About Rapid Response Imagery
The Rapid Response system was developed to provide near realtime imagery from the MODIS instrument for users who require an immediate view of a specific phenomenon from satellites.
All the images that appear on our site are in the public domain and can be freely used and reproduced for any purpose. Please credit: “NASA/GSFC, Rapid Response.” If publishing online, please link Rapid Response. For more information on use and credit, contact the Rapid Response Outreach Coordinator.
The Rapid Response system receives MODIS Level-0 data from a special near real time data feed. These data are processed to Level 1B using the MODISL1DB code from the Ocean Color / SeaDAS group, which is similar but not identical to the code used to process the science quality data.
The calibration look-up-tables for the Level 0 to Level 1B processing are updated regularly when they are received from the MODIS Calibration and Support Team.
The geolocation for the Terra satellite uses the same entrained data as used by the standard processing. For Aqua, Rapid Response uses predicted satellite ephemeris rather than the definitive ephemeris. Normally, the differences in location are relatively small, under 400m and often under 100m.
Rapid Response true and false color images are created using the “corrected reflectance” algorithm developed by Jacques Descloitres at NASA/GSFC. The purpose of this algorithm is to provide natural looking images by removing gross atmospheric effects, such as Rayleigh scattering, from MODIS visible bands 1-7. In particular, the algorithm produces quasi-true-color images from MODIS bands 1, 3, and 4. In contrast, the MODIS land surface reflectance product (MOD09) is a more complete atmospheric correction algorithm that includes aerosol correction, and is designed to derive land surface properties. In clear atmospheric conditions the corrected reflectance product is very similar to the MOD09 product, but they depart from each other in presence of aerosols, which are present in the corrected reflectance product, but not in the land surface reflectance product.
The fire detection code is identical to that used to process the science quality data. However, there will be differences in the locations of the fires detected due to the geolocation differences mentioned above. For more information on the fire data, see the MODIS Collection 5 Active Fire Product User’s Guide. For more information on the algorithm, see Giglio, L., J. Descloitres, C. O. Justice, and Y. J. Kaufman. 2003. An enhanced contextual fire detection algorithm for MODIS. Remote Sensing of Environment, 87:273-282.
The land surface temperature code is adapted from the science code by substituting climatological averages for much of the ancillary data. For details, see Pinheiro, A., J. Descloitres, J. Privette, J. Susskind, L. Iredell, and J. Schmaltz. 2007. Near-real time retrievals of land surface temperature within the MODIS Rapid Response System. Remote Sensing of Environment, 106:326-336.
