Satellite-satellite tracking for estimating geopotential coefficients.

Results of simulation studies of tracking of low-altitude satellites by a high-altitude satellite using range measurements between satellites. The high-altitude satellite is tracked by ground-based range trackers. The low-altitude satellites are tracked only by the high-altitude satellites. Orbital elements for one tracking satellite and four tracked low-altitude satellites are estimated, along with a set of low degree and order geopotential coefficients. Estimation of geopotential coefficients of low degree and order is shown to be considerably more accurate using satellite-to-satellite tracking than using ground-based tracking. The use of data from one high-altitude satellite tracking four low-altitude satellites in a range of inclinations is shown to produce geopotential coefficient estimates with smaller errors than presently exist in individual coefficients or would be obtained using ground-based tracking of the same satellites.