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Landsat

Landsat. Maa-57.2040 Kaukokartoituksen yleiskurssi Luento 2, syksy 2007. Chronology. 1965: NASA initiates an Earth Resources Survey (ERS) Program to develop methods for remote sensing of earth resources from space 1966: Several U.S. govenmental organizations start to participate 1967:

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Landsat

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  1. Landsat Maa-57.2040 Kaukokartoituksen yleiskurssi Luento 2, syksy 2007

  2. Chronology 1965: • NASA initiates an Earth Resources Survey (ERS) Program to develop methods for remote sensing of earth resources from space 1966: • Several U.S. govenmental organizations start to participate 1967: • Feasibility studies for an Earth Resources Technology Satellite (ERTS) 1968-69: • NASA airborne studies with multispectral scanners • ERTS design specifications • NASA approves contract with Hughes for ERTS Multispectral Scanner System (MSS)

  3. Chronology 1970: • Funds approved for an ERTS tracking facility • NASA selects GE as prime contractor for ERTS 1972: • 23.7.1972NASA launches ERTS 1 (Landsat 1) 1973-74: • over 100,000 images covering 75% of the earth's land surface 1975: • Name of the Program changed by NASA from ERTS to Landsat • 22.1.1975: NASA launches Landsat 2

  4. Chronology 1976: • Congress report recommends that NASA implement a training program for users of Landsat data 1977: • House of Representatives Committee on Science and Technology recommends a five year program to assure a more orderly management of earth resources activities. 1978: • Landsat 1 operations terminated • 5.3.1078: NASA launches Landsat 3

  5. Landsat 1 • 23.6.1972 - 6.1.1978 • It was the first Earth-observing satellite to be launched with the express intent to study and monitor our planet's landmasses. • The RBV was supposed to be the prime instrument, but the MSS data were found to be superior. • Data quantization: 6 bits

  6. Landsat 1 Orbit • Sun-synchronous, near-polar orbit at an altitude of 917 km • Inclination angle at 99.2° • Circled the earth every 103.34 minutes • Completed 14 orbits a day • Repeat cycle: 18 days • Swath width: 185 km • Equatorial crossing time: 9:30 a.m. +/- 15 minutes • Swath overlap (or sidelap) varied from 14 percent at the Equator to a maximum of approximately 85 percent at 81 degrees north or south latitude • WRS-1 path/row system

  7. Landsat 1 Return Beam Vidicon (RBV) • Operated from July 23, 1972 to August 5, 1972 recording only 1692 images • 80-meter resolution in the multispectral band • Three cameras that operate in the following spectral bands: • Band 1 Visible blue-green (475-575 nm) • Band 2 Visible orange-red (580-680 nm) • Band 3 Visible red to near-infrared (690-830 nm) • Data: 3.5 MHz FM video

  8. Landsat 1 Multispectral Scanner (MSS) • Four spectral bands: • Band 4 Visible green (0.5 to 0.6 µm) • Band 5 Visible red (0.6 to 0.7 µm) • Band 6 NIR (0.7 to 0.8 µm) • Band 7 NIR (0.8 to 1.1 µm) • Six detectors for each spectral band provided six scan lines on each active scan • Ground Sampling Interval (pixel size): 57 x 79 m • Image size: 185 x 185 km

  9. Landsat 2 • 22.1.1975 - 25.2.1982 • Orbit same as Landsat 1 • RBV same as in Landsat 1 • operated primarily for engineering evaluation purposes and only occasional RBV imagery was obtained, primarily for cartographic uses in remote areas • MSS same as in Landsat 1

  10. Landsat 3 • 5.3.1978 – 31.3.1983 • Orbit same as Landsat 1 • RBV: • two cameras, mounted side-by-side • panchromatic spectral response • higher spatial resolution (40 m) • swath of about 90 km (for a total swath of 180 km). • MSS: Band 8 Thermal (10.4 to 12.6 µm)

  11. Landsat MSS Inari, 20.7.1973, channels 5, 7, 4

  12. MSS • Landsat 1 MSS • Path 200, Row 17 • 22.5.1976 • R: 0.6 - 0.7 m • G: 0.8 - 1.1 m • B: 0.5 - 0.6 m

  13. Chronology 1979: • Presidential Directive • transfers Landsat operations from NASA to NOAA • recommends development of long term operational system with four additional satellites • recommends transition to private sector operation of Landsat 1981: • Reagan administration accelerates pace of Landsat commercialization • Landsat 2 operations terminated

  14. Chronology • 16.7.1982: NASA launches Landsat 4; Thematic Mapper era begins 1983: • Landsat 3 operations terminated • Proposal to commercialize land and weather satellites submitted to Congress 1984: • Government prohibited from privatizing the operational weather satellites, commercialization of land remote sensing satellites • 1.3.1984: NASA launches Landsat 5

  15. Landsat 4 • 16.7.1982 – standby 14.12.1993 - Decommissioned 15.6.2001 • Operational history: • built and launched by NASA, NOAA initially oversaw the operations of the satellite • EOSAT corporation in 1984 • 1998 management of the Landsat 4 and 5 operations contract was transferred from NOAA to the USGS • operations were continued by the private sector until mid-2001 when Space Imaging (formerly EOSAT) returned the operations contract to the U.S. Government • Quantisation: 8 bit (256 levels) • Scene Size: 184 x 185.2 km

  16. Landsat 4 Orbit • Circular, sun-synchronous, near-polar orbit at an altitude of 705 km • Inclined at 98.2° • Circled the Earth every 99 minutes • Repeat cycle: 16 days • Equatorial crossing time: 9:45 a.m. +/- 15 minutes • Swath width: 185 km • WRS-2 path/row system

  17. Landsat 4 Multispectral Scanner (MSS) • Four spectral bands (identical to L1 and L2) • Band 4 Visible (0.5 to 0.6 µm) • Band 5 Visible (0.6 to 0.7 µm) • Band 6 Near Infrared (NIR) (0.7 to 0.8 µm) • Band 7 NIR (0.8 to 1.1 µm) • Six detectors for each reflective band provided six scan lines on each active scan • Ground Sampling Interval (pixel size): 57 x 79 m

  18. Landsat 4 Thematic Mapper • Added the mid-range infrared to the data • Seven spectral bands, including a thermal band: • Band 1 Visible (0.45 – 0.52µm) 30m • Band 2 Visible (0.52 – 0.60µm) 30m • Band 3 Visible (0.63 – 0.69µm) 30m • Band 4 NIR (0.76 – 0.90µm) 30m • Band 5 NIR (1.55 – 1.75µm) 30m • Band 6 Thermal (10.40 – 12.50µm) 120m • Band 7 Mid IR (2.08 – 2.35µm) 30m • Ground Sampling Interval (pixel size): 30m reflective, 120m thermal

  19. Landsat 5 • 1.3.1984 – Present • MSS instrument was turned off in August of 1995. • TM instrument is still in operation • Orbit as Landsat 4 • MSS and TM as in Landsat 4

  20. Visible channels: 1: Blue, 2: Green, 3: Red Infrared channels: 4: NIR1, 5: NIR2, 7: MIR Landsat TM-image: channels

  21. True color 321, False color 432… …and false color 745 Landsat TM-image: color combinations

  22. Landsat TM • Landsat-5 Thematic Mapper • Etna, Italia, image acquisition 3.6.1995 • Channel combinations 321 ja 453

  23. MSS vs. TM Landsat MSS 14.9.1972 Landsat TM 1.9.1990

  24. Chronology 1985: • Earth Observation satellite Company (EOSAT), a partnership of Hughes and RCA, selected by NOAA to operate the Landsat system under a ten year contract. EOSAT: • operates Landsats 4 and 5 • will build two new spacecraft (Landsats 6 and 7) • has exclusive rights to market Landsat data collected prior to date of contract (9/27/85) until expiration date (7/16/94) • has exclusive right to market data collected after 9/27/85 for ten years from date of acquisition. • will receive all foreign ground station fees. • USG to provide $250M for spacecraft development over five years.

  25. Chronology 1986: • Administration recommends limiting government funding to $125M • EOSAT and NOAA argue about the platform of future Landsat 1987: • NOAA submits new plan for Landsat, congress reluctantly accepts 1988: • EOSAT contract with NOAA re-negotiated to conform to changes in commercialization program. • Funding for Landsat 6 released by Congress • NOAA does not request operating funds for Landsat in FY89 because Landsats 4 and 5 are past design life • Congress adds funding to cover operations for half the fiscal year.

  26. Chronology 1989: • NOAA: funds for Landsat operations are spent and directs EOSAT to turn off the satellites • Interim funding plan to keep Landsat operating through the end of fiscal year • President approves policy statement committing the US to continuity of Landsat-type data 1990: • NOAA does not request operating funds for Landsat • Congress appropriates enough funds to keep the system operational for six months and requests agencies that use Landsat data give funds to keep system going for the remainder of the year 1991: • Funding problems and solutions from 1990 repeated in 1991, administration fails to develop a policy toward Landsat

  27. Chronology • 1992: • Land Remote Sensing Policy Act of 1992 recognizes that commercialization of Landsat has not worked and is not likely to work in the future. • Landsat Program Management (NASA, DoD etc.): • establish a management plan • develop a Landsat Advisory Process and report on progress at established intervals • procure Landsat 7 • begin negotiations with contractor on data policy for Landsats 4-6 • assume Landsat 6 program responsibilities from DOC. • develop a data policy for Landsat 7 on the basis of "cost of fulfilling user request" • conduct a technology demonstration program • assess options for a successor land remote sensing system

  28. Chronology 1993: • Funding difficulties continue • 5.10.1993: Landsat 6 launched from Vandenberg Air Force Base, satellite fails to obtain orbit 1994: • National Science and Technology Council: continuation of the Landsat Program with the completion of the ETM+ instrument and the Landsat 7 spacecraft. NASA and NOAA are instructed to develop a management plan to implement the recommendation. • Landsat Program Management and EOSAT agree to terms for continued operation of Landsats 4 and 5 and a data distribution and pricing schedule, later DoC and EOSAT start to fight about funding

  29. Landsat 6 • 5.10.1993, lost on launch Enhanced Thematic Mapper (ETM) • Eight spectral bands, including a pan and thermal band • Band 1 Visible (0.45 – 0.52µm) 30m • Band 2 Visible (0.52 – 0.60µm) 30m • Band 3 Visible (0.63 – 0.69µm) 30m • Band 4 Near Infrared (NIR) (0.76 – 0.90µm) 30m • Band 5 NIR (1.55 – 1.75µm) 30m • Band 6 Thermal (10.40 – 12.50µm) 120 m • Band 7 Mid IR (2.08 – 2.35µm) 30m • Band 8 Panchromatic (PAN) (0.52 - 0.90µm (15m)

  30. Chronology • "Management Plan for the Landsat Program," a document describing the program objectives and agency responsibilities is signed by representatives of NASA, NOAA and the US Geological Survey. 1995: • EOSAT wins lawsuit 1996: • Landsat 7 planning well underway 1997: • Data policy, data pricing policy and the status of the ground system for support of Landsat 7 data acquisition, processing and distribution announced 1999: • 15.4.1999 Landsat 7 launched successfully

  31. Landsat 7 • Mission: repetitive acquisition of high resolution multispectral data of the Earth's surface on a global basis • Features: • Data Continuity: latest in a continuous series of land remote sensing satellites spanning 32 years • Global Survey Mission: systematically build and refresh a global archive of sun-lit, cloud-free images • Affordable Data Products: cost of fulfilling user requests • Enhanced Calibration: better than 5% absolute • Responsive Delivery: within 48 hours of order • Landsat 7 is part of a global research program known as NASA's Earth Sciences Enterprise, a long-term program that is studying changes in Earth's global environment.

  32. Landsat 7 • Launch date: 15.4.1999 Spacecraft • Power: single Sun-tracking solar array and two 50 AHr, NiCd batteries • Attitude control: four reaction wheels (pitch, yaw, roll, and skew), three 2-channel gyros with celestial drift updating, a static Earth sensor, a 1750 processor, and torque rods and magnetometers for momentum uploading • Orbit control and backup momentum unloading provided through a blow-down monopropellant hydrazine system with a single tank containing 270 pounds of hydrazine, associated plumbing, and twelve 1-pound-thrust jets. • Weight: approx. 4,800 lbs (2200 kg) • Length: 14 ft (4.3 m) • Diameter: 9 ft (2.8 m)

  33. Landsat 7

  34. Landsat 7 Orbit • Sun-synchronous orbit at an altitude of 705 km • 233 orbit cycle every 16 days covers the complete globe (except for the highest polar latitudes) • Inclination angle 98.2° • Circles the Earth every 98.9 minutes • Repeat cycle: 16 days • Equatorial crossing time: 10:00 a.m. +/- 15 minutes • Each scene is 185 km wide × 170 km high • WRS-2 path/row system

  35. Landsat 7 Enhanced Thematic Mapper Plus (ETM+) • Eight spectral bands, including a pan and thermal band: • Band 1 Visible (0.45 – 0.52µm) 30m • Band 2 Visible (0.52 – 0.60µm) 30m • Band 3 Visible (0.63 – 0.69µm) 30m • Band 4 Near Infrared (NIR) (0.76 – 0.90µm) 30m • Band 5 NIR (1.55 – 1.75µm) 30m • Band 6 Thermal (10.40 – 12.50µm) 60 m Low Gain / High Gain • Band 7 Mid IR (2.08 – 2.35µm) 30m • Band 8 Panchromatic (PAN) (0.52 - 0.90µm (15m) • Added the Band 6 Low and High gain 60 meter thermal bands • On-board calibration: Full Aperture Solar Calibrator, Partial Aperture Solar Calibrator, 2 Calibration Lamps

  36. Landsat 7 Channel spectral responses

  37. TIR: example • Landsat ETM, 4.7.2001, left channels 743, right 6

  38. Landsat 7 ETM+ band purposes: • Blue-green: Bathymetric mapping, distinguishes soil from vegetation, deciduous from coniferous vegetation • Green: Emphasizes peak vegetation, which is useful for assessing plant vigor • Red: Emphasizes vegetation slopes • Reflected IR: Emphasizes biomass content and shorelines • Reflected IR: Discriminates moisture content of soil and vegetation, penetrates thin clouds • Thermal IR: Useful for thermal mapping andestimate soil moisture • Reflected IR: Useful for mapping hydrothermally altered rocks associated with mineral deposits • Panchromatic: 15 m res., e.g. “sharpening” of multispectral images

  39. Landsat 7 • ETM+ instrument cutaway and optical path Detectors: channels 1-4, 8: silicon, 5 and 7: indium antimonide 6: mercury cadmium tellurid

  40. Landsat 7 Ground System • Mission Operations Center (MOC): NASA Goddard Space Flight Center, all space vehicle operations • Landsat Ground Station (LGS): EDC (Sioux Falls, SD), main receive site for wideband X-Band downlinks of payload data • Landsat Processing System (LPS): EDC records all wideband data and spatially reformats Earth imagery and calibration data into Level 0R data • Image Assessment System (IAS): EDC, is responsible for the off-line assessment of image quality • Level 1 Product Generation System (LPGS): EDC, generates Level 1 products • EROS Data Center Distributed Active Archive Center (LP-DAAC): information management, user interface, data archival and distribution functions • International ground stations (IGS)

  41. Landsat 7

  42. Landsat 7 Worldwide Reference System WRS • Global grid system comprising 233 paths by 248 rows

  43. Landsat 7

  44. Landsat 7 image products Level 0R • Raw data needing radiometric and geometric correction • Data contains more than 20 files • Image data: 9 channels (thermal channel with 2 different settings) • Internal calibrator data (measurements of calibration lamps), Mirror Scan Correction Data (how smoothly mirror is rotating), Payload Correction Data (attitude and position of satellite), Scan line offsets (start and end positions of scan lines) • Metadata about images (date, cloudiness), geolocation index (corner coordinates), calibration parameters

  45. Landsat 7 image products Level 1R • Basic radiometric correction has been made • Image errors like striping or pixel shifts due to scanning system have been removed • Pixel values have been transformed to absolute radiances measured by instrument using calibration data and stored to 32-bit real numbers • Real numbers have been multiplied with 100 and saved as 16-bit integer numbers • These are scaled to 8-bit integer numbers and scaling parameters are saved so that 8-bit numers can be transformed to radiances

  46. Landsat 7 image products Level 1G • Basic radiometric and geometric correction • Geometric effects of instrument (scanning system, incidence angle), satellite (variations in attitude and height) and target (curvature and spinning of Earth) have been removed • Map projections: Universal Transverse Mercator, Lambert Conformal Conic, Transverse Mercator, Polyconic, Oblique Mercator, Polar Stereographic, Space Oblique Mercator • Positioning of image is based on orbital parameters

  47. Landsat 7 image products • Level 0R ja 1G

  48. Landsat 7 Conversion to Radiance • DN's in a 1G product back to radiance units: Lλ = "gain" * QCAL + "offset" • which is also expressed as: Lλ = ((LMAXλ - LMINλ)/(QCALMAX-QCALMIN)) * (QCAL-QCALMIN) + LMINλ where: • Lλ = Spectral Radiance at the sensor's aperture in watts/(meter squared * ster * μm) • gain and offset= from Level 1 product header or ancillary data record • QCAL = the quantized calibrated pixel value in DN • LMINλ = the spectral radiance that is scaled to QCALMIN in watts/(meter squared * ster * μm) • LMAXλ = the spectral radiance that is scaled to QCALMAX in watts/(meter squared * ster * μm) • QCALMIN = the minimum quantized calibrated pixel value (corresponding to LMINλ) in DN, 1 (LPGS Products) / 0 (NLAPS Products) • QCALMAX = the maximum quantized calibrated pixel value (corresponding to LMAXλ) in DN = 255

  49. Landsat 7 System Performance • Absolute Geodetic Accuracy • Geometrically corrected products shall be accurate to 250 meters (1 sigma), excluding terrain effects, without ground control. • Limited by spacecraft/instrument geometric model accuracy (e.g., ephemeris, attitude, alignment knowledge). • Currently post-calibration geodetic accuracy of systematic ETM+ products is approximately 80 meters • Band-to-Band Registration • Geometrically corrected products shall have the multispectral bands registered to 0.17 pixels (1 sigma) • Limited by focal plane alignment and stability • Currently 0.08-0.10 pixels • Image-to-Image Registration • Geometrically corrected images from multiple dates shall be capable of being registered to an accuracy of 7.3 meters (1 sigma) • Limited by high frequency distortions within images (e.g., uncompensated attitude jitter, scan mirror instability) • Currently within specification

  50. Scan Line Corrector (SLC) • Compensates for the along track motion of the spacecraft that occurs during an active cross track scan • Rectilinear scan pattern is produced using the SLC instead of the zig-zag pattern that would be produced without it • Two parallel nickel-plated beryllium mirrors set at an angle on a shaft that rotates

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