Radiation pressure forces, the anomalous acceleration, and center of mass motion for the topex/poseidon spacecraft

摘要

Shortly after launch of the TOPEX/POSEIDON (T/P) spacecraft (s/c), the Precision Orbit Determinatio n(POD) Team at NASA's Goddard Space Flight Center and the Center for Space Research at the University of Texas, discovered residual alongtrack accelerations which were unexpected. Here, we describe the analysis of radiaiton pressure forces acting on the T/P s/c for the purpose of understanding and providing an explanation for hte anomalous accelerations. The radiation forces acting on the T/P solar array, which experiences warping due to temperature gradients between the front and back surfaces, are analyzed and the resulting alongtrack accelerations are determined. Characteristics similar to those of the anomalous acceleration are seen. This analysis led to the development of a new radiation force model, which includes solar array warping and a solar array deployment deflection of as large as 2 deg. As a result of this new model estiamtes of the empirical alongtrack acceleration are reduced in magnitude when compared to the GSFC tuned macromodel and are less dependent upon beta', the location of the sun relative to the orbit plane. If these results are believed to reflect the actual orientation of the T/P solar array, then motion of the solar array must influence the location of the s/c center of mass. Preliminary estiamtes indicate that the center of mass can vary by as much as 3 centimeters (cm) in the radial component of the s/c's position due to rotation of the deflected, warped solar array panel. The altimeter measurements rely upon accurate knowledge of the center of mass location relative to the s/c frame of reference. Any radial motion of the center of mass directly affects the altimeter measurements.