HR: 17:00h
AN: SA14A-05    [Abstracts]
TI: Atmospheric Neutral Density Observed With Accelerometers
AU: * Bruinsma, S
EM: sean.bruinsma@cnes.fr
AF: CNES-CT/SI/GS, 18, avenue E. Belin, Toulouse, 31401 France
AU: Biancale, R
EM: richard.biancale@cnes.fr
AF: CNES-CT/SI/GS, 18, avenue E. Belin, Toulouse, 31401 France
AB: The German satellite CHAMP was launched in a circular, nearly-polar orbit at 460 km altitude in July 2000. The two main mission objectives are the mapping of the magnetic and gravity fields of the Earth. The US/German GRACE satellites were launched in March 2002, also in a circular, nearly-polar orbit, but at 500 km altitude. The GRACE satellites are separated from each other by approximately 220 km, so the satellites pass the same geographical location within about 30 seconds of each other. The mission objective is to track changes in the Earth's gravity field. The CHAMP and GRACE satellites carry STAR accelerometers, positioned at their centers of mass, and GPS receivers and attitude sensors in order to determine accurate satellite positions as well as accurate accelerometer calibration parameters. Total atmospheric density has been derived from the CHAMP/STAR data, and presently about 3 years of observations are available. The GRACE/SuperSTAR accelerometer data are available to the scientific community since August 2004, and atmospheric density can be derived using a similar procedure as the one succesfully applied to CHAMP/STAR data. The CHAMP and GRACE satellites do not orbit at the same altitude (CHAMP is in an approximately 100 km lower orbit), and their orbital planes generally do not coincide. Therefore, the local time vs. latitude sampling is much better using data from both missions. On the other hand, if one wants to study the propagation of waves or disturbances, the orbital planes must be coincident or nearly so. In this study, the densities observed by CHAMP and GRACE are intercompared, both for (almost) coincident orbital planes as well as (almost) perpendicular ones. Secondly, the densities of GRACE-A and GRACE-B are compared in order to investigate if short-scale variations of the order of 100-200 km can be observed. The density observations will also be compared to thermosphere models, and certain modelling errors will be discussed.
DE: 1241 Satellite orbits
DE: 1294 Instruments and techniques
DE: 0355 Thermosphere--composition and chemistry
DE: 0358 Thermosphere--energy deposition
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting