Radiometric measurements of the microwave emissivity of foam

Includes bibliographical references.Radiometric measurements of the microwave emissivity of foam were conducted during May 2000 at the Naval Research Laboratory's Chesapeake Bay Detachment using radiometers operating at 10.8 and 36.5 GHz. Horizontal and vertical polarization measurements were performed at 36.5 GHz; horizontal, vertical, +45°, ­45°, left-circular, and right-circular polarization measurements were obtained at 10.8 GHz. These measurements were carried out over a range of incidence angles from 30° to 60°. Surface foam was generated by blowing compressed air through a matrix of gas-permeable tubing supported by an aluminum frame and floats. Video micrographs of the foam were used to measure bubble size distribution and foam layer thickness. A video camera was boresighted with the radiometers to determine the beam-fill fraction of the foam generator. Results show emissivities that were greater than 0.9 and approximately constant in value over the range of incidence angles for vertically polarized radiation at both 10.8 and 36.5 GHz, while emissivities of horizontally polarized radiation showed a gradual decrease in value as incidence angle increased. Emissivities at +45°, ­45°, left-circular, and right-circular polarizations were all very nearly equal to each other and were in turn approximately equal to the average values of the horizontal and vertical emissivities in each case.This work was sponsored by the Department of the Navy, Office of Naval Research under Award N0014-00-1-280 to the University of Massachusetts, Award N00014-00-0152 to the University of Washington, and Award N0001400WX21032 to the Naval Research Laboratory

Guest Editorial Foreword to the Special Issue on the 9th Specialist Meeting on Microwave Radiometry and Remote Sensing Applications (MicroRad ’06)

HE 9th Specialist Meeting on Microwave Radiometry and Remote Sensing Applications (MicroRad ’06) was held from February 28 to March 3, 2006, in San Juan, Puerto Rico, a Commonwealth of the USA. The conference was chaired by Dr. Steven Reising of Colorado State University, Fort Collins, and the local organizing chair was Dr. Sandra Cruz-Pol of the University of Puerto Rico at Mayagüez. The objective of MicroRad ’06 was to provide an open forum to report and discuss recent advances in the field of microwave radiometry and to gather all parties, including the research, industrial, and academic communities, who are involved in projects and studies in microwave radiometry of the land, oceans, and atmosphere. The meeting was highly successful, with 125 participants from 15 countries, 146 submitted abstracts, 80 oral presentations, and 50 interactive posters during four full days of sessions. MicroRad ’06 is the most recent in a series of meetings focusing on Microwave Radiometry and Remote Sensing of the Environment, dating back to 1983 when the first MicroRad meeting was organized and hosted by the late Prof. Giovanni d’Auria of the University “La Sapienza” of Rome, Italy. An In Memoriam article for Prof. d’Auria appeared on p. 8 of the IEEE GRSS Newsletter, Issue #142, March 2007. The second MicroRad meeting was held in Florence, Italy, organized and chaired by Dr. Paolo Pampaloni at Istituto di Ricerca sulle Onde Elettromagnetiche, Consiglio Nazionale delle Ricerche. Since then, MicroRad meetings have been held approximately every 2 1/2 years, alternating between the USA and Italy. Previous MicroRad meetings in the USA were held in Boulder, CO (1992 and 2001), and in Boston, MA (1996). The MicroRad meetings in Italy were convened in Rome at “La Sapienza” (1983 and 2004) and at “Tor Vergata” (1994), as well as in Florence (1988 and 1999). The technical program of MicroRad ’06 opened with a session on microwave radiometer calibration, featuring presentations on current and planned radiometer systems by representatives of government agencies, industry, and universities. The focus on sensors continued with a session devoted to instru- Digital Object Identifier 10.1109/TGRS.2007.900318 mentation and advanced techniques and one on radiofrequency interference (RFI) mitigation. The first day concluded with a session on experimental campaigns, which included airborne and ground-based measurements as well as calibration and validation of spaceborne sensors. The second day shifted to consideration of science application areas, which began with a session on soil moisture and salinity satellite missions at L-band. This was followed by sessions focusing on ocean wind, sea ice, electromagnetic modeling of the sea surface, and snow cover. The morning of the third day focused on land surfaces with sessions on snow cover, soil moisture, vegetation, and electromagnetic modeling of microwave emission from the land and the cryosphere. On the afternoon of the third day, the emphasis shifted to weather and the atmosphere, starting with two sessions on retrieval methodologies and radiance assimilation. These included four presentations from government laboratories on both sides of the Atlantic to highlight rapid advances in numerical weather prediction and direct applications of satellite radiances. Finally, the fourth and final day of MicroRad ’06 focused on atmospheric remote sensing, which emphasized temperature and humidity in the morning and clouds and precipitation in the afternoon, including many presentations on ground-based techniques and sensor design. At the conclusion of each of the 16 oral sessions of MicroRad ’06, the co-chairs introduced the poster papers on the topic of the session. The long coffee breaks each morning and afternoon provided plenty of time for discussion with poster presenters, which gave the conference the distinctive academic flavor typical of MicroRad meetings