A Case Study in NASA-DoD - The Black Vault

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Table C-I
C&DH CHARACTERISTICS OF AEM, MMS, AND STPSS
Characteristic AEM- HCMIa(l) AEM-SAGE ( 31s) s ( 5) STPSS ( 1)
Telemetry and Command
Band VHF S-band S-band S-band S-band
Tracking System
Compatibility STDN STDN STDN STDN SGLS
Uplink Frequency, MHz 148 2025-2120 2025-2120 2025-2120 1750-1850
Uplink Subcarrier
Modulation FCM/FSK/AM/AM n.a. PCM/FSK/A /FM PSK Ternary FSK with AM
Command Format 60 bits n.a. 60 bits 96 bits f 43 bits J
Command Bit Rate 600 bps n.a. 60 bps 2K, 1K, 125 bps 2 kbps
Downlink Frequency.
MHz 136 2280 2200-2300 2200-2300 2200-2300
Telemetry Format:
Word length 8 bits 8 bits 8 bits 8 bits (3 1 8 bits
Minor frame length 256 words 128 words 128 wordsd 128 words Variable(2)
Major frame length 64 minor frames 64 minor frames 64 minor frames 128 minor frames Variable ( 2 )
Maximum Bit Rate 1.024 kbpsb 8.192 kbps 1 Mbps e 64 kbps 8-128 kbps k
Power Output 1/4 W 2 W 1 W, housekeeping 1.7, 3.5, or
2 W, experiment 7.1 1 4 h (34) 2 W'
Communications Security Not available Not available Not available Not available Available
Antenna Polarization RHCP RHCP RHCP I with RHCP and RHCP ( 2 )
1 with .LHCP( 3 4 )
Memory Size 256 words x 32 bits/word and 256 words x 32 bits/ 16K bits x 18 8K words x
256 words x 16 bits/wordc word and 256 words bits/wordi 32 bits/word m
x 16 bits/word
Tape Recorder Capacity None None 4.5 x 108 bits Up to 9 x 108 or 108 bits
up to 8 x 109
bits (optional)
aTwo versions of the AEI spacecraft are currently being designed by Boeing: HCMM and SAGE. The HNCM vehicle uses
the VHF band for commands and for housekeeping telemetry and S-band for downlink experimental data. The SAGE mission
uses S-band for commands, telemetry, and data.
bData rate during the boost phase is 8192 bps.
eCommands are compared with words In a 256 word, 16 bits/word PROM (Programmable Read Only Memory).
Delayed commands
are stored in the remote command processor, which consists of a 256 word, 32 bits/word CMOS/RAH (Complementary Metal
Oxide Substrate/Random Access Mmory) semiconductor memory (pp. 1-134 to 1-136 of Ref. 31).
dAssumed the same as the HCMM vehicle because no change is indicated.
eTape recorder playback rate. Real time data rate Is limited to I kbps or 8 kbps. A new encoder would be required
if higher bit rates are needed.
fReference 33 lists the command format as fixed at 96 bits (48 bit introduction and 48 bit command word). Page 34 of
Ref. 5 lists the command format as 48 bits (which can he assumed to b only the command word portion of the total format).
gWith use of the 2000 bps command rate, a single 5 rin command contact per day is required for loading of commands in
the on-board computer. This command load will allow the computer to operate the spacecraft for periods of 24 to 72 hr.
hMission selectable.
The MS C&DN computer includes storage for attitude control information, as well as commands. The STPSS C&DN computer
is used only for storing commands, and a separate computer handles attitude control. Therefore, the apparent large difference
in the capacities of the two C&DN computers is one of definition not actual capability.
JSGLS itself has variable command formats. Page 8-3 of Ref. I shows a 43 bit format as TRW's conception of what is
required.
kBy changing subcarriers, this can be increased to 256 kbps, This is SGLS's maximum capacity.
1If appreciably higher data rates or more services are desired, there is provision for the standard 2 W transmitter to
be used to derive a higher power transmitter (e.g., 20 W) in the payload segment.
mWord length deduced from data bus supervisory line formats, p. 8-5 of Ref. 1.