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A microwave radiometer (MWR) is a radiometer that measures energy emitted at one millimeter-to-metre wavelengths (frequencies of 0.3–300 GHz) known as microwaves. Microwave radiometers are very sensitive receivers designed to measure thermally-emitted electromagnetic radiation. They are usually equipped with multiple receiving channels to derive the characteristic emission spectrum of planetary atmospheres, surfaces or extraterrestrial objects. Microwave radiometers are utilized in a variety of environmental and engineering applications, including remote sensing, weather forecasting, climate monitoring, radio astronomy and radio propagation studies.
The Nimbus satellites were second-generation U.S. robotic spacecraft launched between 1964 and 1978 used for meteorological research and development. The spacecraft were designed to serve as stabilized, Earth-oriented platforms for the testing of advanced systems to sense and collect atmospheric science data. Seven Nimbus spacecraft have been launched into near-polar, sun-synchronous orbits beginning with Nimbus 1 on August 28, 1964. On board the Nimbus satellites are various instrumentation for imaging, sounding, and other studies in different spectral regions. The Nimbus satellites were launched aboard Thor-Agena rockets and Delta rockets.
The National Snow and Ice Data Center (NSIDC) is a United States information and referral center in support of polar and cryospheric research. NSIDC archives and distributes digital and analog snow and ice data and also maintains information about snow cover, avalanches, glaciers, ice sheets, freshwater ice, sea ice, ground ice, permafrost, atmospheric ice, paleoglaciology, and ice cores.
The Special Sensor Microwave/Imager (SSM/I) is a seven-channel, four-frequency, linearly polarized passive microwave radiometer system. It is flown on board the United States Air Force Defense Meteorological Satellite Program (DMSP) Block 5D-2 satellites. The instrument measures surface/atmospheric microwave brightness temperatures (TBs) at 19.35, 22.235, 37.0 and 85.5 GHz. The four frequencies are sampled in both horizontal and vertical polarizations, except the 22 GHz which is sampled in the vertical only.
A polar ice cap or polar cap is a high-latitude region of a planet, dwarf planet, or natural satellite that is covered in ice.
Seasat was the first Earth-orbiting satellite designed for remote sensing of the Earth's oceans and had on board one of the first spaceborne synthetic-aperture radar (SAR). The mission was designed to demonstrate the feasibility of global satellite monitoring of oceanographic phenomena and to help determine the requirements for an operational ocean remote sensing satellite system. Specific objectives were to collect data on sea-surface winds, sea-surface temperatures, wave heights, internal waves, atmospheric water, sea ice features and ocean topography. Seasat was managed by NASA's Jet Propulsion Laboratory and was launched on 27 June 1978 into a nearly circular 800 km (500 mi) orbit with an inclination of 108°. Seasat operated until 10 October 1978 (UTC), when a massive short circuit in the Agena-D bus electrical system ended the mission.
The coastal zone color scanner (CZCS) was a multi-channel scanning radiometer aboard the Nimbus 7 satellite, predominately designed for water remote sensing. Nimbus 7 was launched 24 October 1978, and CZCS became operational on 2 November 1978. It was only designed to operate for one year (as a proof-of-concept), but in fact remained in service until 22 June 1986. Its operation on board the Nimbus 7 was limited to alternate days as it shared its power with the passive microwave scanning multichannel microwave radiometer.
The International Permafrost Association (IPA), founded in 1983, is an international professional body formed to foster the dissemination of knowledge concerning permafrost and to promote cooperation among individuals and national or international organisations engaged in scientific investigation and engineering work related to permafrost and seasonally frozen ground. The IPA became an Affiliated Organisation of the International Union of Geological Sciences in July 1989.
NOAA-7, known as NOAA-C before launch, was an American operational weather satellite for use in the National Operational Environmental Satellite System (NOESS) and for the support of the Global Atmospheric Research Program (GARP) during 1978-1984. The satellite design provided an economical and stable Sun-synchronous platform for advanced operational instruments to measure the atmosphere of Earth, its surface and cloud cover, and the near-space environment. An earlier launch, NOAA-B, was scheduled to become NOAA-7, however NOAA-B failed to reach its required orbit.
Measurement of sea ice is important for safety of navigation and for monitoring the environment, particularly the climate. Sea ice extent interacts with large climate patterns such as the North Atlantic oscillation and Atlantic Multidecadal Oscillation, to name just two, and influences climate in the rest of the globe.
The electrically scanning microwave radiometer (ESMR) was an instrument carried by the Nimbus 5 satellite, precursor to the scanning multichannel microwave radiometer (SMMR) and special sensor microwave/imager (SSM/I) instruments.
NOAA-6, known as NOAA-A before launch, was an American operational weather satellite for use in the National Operational Environmental Satellite System (NOESS) and for the support of the Global Atmospheric Research Program (GARP) during 1978-1984. The satellite design provided an economical and stable Sun-synchronous platform for advanced operational instruments to measure the atmosphere of Earth, its surface and cloud cover, and the near-space environment.
NOAA B was an American operational weather satellite for use in the National Operational Environmental Satellite System (NOESS) and for the support of the Global Atmospheric Research Program (GARP) during 1978-1984. The satellite design provided an economical and stable Sun-synchronous platform for advanced operational instruments to measure the atmosphere of Earth, its surface and cloud cover, and the near-space environment.
Sea ice concentration is a useful variable for climate scientists and nautical navigators. It is defined as the area of sea ice relative to the total at a given point in the ocean. This article will deal primarily with its determination from remote sensing measurements.
ADEOS I was an Earth observation satellite launched by NASDA in 1996. The mission's Japanese name, Midori means "green". The mission ended in July 1997 after the satellite sustained structural damage to the solar panel. Its successor, ADEOS II, was launched in 2002. Like the first mission, it ended after less than a year, also following solar panel malfunctions.
The Arctic ice pack is the sea ice cover of the Arctic Ocean and its vicinity. The Arctic ice pack undergoes a regular seasonal cycle in which ice melts in spring and summer, reaches a minimum around mid-September, then increases during fall and winter. Summer ice cover in the Arctic is about 50% of winter cover. Some of the ice survives from one year to the next. Currently, 28% of Arctic basin sea ice is multi-year ice, thicker than seasonal ice: up to 3–4 m (9.8–13.1 ft) thick over large areas, with ridges up to 20 m (65.6 ft) thick. Besides the regular seasonal cycle there has been an underlying trend of declining sea ice in the Arctic in recent decades as well.
The Weddell Polynya, or Weddell Sea Polynya, is a polynya or irregular area of open water surrounded by sea ice in the Weddell Sea of the Southern Ocean off Antarctica and near the Maud Rise. The formation of the polynya exposes relatively warmer ocean waters to a cold atmosphere, leading to a large exchange of heat which drives deep convection in the ocean, often reaching depths of a 1,000 to 2,000 meters.
Nimbus 7 was a meteorological satellite. It was the seventh and last in a series of the Nimbus program.
Nimbus 5 was a meteorological satellite for research and development of sensing technology. It was the fifth successful launch in a series of the Nimbus program.
Eni G. Njoku is a Nigerian-American scientist specializing in microwave remote sensing. He worked at the Jet Propulsion Laboratory (JPL), California Institute of Technology, where he was responsible for developing techniques for sea surface temperature and soil moisture remote sensing using microwave radiometers. He produced the first microwave-derived sea surface temperature maps from space, and developed the first application of deployable mesh antennas for satellite Earth observation. From 2008-2013, he served as project scientist of NASA's first soil moisture mission, the Soil Moisture Active Passive (SMAP) mission, launched in 2015.
References
Jezek, K.C., C. Merry, D. Cavalieri, S.Grace, J. Bedner, D. Wilson and D. Lampkin 1991: Comparison between SMMR and SSM/I passive microwave data collected over the Antarctic Ice Sheet. Byrd Polar Research Center, The Ohio State university, Columbus, OH., BPRC Technical Report Number 91-03, ISSN 1056-8050.
