment which is not suitable for accommodation
on the standard plates or canisters may be attached directly to existing
HH MPE or may be attached to the structure by means of new
customer-unique MPE, provided by GSFC as an optional service. Hardware
mounting locations are shown in Figure 2.27. In either case, the
customer\'s structural design must safely accommodate larger
differential temperature changes between his/her equipment and the
carrier. Proposals for direct mounting should be sent to the HH project
for evaluation.

### HH Side Mounting Plates 

The HH side mounting plate is a generic plate combining the capabilities
of the HH-S and HH-C side plates.

![](media/image26.png){width="6.294444444444444in"
height="7.567361111111111in"}

[]{#__RefHeading___Toc457875866 .anchor}Figure 2.26 CG Envelope &
Positions

![](media/image27.png){width="6.295833333333333in"
height="8.125694444444445in"}

[]{#__RefHeading___Toc457875867 .anchor}Figure 2.27 Hitchhiker-C
Experiment Mounting Interface

## Thermal Considerations

### Thermal Design Requirements

The Hitchhiker carrier and customer equipment relies primarily on a
passive thermal design consisting of multilayer insulating blankets
(MLI) and selected surface-finish applications. The MLI will be used to
reduce energy losses and gains from the environment. Thermostatically
controlled heaters will be used where tighter thermal control is needed,
and passive radiators will be used to dump excess heat from instruments.
This cold-bias design philosophy incorporates a low cost approach to
maintaining temperature requirements throughout the HH payload.

The thermal design and analysis of each experiment is a customer
responsibility. The customer shall determine all internal conduction,
convection, and radiation within their experiment. They shall be
responsible for the proper design and coupling of high power components.
Reduced thermal models of the experiment and associated electronics are
to be supplied to HH. Temperature limits as defined below shall also be
provided for each node in the reduced thermal math model.

> [Operating Temperature:]{.underline} The temperature at which a unit
> will successfully function and meet all specifications.
>
> [Non-Operating Temperature:]{.underline} The temperature to which a
> unit may be exposed in a power OFF condition and if turned ON, will
> not be damaged. The unit does not have to meet its specification until
> it is within the operational temperature range.
>
> [Survival Temperature:]{.underline} The temperature, if exceeded, at
> which the unit will suffer permanent damage.
>
> [Safety Temperature]{.underline}: The temperature, if exceeded, at
> which the unit could potentially lead to catastrophic damage to the
> orbiter or injury to the crew members.

The customer shall also define any special temperature requirements,
such as levels and gradients. Ground temperatures and humidity provided
by the Orbiter and other ground processing locations at KSC are defined
in ICD2-19001.

A list of the following external surface properties: area (size),
thermal coatings, absorptivity (α), emissivity (ε), and reflectivity
shall be provided. The customer will be responsible for obtaining
approval from GSFC regarding any proposed thermal coatings not standard
to HH. They shall also be responsible for providing heaters on the
experiment provided hardware. The heater specification along with the
predicted dissipation, duty cycle and HH bus usage shall be supplied to
HH.

### Thermal Safety Requirements

The customer must also be aware of all safety concerns of their payloads
including that the experiment must be safe without services i.e. remain
safe in the event of a power loss. Payloads must also be safe to land 40
minutes after payload bay door closure, occurring anytime during the
mission. In addition to all safety analysis, all payloads must be able
to fly in a bay-to-Earth attitude continuously and must be able to
withstand 30 minute solar excursions and 90 minute deep space viewing at
a minimum as stated in the Orbiter core ICD-2-19001. It is desirable to
be able to withstand these extreme cases longer than the ICD requirement
for manifesting reasons and longer runs are required for determining
safety concerns such as the maximum design pressure (MDP) temperatures
and battery limitations. The transient behavior of the experiment should
be considered in all thermal analysis for the aforementioned cases.

### Flammability Requirements for MLI Construction

Thermal control blankets are the most widely used materials in the
payload bay that could be flammable. These blankets typically contain 12
to 40 layers of film (0.0005 to 0.002 inches in thickness) separated by
some type of scrim cloth. Blanket materials are usually constructed of
metal-coated polyethylene terephthalate or polyimide film, organic
separator scrim, or beta cloth. Beta cloth and polyimides (at least 1.5
mil thick) are the only nonflammable materials.

Acceptable thermal control blankets are typically constructed as
follows:

a.  The outer layer is made of nonflammable material such as a polyimide
    film (at least 1.5 mil thick,) metal foil, or beta cloth.

b.  Internal layers can be a combination of flammable films or scrims.

c.  The innermost layer (adjacent to the outer surface of the payload)
    is also made of nonflammable materials.

d.  Edges are hemmed or suitably finished so that the inner flammable
    layers are protected.

Reference: "Flammability Configuration Analysis for Spacecraft
Applications" document NSTS 22648 dated October 1988.

### Thermal System Design for a HH Canister

There are presently four options available to HH canister customers:

1\. Fully insulated canister

2\. Insulated canister without upper insulating end cap.

3\. Uninsulated canister with lower insulating end cap.

4\. Opening lid canister (uses insulated canister).

The first three options pertain to a sealed HH canister, while the
fourth refers to the opening lid canister. The three canister insulation
options for the sealed canister are intended to offer a wide range of
heat rejection capabilities depending on customer requirements. GSFC
provides all exterior thermal insulation and coatings for canisters
except for the top surface of an HMDA customer payload. The temperatures
listed for each orientation are approximate, and may vary somewhat
(approx. +/- 10ºC) depending on the Shuttle orbital attitude and beta
angle (angle between the Shuttle orbit plane and the sun).

The first option, a fully insulated canister, would be the best choice
for customers with relatively low power requirements. This option
minimizes heater power needed to maintain operational temperature levels
at cold Orbiter orientations. It does not, however, allow for large
power dissipations on a continuous basis. Average steady-state canister
upper endplate temperatures for various Shuttle attitudes and customer
payload power levels is given in Figure 2.28. The temperatures from
Figure 2.28 are representative of internal experiment temperature
levels. The corresponding Orbiter attitudes are defined in Figure 2.29.

Option 2 offers an increased heat rejection capability over option 1, as
shown in Figure 2.30. The canister top plate exterior surface is coated
with silver teflon ( = . 10,  =.75) and acts as a radiator while the
rest of the canister is insulated. Increased heater power, however, is
required in order to maintain minimum temperature levels in cold Orbiter
orientations. .

Option 3 is available to customers requiring a large heat rejection
capability. In this case, the side walls of the canister are painted
white ( =.24,  = .86) and are allowed to radiate directly to the
Shuttle bay and space. The average upper endplate temperature for
various conditions is given in Figure 2.31. Power levels higher than
those shown can be accommodated for short time periods depending on
customer thermal design. However, large temperature gradients can be
realized along with high power levels. Therefore, special attention
should be given to the thermal design if Option 3 is selected. Also,
large heater power levels are required to maintain minimum temperature
levels even in the Earth viewing case if the experiment is operating at
low levels. Transient response times are reduced as well.

Option 4 refers to the opening-lid canister. When the lid is closed, the
canister thermal behavior is approximately the same as that of the fully
insulated canister (Option 1). When open, thermal behavior is heavily
dependent on the customer payload thermal design, especially the exposed
upper portion of the instrument. It is suggested that customers using
this option pay particular attention to their thermal design, due to the
increased complexity resulting from the opening lid. Thermal information
for customers with opening-lids can be found in \"Thermal Design Guide
for Get Away Special/Motorized Door Assembly Users.\"

![](media/image28.png){width="5.902777777777778in"
height="8.664583333333333in"}

[]{#__RefHeading___Toc457875868 .anchor}Figure 2.28 Fully Insulated
Canister (Option1)

![](media/image29.png){width="6.498611111111111in"
height="8.186111111111112in"}

[]{#__RefHeading___Toc457875869 .anchor}Figure 2.29 Typical Orbital
Thermal Attitudes

![](media/image30.png){width="5.5055555555555555in"
height="8.417361111111111in"}

[]{#__RefHeading___Toc457875870 .anchor}Figure 2.30 Insulated Canister
without Insulated Endcap (Option 2)

![](media/image31.png){width="5.783333333333333in"
height="8.615972222222222in"}

[]{#__RefHeading___Toc457875871 .anchor}Figure 2.31 Uninsulated Canister
(Option 3)

Experimental data was obtained from the GAS Flight Verification Payload
(FVP) on the flight of STS‑3. Table 2.2 lists the steady‑state
temperature predictions and results for both hot and cold cases for the
inside portion of the FVP. The experimental results are averages of
thermistors or nodes at the indicated locations. The flight results
listed are the hottest and coldest levels actually attained. They are
not, however, the worst possible hot or cold case temperatures since
steady‑state conditions were not attained.

[]{#__RefHeading___Toc456763651 .anchor}Table 2.2 Container And Payload
Flight Steady State Thermal Results

(Temperatures In ºC) From Gas Verification Payload

> [HOT CASE]{.underline} [COLD CASE]{.underline}

[LOCATION]{.underline} [PREDICTED]{.underline} [ACTUAL]{.underline}
[PREDICTED]{.underline} [ACTUAL]{.underline}

Top Plate 48.0 32.0 ‑20.6 ‑2.5

Container Sides 49.2 32.0 ‑19.1 ‑3.0

Bottom Plate 49.9 34.0 ‑19.5 ‑3.0

Battery 52.3 31.0 ‑5.7 +1.0

Tape Recorder 52.9 35.0 0.0 +4.0

Power 13.0W 13.0W 34.0W 13.0W

Note: Actual flight thermal levels did not reach steady‑state
conditions. The levels are the maximum and minimum temperatures that
were reached.

Table 2.3 shows external environmental thermal levels for steady‑state
conditions of the GAS container. It includes both predicted and actual
flight thermal levels. Steady‑state temperatures were not attained for
the tail‑to‑sun, extreme cold case, which, therefore, is omitted from
the table. The two predicted values for the adapter beam hot case
correspond to two absorptivity values. The higher absorptivity value
gives a better hot case correlation.

[]{#__RefHeading___Toc456763652 .anchor}Table 2.3 GAS Container External
Thermal Levels at Steady State

> [PREDICTIONS ºC]{.underline} [FLIGHT ºC]{.underline}

Adapter Beam +37 to +46 +45 to +50

(Hot-Bay to Sun)

Adapter Beam -78 -40

(Cold-Nose to Sun)

Bottom Cover +63 +63 to +65

(Hot-Bay to Sun)

Bottom Cover -76 -45 to -50

(Cold-Nose to Sun)

Top Cover (Bracket) +31 +25 to +35

(Hot-Bay to Sun)

Top Cover (Bracket) -73 -47 to -52

(Cold-Nose to Sun)

### Thermal System Design for Pallet and Plate Mounting

The customer is responsible for the thermal design of a plate-mounted
experiment system. This design will encompass the plate and its
attachments to the GAS beam and Orbiter or to the HH bridge. Normally,
in order to avoid problems with thermal/mechanical stress, a customer
will want to provide good thermal conduction between his/her equipment
and the HH mounting plate. On HH-S, the mounting plate has poor thermal
conduction to the GAS beam. On HH-C, mounting plates are thermally
isolated from the cross bay structure by means of special hardware which
allows for thermal expansion. The HH-S GAS beam is attached to the
Orbiter with hardware that also provides thermal isolation and allows
for expansion.

GSFC will supply thermal model data on the HH plates and their
attachments to customers. GSFC will also supply insulation for the backs
of plates and white painted regions to cover the unoccupied front
surface of plates. GSFC will supply a standard heater system on the back
of the HH-S and HH-C small plate consisting of 104-watt heater and three
thermistors. For the top of the bridge single and double bay pallets,
GSFC will also supply 104 watts of heater power. (Thermostats on these
plates open at 12 +/- 3 deg C and close at 6 +/- 3 deg C.) The customer
may use this system by providing a cable to connect the thermal system
to power from his customer port.

### Thermistors

Three thermistors are available for each plate and pallet experiment.
Opening can experiments have no thermistors except for one mounted on
the lower endplate. Sealed canister experiments allow one thermistor to
be used at the customer\'s discretion and one will be mounted on the
lower end plate. Additional thermistors may be available through
negotiation with the HH project.

These thermistors, Yellow Springs Instrument Company (YSI) 44006 type or
equivalent (see the manufacturer\'s specification sheet on the following
page), are supplied by the HH Project for connection to appropriate pins
on J2, as outlined in Tables 2.4 and 2.5. This interface configuration
allows monitoring of up to three temperatures when customer payload
power is on or off. The thermistor interface between customer and
carrier is shown in Figure 2.33.

![](media/image32.png){width="5.922916666666667in"
height="6.996527777777778in"}

[]{#__RefHeading___Toc457875872 .anchor}Figure 2.32 YSI Precision
Thermistor

![](media/image33.png){width="5.997916666666667in"
height="6.895138888888889in"}

[]{#__RefHeading___Toc457875873 .anchor}Figure 2.33 Thermistor Interface
To Carrier

## Electrical/Power Support Systems

### Electrical Design 

The electrical interfaces for plate mount and canister customers differ
slightly. Figure 2.34 and Table 2.4 give plate mounting details. Figure
2.35, 2.36, and Table 2.5 provide details on the canister mount. Figure
2.36 shows the Motorized Door Canister with the control and monitoring
interface. Electrical designs interfaces are governed by ICD-2-19001.
The electrical characteristics of the thermistors is defined in Section
2.2.6.

### Power Characteristics

Each of the two 12 gauge 28V power lines is protected by a 20A fuse
(vacuum derated to 10A), per figure 2.37. Customers must provide
consistent wiring and fusing within their payloads. Smaller gauge wire
for power service shall require an appropriately down-sized fuse to
provide circuit protection. Table 2.6 shows acceptable wire and fuse
sizes.

![](media/image34.png)

[]{#__RefHeading___Toc457875874 .anchor}Figure 2.34 Hitchhiker Standard
Interface Cables

[]{#__RefHeading___Toc456763653 .anchor}Table 2.4 Plate Electrical
Interface Connectors

**[ID]{.underline} [PIN (Note 3)]{.underline} [Type (Note
2)]{.underline} [Function]{.underline}**

**[Power Connector J1]{.underline}: (Note 4)**

+28A A C +28V Power Circuit A

RETA B C Power Return (Note 1)

+28B C C +28V Power Circuit B

RETB D C Power Return (Note 1)

+28HTR E B +28V Heater Power

RETH F B Heater Power Return (Note 1)

FRMGND G B Frame Ground

**[Signal Connector J2:]{.underline} (Note 4)**

PCMAD 1 A PCM Analog Data

PCMINDX 41 A PCM Index Pulse

SIGGND 2 A Signal Ground

PCMCLK 42 A PCM Bit Rate Clock (Note 5)

PCMENA 32 A Serial Digital Enable A (Note 5)

PCMENB 33 A Serial Digital Enable B (Note 5)

PCMDATA 3 A Serial Digital Data A (Note 5)

PCMDATB 8 A Serial Digital Data B (Note 5)

THER1 14 A Thermistor 1

THER2 15 A Thermistor 2

THER3 16 A Thermistor 3

SHIELD 6 A Shield For Command And

> Data Signals

RD+ 21 A Receive Data Async + From SPOC

RD- 22 A Receive Data Async - From SPOC

SD+ 23 A Send Data Async + To SPOC

SD- 24 A Send Data Async - To SPOC

BLCMD1 17 A Bi-Level/Pulse Command 1

BLCMD2 18 A Bi-Level/Pulse Command 2

BLCMD3 19 A Bi-Level/Pulse Command 3

BLCMD4 20 A Bi-Level/Pulse Command 4

SCMDCLK 10 A Serial Command Clock (Note 5)

SCMDENV 11 A Serial Command Envelope (Note 5)

SCMDDAT 12 A Serial Command Data (Note 5)

METMIN 40 A MET/MET One Minute Pulse

IRIGMET+ 30 A IRIG-B MET (MET) +

IRIGMET- 31 A IRIG-B MET (MET) -

FRMGND 49 A Frame Ground

KUMRCLK+ 34 A Customer Generated MR Clock +

KUMRCLK- 35 A MR Clock -

**[ID]{.underline} [Pin (Note 3)]{.underline} [Type (Note
2)]{.underline} [Function]{.underline}**

KUMRDAT+ 43 A Customer Generated MR

> Data +

KUMRDAT- 44 A MR Data -

KUMRSHLD 25 A Shield For KU Signals

UNDTSP1+ 61 D Undedicated TSP 1 + (Optional Video +)

UNDTSP1- 66 D Undedicated TSP 1 - (Optional Video -)

UNDTSPS1 54 A Shield For Undedicated TSP 1

UNDTSP2+ 62 D Undedicated TSP 2 +

UNDTSP2- 63 D Undedicated TSP 2 -

UNDTSPS2 55 A Shield For Undedicated TSP 2

UNDTSP3+ 56 D Undedicated TSP 3 +

UNDTSP3- 57 D Undedicated TSP 3 -

UNDTSPS3 48 A Shield For UNDTSP3

UND4 58 A Undedicated 4

UND5 59 A Undedicated 5

UND6 60 A Undedicated 6

UND7 64 A Undedicated 7

UND8 65 A Undedicated 8

UNDS 53 A Shield For Undedicated 4-8

MDAOC 52 A Reserved

MDASTP 51 A Reserved

Note 1: Power Return Pins B, D And F May Be Connected Together Within
Payload.

Note 2: Wire Type Designations:

A 22 GA

B 16 GA

C 12 GA

D 26 GA

Note 3: Customer Will Make No Connections To Unused Pins

Note 4: The Designations \"J1\" And \"J2\" In This Table Indicate The
Pin Out For A Chassis Mount Connector Mounted To A Particular Scientific
Experiment. The Hh-Provided Connecting Cable Will Be Terminated In
Connectors With A Designation Of \"P1\" And \"P2\" But Will Have The
Identical Pin-Out As Shown In This Table.

Note 5: These services are no longer available/offered.

![](media/image35.png){width="6.290972222222222in"
height="7.764583333333333in"}

[]{#__RefHeading___Toc457875875 .anchor}Figure 2.35 Hitchhiker Standard
Interface Cables

![](media/image36.png){width="5.995138888888889in" height="7.5625in"}

[]{#__RefHeading___Toc457875876 .anchor}Figure 2.36 Hitchhiker Motorized
Door Canister

[]{#__RefHeading___Toc456763654 .anchor}Table 2.5 Canister Electrical
Interface Connectors

**[ID]{.underline} [Pin]{.underline}(Note 3) [Type]{.underline}(Note 2)
[Function]{.underline}**

**[Power Connector P1:]{.underline}**

+28A A C +28V Power Circuit A

RETA B C Power Return (Note 1)

+28B C C +28V Power Circuit B (Note 5)

RETB D C Power Return (Note 1)

+28HTR E B + 28V Heater Power

RETH F B Heater Power Return (Note 1)

FRMGND G B Frame Ground

**[Signal Connector P2:]{.underline}(Note 4)**

PCMAD 1 A PCM Analog Data

PCMINDX 41 A PCM Index Pulse

SIGGND 2 A Signal Ground

PCMCLK 42 A PCM Bit Rate Clock (Note 11)

PCMENA 32 A Serial Digital Enable A (Note 11)

PCMENB 33 A Serial Digital Enable B (Note 11)

PCMDATA 3 A Serial Digital Data A (Note 11)

PCMDATB 8 A Serial Digital Data B (Note 11)

THER1 14 A Thermistor 1 (Not Wired To PLD) (Note 6)

THER2 15 A Canister Pressure (Not Wired To PLD)

THER3 16 A MDA Door Position 0‑5 V (Note 7)

SHIELD 6 A Shield For Command And Data Signals

RD+ 21 A Receive Data Async + From SPOC

RD‑ 22 A Receive Data Async ‑ From SPOC

SD+ 23 A Send Data Async + To SPOC

SD‑ 24 A Send Data Async ‑ To SPOC

BLCMD1 17 A Bi-level/Pulse Command 1

BLCMD2 18 A Bi-level/Pulse Command 2

BLCMD3 19 A Bi-Level/Pulse Command 3

BLCMD4 20 A Bi-level Cmd 4/Open Close MDALID

SCMDCLK 10 A Serial Command Clock (Note 11)

SCMDENV 11 A Serial Command Envelope (Note 11)

SCMDDAT 12 A Serial Command Data (Note 11)

GMTMIN 40 A GMT/MET One-Minute Pulse

IRIGGMT+ 30 A IRIG‑B GMT (MET) +

IRIGGMT‑ 31 A IRIG‑B GMT (MET)‑

FRMGND 49 A FRAME GROUND

KUMRCLK+ 34 A Customer-Generated MR Clock +

KUMRCLK‑ 35 A MR Clock ‑

KUMRDAT+ 43 A Customer-Generated MR Data +

KUMRDAT‑ 44 A MR Data ‑

KUMRSHLD 25 A Shield For Ku Signals

UNDTSP1+ 61 D Undedicated TSP 1 + (Optional Video +)

UNDTSP1‑ 66 D Undedicated TSP 1 ‑ (Optional Video -)

UNDTSPS1 54 A Shield For Undedicated TSP 1

UNDTSP2+ 62 D Undedicated TSP 2 +

UNDTSP2‑ 63 D Undedicated TSP ‑

UNDTSPS2 55 A Shield For Undedicated TSP 2

[Table 2.5 Continued]{.smallcaps}

**[ID]{.underline} [Pin]{.underline}(Note 3) [Type]{.underline}(Note 2)
[Function]{.underline}**

UNDTSP3+ 56 A Undedicated TSP 3+

UNDTSP3‑ 57 A Undedicated TSP 3‑

UNDTSPS3 48 A Shield For Undedicated TSP 3

UND4 58 A Undedicated 4

UND5 59 A Undedicated 5

UND6 60 A Undedicated 6

UND7 64 A Undedicated 7

UND8 65 A Undedicated 8

UNDS 53 A Shield For Undedicated 4‑8

MDAOC 52 A MDA Door Open/Close SIG To MDA

SW-6 NO 26 E MDA Door Open Switch S6, Normally

Open (Note 9)

SW-6 C 27 E MDA Door Open Switch S6, Center Contact

SW-6 NC 28 E MDA Door Open Switch S6, Normally Closed

SW-5 NO 36 E MDA Door Open Switch S5, Normally Open

SW-5 C 37 E MDA Door Open Switch S5, Center Contact

SW-5 NC 38 E MDA Door Open Switch S5, Normally

Closed

**[Safe/Arm Connector P3:]{.underline} (Note 10)**

PYRO 1 PWR A B \-\--

PYRO 1 RET B B \-\--

PYRO 1 PWR (DEV) G B \-\--

PYRO 1 RET (DEV) R B \-\--

PYRO 2 PWR N B \-\--

PYRO 2 RET C B \-\--

PYRO 2 PWR (DEV) J B \-\--

PYRO 2 RET (DEV) H B \-\--

PYRO 3 PWR P B \-\--

PYRO 3 RET D B \-\--

PYRO 3 PWR (DEV) L B \-\--

PYRO 3 RET (DEV) K B \-\--

PYRO 4 PWR F B \-\--

PYRO 4 RET E B \-\--

PYRO 4 PWR (DEV) M B \-\--

PYRO 4 RTN (DEV) S B \-\--

Note 1: Power Return Pins B, D, And F May Be Connected Together Within
Payload

Note 2: Wire Type Designation:

A 22 GA

B 16 GA

C 12 GA

D 26 GA

E 24 GA

F 20 GA

[Table 2.5 Continued]{.smallcaps}

Note 3: Customer will make no connections to unused pins

Note 4: The designations \"P1\" and \"P2\" in this table indicate the
pin-out for a cable-mounted connector. A canister experiment would need
this termination to interface to the canister baseplate connector
(designated as \"J1\" and \"J2\"). The pinouts are identical for either
\"J\" or \"P\" designated connectors. Connector pair J3/P3 is a safe and
arm connector whose use is not a standard service. The pin-out is not
included.

Note 5: 28v b power circuit shared with MDA motors ‑ may contain excess
EMI during door motor operation.

Note 6: Thermistor 1 is located on canister bottom plate

Note 7: Pin 16 (MDA door position) may only be connected to
high-resistance (100 k ohms) load within payload if MDA is flown

Note 8: pin 20 BLCMD 4 to be connected to pin 52 (MDA open/close
control) unless payload has other provision for generating 28v 10MA
signal to open door (if MDA is flown).

Note 9: When door is fully opened, normally open contact is shorted to
center contact. When door is closed, normally closed contact is shorted
to center contact.

Note 10: Safe/arm connector is currently configured as a feed through,
from outside

> Canister to experiment.

Note 11: These services are no longer offered.

[]{#__RefHeading___Toc456763655 .anchor}Table 2.6 Circuit Protection
Requirements

  ----------------------- ----------------------- -----------------------
  Min. Wire Gauge         Max. Fuse Size (A)      Max. Load (A)

  26                      3                       1.5

  24                      5                       2.5

  22                      6                       3.0

  20                      7.5                     3.75

  18                      10                      5.0

  16                      12.5                    6.25

  14                      15                      7.5

  12                      25                      12.5

  10                      30                      15
  ----------------------- ----------------------- -----------------------

Six electrical interfaces are provided via six standard sets of cables
and connectors. Two additional sets are reserved for system use. These
provide up to 500W of 28VDC power to each interface and 50W of
\"Survival Heater Power.\" In addition to providing this type of
interface during on-orbit operations, the HH has provisions for a
transparent bi-directional data path between the customer\'s payload and
the Customer Ground Support Equipment (CGSE). This type of interface
allows the customer to maintain autonomous control over his/her payload.

The characteristics of the power will be the same as Orbiter power
except for higher source resistance due to the added carrier wiring. It
is important to note that, while power is switched to each experiment
through the HH avionics, no EMI filtering is provided. Customers will
see the EMI environment specified in Appendix H and are expected to meet
all EMI requirements by providing filtering with each experiment. Each
power interface will consist of 28 VDC +/- 4 VDC power supplied via dual
12 gauge 10A circuits. Each of the dual circuits can be switched in
through independent contacts of a Double-Pole Single Throw (DPST) relay
(Figure 2.38). Each power interface will have independent current
measurement capability.

### DC Power Ripple and Transient Limits (For Payload Main Circuit Only)

See Appendix H of this document.

[]{#__RefHeading___Toc456763656 .anchor}Table 2.7 Customer Electrical
Interfaces And Service Summary

1\. 28 VDC (+/- 4 VDC) Power (Dual 10A Circuits)

2\. Asynchronous Interface (Bi-Directional, 1200 Baud)

3\. Serial Command (Clock/Data/Envelope) can also function as Individual
Bi-Level 0, +5v Commands (3 Each)

4\. Bi-Level or Pulse 0, +28v Command (4 Each)

5\. IRIG-B Met and Met One-Minute Pulse

6.  Medium-Rate Ku-Band Data (16 Kb - 1.4 Mb/S Total,

> Clock/Data Interface)

Items 2, 3, 4, and 6 can be interfaced to customer GSE

Items 2 and 6 are \"Transparent\" interfaces

[]{#__RefHeading___Toc456763657 .anchor}Table 2.8 Hitchhiker Electrical
Accommodations

  ------------------------------ ---------------- -----------------------
                                 Total HH and     Single Customer Payload
                                 Customer         Port Max
                                 Payloads Max     

  Power (28 +/- 4DC)             1300W            500w

  Energy (KWH)                   60               10 (Note 2)

  Low-Rate Downlink              6000 B/S         960 B/S (Note 1)

  Medium-Rate Downlink           1.4 Mb/S         1.4 Mb/S (Note 3)

  Serial Command Channels        6                1 (Note 4)

  Bi-Level Commands              24               4
  ------------------------------ ---------------- -----------------------

> Note 1: Nominal Information Rate Of One Standard Asynchronous Channel.
> Any Combination Of Five 1.2k Baud Channels May Be Downlinked
> Simultaneously.

Note 2: Nominal 1/6 Allocation.

Note 3: By Mission Requirements.

Note 4: These Services Are No Longer Offered.

![](media/image37.png){width="6.292361111111111in"
height="8.079166666666667in"}

[]{#__RefHeading___Toc457875877 .anchor}Figure 2.37 Customer Power
Interface

In addition to the two 10-amp power lines, one 2.5-amp heater line is
available at each power port. Heater service is controlled via a single
relay for multiple customer ports. Therefore, power to this line shall
be assumed ON for the duration of the flight. It is recommended that
customers included internal (e.g., thermostatic) switching for this
service.

![](media/image38.png){width="6.290277777777778in"
height="7.396527777777778in"}

[]{#__RefHeading___Toc457875878 .anchor}Figure 2.38 Hitchhiker Avionics
Unit -- Power Distribution

### Thermal Power Characteristics

The thermistor characteristics that accomplish thermal control are
specified in section 2.2.6.

### Signal Characteristics

This data is available to the customer either in real-time or post-fight
when specified as a requirement. Figure 2.40 provides a schematic
drawing of the HH-S customer power interface. Customer signal ground
must be connected to chassis (case). As shown in Figure 2.48, 28v return
must be used for the bi-level return. The customer 28v return must be
isolated from both signal ground and chassis (case) by a minimum
resistance of 1M ohm. This requirement cannot be waived.

Tables 2.7 and 2.8 provide the detailed characteristics of the
electrical system interfaces. A switch panel is used for carrier and
experiment power activation and de-activation and may be used to provide
a safety inhibit to a customer\'s hazardous function if required.

### Standard Connectors for Customers

In choosing connectors for experiment internal wiring harnesses, it is
highly recommended that the selection be limited to the MIL-C-38999
series I, II, or III or other space flight approved connectors. In the
cases where GSFC is to supply the cables and harnesses as a service to
the customer or where the connectors are otherwise specified within this
document, the selection of connectors must be made from MIL-C-38999 to
minimize cost and schedule impacts. GSFC will not be responsible for
supplying connectors outside this specification. Sources of supply are
as follows:

ITT Cannon

666 E. Dyer Road

P.O. Box 929

Santa Ana, CA 92702-0929

Amphenol Corporation

Bendix Connector Operations

40-60 Delaware Avenue

Sidney, NY 13838-1395

Matrix Sciences

365 Maple Avenue

Torrence, CA 90503

A detailed specification for this series of connectors may be obtained
through the GSFC library or through the GSFC Code 300 library. Specific
information regarding the manufacturer part numbering, cost,
availability, etc. may be obtained from the above sources or through the
GSFC electrical engineer assigned to the project.

### Shield Grounding

In order to maintain the EMC of the Hitchhiker and its customer, the
following shielding practices will be used.

Refer to Figure 2.40. All logic level signals and analog signals
excluding video and RF shall have their shields grounded to the signal
ground at the sending end only. Signal returns will be routed in the
same bundle as the associated signal lines in order to minimize
electromagnetic emission and susceptibility.

![](media/image39.png){width="5.46875in" height="1.2458333333333333in"}

a.  Logic Level signal shield practice

[]{#__RefHeading___Toc457875879 .anchor}Figure 2.39 Digital Signal
Shield

![](media/image40.png){width="5.385416666666667in" height="1.59375in"}

b.  Analog shielding practice

[]{#__RefHeading___Toc457875880 .anchor}Figure 2.40 Shield Grounding of
Logic Level and Analog Signals

All lines which carry significant current transitions while displaying
"clean" constant voltages will be electromagnetically shielded (both
ends grounded). Typically this will occur on power lines and the shields
shall be grounded to chassis in these cases. Power distribution shall be
through twisted pairs of wires in bundles separate from other signals.
Refer to Figure 2.41.

![](media/image41.png){width="4.5in" height="1.4375in"}

[]{#__RefHeading___Toc457875881 .anchor}Figure 2.41 Shield Grounding of
Power Line

All lines which carry significant current and voltage transitions will
be double shielded with an electrostatic shield (sending end grounded)
and an electromagnetic shield (both ends grounded to chassis). Refer to
Figure 2.42. This will occur on relay drive signals typically.

![](media/image42.png){width="5.177083333333333in" height="2.15625in"}

[]{#__RefHeading___Toc457875882 .anchor}Figure 2.42 Double Shielding
Significantly Varying Current and Voltage Lines

## Command And Communication Support System

### Transparent Data System

Figures 2.43 through 2.47 illustrate the transparent data system
available to the customer through HH. The figures present the command,
low-rate and medium rate data flows. The data communications interface
generally remains unchanged from the customer\'s point of view
independent of whether the payload is at the customer\'s facility, at
the integration facility, or during flight operations. Some ground data
processing functions may have optional service charges for reimbursable
customers. Contact the Project Office for details.

[]{#__RefHeading___Toc457875883 .anchor}Figure 2.43 Hitchhiker
Transparent Data System

**Hitchhiker Command Flow**

[]{#__RefHeading___Toc457875884 .anchor}Figure 2.44 Hitchhiker Command
Flow

![](media/image43.png){width="5.152083333333334in"
height="7.9215277777777775in"}

[]{#__RefHeading___Toc457875885 .anchor}Figure 2.45 Hitchhiker Low Rate
Data Flow

![](media/image44.png){width="5.76875in" height="8.494444444444444in"}

[]{#__RefHeading___Toc457875886 .anchor}Figure 2.46 Hitchhiker Medium
Rate Data Flow

**Hitchhiker Signal Port to Customer Interface**

![](media/image45.png){width="5.675694444444445in"
height="7.179166666666666in"}

[]{#__RefHeading___Toc457875887 .anchor}Figure 2.47 Hitchhiker Signal
Port to Customer Interface

### Bi-Level Command System

Signals that traverse the bi-level command interface may be set to ØV
(false) or +28V (+19.5 to +32V) (true), or may be pulsed from false to
true and back to false. There are four bi-level signals per interface.
Figure 2.48 illustrates the customer bi-level command interface while
Figures 2.49 and 2.50 show the command formats. Only one of the four
signals may be affected by any one command. Bi-level commands can be
sent either via ACCESS or CGSE.

![](media/image46.png)

[]{#__RefHeading___Toc457875888 .anchor}Figure 2.48 Customer Bi-Level
Command Interface

![](media/image47.png){width="6.291666666666667in"
height="7.954861111111111in"}

[]{#__RefHeading___Toc457875889 .anchor}Figure 2.49 Customer Message
Format for 28 Volt Bi-Level Commands

![](media/image48.png){width="5.584027777777778in"
height="8.202777777777778in"}

[]{#__RefHeading___Toc457875890 .anchor}Figure 2.50 Customer Message
Format for 28 Volt Pulse Commands

### Asynchronous Uplink

The asynchronous uplink is used to transmit customer asynchronous
command messages and Mission Elapsed Time (MET) messages to the payload.
All commands issued by the CGSE have the general format shown in Figure
2.51

The customer message format for asynchronous commands is shown in Figure
2.52. The format of the asynchronous MET message is shown in Figure
2.53. The format of the synchronize to MET command is shown on Figure
2.54 One receive data (RD) signal is available through each HH port.

The interface operates at 1200 baud asynchronous data rate. The signal
format is shown in Figure 2.55 where each signal contains one start bit,
eight data bits (no parity), and one stop bit. The uplink messages may
originate from the ACCESS or from CGSE. The transport delay between CGSE
and the customer\'s payload is nominally 2 to 20 seconds. The transport
delays are due to latencies introduced by the number of CGSEs issuing
commands, the networks, JSC Mission Control Center (MCC) and uplink
delays. The delay does not account for retrying a command because of
command uplink failure.

![](media/image49.png){width="6.144444444444445in"
height="6.9222222222222225in"}

[]{#__RefHeading___Toc457875891 .anchor}Figure 2.51 Customer
Asynchronous Message Format -- General

![](media/image50.png){width="6.298611111111111in"
height="7.3597222222222225in"}

[]{#__RefHeading___Toc457875892 .anchor}Figure 2.52 Customer Format for
Asynchronous Commands

![](media/image51.png){width="6.2868055555555555in"
height="8.256944444444445in"}

[]{#__RefHeading___Toc457875893 .anchor}Figure 2.53 Customer Message For
MET

![](media/image52.png){width="6.448611111111111in"
height="6.715972222222222in"}

[]{#__RefHeading___Toc457875894 .anchor}Figure 2.54 Customer Message
Format for Synchronized MET

![](media/image53.png){width="5.9in" height="7.4534722222222225in"}

[]{#__RefHeading___Toc457875895 .anchor}Figure 2.55 Customer
Asynchronous RD Interface

### Asynchronous Downlink

One Asynchronous Send Data (SD) signal per interface that operates at
1200-baud asynchronous and has a similar message pattern (one bit start,
8 data bits, and one stop bit) as the uplink interface is available
through the HH interface. (See Figure 2.56).

The downlink can support continuous 1200-baud transmission which will be
routed to the customer\'s GSE via the ACCESS to CGSE interfaces.
Downlink messages do not have a format requirement. Nominally, the
transport delay between customer payload and customer GSE is 5 to 15
seconds. The standard HH avionics arrangement can simultaneously
downlink any 5 of the 8 available asynchronous downlink channels. These
channels are selectable via ground system commands from the ACCESS.

![](media/image54.png){width="6.108333333333333in"
height="7.475694444444445in"}

[]{#__RefHeading___Toc457875896 .anchor}Figure 2.56 Customer
Asynchronous SD Interface

### Medium-Rate Ku-Band Downlink

The carrier contains a Medium-rate Multiplexer (MRM) capable of
multiplexing up to six simultaneous customer-provided serial‑bit
non‑return to zero (NRZ) data signals into a single serial 2Mb/s
bit‑stream for transmission via channel 2 of the Orbiter Ku‑band
Tracking and Data Relay Satellite System (TDRSS) signal processing
system. The combined simultaneous input rate to the MRM from all HH
experiments cannot exceed 1.4 Mb/s. This effectively limits customer
downlink rates if the MRM is accepting data from more than one source.
As previously shown in Figure 2.45, channel 2 is not available for
exclusive use of HH data but is shared with dumping of the Orbiter\'s
tape recorder and the payload interrogator. In addition, use of the
medium-rate system requires the TDRSS as well as deployment and pointing
of a steerable antenna on the Orbiter which cannot be used in certain
attitudes or orbit positions. In general, Ku‑band medium-rate service
should be available approximately 50 percent of the time during a
typical flight.

Medium-rate data accommodations will be allocated by the SSPP on a
case-by-case basis. This allocation will depend on several factors,
including experiment data rate, mission timeline, and the requirements
of other co-manifested experiments. The maximum data rate per user
channel is 880 kbps. If conflicts exist between several medium-rate
users, then medium-rate data output must be controllable via CGSE ground
command.

Each customer-supplied input data stream must be continuous and stable
within 1 percent of its assigned data rate during the customer's
data-take periods. If the customer's data is discontinuous or
event-oriented, the customer may elect to have the clock stop between
periods of valid data, or may elect to transmit continuous clock but
discontinue transmitting valid data.

It is recommended that each valid period be preceded by at least 4 data
frames of leader telemetry prior to the first frame of required data.
This is needed in order to ensure that the ACCESS ground data system has
sufficient time to sync on the composite downlink signal during mission.
Each data period must be followed by at least 66 bytes of clock to flush
the customer data buffer in the MRM.

Customer data during valid data periods must consist of a continuous
series of data frames each containing a fixed integral multiple of 8
bits but no more than 8,192 bits. Each data frame must contain a fixed
synchronization pattern of at least 24 bits to be specified by the
customer. The pattern FAF320 (hexadecimal, most significant bit and byte
first) is recommended but may be customer selected. The remaining format
of the data frames can be determined by the customer as desired;
however, the following considerations should be taken into account. Each
data frame should contain a frame number that does not repeat for at
least 256 frames, as well as time information adequate for the
customer's needs; it should also contain provision for error detection
if necessary to meet the customer' goals.

During testing and flight operations, the Medium Rate Demultiplexer Unit
(MRDU), referenced in Figure 2.46, will decommutate the multiplexed
signal and regenerate the customer\'s clock and data for use by the
CGSE. This data interface is shown in Table 2.12. The clock will
generally be at a slightly higher bit rate than the onboard customer
supplied clock. The ground clock and data will stop momentarily
periodically to equalize the average data rate.

The data bit error rate is expected to be generally no worse than
10^‑5^; however, there will be periods of dropout and deteriorated data
especially near the ends of TDRSS coverage periods. The data delay will
be several hundred bytes plus approximately 2 seconds. The CGSE must be
designed to obtain and maintain synchronization and otherwise operate in
a satisfactory manner under these conditions.

The electrical interfaces and timing for the medium-rate system are
shown in Figures 2.57, 2.58 and 2.59. Data return on the ground can be
either by NRZ‑L serial data and clock interface identical to Figures
2.58 and 2.59 or post mission by Compact Disc (CD). The CD format is
shown in Appendix C and will be frame synchronized data sets if the
customer uses a fixed-frame length. GSFC engineers can assist customers
in the design of prospective medium rate (MR) telemetry formats. Again,
the customer\'s medium-rate ground data interface is shown in Table
2.12.

![](media/image55.png)

[]{#__RefHeading___Toc457875897 .anchor}Figure 2.57 Medium Rate Customer
Interface

![](media/image56.png){width="6.151388888888889in"
height="6.729166666666667in"}

[]{#__RefHeading___Toc457875898 .anchor}Figure 2.58 Medium Rate Customer
Data

[]{.mark}

![](media/image57.png){width="6.55in" height="5.403472222222222in"}

[]{#__RefHeading___Toc457875899 .anchor}Figure 2.59 Medium Rate Customer
Clock

[]{.mark}

### Analog Data

One analog data line is provided in each standard interface. This line
is sampled at a rate of approximately 15 Hz. Voltages in the range of
‑0.06 to 5.04 volts are converted to 8-bit values (00 and FF,
respectively). Voltages slightly below ‑0.06 or above 5.04 volts will be
transmitted as 00 or FF (i.e., no foldover occurs). An index pulse on a
separate wire occurs once per sample and can be used to advance a
customer-supplied analog multiplexer to allow multiple parameters to be
sampled over the single analog line. Several (typically three) of the
multiplexer\'s inputs should be connected to known fixed voltages (e.g.,
+5.10, zero, +2.50) to allow the customer\'s ground equipment to
determine synchronization with the returned sample sequence. Analog
interfaces are shown in Figure 2.60.

![](media/image58.png){width="6.243055555555555in"
height="8.223611111111111in"}

[]{#__RefHeading___Toc457875900 .anchor}Figure 2.60 Customer Analog Data
Interfaces

### Temperature Data

As provided in each interface, three additional analog data lines
(Figure 2.33) are sampled at approximately .5 Hz (‑0.06 ‑ +5.04v, 8
bits) and are provided with a regulated power source and resistor
network. These are intended for connection to YSI 44006 (see Section
2.2.2) thermistors to be supplied by GSFC and installed inside the
customer\'s flight equipment by the customer. These networks and
thermistors allow temperatures in the range of ‑20 to +60 degrees C to
be measured without requiring the customer equipment to be operating. If
all the thermistor lines are not required for temperatures, they may be
used by the customer to measure other parameters such as: canister
temperature, bottom plate temperature, canister pressure, and door
position (if door is present).

### Inter-Range Instrumentation Group, Type B (IRIG-B) MET Signal

Orbiter MET in IRIG‑B format will be distributed to each interface. This
signal is maintained to within 10 milliseconds (ms) and consists of a
100 Pulse Per Second (PPS) Pulse-Width-Type PCM signal giving days,
hours, minutes, and seconds, once each second. In addition, there will
be a MET minute signal; Transistor-Transistor Logic (TTL) levels,
nominal square wave 1 ppm; edges traceable to MET within 10 ms. The
customer timing interface is shown in Figure 2.60. Greenwich Mean Time
(GMT) may be used in place of MET on some HH missions.

Real-time data transmitted to customer\'s GSE can usually be tagged by
the customer\'s software to within 10 seconds. Therefore no time signals
may be necessary at the customer\'s payload if time knowledge to within
10 seconds is adequate. If it is necessary to have time knowledge within
the customer\'s payload, the MET minute signal can be used to reset a
customer one-minute clock to 10 milliseconds accuracy. If the customer
is using the asynchronous command channel, day-hour-minute-second time
may be sent to the customer\'s payload periodically to update an
on-board clock to within 3 seconds. This may be used in conjunction with
the above minute pulse to obtain maximum accuracy. The IRIG time signal
may also be decoded to obtain day-hour-minute-second time to within 10
milliseconds but is recommended only for existing designs because of the
larger number of electronic parts required for decoding.

The signal characteristics of this interface are described in paragraph
8.2.10 of JSC 07700 Vol. XIV Attachment 1 OICD 2‑19001) [SHUTTLE
ORBITER/CARGO STANDARD INTERFACES,]{.underline} This paragraph follows.

> \[8.2.10.1.1\] GMT (in HH Application, MET). The absolute time data,
> at any given time during a seven‑day mission, shall not deviate by
> more than +/‑ 10 milliseconds from the groundstation MET Reference
> Time Standard and shall be synchronized with the ground MET at certain
> times during a mission, subject to mission procedural constraints to
> prevent ring unacceptable time base perturbations. The accuracy of
> these time updates shall be +/‑ 5 milliseconds. The Master Timing Unit
> (MTU) frequency offset and drift rates shall constrain the time error
> growth rate to a maximum of +/‑ 10 milliseconds per 24 hours.

The MET output format is modified IRIG‑B as shown in Figure 2.62. The
electrical interface characteristics are shown in Figure 2.61.

![](media/image59.png){width="5.997916666666667in"
height="8.147222222222222in"}

[]{#__RefHeading___Toc457875901 .anchor}

Figure 2.61 Customer Interfaces for Time

![](media/image60.png){width="5.954861111111111in" height="8.275in"}

[]{#__RefHeading___Toc457875902 .anchor}Figure 2.62 MET Output Format

### ACCESS/CGSE Interface

Overall communication between the customer\'s payload and their ground
support equipment are shown in Figure 2.63. The ACCESS provides the
customer with (1) the command interface between the CGSE and the
customer payload, (2) low-rate customer payload data as telemetered by
the HH avionics, and (3) Orbiter ancillary data. The ACCESS provides two
asynchronous data lines for these purposes.

The Advanced Carrier Customer Equipment Support System (ACCESS) is a
Pentium PC-based, networked system that allows customers to receive
telemetry from and send commands to their experiment during Integration
and Test (I&T) and mission operations. The ACCESS system consists of the
User Interface Unit (UIU) and the Carrier Interface Unit (CIU) and the
Medium Rate Demultiplexer Unit (MRDU). Figures 2.63 and 2.64 illustrate
the Hitchhiker ACCESS system. ACCESS can also provide data displays for
each customer and thermal plotting capabilities.

The UIU is the main console for the system operator. Its overall
function is to ingest low rate telemetry packets via the network from
the CIU and distribute user packets via the ARNET RS232/RS422 ports. It
allows the operator to send various directives and commands to control
the different UIU and CIU processes as well as control of the HH
Carrier. The UIU also allows the operator to view numerous pages that
monitor the health and safety for the customer payload, such as the
current and temperatures. The UIU also performs hazardous command checks
and telemetry limit checking. The UIU is also responsible for ingesting
users commands via RS232/RS422 serial ports and sending the command
packets to the CIU for output to the carrier.

The CIU is responsible for ingesting low rate telemetry from the HH
carrier in the form of minor frames (I&T) or NASCOM blocks (mission),
decommutating the data into subcom frames, and creating user data
packets for distribution through the UIU to the customer. The CIU is
also responsible for transmitting the commands to the avionics in I&T
format (ground testing) or NASCOM format (mission operations). The CIU
acts as a front end for the UIU.

The MRDU is a stand-alone medium rate processing system that ingests the
2MB composite data stream from the NASA Communications network (NASCOM),
demultiplexes the customer medium rate data, and distributes that
customer data via an RS422 interface to the CGSE. The MRDU is also
responsible for archiving the 2MB composite data stream for use in
creating the post-mission customer data products.

The ACCESS also has the capability of providing a real-time Data Display
Unit (DDU) for each customer's use during a HH mission. The DDU's are
stand-alone Windows-based PC's that display HH avionics health and
safety data, as well as thermistor temperatures, customer data streams,
and other telemetry and command status information. The pages displayed
on the DDU contain the same information used by the ACCESS operators to
monitor the HH avionics.

The thermal plotting capability is contained in a stand-alone
workstation monitored by a thermal engineer during all HH missions. The
system provides real time monitoring and near real time plots of the HH
avionics and customer temperatures.

The following sections define the electrical interfaces supported by the
ACCESS and the data transferred between the ACCESS and the CGSE.

Hitchhiker/Customer Communications

![](media/image61.wmf)

[]{#__RefHeading___Toc457875903 .anchor}Figure 2.63 Hitchhiker/Customer
Communications

**Advanced Carrier Customer Equipment Support System (ACCESS**)

Low Rate Data Processing

![](media/image62.wmf)

[]{#__RefHeading___Toc457875904 .anchor}Figure 2.64 ACCESS Low Rate Data
Processing

Advanced Carrier Customer Equipment Support System (ACCESS)

**Medium Rate Data Processing Unit (MRDU)**

![](media/image63.wmf)

[]{#__RefHeading___Toc457875905 .anchor}Figure 2.65 ACCESS Medium Rate
Data Processing Unit

#### ACCESS‑CGSE Physical Interface Requirements. 

The asynchronous interfaces for customer unformatted payload telemetry
(type 2) data and command generation are RS-232 or RS-422 compatible.
These interfaces are full duplex with an ACCESS receive side for CGSE
command messages and an ACCESS send side for transmitting customer data
to the customer CGSE. One line (either RS-232 or RS-422) is assigned per
customer ID (CID). The default data rate is 1200 baud (see Table 2.9 for
additional line rates and information).

The asynchronous interfaces provided for HH ancillary data (type 4),
formatted payload data (type 2), Shuttle orbit and attitude data (CAS --
type 10), Analog data (type 3), Command Completion status messages (type
5), and Command Link status messages (type 6) are RS-232 compatible.
These interfaces are half duplex and are not nominally used for command
messages. The default rate is 19200 baud (see Table 2.9 for additional
information).

A summary of the RS-232-C and RS-422 lines and their characteristics are
presented in Table 2.9. The RS-232-C and RS-422 connector types and pin
assignments are shown in Tables 2.10 and 2.11 respectively.

The interface for customer medium rate payload telemetry is RS-422
compatible. One line is assigned per customer ID (CID). The data rate is
dependent on the number of customers using the HH avionics medium rate
capability up to a combined rate of 1.2 Mb.

The medium rate connectors and pin assignments are shown in Table 2.12.
A more detailed explanation of the telemetry and command interfaces are
provided in the following sections.

[]{#__RefHeading___Toc456763658 .anchor}Table 2.9 ACCESS ‑ CGSE
Communications Line

**[Line \#]{.underline} [Line Characteristics]{.underline}
[Function]{.underline} [Comments]{.underline}**

1 Full Duplex, 1200 Access Receive Side: 1 Line Per CID

Baud, No Echo, 1 CGSE Command Messages

Start, 1 Stop, No

Parity, RS422 Access Send Side:

Or RS232 Raw Payload Data From

Avionics Asynchronous Send

Data Port.

2 Half Duplex, 19.2k Multiplexed Data 1 Line Per CID

Baud, No Echo, 1 Messages Of Any Of The

Start, 1 Stop, No Following Types:

Parity, 8 Bit Data

RS232 2 - Customer Async Data If Utilization Rate

3 -- Customer Analog Data Exceeds 75% Of

4 -- HH Ancillary Data Baud Rate, A Second

5 -- Customer Command Completion Line Will Be

6 - Customer Command Link Status Required

10 - Shuttle Ancillary Data (Orbit/Attitude)

14 - Customer PCM-B Data

15 - Customer PCM-A Data

[]{#__RefHeading___Toc456763659 .anchor}Table 2.10 Pin Designation For
RS-232 Asynchronous Data

(ACCESS to CGSE)

[]{#__RefHeading___Toc456763660 .anchor}Serial Formatted Data

Unformatted Data

Avionics Ancillary Data

STS Orbit/Ancillary Data

Serial Command Messages (CGSE to ACCESS)

  ----------------------------- -----------------------------------------
  **[PIN Number]{.underline}**  **[Function (Access)]{.underline}**

  1                             Frame Ground (FG)

  2                             Transmit Data (TD)

  3                             Received Data (RD)

  4-6                           N/C

  7                             Signal Ground (SG)

  8-25                          N/C
  ----------------------------- -----------------------------------------

The Serial Interface Circuit will use the "Null Modem" configuration,
shown in Figure below.

![](media/image64.png){width="6.498611111111111in"
height="2.3979166666666667in"}

[]{#__RefHeading___Toc456763661 .anchor}Table 2.11 Pin Designation for
RS-422 Asynchronous Data

(ACCESS to CGSE)

Serial Formatted Data

Formatted Data

Serial Command Messages (CGSE to ACCESS)

  ----------------------- ---------------------------- ----------------------------
  **[Pin                  **[Function]{.underline}**   **[Comments]{.underline}**
  Number]{.underline}**                                

  1                       Frame Ground                 Connector Type-

  2                       (+) Transmit Data            25-Pin Male

  3                       Signal Ground                Suggested Part

  4                       (-) Transmit Data            Sources

  5                       Signal Ground                (Male Connector)

  6                       (+) Receive Data             1\. AMPHENOL

  7                       Signal Ground                P/N 0325PV

  8                       (-) Receive Data             2\. TRW "Cinch"

  9                       Signal Ground                P/N DB-25P

  10-25                   N/C                          or MIL-SPEC

                                                       M24308/4-3
  ----------------------- ---------------------------- ----------------------------

![](media/image65.png){width="4.626388888888889in"
height="2.8965277777777776in"}

[]{#__RefHeading___Toc456763662 .anchor}Table 2.12 Pin Designation For
Customer RS-422 Medium Rate Data

Ground Data Interface

[]{#__RefHeading___Toc456763663 .anchor}(ACCESS to CGSE)

![](media/image66.png)

#### ACCESS‑CGSE Telemetry Interface

The ACCESS can provide HH avionics telemetry and asynchronous payload
telemetry to the CGSE. No data interpretation or conversions are
performed by the ACCESS. All data of a given type are transferred in a
time-sequential order. The following sub-sections describe the format of
the data transferred.

1\. Unformatted Customer Payload Asynchronous Downlink Data (Type 2)

The customer will receive the asynchronous payload telemetry in near
real-time in a \"transparent\" manner. The data are bursted to the CGSE
over a dedicated 1200-baud asynchronous telemetry/command line (RS-232-C
or RS422) without any framing, as they are received by the ACCESS. No
attempt is made to synchronize this stream with any other data stream or
to maintain the data sampling timing relationship within a stream.

2\. Formatted Customer Asynchronous Downlink Payload Data (Type 2)

The ACCESS formatted messages contain a maximum of 120 bytes of payload
data and contain the HH time code of the telemetry frame containing the
last data byte transmitted within the message. This data message format
is shown in Table 2.13. The ACCESS schedules transmission of these
blocks upon the filling of the data fields within the message or after
one second if the message is not empty. If these messages are
multiplexed with other message blocks, the timing between messages is
erratic. Note that it is possible to receive a block with \"no data
bytes\" if a sync error is encountered.

The customer will receive the formatted asynchronous payload data in
near real time over an ACCESS/CGSE line. The electrical interface is
nominally a 19.2 baud RS-232-C data line. The ACCESS will place the
payload data into individual messages. No attempt is made to synchronize
the data within the messages.

The ACCESS can also send the HH avionics ancillary data, customer energy
data, analog data, command acknowledgments, and a subset of the Shuttle
orbit and attitude data multiplexed with the formatted asynchronous
payload data.

The aggregate data rate of all the multiplexed data (including overhead)
must not exceed 75 percent of the data line baud rate. Whenever the data
rates are predicted to exceed the 75 percent threshold, another RS-232-C
line will be provided. In this case, the assignment of data types
transferred over each line will be negotiated with the Project. The user
may reconstruct each data stream by grouping data of similar types.

[]{#__RefHeading___Toc456763664 .anchor}Table 2.13 Access Formatted
Asynchronous Data Message Structure

**[Byte]{.underline} [Bits]{.underline} [Function]{.underline}
[Content]{.underline}**

1 1‑8 Synchronization E5 (Base 16)

2 1‑8 Number of data bytes 0 [\<]{.underline} N [\<]{.underline} 120

in message

3 1‑4 Customer Identification 1 [\<]{.underline} CID [\<]{.underline} 8

(CID)

3 5‑8 Message type 2

4‑5 1‑8/1‑8 Binary day of MET from 0 [\<]{.underline} DD
[\<]{.underline} 366

Avionics PCM frame containing

last payload data byte

(DD)

6‑9 1‑8/1‑8 Milliseconds of day from 0 [\<]{.underline} M
[\<]{.underline} 86399999

Avionics PCM frame containing

last payload data byte.

Treated as a 32‑bit integer (M)

10 1 Avionics minor frame sync loss 0/1

indicator 1 = sync loss during

data collection

10 2 MCU frame sync loss 0/1

indicator 1 = sync loss

during data collection

10 3 MCU encountered data 0/1

overrun if set to 1

10 4 MCU encountered parity 0/1

error if set to 1

10 5-8 Spare 0\'S

10+N 1-8 Payload data 0-255

11+N 1-8 Exclusive OR of bytes 0-255

2 through (N+10)

3\. Customer Analog Data (Type 3)

The customer may receive data from its analog channel assigned by the HH
mission. The ACCESS formats the data into message blocks as shown in
Table 2.14. The data are tagged with the HH time code (MET) of the minor
frame containing the last byte of user data transmitted within the
message. No attempt is made to synchronize the data within the sequence
of analog samples. This message is scheduled for transmission to the
CGSE every HH major frame. It is multiplexed with other ancillary and
command acknowledgment messages, hence the timing between the messages
is erratic. However, the time for messages of the same time is in
ascending order.

[]{#__RefHeading___Toc456763665 .anchor}Table 2.14 Access Formatted
Payload Analog Data Structure

**[Byte]{.underline} [Bits]{.underline} [Function]{.underline}
[Value]{.underline}**

1 1‑8 Synchronization E5(Base 16)

2 1‑8 Number of data bytes 32

in message

3 1‑4 Customer Identification 1 [\<]{.underline} CID [\<]{.underline} 8

(CID)

3 5‑8 Message type 3

4‑5 1‑8/1‑8 Binary day of year from 0 [\<]{.underline} DD
[\<]{.underline} 366

Avionics PCM frame containing

last byte of multiplexer

data transferred (DD)

6‑9 1‑8/1‑8/ Milliseconds of day from 0 [\<]{.underline} M
[\<]{.underline} 86399999

1-8/1-8 Avionics PCM frame containing

last byte of analog

data transferred (M)

10 1 Avionics minor frame sync loss 0/1

during data collection if set

10 2‑8 Spare 0

11‑42 1‑8 Analog data 0‑255

43 1‑8 Exclusive OR of bytes 2-42 0‑255

4\. HH Ancillary Data Message (Type 4)

The ACCESS will provide HH avionics ancillary data messages which
contain information such as the payload temperatures, relay states,
current load, user analog data, and energy usage. The frequency and
content of this message is dependent upon the mission-unique HH
telemetry format. Currently, the message is transmitted approximately
once every 4 seconds assuming a nominal 8kb/sec telemetry rate. The
format of the HH ancillary data messages is defined in Table 2.15. The
time field is the HH time code of the minor frame from which the last
data byte was sampled.

[]{#__RefHeading___Toc456763666 .anchor}Table 2.15 Access Ancillary Data
Message Structure

**[Byte]{.underline} [Bits]{.underline} [Function]{.underline}
[Content]{.underline}**

1 1-8 Synchronization E5 (Base 16)

2 1-8 Number of data bytes in 10

message

3 1-4 Customer Identification (CID) 1 [\<]{.underline} CID
[\<]{.underline} 8

3 5-8 Message type 4

4-5 1-8/1-8 Binary day of year 0 [\<]{.underline} DD [\<]{.underline}
366

6-9 1-8/1-8/ Milliseconds of day 0 [\<]{.underline} M [\<]{.underline}
86399999

1-8/1-8

10 1 HH minor frame sync loss 0/1

indicator (1=Loss)

10 2 MCU sync loss indicator 0/1

(1=Loss)

10 3 Avionics analog channel 0/1

sync loss (1=Loss)

10 4-8 Spare 0

11 1-8 Current drawn by user 0-255

in counts (as telemetered)

12 1-8 Relay status as telemetered 0-255

13 1-8 Heater bus status 0-255

14 1-8 Thermistor #1 reading in counts 0-255

15 1-8 Thermistor #2 reading in counts 0-255

16 1-8 Thermistor #3 reading in counts 0-255

17 1-8 Energy usage as computed 0-255

by MCU in counts (Sample 1)

18 1-8 Bus voltage as sampled 0-255

by MCU in counts (sample 1)

19 1-8 Energy usage as computed 0-255

by MCU in counts (sample 2)

20 1-8 Bus voltage as sampled by 0-255

MCU in counts (sample 2)

21 1-8 Exclusive OR of bytes 2-20 0-255

5\. Shuttle Orbit and Attitude Data Messages (Type 10)

The customer may receive the Shuttle orbit and attitude parameters as
they are received by the ACCESS from the Calibrated Ancillary System
(CAS) at the Johnson Space Center (JSC). No attempt is made to convert
the data values. The time field is contained in the Shuttle ancillary
data block received from the CAS. Table 2.16 depicts the default format
and content of the message. The frequency of the message is
approximately once a second. The customer may negotiate with the Project
for the inclusion of other data found in the Shuttle ancillary data
block.

Algorithms for converting the quaternions in these messages to RA/DEC of
the Z axis or orbiter R,P,Y angles are given in Appendix G.

[]{#__RefHeading___Toc456763667 .anchor}Table 2.16 Shuttle Orbit And
Attitude Data Message Structure

**[Byte]{.underline} [Bits]{.underline} [Function]{.underline}
[Value]{.underline}**

1 1‑8 Synchronization E5 (Base 16)

2 1‑8 Number of data bytes in message, 92

excluding header and checksum

3 1‑4 Customer Identification (CID) 1 [\<]{.underline} CID
[\<]{.underline} 8

3 5‑8 Message type 10

4‑5 1‑8/1‑8 Binary day of year computed from 0 [\<]{.underline} DD
[\<]{.underline} 366

Primary Source MET

6‑9 1‑8/1‑8/ Milliseconds of day computed

1-8/1-8 from Primary Source MET 0 [\<]{.underline} M [\<]{.underline}
86399999

10 Spare

11-18 All X-Component of current Shuttle

position vector in IBM floating

point. M50 coordinate system.

19-26 All Y component of current Shuttle

position vector IBM floating point.

M50 coordinate system.

27-34 All Z component of current Shuttle

position vector in IBM floating

point M50 coordinate system.

35-38 All X component of velocity vector

in IBM floating point. M50

coordinate system.

39-42 All Y-component of velocity vector

in IBM floating point. M50

coordinate system.

43-46 All Z component of velocity vector

in IBM floating point. M50

coordinate system.

Table 2.16 Continued

47-54 All Time Tag associated with current

state in IBM floating point.

55-58 All M50 to measured body quaternion

element 1 in IBM floating point

59-62 All M50 to measured body quaternion

element 2 in IBM floating point

63-66 All M50 to measured body quaternion

element 3 in IBM floating point

67-70 All M50 to measured body quaternion

element 4 in IBM floating point

71-74 All M50 WRT LVLH quaternion element 1

in IBM floating point

75-78 All M50 WRT LVLH quaternion element 2

in IBM floating point

79-82 All M50 WRT LVLH quaternion element 3

in IBM floating point

83-86 All M50 WRT LVLH Quaternion Element 4

in IBM floating point

87-102 All Vernier Jet Data

103 1-8 Exclusive OR of bytes 2-102

[Table 2.16 Continued]{.smallcaps}

VERNIER JET DATA

Bytes 87-102

Up to 16 Samples of Orbiter Vernier Thruster Data in Time Sequence

Bit 1 = 0 Valid Sample

Bit 1 = 1 Fill (No valid sample)

Bit 2 Spare

Bits 3-8 Vernier Jet Data

1 = Jet Firing

0 = Jet Not Firing

[BIT]{.underline} [JET]{.underline} [POSITION PLUME
DIRECTION]{.underline}

3 F5L FWD-Left Down/Left

4 F5R FWD- Right Down/Right

5 L5D AFT-Left Down

6 L5L AFT-Left Left

7 R5R AFT-Right Right

8 R5D AFT-Right Down

3.  ACCESS-CGSE Command Interfaces

Messages are exchanged between the ACCESS and CGSE for payload
commanding and command acknowledgment.

The ACCESS UIU will accept commands from the CGSE over a 1200 baud
RS-232-C or RS-422 interface. These commands will be screened by the
ACCESS for criticality, then transferred to the ACCESS CIU via the LAN.
Once a customer's command is received at the CIU, it is placed in a
command block, encoded in the proper format (NASCOM or I&T) and placed
into an uplink command buffer, then transmitted. The CIU will verify
that the command block was accepted by the HH avionics. A new command
block will not be transmitted until a previously transmitted command
block is verified by the HH avionics in telemetry. Commands that are not
verified within a timely manner (nominally 5 seconds for I&T, and 15
seconds during mission operations) by the HH avionics will be
retransmitted by the ACCESS operators. The command will not be released
from the ACCESS buffer until a verification has been received from the
avionics. ACCESS, however, does not monitor the telemetry to determine
if the customer payload responded to the commands.

Customer CGSE's are connected to the ACCESS via the Serial Port
Interfaces referenced in Figure 2.63. This places some limitations on
user command thru-put, especially for long "back to back" experiment
command strings.

In reference to the HH Command Flow, the following three elements apply:

1\. The presence of a 1200-baud ACCESS line does not mean that the user
can continuously pump commands at this rate. The maximum command string
length is 119 bytes. User minimum Delay Time (DT) between command
strings sent by its CGSE to the ACCESS is:

DT = (Number of active command lines) \* (400 milliseconds).

2\. The ACCESS UIU uses message queues for transferring user commands to
the ACCESS CIU via the LAN. It takes the UIU 400 milliseconds to encode
the user input command for transfer it to the CIU. It will take twice as
long, on average, to process two user input buffers. If a user does not
enforce a delay of DT milliseconds between long command strings, an
overflow can occur causing customer commands to be lost.

Command string staging is of significant overhead for the ACCESS.
Suggested average separation between long strings of Universal
Asynchronous Receiver Transmitter (UART) commands with two active
command lines is 800 milliseconds.

The user is advised to hold its long command strings in its own CGSE for
DT time rather than using the ACCESS to stage its long command strings.

3\. Note that the ACCESS "round-robin" prioritization of users can
improve the ACCESS processing of long and short command strings
generated by two concurrent users.

#### ACCESS Command Acknowledgment (ACKS) Messages (Types 5/6)

These messages are multiplexed with the HH system ancillary data
messages, Shuttle orbit and attitude data messages, etc. All messages
are optional. These messages are transmitted from the ACCESS to the CGSE
on the 19.2k baud link. The time in these two messages is the ACCESS
computer GMT time when the message was generated.

1\. Command Completion Status (Type 5)

After transmission by the ACCESS, the ACCESS issues an optional command
acknowledgment message to the CGSE indicating the number of commands
successfully transmitted to the HH avionics. Upon receipt of this
message, the CGSE may issue another set of commands. If the CGSE does
not opt for the command completion message, the CGSE should verify the
receipt of the commands by the payload prior to transmitting more
commands. Failure to do so may result in the loss of commands because
the command link is slower than the aggregate command rate of all the
users. In fact, transmission delays of 10-20 seconds may be common in
operations because of additional delay in the networks and MCC. The
format of this message is shown in Table 2.17.

[]{#__RefHeading___Toc456763668 .anchor}Table 2.17 Access Command
Completion Status Message Structure

**[Byte]{.underline} [Bits]{.underline} [Function]{.underline}
[Value]{.underline}**

1 1-8 Synchronization E5 (Base 16)

2 2-8 Number of data bytes 2

in the message, excluding

header and checksum

3 1-4 Customer 1 [\<]{.underline} CID [\<]{.underline} 8

Identification (CID)

3 5-8 Message type 5

4-5 1-8/1-8 Binary day of year 1 [\<]{.underline} DD [\<]{.underline}
366 (Note 1)

6-9 1-8/1-8/ Millisecond time of day 0 [\<]{.underline} M
[\<]{.underline} 86399999

1-8/1-8

10 1-8 Spare 0

11 1-8 Number of commands transmitted

12 1-8 Number of commands accepted by SPOC

13 1-8 Exclusive OR of bytes 0-255

2-12

Note 1: This time is the ACCESS computer GMT time.

2\. Data Link Status (Type 6)

The ACCESS will originate messages if errors are detected in the command
data link between the ACCESS and the CGSE. The messages indicate the
error and the number of commands rejected by the ACCESS because of the
error. The format of this message is shown in Table 2.18.

[]{#__RefHeading___Toc456763669 .anchor}Table 2.18 Access Data Link
Status Message Structure

**[Byte]{.underline} [Bits]{.underline} [Function]{.underline}
[Value]{.underline}**

1 1-8 Synchronization E5 (Base 16)

2 2-8 Number of data bytes 2

in message, from bytes 11

to end not including

check sum

3 1-4 Customer 1 [\<]{.underline} CID [\<]{.underline} 8

Identification (CID)

3 5-8 Message Type 6

4-5 1-8/1-8 Binary day of year 1 [\<]{.underline} DD [\<]{.underline}
366 (Note 1)

6-9 1-8/1-8/ Millisecond time 0 [\<]{.underline} M [\<]{.underline}
8639999

1-8/1-8 of day (M)

10 1-8 Spare 0

11 1-8 Number of command 1 [\<]{.underline} M [\<]{.underline} 120

bytes accepted or rejected

12 1-8 Status indicator (no bits

set = received CMD without

errors)

Bit #1 - CGSE shipped too many

bytes in command message

Bit #2 - Parity error in transmission

between CGSE-ACCESS

Bit #3 - Data overrun

Bit #4 - Framing Error

Bit #5 - Invalid CID

Bit #6 - Checksum Error

1-8 Exclusive OR of bytes 0-255

2 through 12

Note 1: This time is the ACCESS computer GMT time.

[]{#__RefHeading___Toc456763558 .anchor}Crew Control

The Crew Control system provides a second method (independent of the
ground command system) for controlling the flow of power to the customer
payloads and, thus, ensures that power could be removed from the payload
even in the event of any single failure. Since two independent commands
(crew and ground) are required to apply power to a customer payload, two
inhibits are present to prevent a hazardous payload function from
occurring during ascent or descent. Additional crew control functions
can be used to inhibit a hazardous payload function during on-orbit
operations.

Crew Control of the carrier power system (see Figure 2.34) is
implemented using the first two switches S1 and S2 ( DS1 and DS2
indicate the state of S1 and S2) of the SPASP or normally the first two
switches of the SSP (see Figure 2.68). The carrier can be assigned to
either half of the SSP and if assigned to the other half, S13 and S14
(DS13 and DS14 indicate the state of S13 and S14) would be used. The
remaining switches can be assigned to a customer function with a
negotiated electrical interface. Switch panel control is normally
provided only to inhibit a hazardous function or provide a crew
controlled function which must be synchronized with some other crew
activity such as Orbiter attitude control. The use of the SPASP or SSP
is determined by NASA based on the STS manifesting rules. The available
switch and indicator characteristics are shown in Figure 2.69. The SSP
cargo switching and fusing interface schematic is shown in Figure 2.70
(sheet 1 & 2).

### Undedicated Connections in Standard Interface

Some Twisted Shielded Pair (TSP) and single wires in each interface are
undedicated and may be connected by mission unique jumper plugs to the
following:

1\. Crew Control (Switch Panel)

2\. Undedicated wires in a second standard interface port assigned to
the same customer.

3\. Other function as negotiated.

Use of the special connections may result in conflicts between customer
payloads on the same flight and may therefore reduce manifesting
possibilities and flight opportunities for each customer.

![](media/image67.png)

[]{#__RefHeading___Toc457875906 .anchor}Figure 2.65 Switch Panels

![](media/image68.png){width="6.490277777777778in"
height="8.055555555555555in"}

[]{#__RefHeading___Toc457875907 .anchor}Figure 2.66 SPASP or SSP Switch
and Indicator Characteristics

![](media/image69.png){width="6.104861111111111in"
height="8.164583333333333in"}

[]{#__RefHeading___Toc457875908 .anchor}Figure 2.67 SSP Cargo Element
Switching and Fusing Interface Schematic (1of 2)

![](media/image70.png){width="5.754166666666666in"
height="8.29861111111111in"}

[]{#__RefHeading___Toc457875909 .anchor}Figure 2.68 SSP Cargo Element
Switching and Fusing Interface Schematic (2 of 2)

### Orbiter CCTV Interface

A special interface can be provided to allow the display of a customer
payload generated TV signal in the crew cabin. This signal can also be
recorded on-board or transmitted to the ground. The signals are standard
National Television Standard Committee (NTSC) (EIA RS-170/RS-330) color
or black and white television signals transmitted on a differential
interface. Details of the CCTV interfaces and services can be provided
by the project office.

### Hitchhiker Video Interface Unit

The Hitchhiker Video Interface Unit (HVIU) is Hitchhiker-provided. Video
can be accommodated from eight separate customer signal ports, one at a
time. Switching of HVIU channels is commanded via ACCESS. The HVIU
produces a differential signal output to the orbiter CCTV interface.

Customer video input to the HVIU shall be an unbalanced, 75-ohm
interface and shall conform to RS-170 and RS-330 specifications. Shield
shall be tied to frame ground at the customer side; the video signal
lines shall be isolated from frame ground by at least 1 Mohm. Therefore,
use of commercially available devices which tie signal ground to chassis
should be avoided.

During the mission, availability of real-time video telemetry depends on
orbiter support of payload CCTV and cannot be guaranteed. However,
payload video can be recorded via the orbiter recorders and replayed at
a later time during the mission or provided post-mission. Therefore,
customers whose video is critical to their experiment are advised to
consider incorporating recording capability in their hardware design.

## Hitchhiker-JR (HH-J)

### Hitchhiker-JR Overview

The HH-J carrier provides mechanical and electrical interfaces similar
to the existing GAS carrier which has been used in the past to carry
Shuttle secondary payloads. Following availability of the new carrier,
the GAS carrier will not be used for secondary payloads.

The new avionics system (Figures 2.72 - 2.74) provides for better
monitoring of carrier functions and can provide improved monitoring and
power services for customer equipment if desired.

The HH-J carrier system consists of a canister (with or without a
motorized door) equipped with a HH Remote Interface Unit (HRIU). The
HRIU communicates via a control line with a Payload and General Support
Computer (PGSC) in the crew cabin. The PGSC is a lap top class personal
computer and contains payload unique software provided by SSPP.

The HH-J avionics is operated from Orbiter power unlike the GAS avionics
which is battery operated. Orbiter power may also be used for heaters
and can be used to operate customer equipment if certain restrictions
are met. Customer equipment may also be operated from customer supplied
batteries if desired.

During flight operations, the crew controls HH-J and GAS payloads using
a menu type control and display interface on the PGSC. Unlike the
avionics used with GAS, the HRIU reports carrier status information for
display to the crew. The status information includes canister
temperature and pressure, customer battery voltage and current, door
status, and commanded relay status. This information will help SSPP, the
customer, and flight crew make decisions during the flight. On some
missions it will be possible to record the status data in the laptop
periodically for post flight use. Each HRIU has a unique data bus
address allowing the crew to individually communicate with a number of
HH-J canisters.

![](media/image71.png){width="4.370138888888889in"
height="7.459722222222222in"}

[]{#__RefHeading___Toc457875910 .anchor}Figure 2.69 HH-J Control Concept

![](media/image72.png){width="5.883333333333334in"
height="8.240277777777777in"}

[]{#__RefHeading___Toc457875911 .anchor}Figure 2.70 HH-J Power
Distribution

If the customer desires and provides the necessary wiring, it is
possible to provide the crew with some displays of customer hardware
status.

Customer mechanical interfaces are the same as for the standard HH
canister (section 2.1.1.). HH-J canisters may be flown on the side-mount
or bridge configuration.

### Hitchhiker-J Electrical Interfaces

#### HH-J Electrical Power

HH-J customer equipment may be operated from Orbiter power or from
internal customer batteries with power switched by carrier relays in a
manner similar to GAS as shown in Figure 2.70. If internal power is
used, the carrier provides two size 12 power wires individually
protected by 20 amp fuses in the carrier and switched by a crew
controlled relay. Customer peak power should be limited to a maximum of
10 amps in either line because of vacuum derating of the fuses.

The enable relays (\"E\") in all the canisters are simultaneously
activated by the crew near the beginning of the mission and deactivated
near the end of the mission. The \"E\" relays are controlled by a single
switch on the Bus Interface Assembly (BIA) in the cabin and are
independent of the computer for safety reasons. The \"E\" relays provide
power to the HRIUs in the canisters. Once the HRIUs are activated, the
crew can individually activate the \"K3\" relay (to provide power to the
customer equipment) and the \"K4\" relay (controlling canister heater
and door power) in any specific canister.

The HRIU is provided with a current monitor which measures the total
current in the A, B, and C power lines. The HRIU also measures the
voltage on the down stream side of the K3 and K4 relays.

The customer may elect to use Orbiter +28 VDC power. In this case,
maximum power draw of the equipment is limited to 100 watts and the
energy use over the duration of the mission is limited to a maximum of 4
Kwh. The customer equipment must meet the requirements of section 2.3.1
with regard to power voltage, conducted electromagnetic noise emitted by
the customer equipment, ground isolation, and susceptibility of customer
equipment to Orbiter generated electromagnetic noise. Orbiter power is
normally available starting several hours after payload bay doors are
opened and extended to several hours prior to payload bay door closing.

#### HH-J Control Relays

The HRIU has two control relays \"K1\" and \"K2\" which may be used to
control customer equipment. The relays are limited to 1 Amp and 32 volts
and are break-before-make single pole double throw type. The nominal
launch configuration of all relays is \"reset\".

#### HH-J Thermistors

The user may elect to place SSPP supplied temperature sensors in his
equipment wired to the customer interface connector. The characteristics
of the sensors are given in section 2.2.2. The use of the sensors will
improve crew monitoring of significant temperatures in customer
equipment.

#### HH-J Analog Telemetry Data

The user may elect to connect internal status measurements to carrier
analog telemetry inputs which allow crew monitoring of a voltage between
zero and +5 volts. A single measurement may be connected to the PCMAD
signal line as defined in section 2.4.7.1. Also, an index pulse,
PCMINDX, may be used to step a customer\'s internal multiplexer as
described in section 2.4.7.1. For HH-J, only infrequent sampling of the
data is possible. Contact the Project Office for more information.

#### HH-J Bi-level or Pulse Commands

Bi-level commands may be set to OV (false), or to +28V (true), or pulsed
from false to true and back to false. (It is preferred to have the
bi-level transverse from false to true, default state is OV for HRIU)
All commanding of bi-level functions is performed by the mission
specific Flight Software (FSW), which is developed at GSFC, and executed
on the Payload & General Support Computer (PGSC). Four bi-levels are
available to each customer. Only one bi-level signal may be commanded by
the FSW at a time. A minimum of 100msec is required between each
bi-level command. Figure 2.71 illustrates the HH-J bi-level command
electrical interface.

![](media/image73.png){width="5.997916666666667in"
height="1.6729166666666666in"}

![](media/image74.png){width="5.996527777777778in"
height="3.7534722222222223in"}

[]{#__RefHeading___Toc457875912 .anchor}Figure 2.71 HH-J Bi-level
command electrical interface

#### HH-J Customer Connectors

The HH-J canister bottom plate contains connectors for connecting
customer equipment designated J13, J2, and J11 as shown in Table 2.21.
J13 provides the Orbiter power interfaces, J2 provides signal
interfaces, J11 connects to a connector on the canister bottom plate and
can be used for ground test connection to customer equipment after it
has been installed in a canister or for connecting two adjacent
canisters during flight using an optional interconnect cable. An
additional connector, J12 is used in place of J13 if the customer
equipment contains its own battery. The Project Office will furnish
connectors to the customer for use in fabricating the customer to
carrier cables.

#### HH-J Grounding

The customer equipment return for Orbiter 28VDC power is Orbiter power
return. If the customer provides his own battery power, the battery
voltage may not exceed 32 VDC and the battery negative terminal should
be connected to frame (structure) ground in the customer equipment.
Orbiter power return connection in customer equipment using Orbiter
power must be isolated from frame ground by a minimum of 10 K Ohms
resistance. Orbiter power return is connected to frame ground in the
Orbiter.

The reference for analog signals, thermistor returns, and PCMINDX signal
is carrier signal ground. The signal ground must be isolated from frame
ground and Orbiter 28 V return by a minimum of 10 K ohms unless a
project waiver is obtained. Signal ground is connected to frame ground
in the carrier.

#### HH-J Electromagnetic Interference Control

HH-J customer equipment must meet the requirements of Appendix H.

#### HH-J Thermal Control

Customer equipment may contain heater(s) and thermostat(s) connected to
the 28V Orbiter heater power lines (+28HTR, RETH) controlled by
commandable relay K4 and not exceeding a maximum of 50 watts (for all
heaters on simultaneously at 32 volts). Thermostats should not be set to
a temperature higher than 5 degrees C unless approved by the Project
Office.

#### HH-J Malfunction Inputs

Two of the thermistor inputs, THER1 and THER2, may instead be used as
malfunction inputs. Malfunction inputs on HH-J are similar but not
identical to the functions in the GAS carrier. A user may provide a
\"true\" malfunction input to cause the carrier to reset the power relay
in the carrier and remove power from the instrument. A malfunction true
condition is indicated by an input voltage between zero and 2.0 volts
relative to circuit ground, or by a resistance of less than 100 ohms
between the malfunction input and circuit ground. A malfunction false
condition is indicated by an input voltage between 3.5 volts and 5.0
volts or an input resistance higher than 100K ohms.

If a malfunction true condition is sensed at either of the malfunction
inputs for 2 seconds or more, the HH-J carrier software will reset the
power relay. The relay will remain reset unless set by the flight crew.
The values of the malfunction input voltages are available for display
to the crew in the Orbiter cabin.

The equivalent circuit for the malfunction input in the carrier is the
same as for the thermistor input shown in Figure 2.69.

![](media/image75.png)

[]{#__RefHeading___Toc457875913 .anchor}Figure 2.72 Malfunction Input
Circuitry

[]{#__RefHeading___Toc456763670 .anchor}Table 2.20 Hitchhiker-Jr
Electrical Interface Connections

**[Power Connector P13 (Orbiter Power)]{.underline}**

Customer Connector Type: CVA6R20-15PN-16

**[ID]{.underline} [PIN]{.underline} [TYPE]{.underline}
[FUNCTION]{.underline}**

+28 A C +28 Power Circuit A

RETA B C Power Return (Note 1)

+28B C C +28 Power Circuit B

RETB D C Power Return (Note 1)

+28HTR E B +28 Heater Power

RETH F B Heater Power Return (Note 1)

FRMGND G B Frame Ground

**[Signal Connector P2]{.underline}**

Customer Connector Type: KJG6E18-35PN-16

PCMAD 1 A Analog Data, O - +5v

PCMINDX 41 A Index Pulse

SIGGND 2 A Signal Ground

SHIELD 6 A Shield (To Be Tied To Frame Ground In PLD)

BLCMD1 17 A Bi-level/Pulse Command 1

BLCMD2 18 A Bi-level/Pulse Command 2

BLCMD3 19 A Bi-level/Pulse Command 3

BLCMD4 20 A Bi-level/Pulse Command 4

THER1 14 A Thermistor 1 Or Malf Input #1

THER2 15 A Thermistor 2 Or Malf Input #2

THER3 16 A Thermistor 3

K2RES 58 A K2 Relay Reset Contact

K2SET 57 A K2 Relay Set Contact

K2ARM 59 A K2 Relay Arm

K1RES 49 A K1 Relay Reset Contact

K1SET 56 A K1 Relay Set Contact

K1ARM 50 A K1 Relay Arm

[Safe/Arm Or Interconnect Connector P11]{.underline}

Customer Connector Type: TVSO6RF-21-16S(453)

**[ID]{.underline} [PIN]{.underline} [TYPE]{.underline}
[FUNCTION]{.underline}**

A B

B B

G B

R B

N B

C B

J F

H F

P F

D F

L F

K A Twisted Shielded Pair TSP1+

F A TSP1-

E A TSP Shield

M A TSP2+

S A TSP2-

Power Connector P12 (Battery Power)

Customer Connector Type: JTO6RE-16-6S

BATA+ A C CUSTOMER BATTERY + CIRCUIT A

BATB+ B C CUSTOMER BATTERY + CIRCUIT B

PPWRA C C CUSTOMER LOAD CIRCUIT A

PPWRB D C CUSTOMER LOAD CIRCUIT B

+28HTR E B ORBITER 28V HEATER POWER

RETH F B HEATER POWER RETURN

Note 1: Power Return Pins B, D May Be Connected Together Within Payload.

Note 2: Wire Type Designation:

**TYPE SIZE**

A 22 GA

B 16 GA

C 12 GA

F 20 GA

See Fusing Requirements In Table 2.6.

Note 3: Customer Will Make No Connections To Unused Pins

## Hitchhiker Ejection Capabilities Specification

The Hitchhiker carrier system provides several options for launching a
small spacecraft from the Shuttle payload bay. Figure 2.75 shows a
typical payload configuration. Each option requires the same maximum
payload weight and CG offset and same user-supplied 9.37 inch interface
plate, which attaches to the carrier with a clamp mechanism. Figure 2.76
describes this interface plate with some reference dimensions. Detailed
requirements for this plate are contained in the most current revision
of GD 1507205, [Ejection System User Interface Control
Drawing]{.underline}. None of the launch configurations provides any
electrical power or signal connection to the spacecraft, but each
provides a different satellite envelope and payload environment. The
five different payload configurations listed below are shown in Figures
2.77 to 2.81.

[PAYLOAD CONFIGURATIONS]{.underline}

Hitchhiker Ejection System (HES): always mounted in a canister.

1\. with an opening door

2\. with no door (open-top canister)

Pallet Ejection System (PES): canister-mounted configuration.

3\. with an opening door

4\. with no door (open-top canister)

Pallet Ejection System (PES): pallet-mounted configuration.

5\. on top of cross-bay structure

Payload and ejection system are mounted either in a canister or on a
pallet prior to orbiter installation and launch. The user must provide
means for lifting the spacecraft during installation on to the ejection
system. For a canister-mounted satellite, only the top of the payload
will be accessible for servicing after it is installed into the
canister.

Once in orbit with the Shuttle in the requested attitude, the clamp is
released by the crew and the payload is ejected. The system does not
provide for controlled rotation (spin) of the payload prior to ejection,
but a worst case ejection torque applied about the ejection vector will
be calculated for every mission. This torque is dependent on several
factors. Orbital lifetime of ejected objects in typical Shuttle orbits
is usually less than one year.

Spacecraft must be designed to avoid contact with the canister under
launch loads and during ejection.

The ejection system and door mechanism are zero fault tolerant against a
failure that would cause inability to eject or inability to close the
door. Therefore, the spacecraft design must satisfy Shuttle safety
requirements for a landing in the Shuttle with the door open. Spacecraft
with hazardous functions that occur after ejection (such as deploying
appendages) must provide adequate safety inhibits to prevent premature
activation. Payloads with such functions are strongly advised to set up
a Technical Interchange Meeting (TIM) with the SSPP system safety
organization.

Users must select an ejection attitude and velocity that preclude any
possibility of collision with the Shuttle during the portion of the
mission following satellite deployment. JSC will perform a re-contact
analysis to insure that no re-contact occurs.

Table 2.23 lists some characteristics and requirements of HH launcher
systems. Deviations from these or other ejection system requirements are
negotiable on a case-by-case basis. For example, a larger CG offset may
be acceptable for a physically smaller satellite.

[]{#__RefHeading___Toc456763671 .anchor}Table 2.21 Characteristics Of
Hitchhiker Launcher Systems

Maximum spacecraft weight 150 lb (68 kg)

Maximum spacecraft CG offset from separation plane 10.25 in (26 cm)

Maximum spacecraft CG offset from launcher centerline 0.25 in (0.64 cm)

Ejection velocity range 1 to 4 ft/sec (0.3 to 1.2 m/sec)

![](media/image76.png){width="5.830555555555556in"
height="7.413194444444445in"}

[]{#__RefHeading___Toc457875914 .anchor}Figure 2.73 Ejection System
Overview

![](media/image77.png){width="6.136805555555555in"
height="7.561111111111111in"}

[]{#__RefHeading___Toc457875915 .anchor}Figure 2.74 Payload Interface
Plate

![](media/image78.png){width="6.502083333333333in"
height="7.0569444444444445in"}

[]{#__RefHeading___Toc457875916 .anchor}Figure 2.75 Hitchhiker Ejection
System with Door

![](media/image79.png){width="5.354861111111111in" height="7.5375in"}

[]{#__RefHeading___Toc457875917 .anchor}Figure 2.76 Hitchhiker Carrier
Ejection System with Open Canister

![](media/image80.png){width="6.497916666666667in"
height="6.959027777777778in"}

[]{#__RefHeading___Toc457875918 .anchor}Figure 2.77 Pallet Ejection
System with Door

![](media/image81.png){width="6.493055555555555in"
height="7.836805555555555in"}

[]{#__RefHeading___Toc457875919 .anchor}Figure 2.78 Pallet Ejection
System with Open Canister

![](media/image82.png)

[]{#__RefHeading___Toc457875920 .anchor}Figure 2.79 Pallet Ejection
System on Single Bay Pallet