Application review panel: High resolution passive microwave satellites
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Staelin, D. H.↗
Engineering topics
Staelin, D. H.
Publications and source records attributed to Staelin, D. H..
Microwave spectroscopic imagery of the earth
The microwave spectrometer on the Nimbus 6 satellite has produced the first microwave spectral images of the earth. It has yielded global maps of (1) atmospheric temperature profiles, (2) the distributions of water vapor and liquid water over ocean, and (3) the coverage and type of ice and snow. The method has potential for operational synoptic monitoring.
Staelin, D. H.↗
Possible effect of subsurface inhomogeneities on the lunar microwave spectrum
Inhomogeneities beneath the lunar surface could alter the average microwave emission spectrum of the moon in a fashion generally consistent with observations, even in the absence of an average heat flux or density gradients with depth. The lunar subsurface was modeled as an inhomogeneous lossy dielectric with three-dimensional refractive-index fluctuations characterized by independent horizontal and vertical correlation lengths. The model suggests that attempts to infer the physical properties of the moon from the lunar microwave spectrum could be significantly inaccurate if subsurface scattering were neglected.
Fisher, A. D.↗
Theory for microwave thermal emission from a layer of cloud or rain
Microwave thermal emission from a layer of cloud or rain consisting of spherical particles has been investigated. Scattering effects are studied in great detail with both numerical and analytical approaches. In the absence of ground emission, it is found that scattering induces brightening for optically thin layers and vice versa for optically thick layers. As a function of observation angle, brightening occurs near nadir, while darkening occurs at large angles in the case of small optical thickness. For large optical thickness, darkening occurs at all angles because of backscattering effects. When the layer of cloud or rain is above an air layer and an ocean surface at a higher temperature, it is found that the darkening effect at large optical thickness is much more pronounced. The darkening effect is also larger for vertical polarizations because the ocean emits more vertically polarized components. The effect of thermal emission and molecular absorption by atmospheric gases is also taken into account. Results obtained from analytical formulas under single-scattering assumptions are compared and illustrated.
Tsang, L.↗
Inversion of passive microwave remote sensing data from satellites
Global passive microwave observations from earth-orbiting satellites have mapped humidity and liquid water over ocean, temperature profiles, ice and snow, and other geophysical parameters. In most applications, the inversion problem is adequately approximated as linear with jointly Gaussian statistics, and, thus, a linear retrieval performs well. In some cases, the problem is typically factored into a decision process followed by appropriate linear or quasilinear processes. Certain problems, however, require more powerful nonlinear or nonstationary procedures, such as Kalman filtering.
Staelin, D. H.↗
Atmospheric sounding with passive microwaves: Review and prognosis
Global maps of temperature profiles from 0 to 20 km altitude and of total water vapor and liquid water over the ocean were obtained from satellite-borne microwave spectrometers. Future satellites will extend the altitude range above 100 km and permit monitoring of H2O, O3, CO, N2O, and other trace constituents. Operational microwave temperature sounding spectrometers are scheduled for launch on both military and civilian U.S. satellites, and future improvements can be expected.
Staelin, D. H.↗
Atmospheric sounding with passive microwaves - Review and prognosis
Global maps of temperature profiles 0-20 km and of total water vapor and liquid water over ocean have been obtained from satellite-borne microwave spectrometers. Future satellites should extend the altitude range above 100 km and permit monitoring of H2O, O3, CO, N2O, and other trace constituents. Operational microwave temperature-sounding spectrometers are scheduled for launch on both military and civilian U.S. satellites, and future improvements can be expected.
Staelin, D. H.↗
Remote sensing of atmospheric water vapor and liquid water with the Nimbus 5 microwave spectrometer
The Nimbus 5 satellite is provided with a passive microwave spectrometer (NEMS) incorporating channels at 22.235 and 31.4 GHz to measure atmospheric water vapor and liquid water over ocean. The discussion covers principles of atmospheric water determination, accuracy of measurements, observations of specific storms and fronts, and observations of water vapor and liquid water on a global scale. The NEMS experiment has demonstrated the ability of a two-channel microwave spectrometer to determine integrated abundances of water vapor and liquid water with estimated rms accuracies of 0.2 and 0.01 g per sq cm, respectively. The data can be used to plot global maps or accumulate global statistics.
Staelin, D. H.↗
Snow and ice surfaces measured by the Nimbus 5 microwave spectrometer
The 22.2- and 31.4-GHz channels of the microwave spectrometer on board the Nimbus 5 earth observatory satellite provide information about the global distribution and character of various types of snow and ice. Observations for the winter and summer of 1973 are presented for both polar regions. Well-defined spectral signatures are found for snow, sea ice, and land ice in Greenland and Antarctica. A simple model with subsurface temperature gradients in a lossy homogeneous dielectric does not account for the observations; internal scattering effects appear to play a dominant role.
Kunzi, K. F.↗
Retrieval of atmospheric temperature profiles by a scanning microwave spectrometer
The Nimbus-6 satellite carries a scanning microwave spectrometer (SCAMS) experiment. The five frequency bands observed are near 22.2, 31.6, 52.8, 53.8, and 55.4 GHz. The calibration system permitted preflight calibration to an accuracy of about 1 K. In orbit, small empirical corrections were made to the calibration constants to obtain agreement in the mean of SCAMS measurements with computations based on conventional data analyzed by the National Meteorological Center (NMC). Global maps of temperature profiles were retrieved from the SCAMS measurements by a statistical method. Using the NMC analysis as the verification, RMS errors in level temperatures range of about 2-4 K, depending on altitude. Errors for layers of octave extent in pressure are uniformly about 2 K. Theoretical computations show that additional spectrometer channels would improve temperature sensing performance
Rosenkranz, P. W.↗
Satellite observations of snow and ice with an imaging passive microwave spectrometer
The scanning microwave spectrometer (SCAMS) on the Nimbus-6 satellite continuously maps the terrestrial surface with a resolution of about 150 km at 22.235 and 31.400 GHz. SCAMS observes at six angles besides nadir, yielding brightness temperatures which are a function of the distribution and character of various types of snow and ice, including microstructure and subsurface profiles in refractive index, loss (moisture or salinity), and temperature. Spectral signatures exhibiting interesting topographical structure have been observed. To aid in the interpretation of these data, a model was developed to describe the propagation of microwave intensity in a scattering medium characterized by three-dimensional random fluctuations of refractive index in addition to nonrandom variations in permittivity, temperature, and loss. The model combines Maxwell's equations in the Born approximation with radiative-transfer theory; this approach yields the variation of intensity with polarization, direction, and position.
Fisher, A. D.↗
Microwave sensing of atmospheric temperature and humidity from satellites
A 5-channel microwave spectrometer (NEMS) carried on the Nimbus 5 satellite has been taking scans near the 22.235 GHz water vapor resonance and 60 GHz oxygen absorption complex for over 2 years; spectral measurement techniques are described at length. NEMS determinations of atmospheric temperature profiles over 0 to 20 km, and of precipitable water vapor and liquid water over oceans, are compared to relevant radiosonde data and to data reported in analyses by the U.S.A. National Meteorological Center. Some discrepancies between theoretical prediction and empirical evidence are reconciled by examining effects of atmospheric fluctuations. The radiosonde data respond to local fluctuations and do not yield true averages over the large areas sensed remotely by the NEMS.
Staelin, D. H.↗
Passive microwave radiometric observations of the atmosphere
Passive microwave sensing techniques can be used to obtain the temperature of the atmosphere, and to infer liquid water, water vapor and other molecular species over ocean or above the troposphere. The use of satellite-borne passive microwave radiometers is discussed along with the future use of the instrument on Nimbus-G and on the space shuttle.
Cassel, A. L.↗
Remote sensing of atmospheric temperature profiles with the Nimbus 5 microwave spectrometer
The paper discusses the accuracy of atmospheric vertical temperature profile measurements performed by the Nimbus 5 microwave spectrometer and compares results obtained during the first 6 months of its operation with independent ground-truth measurements (coincident radiosonde measurements). The microwave spectrometer can measure temperature profiles averaged over the instrument weighting function (about 10 km) layers with a root-mean-square accuracy of a few tenths of a degree K for measurement integration times of 16 s. Lower tropospheric temperature data from the spectrometer measurements is used in the numerical weather prediction model of the National Meteorological Center.
Waters, J. W.↗
Microwave atmospheric temperature sounding - Effects of clouds on the Nimbus 5 satellite data
The microwave spectrometer on the Nimbus 5 earth observatory satellite has been used to measure thermal radiation in five frequency bands between 22.235 and 58.8 GHz. Clouds were observed to affect less than 0.5% of the temperature profile soundings. Most such effects occur in the intertropical convergence zone and alter the inferred temperature profile by less than a few degrees Centigrade. These effects are evident as cold spots at 53.65 GHz and can be identified by virtue of their small spatial extent, in contrast to smooth variations characteristic of normal atmospheric temperature fields. These effects at 53.65 GHz are sufficiently well correlated with inferred liquid water abundances that they can be used for detecting major storm systems over both land and sea.
Staelin, D. H.↗
Development of a stratospheric and mesospheric microwave temperature sounder experiment
A passive microwave spectrometer system for measuring global atmospheric temperature profiles from 0-75 km altitude was developed and analyzed. The system utilizes 12 channels near the 5 mm wavelength oxygen absorption band and is designed to provide global coverage by scanning perpendicular to the orbital track of a polar orbiting satellite. A significant improvement in the accuracy of theoretical atmospheric microwave transmittance functions was achieved through the development of a first-order approximation to overlapping line theory for the oxygen molecule. This approximation is particularly important in the troposphere and lower stratosphere where pressure-broadening blends nearby lines. Ground-based and aircraft observations of several resonances of stratospheric oxygen generally support the theory. The 23, 25, 29, and 31 atmospheric oxygen lines were measured and the frequencies of several such oxygen lines were measured with improved precision. The polarization and Zeeman splitting of the atmospheric 27 line was also observed.
Staelin, D. H.↗
Passive microwave sensing of the earth
The natural thermal radio radiation emitted by the terrestrial atmosphere and surface can be measured by passive microwave sensors. The receivers and antennas for the required sensing systems are briefly considered along with questions regarding the geophysical information obtainable. Satellite, aircraft, and ground-based observations are discussed. Attention is given to the possibility to monitor continually the evolution of the ice caps in polar regions.
Staelin, D. H.↗
Measurements of snow cover over land with the Nimbus-5 microwave spectrometer
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Kuenzi, K. F.↗