MAVEN Aerobraking Campaign of 2019 and the Resulting Accelerometer Measurements: Wave Features in the Martian Thermosphere
Abstract
Determining the processes that work to couple the various Mars atmospheric layers ( 0-200 km) is an important and ongoing study of the planet. Understanding atmospheric escape processes and climate evolution are in part dependent on this coupling. Features consistent with lower to upper atmosphere coupling have been observed by many Mars spacecraft instruments. Dedicated sampling continues in order to more fully characterize the inter-annual, seasonal, latitudinal and solar local time variations of this coupling. For this study, measurements of the Martian mass density structure in the thermosphere were obtained during the recent MAVEN aerobraking campaign making use of the onboard Accelerometer. MAVEN aerobraking occurred over Ls 340 to 3 (near the equinox season), spanning Mars Years 34 and 35. Aerobraking was conducted over 12-February to 30-March, 2019, yielding Accelerometer densities from altitudes as low as 123 km and up to 150 km, and from southern hemisphere latitudes on the nightside. Sorting of MAVEN Aerobraking accelerometer densities was performed as a function of 5-km reference altitude bins (135 to 150 km) and discrete latitude swaths yielding density plots as a function of longitude. A wave fitting routine was also applied, revealing wave#2 and #3 amplitudes are most important at low latitudes, along with decreasing amplitudes with rising altitudes above 135 km. We also investigated the coherence of the waves (phasing) from lower to upper thermosphere altitudes during this sampling period. Finally, comparisons are made with longitude wave structures observed previously by other Accelerometer instruments on other spacecraft. These longitude wave features are indeed produced by coupling with the lower-middle atmosphere via upward propagation of planetary waves of various mode types.
- Publication:
-
EPSC-DPS Joint Meeting 2019
- Pub Date:
- September 2019
- Bibcode:
- 2019EPSC...13..347B