Remote sensing systems

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Remote sensing systems

  1. 1. Remote Sensing Systems
  2. 2. Early Satellite Sensing • Spy satellites gave exquisite but very local views and were classified • Even before satellites were launched, it was clear that color imaging was essential • Best images were from manned spacecraft – Low latitude – Limited coverage in space and time – Almost all oblique
  3. 3. Gemini XII, 1968 (410 miles)
  4. 4. Early Satellite Sensing • Meteorological satellites gave hints of what might be possible – Snow coverage – Sea ice – Glaciers – Gross geological structures
  5. 5. Nimbus I image 1964
  6. 6. Landsat • Landsat 1 1972-1978 • Landsat 2 1975-1981 • Landsat 3 1978-1983 • Landsat 4 1982-1993 • Landsat 5 1984, still functioning • Landsat 6 1993, failed to reach orbit • Landsat 7 1999, still functioning, but with faulty scan line corrector (May 2003) • Landsat Data Continuity Mission, scheduled for 2012
  7. 7. Two Key Features of Landsat • Orbits are sun synchronous: satellite crosses equator southbound on day side at about 10 AM local time • Orbits repeat ground track precisely every 14-18 days (Revisit period) • A term to know: Nadir = point directly below (opposite of Zenith)
  8. 8. Early Landsat • Originally modeled on Nimbus weather satellite system • Landsat 1 observed in Green, Red and two IR bands with 80-m resolution • Landsat 3 had 30-m resolution • Landsat 3 added a fifth thermal IR band but it failed • Landsat 4: 7 bands • Landsat 7: 15 m resolution panchromatic
  9. 9. Failed Experiment • President Jimmy Carter recommended private sector operation of Landsat, 1979 • Earth Observation Satellite Company (EOSAT), a partnership of Hughes Aircraft and RCA, was awarded ten year contract to operate Landsat, 1985 • EOSAT operated Landsats 4 and 5 and had exclusive rights to market Landsat data. • EOSAT needed repeated bailouts • Congress passed Land Remote Sensing Policy Act (Public Law 102-555) and returned Landsat to public domain, 1992
  10. 10. Landsat 7 Bands 1 0.45-0.52µm Blue-Green 30 m 2 0.52-0.60 µm Green 30 m 3 0.63-0.69 µm Red 30 m 4 0.76-0.90 µm Near IR 30 m 5 1.55-1.75 µm Mid-IR 30 m 6 10.40-12.50 µm Thermal IR 60 m 7 2.08-2.35 µm Mid-IR 30 m 0,52-0.90 µm Panchromatic 15 m
  11. 11. Uses of Landsat 7 Bands 1. Coastal water mapping, soil/vegetation discrimination, forest classification, man-made feature identification 2. Vegetation discrimination and health monitoring, man- made feature identification 3. Plant species identification, man-made feature identification 4. Soil moisture monitoring, vegetation monitoring, water body discrimination 5. Vegetation moisture content monitoring 6. Surface temperature, vegetation stress monitoring, soil moisture monitoring, cloud differentiation, volcanic monitoring 7. Mineral and rock discrimination, vegetation moisture content
  12. 12. False Color Images • Near IR (ETM+ band 4)  Red • Red (ETM+ band 3)  Green • Green (ETM+ band 2)  Blue • Colors on image are shifted one band toward blue compared to real scene
  13. 13. Making a False-Color Image
  14. 14. Landsat 7 Facts • Altitude: 705 kilometers • Period: 98.9 minutes • Inclination: Sun-synchronous, 98.2 degrees • Equatorial crossing: Southbound 10:00AM +/- 15 min. • Repeat coverage interval: 16 days (233 orbits) • Swath width: 185 kilometers • On-board data storage: ~375 Gb (solid state)
  15. 15. See SPOT. See SPOT See • Satellite Pour l'Observation de la Terre • Sun-synchronous • Altitude: 832 kilometers, • Inclination: 98.7 • Revisit period: 26 days • Uses CCD’s and stare mode; no scanning
  16. 16. SPOT 5 Bands Band (microns) Colors Resolution 0.51 - 0.73 Panchromatic 2.5 & 5m 0.50 - 0.59 Green 10m 0.61 - 0.68 Red 10m 0.79 - 0.89 Near IR 10m 1.58 - 1.73 Mid IR 20m
  17. 17. SPOT Image of Kuwait City, 2004
  18. 18. IKONOS • 1992 Land Remote Sensing Policy Act permitted private companies to enter the satellite imaging business. • Lockheed Martin • Launched 2000 • 1 m resolution • Bands: Blue, Green, Red, Near IR • Now operated by GeoEye Inc., Dulles VA
  19. 19. Burj Khalifa by IKONOS
  20. 20. Terra • Part of NASA EOS (Earth Observation System) • Partnership of U.S., Canada, Japan • Instruments – ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) – CERES (Clouds and Earth's Radiant Energy System) – MISR (Multiangle Imaging Spectroradiometer) – MODIS (Moderate-Resolution Imaging Spectroradiometer) – MOPITT (Measurements of Pollution in the Troposphere)
  21. 21. ASTER • U.S. – Japan joint mission • Three Subsystems, each with own telescopes • VNIR: Four visible and near-IR channels, 15-m resolution • SWIR: Six short wave IR channels, 30-m resolution • TIR: Five Thermal IR Channels, 90-m resolution – IR sensors use Stirling Cycle coolers
  22. 22. MODIS • Resolutions 250, 500 and 1000 meters • Ten visible bands (250 and 500-m) • Ten Near IR bands (500 and 1000 m) • 16 Medium and Thermal IR bands (1000 m) • Bands are narrow and tailored to specific emissions and absorptions (ocean color, aerosols, ozone, water vapor, cloud temperature)

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