ICESAT Satellite - NASA/Goddard Space Flight Center
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
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 | lectivity 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
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 DistributedSurface 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
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:
- 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
| 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 |
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
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:
- 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
| Vertical Accuracy (m) | Surface Slope (degrees) | Surface Roughness (m) |
|---|---|---|
| 1 | 10 | unspecified |
| .5 | 3 | 1 |
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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SCIENCE
ICESAT Fact:
The ICESAT mission and the GLAS Instrument completed taking over 1.9 billion measurements while in orbit with the completion of its 2009 spring campaign.
