Ultralight dust wiper mechanism for operation in Mars

摘要

Building on the success of the two rover geologists that arrived to Mars in January, 2004, NASA's next rover mission is planned for the end of the decade. Twice as long and three times as heavy as Spirit and Opportunity, the Mars Science Laboratory rover will collect Martian soil samples and rock cores and analyze them for organic compounds and environmental conditions that could have supported microbial life now or in the past. MSL meteorological package is called REMS (Rover environmental Monitoring Station). This is a scientific instrument designed to provide in situ, near-surface measurements of Temperature (ground surface and atmosphere), Wind, Pressure, Water Vapour and Ultraviolet Radiation (UV). UV observations at the surface will provide important information necessary to asses the habitability of the near surface environment. REMS UV sensor on MSL rover shall be pointing to the Martian sky. From the beginning, deposition of dust particles on the sensor head was considered by NASA's science office a major concern. Such unpredictable phenomena may attenuate the signal received by the optical sensor, and therefore must be considered by far the largest source of error in the sensor. We have studied the error introduced by Martian dust deposition, as well as by frost formation on REMS UV sensor. Several error mitigation strategies such as the use of magnets where evaluated. Finally, a robotic dust wiper was selected as error mitigation system. An optical sensor with a dust wiper was designed, constructed and pre-qualified for MSL mission. Several brushes where fabricated and tested as to maximize its efficiency with submicron particles dust. An Engineering Model of the Sensor including the dust Wiper technology was fabricated and tested. The prototype was subjected to an early qualification campaign under MSL project requirements. Technology performance and qualification results are presented in this paper. The proposed Dust Wiper technology proves to be a simple, yet effective solution to mitigate the error caused by dust on optical sensors or solar panels operating on dirty atmospheres. Using a novel actuator technology based on SMA fibers, the solution represents a very small increase in Mass and a major improvement in system performance. The actuator technology is now being considered for industrial sectors where mass, reliability and cost reduction are key design goals.