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 Mini-TES is a Fourier Transform Spectrometer covering the spectral range 5-29 micrometers (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 degree of azimuth travel and views from 30 degrees above the nominal horizon to 50 degrees 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 K. One calibration target is located inside the PMA head, the second is on the Rover deck.

Christensen, P.R., et al., The Miniature Thermal Emission Spectrometer for the
                   Mars Exploration Rovers, Journal of Geophysical Research- Planets, 2003.

Instrument Overview
  ===================
    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 Mini-TES is a
    Fourier Transform Spectrometer covering the spectral range
    5-29 micrometers (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 degree of azimuth
    travel and views from 30 degrees above the nominal horizon to 50
    degrees 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 K. 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 263 to 303
    K, with most surface composition data collected at scene
    temperatures >270 K. For these conditions the radiometric precision
    for two-spectra summing is +/-1.8 x10-8 W cm-2 sr-1 /cm-1 between
    450 and 1500 cm-1, increasing to ~4.2 x10-8 W cm-2 sr-1 /cm-1 at
    shorter (300 cm-1) and longer (1800 cm-1) wavenumbers. The absolute
    radiance error will be <5 x10-8 Watt cm-2 sr-1 /cm-1, decreasing to
    ~1 x10-8 Watt cm-2 sr-1 /cm-1 over the wavenumber range where the
    scene temperature will be determined (1200-1600 cm-1). The
    worst-case sum of these random and systematic radiance errors
    correspond 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 2-dimensional rasters and 3-dimensional
    hyperspectral image cubes of varying sizes. The overall Mini-TES
    envelope size is 23.5 cm x 16.3 cm x 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 (SBRS).   Information in this instrument description
    is taken from The Miniature Thermal Emission Spectrometer for the
    Mars Exploration Rovers paper [CHRISTENSENETAL2003]. See this paper
    for more details.
 
 
  Scientific Objectives
  =====================
    The chief scientific objectives of the Mini-TES are:
 
    1) determine the mineralogy of rocks and soils, and
 
    2) determine the thermophysical properties of selected soil patches,
       and
 
    3) determine the temperature profile, dust opacity, water-ice
       opacity, and water vapor abundance in the lower boundary layer of
       atmosphere
 
 
  Calibration
  ===========
    The initial Mini-TES calibration and test was performed at SBRS
    prior to delivery to JPL, and a subset of these tests was performed
    on the integrated Mini-TES/PMA assembly. The objectives of these
    tests were to determine:
 
    (1) the field-of-view definition and alignment;
 
    (2) the out-of-field response;
 
    (3) the spectrometer spectral line shape and spectral sample
        position; and
 
    (4) the spectrometer radiometric calibration.
 
    Bench-level testing of the Mini-TES instrument was performed at SBRS
    in two phases. The first phase consisted of piece-part and
    system-level testing of the spectral performance of each sub-section
    under ambient conditions. The second phase consisted of field of
    view and out-of-field tests conducted before and after vibration and
    thermalvacuum testing to determine and confirm the instrument
    field-of-view and alignment. Mini-TES I was operated for a total of
    166 hours and Mini-TES II was operated for 594 hours at SBRS prior
    to initial delivery to JPL. The Mini-TES spectrometer, without the
    PMA, was tested and calibrated in vacuum at SBRS at instrument
    temperatures of -243, 263, 283, and 303 K. A matrix of calibration
    tests were performed viewing two precision calibration reference
    blackbody standards, one set at 223 K, 243 K, 263 K, and 283 K.
    While the second was varied at temperatures of 145 K, 190 K, 235 K,
    280 K, and 325 K. The Mini-TES/PMA systems were radiometrically
    calibrated in 6 mbar of nitrogen at instrument temperatures of 243,
    273, and 303 K over a range of calibration blackbody temperatures.
    These tests determined:
 
    (1) the emissivity and effective temperature of the internal
        reference surface;
 
    (2) the instrument response function and its variation with
        instrument temperature;
 
    (3) the absolute radiometric accuracy;
 
    (4) the spectrometer noise characteristics; and
 
    (5) the spectrometer gain values.
 
 
  Operational Considerations
  ==========================
    The Mini-TES has many performance requirements, that if not met
    could significantly compromise the quality of the data obtained.
 
    Mineralogic mapping has three measurement requirements:
 
    (1) radiometric accuracy and precision necessary to uniquely
        determine the mineral abundances in mixtures to within 5%
        absolute abundance;
 
    (2) spectral resolution sufficient to uniquely determine the mineral
        abundances in mixtures to within 5% absolute abundance; and
 
    (3) spatial resolution of <25 cm at 10 m distance (25 mrad)
        necessary to resolve and identify individual rocks 0.5 m in size
        or larger in the rover near field.
 
    The determination of atmospheric temperature profiles, aerosols,
    water vapor, condensates has two measurement requirements:
 
    (1) radiometric accuracy and precision necessary to determine the
        opacities of atmospheric dust and ice to +/-0.05 and temperature
        to +/-2 K; and
 
    (2) spectral resolution sufficient to uniquely identify dust,
        water-ice, water-vapor, and sound the atmosphere, and monitor
        their physical and compositional properties.
 
 
  Detectors
  =========
    The Mini-TES uses uncooled detectors to reduce the complexity of the
    fabrication, testing, operation, and rover interface of the
    instrument, while meeting the scientific requirements for the
    investigation. The Mini-TES has a single deuterated triglycine
    sulfate (DTGS) uncooled pyroelectric detector with proven space
    heritage that gives a spatial resolution of 20 mrad; an actuated
    field stop reduces the field of view to 8 mrad.
 
 
  Electronics
  ===========
    Mini-TES uses two Datel DC to DC power converters that accept +11 to
    +36 volts unregulated input voltage and supply +/-5 and +/-15 volts
    regulated output voltage. The Datel converters went through
    significant screening by Raytheon and NASA to validate them for use
    on the MER Mini-TES instruments.  The power converters are mounted
    on the same circuit card as the two SDL 80  mWatt 978 nm laser diode
    assemblies. These laser diodes have also been through significant
    screening for the Mini-TES instruments. The laser diodes are coupled
    into the optics via 1m fiber optic cables. The power connections to
    the spacecraft power bus are through the 21-pin Cannon micro-D
    flight connector located at the base of the Mini-TES interferometer
    baseplate.
 
    Mini-TES uses an uncooled DTGS pyroelectric detector with an
    integrated FET detector package. The bias voltage applied to the FET
    by the pre-amplifier ensures that the DTGS detector's crystals are
    properly poled when power is applied to the instrument.
    Pre-amplification and front-end filtering is performed on the
    preamplifier circuit board amplify the signal and to AC couple the
    detector output to block high frequency oscillations. A +/-12 volt
    regulator supplies power the detector and preamplifier electronics.
 
    The spectrometer circuit board performs the bulk of the analog
    electronics processing. The analog detector signal is passed through
    dual post-amplifier chains, performing the high-frequency boost,
    3-pole Bessel filtering, amplifier gain, and analog signal
    track/hold. The interferogram signal due to the scene is 'boosted'
    to account for the '1/f' roll-off of the detector response and is
    amplified to fill the 16-bit analog to digital converter.  The
    filtering is performed to achieve the desired IR signal bandpass of
    5 to 220 Hz. In addition, the analog signals from the two Hammamatsu
    silicone photodiode fringe signal detectors are passed through the
    fringe post-amplifier and fringe detection circuitry on the
    spectrometer board. The fringe detection electronics use a zero
    crossing comparator to generate the sampling pulse and the constant
    velocity servo feedback fringe clock. The amplified and filtered IR
    signal, fringe analog signal amplitude and the internal instrument
    analog telemetry is then fed into a 16:1 analog multiplexer followed
    by a 16-bit analog to digital converter. The 16-bit digital IR
    data are then transferred to the data buffer on the command and
    control circuit board for formatting and transfer to the Mini-TES
    interface electronics.
 
    The low level command, control and data flow tasks of the Mini-TES
    are controlled by logic in the command and control Field
    Programmable Gate Array (FPGA). The interface electronics parse out
    the low level instrument command parameters that control various
    Mini-TES hardware functions. The Mini-TES command parameters are:
    interferometer motor on/off, amplifier gain high/low, amplifier
    chain primary/redundant, target (shutter) open/close, laser diode1
    on/off, laser heater2 on/off, start-of-scan optical switch
    primary/redundant, and laser heaters on/off.
 
    The flow of the digital interferometer data is controlled by
    additional logic in the command and control board FPGA. After each
    interferometer scan, the 16-bit interferogram data and 16-bit
    telemetry data are moved from the A/D to the input memory buffer on
    the 16-bit parallel data bus. These 16-bit parallel data are then
    sent to the digital multiplexer and serializer electronics where the
    three header words and fourteen digital telemetry words are
    serialized with the 16-bit IR data. The multiplexer, serializer and
    data formatting logic are included in the command and control FPGA.
    The three data header words include: 8-bit sync, 8-bit commanded
    parameter status, 16-bit scan count, and 16-bit interferogram
    sample count. The fourteen 16-bit telemetry words include:
    +5V power, -5V power, +15V power, -15V power, +10V power,
    -10V power,+12V power, -12V power, detector temperature, motor
    temperature, beamsplitter/optics temperature, laser diode1
    temperature, laser diode2 temperature, and fringe signal amplitude.
 
    The Mini-TES timing sequencing electronics are implemented in the
    command and control board FPGA. These electronics generate the
    timing waveforms necessary to control and synchronize instrument
    operation. The timing electronics provide the control and
    synchronization of the amplification, track/hold, multiplexing, and
    analog to digital conversion of the analog signals. They also
    control and synchronize the interferometer servo electronics with
    the data acquisitions. The timing sequencing electronics include the
    fringe delay electronics which are used to correct the sampling
    error due to the phase delays between the fringe and IR analog
    channels. All clocks in the timing sequencer are generated from the
    master clock crystal oscillator which operates  at a frequency of
    14.5152 MHz.
 
    The Mini-TES interferometer servo electronics are located on the
    command and control board and include the digital motor control
    logic and the analog servo drive electronics. The interferometer
    digital drive electronics, located in the FPGA, receive scan timing
    clocks from the timing sequencer electronics and the fringe clock
    from the fringe detection electronics. The motor control logic uses
    these clocks to synchronize the mirror movement with the
    spectrometer data acquisitions. The interferometer analog servo
    drive electronics generate the analog signals that control the
    movement of the TES interferometer moving mirror actuator. The
    moving mirror uses a direct drive Schaeffer linear motor with
    tachometer feedback. The moving mirror tachometer signal is returned
    to the interferometer control electronics to allow active feedback
    control of the actuator. The start of scan is monitored using
    primary and redundant single and double scan optical-interrupters
    that are connected to the moving mirror assembly.
 
 
  Optics
  ======
    The Mini-TES optical system uses a compact Cassegrain telescope
    configuration with a 6.35 mm diameter primary mirror that defines
    the system's aperture stop. Light reflects off the secondary mirror,
    forming the f/12 focal ratio.  The 1.12 cm diameter secondary
    obscures the clear aperture reducing the effective collection area.
    The use of baffles around the telescope housing and secondary mirror
    and the use of diffuse black paint around the optics and within the
    cavity minimizes stray light affects. An anti-reflection coated
    Cadmium Telluride (CdTe) window is located between the exit of the
    telescope's optical path and the entrance of the interferometer
    optical system. This window is tilted so that an internal etalon is
    not created between this surface and the beamsplitter. A flat mirror
    folds the radiance into the plane of the interferometer. All mirror
    surfaces are diamond-turned and gold-coated.
 
    Mini-TES utilizes the identical Michelson interferometer design as
    the TES instruments. The radiance from the main fold mirror passes
    through a 0.635 cm thick Potassium Bromide (KBr) beamsplitter and
    its amplitude is split in two and reflected/transmitted to each arm
    of the interferometer. This beamsplitter is installed in a radial
    3-point mount that allows the beamsplitter to maintain alignment
    over a 373 K operational range (223 K to 323 K). Due to the
    hydroscopic nature of KBr, a dry nitrogen purge during ground
    testing is required to maintain its transmission properties. In
    order to maintain positive purge without over-pressurization, the
    Mini-TES housing has a CdTe window, described above, an exhaust
    port, and check valve.
 
    A fixed mirror is in the reflected path of the interferometer, while
    a constant velocity moving mirror is in the transmission path. The
    moving mirror moves +/-0.25 mm to achieve the spectral sampling
    requirement of 10 cm-1. The wavefronts recombine at the beamsplitter
    and pass through a compensator of identical thickness to the
    beamsplitter to preserve the optical path difference.  This
    recombined radiance is directed by a fold mirror through the 20-mrad
    field stop towards the parabolic focus mirror. This mirror reimages
    the optical pupil onto the on-axis DTGS detector element, which is
    protected by thin (0.05 cm) chemical vapor deposited diamond window.
 
 
  Location
  ========
    Within the Rover's Warm Elecronics Box, at the base of the Pancam
    Mast Assembly
 
 
  Operational Modes
  =================
    1. Full 360 20-mrad panoramic mode
    2. 8-mrad field of view mode
    3. Single spectrum per pixel, 20-mrad mode
    4. Partial panorama mode
 
 
  Measured Parameters
  ===================
    The Mini-TES takes thermal infrared spectra of the target by viewing
    wavelenghts from 5 to 40 micrometers. The Mini-TES calibrated
    radiance is the primary data product for the MER mission. These data
    will be converted to effective emissivity and surface temperature by
    fitting a Planck blackbody function to the calibrated spectrum. The
    emissivity spectra will be converted to mineral abundance using a
    linear deconvolution model and a matrix of mineral spectra from the
    ASU Mineral Library and other sources. The derived surface
    temperature will be used to produce thermal inertia images via a
    thermal model, using data from multiple times of day where possible.
    Attempts will be made to coordinate these diurnal observations with
    the times of TES or THEMIS direct overflights, providing
    simultaneous temperature observations that can be extended to
    broader regions surrounding the rovers.

extracted metadata from PDS3 catalog and
                    modified to comply with PDS4 Information Model

MER-Opportunity Miniature Thermal Emission Spectrometer

Description

Identifier (LID)

Version