Update on the evolution of the LAGEOS orbit

The character and causes of the along track acceleration on the LAGEOS satellite is studied. An empirical model of this effect is desirable for the determination of Earth and station orientation parameters at the centimeter level from laser ranging observations and to obtain the best Earth rotation parameters. Analysis of the signature of the acceleration leads to a better physical understanding of the mechanism(s) causing it. The cause of the acceleration (orbit decay) is unknown but calculations and theoretical studies of the changes in the spacecraft orbit suggest that charged particle drag and possibly, Earth albedo radiation pressure (sunlight reflected from the Earth back onto the spacecraft) are the most likely explanations.