The Effect of Helium on Low Earth Orbit Atmospheric Drag
Abstract
Atmospheric drag describes the perturbing force of the atmosphere on the orbits of Low Earth Orbit (LEO) objects and depends on the spacecraft drag coefficient and the mass density of the space environment. Recently, examination of the contracted upper atmosphere during this past solar minimum has motivated the need to achieve a better understanding of the role of helium in thermospheric dynamics. In a quiet, contracted thermosphere, mass transport processes governed by vertical diffusion and large scale meridional flow allow helium to concentrate around winter polar latitudes at 500 km altitude. Atmospheric drag is a significant source of uncertainty in orbital trajectories at these altitudes, and the effect of helium on atmospheric drag has not yet been quantified. The Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) is a physics-based model of Earth's upper atmosphere maintained by the National Center for Atmospheric Research that offers the ability to study the effects of including or neglecting helium on atmospheric density and spacecraft drag coefficient estimates at LEO altitudes. To examine the spatial and temporal effects of helium on LEO satellite drag, we simulate TIEGCM atmospheres with and without helium along the orbital trajectories of two LEO satellites, the Challenging Minisatellite Payload (CHAMP) at 375 km altitude and the Gravity Recovery and Climate Experiment (GRACE) at 500 km altitude, for one week during each of three active, moderate, and quiet geomagnetic activity time periods selected for both this past solar maximum and solar minimum. We compare TIEGCM mass densities with and without helium included as a major species with accelerometer-derived density estimates for CHAMP and GRACE revised based on newly-computed drag coefficients modeled for TIEGCM atmospheres with and without helium during these time periods to identify the strengths and weaknesses of TIEGCM estimates attributed to helium. We additionally compare TIEGCM atmospheres with and without helium to atmospheres simulated by the Naval Research Laboratory's Mass Spectrometer and Incoherent Scatter Extended Model (NRLMSISE-00), an empirical model of the atmosphere that includes helium, in order to assess trends in the variations in helium predicted from different atmospheric models.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMSA23B3190B
- Keywords:
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- 2447 Modeling and forecasting;
- IONOSPHEREDE: 2722 Forecasting;
- MAGNETOSPHERIC PHYSICSDE: 7513 Coronal mass ejections;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMYDE: 7934 Impacts on technological systems;
- SPACE WEATHER