Atmospheric densities derived from CHAMP/STAR accelerometer observations

摘要: Abstract The satellite CHAMP carries the accelerometer STAR in its payload and thanks to GPS SLR tracking systems accurate orbit positions can be computed. Total atmospheric density values retrieved from measurements, with an absolute uncertainty of 10–15%, under condition that radiative force model, macro-model, instrumental calibration parameters are applied, upper-atmosphere winds less than 150 m / s . (i.e. a bias scale factor) tangential acceleration were accurately determined using iterative method, which required estimation gravity field coefficients several iterations, first result was EIGEN-1S (Geophys. Res. Lett. 29 (14) (2002) 10.1029) solution. procedure derive is as follows: (1) reduced-dynamic computed, used pseudo-observations, for reference purposes; (2) dynamic fitted pseudo-observations calibrated saved data file containing all necessary information values; (3) compute at each integration step, terrestrial coordinates available. This applied 415 days over total period 21 months, yielding 1.2 million useful observations. model predictions DTM-2000 (EGS XXV General Assembly, Nice, France), DTM-94 (J. Geod. 72 (1998) 161) MSIS-86 Geophys. 92 (1987) 4649) evaluated by analysing ratios “observed” “computed” ratio) globally, functions solar activity, geographical position season. global mean showed models underestimate 10–20%, rms 16–20%. binning function local time revealed diurnal semi-diurnal components too strong DTM models, while three latitudinal gradient inaccurately. Using priori, certain re-estimated STAR-derived densities, DTM-STAR test model. this preliminary 1.00 15%, respectively, tidal modelling errors become small. only representative high activity conditions, seasonal effect probably not estimated due correlation effect. At least one more year separate effect, taken low conditions must also assimilated construct circumstances.