NASA/CR-201140, Hickey, M.P., An Engineering Model for the Simulation of Small-Scale Thermospheric Density Variations for Orbital Inclinations Greater Than 40 Degrees , Prepared for Systems Analysis and Intergration Laboratory, Science and Engineering Directorate, NASA Marshall Space Flight Center, AL 35812, Contract NAS8-38333, by Physitron, Inc. 3304 Westmill Drive Huntsville, AL 35805, August, 1996, pp. 48, Format(s): PDF 4262k |
This report describes the development of an engineering model that simulates small-scale density variations in the thermosphere and provides engineers with a set of instructions enabling them to implement the model in their existing orbital propagation models. The model is provided as a callable subroutine that can be easily used in conjunction with the MET model, and is simplistic enough to contain the essential elements of the variations without overburdening computational resources. The model FORTRAN code is included at the end of this report.
The model is derived from the spectral analysis of thermospheric neutral density data obtained from the Neutral Atmosphere Temperature Experiment (NATE) on the Atmosphere Explorer-C satellite between December 1974 and December 1978. During this time, the 68.1 degree inclination orbits were approximately circular between 220 and 400 km altitude. Solar activity was low to moderate during this period.
Total densities for contiguous strings of 15 sec density data values were spectrally analyzed, and Fast Fourier Transform periodograms were computed for each string. The periodograms were binned according to latitude and the geomagnetic activity index ap, and then average periodograms were computed for each bin. Finally, stochastic (autoregression) models were fit to each of the average periodograms. Two laditude bins and two ap bins were employed.
The model is derived from the spectral analysis of thermospheric neutral density data obtained from the Neutral Atmosphere Temperature Experiment (NATE) on the Atmosphere Explorer-C satellite between December 1974 and December 1978. During this time, the 68.1 degree inclination orbits were approximately circular between 220 and 400 km altitude. Solar activity was low to moderate during this period.
Total densities for contiguous strings of 15 sec density data values were spectrally analyzed, and Fast Fourier Transform periodograms were computed for each string. The periodograms were binned according to latitude and the geomagnetic activity index ap, and then average periodograms were computed for each bin. Finally, stochastic (autoregression) models were fit to each of the average periodograms. Two laditude bins and two ap bins were employed.
| Keywords: | thermosphere, thermospheric density, waves, density variations simulation, gn&c design |
|---|---|
| Subjects: | Engineering: Fluid Mechanics and Thermodynamics: Thermal Protection |
| ID Code: | 336 |
| Deposited On: | 02 July 2002 |