Comtech EF Data C5 - Manual (Page 203)

C5/K1/K3 Integrated Satellite Terminal System Operation
Rev. 0 4–77
SATELLITE MOTION AND ORBITAL INCLINATION
SATELLITE
NOMINAL
POSITION
N
S
GEO-SYNCHRONOUS
EQUATORIAL ORBIT
GEO-SYNCHRONOUS
INCLINED ORBIT
SATELLITE
N/S
MOTION
N
S
A
B
C
A
AS STATION-KEEPING FUEL
BECOMES EXHAUSTED, THE N/S
STATION-KEEPING IS LIMITED
TO PRODUCE A MORE INCLINED
ORBIT, THUS PROLONGING THE
LIFE OF THE SATELLITE.
A SATELLITE IS MAINTAINED AT AN
ASSIGNED GEOSTATIONARY
LOCATION THROUGH THE USE OF
GROUND COMMAND ADJUSTMENTS
TO ITS N/S AND E/W LOCATION. THIS
PROCESS, KNOWN AS SATELLITE
STATION-KEEPING, IS USED TO KEEP
THE SATELLITE DRIFT WITHIN
CERTAIN BOUNDARIES.
THE N/S MOTION CHANGES THE
PATH FROM THE SATELLITE TO THE
EARTH, RESULTING IN FREQUENCY
CHANGES KNOWN AS THE DOPPLER
EFFECT.
Figure 4-27. Doppler Shift
4.5.1 Buffer Size
The depth of the receive buffer depends on four parameters:
! Doppler shift caused by satellite
! Stability of each clock (plesiochronous/Doppler operation)
! Frame/Multiframe length of multiplexed data format
! Allowable time between clock slips