VisibleNearInfrared Spectrometer, Thermal Infrared Spectrometer, and Neutron Detector

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Visible/Near-Infrared Spectrometer,Thermal
Infrared Spectrometer,and Neutron Detector

• Life in the Atacama 2004Science Technology
  Workshop
• J. MoerschU. Tennessee

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Overview

• Description of capabilities, operational
  considerations, and outstanding issues for three
  instruments in this years field test
• Visible/Near-Infrared Reflectance Spectrometer
• Thermal Infrared Emission Spectrometer
• Neutron Detector

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Visible/Near-Infrared Reflectance Spectrometer

• Measures reflected light (from Sun or artificial
  source) off target as a function of wavelength.
• Ratio of (measured radiance / incident radiance)
  is Reflectance.
• Reflectance spectra in the 0.35 2.5 µm are
  diagnostic of a number of minerals and organic
  compounds.

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Vis/Near-IR spectra can be used to distinguish
between broad classes of minerals
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Vis/Near-IR spectra can also be used to
distinguish between minerals within a particular
group
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Organic matter can also be identified (e.g.
chlorophyll)
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ASD Portable Vis/Near-IR Field Spectrometer
Spectrometer Laptop Fiber Optic
Pan/Tilt Platform 1 deg. Foreoptic
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ASD Vis/Near-Ir Portable Field Spectrometer
Some Specs Wavelength range 350-2500
nm Spectral Resolution 3-10 nm Field of
View 1 (1.7 cm _at_ 1m range) Time reqd for
one spectrum 1-2 seconds in sunlight Data
interface Parallel cable to computer Data
volume 9kb/spectrum Power Internal NiMH
(2 hour endurance) Dimensions 33 x 11 x 41
cm Mass 8.6 kg Two of these instruments
will be available one on the rover (primary),
one human-carried (backup).
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ASD Vis/Near-IR Portable Field Spectrometer
Calibration accomplished by taking spectrum of a
white reference standard every 10 minutes (more
often if conditions varying).
Spectra may be taken at night or under cloudy sky
using an artificial illumination source. This
also provides access to spectrum in the H20
absorption bands.
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Vis/Near-IR SpectrometerOperational
Considerations

• Spectrometer mounted to rover, with 1-degree
  foreoptic mounted to mast, approximately
  co-located with panoramic cameras
• Images may be used to select targets. Instrument
  may also be pointed in the blind using azimuth
  and elevation angles.
• Targets can be individual points or raster
  patterns.
• Spot size is 1.7 cm _at_ 1m range. With artificial
  illumination source, spot size is about 5cm.
• Calibration target mounted on rover deck. Dark
  current calibration (internal to instrument)
  also possible.
• Data will be returned as binary files. RST will
  have software to turn these into spectra, and
  spectral libraries for compositional analysis.

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Vis/Near-IR SpectrometerOpen Issues

• Backup spectrometer will be shipped off to
  manufacturer for spectral resolution upgrade
  before field expedition.
• Best method for shipping to Chile?
• How to target if backup spectrometer used?
• Other issues on CMU side? Integration with
  rover? Software for targeting and data product
  tracking?

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Thermal Infrared Emission Spectrometer

• Measures emitted radiance from target
• Ratio of
• (Measured target radiance /
• Radiance of perfect blackbody at same
  temperature)
• is called Emissivity.
• Emissivity spectra are diagnostic of mineral/rock
  compositions

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Example Thermal IR spectra
After Christensen et al., 1992
Christensen et al. 1985
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Boba Fett Hill Contact (Marsokhod 1999 experiment)
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Foreoptic
Optical head
Mike
Computer controller
Instrument will be operated as standalone,
simulated to be on the rover.
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ASU DP Thermal Infrared Field Spectrometer
Some Specs Wavelength range 8 12
µm Spectral Resolution 6 cm-1 (0.04 - .09
µm) Time reqd for one spectrum lt10
minutes Field of view 4.8 (8.2 cm _at_ 1m
range) Data interface Integrated
computer Data volume 36 kb/spectrum Power
12V 7-hour battery pack Dimensions 36 x 20 x
23 cm Mass 7 kg Coolant Liquid nitrogen
in on-board dewar
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DP Portable Thermal-IR Field Spectrometer
Calibration

• Each target spectrum requires four measurements
• Target spectrum
• Hot blackbody spectrum
• Cold blackbody spectrum
• Downwelling radiance spectrum measurement
• Calibration of raw spectra will be accomplished
  by the RST using supplied software

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Thermal-IR SpectrometerOperational Considerations

• Spectrometer is not mounted to the rover
  operated by field personnel in a stand-alone mode
  at the end of each sol.
• Instrument can only be used in single point
  mode rastering not possible because it has no
  precise az/el pointing (its pointed by eye).
• Calibration spectra will be acquired with each
  spectrum or set of spectra at a single site.
• Spectral acquisition can be cumbersome. At
  beginning of field test, a limit of 6 spectra per
  sol will be imposed. If we find we can handle
  more, we will advise the RST of a higher limit
  per sol.
• Data will be returned as raw radiance spectra of
  the target and calibrators. RST will have
  software to turn these into spectra, and spectral
  libraries for compositional analysis.

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Thermal IR SpectrometerOpen Issues

• Need to find a source of liquid nitrogen in town
  
• Best method for shipping to Chile?
• How to identify targets?

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Neutron Detector

• Counts neutrons coming up from the surface in two
  different energy ranges a) all energies, b)
  energies above the Cd-cutoff (epithermals)
• Ratio of (All Epithermal) / Epithermal is
  sensitive to amount of hydrogen within sensing
  radius (0.5 1m)

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Neutron Detector Physical processes
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Neutron Detector Sensitivity
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Neutron Detector Systematic Traverse Measurements
Pure Dry
Traverse measurements
Pure Wet
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Neutron detector
Some Specs Time reqd for one measurement
10 minutes Sensing radius (depends on density)
0.5 1.0 m Data interface Serial RS-232
to Tablet PC Data volume A few bytes per
measurement Power 14V laptop
batteries Radiation source Encapsulated
pellet of 252Cf (gives about 104
neutrons/second)
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Neutron DetectorOperational Considerations

• Instrument is not mounted to the rover operated
  by field personnel in a stand-alone mode at the
  end of each sol. Instrument will be
  wagon-mounted to keep the geometry of the
  detector tubes fixed.
• Instrument is not pointable it simply senses
  hydrogen abundance within a certain range.
• Measurements with this instrument should not yet
  be interpreted in terms of absolute H abundances,
  but as relative abundances (e.g., wetter or
  dryer).
• Not possible to distinguish between possible
  sources of H could be water, could be in
  minerals.
• At beginning of field test, a limit of 6
  measurements per sol will be imposed. If we find
  we can handle more, we will advise the RST of a
  higher limit per sol.
• Data will be returned as a single number at each
  position, the ratio of thermal/epithermal counts.

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Neutron DetectorOpen Issues

• Co-I was recently in an accident may or may not
  be healed in time. His presence may be critical
  to the success of this instrument.
• Finding an appropriate isotopic source and
  getting it to/from Chile is a big issue not yet
  resolved.
• Need to buy a wagon in Chile.
• Best method for shipping instrument to Chile?
• How to identify targets from RST?

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Personnel

• Jeff Moersch (UT)
• Field team lead on all three instruments
• Darrell Drake (LANL)
• Field team neutron detector
• Mike Wyatt (ASU)
• Field team thermal infrared spectrometer
• Mike Rampey (UT)
• Field team
• Jen Piatek (UT)
• Remote science team lead on all three instruments