TERRESTRIAL ATMOSPHERIC EFFECTS ON SATELLITE ECLIPSES WITH APPLICATION TO THE ACCELERATION OF LAGEOS

We examine spatial variability of attenuation in the Earth's atmospher e as a cause of asymmetrical eclipses and consequent acceleration of L AGEOS, i.e., the solar radiation pressure on LAGEOS due to the Earth's penumbra. Measurements of atmospheric attenuation derived from the sa tellite-borne Stratospheric Aerosol and Gas Experiment after the erupt ion of Mount Pinatubo were used to simulate the largest expected aeros ol content of the atmosphere. In our,experiment one hemisphere was loa ded with volcanic aerosols, while the other was not. The difference be tween attenuation in the two hemispheres sets a maximum reasonable lim it to the size of eclipse asymmetry. This condition would accelerate L AGEOS only about 0.2 picometers per second squared (pm s(-2) or 10(-12 ) s(-2)) and indicates that eclipse asymmetry can only account for abo ut 40-50% of the remaining unmodeled residuals. This is slightly less than the penumbral acceleration found by Vokrouhlicky et al. (1994).