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Science: ICESat Science Requirements

Science: ICESat Science Requirements

ICESat Science Requirements:

• Surface Characteristic Measurments
• Ice Sheet Topographical Mapping
• Vegetative Canopy Profile
• Global Land Topographical Mapping
• Aerosol/Atmospheric Profile
• Ocean Surface Topographical Mapping

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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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