The Geophysical Institute's High Resolution Picture Transmission (HRPT) project operates a automated satellite-receiving station that receives, processes, archives, and distributes image data from polar-orbiting satellites which broadcast data from medium-resolution earth sensors.

The receiving-station is of the automated HRPT type and currently receives visible and infrared images from AVHRR sensors on two NOAA weather satellites, currently NOAA-12 and NOAA-14. The HRPT acronym refers to the particular kind of L-band telemetry downlink and modulation schemes used by the NOAA weather satellites to transmit images to inexpensive ground stations. NOAA's Advanced Very High Resolution Radiometer (AVHRR) sensor covers very large regions of the earth with high spatial-resolution (about 1-km) relative to the area covered (hundreds of thousands of sq-km).

The NOAA sensors provide data from five wavelength bands:
Ch 1	Visual
Ch 2	Near-Infrared
Ch 3	Mid-infrared
Ch 4	Thermal-infrared 1
Ch 5	Thermal-infrared 2

The HRPT station provides on-line access to browse images, in the gif format, of band 2 (near-infrared), sub-sampled by 32 to generate images containing approximately 900 pixels by 900 lines. This subsampling reduces spatial resolution to 32-km, but minimizes transmission time and keeps image files of manageable length.

The directly-acquired digital AVHRR data are subsampled and routinely composited into regional mosaics showing synoptic coverage from the Russian Far East into western Canada/Greenland and the U.S., and from 40 degrees North to 90 degrees North latitude. The displays are updated hourly, using unique techniques developed by colleagues at the Institute of Marine Science. The regional coverage is available from ftp://gis.lter.alaska.edu/LoRes_Archive/ with the filename "daily.composite.gif" and can be downloaded via ftp or this WWW link.

Digital images of band 2 and band 4 (thermal infrared) subsampled only by two (2-km spatial resolution) also are provided on-line to users with interests in the Alaskan environment. University researchers and students routinely use these images to address dynamically-changing natural events, monitoring key Alaskan resources, and for instructional purposes in college-level courses. Government, other universities, industry, and foreign users also regularly download our data. These higher-resolution images, also in the gif format, are available on-line at "ftp://gis.lter.alaska.edu/HiRes_Current/". Radiometric data at full-resolution from all bands are also available by special arrangement at moderate cost.

This project was sponsored in part by the Natural Resources Fund, University of Alaska, and Geophysical Institute and cost sharing by major users of the image data. Its scientific personnel include J.M.Miller, K.G.Dean, K.Engle, and S.George.

For more information on AVHRR data, or to express support and possible cost-sharing, please contact John Miller at jmiller@gi.alaska.edu or 907-474-7363.