InSight Communications Degradation During Peak Heating Phase of Atmospheric Entry

Abstract

This paper discusses the analysis of the UHF (401 MHz) plasma-induced communications blackout (and brownout) experienced by the Mars InSight spacecraft during its entry, descent, and landing (EDL) phase into the Martian atmosphere on 26 November 2018. The UHF relay links from InSight to the Mars Reconnaissance Orbiter and to the Mars Cube One A and Mars Cube One B CubeSats suffered a period of about 52 s of degradation, consisting of a combination of brownout (signal fades) and blackout (complete loss of signal). The observed signal fades and outages on these proximity links spanned the interval from about 48 to 100 s after entry started at the atmospheric interface. In addition, the degradation of the weaker signal received at the Green Bank, West Virginia 100 m radio telescope is also discussed, which occurred from about 40 to 120 s after atmospheric entry. The observations were in agreement with existing models of signal degradation given the entry trajectory of the vehicle. This paper discusses model estimates and measurements of signal degradation during the peak heating phase of the InSight EDL, as well as the results of high-fidelity analysis performed using computational fluid dynamics tools.