Refactoring the Curiosity Rover's Sample Handling Architecture on Mars

The Curiosity Mars rover sample handling hardware and software were architected assuming that end-to-end sampling operations would occur in a single rover position, from acquisition of a powdered sample with a scoop or drill, through to the cleaning out of all sample residue in the sample chain. However, after analysis of the first drilled samples in Yellowknife Bay, the science team wanted to iterate with additional experiments on Mars and in laboratories on Earth to better understand their results and increase the value of science returned. With the architecture as conceived, the time needed to do so was in direct competition with the exploration of other targets and satisfaction of success criteria during the prime mission. The science team desired the capability to "cache" the sample for future use while continuing progress towards mission objectives by driving away and maintaining use of the robotic arm for contact science. Allowing sample to move about freely in this state risked hardware damage, ending the ability to deliver sample using the nominal path. In this paper we present the approaches that were developed to repurpose some of the sampling hardware into a series of caches and catchments that reduced this hardware risk to a level acceptable during the prime mission. This approach presented new challenges for rover planners, who had to learn to command the robotic arm using new routines that were too complicated to manage without assistance. The rover planner Software Simulation ("SSim") was updated to track the turret gravity vector and sample state, generating an execution error or breakpoint as constraints were violated. Sample from the Cumberland drill target was cached for over 9 months, facilitating a number of scientific discoveries. As data accumulated and the mission transitioned into extended operations, the cached sample capability evolved to significantly simplify operations and reduce overhead.