Abstract: Microwave radiometers measure natural thermal emission in the microwave portion of the electromagnetic spectrum, with most instruments operating in the range from 0.3-200 GHz. These instruments provide information on thermodynamic and constituent makeup of an observed volume. JPL has been developing microwave radiometers since the early 1960s, the first being for the Mariner 2 spacecraft, which explored Venus in 1962. This radiometer, which operated at 16 and 22 GHz, allowed scientists to peer beneath the thick clouds to reveal that Venus has a hot surface. Subsequent to this, JPL led the development of many microwave radiometers for Earth science, the first being the Scanning Multi-Channel Microwave Radiometer that flew on the Nimbus-7 satellite from 1978 to 1987 and led to many advances in the field of microwave radiometry; it is recognized that the start of the passive microwave sea ice climate data record begins with its data. Next, the Microwave Scanning Unit and the Microwave Limb Sounder were developed. The Microwave Scanning Unit was the predecessor to the cross-track sounding instruments currently flown by NOAA that have been shown to have the most significant impact on weather forecast accuracy, among all data sources assimilated into the weather models. In 1992 Topex/Poseidon was launched to measure sea-surface topography using a radar altimeter, which included a microwave radiometer to correct for the propagation delay of the radar signal through the troposphere due of water vapor. This led to a family of altimeter radiometers that were developed from the late 1990s to present for the Jason series missions, with each successive generation improving upon the last. These advancements in radiometer technology enabled the development of the Juno microwave radiometer system that is currently exploring the inner depths of Jupiter’s thick atmosphere and the Compact Ocean Wind Vector Radiometer system that provides measurements of the wind’s speed and direction over the surface of Earth’s oceans -- an example of a new generation of small-satellite radiometer that could play an important role in the future Earth observation system. Other yet smaller systems under development include TEMPEST, intended to measure precipitation development with a tandem of 6U cubesat systems. This talk will highlight the developments of the past and how they relate to ongoing and future research in microwave radiometry at JPL. Along the way, key science resulting from the various instruments will be presented, ranging from the first-ever time-continuous thermodynamic observations of a rapidly intensifying hurricane on Earth to observations enabling the understanding the deep circulation within Jupiter. Finally, prospects for the future of radiometry will be presented focusing on emerging technology trends and what small-satellite systems could mean for observing the Earth system like never before.
Bio: Brown joined JPL in 2005 as a member the Microwave Advanced Systems Section. He received a B.S degree in meteorology from Pennsylvania State University followed by an M.S. in atmospheric science and a Ph.D. in geoscience and remote sensing from the University of Michigan. He has been involved with the Topex, Jason 1, 2 and 3 microwave radiometers and the WindSat polarimetric radiometer. He is currently the principal investigator of the Compact Ocean Wind Vector Radiometer being developed for the U.S. Air Force and instrument scientist for the microwave radiometer on Juno. He is a member of the science team for the Ocean Surface Topography Mission and SMAP. He received a NASA Exceptional Achievement Medal in 2009 and the JPL Lew Allen Award in 2010. He has also received four NASA Group Achievement Awards.
