Evaluation of Effects of Main Perturbation Forces on the LEO Orbit Design

With the successful deployment and effective operations of U.S.A.sponsored GPS/MET experiment and some follow-up campaigns,for example,SAC-C sponsored by NASA of U.S.A.and Argentina,and CHAMP by Germany,radio occultation via GPS constellation has been demonstrated to be one of the competitive alternatives for monitoring of the terrestrial atmosphere.This technique has such potential functions as follows:it can give independent temperature profile;the water vapor profiles can be derived by inversion method;it can provide atmospheric parameter profiles with refined vertical resolutions;it is independent of such factors as aerosol,cloud,waterfall,and so on,i.e.,it is not subject to the weather conditions;gravity height can be surveyed as good as 10 meters;the gravity wave could be detected from the middle troposphere to the stratosphere;the total electron content in the ionosphere can be precisely measured;the low Earth orbiter′s precision orbit information can be used as a by-product for refining the existent Earth gravity model.Based on the established conceptions for occultation technique for Earth′s atmosphere sensing,Yan et al.proposed a possibility to monitor the regional atmosphere with particular orbit design for Low Earth Orbiting (LEO) satellite;its gist is to preserve the LEO satellite in a specific orbit so as to keep the occultation events regularly occurring at a geographically relatively fixed location;in a simulation,60-200 day-long preservations for LEO orbit are designed,depending on the different GPS satellites and some other specific parameter setting-up.Such a particular LEO satellite can provide practical way of atmospheric parameter profiles for a given point of interest;it can be effective in profiling atmosphere,and costs a comparatively smaller budget compared with a constellation of LEO satellites with irregular or random occultation tangent points footprints.Herein,we pay our attention to the perturbation related to such a satellite′s orbit design.As far as Low Earth orbiters are concerned,the perturbation forces,for instance,air drag,luni-solar gravitation,N-body perturbation,solar radiation pressure and tidal perturbation and so on,are analyzed,and the formulations for derivation of perturbation sources are summarized.Also,the orders of magnitude for the perturbation forces are assessed based on the presented formulations.According to the particular requirement of stability for radio occultation footprints,force models are singled out for efficiency purpose.The effects of perturbation force models on the orbit design are estimated.