Estimating Density Using Precision Satellite Orbits from Multiple Satellites
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timating Density Using Precision Satellite Orbits from Multiple Satellites Craig A. McLaughlin,1 Travis Lechtenberg,2 Eric Fattig,2 and Dhaval Mysore Krishna2
Abstract This article examines atmospheric densities estimated using precision orbit ephemerides (POE) from several satellites including CHAMP, GRACE, and TerraSAR-X. The results of the calibration of atmospheric densities along the CHAMP and GRACE-A orbits derived using POEs with those derived using accelerometers are compared for various levels of solar and geomagnetic activity to examine the consistency in calibration between the two satellites. Densities from CHAMP and GRACE are compared when GRACE is orbiting nearly directly above CHAMP. In addition, the densities derived simultaneously from CHAMP, GRACE-A, and TerraSAR-X are compared to the Jacchia 1971 and NRLMSISE-00 model densities to observe altitude effects and consistency in the offsets from the empirical models among all three satellites.
Introduction Because satellite drag is the largest error source in estimating satellite orbits below 800 km, improved drag modeling is a key component of improving orbit determination and prediction accuracy, which is important for avoiding collisions with satellite debris and planning satellite operations such as remote sensing of Earth or communicating with satellites. The February 2009 collision of an Iridium communication satellite with a defunct Russian satellite demonstrates the importance and difficulty of the space debris and orbit prediction problem. The long-term objectives of this research are to improve satellite drag modeling and enhance understanding of the upper atmosphere at satellite altitudes. One of the current goals is to show the potential for utilizing precision orbit measurements and ephemeris data to generate corrections to a given density model, thus yielding more accurate density estimates necessary for enhanced atmospheric drag calculations, improved orbit determination and prediction, and an 1
Aerospace Engineering, University of Kansas, 1530 W. 15th St., Lawrence, KS 66047. Graduate Research Assistant, Aerospace Engineering, University of Kansas, 1530 W. 15th St., Lawrence, KS 66047. 2
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increased understanding and measurement of the density and its variations in the thermosphere and exosphere. This article examines density estimation for multiple satellites using precision orbit ephemeris (POE) data as observations. The research presented in this article is a step toward the goal of combining accurate data with good spatial coverage obtained from a large number of satellites. Many satellites currently possess Global Positioning System (GPS) receivers or satellite laser ranging retro reflectors that when utilized in conjunction with an orbit determination process provide position accuracies in the centimeter to meter range. This research estimates atmospheric density using precision orbit data of these satellites as observations in an orbit determination scheme. Several papers have examined the use of GPS
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