LAGEOS-1 spin determination, using comparisons between Graz kHz SLR data and simulations

kHz SLR data contains unique information about the measured targets; this information allows e.g. determination of spin parameters (spin period, spin direction, spin axis orientation) of various satellites, using various methods for different spin periods / satellites: Spectral analysis for spin periods of 2 s (AJISAI (Kirchner et al, 2007)), simulations for spin periods of 77.5 s (GP-B), and comparing simulation results with kHz data for very long spin periods like LAGEOS-1 (about 5000 s). For the long LAGEOS-1 spin periods, we developed a method to calculate spin axis orientation and spin period from Graz kHz SLR data. This method is based on simulation of returns from each retro reflector, with spin period and spin axis orientation as input parameters. Varying these parameters, the simulation generates retro tracks similar to those seen in the kHz SLR data; comparing simulated and measured tracks, allows determination of spin period, and spin axis orientation. Applying this method to a set of LAGEOS-1 passes covering a period of 178 days – shows also the slow change of the LAGEOS-1 spin axis direction with time.