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Revision 10 C-9 450-SNUG
Table C-3. Acquisition Events for TDRSS Services (Normal Forward and Return) (cont’d)
Event Time
Customer platform
receives forward
service signal
Command
channel PN code
acquired
T1 = TF + d
T2 = T1 + cmd
Equipment Status
Customer Platform TDRS/Ground Terminal
Command channel PN code
acquisition process starts;
carrier acquisition process
enabled. Autotrack acquisition
process starts for Ku-band or
Ka-band customers with
autotrack enabled.
Command channel PN code
despreader synchronized;
carrier acquisition process
starts
Remarks
Continuing as above d reflects estimated
propagation delay
(approximately 240 msec):
ground terminal
TDRS customer platform
For Ku-band and Ka-band
customer platform and TR = TF,
the customer platform autotrack
process after TR shall be at a
rate which results in an
instantaneous rate of change of
Prec 10 dB/sec; the customer
platform autotrack of forward
service signal is not necessary
if the customer platform
antenna can be open-loop
pointed with sufficient accuracy
to meet KuSA or KaSA forward
and return service requirements
Continuing as above cmd 20 sec (example value
for NASA 4 th generation
transponder); cmd represents
the time required for the
customer receiver to acquire
the command channel PN
code. Command channel is PN
modulated only if data rate
300 kbps.