A Case Study in NASA-DoD - The Black Vault

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The duration of the data pass is 10 min during illumination and 15 min
during occultation. The HCMM vehicle power budget during data pass is
roughly as follows:
Experiment
Telemetry
Attitude control and determination
Power circuitry
Total
24 W
35 W
12 W
12 W
83 W (10 to 15 min)
The remainder of the energy produced during illumination is used for
battery charging and this energy is later used by the spacecraft during
eclipse. During the eclipse, 46 Whr of energy are available from the
battery; this is about 75 percent of the energy used in charging the
battery. Examination of the power system performance for the HCMM and
SAGE missions indicates that about half the energy out of the arrays
is used for battery charging.
On the SAGE vehicle, there are some high short-duration loads
(less than 4 sec) from the experiment and from the tape recorder.
The timing for the experiment module is such that the tape recorder
peak demands and experiment peak demands do not occur at the same time;
the power system is not adequate for this. The telemetry subsystem
requires 18 W to 21 W, except during tape dump (once per day), when
this subsystem uses 51 W of power (500 sec duration). The total SAGE
power demand during tape dump is:
Standby power to experiment
Telemetry
Attitude control and determination
Power circuitry
Total
9 W
51 W
16 W
12 W
88 W (500 sec)
Tables of subsystem electric load demands provided by Boeing show
an HCMM payload total power consumption of 34 W during a data pass.
However, a total of the entries adds only to 24 W. Either there is an
error in a table entry, or else there is a mistake in addition.
** One such load is the 120 W pulse option (2 to 4 sec duration) to
the experiments. The experiment module, which includes the experiment
and a tape recorder, requires only 9 W during standby but can draw a
maximum pulse power of 117 W during acquisition (4 sec duration).