A sun photometer was installed at the Sevilleta Field Station in 1994.It is part of a network of such instruments deployed around the world within a program called AERONET (AErosol RObotic NETwork http://aeronet.gsfc.nasa.gov/new_web/system_descriptions.html) established by NASA to obtain a measure of atmospheric aerosols around the globe. Individual photometer units are designed to view the sun and sky at preprogrammed intervals throughout the day for the measurement of aerosol optical thickness, water vapor amounts, ozone levels, particle size distribution, aerosol scattering, phase function, and single scattering albedo. These measurements can also be used to radiometrically correct satellite imagery. The unit consists of A) the photometer, B) a robot for directing the photometer at the sun, C) a CIMEL datalogger which directs the data collection and storage, D) a DCP (Data Collection Platform) which controls hourly data transmission to the GOES satellite and E) an antenna for facilitating this DCP to satellite link. Solar measurements are made at 1021, 871, 669, 498, 437, 379, and 339 nm. The Sevilleta LTER is responsible for maintenance of the unit on site while NASA takes care of data processing and and storage and annual re-calibration of the unit. Data can be obtained from NASA via:http://aeronet.gsfc.nasa.gov/cgi-bin/type_piece_of_map_opera_v2_new.