117 Mars 2020 Rover Adaptive Caching Assembly:  Caching Martian Samples for  Potential Earth Return  

Milo Silverman* and Justin Lin* 

Abstract  

The Adaptive Caching Assembly  (ACA) is part of the Sampling and Caching System on the Mars 2020  Perseverance Rover and consists of multiple stations that process , hermetically seal,  and store sample  tubes containing collected Martian material, either rock cores or regolith  samples, in preparati on for caching  on the surface of Mars. The ACA stations consist of seven active degrees -of-freedom,  as well as a large  number of passive mechanisms that must operate in extreme Mars temperature and pressure conditions .  A robotic arm within the Rover manipulates the sample tubes between ACA stations as part of an end- toend sampling sequence and utilizes a compliant end effector to accommodate misalignments during station  interactions . Stringent hardware c leanliness requirements were dictated to ensure collected samples would  not be compromised, which significantly impacted  the design, assembly, and test operations  of the ACA.   Three ACAs  were assembled to support ground testing and flight operations , which  were exposed to  environmental testing to validate functionality in Mars -like conditions . A number of challenges existed from  design through test, including volume constraints, mechanism controllability  and operation, the effects of  tight tolerances, and c leanliness requirements.  

Introduction  

The Adaptive Caching Assembly is part of the Sampling and Caching System (SCS) on the Perseverance  Rover (Figure 1), which successfully launched on July 30, 2020, and will land on Mars in February  2021 .  The Rover’s primary mission has a duration of one- and-a-half Martian years, or approximately three Earth  years . The Mars 2020 Perseverance Rover design is heavily based on the Mars Science Laboratory (MSL)  Curiosity Rover, which has been operating on the surface of Mars since August 2012; however,  Perseverance  is outfitted with a new sampling system and scientific instrument suite to address the new  mission goals . The Perseverance Rover has four main science objectives:  looking for habitability, seeking  biosignatures, caching samples, and preparing for humans [1] . Seven science instruments are located on  the Rover to address many  of these objectives  via remote and in- situ observations and operations . 

Sampling and Caching System  

The Sampling and Caching System’s purpose is to create the cache of scientifically selected and  documented Martian materials by collecting rock cores and regolith samples, packaging these materials  into hermetically sealed sample tubes, and depositing them on the Martian surface for potential return to  Earth . These packaged samples must meet stringent science- driven contamination control requirements  which drive the physical architecture and hardware implementation: less than 10 ppb organic carbon, less  than 1 terrestrial viable organism per sample, and limits on inorganic contamination on elements that impact  returned sample science. SCS must also perform rock abrasion and dust removal  operations to prepare  surfaces for sci entific instrument assessment , and then position the instruments for the assessment.  

SCS consists of two robotic systems which work in conjunction with each other to perform the mission  functions:  one MSL- like robotic system on the outside of the Rover c onsisting of a Robotic Arm and Turret,  and one new autonomous r obotic system on the inside of the Rover called the Adaptive Caching Assembly.  

* Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA  

Proceedings of the 45th Aerospace Mechanisms Symposium, NASA Johnson Space Center, 2020