A Case Study in NASA-DoD - The Black Vault

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The maximum experiment power for durations of more than a few
seconds is required by the SAGE experiment (during the track interval),
not the HCMM experiment. The power breakdown for the SAGE vehicle for
the 180 sec track interval during data taking is as follows:
Experiment
Telemetry
Attitude control and determination
Power system circuitry
Total
43 W
19 W
16 W
12 W
90 W (180 sec)
The power consumed by experiments plus telemetry can be high for short
periods of time, e.g., it is 59 W for 10 to 15 min and 62 W for 3 min.
(1)
DESCRIPTION OF STPSS
AND COMPARISON WITH AEM
The STPSS spacecraft also has a-28 V bus, but its voltage regulation
is not quite as stringent as the AEM (±5 V rather than ±4 V, as
shown in Table B-1).
Additional power regulation equipment (±1.8 percent
regulation) can be added if the experiments require it (optional),
but the associated weight and power loss are not mentioned.
The STPSS
spacecraft is equipped with three 20 Ah batteries and up to 24 solar
panels may be used in two arrays. These arrays can provide up to 1200 W
maximum (during illumination) in the three-axis-stabilization configuration
with sun tracking. Use of the same 24 panels around a spinning
spacecraft will generate only about 1200/w, or 380 W.
Spacecraft subsystems,
excluding experiments, require approximately 100 to 200 W, depending
on which one of four stabilization techniques is used. A block
diagram of the STPSS power subsystem is shown in Fig. B-2.
The STPSS spacecraft can supply substantially more power for experiments
than the AEM, i.e., 400 W compared to 40 W. Short-term peak
load data comparable to those available for the AEM are not available
for the STPSS. Other characteristics, shown in Table B-l, are relatively
standard.
The average power available for experiments over an orbital period
also depends on the orbit.