Scientific Observations With the InSight Solar Arrays: Dust, Clouds, and Eclipses on Mars

Abstract

Records of solar array currents recorded by the InSight lander during its first 200 sols on Mars are presented. In addition to the geometric variation in illumination on seasonal and diurnal timescales, the data are influenced by dust suspended in the atmosphere and deposited on the solar panels. Although no dust devils have been detected by InSight's cameras, brief excursions in solar array currents suggest that at least some of the vortices detected by transient pressure drops are accompanied by dust. A step increase in array output (i.e., a "cleaning event") was observed to be directly associated with the passage of a strong vortex. Some quasiperiodic variations in solar array current are suggestive of dust variations in the planetary boundary layer. Nonzero array outputs before sunrise and after sunset are indicative of scattering in the atmosphere: A notable increase in evening twilight currents is observed associated with noctilucent clouds, likely of water or carbon dioxide ice. Finally, although the observations are intermittent (typically a few hours per sol) and at a modest sample rate (one to two samples per minute), three single-sample light dips are seen associated with Phobos eclipses. These results demonstrate that engineering data from solar arrays provide valuable scientific situational awareness of the Martian environment.

The whirlwinds of Elysium: A catalog and meteorological characteristics of “dust devil” vortices observed by InSight on Mars

“…Lorenz and Jackson, 2015). InSight's solar panels can in principle record such shadows, and these records have indicated dust variations and clouds on Mars (Lorenz et al, 2020). However, solar array data are only recorded when the lander is 'awake' to perform radio transmissions or other high power operations, hence long gaps exist when no data are available.…”

Geophysical Observations of Phobos Transits by InSight

“…The Sol 96–99 Phobos transits of spring 2019 were detected as single‐sample current drops, confirming their occurrence but precluding quantitative analysis (Lorenz, Lemmon, Maki, et al., 2020).…”

“…The changes in the solar array current (SAC) channels are given as the average drop in ampere between the two solar panels and the corresponding % drop from baseline. Channels E‐0791 (west) and E‐0771 (east) provide the currents from the hard‐tied strings, physically around the perimeter of each solar array and directly tied to incoming sunlight (Lorenz et al, 2020; Mittelholz et al, 2020). Channels E‐0792 and E‐0772 do not directly represent incoming sunlight, but are correlated with the IFG measurements.…”

“…For Phobos, this can reach around 40%. The current generated by the InSight solar arrays is monitored when the lander is awake and is recorded with a precision of about 0.1% (for noon sunlight levels) at a sample interval of around 30 s until September 2019 and 4 s afterward (Lorenz, Lemmon, Maki, et al., 2020).…”

Geophysical observations of Phobos transits by InSight

“…For Phobos, this can reach around 40%. The current generated by the InSight solar arrays is monitored when the lander is awake and is recorded with a precision of about 0.1% (for noon sunlight levels) at a sample interval of around 30 s until September 2019 and 4 s afterward (Lorenz, Lemmon, Maki, et al, 2020).…”