Steven H. Silverman

Mars Global Surveyor Thermal Emission Spectrometer experiment: Investigation description and surface science results

The Thermal Emission Spectrometer (TES) investigation on Mars Global Surveyor (MGS) is aimed at determining (1) the composition of surface minerals, rocks, and ices; (2) the temperature and dynamics of the atmosphere; (3) the properties of the atmospheric aerosols and clouds; (4) the nature of the polar regions; and (5) the thermophysical properties of the surface materials. These objectives are met using an infrared (5.8- to 50-μm) interferometric spectrometer, along with broadband thermal (5.1- to 150-μm) and visible/near-IR (0.3- to 2.9-μm) radiometers. The MGS TES instrument weighs 14.47 kg, consumes 10.6 W when operating, and is 23.6×35.5×40.0 cm in size. The TES data are calibrated to a 1-σ precision of 2.5−6×10−8 W cm−2 sr−1/cm−1, 1.6×10−6 W cm−2 sr−1, and ∼0.5 K in the spectrometer, visible/near-IR bolometer, and IR bolometer, respectively. These instrument subsections are calibrated to an absolute accuracy of ∼4×10−8 W cm−2 sr−1/cm−1 (0.5 K at 280 K), 1–2%, and ∼1–2 K, respectively. Global mapping of surface mineralogy at a spatial resolution of 3 km has shown the following: (1) The mineralogic composition of dark regions varies from basaltic, primarily plagioclase feldspar and clinopyroxene, in the ancient, southern highlands to andesitic, dominated by plagioclase feldspar and volcanic glass, in the younger northern plains. (2) Aqueous mineralization has produced gray, crystalline hematite in limited regions under ambient or hydrothermal conditions; these deposits are interpreted to be in-place sedimentary rock formations and indicate that liquid water was stable near the surface for a long period of time. (3) There is no evidence for large-scale (tens of kilometers) occurrences of moderate-grained (>50-μm) carbonates exposed at the surface at a detection limit of ∼10%. (4) Unweathered volcanic minerals dominate the spectral properties of dark regions, and weathering products, such as clays, have not been observed anywhere above a detection limit of ∼10%; this lack of evidence for chemical weathering indicates a geologic history dominated by a cold, dry climate in which mechanical, rather than chemical, weathering was the significant form of erosion and sediment production. (5) There is no conclusive evidence for sulfate minerals at a detection limit of ∼15%. The polar region has been studied with the following major conclusions: (1) Condensed CO2 has three distinct end-members, from fine-grained crystals to slab ice. (2) The growth and retreat of the polar caps observed by MGS is virtually the same as observed by Viking 12 Martian years ago. (3) Unique regions have been identified that appear to differ primarily in the grain size of CO2; one south polar region appears to remain as black slab CO2 ice throughout its sublimation. (4) Regional atmospheric dust is common in localized and regional dust storms around the margin and interior of the southern cap. Analysis of the thermophysical properties of the surface shows that (1) the spatial pattern of albedo has changed since Viking observations, (2) a unique cluster of surface materials with intermediate inertia and albedo occurs that is distinct from the previously identified low-inertia/bright and high-inertia/dark surfaces, and (3) localized patches of high-inertia material have been found in topographic lows and may have been formed by a unique set of aeolian, fluvial, or erosional processes or may be exposed bedrock.

Thermal emission spectrometer experiment: Mars Observer mission

Thermal infrared spectral measurements will be made of the surface and atmosphere of Mars by the thermal emission spectrometer (TES) on board Mars Observer. By using these observations the composition of the surface rocks, minerals, and condensates will be determined and mapped. In addition, the composition and distribution of atmospheric dust and condensate clouds, together with temperature profiles of the CO2 atmosphere, will be determined. Broadband solar reflectance and thermal emittance measurements will also be made to determine the energy balance in the polar regions and to map the thermophysical properties of the surface. The specific science objectives of this investigation are to determine (1) the composition and distribution of surface materials, (2) the composition, particle size, and spatial and temporal distribution of suspended dust, (3) the location, temperature, height, and water abundance of H2O clouds, (4) the composition, seasonal behavior, total energy balance, and physical properties of the polar caps, and (5) the particle size distribution of rocks and fines on the surface. The instrument consists of three subsections: a Michelson interferometer, a solar reflectance sensor, and a broadband radiance sensor. The spectrometer covers the wavelength range from 6 to 50 μm (∼1600–200 cm−1) with nominal 5 and 10 cm−1 spectral resolution. The solar reflectance band extends from 0.3 to 2.7 μm; the broadband radiance channel extends from 5.5 to 100 μm. There are six 8.3-mrad fields of view for each sensor arranged in a 3 × 2 array, each with 3-km resolution at the nadir. Uncooled deuterated triglycine sulphate (DTGS) pyroelectic detectors provide a signal-to-noise ratio (SNR) of over 500 at 10 μm for daytime spectral observations at a surface temperature of 270 K. The SNR of the albedo and thermal bolometers will be approximately 2000 at the peak signal levels expected. The instrument is 23.6 × 35.5 × 40.0 cm, with a mass of 14.4 kg and an average power consumption of 14.5 W. The approach will be to measure the spectral properties of thermal energy emitted from the surface and atmosphere. Emission phase angle studies and day-night observations will be used to separate the spectral character of the surface and atmosphere. The distinctive thermal infrared spectral features present in minerals, rocks, and condensates will be used to determine the mineralogic and petrologic character of the surface and to identify and study aerosols and volatiles in the atmosphere.

High efficiency diode doubler with conjugate- matched antennas

A high efficiency harmonic re-radiator, consisting of a diode doubler and conjugate-matched receive and transmit antennas, is described. The device operates by receiving a 1.3 GHz signal and re-radiating a 2.6 GHz signal. The doubler design is optimized for low input power operation and provides 1% conversion efficiency at -30 dBm input. It is shown that utilizing proper harmonic terminations in the computer simulations is critical for accurate performance prediction.

Miniature thermal emission spectrometer for the Mars Exploration Rover

This paper describes the dual-mission Mars 2003 Miniature Thermal Emission Spectrometer (Mini-TES) being built by Raytheon Santa Barbara Remote Sensing (SBRS) under contract to Arizona State University (ASU). Mini-TES is a single detector Fourier Transform Spectrometer (FTS), covering the spectral range 5-29 microns (micrometers ) at 10 cm-1 spectral resolution. Scheduled for launch in 2003, one Mini-TES instrument will fly to Mars aboard each of the two missions of NASAs Mars Exploration Rover Project (MER). Mini-TES is designed to provide a key minerological remote sensing component of the MER mission, which includes several other science instruments. Originally intended for the Athena Precursor Experiment (APEX) slated for a 2001 launch, 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 successfully completed its intended mission of one Martian year (two earth years) with over 100 million spectra collected to date, and counting. Relevance of the Mini-TES to MER science, overall design, performance, assembly and test flow as well as details of the hardware fabricated at SBRS, are discussed.

Advanced planetary thermal spectroscopy

Advanced technology miniaturization of the 14.5-kg Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) allows new scientific missions. A 2to 3-kg mini-TES is being developed under a NASA Planetary Instrument Definition and Development (PIDDP) effort by Arizona State University and Santa Barbara Remote Sensing. Mini-TES will obtain spectra from 6 to 40 /spl mu/m, applicable to flyby spacecraft atmospheric and surface analyses to help select planets and smaller objects for examination from orbit. From low-altitude, mini-TES could assess aerosols, ice and vapor abundance and composition, as well as vertical temperature profiles, and examine surface composition with 1-km to 100-m resolution. Mini-TES could analyze ice, rock, and soil with from 1-m to 20-cm resolution from a fixed lander down to a centimeter from a rover, as well as provide surface-based atmospheric analyses.

Miniature thermal emission spectrometer for Mars 2001 Lander

This paper describes the Mars 2001 Miniature Thermal Emission Spectrometer (Mini-TES) being built by Raytheon Santa Barbara Remote Sensing (SBRS) under contract to Arizona State University (ASU). Mini-TES is a point (single-pixel) Fourier Transform Spectrometer (FTS), covering the spectral range 5 - 28 microns (micrometer) at 10 cm-1 spectral resolution. It is part of the Athena Precursor Experiment (APEX) that will fly to Mars on board NASAs Mars 2001 Lander mission. Mini-TES is designed to provide a key mineralogical remote sensing component of the APEX mission, which includes several other science instruments. Even though Mini-TES is a new design, the Athena mission required proven, flight-tested instrumentation to meet a two-year development schedule. 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 currently providing excellent science data from the MGS, in orbit about Mars. Mini-TES occupies only 15% of the volume and is 83% lighter than MGS TES, yet nearly all the design and technology elements of Mini-TES are direct descendants of proven flight components from MGS TES. Relevance of the Mini- TES to APEX science, overall design, performance, as well as details of the hardware being fabricated at SBRS, are discussed. Possible applications to future missions are also addressed.

Mars exploration via thermal emission spectroscopy

The National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory, the Arizona State University (ASU), and Raytheon Space and Airborne Systems (SAS) Santa Barbara Remote Sensing (SBRS) have executed a series of successful Mars exploration missions. These have recently been publicized on television and the internet with the early 2004 Mars Exploration Rover (MER) mission geological robots that have revolutionized our detailed knowledge of the planets geology and atmosphere. This latest mission success has its foundation in missions dating back to 1969. Over the past thirty-five years NASA has demonstrated a long-term commitment to planetary science and solar system exploration that continues with a commitment recently expressed by President Bush and codified in a reorganization of the NASA space sciences mission directorate. This paper reports on a small but exciting aspect of this sweeping NASA program, and illustrates the benefits and efficiency with which planetary and solar system exploration can be accomplished. Key in the success is the vision not only of NASA in general, but of the mission Principal Investigator, in particular. The specific series of missions leading to MER contains an underlying vision of carefully planned geological investigations using remote sensing instrumentation, starting with broad survey, leading to more finely resolved global imaging, and finally to landing instrumentation capable of detailed rock and soil analyses. The mission started with broad and relatively coarse spatial resolution orbital surveys with fine spectral capability focused on identifying the overall geological and atmospheric character of the planet accomplished from 1996 to the present conducted by the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES). This led to the more detailed global imaging at finer spatial resolution offered by the Mars 2001 Odyssey Mission Thermal Emission Imaging System (THEMIS) which identified specific landing sites of interest for detailed exploration. The mission culminated in the recent MER lander geological analyses conducted by the mini-TES instruments carried by the rovers. This series of remote sensing investigations has set the stage for a new era in solar system exploration.

Performance of the miniature thermal emission spectrometer (Mini-TES) for Mars 2001 Lander

This paper describes the science rationale, design, and the measured performance of the Miniature Thermal Emission Spectrometer (Mini-TES). Mini-TES is a single detector Fourier Transform Spectrometer (FTS), covering the spectral range 5-28 /spl mu/m at 10 cm/sup -1/ spectral resolution. The primary mission of Mini-TES will be to obtain mineralogical data for rocks and soil surrounding the 2001 Lander. Mini-TES also plays a key role in the Mars sample return missions in 2003 and 2005. The Mini-TES design is based on proven heritage from the successful Mars Global Surveyor (MGS) TES which is currently providing excellent science data from Mars orbit. Mini-TES has only 15% of the volume and 17% of the mass of MGS TES. The use of TES design heritage and commercial technology in a few key areas has led to a low-cost, robust design. Additional applications are anticipated for the Mini-TES in the exploration of other planets, moons, asteroids, and comets.

Miniaturization of the Thermal Emission Spectrometer (TES) electronics for the Mars 2001 Lander

This paper will describe the miniaturization of the Thermal Emission Spectrometer (TES) electronic system for use in the Miniature-TES (Mini-TES) being built for Arizona State University. Mini-TES will be used to measure thermal emission for mapping of surface minerals on Mars. Mini-TES is a single pixel, Fourier Transform Spectrometer, covering 5 - 28 micrometer at 10 cm-1 resolution. The Mini-TES electronics incorporate modern Field Programmable Gate Array (FPGA) technology, surface mount designs, and simplified command, control and data protocol allowing for a 4 fold reduction in the electronics subsystem. Use of the Lander computer for shared signal processing further help to reduce the Mini-TES complexity. Details of the specific flight hardware design, actual hardware fabrication and initial test results will be discussed.