Showing papers on "Radiometer published in 1984"
TL;DR: The three-satellite ERBE will provide upgraded data on changes in the input and outflow of energy which drives climatic phenomena as mentioned in this paper, which will be flown in the mid-1980s.
Abstract: The three-satellite ERBE will be flown in the mid-1980s and will provide upgraded data on changes in the input and outflow of energy which drives climatic phenomena. The spacecraft will carry radiometers, self-calibration equipment, and be programmed with inversion and averaging algorithms. Radiation will be scanned at 0.2-5 and 5-50 microns. The ACRIM detector, similar to that on the SMM spacecraft, will measure the incoming solar radiation at the 600 km sun-synchronous orbit travelled by the three ERBE spacecraft. Data transmitted to the NASA-Langley Center will be analyzed with algorithms which extract radiant flux data from the measured radiances.
558 citations
TL;DR: In this article, an investigation of the accuracy with which this correction can be made over the north-eastern and tropical Atlantic Ocean using data at 3.7, 11 and 12 μm wavelengths from the Advanced Very High Resolution Radiometer (AVHRR/2) on the NOAA-7 satellite, and the results are used as a test of atmospheric transmittance models.
Abstract: The accuracy with which sea surface temperature (s.s.t.) can be measured using satellite infrared radiometers is limited primarily by uncertainties in the correction for atmospheric effects upon the measured radiance. This paper reports an investigation of the accuracy with which this correction can be made over the north-eastern and tropical Atlantic Ocean using data at 3.7, 11 and 12 μm wavelengths from the Advanced Very High Resolution Radiometer (AVHRR/2) on the NOAA-7 satellite, and the results are used as a test of atmospheric transmittance models. Simulations of atmospheric transmittances based on line-by-line calculations, using published line listings and experimental data on the water vapour ‘continuum’ absorption, provide regression relationships which permit the s.s.t. to be calculated from the brightness temperatures measured in each channel. New algorithms for both the ‘split window’ (11 and 12 μm) and the ‘triple window’ (3.7, 11 and 12 μm) have been derived for a range of airmasses from 1 to 2 to enable the s.s.t. to be retrieved from a 2280 km wide swath centred on the sub-satellite track. To test the validity of the simulations, the s.s.t. values derived from the satellite measurements were compared with near-coincident in situ measurements from oceanographic research ships. The absence of significant bias (˜0.1 K) in the comparison constitutes an important experimental verification of the atmospheric transmittance model used in the simulations, and the r.m.s. difference between ship and satellite values indicates that daytime measurement of s.s.t. using the ‘split-window’ can be made to an accuracy of about ±0.6 K, in the eastern North Atlantic. Some possible sources of this uncertainty are discussed.
182 citations
TL;DR: In this article, an outline of the LIMS temperature determinations from measurements in two channels covering portions of the 15-micrometer band of carbon dioxide is given, where the known sources of error from the radiometer and data reduction are used to estimate the systematic and random errors expected of the results.
Abstract: An outline is given of LIMS temperature determinations (as a function of pressure) from measurements in two channels covering portions of the 15-micrometer band of carbon dioxide. The known sources of error from the radiometer and data reduction are used to estimate the systematic and random errors expected of the results. Observational determinations of the complete end-to-end precision are obtained by computing the standard deviation of six sequential temperature retrievals in regions where the atmosphere is horizontally uniform. This yields values of 0.2 to 0.6 K, in reasonable agreement with the estimates. A correction for horizontal gradients in the atmosphere leads to a large reduction in the differences between the stratospheric temperatures determined on the ascending and descending portions of the orbit. The temperatures agree in the mean with radiosondes and rocketsondes to within 1-2 K in most regions below 1 mbar. Several interesting, previously unseen features included cold regions in the mid-latitude mesosphere and wavelike vertical variations in the tropics.
82 citations
TL;DR: In this paper, a series of experiments were conducted over several years using an aircraft platform to study the relationship between passive microwave data and surface soil moisture and the results indicated that the basic cause and effect relationships between sensor measurements and soil moisture can be extrapolated from theory and small scale tests to larger resolution elements observed by the aircraft.
70 citations
TL;DR: In this paper, the authors showed that at 94 GHz the layers of solid ice present in the dry snow cover throughout the NORSEX area can explain the anomalies at horizontal polarization in the frequency range from 5 to 35 GHz.
Abstract: Observations of microwave emissivities of multiyear sea ice showed anomalies at horizontal polarization in the frequency range from 5 to 35 GHz during the Norwegian Remote Sensing Experiment (NORSEX) [1] in September and October 1979. The effect can be explained by layers of solid ice present in the dry snow cover throughout the NORSEX area. A special experiment made on a typical multiyear floe confirms this explanation. Since the results also indicate that at 94 GHz the layers do not affect the radiation, a dual-polarized radiometer in the 90-GHz window is a promising sea-ice sensor.
66 citations
01 Jul 1984
TL;DR: In this paper, the sensitivity of active and passive microwave remote sensing approaches to soil moisture variations is studied. And the effect of vegetation cover on microwave backscatter and emission is investigated.
Abstract: Four major objectives are proposed: (1) to study the sensitivity of active and passive microwave remote sensing approaches to soil moisture variations; (2) to investigate the effect of vegetation cover on microwave backscatter and emission; (3) to test theoretical models of microwave backscatter and emission from a natural terrain against the observations obtained from SIR-B and aircraft radiometer flights; and (4) to estimate vegetation biomass with airborne visible and infrared sensors.
50 citations
TL;DR: The balloon-borne microwave limb sounder (BMLS) as mentioned in this paper measured atmospheric thermal emission from millimeter wavelength spectral lines to determine vertical profiles of stratospheric species, including ClO, O3, and H2O2.
Abstract: The balloon-borne microwave limb sounder (BMLS) measures atmospheric thermal emission from millimeter wavelength spectral lines to determine vertical profiles of stratospheric species. The instrument flown to date operates at 205 GHz to measure ClO, O3, and H2O2. A 63 GHz radiometer will be added to test the technique for determining tangent point pressure from the MLS experiment on the upper atmosphere research satellite (UARS). Many additional species could also be measured by the BMLS. A radiometer at 270 GHz would provide measurements of HO2, NO2, HNO3, N2O, O-16O-18O-16, and HCN. With this addition, the BMLS can test the current theory of O3 photochemical balance in the upper stratosphere.
48 citations
TL;DR: In this paper, a radiative transfer model was used to calculate the irradiance at the earth's surface for a number of atmospheric scattering and adsorption conditions, and the partial spectrum/total spectrum (P/T) ratio for each radiometer at each atmospheric condition was determined.
47 citations
TL;DR: Coordinated polarization lidar, Ku-band radar and dual-channel microwave radiometer observations of a deep orographic cloud system were collected from a mountain base site in northwestern Colorado as part of the Colorado Orographic Seeding Experiment (COSE) research effort.
Abstract: Coordinated polarization lidar, Ku-band radar and dual-channel microwave radiometer observations of a deep orographic cloud system were collected from a mountain-base site in northwestern Colorado as part of the Colorado Orographic Seeding Experiment (COSE) research effort. The remote sensing observations are presented for three distinct storm stages, corresponding to a pre-frontal altostratus cloud layer, a local orographically-induced cloud development, and a peak in storm activity accompanying the passage of a weak cold front. Supercooled liquid water in the form of thin but often dense liquid layers, and expansive, more weakly mixed-phase cloud regions were usually present even to temperatures approaching −40°C. The liquid water amounts present were often below the detection threshold of the vertically-pointing radiometer measurements, but during one brief interval a liquid water content as high as 0.5 g m−3 may have occurred. The lidar depolarization data also show the presence of a persiste...
44 citations
TL;DR: In this article, the authors used the pre-launch versions of the instrument calibration and geophysical parameter retrieval algorithms for sea surface temperature retrievals on 2 months of Nimbus-7 scanning multichannel microwave radiometer data.
Abstract: Sea-surface temperature retrievals have been tested on 2 months of Nimbus-7 scanning multichannel microwave radiometer data. Using the prelaunch versions of the instrument calibration and geophysical parameter retrieval algorithms the initial results were poor. Improved algorithms produced substantially better results. It appears that at least for the night-Southern Hemisphere portion of the Nimbus-7 orbit, a rms measurement accuracy of 1.45°C has been achieved. Similar tests with wind speed retrievals yield an accuracy of 2.7 m/s rms with no substantial differences between day and night measurements but limited by availability of surface observations to the Northern Hemisphere. Moreover, it appears that the retrieved wind speed is more nearly related to the square of the wind observed at the surface than to the wind itself.
43 citations
TL;DR: The heat capacity mapping radiometer onboard the Heat Capacity Mapping Mission experimental satellite was launched in April 1978 and provided data until July 1980 as discussed by the authors, and the data acquired during the period from May 1978 to May 1979 were systematically utilized for evaluation of sea surface temperature in French oceanic regions (North Sea, English Channel, Celtic Sea, Bay of Biscay, and western Mediterranean Sea).
Abstract: The Heat Capacity Mapping Mission experimental satellite was launched in April 1978 and provided data until July 1980. Although the basic mission objective was the measurement of diurnal temperature variations of the earth's surface for soil and geology applications, the characteristics of the heat capacity mapping radiometer onboard the satellite (temperature sensitivity of 0.3°C, instantaneous field of view of 0.5 km) also recommended it for use in oceanographic studies. The data acquired during the period from May 1978 to May 1979 were systematically utilized for evaluation of sea surface temperature in French oceanic regions (North Sea, English Channel, Celtic Sea, Bay of Biscay, and western Mediterranean Sea) and for study of sea surface temperature-related dynamic phenomena. Comparisons were made of the radiometric performance of the heat capacity mapping radiometer to that of the very high resolution radiometer and the advanced very high resolution radiometer onboard meteorological satellites. They demonstrate the decisive gain in quality of the heat capacity mapping radiometer over the very high resolution radiometer and the similarly improved quality of the heat capacity mapping radiometer and advanced very high resolution radiometer for the observation of mesoscale sea surface temperature features. The utilization of available photographic products proved very suitable, since they had been geometrically corrected and enhanced in the sea surface temperature range, consequently avoiding many of those cases requiring involved computer treatment. On the basis of the interpretation of photographic products, conclusions have been drawn regarding several oceanic phenomena: (1) The thermal effluent of the Rhine-Meuse system is affected by the residual tidal current of the North Sea. The extent of the offshore diffusion of the effluent is influenced by winds from the northeast and west which, respectively, retard or accelerate the residual current; (2) images exhibiting cold water along the edge of the continental shelf strongly support the hypothesis of a mixing process due to internal waves generated by the action of tidal currents at the edge of the shelf; (3) large-scale eddy structures detected during the summer in the region of the Mediterranean Sea around 6°E and 38°N may be linked to a phenomenon of barotropic-baroclinic instability; (4) significant diurnal heating of the surface layer (several degrees Celsius) observed in the Mediterranean Sea is related to the presence of weak winds, leading one to interpret with caution the daytime sea surface temperature satellite observations made during the summer period.
TL;DR: Ozone mixing ratios at pressure levels near 2 mbar were analyzed for the purpose of estimating the average response of the upper stratospheric ozone to solar UV variability on the time scale of the solar rotation period as mentioned in this paper.
Abstract: Ozone mixing ratios at pressure levels near 2 mbar are analyzed for the purpose of estimating the average response of the upper stratospheric ozone to solar UV variability on the time scale of the solar rotation period. The data were obtained from observations made with the Nimbus 4 backscattering UV radiometer in 13 latitude zones between 65 degrees N and 65 degrees S. The anaysis showed that temporal variations are negatively correlated with changes in zonally averaged equivalent temperature measured simultaneously by Nimbus 4 radiometer. A linear regression analysis is performed in order to obtain estimates of the average percent change of ozone at low latitudes, on the considered time scale for given changes in 10.7-cm flux, and in the UV flux model developed by Lean et al. (1982). Reproductions of the ozone profiles are provided.
01 Oct 1984
TL;DR: In this paper, a new and very practical method is introduced for the characterization of radiometer noise and stability, which consists of the measurement of the "Allan-variance" well known for the characterisation of the stability of frequency standards.
Abstract: For the characterization of radiometer noise and stability a new and very practical method is introduced. It consists of the measurement of the "Allan-variance" well known for the characterization of the stability of frequency standards. The plot of the Allan variance versus integration time allows one to determine the different types of fluctuations of the radio-meter output signal. In particular, the best range of integration time for optimum use of the system can accurately be evaluated. Theoretical considerations and experimental results are presented.
TL;DR: Microwave systems combining microwave heating generators with radiometers with microwave radiometers used for two years in hyperthermia therapy and first clinical results are detailed.
Abstract: Microwave systems combining microwave heating generators (434, 915 or 2450 MHz) with microwave radiometers (1-2 GHz or 2-4 GHz) have been used for two years in hyperthermia therapy Technical aspects (generator, radiometer, applicator), experiments and first clinical results are detailed
TL;DR: In this paper, an approach is presented whereby visible/near infrared data are used to develop corrections in the microwave soil moisture signal to account for vegetation effects, and effective estimation of soil moisture in the presence of vegetation can be made with L-band microwave radiometers and visible/infrared sensors when the PVI is less than 4.3.
Abstract: Investigations concerning microwave techniques for remote estimation of soil moisture have shown Increased interest in the study of vegetation effects on the estimates of soil moisture. This paper addresses only combinations of passive microwave and visible/infrared systems. An approach is presented whereby visible/near infrared data are used to develop corrections in the microwave soil moisture signal to account for vegetation effects. Microwave brightness temperature measurements at near nadir took angles were made with 1.4- and 5-GHz systems. Visible/infrared data were collected with the NASA NS001 Thematic Mapper Simulator and the M2S imager at the time of the microwave observations. The visible/infrared data were used to calculate Perpendicular Vegetation Index (PVI) which was then related to the change in sensitivity of the microwave measurement to surface soil moisture. It was found that effective estimation of soil moisture in the presence of vegetation can be made with L-band microwave radiometers and visible/infrared sensors when the PVI is less than 4.3. If implemented from a space platform, this technique can provide a pragmatic means of estimating moisture over many agricultural areas without the expensive necessity of collecting ground data.
TL;DR: In this paper, a system consisting of dual microwave radiometers, one operating at 20.7 GHz and the other at 31.4 GHz, was developed for estimating atmospheric water vapor path delay.
Abstract: To support very long baseline interferometric experiments, a system has been developed for estimating atmospheric water vapor path delay. The system consists of dual microwave radiometers, one operating at 20.7 GHz and the other at 31.4 GHz. The measured atmospheric brightness temperatures at these two frequencies yield the estimate of the precipitable water present in both vapor and droplets. To determine the accuracy of the system, a series of observations were undertaken, comparing the outputs of two water vapor radiometers with the phase variation observed with two connected elements of the very large array (VLA). The results show that: (1) water vapor fluctuations dominate the residual VLA phase and (2) the microwave radiometers can measure and correct these effects. The rms phase error after correction is typically 15 deg at a wavelength of 6 cm, corresponding to an uncertainty in the path delay of 0.25 cm. The residual uncertainty is consistent with the stability of the microwave radiometer but is still considerably larger than the stability of the VLA. The technique is less successful under conditions of heavy cloud.
TL;DR: Calibration problems which include the influence of instrumental scatter on solar aureole measurements and the effects of optical instability on Langley plot data have been investigated.
Abstract: A small field-of-view microprocessor-controlled radiometer has been developed for measuring the spectral radiance in the solar aureole region and on the solar disk itself. Calibration problems which include the influence of instrumental scatter on solar aureole measurements and the effects of optical instability on Langley plot data have been investigated. A simple technique for measuring the instrumental scatter component is presented and comparisons are made with actual aureole data. Simultaneous measurements of NO2 columnar abundance were performed in order to assess the effect of variable NO2 optical depth on Langley plot calibration constants in the blue region of the spectrum. The aureole radiance at a constant angular distance from the sun is used to infer optical stability as affected by aerosol content variation. The latter two studies were felt to be particularly relevant given that our measurements were made in the vicinity of a large urban center.
TL;DR: In this article, the absolute radiometer on Spacelab 1 was used to obtain solar irradiance observations from space and a provisional value was obtained for the mean solar constant during the observation period (6 to 8 December 1983).
Abstract: The absolute radiometer on Spacelab 1 was used to obtain solar irradiance observations from space. A number of effects must be taken into account in the data reduction. A provisional value was obtained for the mean solar constant during the observation period (6 to 8 December 1983).
TL;DR: In this article, the authors describe the measuring task, the engineering constraints, and the resulting design of the stratospheric and mesospheric sounder, and their calibration system and its performance are discussed in more detail.
Abstract: The measuring task, the engineering constraints, and the resulting design of the stratospheric and mesospheric sounder are described in broad terms. The calibration system and its performance are discussed in more detail. One significant side effect in the design and its impact on the fields of view is also discussed. The major lessons for future pressure modulator radiometer designs are summarized.
TL;DR: In this article, an attempt has been made to relate hand-held radiometer measurements, and airborne multispectral scanner readings, with both different wheat stand densities and grain yield.
Abstract: An attempt has been made to relate hand-held radiometer measurements, and airborne multispectral scanner readings, with both different wheat stand densities and grain yield. Aircraft overflights were conducted during the tillering, stem extension and heading period stages of growth, while hand-held radiometer readings were taken throughout the growing season. The near-IR/red ratio was used in the analysis, which indicated that both the aircraft and the ground measurements made possible a differentiation and evaluation of wheat stand densities at an early enough growth stage to serve as the basis of management decisions. The aircraft data also corroborated the hand-held radiometer measurements with respect to yield prediction. Winterkill was readily evaluated.
TL;DR: In this article, the authors evaluate the response of a 21 cm radiometer, measuring the radiation emitted by a bare soil, to varying accumulations of rain and show that correlations between the decrease in emissivity after a rain storm and the total accumulation depend strongly on the physical characteristics of the soil which affect its capacity to hold water.
Abstract: This simulation study evaluates the response of a 21-cm radiometer, measuring the radiation emitted by a bare soil, to varying accumulations of rain. We show that correlations between the decrease in emissivity after a rain storm and the total accumulation depend strongly on the physical characteristics of the soil which affect its capacity to hold water. These are primarily soil texture and pre-rain soil moisture. A method is also discussed which would use the numerical models with remotely sensed microwave brightness and surface physical temperatures, along with conventional weather data, to estimate the total accumulation.
TL;DR: In this paper, the use of satellite microwave data to determine snowpack properties is investigated through calculation of theoretical microwave brightness temperatures and comparison of the computed brightness temperatures with actual satellite microwave measurements.
01 Oct 1984
01 Jan 1984
TL;DR: In this article, the soil moisture was measured by truck mounted microwave radiometers at the frequencies of 1.4 GHz, 5 GHz, and 10.7 GHz at two different test sites.
Abstract: Soil moisture was measured by truck mounted microwave radiometers at the frequencies of 1.4 GHz, 5 GHz, and 10.7 GHz. The soil textures in the two test sites were different so that the soil type effect of microwave radiometric response could be studied. Several fields in each test site were prepared with different surface roughnesses and vegetation covers. Ground truth on the soil moisture, temperature, and the biomass of the vegetation was acquired in support of the microwave radiometric measurements. Soil bulk density for each of the fields in both test sites was sampled. The soils in both sites were measured mechanically and chemically. A tabulation of the measured data is presented and the sensors and operational problems associated with the measurements are discussed.
TL;DR: In this article, a comparison of HCMM infrared temperatures with in situ data from the Mississippi River in the St. Louis, Missouri, area and with sea surface temperatures collected in the Nantucket Shoals and Gulf of Mexico regions is presented.
TL;DR: In this paper, rotationally split p-, g-and f-modes have been identified in the temporal power spectrum of Bos and Hill's (1983) limb-darkening data, and two rotational curves have been deduced which imply a solar gravitational quadrupole moment sufficiently large to preclude agreement between general relativity and planetary motion observations.
Abstract: Individual 5-min p-mode oscillations of spherical harmonic degree 0-2 and radial order 16-26 are revealed by the Solar Maximum Mission Spacecraft's Active Cavity Radiometer Irradiance Monitor power spectra for total solar irradiance flux variation. Rotationally split p-, g- and f-modes have been identified in the temporal power spectrum of Bos and Hill's (1983) limb-darkening data, and from these splittings, two rotational curves have been deduced which imply a solar gravitational quadrupole moment sufficiently large to preclude agreement between general relativity and planetary motion observations.
01 Jan 1984
TL;DR: The Along Track Scanning Radiometer (ATSR) as mentioned in this paper was used to provide accurate measurements of sea surface temperature using a multi-angle, multichannel technique to overcome the effects of the clear atmopshere.
Abstract: Factors determining the accuracy with which the sea surface temperature can be measured from space using infrared radiometers are discussed. These include the clear atmosphere radiative effects, contamination of the signal by clouds in the field of view, and sun glitter at the 3.7 μm ‘atmospheric window’. The effects of near surface vertical temperature gradients caused by surface heat loss (the skin effect) and by solar heating (the diurnal thermocline) are also discussed. A review of present measurement capabilities is made and a brief description is given of the Along Track Scanning Radiometer (ATSR), which will fly on the European satellite ERS-1 to provide accurate measurements of sea surface temperature using a multi-angle, multichannel technique to overcome the effects of the clear atmopshere.
01 Nov 1984
TL;DR: The PARABOLA as discussed by the authors is a collapsable support boom, which is self contained and easily transportable to remote sites to enable the acquisition of radiance data for almost the complete (4 pi) sky and ground-looking hemispheres in only 11 seconds.
Abstract: A unique field instrument, called the PARABOLA, a collapsable support boom, which is self contained and easily transportable to remote sites to enable the acquisition of radiance data for almost the complete (4 pi) sky and ground-looking hemispheres in only 11 seconds was designed. The PARABOLA samples in 15 deg instantaneous field of view sectors in three narrow bandpass spectral channels simultaneously. Field measurement on a variety of earth surface cover types using a truck boom, a specially designed pickup truck mounting system, and a hot air balloon were studied. The PARABOLA instrument has potential for climatological and other studies which require characterization of the distribution of diffuse solar radiation within the sky hemisphere.
TL;DR: In this article, the authors measured the long-wavelength spectrum of the cosmic background radiation at three different wavelengths (0.33, 0.9, 3.0, 6.3, and 12.0 cm) with a radiometer tunable from 1.7 to 15 cm.