Determination of spin axis orientation of Geosynchronous objects using space-based sensors: an initial feasibility investigation

The spin axis of a rotating satellite can be determined by studying the rate of change of the observed spin rate as a function of the satellite’s position in its orbit. The observed spin rate change is largest when the rate of change of the sun-satellite-observer angle is largest. Application of this method is problematic for deep-space objects due to the slow rate of change of this angle, however some assumptions can be made to make the problem tractable. Alternatively, since space-based sensors in Low Earth Orbit are moving much faster than ground-based sensors, use of such a sensor has the potential to expand the number of objects for which the spin axis can be determined. This paper explores both approaches. First, a ground-based – and assumption-based method is used to determine the spin state of rocket bodies in deep-space. This is followed by a comparison of the rate of change of the spin rate that would be observed by both a ground-based and a space-based sensor. This comparison both illuminates the issues with using a ground-based sensor, and the potential of a space-based sensor. The use of the upcoming NEOSSat spacecraft – to be launched in Q2 2011 – to exploit this potential is explored.