[time-nuts] WAAS/Inmarsat-3

Jim Lux jimlux at earthlink.net
Fri Jul 5 21:46:14 EDT 2013

An ION paper by Nagle, et al.

Nagle, J. R., Van Dierendonck, A. J., Hua, Q. D., "INMARSAT-3 NAVIGATION 
Journal of The Institute of Navigation, Vol. 39, No. 4, Winter 
1992-1993, pp. 445-462.

Inmarsat-3, the next generation of Inmarsat satellites, will carry a 
dedicated transponder package that will be capable of transmitting 
signals virtually identical to those of GPS at the Ll frequency (1575.42 
MHz). This paper provides a brief functional description of the 
Inmarsat-3 navigation transponder. This is followed by a discussion of 
the results of two studies performed to determine the compatibility 
between the proposed Inmarsat-3 navigation signals and the GPS 
navigation signals. The first study resolved the issue of potential 
interference that may be caused by the Inmarsat-3 navigation signals to 
GPS receivers acquiring and tracking the GPS signals. The second study 
examined the selection of C/A-codes to be used by the Inmarsat-3 
navigation payloads transmitting GPS lookalike signals. The properties 
of these codes were then applied to the expected signal levels of the 
Inmarsat-3 satellites to assess the interference potential to GPS. The 
results show that the proposed Inmarsat-3 signals will not adversely 
interfere with the GPS signals.

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