M2020 Rover Heater Energy Correction Factors for Improving Mission Operations

In the year since NASA’s Perseverance Rover landedon Mars, it reached many noteworthy milestones despite theharsh thermal environment where ambient temperatures oftendip below -80°C. Perseverance’s accomplishments includesurpassing the record distance driven on Mars within a MartianSol, successfully acquiring multiple rock samples, collectingthousands of images, and enabling the first powered flight onanother planet. In order to successfully execute these activitiesand ensure hardware safety in this frigid environment,Perseverance’s instruments and actuators must be heated suchthat the components reach and remain within operationalallowable flight temperatures (AFTs). To bring temperatures tooperational AFTs, a prescribed preheat is applied prior to thestart of the planned activity. The prescribed preheat includes aheating duration and the target temperatures necessary for thecomponent, including the internal parts not monitored bytemperature sensors, to reach operational AFTs. Should thecomponent not reach its target temperature within theprescribed preheat duration, Perseverance cannot perform thevaluable science activity planned for that Sol. Therefore, thepreheat command arguments are based off of a conservativethermal model that assumes a worst-case cold environment toguarantee a successful preheat regardless of the roverorientation with respect to the sun, high wind speeds, andvarying dust coverage. By adopting this conservative stance onpreheats, the rover planners also consequently allocate moreenergy to preheats than what is actually used. On certain Sols,this over-allocation can exceed 100Whr; all of which could haveinstead been allocated to other rover activities. To address thechallenge of balancing accurate preheat energy estimates withthe requirement to ensure successful preheats, the thermalsubsystem has developed energy correction factors based onPerseverance’s actual preheat energy usage. By focusing oncorrecting the energy estimates rather than adjusting thesequenced preheat duration or target temperature, the thermalteam balances a strict mission risk posture with the need tomaximize mission science return and efficiently allocate energy.This paper focuses on how the energy correction factors weredeveloped; the verification and validation of these energyfactors with flight data; and the energy correction factors'impact on rover planning.