Successful Mars remote sensors, MO THEMIS and MER Mini-TES

Abstract This paper describes results of the calibration of the miniature thermal emission spectrometer (Mini-TES) and the thermal emission imaging system (THEMIS) built by Raytheon Santa Barbara Remote Sensing (SBRS) under contract to Arizona State University (ASU). This paper also serves as an update to an earlier paper (Silverman et al., 2003) for mission description and instrument designs (Schueler et al., 2003). A major goal of the Mars exploration program is to help determine whether life ever existed on Mars via detailed in situ studies and surface sample return. It is essential to identify landing sites with the highest probability of containing samples indicative of early pre-biotic or biotic environments. Of particular interest are aqueous and/or hydrothermal environments in which life could have existed, or regions of current near-surface water or heat sources [Exobiology_Working_Group, 1995, An Exobiological Strategy for Mars Exploration, NASA Headquarters]. The search requires detailed geologic mapping and accurate interpretations of site composition and history in a global context. THEMIS and Mini-TES were designed to do this and builds upon a wealth of data from previous experiments. Previous experiments include the Mariner 6 / 7 Mars infrared radiometer (MIR) and infrared spectrometer [G.C. Pimentel, P.B. Forney, K.C. Herr, Evidence about hydrate and solid water in the martian surface from the 1969 Mariner infrared spectrometer, Journal of Geophysical Research 79(11) (1974) 1623–1634], the Mariner 9 infrared interferometer spectrometer (IRIS) [B. Conrath, R. Curran, R. Hanel, V. Kunde, W. Maguire, J. Pearl, J. Pirraglia, J. Walker, Atmospheric and surface properties of Mars obtained by infrared spectroscopy on Mariner 9, Journal of Geophysical Research 78 (1973) 4267–4278], the Viking infrared thermal mapper (IRTM) [H.H. Kieffer, T.Z. Martin, A.R. Peterfreund, B.M. Jakosky, E.D. Miner, F.D. Palluconi, Thermal and albedo mapping of Mars during the Viking primary mission, Journal of Geophysical Research 82 (1977) 4249–4292], the Phobos Termoscan [A.S. Selivanov, M.K. Naraeva, A.S. Panfilov, Y.M. Gektin, V.D. Kharlamov, A.V. Romanov, D.A. Fomin, Y.Y. Miroshnichenko, Thermal imaging of the surface of Mars, Nature, 341 (1989) 593–595], and the continuing Mars global surveyor (MGS) mission using the Mars orbiter camera (MOC) [M.C. Malin, K.S. Edgett, Mars global surveyor Mars orbiter camera: interplanetary cruise through primary mission, Journal of Geophysical Research 106 (2001) 23, 429–23, 570] and MGS thermal emission spectrometer (TES) [P.R. Christensen, J.L. Bandfield, V.E. Hamilton, S.W. Ruff, H.H. Kieffer, T. Titus, M.C. Malin, R.V. Morris, M.D. Lane, R.N. Clark, B.M. Jakosky, M.T. Mellon, J.C. Pearl, B.J. Conrath, M.D. Smith, R.T. Clancy, R.O. Kuzmin, T. Roush, G.L. Mehall, N. Gorelick, K. Bender, K. Murray, S. Dason, E. Greene, S.H. Silverman, M. Greenfield, The Mars global surveyor thermal emission spectrometer experiment: investigation description and surface science results, Journal of Geophysical Research 106 (2001a) 23, 823–23, 871]. TES has collected hyperspectral images (up to 286 spectral bands from 6– 50 μ m ) of the entire martian surface, providing an initial global reconnaissance of mineralogy and thermophysical properties [J.L. Bandfield, Global mineral distributions on Mars, Journal of Geophysical Research 107 (2002) 10.1029/2001JE001510; S.W. Ruff, P.R. Christensen, Bright and dark regions on Mars: particle size and mineralogical characteristics based on thermal emission spectrometer data, Journal of Geophysical Research, 2002, in press]. By covering the key 6.3– 15.0 μ m region in both TES and THEMIS, it is possible to combine TES fine spectral resolution with THEMIS fine spatial resolution to achieve a global mineralogic inventory at the spatial scales necessary for detailed geologic studies within the Odyssey data resources. Mini-TES is a single detector Fourier transform spectrometer (FTS), covering the spectral range 5– 29 μ m at 10 cm - 1 spectral resolution. Launched in June 2003, one Mini-TES instrument will fly to Mars aboard each of the two missions of NASA's Mars Exploration Rover Project (MER), named Spirit and Opportunity. The first Mini-TES unit was required to meet a two-year development schedule with proven, flight-tested instrumentation. Therefore, SBRS designed Mini-TES based on proven heritage from the successful MGS TES. THEMIS is based on “bolt-together” pushbroom optics and uncooled silicon microbolometer focal plane array (FPA) technology. Sometimes dubbed “Mars Landsat,” THEMIS was launched in 2001 on Mars Odyssey, and provides guidance for future lander missions now in preparation for launch. Advanced materials and optical machining allow THEMIS low-scatter, reflective, wide field-of-view (WFOV) pushbroom optics for relatively long dwell-time compared to narrow FOV optics requiring cross-track scanning for equivalent spatial resolution. This allows uncooled silicon microbolometer FPAs, with less signal sensitivity than cryogenically cooled photo-diode FPAs, to meet the THEMIS sensitivity requirements. Instrument design, performance, integration, as well as details of the calibration are discussed. Full instrument and calibration details are available in the Journal of Geophysical Research Mini-TES and THEMIS papers by Christensen et al.