This section describes the performance drivers for the contact functions of
*Telemetry,* *Commanding, and GSS Processing* and describes a
reasonable distribution of the required functionality on hardware platforms.
The *Telemetry* and *Commanding* appendices (B and C, respectively)
contain detailed analysis of processing loads in each area. Analysis of
*GSS* load is included in Appendix B, since status data can be processed
like telemetry data. Several telemetry and commanding architecture options are
presented in Appendix B (Figure B-9) and Appendix C (Figure C-9). Each option
varies the allocation of functions across platforms, as shown in Figure 9.
Functions for *Telemetry* processing, *Commanding* processing, and
*GSS* processing are listed.

As discussed in Appendix B, the *Telemetry* load is bounded by the
satellite PCM rate, which ranges from 75 bps to 5 Mbps, the data expansion
factors associated with telemetry processing, and the telemetry processing and
display requirements. The higher telemetry rates, (e.g., 1.024 Mbps to 5
Mbps), consist primarily of mission data, with little or no embedded SOH data.
Therefore, not all measurands in the 5-Mbps stream are processed for SOH
assessments, which is the SSCS responsibility. A maximum SOH embedded rate of
128 Kbps and a maximum dedicated SOH stream rate of 128 Kbps are assumed for
the worst case SOH load.

The *Commanding* load is driven by the commanding rate (which ranges from
75 bps to 28.8 Kbps), amount of real-time constraint checking performed, and
complexity of real-time command verification. *Commanding* performance
loads are detailed in Appendix C.

At lower telemetry and commanding rates, *GSS* data processing becomes an
additional loading factor. This data is used as input to the command
constraint checking process and in determining both the quality of the
satellite telemetry data and the vehicle state. Thus, the processing load for
*GSS* data is included in the calculation of total contact load. The GSS
data rate is assumed to range from 3.1 Kbps to 6.8 Kbps (see Appendix B).

To illustrate the variation in processing load allocations across platforms,
two cases with specific data rates are analyzed. For high data rates, the
maximum *Telemetry*, *Commanding*, and *GSS* data rates (1.024
Mbps mission, 256 Kbps SOH, 28.8 Kbps commanding, and 6.8 Kbps GSS) are
assumed. For nominal data rates, 8 Kbps SOH, 1 Kbps commanding, and 6.8 Kbps
GSS are assumed.