Preliminary results to support evidence of thermospheric contraction

Atmospheric density has an important influence in predicting the positions of satellites in low Earth orbit. For long-term predictions of satellite ephemerides, any future density trend in the thermosphere would be a valuable input, not only to satellite operators, but also to studies of the future low Earth orbit environment in terms of space debris. A secular thermospheric density trend has not yet been definitively proven but predictions by Roble and Ramesh [1], along with evidence by Keating et al. [2] and Emmert et al. [3 & 4], strongly suggest the existence of such a phenomenon. With the ultimate goal of deriving a long-term empirical model of thermospheric cooling and contraction, the primary focus of this paper is to present preliminary results obtained to support the existing evidence for such a thermospheric contraction. The results from four satellites over 30 years indicate a thermospheric mass density decline of -4.1 ± 0.7 % per decade above an altitude of approximately 355 k