Dynamical state of the atmosphere in 1986 from the orbital decay of the LDEF satellite

Abstract

he dynamical state of the earth’s atmosphere in 1986 is discerned from the orbital decay of the Long Duration Exposure Facility (LDEF) satellite which was launched into a near-circular fixed-attitude orbit and, therefore, presented a constant cross-sectional area to the ambient atmosphere. The atmosphere began the year in a contracting mode which was reversed to an expanding mode from Day 20 through Day 45. It was then switched to a prolonged contraction mode which lasted until Day 240. During this period, LDEF faced progressively smaller densities as it descended through the atmosphere. The atmosphere was in overall expansion from Day 240 through Day 310 and in general contraction for the rest of the year 1986. The calculated densities faced by LDEF, generally, followed the pa0.7ttern of the observed monthly average 10.7 cm solar flux which exhibited the classic feature of the semi-annual variation of the atmosphere. The calculated drop of altitude of the satellite agreed closely with the observation altitude drop.