This product grew out of the AVHRR Polar Pathfinder (APP) project, lead by Chuck Fowler and Jim Maslanik at the University of Colorado. The programs used for AVHRR calibration and navigation were developed by Dan Baldwin, also at the University of Colorado. AVHRR GAC data are being provided by the NOAA Satellite Active Archive (SAA). The algorithms used in the retrieval of surface, cloud, and radiation parameters were developed under support from NASA, particularly the POLES project. Xuanji Wang has contributed much time and effort in testing and using CASPR with APP data. Continued support is provided by the Office of Research and Applications (ORA), NOAA/NESDIS. Thanks to Bill Bellon for suggesting this product and for work on the web page.