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Table 8-1. TDRSS KaSA Forward Service Signal Parameters (cont’d)
Notes (cont’d):
2. The forward data rate in this table is the baud rate that will be transmitted by the TDRSS
(includes all coding and symbol formatting). For non-WDISC customers, forward data
conditioning is transparent to the SN. For all customers, forward convolutional coding is
transparent to the SN. These transparent operations should be performed by the customer prior
to transmission to the SN data interface. Refer to Section 3, paragraph 3.6 for a description of
SN data interfaces, associated constraints, and WDISC capabilities. WSC/GRGT is capable of
25 Mbps with changes.
3. The SN is capable of supporting BPSK signals at data rates less than 300 kbps; however, its use
will be controlled and must be coordinated with GSFC Code 450.
4. After the start of the KaSA forward service, if a customer MOC is unable to accurately define fo (the nominal center frequency of the customer platform receiver), the forward service carrier
frequency can be swept. The KaSA forward service frequency sweep will be initiated by the SN
ground terminal at fo-30 kHz and linearly swept to fo +30 kHz in 120 seconds and held at fo +30
kHz thereafter. The KaSA forward service frequency sweep does not impact simultaneous SN
ground terminal Doppler compensation of the KaSA forward service carrier and PN code rate (if
applicable).
fo
22555
6
5. “K” =
10
Rounded to the nearest integer if K integer and 0 < K < 198.
5
fo is the nominal center frequency in Hz of the customer platform receiver as defined by the
customer MOC.
6. Customers who operate in a SS-BPSK mode for one service cannot reconfigure any of their
Forward Services (i.e., MAF, SMAF, SSAF, KuSAF, or KaSAF) to an SS-UQPSK mode. Contact
Code 450 if additional flexibility is required.
This modulation scheme includes separate but simultaneous command and
range channels. The command channel includes a rapidly acquirable PN code
and contains the forward service data. The range channel is acquired
separately and contains a PN code which satisfies the range ambiguity
resolution requirements. The length of the command channel PN code is 2 10 -1,
where the length of the range channel PN code is 256 times the command
channel PN code length. The customer platform command channel acquisition
can precede customer platform range channel acquisition; this feature permits
rapid acquisition of the range channel by limiting the range channel PN code
search to only 256 chip positions while the range channel PN code itself
contains 261,888 chips. The PN code chip rate is coherently related to the
TDRS transmit frequency in all cases. This feature permits the customer
platform receiver to use the receiver PN code clock to predict the received
carrier frequency, thereby minimizing receiver complexity and reducing
acquisition time. 451-PN CODE-SNIP defines all the salient characteristics for
the forward range and command channel PN code libraries. The Agency
Spectrum Manager responsible for PN code assignments will allocate a
customer platform-unique PN code assignment from these libraries. The GSFC
Spectrum Manager is responsible for NASA PN code assignments.
Revision 10 8-6 450-SNUG