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Science: ICESat Science Requirements

Science: ICESat Science Requirements

ICESat Science Requirements:


Characteristics of Surface Properties:

Provide Measurements of Apparent Surface Reflectivity:

  • Provide Global Surface Coverage
  • Spatial Grid Resolution Unspecified
  • Measure Apparent Surface Reflectivity to:
Surface Type Reflectivity Accuracy (%) Averaging Time (sec)
Land 10 1
Snow 5 1
  • Expect Up to TBD% Loss of Maximum Achievable Quantityof Reflectivity Data (due to principally):
    • cloud cover
  • Repeat Mapping Unspecified
  • Provide Intermediate and Finished Reflectivity DataProducts to The MTPE Archive Within TBD Months After Formation
  • Input Data Products Needed Within TBD Days After TheirCreation

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Characteristics of Vegetative Canopy Measurements:

Provide Profiles of Vegetative Canopies:

  • Profiles are Referenced Relative to Local SurfaceElevation:
    • Local Surface Elevation is Referenced Relative to Geocenter
    • Geocenter is Defined Relative to IERS Terrestrial Reference Frame (ITRF)
    • Vertical Resolution Unspecified
    • Spatial Resolution Unspecified
  • Provide Aerial Coverage Over Globally Distributed Surface Vegetation
  • No Specific Seasonal Repeat Conditions
  • Provide Intermediate and Finished Data Products toThe MTPE Archive Within TBD Months After Formation
  • Input Data Products Needed for Formation of VegetativeCanopy Profiles Within TBD Days After Their Creation

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Characteristics of Aerosol/Atmospheric Measurements:

Provide Profiles of Cloud and Aerosol Structures:

  • Profiles are Referenced Relative to Sea-Level:
    • Sea Level is Defined Relative to TBD (mean relative to geocenter)
    • Measurement Extends from Sea Level up to 40 Km. Radial Altitude
  • Provide Aerial Coverage Over Globally Distributed Clouds & Aerosols
  • Sample Individual Cloud Top and/or Aerosol Layer Heights:
    • when Upper Boundary is "Sharp" (less than 100 m)
    • and Backscatter Cross-Section is at least .001 per meter per steradian
    • with 75 meter (1 sigma) Vertical Resolution
  • Sample Vertical Tropospheric Cloud & Aerosol Structures:
Vertical Resolution (m) Horizontal Resolution (m) Relative Accuracy (%) Backscatter Cross Section(1/m-sr)
75 200 5 10-4
300 10 10 10-4 - 10-6
300 50 20 10-6 - 10-8
  • Desire Orbit Optimization to Provide Occasional NadirCoincidences with MODIS (either AM-1 or PM-1):
    • Provides Calibration of Altimetry Atmospheric Correction
    • Coordinates MODIS Atmospheric Data with ICESat Cloud Profiles (Structures)
  • Lateral Resolution/Track Density Unspecified
  • No Specific Seasonal Repeat Conditions
  • Provide Intermediate and Finished Data Products toThe MTPE Archive Within TBD Months After Formation
  • Input Data Products Needed for Formation of CloudProfile Within TBD Days After Their Creation

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Characteristics of Ice Sheet Topographical Map: Provide a Topographical Map of The Global Ice Sheets:

  • Map is Referenced in Geocentric Coordinates, DefinedRelative to IERS Terrestrial Reference Frame (ITRF)
  • Provide 96% Areal Coverage of:
    • Arctic Ice Cap & Sea Ice
    • Antarctic Ice Cap & Sea Ice
    • Greenland Ice Sheet & Sea Ice
  • Utilize the Cross-Over Analysis Technique for Ice Data:
    • Provide Spatial Grid Resolution of Less Than 10 Km. in Any Direction
    • Assume Averaging "Box" of 200 Km. Square for any Given DataSet Reduction (Worst Case Elevation Error Tolerance Conditions)
    • Maximize Angle Between Cross Over Tracks Up to 90 degrees Maximum
    • Provide Post-Facto Mean Elevation Error of 1 cm. or Less
    • Be Able to Measure Localized Regional (10000 sq. Km.) Topographiesto as Small a Spatial Grid Resolution as 1 Km. Square After Accumulationof 5 Years of Data Within That Region
  • Accommodate Surface Feature Average Slope Change, orequivalent roughness, of 3 degrees or Less, Over Any Sensor Footprint:
    • Elevation Error of Single Measurement is 15 cm. (From 1 degree or LessFeature Slope Regions)
    • Elevation Error of Single Measurement is 22 cm. (From 1-3 degree FeatureSlope Regions)
    • Elevation Data From Features with Surface Slopes Greater Than 3 degreesis to be Provided with Resulting System Accuracy Acceptable
    • Sample Ice Sheet Surface Elevation having Wavelengths of 500 m. orGreater
  • Expect Up to 50% Loss of Maximum Achievable Quantityof Ice Data (due to principally):
    • cloud cover
    • feature slopes
  • Repeat Entire Mapping on a Time Scale no Longer Than182 Days:
    • Repeat Registration of Map Tracks/Grid to Within 1 Km. or Less of InitialMap (Reference for Entire Data Set)
  • Provide Intermediate and Finished Map Data Productsto The MTPE Archive Within TBD Months After Formation
  • Input Data Products Needed for Formation of Ice MapWithin 7 Days After Their Creation

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Characteristics of Land Topographical Map:

Provide a Topographical Map of The Land Surface:

  • Map is Referenced in Geocentric Coordinates, DefinedRelative to IERS Terrestrial Reference Frame (ITRF)
  • Provide Global Land Surface Coverage
  • Spatial Grid Resolution Unspecified
  • Accommodate Surface Feature (Along Track) ElevationStep Changes of up to 3 Km.
  • Measure Height of Land Surface Topography to:
Vertical Accuracy (m) Surface Slope (degrees) Surface Roughness (m)
1 10 unspecified
.5 3 1
  • Expect Up to tbd% Loss of Maximum Achievable Quantityof Land Data (due to principally):
    • cloud cover
    • feature slopes
  • Repeat Mapping Unspecified
  • Provide Intermediate and Finished Map Data Productsto The MTPE Archive Within TBD Months After Formation
  • Input Data Products Needed for Formation of Land MapWithin TBD Days After Their Creation

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Characteristics of Ocean Topographical Map:

Provide a Topographical Map of The Global Oceans:

  • Map is Referenced in Geocentric Coordinates:
    • Geocenter is Defined Relative to IERS Terrestrial Reference Frame(ITRF)
    • Elevation and Spatial Resolution Unspecified
  • Provide Global Ocean Coverage
  • Expect Up to TBD% Loss of Maximum Achievable Quantityof Ocean Data (due to principally):
    • cloud cover
  • Repeat Mapping Unspecified
  • Provide Intermediate and Finished Map Data Productsto The MTPE Archive Within TBD Months After Formation
  • Input Data Products Needed for Formation of OceanMap Within TBD Days After Their Creation

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