SPS Feasability Study SD76SA0239-2

where a^ and are constants related to the nominal orbit. For two satellites in close proximity in the same orbit, 6ro = 69O = 0. Consider that one is △0O ahead of the nominal position and one is A0O behind the nominal position. Their relative motion then becomes Hence, to first order there is no relative motion of the satellites. This analysis can be extended to show that the effect of any disturbance that is the same, to first order, on both satellites produces no relative motion, to first order. Errors in initial conditions can produce relative motions that could result in collisions. Since solar pressure produces no relative satellite motion, it is not controlled by the stationkeeping system. Semimajor axis variations are corrected with one three-hour burn per orbit during eclipsing periods. The required engines are oriented to fire in the -z direction to minimize propellant contamination of solar array and reflector surfaces. The burn is centered 90° from the earth sun line in the first half of the orbit after emerging from eclipse. The velocity increment to be imparted is 0.02589 m/sec which requires a thrust of 57.5 newtons. Changes in orbital inclination are corrected by two firings per orbit, one north and one south. As a satellite passes through its ascending node, thrusters on the north end fire to rotate the orbit plane toward the equatorial plane. Simarly, as the satellite passes through its descending node, thrusters