Deriving the spin rate/orientation from the quiescent spacecraft ABRIXAS using optical observations
J. Greiner, P. Friedrich, D. -E. Liebscher, G. Hasinger, P. D. Maley, B. Lübke-Ossenbeck
Abstract
With the loss of the battery system of ABRIXAS
shortly after launch and consequent absence of telemetry, there was
urgent need to determine ABRIXAS' spin rate and orientation in order to
assess the possibility of re-establishing telemetry during periods of
full-Sun orbits. We, therefore, conducted optical and video
observations of ABRIXAS passages with a 1-second time resolution, and
later simulated the optical appearance of ABRIXAS for several passages
based on a three-dimensional model of the reflectivity properties of
the 2.5m x 1.8m x 1.2m size-satellite. Here we present the results of
the comparison of our grid of light curve models with the observations
and show first how the spin rate of ABRIXAS slowed down between June and
December 1999 and second what information can be deduced on the temporal
change of the orientation of the spin axis. We conclude with discussing
the benefit of using ground based optical observation as a cost
effective way to develop information about the orientation of a
satellite when there is no telemetry.