SEASAT orbit determination from laser range observations

The sensitivity of SEASAT orbit solutions and parameter estimations to the applied gravity and atmospheric drag model was investigated. For the gravity field the NASA GEM-9, GEM-10B, PGS-S3 and PGS-S4 models were used. Atmospheric drag was modeled by constant and time-varying cross-sectional areas and adjustable drag coefficients. Although PGS-S4 is the best SEASAT gravity model, computed orbits show a distinct sinusoidal trend in the along-track position error component. By solving for a limited number of gravity field coefficients a modified PGS-S4M model with considerably reduced along-track errors is obtained.