Genesis Solar Wind Science Canister Components Curated as Potential Solar Wind Collectors and Reference Contamination Sources

Introduction: The Genesis mission collected solar wind for 27 months at Earth-Sun L1 on both passive and active collectors carried inside of a Science Canister, which was cleaned and assembled in an ISO Class 4 cleanroom prior to launch. The primary passive collectors, 271 individual hexagons and 30 half-hexagons of semiconductor materials, are described in [1]. Since the hard landing reduced the 301 passive collectors to many thousand smaller fragments, characterization and posting in the online catalog remains a work in progress, with about 19% of the total area characterized to date [2, 3, 4]. Other passive collectors, surfaces of opportunity, have been added to the online catalog [4, 5, 6, 7]. For species needing to be concentrated for precise measurement (e.g. oxygen and nitrogen isotopes) an energy-independent parabolic ion mirror focused ions onto a 6.2 cm diameter target [8]. The target materials, as recovered after landing, are described in [9, 10, 11, 12, 13, 14]. The online catalog of these solar wind collectors, a work in progress, can be found at: http://curator.jsc.nasa.gov/gencatalog/index.cfm This paper describes the next step, the cataloging of pieces of the Science Canister, which were surfaces exposed to the solar wind or component materials adjacent to solar wind collectors which may have contributed contamination. The Science Canister prior to launch. The Science Canister, a “tuna can” shape about 75 cm in diameter and 40 cm tall, was cleaned, assembled and closed under nitrogen purge in an ISO Class 4 cleanroom at Johnson Space Center (Fig. 1). It was not opened until on station at Earth-Sun L1 for solar wind collection. Rigorous precautions were taken to assure cleanliness of the canister interior and solar wind collectors [15]. Functionality of the canister is described in [16] (Figs. 2 & 3). The primary passive collectors, the hexagons, were affixed to 5 arrays, each devoted to particular solar wind regimes: two arrays for bulk solar wind, 1 each for coronal mass ejection, high speed and interstream slow speed solar wind. Arrays for coronal mass ejection, high speed and low speed solar wind were shaded until appropriate solar wind regime was determined by on board instruments, then that specific array was deployed (unshaded). The three surfaces of opportunity (gold foil, polished aluminum alloy, metallic glass) and adjacent canister hardware were exposed to solar wind for the duration of collection. The Science Canister structure was aluminum 7075. The interior aluminum surface was bare aluminum – no anodizing or other surface finishing. The array frames were cut by electric discharge machining (EDM) from aluminum 6061 plate. The array frames were phosbrite dipped to remove the EDM dross contamination. Most smaller parts were made from aluminum 6061 with no surface finishing. Final cleaning was done with heated, megasonically energized ultrapure water (>18 M). The structure for the concentrator, assembled at Los Alamos National Laboratory, was gold-coated aluminum with stainless steel grids. Use of lubricants and staking compounds in the canister were severely restricted, the array deployment mechanism was external to the canister interior, and the pressure equalization for re-entry was through a molecular sieve sorbant.