Thermospheric density derived from onboard GPS observation data

Onboard GPS observation data of a satellite includes accurate information of velocity and location, which are closely related to atmospheric density. Therefore, these GPS information can be used to derive thermospheric density through integration of differential equation. This paper presents a new method of deriving atmospheric density with a high temporal resolution from precise orbit data of low earth orbiting (LEO) space objects, and also presents the solution procedure of mean motion n(M) and the inverse ballistic coefficient B which are the two most important parameters for retrieving density. Tiangong-1 is taken as an example to evaluate the effectiveness of the method. The result shows that the GPS-derived density is in good agreement with observed density with the average error 8.6% and 8.4% respectively on 1st January and 24th February in 2012 for Tiangong-1. This result indicates the method provides an effective and reliable way to obtain extensive and accurate thermospheric density.