M2020 Rover Heater Energy Correction Factors for Improving Mission Operations

In the year since NASA's Perseverance Rover landed on Mars, it reached many noteworthy milestones despite the harsh thermal environment where ambient temperatures often dip below −80°C. Perseverance's accomplishments include surpassing the record distance driven on Mars within a Martian Sol, successfully acquiring multiple rock samples, collecting thousands of images, and enabling the first powered flight on another planet. In order to successfully execute these activities and ensure hardware safety in this frigid environment, Perseverance's instruments and actuators must be heated such that the components reach and remain within operational allowable flight temperatures (AFTs). To bring temperatures to operational AFTs, a prescribed preheat is applied prior to the start of the planned activity. The prescribed preheat includes a heating duration and the target temperatures necessary for the component, including the internal parts not monitored by temperature sensors, to reach operational AFTs. Should the component not reach its target temperature within the prescribed preheat duration, Perseverance cannot perform the valuable science activity planned for that Sol. Therefore, the preheat command arguments are based off of a conservative thermal model that assumes a worst-case cold environment to guarantee a successful preheat regardless of the rover orientation with respect to the sun, high wind speeds, and varying dust coverage. By adopting this conservative stance on preheats, the rover planners also consequently allocate more energy to preheats than what is actually used. On certain Sols, this over-allocation can exceed 100Whr; all of which could have instead been allocated to other rover activities. To address the challenge of balancing accurate preheat energy estimates with the requirement to ensure successful preheats, the thermal subsystem has developed energy correction factors based on Perseverance's actual preheat energy usage. By focusing on correcting the energy estimates rather than adjusting the sequenced preheat duration or target temperature, the thermal team balances a strict mission risk posture with the need to maximize mission science return and efficiently allocate energy. This paper focuses on how the energy correction factors were developed; the verification and validation of these energy factors with flight data; and the energy correction factors' impact on rover planning.