SN User's Guide - ESC Home - NASA

capability of +3 kHz is available. For DG1 mode 2, the I and Q channel PN
codes are unique 2 11 -1 Gold Codes.
NOTE:
The SN DAS allows expansion of the TDRSS F3 – F7 and K,
L, M MAR DG1 mode 2 services to be scheduled for
extended duration or in a ‘near real time’ manner. Refer to
Appendix H for further information.
c. DG1 Mode 3 (SMA via F8 – F10 or K, L, M). DG1 mode 3 can be used when
range and two-way Doppler measurements (coherent transponder operations)
are required concurrently with return service high-rate data transmission.
Restrictions on DG1 mode 3 signal acquisition are identical to those for DG1
mode 1. In DG1 mode 3, the Q channel must contain only data and no PN
code.
d. Functional Configurations. Table 5-7 lists the DG1 MA return service functional
configurations and a further description of the functional configurations, the I-Q
channel ambiguity, and data polarity ambiguity is found in Appendix B,
paragraph B.3.2.
5.3.2.3 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 (SMA via F8 – F10 or K, L, M). Return service signal acquisition
by the SN ground terminal for DG2 coherent is possible only when the
scheduled TDRSS (SSA or MA) 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 twoway
Doppler tracking can be provided when the DG2 carrier is coherently
related to the TDRSS (SSA or MA) forward service carrier frequency.
b. DG2 Noncoherent (SMA via F8 – F10 or K, L, M). The DG2 carrier is
independent of the TDRSS (SSA or MA) forward service carrier frequency. The
customer platform transmit frequency for DG2 noncoherent service must be
defined by the customer MOC to an accuracy of +700 Hz in its service
specification code when requesting TDRSS SMA return service (refer to
Section 10, paragraph 10.2.2). For customers whose frequency uncertainty is
greater than +700 Hz, an expanded frequency search capability of +3 kHz for
SQPSK DG2 services and +35 kHz for BPSK and QPSK DG2 services is
available after start of the return service.
c. Functional Configurations. Table 5-7 lists the DG2 SMA return service
functional configurations and a further description of the functional
Revision 10 5-20 450-SNUG