Monday, September 16, 2013

Florida Space Institute Seminar September 18

Florida Space Institute Seminar Announcement

Speaker:  John Wise
Affiliation: Air Force Research Lab, Space Weather Center of Excellence Branch of the Battlespace Environment Lab of the Space Vehicles Directorate
Day and Date: Wednesday, September 18, 2013
Time: 11:00 - 12:00

Location: Research Park
12354 Research Parkway
Partnership 1 Bldg. Suite 209
Orlando, FL 32826

Title:          Empirical Modeling Of The Thermosphere
The thermosphere is the part of our atmosphere extending from 80 km to around 600 km.  It is the region in which low earth orbit (LEO) satellites operate.  Neutral density variations from the thermosphere create drag on these satellites and affect their orbits.  In order to understand how the thermosphere affects satellite orbits we need  to model its neutral density and composition.  We discuss some measurements from  the Atmospheric Density Mass Spectrometer (ADMS), which flew onboard the TacSat-2 satellite during the last solar minimum in 2007, which collected  in-situ ratios of total oxygen/N2  in the thermosphere between 415-425 km, at various local times and latitudes equatorward of +/- 40 degrees.   The number densities for oxygen and nitrogen were compared to the NRLMSISE-00 model and to the mass spectrometer measurements of the OSS and NATE from Atmospheric Explorer (AE) during the solar minimum of 1976.  The ADMS atomic oxygen was determined to be more than 50% lower than the atomic oxygen measured by AE at 400 km.  During 2007 the atomic oxygen was about 50% lower than MSIS, but the ADMS N2 densities were in reasonable agreement with the model.  ADMS did not collect data for helium so we are only able to infer its mixing ratio based on corrected model results.  We adjusted  the MSIS total density and O/N2 profiles for several local times when ADMS, CHAMP and GRACE were co-located.  The MSIS exospheric temperature  and atomic oxygen were adjusted to reduce data/model errors between the three experiments in a least squares sense.  Reasonable fits were obtained for late afternoon in the northern hemisphere as well as midnight local times, but the dawn and noontime cases were more difficult to model.
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