Robotic Operations for the First Sample Depot on Mars

The Perseverance rover has completed a very successful 2.5 years on Mars. It has filled 24 of the 43 sample tubes it brought to Mars and completed the Three Forks Sample Depot on January 28, 2023, where it deposited 10 of these samples on the surface of Mars. Each deposited sample was sealed within a Returnable Sample Tube Assembly (RSTA) and attached glove assembly (RGA). Creation of this sample depot has satisfied all of the prime mission requirements. The Mars Sample Return mission aims to bring some of the samples that Perseverance collects from Mars to Earth, either via direct delivery from the Perseverance rover to the Sample Retrieval Lander (SRL), or by deploying Sample Recovery Helicopters (SRH) to fly to the samples and collect them. This paper describes the strategic planning and tactical execution of the mobility, robotic arm, sampling and imaging activities that led to the very successful depot creation. A number of factors had to be considered including SRH access, communication obstructions, view for imaging, and contingency handling. It discusses how the strategic planning arrived at the plan for alternating two main types of sols: drop and image, and drive and photoshoot. Drop and image choreographed moves between the Perseverance external robotic arm and the Adaptive Caching Assembly (ACA) inside the rover, which has a second robotic arm - the Sample Handling Arm - to image the sample before and after depositing it on the surface. Drive and photoshoot consists of backing up and taking mid-drive images of the dropped sample. During the 42 Martian days (sols) that it took to create and document the Three Forks depot, the rover drove 207.93 meters, dropped 10 sample RGAs, and took 4000 images. Completion of this sample depot ensures that there will be samples for the Mars Sample Return mission to transport back to Earth for the first time.