Michael Schmidt, Julian Zeitlhöfler, Armin Corbin, Kristin Vielberg, Anno Löcher, Sergei Rudenko, Mathis Bloßfeld, Lea Zeitler, and Jürgen Kusche
A major problem in the precise orbit determination of Low-Earth-Orbiting (LEO) satellites at altitudes below 1000 km is modeling the aerodynamic drag which mainly depends on the thermospheric density and causes the largest non-gravitational acceleration. Typically, empirical thermosphere models such as NRLMSISE-00, NRLMSIS 2.0, JB2008 or DTM2013 are used to calculate density values at satellite positions. However, since the current thermosphere models cannot provide the required accuracy, unaccounted variations in the thermospheric density may lead to significantly incorrect satellite positions.
In this presentation, we will report about the most important results from our recently published paper Zeitler et al. (2021). In this study we compared for the first time thermospheric density corrections for the NRLMSISE-00 model in terms of scale factors calculated from satellite laser ranging (SLR) measurements to various spherical LEO satellites (Starlette, Stella, Larets, etc.) with the corresponding values from accelerometer measurements on-board CHAMP and GRACE.
Our results demonstrate that both measurement techniques can be used to derive comparable (with correlations of up to 80% and more depending on altitude) scale factors of the thermospheric density with a temporal resolution of 12 hours, which vary around the value 1. This indicates to which extent the NRLMSISE-00 model differs from the observed thermospheric density. On average, during high solar activity, the model underestimates the thermospheric density and should be scaled up using the estimated scale factors. We find a linear decrease of the estimated thermospheric density scale factors above 680 km of about −5% per decade due to climate change.
Furthermore, we validate the approach of deriving scale factors from SLR measurements by using two independent software packages.
Zeitler L., Corbin A., Vielberg K., Rudenko S., Löcher A., Bloßfeld M., Schmidt M., and Kusche J. (2021). Scale factors of the thermospheric density ‐ a comparison of SLR and accelerometer solutions. Journal of Geophysical Research: Space Physics, 126, e2021JA029708. doi: 10.1029/2021JA029708