DRAG ON THE LAGEOS SATELLITE

The average drag on the LAGEOS satellite appears to be well understood. Yarkovsky thermal drag accounts for about 70% of the observed drag. Neutral particle drag accounts for about 14% of the drag for a hydrogen number density of 5 × 109 m-3. Proton drag accounts for 12 per cent at a number density of 3 × 109 m-3 and a temperature of 5000 K in the plasmasphere for a satellite potential of -1 V. Charged helium and oxygen give another 4%, so that charged particle drag totals 16%. All together the three types of drag account for all of the observed average drag. Less well understood are the fluctuations in LAGEOS's along-track acceleration when the orbit intersects the Earth's shadow. -from Author