HR: 10:20h
AN: SH32A-01    [Abstracts]
TI: Genesis Science Team Report on Mission Status
AU: * Burnett, D S
EM: burnett@gps.caltech.edu
AF: Cal Tech, Geological and Planetary Sciences, Pasadena, CA 91125 United States
AB: The Genesis Discovery Mission exposed pure materials to the solar wind at the L1 Lagrangian point for 27 months between December 2001 and April 2004. These were returned for analysis in terrestrial laboratories in Sept 2004. The general science objectives for Genesis are: (1) measure solar isotopic abundance ratios to the precision required for planetary science problems, (2) improve the accuracy of photospheric elemental abundances by a least a factor of three, (3) provide independent analyses of the 3 major solar wind regimes and (4) provide a reservoir of solar matter for subsequent studies. Based on these general objectives, we are working towards a list of 18 specific prioritized measurement objectives, the first 5 of which are isotopic measurements. The two highest priority objectives are the isotopic compositions of O and N; to obtain a higher signal to background ratio for these elements, a concentrator (focusing ion telescope) was built at LANL to provide a factor of 20 fluence enhancement for elements lighter than P on a 30 mm radius target. The concentrator performed well in flight. A variety of other collector materials, tailored to specific analytical approaches, were mounted in 5 arrays of 55 hexagons, 4 cm point to point. Three of the arrays were used to provide the independent regime (coronal hole, low speed interstream, and coronal mass ejection) samples. The solar wind regime was measured by LANL Solar Wind Monitors on the Genesis spacecraft and the appropriate array exposed while the inappropriate array remained shielded. Array switchouts were carried out flawlessly during flight. Sample analyses have been slowed considerably by a parachute deployment failure which caused a crash of the sample return capsule upon reentry and by the presence of an in-flight contamination film, affectionately referred to as the brown stain. The crash has led to major loss of collector materials, along with significant pitting and scratching of the surviving materials. The concentrator target materials were recovered, essentially intact. If a potentially analyzable size fragment is defined as 3mm smallest dimensions, we now have roughly15,000 samples. The crash produced high densities of particulate surface contamination in addition to the surface pits and scratches. For those materials compatible with wet cleaning (e.g. Si) we have been able to remove essentially all particles greater than 5 microns in size and significantly reduce the densities of smaller particles. The brown stain is variable in thickness (typically 50 Angstroms) and results in minor solar wind attenuation; however, it does interfere with almost all analysis methods and must be removed. We have had some success with atomic O etching, and this is being vigorously pursued at present. Analytical efforts are proceeding on a broad front at present, and sample requests can be made to the Genesis Sample Curator, Judy Allton at the Johnson Space Center. Our original measurement objectives are challenged to various degrees, but none appear impossible at this point. Preliminary data on H, He, Ne, Ar, Mg, and Fe fluences will be presented at this meeting.
DE: 6040 Origin and evolution
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005