Santa Barbara Remote Sensing Research Articles

Miniature thermal emission spectrometer for the Mars Exploration Rover

This paper describes results of the calibration of the miniature thermal emission spectrometer (Mini-TES) being 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 [R.J. Peralta, S. Silverman, D. Bates, Raytheon/Santa Barbara Remote Sensing, P. Christensen, G. Mehall, T. Tourville, R. Keehn, G. Cannon, Arizona State University, Miniature thermal emission spectrometer for the Mars Exploration Rover, Proceedings of the SPIE, vol. 4485-09, August 2001] for mission description and instrument design. 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. Mini-TES is designed to provide a key minerological remote sensing component of the MER mission, which includes several other science instruments. 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 Mars Global Surveyor (MGS) thermal emission spectrometer (TES), which was launched in 1996 and is still operational with over 500 million spectra collected to date. Mini-TES design, performance, integration onto the rovers, as well as details of the calibration are discussed. Full instrument and calibration details are the subject of an upcoming Journal of Geophysical Research Mini-TES paper by Christensen, et al.

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

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.

Miniature Thermal Emission Spectrometer for the Mars Exploration Rovers

The Miniature Thermal Emission Spectrometer (Mini‐TES) will provide remote measurements of mineralogy and thermophysical properties of the scene surrounding the Mars Exploration Rovers and guide the rovers to key targets for detailed in situ measurements by other rover experiments. The specific scientific objectives of the Mini‐TES investigation are to (1) determine the mineralogy of rocks and soils, (2) determine the thermophysical properties of selected soil patches, and (3) determine the temperature profile, dust and water‐ice opacity, and water vapor abundance in the lower atmospheric boundary layer. The Mini‐TES is a Fourier Transform Spectrometer covering the spectral range 5–29 μm (339.50 to 1997.06 cm−1) with a spectral sample interval of 9.99 cm−1. The Mini‐TES telescope is a 6.35‐cm‐diameter Cassegrain telescope that feeds a flat‐plate Michelson moving mirror mounted on a voice‐coil motor assembly. A single deuterated triglycine sulfate (DTGS) uncooled pyroelectric detector with proven space heritage gives a spatial resolution of 20 mrad; an actuated field stop can reduce the field of view to 8 mrad. Mini‐TES is mounted within the rover's Warm Electronics Box and views the terrain using its internal telescope looking up the hollow shaft of the Pancam Mast Assembly (PMA) to the fixed fold mirror and rotating elevation scan mirror in the PMA head located ∼1.5 m above the ground. The PMA provides a full 360°of azimuth travel and views from 30° above the nominal horizon to 50° below. An interferogram is collected every two seconds and transmitted to the Rover computer, where the Fast Fourier Transform, spectral summing, lossless compression, and data formatting are performed prior to transmission to Earth. Radiometric calibration is provided by two calibration V‐groove blackbody targets instrumented with platinum thermistor temperature sensors with absolute temperature calibration of ±0.1°C. One calibration target is located inside the PMA head; the second is on the Rover deck. The Mini‐TES temperature is expected to vary diurnally from −10 to +30°C, with most surface composition data collected at scene temperatures >270 K. For these conditions the radiometric precision for two‐spectra summing is ±1.8 × 10−8 W cm−2 sr−1/cm−1 between 450 and 1500 cm−1, increasing to ∼4.2 × 10−8 W cm−2 sr−1/cm−1 at shorter (300 cm−1) and longer (1800 cm−1) wave numbers. The absolute radiance error will be <5 × 10−8 W cm−2 sr−1/cm−1, decreasing to ∼1 × 10−8 W cm−2 sr−1/cm−1 over the wave number range where the scene temperature will be determined (1200–1600 cm−1). The worst‐case sum of these random and systematic radiance errors corresponds to an absolute temperature error of ∼0.4 K for a true surface temperature of 270 K and ∼1.5 K for a surface at 180 K. The Mini‐TES will be operated in a 20‐mrad panorama mode and an 8‐mrad targeted mode, producing two‐dimensional rasters and three‐dimensional hyperspectral image cubes of varying sizes. The overall Mini‐TES envelope size is 23.5 × 16.3 × 15.5 cm, and the mass is 2.40 kg. The power consumption is 5.6 W average. The Mini‐TES was developed by Arizona State University and Raytheon Santa Barbara Remote Sensing.

Prelaunch characteristics of the Moderate Resolution Imaging Spectroradiometer (MODIS) on EOS-AM1

The Moderate Resolution Imaging Spectroradiometer (MODIS), with 36 bands and 0.25-, 0.5-, and 1.0-km geometric instantaneous-fields-of-view (GIFOVs) at nadir, has completed system level testing and has been integrated onto the Earth Observing System (EOS)-AM1 spacecraft, which is slated for launch in 1998. Raytheon Santa Barbara Remote Sensing (SBRS), Goleta, CA, the MODIS developer, has performed extensive characterization and calibration measurements that have demonstrated a system that meets or exceeds most of NASA's demanding requirements. Based on this demonstrated capability, the MODIS Science Team, an international group of 28 land, ocean, atmosphere, and calibration remote-sensing scientists, has commenced delivery of algorithms that will routinely calculate 42 MODIS standard data products postlaunch. These products range from atmospheric aerosols, snow cover, and land and water surface temperature to leaf area index, ocean chlorophyll concentration, and sea ice extent, to name just a few. A description of the Science Team, including members' research interests and descriptions of their MODIS algorithms, can be found at the MODIS homepage (http://ltpwww.gsfc.nasa.gov/MODIS/MODIS.html). The MODIS system level testing included sufficient measurements in both ambient and thermal-vacuum environments to both demonstrate specification compliance and enable postlaunch implementation of radiometric calibration algorithms. The latter will include calculations to account for changes in response versus scan angle, response versus temperature, and response linearity. The system level tests also included performance verification of the onboard calibration systems, including the solar diffuser stability monitor (SDSM), the blackbody (BB), and the spectral radiometric calibration assembly (SRCA), which will enahle monitoring of MODIS performance postlaunch. Descriptions of these subsystems are also on the MODIS homepage.