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The microwave limb sounder (MLS) on the Upper Atmosphere Research Satellite (UARS) is the first satellite experiment using limb sounding techniques at microwave frequencies. Primary measurement objectives are stratospheric ClO, O3, H2O, temperature, and pressure. Measurements are of thermal emission: all are performed simultaneously and continuously and are not degraded by ice clouds or volcanic aerosols. The instrument has a 1.6-m mechanically scanning antenna system and contains heterodyne radiometers in spectral bands centred near 63, 183, and 205 GHz. The radiometers operate at ambient temperature and use Schottky-diode mixers with local oscillators derived from phase-locked Gunn oscillators. Frequency tripling by varactor multipliers generates the 183- and 205-GHz local oscillators, and quasi-optical techniques inject these into the mixers. Six 15-channel filter banks spectrally resolve stratospheric thermal emission lines and produce an output spectrum every 2 s. Thermal stability is sufficient for 'total power' measurements which do not require fast chopping. Radiometric calibration, consisting of measurements of cold space and an internal target, is performed every 65-s limb scan. Instrument in-orbit performance has been excellent, and all objectives are being met.

Antenna for imaging of polar regions has terrestrial applications. Antenna consists of four horizontally-polarized 19.0 by 0.6-m planar waveguide arrays and appropriate feed networks mounted on single aluminum supporting structure. Antenna suitable for high quality imaging of sea ice in polar regions above 60 degrees latitude.

X-band system has 100-m2 resolution. Wide swath imaging radar of synthetic aperature type transmits signal to ground station for subsequent processing into imagery. Concept meets functional requirements for continuously mapping sea ice in north and south polar regions.

The state-of-the-art of active microwave remote sensors (altimeters, scatterometers and imagers) used in geologic applications is assessed and the ongoing radar geology activities within NASA, government agencies, industry, universities and foreign organizations is summarized. Plans for radar geology research and development and space flight missions are also outlined.

A Scanning Multichannel Microwave Radiometer has been designed for the Nimbus-G Spacecraft and incorporated also into the Seasat-A payload for the primary purpose of determining sea surface temperatures and wind stress on a nearly all-weather basis. Observations of microwave polarization components will be made at wavelengths of 0.8, 1.4, 1.7, 2.8, and 4.6 cm over a swath 577 km wide below the Seasat-A spacecraft. The smallest spatial resolution cell is 15 x 23 km at a wavelength of 0.8 cm, and proportionately larger at the other wavelengths. Using experimentally determined algorithms for converting the observed brightness temperatures, the indicated accuracies of the results (excluding conditions of significant rainfall) are within 1 K for sea surface temperature and 2 m/sec for surface wind speeds, over a range from 0-50 m/sec.

The purpose of the Shuttle microwave system experiment (SIMS) is to utilize the capabilities of the Space Shuttle to perform passive microwave measurements of thermal emission from the earth's atmosphere and surface, which can be interpreted in terms of meaningful atmospheric and geophysical parameters. The paper is a status report of an ongoing definition phase study of SIMS. The wavelengths and observable parameters for the SIMS channels are identified. The SIMS instrument is discussed with particular reference to the antenna system. A system consisting of a parabolic torus reflector offset fed by a number of feeds and radiometers on a rotating wheel is determined to be the best antenna configuration for SIMS. A tentative data flow diagram for SIMS is also provided.

The scanning multichannel microwave radiometer (SMMR) is an imaging 5-frequency radiometer flown on the Seasat and Nimbus-7 earth satellites launched in 1978. It measures dual-polarized microwave radiances from the earth's atmosphere and surface, primarily for the purpose of deriving global and nearly all-weather measurements of sea surface temperature, wind speed, and atmospheric liquid water and water vapor. This paper describes the SMMR instrument and its calibration, antenna pattern measurements, and data processing procedures. Analysis of early data from the Seasat SMMR shows that the expected engineering performance in flight was achieved, and the measurement of sea surface temperature and wind speed with accuracies of 1.5 K and 2 m/s, respectively, may be achievable once the geophysical data processing algorithms and analysis have been completed.

The present status of the applications of Synthetic Aperture Radars (SARs) is reviewed, and the technology state-of-the art as represented by the Seasat-A and SIR-A SARs examined. The potential of SAR applications, and the near- and longer-term technology trends are assessed.

A scanning multichannel microwave radiometer (SMMR) has been designed for the Nimbus-G spacecraft and incorporated also into the SeaSat-A payload for the primary purpose of determining sea surface temperatures and wind stress on a nearly all-weather basis. Observations of microwave polarization components will be made at wavelengths of 0.8, 1.4, 1.7, 2.8, and 4.6 cm over a swath 822 km wide below the Nimbus-G and 595 km wide below the SeaSat-A spacecraft. The smallest spatial resolution cell is about 20 km at a wavelength of 0.8 cm, and proportionately larger at the other wavelengths. Using algorithms based on a combination of experimental data and physical models for converting the observed brightness temperatures, the indicated accuracy of the results (excluding conditions of significant rainfall) are within 1 K for sea surface temperature and 2 m/s for surface wind speeds, over a range from 0-50 m/s.

As a result of a growing awareness by the remote sensing community of the unique capabilities of passive and active microwave sensors, these instruments are expected to grow in the next decade in numbers, versatility and complexity. The Nimbus-G and Seasat-A Scanning Multichannel Microwave Spectrometer (SMMR), the Seasat-A radar altimeter, scatterometer and synthetic aperture radar represent the first systematic attempt at exploring a wide variety of applications utilizing microwave sensing techniques and are indicators of the directions in which the pertinent technology is likely to evolve. The trend is toward high resolution multi-frequency imagers spanning wide frequency ranges and wide swaths requiring sophisticated receivers, real-time data processors and most importantly, complex antennas.

Microwave radiometers measure thermal electromagnetic radiation at frequencies ranging over the entire radio spectrum, from audio to infrared. The temperatures of black-body radiators can be measured with sensitivities better than 0.01 K, and with absolute accuracies better than 0.5 K. Radiometric systems have been built with as many as 400 independent spectral channels. Frequency resolutions range from hertz to gigahertz; and integration times range from microseconds to hours. Radiometric systems have operated reliably on the ground, and in balloons, aircraft, and spacecraft, including the 1962 Mariner 2 planetary probe to Venus.

A prototype of the Nimbus E microwave spectrometer was flown in an airplane over various atmospheric and surface conditions. Effects of clouds and the terrestrial surface on the data are discussed. Using a multiple-regression statistical method of inverting the equation of radiative transfer, estimates of temperature and integrated contents of water vapor and liquid water in the atmosphere below the aircraft were made from the microwave data obtained at high altitude. These estimates are compared with direct measurements made by other experiments on board the aircraft, in both clear atmospheres and in the presence of clouds.

Venus/Mercury swingby with Venus capsule - preliminary science objectives and experiments for use in advanced mission studies

Mission planning and experiment design for future Mariner-type Venus space probes

Microwave radiometry applied to oceanography

Mariner ii spacecraft microwave radiometer experiment & venus space probe

Description of the radiometer carried by the mariner ii space probe

Description of a microwave radiometer used on the mariner venus probe

A five-channel microwave spectrometer operating near the 1.35-cm wavelength water vapor and the 5-mm wavelength oxygen resonances was flown in the NASA Convair 990 aircraft at altitudes near 12 km and used to infer layer thicknesses and water vapor and liquid water abundances in the troposphere. The calibration of the spectrometer and a multiple regression method of interpretation of the data obtained from the flights are described. Possible errors from clouds and from the terrestrial surface are discussed. Values of atmospheric layer thicknesses, water vapor content, and liquid water content inferred from microwave data obtained over two frontal systems are presented. The inferred values of 1000- to 500-mb and 500- to 250-mb thicknesses agree with directly measured values to within 15 meters at the places where the direct measurements were made. This agreement is equivalent to errors of less than 1 K in mean temperature.