A VERY BRIEF INTRODUCTION TO REMOTE SENSING

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A VERY BRIEF INTRODUCTION TO REMOTE SENSING

• Arden Albee
• April 15, 2004

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THE ELECTROMAGNETIC SPECTRUM
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Modes of EM wave interaction with a surface or
media
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SOLAR RADATION ON THE EARTHS SURFACE
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Atmospheric absorption and useful regions for
remote sensing
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ATMOSPHERIC INTERACTIONSWITH SURFACE RADIANCE
Murchie et al, 2000
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Film Cameras

• Black White ( later color film) provides a
  simple sensor.
• Two dimensions of near-infinite, well-calibrated
  pixels. Radial lines from center point of aerial
  photos preserve angular relationship regardless
  of topography and aircraft tilt and provide a
  basis for building mosaics and geodetic nets.
  Stereo images provide a basis for calculating
  topography.
• The Lunar Surveyor mission scanned film on board
  to digitize it, whereas the later Mars Viking
  mission used vidicons, essentially TV tubes in
  reverse. Most of Viking analysis was done on
  photo printsnot digitally. Digitization of the
  prints is recent.
• Point, line, and 2-D sensors became successively
  available and were used in conjunction with
  filters and spectrometers to build up the
  capability for hyperspectral imaging.

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Scanning approaches for use of point sensor and
line array
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Hyperspectral Image Cube
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Organization of hyperspectral image cube.
Geographic Information Systems (GIS) can be
regarded as an logical extension with the
additional of topographic, geographic, and
demographic data layers. Off-the-shelf systems
are available to easily manipulate such systems
whether terrestrial or martian.
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CHARACTERISTIC IR SPECTRA OF ATMOSPHERE
Basic blackbody curves vary with temperature.
Absorption by gas, ice, dust, etc. provide
spectral information on the radiating material.
Note that Phobos radiation is almost pure black
body.
Christensen, et al
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Decorrelation stretching for highly-correlated
data
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Foreshortening
Layover
Red black indicate shadowed area
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Sources of Widespread Coverage

• LandsatThematic Mapper6 vis-swir, 1 tir
• ASTER (Advanced Spaceborne Thermal Emission and
  Reflection Radiometer)14 vnir-swir-tir
• SRTMShuttle Radar Topographic Mission 30 m
  resolution
• ARCVIEWwidely used GIS software

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Some Nuclear Physics

• Incoming cosmic rays excite Neutrons
• High energy Neutrons collide with atoms,
  releasing gamma rays for specific elements
• Neutrons are slowed by collusion with H to
  epi-thermal (intermediate) and thermal (low)
  energies
• We can measure all of these from orbit and
  obtain chemical composition

(GRS Science Team)
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REVIEW OF SPECTROSCOPIC DATA (L. SODERBLOM, in
MARS, 1992)

• Spectroscopic observations cover 0.3-50 µm, but
  Earth and Mars atmospheric interferences hamper
  accurate mineral identification.
• Water absorption at 3 µm is evident and is
  spatially variable on Mars actual nature of
  water is not clear
• C02 ice (1.2-2.4 µm) is evident near south cap
• Multicolor images show three discrete albedo
  units.
• Reddish, very fine-grained, ferric oxide evident
  in VIS-NIR spectra of light and dark regions Ca
  pyroxene probable in dark regions
• Sheet silicates, palagonite, amorphous material,
  carbonate, sulphate inferred from lander
  chemistry, spectral character, and theory, but
  not confirmed
• CONCEPT OF HIGHLY OXIDIZED AND HYDRATED WEATHERED
  SURFACE PREVAILED

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COMBINED ISM-TES SPECTRAOF SOILS
Mustard Cooper, 2002
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COMBINED ISM-TES SPECTRAOF DARK REGIONS
Mustard Cooper, 2002
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Typical TES spectra from Mars
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• CONCLUSIONS
• The most distinctive geologic units on Mars are
  still the light red, dark red, and dark
  units and they do not match the topographic units
  such as volcanic constructs.
• Easily-weathered igneous minerals (feldspar,
  pyroxene, and olivine) dominate dust-free
  regions. Meaning of andesite is not yet clear.
• Lack of significant chemical weathering of the
  Martian surface indicates a geologic history
  dominated by a cold, dry climate.
• Similar minerals, but different proportions, as
  Martian meteorites plagioclase Ca-pyroxene
  dominate surface. No specific source area for
  meteorites can be identified.
• Widespread light-toned, cliff-forming, layered
  outcrops ( sedimentary rocks) have
  non-diagnostic spectra like dust.

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