

     Well, almost. It turns out that clever orbital mechanics can 
engineer things so that resonant interactions with the higher order 
harmonics of the Earth's gravitational field can pump energy into a 
satellite, and keep it from experiencing drag effects for periods of 
months to years. 

     My favorite example of this is the Soviet/Russian heavy ELINT 
satellites of the Cosmos 1603 class, which are in 14:1 resonance. In 
particular, C1833 has undergone two periods of prolonged *gain* in 
altitude, the current one having started in June 1991; the mean altitude 
of the satellite is now as high as it has ever been since launch on 18 
March 1987. (Looking at the elements for C1833 also shows the 
limitations of NORAD's software -- but that's another story.) 

    This probably has little relevance to space stations, since the 71 
degree orbits of the C1603 satellites are at 850 km, which is 
unacceptably far into the inner van Allen belt for manned platforms. But 
it's kind of interesting from the point of view of the physics of the 
situation. 

    (Orbital elements for these satellites are available on request.) 


Allen Thomson                  SAIC                       McLean, VA