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5.3 MA Return Services
5.3.1 General
The RF signals provided by the customer platform to the TDRS and the characteristics
of data provided at the SN ground terminal interface are defined in paragraphs 5.3.2
through 5.3.5. This discussion assumes that an appropriate return service has been
scheduled and a data signal is present at the TDRS interface.
NOTE:
The F8 spacecraft has some SMA return G/T performance
variations due to an MA element array and sunshield
proximity problem. The F8 G/T varies based upon the
normal daily TDRS diurnal cycle. This section documents
the required Prec values for both the F8 hot and cold
conditions. The hot periods can be predicted and will occur
at regular intervals with a total hot period of less than
12 hours/day. Note that F8 is unavailable for normal
customer scheduling.
5.3.2 Signal Parameters
The TDRSS MA return service signal parameters are listed in Table 5-6. The services
are divided into 2 major groups, Data Group 1 (DG1) and Data Group 2 (DG2). DG1
services utilize spread spectrum modulation while DG2 services are non-spread. A
description of the features inherent in the DG1 and DG2 services is discussed in 5.3.2.2
and 5.3.2.3, respectively. Within each data group, there are several types of
modulation. Additionally, both data groups support coherent and noncoherent modes.
A description of these general characteristics is provided in 5.3.2.1.
Revision 10 5-12 450-SNUG