Longitudinal Wave Observations Using MAVEN NGIMS Aerobraking and Deep Dip Data

The Mars Atmosphere and Volatiles EvolutioN (MAVEN) mission was characterized by an inclined orbit with periapsis of ~150km and apoapsis of ~6200km for most of the mission. For nine selected 1-2-week campaigns during the regular mission the spacecraft dipped deeper in the atmosphere with periapsis down to ~125km (deep dips). Additionally, in 2019, the spacecraft adjusted the apoapsis down through an extended aerobraking maneuver again with periapsis dipping to ~125 - 130km for 6 weeks. These extended campaigns near the homopause provide a unique opportunity for the Neutral Gas and Ion Mass Spectrometer (NGIMS) and the Accelerometer (ACC) to combine in-situ observations of the thermosphere (~125 - 175km). Preliminary analysis of the data reveal longitudinal waves along the 135, 145, 155, 165, and 170km bands. When the data was limited to the shorter deep dip campaigns, these wave patterns were not as easily fit or organized. By contrast, the much longer 6-week aerobraking campaign provided sufficient data points so that the wave forms could be well fitted. Because these wave fits were conducted from near the homopause, this allows us to connect longitudinal wave dynamics from the middle atmosphere to the upper atmosphere. The ACC was able to perform wave-4 and wave-3 fits on the lower thermosphere bands (~135 - 150km). NGIMS observed similar behavior at these lower altitudes as well but has better resolution at the higher altitudes and is capable of performing similar wave-fitting on the entire altitude rage (135-175km).