Spin motion and orientation of LAGEOS-2 from photometric observation

The spin rate and spin axis orientation of the Laser Geodynamics Satellite 2 (LAGEOS-2) satellite were determined by analysis of photometric observation data. A photometer system developed at the Space Geodesy Facility at Herstmonceux, U.K., was used to time solar glints from the rotating satellite. It was found that the spin rate of LAGEOS-2 slowed by 38% per year between March 2000 and November 2002 and that the spin axis undergoes a slow, complex precession with respect to the earth's rotation axis. Moreover, the analysis revealed that the direction of the spin was the reverse of that of the earth's rotation and that the optical alignment of a reflector surface on LAGEOS-2 can deviate from its position vector by up to 15 arcmin. Index Terms--Attitude control, optical reflection, photometry, space technology.