SN User's Guide - ESC Home - NASA

7.3.2.3 DG2 Signal Parameters
DG2 signal parameters are subdivided into two modes of operation, DG2 coherent and
noncoherent. DG2 must be used when the return service data rate equipment exceeds
the capability of DG1 operations. DG2 operations cannot provide TDRSS range
tracking because PN code modulation is not used. The two DG2 modes are
distinguished as follows:
a. DG2 Coherent. Return service signal acquisition by the SN ground terminal for
DG2 coherent is possible only when the scheduled KuSA TDRSS forward
service signal is acquired by the customer platform and the carrier transmitted
by the customer platform are coherently related to the forward service signal
from the TDRS. TDRSS two-way Doppler tracking can be provided when the
DG2 carrier is coherently related to the TDRSS KuSA forward service carrier
frequency.
b. DG2 Noncoherent. The DG2 carrier is independent of the TDRSS KuSA
forward service carrier frequency. The customer platform transmit frequency for
DG2 noncoherent service must be defined by the customer MOC to an
accuracy of +5 kHz in its service specification code when requesting TDRSS
KuSA return service. For customers whose frequency uncertainty is greater
than +5 kHz, an expanded frequency search capability of +20 kHz is available
after start of the return service.
c. Functional Configurations. Table 7-6 lists the DG2 KuSA return service
functional configurations through the SN ground terminal receiver and a further
description of the functional configurations, the I-Q channel ambiguity, and data
polarity ambiguity is found in Appendix B, paragraph B.3.3. Refer to paragraph
7.3.6 for the KuSAR IF service functional configurations.
Revision 10 7-19 450-SNUG