RE: NavSpaSur

Ted Molczan (
Thu, 4 Jan 1996 21:43:32 -0500

Josh Williams asked:

>Does anyone know any of the NORAD numbers for the NavSpaSur Satellites? I 
>would like to track them but information is VERY hard to come by, also TS 
>Kelso has told me that the project is NOT classfied, and that confused me 
>even more. Maybe the satellites are not named after the project, which 
>maybe the problem here...

NavSpaSur stands for Naval Space Surveillance System.
It is not a satellite system. It is an Earth-based radar
interferometer system, used to detect and track satellites.
It consists of three stations which transmit a powerful
217 MHz signal narrow fan-beam of radio waves across the
southern U.S.A. The fan can be thought of as a fence of
radio waves. When satellites cross through it, they reflect
some of the radio waves, which are then received by several
of six receivers across the southern U.S.A. The motion of
a satellite causes the reflected radio waves to be Doppler-
shifted. The amount of the Doppler shift will be different
for each receiving site because the relative velocity of
the satellite will be different for each site. By analyzing
a sufficient number of near-simultaneous Doppler shifted
reflections, the orbital elements of the satellite can be

I know at least one radio amateur in the southern U.S.A. who
has received the reflections. In principle, hobbyists could
make use of the NavSpaSur system, if they could build their
own network of receivers and data reduction/analysis system.

What little I know about this comes from Desmond King-Hele's
book, Observing Earth Satellites, ISBN 0 333 33041 2.

bye for now