A Case Study in NASA-DoD - The Black Vault

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The STPSS can carry a nominal payload of about 1000 lb, can be
operated at altitudes up to geosynchronous, and weighs about 1000 lb.
It can be procured in three different configurations--a spinning version
(STPSS-S), a low-cost, three-axis-stabilized version (STPSS-LC), and a
three-axis-stabilized precision version (STPSS-P).
The MMS is the most sophisticated of the standard spacecraft considered
in this study; it is designed for on-orbit servicing and reuse.
It can carry a payload of about 4000 lb and can also be operated up to
geosynchronous altitude.
AEM and MMS spacecraft have communications systems that are compatible
with the Space Tracking and Data Acquisition Network, while the L-AEM
and STPSS are compatible with the Space Ground Link System. This difference
in the communication system needs to be corrected before the AEM
and MMS can be used for Air Force missions. (The modifications necessary
to make this correction are discussed later.) Another difference is in
the data rate capability of the communication systems. Both the AEM and
MIS have data rates considerably less than that of the L-AEM and STPSS,
i.e., 8 and 64 kbps,* respectively, as compared with 128 to 256 kbps.
All of the spacecraft use 28 V electric power systems. The basic
differences are in the solar array designs and battery charging systems.
The AEM has a fixed solar array capable of providing about 40 to 50 W for
experimental use. The other designs treat the solar array as a missionspecific
item. The peak array power for the L-AEM is 1000 W, almost as
much as the 1200 W of the STPSS output; the MMS power system can handle
arrays having a peak output of up to 3600 W. The battery-charging system
of the MKS is different from those of the L-AEM and STPSS. All three provide
for more than one battery, but an individual charging system is used
by the L-AEM and STPSS, whereas a parallel charging system is used for the
14S.
In stabilization and control capability, the MMS is again superior to
the other spacecraft with a pointing accuracy of ± 0.01 deg and a pointing
stability of ± 10 -6 deg/sec. The L-AEM design provides essentially the
The communications data rate is given in kbps, the power system
capacity in volts (V), and the solar array output in watts (W).