3Why: The earth systems are in constant motion. Long term daily observation of the entire earth which can be used to establish baselines, from which it is possible detect and measure regional to global scale environmental changes.
4How:Imaging sensors on polar orbiting satellites provide consistent sun-synchronous observation of the earth at a spatial and spectral resolution suitable for observing:Clouds and aerosols.Snow and ice.Ocean color and temperature.Land surface, vegetation and fire.
5Disadvantages of Geostationary Satellite Data: Orbits at 35,000 km make it difficult to acquire sub-kilometer resolution imagery.Global constellation with spectral bands suitable for air, land, sea and ice observations has not been achieved.No polar coverage.
7A Long Term Record Of Daily Global Observations of the Earth: AVHRR – Advanced Very High Resolution Radiometer flown on NOAA’s Polar Orbiting Environmental Satellites from 1978 to the present.MODIS – MODerate resolution imaging spectrometer flown on NASA Earth Observing System (Terra and Aqua satellites since December 1999.VIIRS – Visible Infrared Imaging Radiometer Suite – to be flown on the NOAA-NASA-DOD National Polar Orbiting Environmental Satellite System (NPOESS) with first launch expected in
8Science Driven Improvements From AVHRR - Spectral Resolution Five BandsVis, NIR,MIR, andtwo TIRMODIS36 BandsVIIRS20 Bands“The best ofthe MODISBands.”
9Science Driven Improvements From AVHRR – Spatial Resolution Four kmGACOne kmLAC &HRPTMODISInternestedBands at 250 m500 mAnd 1 kmVIIRS15 bands at800 mFive bandsAt 400 m
10Science Driven Improvements From AVHRR – Geolocation Accuracy Variable.GCP’sFrequentlyUtilized.MODISSub-Kilometer.VIIRSSub-Kilometer.
19SummaryNASA and NOAA have built a long record of daily global observations of the earth.The NASA-MODIS instrument provides data that are substantially better than the NOAA-AVHRR.The VIIRS instruments will continue MODIS style observations into the next decade and beyond.Establishing and operating new archives for MODIS and VIIRS for global environmental change research would require a very large effort in data transfer, data storage, and data processing.