NOAA The Polar-Orbiting, Operational, Environmental Satellite #<°1% U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration The blunt, square-winged object hurtles out of earth's night into the unfiltered sunlight that beats through the vacuum of space. It is a box about the size of a large air-conditioner, from one end of which three rectangular panels extend at right angles to one another, like awkward, flightless wings. Sunlight transforms it. The gold foil in which the oblong body is wrapped gleams; the indigo panels which compose the wings grow bright and drink the energy of the sun. This is a NOAA spacecraft, one of a series oper- ated by the National Environmental Satellite Serv- ice of the U.S. Commerce Department's National Oceanic and Atmospheric Administration. It is half of a team of satellites — the others "hang" in geo- stationary orbit nearly 22,000 statute miles (35,000 kilometers) farther out in space — and evolved from the experimental TIROS* series and the operational ESSA vehicles of the TOS series. Between them, the NOAA and geostationary satellites constitute the national operational environmental satellite system. •TIROS is the acronym lor Television Infrared Observation Sat- tellite; TOS, lor TIROS Operational System, in which the space- craft themselves were called ESSA, lor Environmental Survey Sat- ellite; ITOS, lor Improved TIROS Operational System, l/ie first ol wh/c/l was designated TIROS M until launched, then ITOS-I. Successive satellites in the ITOS series are designated NOAA, lor the operating agency, and numbered consecutively. From their 900-statute-mile (1, 500-kilometer) high, nearly circular, nearly polar orbit, NOAA sat- ellites face the earth's surface continuously. The orbital period of the spacecraft is about 114 min- utes, so that for each pass the earth has rotated 28.5 degrees to the east. The combination of satel- lite motion and the earth's rotation beneath the orbit provides overlapping strips of satellite imag- ery covering a swath about 2,100 statute miles (3,400 kilometers) wide from pole to pole. NOAA satellites after NOAA-1 carry no cameras. Their radiometers scan the planet's surface and at- mosphere, sensing what can be seen in visible light and infrared and sounding the atmospheric col- umn for temperatures and water vapor. A solar proton monitor measures the energetic particles flowing earthward from the sun. Duplicate sets of three principal instruments are carried by the spacecraft: a scanning radiometer (SR), a very-high- resolution radiometer (VHRR), and a vertical tem- perature profile radiometer (VTPR). Scanning radiometer images are available as di- rect-readout transmissions to any suitably equipped ground stations within radio range of the satellite. These images cover an area about 2,100 statute miles (3,400 kilometers) wide in strips up to 5,000 statute miles (8,000 kilometers) long. The SR data are also stored on tape recorders in the satellite and transmitted to the Satellite Service's Command and Data Acquisition (CDA) stations at Cilmore Creek, Alaska, and Wallops Station, Virginia. This instru- ment senses in both the visible and infrared and its stored-data images can resolve objects down to two nautical miles (four kilometers). Images from the very-high-resolution radiometer, which senses in both visible and infrared channels, are similar to those taken by the scanning radio- meter, but have much better resolution — about half a mile (one kilometer). Only limited amounts of VHRR data are stored by the satellite and trans- mitted to CDA stations. The radiometer operates primarily in a direct readout mode, transmitting data as it is obtained to relatively complex "S-band" re- ceiving stations. NOAA's VHRR receivers are at the CDA stations in Virginia and Alaska, and at a ground station in Redwood City, California. The vertical temperature profile radiometer meas- ures infrared energy radiated at six narrow spectral intervals of the atmosphere and at either the surface or cloud tops. These measurements are used to cal- culate the vertical temperature distribution — or tem- perature profile — of the atmosphere beneath the satellite. The instrument also provides information on the total moisture content of the atmospheric column observed. The VTPR sounds the atmosphere The NOAA orbit is about 900 statute miles (1,500 kilometers) hrs^h, nearly circular, and nearly polar, with the scanning and very-high-resolution radio- meters covering some 26 million square miles (75 million square kilometers) along a pole-to-pole swath about 2,100 statute miles (3,400 kilometers) wide. The spacecraft crosses the equator northbound nine hours behind (9 p.m. local lime) and south- bound Ihree hours ahead (9 a.m. local lime) ni the sun. An eastward drift Jul the orbit (below) holds the spacecraft al these local times t hr ough flic year. every half second as the radiometer sweeps across the orbital path in a 23-step scan, covering a 37- statute-mile (60-kilometer) square on the earth's sur- face with each step, and a total area of 850 statute miles (1,350 kilometers) by 37 statute miles (60 kil- ometers) in each scan. In this way, the device pro- vides environmental scientists with virtually global coverage of vertical temperature distributions. These data are also used to calculate geopotential height — the actual altitude of a specific pressure level in the atmosphere. In addition to direct broadcast over the radio beacon, VTPR output is transmitted by the sat- ellite on command to NOAA's CDA stations, and re- layed to the National Environmental Satellite Service, Suitland, Maryland, for analysis and processing. The solar proton monitor (SPM) aboard the NOAA spacecraft detects the arrival of energetic solar pro- tons in the vicinity of earth. These data are trans- mitted to the CDA stations by the satellite, relayed to Suitland, and from there to NOAA's Space Envi- ronment Laboratory in Boulder, Colorado, where they become part of the routine of reporting and forecasting the geophysical effects of solar events. Radiometer data from NOAA satellites are fash- ioned by the National Environmental Satellite Serv- ice into a large family of products that can be ap- plied by meteorologists, oceanographers, and other environmental scientists — and the family is growing rapidly. They include computer-prepared mosaics of global cloud cover in several map projections, daily global analyses of sea surface temperatures in cloud- free areas, and, from the VHRR output, high-resolu- tion sea-surface temperature analyses for selected areas where such information can be used to moni- tor bay and estuarine circulation for pollution con- trol, trace the thermal boundaries of fisheries, and acquire a better understanding of ocean dynamics. VHRR observations of ice on oceans, lakes, and riv- ers provide data useful to navigation, and high-reso- lution observations of snowpack in remote areas assist hydrologists in assessing spring flood potential. Special products include three-dimensional repre- sentations of atmospheric temperature and motion, and minimum brightness mosaics, which average the clouds out of satellite images and show a "bare" earth and its areas of snow and ice cover. The National Meteorological Center of NOAA's National Weather Service uses most of the data products developed there routinely, as part of the day-to-day analysis and forecasting of national and global weather. This information is also transmitted over facsimile circuits to National Weather Service offices across the Nation, and to other environ- mental science organizations here and abroad. NOAA satellite output includes two channels each from the scanning radiometer and the very-high- resolution radiometer, a channel from the vertical temperature profile radiometer, and a channel from the solar proton monitor. Shown here are (1) VHRR visible, (2) VHRR infrared, (3) SR visible, (4) SR infra- red, (5) the solar proton flux data prepared from the satellite output by NOAA's Space Environment Lab- oratory in Colorado, and (6) VTPR analysis used by National Meteorological Center forecasters. AQD0D70 t mfl31fl NOAA and its National Environmental Satellite Service work at the threshold of the new science and technology behind our ability to observe the environment from space. NESS operates one of the Nation's two operational civil satellite systems and is developing new ways of using this system and its massive output of environmental data for the general benefit. NESS, with headquarters in Suitland, Maryland, has also developed a field organization to support the expanding local role of satellite data in envi- ronmental analysis, forecasting, and warning. This includes the two Command and Data Acquisition Stations at Cilmore Creek, Alaska, and Wallops Sta- tion, Virginia, the S-band VHRR receiver facility at Redwood City, California, and Satellite Field Service Stations, co-located with selected National Weather Service centers and offices, to receive and interpret data from the operational geostationary satellite, and to provide regional services to data users in the field. Global weather is international, and NESS is a major element in the World Meteorological Center in Washington, along with the National Meteoro- logical Center and NOAA's Environmental Data Serv- ice. This is one of three world data centers estab- lished under the United Nations' World Meteoro- logical Organization; the others are in Moscow and Melbourne. 'Went of c NOAA/PA 73020 1974 GPO : 1974 O - 530-470