The following terms and acronyms are used in descriptions of meteorological satellite systems, instruments, data, or their display via the Internet.

AMSU - Advanced Microwave Sounder Unit. Microwave instrument onboard the NOAA-15 through NOAA-19 amd European METOP spacecraft. The AMSU-A instrument consists of fifteen channels from 23.8 to 89.0 GHz with a subpoint resolution of 48 km. The AMSU-B is a five channel instrument from 89.0 to 183.0 GHz with a subpoint resolution of 16 km.

APT - Automatic Picture Transmission. Mode of transmitting images from the NOAA AVHRR. Provides low resolution (4 km) Infrared (IR) and Visible data.

ASOS - Automated Surface Observing System. A network of automatic weather observation stations operated by the U.S. National Weather Service or Dept. of Defense.

AVHRR - Advanced Very High Resolution Radiometer. Imaging instrument onboard the NOAA polar orbiting satellites. Produces infrared (IR) and visible images with a sub-point resolution of 1 km at the earth's surface.

CONUS - CONtinental United States.

DMSP - Defense Meteorological Satellite Program. A series of low altitude (550km), polar orbiting satellites operated by the Department of Defense. Provides high resolution (0.5 km) visible and IR, plus passive microwave imagery (25-40 km). Data is made available via the Shared Processing Network and archived at the National Geophysical Data Center, Boulder, CO.

ENVISAT - Polar orbiting spacecraft operated by the European Space Agency possessing several instruments used to monitor the earth's environment. Parameters measured include ozone concentration, aerosols, surface stress for earthquake potential, sea level heights, and fires.

EUMETSAT - European Organisation for the Exploitation of Meteorological Satellites. Delivers weather and climate-related satellite data, images and products 24 hours a day, 365 days a year to meteorological agencies of member states.

GIF - Graphical Information Format. Common image format used on the Internet. Developed by Compuserve. Main advantage is that GIF images occupy relatively little file space.

GMS - (Himiwari) geostationary satellite operated by the Japanese Meteorological Agency. Views the western Pacific Ocean, eastern Asia, the Indian Ocean, and Australia and New Zealand. Provides images in visible and three IR channels at resolutions of 2.5 km and 5 km, respectively.

GOMS - Geostationary Operational Meteorological Satellite. The first GOMS was launched by the Russian government on October 31, 1994 and has not provided images since 1998. GOMS is located above the Indian Ocean on the Equator at 76 degrees East. To date, no new GOMS spacecraft have been placed in orbit.

GOES - Geostationary Operational Environmental Satellite. A U.S. satellites operated by NOAA. Positioned in a nearly stationary orbit over the Equator at an altitude of about 22,500 miles. GOES-12 is currently the operational east spacecraft at 75 degrees West, while GOES-11 is the west spacecraft located at 135 degrees West. GOES-10 is situated at 60W and is providing images of South America.

GPS - Global Positioning System. Constellation of polar-orbiting satellites that provides accurate earth position data for commerce. Refraction (occultaion) of the GPS radio signals caused by atmospheric density and moisture can be used to derive Total Precipitable Water for weather forecast applications.

HRPT - High Resolution Picture Transmission. High resolution imaging mode from the AVHRR on the NOAA satellites. Data is produced in five channels with a resolution of 1km at the satellite subpoint (nadir).

INDOEX - Indian Ocean Experiment. Images (Visible, IR, Water Vapor) obtained from a METEOSAT spacecraft centered over the Indian Ocean.

INSAT - Indian Satellite operated by Indian Space Agency. This geostationary satellite is located at 74 degrees East, providing three-hourly visible and infrared coverage of Asia, east Africa, and the Indian Ocean region.

IR - Infrared. Type of satellite image that shows earth-emitted radiance in various wavelengths, usually near 4, 6-7, and 10-12 micrometers. Advantage of IR is that it can be used to monitor weather and oceanographic conditions 24 hours a day.

JPEG - Joint Photographic Expert Group. Image format that uses data compression techniques to reduce the size of the image file. Supports 8 or 24 bits-per-pixel.

LAC - Local Area Coverage. High resolution (1km) image data from AVHRR that is obtained over remote areas, saved via onboard data recorder, then later transmitted to a ground station.

LI - Lifted Index. Difference in temperature between an air parcel lifted adiabatically from the surface to 500 mb (about 18,000ft) and the environmental temperature at that level. A product that can be derived from GOES imager or sounder data, as well as radiosonde or numerical model data.

METEOSAT - Series of geostationary satellites operated by the European Space Agency. Meteosat Second Generation (MSG) now provides imagery in visible, plus eleven IR bands, including longwave IR (10.5 micrometer) and water vapor (6.5 micrometer) channels at 2.5 km resolution. Centered near Greenwich meridian (0 deg Longitude). METEOSAT is also providing images of the Indian subcontinent at 63 deg East (referred to as INDOEX).

METOP - Series of low earth orbit spacacraft developed by EUMETSAT that will provide observations using heritage instruments from the NOAA series such as AVHRR. The first METOP (-A) was launched in 2006.

MODIS - Moderate resolution Infrared Spectroradiometer. Instrument on NASA Aqua and Terra spacecraft that provide Visible and IR data from 36 channels at sub-point resolutions from 250m to 1 km.

MPEG - Moving Picture Experts Group. Image format used to display animated sequences (movies). Requires considerable system memory to run, depending on movie size.

MTSAT - Multi-purpose Transport SATellite (Japan). Replacement for GMS at 140E since 2005. Also supports transport navigation within Japan.

NCDC - National Climatic Data Center, Asheville, NC. Archive center for all meteorological data, including satellite imagery. Operated by NOAA/NESDIS.

NESDIS - National Environmental Satellite Data, Information Service. Government agency that operates the U.S. civilian weather satellites and provides the data to users. Also operates the environemental data centers such as NGDC and the National Climatic Data Center (NCDC) in Asheville, NC.

NGDC - National Geophysical Data Center, Boulder, Colorado. Archives most imagery from DMSP satellites (OLS, SSM/I microwave data). Also houses the Snow and Ice Data Center.

NOAA - National Oceanographic and AtmosphericAdministration. Refers to a series of low earth orbit satellites at an altitude of 530 miles, operated by the U.S. government agency of the same name. Orbits are sun-synchronous such that they pass over a given location at about the same local time each day.

NPOESS - National Polar Orbiting Environmental Satellite System. Merger of U.S. civilian and military polar orbiting satellite systems to replace the NOAA and DMSP spacecraft beginning around 2012 with the launch of the NPP (NPOESS Prototype).

OLS - Operational Line Scanner. The imager that produces high resolution (0.5 to 2.7 km) visible and infrared imagery from DMSP satellites.

PW - Precipitable Water. Total amount of water vapor within an atmospheric column (expressed in mm) available for precipitation. One of the products derived from the GOES/POES imager or sounder.

RAMSDIS - Regional and Mesoscale Meteorological Satellite Data and Information System. A PC-based display system developed at Colorado State University in the early 1990's to provide frequent animation of GOES imagery and derived products. Most products are now available on the CIRA Web site.

SAA - Satellite Active Archive. Digital archive of satellite imagery from the NOAA polar orbiting series. User can browse through sample images and order digital data online. Now referred to as the Comprehensive Large Array Stewardship System (CLASS).

SeaWIFS - Sea-viewing Wide Field-of-view Sensor. The instrument has eight channels in the visible and near-IR portion of the spectrum (0.4um to 0.9um) at a subpoint resolution of 1.1 km. SeaWIFS data is used to observe ocean color features as well as other phenomena at a frequency of one overpass per day.

SEVIRI - Spinning Enhanced Visible and Infrared Imager. Instrument on the METEOSAT Second Generation (MSG) spacecraft featuring 12 spectral bands. The four Vis and Near IR bands and the eight IR bands have resolutions of 1 km and 3 km, respectively. Available in High (15 min) and Low Rate (30 min) transmissions.

SSM/I - Special Sensor Microwave/Imager. Passive microwave instrument onboard the U.S. Dept. of Defense meteorological satellites (DMSP). Obtains data in seven channels (four wavelengths, three with vertical/horizontal polarization) at resolutions of 25 km (85 Ghz only) and 40 km.

SST - Sea Surface Temperature. Temperature slightly below the ocean surface as measured by ocean buoys and ships or on the ocean surface as measured by satellite infrared measurements.

TIFF - Tagged Image File Format. A compressed file format that is often used for high quality images.

TPW - Total Precipitable Water. The total amount of moisture available for precipitation in an atmospheric column, usually expressed in mm.

Vegetation Index (VI) - Determined using visible and near-IR channels on AVHRR. Denotes relative chlorophyll content of vegetation during daylight conditions, and is thus used to monitor drought conditions.

Vis - Visible satellite imagery that shows reflected sunlight in the ultraviolet portion of the spectrum (0.5 to 1.0 micrometers).

WEFAX - Weather Facsimile. A type of low resolution imagery broadcast directly from a satellite to a user on the ground with proper receiving equipment.

WV - Water Vapor. Imagery available from GOES, MTSAT and METEOSAT that shows middle and upper tropospheric moisture and other significant features.