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Arctic & Antarctic Research Center (AARC) AVHRR and HRPT Direct Readout Radiance Data from McMurdo and Palmer Stations, Antarctica

AVHRR HRPT level 0 raw telemetry data are acquired at the Arctic and Antarctic Research Center (AARC) on selective passes by satellite receivers located at McMurdo Station, Antarctica (77 degrees, 51 minutes S, 166 degrees, 40 minutes E.) and Palmer Station, Antarctic Peninsula (64 degrees, 46 minutes S, 64 degrees, 4 minutes W.) Generally, most of the Antarctic continent and its coastline are covered daily. Swaths are 2250 kilometers long and generally start or end over the extreme South Pacific Ocean adjacent to the Ross Sea. Data collection from Palmer Station covers the land areas of West Antarctica, Southern South America, the South Atlantic including the Falkland Islands and the South Orkney Islands, and the Drake Passage and portions of the South Pacific Ocean. Continuous data collection at the McMurdo Station began on 26 October 1987. Data are also archived for 30 October 1985 - 2 December 1985 and for 30 October 1986 - 30 January 1987. Continuous data collection began at the Palmer Station 3 August 1989. The data resolution is 1100 meters at subtrack, 4000 - 6000 meters at limb; 360 scans per minute. Satellite revisit time is twice daily, however, due to the proximity to the South Pole, 14 passes a day are received at McMurdo and 10 passes a day are received at Palmer from each spacecraft. Data are acquired, archived, processed for requesters, and distributed by the Arctic & Antarctic Research Center (AARC). Processing of the raw data will depend on the requirements of the requester, but a typical sequence might be as follows: + Reformat raw data for extraction; up to 10 missing scan lines can be interpolated by the software. + Calibrate the reformatted data to convert from brightness values to temperature values. + Apply the moisture/atmospheric correction. + Register selected data to the user-specified grid. + Transfer to user-specified medium. Some examples are tape, diskette, photographic product, or file format for electronic transfer. About 95 percent of the presently archived data have been cataloged on our online directory. Data dropouts, caused by transmission interference due to solar flare activity, occur in some images; the processing software can smooth the data if fewer than 10 scan lines are missing. All archived images contain usable data. Processed data are binary byte arrays of user-defined size. Full spacecraft attitude correction and earth correction routines are applied to the raw data to create the products. Orbital elements, equator crossings, altitude and period of the spacecraft are generated for the raw data using the AARC scientific workstation. Data products can be gridded to a user-specified grid. Data are also available in raw form (10 bits of information stored in a 16 bit word) on 4mm DDS2 or DDS3 DAT cassettes or DLT7000 tapes. Users would need access to an 4mm DAT or DLT7000 reader. An alternative method to access the digital archive is to use the Sun Workstations located at the AARC, Scripps Institution of Oceanography. AARC personnel can be contacted for access information.

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