Precise onboard ephemeris propagation method using CW frame and multiple compressions

The purpose of this paper is to develop a precise onboard ephemeris propagation method, which uses a multiple sequential compression method. Onboard knowledge of the ephemeris of the satellite is used for attitude determination and antenna pointing control. The compression of the predicted ephemeris is performed in the satellite orbit frame, radial, in-track, and out-of plane (CW) frame. A model for two-body plus secular variations is used to define a reference orbit. The residuals between the ephemeris from the reference orbit and the true orbit from a numerical technique are compressed in a multiplicity of base functions and the coefficients produced in the compression of residuals are limited to satisfy the requirements of the onboard ephemeris propagation. An accurate estimate of the position and velocity with a relatively small number of coefficients is achieved, and a crucial feature of a stable prediction beyond the fit span is obtained when the periodic ground-based upload is delayed or even omitted. In this way a convenient weekly uploading can be adopted.