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.
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 Active Cavity Radiometer Irradiance Monitor Satellite, or ACRIMSAT was a satellite carrying the ACRIM-3 instrument. It was one of the 21 observational components of NASA's Earth Observing System program. The instrument followed upon the ACRIM-1 and ACRIM-2 instruments that were launched on multi-instrument satellite platforms. ACRIMSAT was launched on 20 December 1999 from Vandenberg Air Force Base as the secondary payload on the Taurus launch vehicle that launched KOMPSAT. It was placed into a high inclination of 98.30°, at 720 km. Sun-synchronous orbit from which the ACRIM-3 instrument monitored total solar irradiance (TSI). Contact with the satellite was lost on 14 December 2013.
Aquarius was a NASA instrument aboard the Argentine SAC-D spacecraft. Its mission was to measure global sea surface salinity to better predict future climate conditions.
OSTM/Jason-2, or Ocean Surface Topography Mission/Jason-2 satellite, was an international Earth observation satellite altimeter joint mission for sea surface height measurements between NASA and CNES. It was the third satellite in a series started in 1992 by the NASA/CNES TOPEX/Poseidon mission and continued by the NASA/CNES Jason-1 mission launched in 2001.
Soil Moisture and Ocean Salinity (SMOS) is a satellite which forms part of ESA's Living Planet Programme. It is intended to provide new insights into Earth's water cycle and climate. In addition, it is intended to provide improved weather forecasting and monitoring of snow and ice accumulation.
SAC-D, also known as Aquarius after its primary instrument, is an Argentine Earth science satellite built by INVAP and operated by CONAE. SAC-D was launched from Vandenberg Air Force Base on 10 June 2011, with a planned mission life of five years. Due to a power system failure, the mission was ended on 8 June 2015.
SARAL is a cooperative altimetry technology mission of Indian Space Research Organisation (ISRO) and Centre National d'Études Spatiales (CNES). SARAL performs altimetric measurements designed to study ocean circulation and sea surface elevation.
The Spaceborne Imaging Radar (SIR) – full name 'Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR)', is a synthetic aperture radar which flew on two separate shuttle missions. Once from the Space Shuttle Endeavour in April 1994 on (STS-59) and again in October 1994 on (STS-68). The radar was run by NASA's Space Radar Laboratory. SIR utilizes 3 radar frequencies: L band, C band (6 cm) and X band (3 cm), allowing for study of geology, hydrology, ecology and oceanography. Comparing radar images to data collected by teams of people on the ground as well as aircraft and ships using simultaneous measurements of vegetation, soil moisture, sea state, snow and weather conditions during each flight. The imaging radar was able to take images anytime regardless of clouds cover. The Radar-C system was built and operated by NASA's Jet Propulsion Laboratory (JPL). The mission was a joint work of NASA with the German and Italian space agencies. Each of the week long mission scanned about 50 million square kilometers of the Earth's surface,.
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 Suomi National Polar-orbiting Partnership, previously known as the National Polar-orbiting Operational Environmental Satellite System Preparatory Project (NPP) and NPP-Bridge, is a weather satellite operated by the United States National Oceanic and Atmospheric Administration (NOAA). It was launched in 2011 and is currently in operation.
The Cyclone Global Navigation Satellite System (CYGNSS) is a space-based system developed by the University of Michigan and Southwest Research Institute with the aim of improving hurricane forecasting by better understanding the interactions between the sea and the air near the core of a storm.
ExoCube (CP-10) is a space weather satellite developed by the California Polytechnic State University – San Luis Obispo and sponsored by the National Science Foundation. It is one of many miniaturized satellites that adhere to the CubeSat standard. ExoCube's primary mission is to measure the density of hydrogen, oxygen, helium, and nitrogen in the Earth's exosphere. It is characterizing [O], [H], [He], [N2], [O+], [H+], [He+], [NO+], as well as the total ion density above ground stations, incoherent scatter radar (ISR) stations, and periodically throughout the entire orbit. It was launched aboard a Delta II rocket with the NASA SMAP primary payload from Vandenberg AFB in California on January 31, 2015.
Mars Cube One was a Mars flyby mission launched on 5 May 2018 alongside NASA's InSight Mars lander. It consisted of two nanospacecraft, MarCO-A and MarCO-B, that provided real-time communications to Earth for InSight during its entry, descent, and landing (EDL) on 26 November 2018 - when InSight was out of line of sight from the Earth. Both spacecraft were 6U CubeSats designed to test miniaturized communications and navigation technologies. These were the first CubeSats to operate beyond Earth orbit, and aside from telecommunications they also tested CubeSats' endurance in deep space. On 5 February 2019, NASA reported that both the CubeSats had gone silent by 5 January 2019, and are unlikely to be heard from again. In August 2019, the CubeSats were honored for their role in the successful landing of the InSight lander on Mars.
Lunar Flashlight was a low-cost CubeSat lunar orbiter mission to explore, locate, and estimate size and composition of water ice deposits on the Moon for future exploitation by robots or humans.
ISS-RapidScat was an instrument mounted to the International Space Station'sColumbus module that measured wind speeds. It was launched aboard SpaceX CRS-4 in September 2014 and operated until August 2016. ISS-RapidScat was a scatterometer designed to support weather forecasting by bouncing microwaves off the ocean's surface to measure wind speed via wind waves. It featured a 75 cm (30 in) rotating radar dish that operated at 13.4 GHz. It could collect data between 51.6 degrees north and south latitude, with a swath 900 km wide (560 mi).
NOAA-20, designated JPSS-1 prior to launch, is the first of the United States National Oceanic and Atmospheric Administration's latest generation of U.S. polar-orbiting, non-geosynchronous, environmental satellites called the Joint Polar Satellite System. NOAA-20 was launched on 18 November 2017 and joined the Suomi National Polar-orbiting Partnership satellite in the same orbit. NOAA-20 operates about 50 minutes behind Suomi NPP, allowing important overlap in observational coverage. Circling the Earth from pole-to-pole, it crosses the equator about 14 times daily, providing full global coverage twice a day. This gives meteorologists information on "atmospheric temperature and moisture, clouds, sea-surface temperature, ocean color, sea ice cover, volcanic ash, and fire detection" so as to enhance weather forecasting including hurricane tracking, post-hurricane recovery by detailing storm damage and mapping of power outages.
TROPICS(Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of Smallsats) is a 2023 NASA constellation of six small satellites, 3U CubeSats, that will measure temperature and moisture profiles and precipitation in tropical systems with unprecedented temporal frequency. This data will enable scientists to study the dynamic processes that occur in the inner core of the storm resulting in rapid genesis and intensification. William Blackwell of the Massachusetts Institute of Technology's Lincoln Laboratory in Lexington, Massachusetts is the principal investigator. The constellation was initially planned to be delivered to orbit on three launches between June and July 2022. Due to the loss of the first two satellites after a launch failure in June 2022, the first satellites were delivered to orbit aboard a Rocket Lab Electron rocket on 7 May 2023.
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.
