Miniature Thermal Emission Spectrometer for the Mars Exploration Rovers

Abstract

[1] 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 mm (339.50 to 1997.06 cm À1 ) with a spectral sample interval of 9.99 cm À1 . 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 À10 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 Â 10 À8 W cm À2 sr À1 /cm À1 between 450 and 1500 cm À1 , increasing to $4.2 Â 10 À8 W cm À2 sr À1 /cm À1 at shorter (300 cm À1 ) and longer (1800 cm À1 ) wave numbers. The absolute radiance error will be <5 Â 10 À8 W cm À2 sr À1 /cm À1 , decreasing to $1 Â 10 À8 W cm À2 sr À1 /cm À1 over the wave number range where the scene temperature will be determined (1200-1600 cm À1 ). 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-JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. E12, 8064, doi:10.1029/2003JE002117, 2003

Microscopic emission and reflectance thermal infrared spectroscopy: instrumentation for quantitative in situ mineralogy of complex planetary surfaces

“…(1) to the form shown in Eq. (4). In this case all of the radiance (both emitted and reflected) are moved to a single side of the equation.…”

“…These landed spacecraft missions have characterized martian surface in detail using a variety of in situ and landed remote sensing techniques. For example onboard, the MERs, a broad suite of instruments including the alphaparticle x-ray spectrometer (APXS, [1]), Mössbauer (MB, [2]), Microscopic Imager (MI, [3]), the minithermal emission spectrometer (mini-TES, [4]), and the Panoramic Camera (PanCam, [5]) have characterized in detail both Meridiani Planum and a section of the floor of the Gusev Crater. The combination of in situ (e.g., MI, APXS, MB) and remote sensing (e.g., PanCam, mini-TES) instruments has proved to be especially successful in both identifying potential targets at a distance and characterizing those targets in detail [6][7][8][9][10][11][12][13][14][15].…”

“…Depending on the position of the secondary mirror, it is possible to manipulate the nature of the light exiting the optic. For example, in the version mounted to the flight spare mini-TES instrument, a back F-number of 12 is used as it matches the original design of the mini-TES Cassegrain telescope [4].…”

“…Complementary techniques from orbit and at lander scales can allow for the extrapolation of the findings from landers to the rest of the planetary surface. To date, the TES, [22] and mini-TES [4] instruments are the best-matched set of complementary (spectral sampling and wavelength range) instruments sent to both the orbit and the surface of Mars. However, the scales of these measurements are quite disparate, where mini-TES samples outcrop scale variability (centimeter to meter spot sizes) and TES samples regional scale variability (∼3 × 8 km spots when the instrument is nadir looking).…”

A Wind-powered Rover for a Low-Cost Venus Mission

“…An example of the effective operation of thermal emission spectroscopy on a planetary rover is the use of the miniTES instrument on the Mars Exploration Rovers. 30 Infrared detectors (bolometers) can operate at the required temperature, however, to function, the instrument needs to be at a lower temperature than the sample being analyzed. Due to Venus's greenhouse effect, objects in equilibrium at the surface are at nearly the same temperature, meaning the sample will be about the same temperature as the instrument.…”