Showing papers on "Radiometer published in 1974"
TL;DR: In this paper, three channels in the 775-to 960-cm−1 (12.9-10.5 μm) region were used to measure the sea surface temperature (SST) over cloud-free oceans.
Abstract: The Nimbus 3 and 4 Iris spectral data in the 11- to 13-μm water vapor window region are analyzed to determine the sea surface temperature (SST). The high spectral resolution data of Iris are averaged over approximately 1-μm-wide intervals to simulate channels of a radiometer to measure the SST. In the present exploratory study, three such channels in the 775- to 960-cm−1 (12.9–10.5 μm) region are utilized to measure the SST over cloud-free oceans. However, two of these channels are sufficient in routine SST determination. The differential absorption properties of water vapor in the two channels enable one to determine the water vapor absorption correction without detailed knowledge of the vertical profiles of temperature and water vapor. The feasibility of determining the SST is demonstrated globally with Nimbus 3 data, where cloud-free areas can be selected with the help of albedo data from the medium resolution infrared radiometer experiment on board the same satellite. The SST derived from this technique agrees with the measurements made by ships to about 1°C.
298 citations
TL;DR: In this paper, a new radiometer is described for remote sounding of the temperature of the stratosphere and mesophere (40-90 km) from a satellite platform, including a cell containing CO 2 gas whose pressure can be modulated at a frequency of ca. 15 Hz.
Abstract: A new radiometer is described for remote sounding of the temperature of the stratosphere and mesophere (40-90 km) from a satellite platform. In order to select radiation emitted from close to the centres of CO$\_{2}$ lines in the 15 $\mu $m infrared band, included in the optical system is a cell containing CO$\_{2}$ gas whose pressure can be modulated at a frequency of ca. 15 Hz. The parts of the emission lines selected can be altered by two methods known as pressure scanning and Doppler scanning. A two-channel instrument for the Nimbus F satellite is described in detail.
75 citations
TL;DR: A laser absorption spectrometer, using an ir laser transmitter and a heterodyne radiometer, can be used from an aircraft or spacecraft to measure altitude profiles of air pollutants and other atmospheric constituents.
Abstract: A laser absorption spectrometer, using an IR laser transmitter and a heterodyne radiometer, can be used from an aircraft or spacecraft to measure altitude profiles of air pollutants and other atmospheric constituents. The technique involves measurement of differential absorption at several wavelengths, using the diffusely reflecting earth's surface to provide a return signal. The pressure broadening of absorption lines allows one to discriminate between high and low altitude absorbers. Application of the technique to measurements of ozone, nitric oxide, and water vapor are presented. CO2 and CO lasers are considered as transmitters. The discussion includes altitude resolution limitations, atmospheric temperature dependence, and frequency stability requirements of the instrument.
74 citations
TL;DR: In this article, a radiometer for the remote measurement of sea surface temperature is described, along with an outline on the design of a unique cryogenically cooled termination used to calibrate the whole radiometer, including antenna.
Abstract: A radiometer for the remote measurement of sea surface temperature is described. Two requirements are necessary for the attainment of an absolute accuracy of 1 or 2 K in molecular temperature. Although the first is inappropriate for discussion here, it is clear that corrections must be developed to account for perturbations caused by surface effects (roughness, foaming, and salinity changes) and for atmospheric effects (absorption and scattering). The second requirement, namely, the development of an instrument capable not only of high relative accuracy (i.e., resolution) but also of high absolute precision, is the subject of this paper. The concepts underlying the design of an instrument capable of an absolute accuracy of a few tenths degrees Kelvin in the measurement of brightness temperature at S band are described. The role of the antenna is discussed and the importance of high ohmic and beam efficiencies is stressed. The hardware itself is fully described, along with an outline on the design of a unique cryogenically cooled termination used to calibrate the whole radiometer, including antenna. Finally, some test results are presented that show that the design goals for the instrument have been closely approached.
51 citations
TL;DR: Temperatures inside a body have been measured by a radiometer at 0.9 to 1.2 GHz with an antenna on the surface of the body as mentioned in this paper, which may have both industrial and medical applications.
Abstract: Temperatures inside a body have been measured by a radiometer at 0.9 to 1.2 GHz with an antenna on the surface of the body. This technique to measure depth temperatures may have both industrial and medical applications.
47 citations
01 Jan 1974
TL;DR: In this article, the authors surveyed various techniques for remotely sensing the earth with instruments operating at microwave frequencies and found that microwave sensors can provide day-night operation and almost an all-weather capability due to higher transmission through clouds at microwave than at visible or infrared wavelengths.
Abstract: Extant techniques for remotely sensing the earth with instruments operating at microwave frequencies are surveyed. Microwave sensors can provide day-night operation and almost an all-weather capability due to higher transmission through clouds at microwave than at visible or infrared wavelengths. Passive (radiometers), active (radars, altimeters, and scatterometers), and composite (passive-active) microwave sensors are in use or planned for such diverse applications as measuring ocean surface dynamics, Ocean salinity, soft moisture content, atmospheric temperature and atmospheric constituents; detecting sea ice, oil slicks, and storm cells; and identifying agricultural crops. These measurements have been taken with sensors located in towers, aircraft, and most recently satellites.
41 citations
01 Oct 1974
TL;DR: In this article, the human body emits thermal signals at millimeter wavelengths which can produce a thermographic image potentially useful for detection of hot spots, and the spatial resolution which can be obtained at a frequency of 45 GHz is in the order of 1.3 cm.
Abstract: Radiometer measurements show that the human body emits thermal signals at millimeter wavelengths which can produce a thermographic image potentially useful for detection of "hot spots." The spatial resolution which can be obtained at a frequency of 45 GHz is in the order of 1.3 cm, and the temperature resolution is 0.1 K.
40 citations
TL;DR: An infrared heterodyne radiometer with a spectral resolution of 0.04 reciprocal centimeters has been used to remotely detect samples of ozone, sulfur dioxide, ammonia, and ethylene at room temperature, and samples of nitric oxide at 390K.
Abstract: An infrared heterodyne radiometer with a spectral resolution of 0.04 reciprocal centimeters has been used to remotely detect samples of ozone, sulfur dioxide, ammonia, and ethylene at room temperature, and samples of nitric oxide at 390K. Each gas was observed in a background of nitrogen or oxygen at atmospheric pressure. Sensitivities to some of these gases are adequate for detection of ambient concentrations as low as a few parts per billion.
36 citations
01 Jan 1974
TL;DR: The Skylab microwave radiometer-scatterometer experiment S-193 was designed to collect simultaneous information on the radiometric emission and the backscatter from the earth from orbital altitude for the first time.
Abstract: The Skylab microwave radiometer-scatterometer experiment S-193 was designed to collect simultaneous information on the radiometric emission and the backscatter from the earth from orbital altitude for the first time. A primary driving force was ascertaining the response from the oceans of both active and passive systems to variations in wind, and the ability of the passive system to aid in calibrating the active system. Numerous overland applications were also explored. Preliminary results of backscatter and emission from sea and atmosphere are shown for hurricane Ava and for two flights across the Gulf of Mexico. The results tend to confirm the most recent theoretical prediction of an approximately square-law relation between scattering coefficient for horizontal polarization and windspeed, with a somewhat smaller dependence for vertical polarization. Overland measurements show that scatterometer signals at 30 deg increase and radiometer signals decrease for terrain that has recently experienced rainfall.
32 citations
TL;DR: In this paper, a simple model for the 15 μm CO2 absorption band is used to find radiometer configurations which give maximum information, and the spectral bandwidths corresponding to these optimum configurations are considerably broader than those specified in the past for radiometers of this type.
Abstract: Infra-red radiometry from an earth satellite is becoming an important technique for the determination of the three-dimensional temperature structure of the atmosphere on a global scale. In this paper a quantitative expression for the information content of the data from a temperature sounding radiometer is derived. A simple model for the 15 μm CO2 absorption band is used to find radiometer configurations which give maximum information. The spectral bandwidths corresponding to these optimum configurations are considerably broader than those specified in the past for radiometers of this type. The technique of selective chopping in which the radiometer contains absorbing cells filled with CO2 is shown to make a significant increase in the information content.
30 citations
TL;DR: In this article, the authors examined the data for the one-year period June 1970 to May 1971 and showed that strong wave activity occurred in the polar regions during winter and spring seasons, the energy being predominantly in the first three wavenumbers.
Abstract: Meterological measurements from a satellite in near-polar orbit cover the entire globe twice per day, providing adequate data for the first time over the poles and oceans. The selective chopper radiometer on Nimbus 4, launched in April 1970, has monitored the three-dimensional atmospheric temperature field continuously for over two years. In this paper we examine the data for the one-year period June 1970 to May 1971. A spectral analysis of the satellite data in time is shown to be equivalent to an analysis of the temperature pattern in both longitude and time. Analyses of the stratospheric temperatures for the four latitudes 60 degrees N, 20 degrees N, 20 degrees S and 60 degrees S demonstrate the presence of both static and travelling waves. The variation of the amplitudes and phases of these waves with latitude, height and season are described. Strong wave activity occurred in the polar regions during winter and spring seasons, the energy being predominantly in the first three wavenumbers.
01 Apr 1974
TL;DR: In this article, the attenuation is assumed to be due only to absorption in the rain, and curves are given for estimating errors at frequencies of 37, 72 and 110 GHz.
Abstract: Scattering by rain is often neglected when evaluations of attenuation are made from aerial-noise temperatures observed by radiometers. Calculations show that values may be significantly low if the attenuation is assumed to be due only to absorption in the rain. Curves are given for estimating errors at frequencies of 37, 72 and 110 GHz.
TL;DR: Results are consonant with those from other laboratory and atmospheric transmittance measurements, and they underline the importance of properly modeling the water-vapor continuum in calculations of atmospheric radiation in the middle infrared.
Abstract: Observations in the spectral window at 11-12 microm, in the carbon dioxide band at 13.3-13.4 microm, and in the water vapor rotation band at 18.7-18.8 microm have been made by the satellite infrared spectrometer and the vertical temperature profile radiometer on the Nimbus 4 and NOAA-2 satellites. Combinations of radiances measured by the separate instruments have been used to infer sea-surface temperatures and mesoscale precipitable water in tropical regions. In each spectral interval, atmospheric transmittances for these analyses were constructed from continuous absorption (of unexplained origin), which is dependent upon the square of the partial pressure of water vapor and about the inverse fifth power of temperature, in addition to absorption by resonance lines. Results are consonant with those from other laboratory and atmospheric transmittance measurements, and they underline the importance of properly modeling the water-vapor continuum in calculations of atmospheric radiation in the middle infrared.
TL;DR: A satellite-borne near infrared radiometer also detected and tracked it as discussed by the authors, which provided additional altitude information and calculated the trajectory using ground-based observations and the satellite data, which was used to estimate the trajectory of the meteor.
Abstract: AN extraordinarily large and brilliant meteor was seen by many observers1 in the western United States and Canada at 2030 UT (1430 local time), on August 10, 1972. A satellite-borne near infrared radiometer also detected and tracked it. W. T. Rogers, a surveyor of Billings, Montana, obtained a ground based sighting which provided additional altitude information. Using his measurement and the satellite data we calculated the trajectory.
Journal Article•
TL;DR: In this paper, the authors analyzed the Nimbus 3 and 4 IRIS spectral data in the 11-13 micron water vapor window region to determine the sea surface temperature (SST).
Abstract: The Nimbus 3 and 4 IRIS spectral data in the 11-13 micron water vapor window region are analyzed to determine the sea surface temperature (SST). The high spectral resolution data of IRIS are averaged over approximately 1 micron wide intervals to simulate channels of a radiometer to measure the SST. Three channels are utilized to measure SST over cloud-free oceans. However, two of these channels are sufficient in routine SST determination. The differential absorption properties of water vapor in the two channels enable one to determine the water vapor absorption correction without detailed knowledge of the vertical profiles of temperature and water vapor. The feasibility of determining the SST is demonstrated globally with Nimbus 3 data where cloud-free areas can be selected with the help of albedo data from the MRIR experiment on board the same satellite.
TL;DR: In this article, the spectral distribution of the radiation is measured using a Michelson interferometer with an optical path difference of ± 10 cm, using a 77°K reference blackbody.
Dissertation•
01 Aug 1974TL;DR: In this article, a dual frequency radiometer, 1.41356 GHz and 10.69 GHz, took measurements at angles between 0 and 50 degrees from an altitude of about fifty feet and the relationship of soil moisture to the permittivity for the soil was obtained in the laboratory.
Abstract: Controlled ground-based passive microwave radiometric measurements on soil moisture were conducted to determine the effects of terrain surface roughness and vegetation on microwave emission. Theoretical predictions were compared with the experimental results and with some recent airborne radiometric measurements. The relationship of soil moisture to the permittivity for the soil was obtained in the laboratory. A dual frequency radiometer, 1.41356 GHz and 10.69 GHz, took measurements at angles between 0 and 50 degrees from an altitude of about fifty feet. Distinct surface roughnesses were studied. With the roughness undisturbed, oats were later planted and vegetated and bare field measurements were compared. The 1.4 GHz radiometer was less affected than the 10.6 GHz radiometer, which under vegetated conditions was incapable of detecting soil moisture. The bare surface theoretical model was inadequate, although the vegetation model appeared to be valid. Moisture parameters to correlate apparent temperature with soil moisture were compared.
TL;DR: A scanning radiometer, using eight interference filters, has been developed at the Smithsonian Radiation Biology Laboratory for monitoring the spectral distribution of daylight.
Abstract: A scanning radiometer, using eight interference filters, has been developed at the Smithsonian Radiation Biology Laboratory for monitoring the spectral distribution of daylight. The unit has been designed to perform in the natural environment with a minimum of maintenance. The range of intensities it can cover is three to four decades, depending on the filtering and detectors.
TL;DR: Field operation has shown the instrument to be fast and reliable for measuring the intensity and polarization of sunlight, which may be of interest for characterizing atmospheric processes or the physical properties of natural surfaces.
Abstract: Photon counting is used in this instrument to obtain high precision in the measurement of the intensity, degree of polarization, and orientation of the plane of polarization of light in the natural environment. The dual-channel configuration, with four interference filters in each channel, provides the possibility of measurements in eight narrow spectral intervals in the wavelength range 0.32–0.90 μm. Operation of the device, including rotation of the polarizing prism, selection of the filters, orientation in azimuth and elevation, and other mechanical processes, is controlled completely by a small electronic computer. The measurements are reduced to the physical quantities of interest on a real-time basis by the computer, which also is used to record the data on magnetic tape and print them out on a high speed printer as desired. Field operation has shown the instrument to be fast and reliable for measuring the intensity and polarization of sunlight, which may be of interest for characterizing atmospheric processes or the physical properties of natural surfaces.
TL;DR: The Nimbus-5 infrared temperature profile radiometer experiment was designed to measure upwelling infrared radiation in appropriate spectral intervals and with sufficient geographical resolution for sounding the atmosphere's temperature distribution down to the earth's surface even under partly cloudy sky conditions.
Abstract: The Nimbus-5 infrared temperature profile radiometer (ITPR) experiment was designed to measure up-welling infrared radiation in appropriate spectral intervals and with sufficient geographical resolution for sounding the atmosphere’s temperature distribution down to the earth’s surface even under partly cloudy sky conditions. A primary scientific goal of the experiment was the specification of the mesoscale features of surface and atmospheric temperature and water vapor that are associated with intense weather systems. In this paper the ITPR instrument is described and some initial spacecraft results are given that demonstrate the success of the experiment in achieving its scientific goals.
TL;DR: In this article, a theoretical analysis of high spectral resolution (<0.01 cm" )) remote sensing of atmospheric gas profiles with a tunable infrared laser heterodyne radiometer at satellite altitudes is presented.
Abstract: A theoretical analysis of high spectral resolution (<0.01 cm" *) remote sensing of atmospheric gas profiles with a tunable infrared laser heterodyne radiometer at satellite altitudes is presented. Numerical simulations are given for retrievals of H2O vapor and CH4 profiles assuming a tunable diode laser as the heterodyne local oscillator. Line-by-line calculations of atmospheric thermal emissions are made in selected frequency intervals and used in sample retrievals of profiles of these gases from 0 to 30 km altitude. The potential of this technique for providing maximum vertical resolution with minimum interference effects is demonstrated. Error analyses using expected radiometer signal-to-noise errors, temperature bias errors, and ground temperature errors indicate that retrieval profiles with less than 20% average error can be obtained.
TL;DR: A very high resolution Radiometer on the NOAA-2 satellite has provided some imagery of the Lesser Antilles showing large areas of relatively calmer water (about 200 km) downwind from the islands.
Abstract: A Very High Resolution Radiometer on the NOAA-2 satellite has provided some imagery of the Lesser Antilles showing large areas of relatively calmer water (about 200 km) downwind from the islands. The relatively calm seas are caused by the disruption of air flow over the islands.
01 Jan 1974
TL;DR: In this article, the minimum detectable temperature of a Josephson junction in video detection of microwave and millimeter-wave radiation has been calculated using the well-known method based on a Fokker-Planck equation.
Abstract: The noise temperature and the minimum detectable temperature of a Josephson junction in video detection of microwave and millimeter-wave radiation has been calculated. We use the well-known method based on a Fokker-Planck equation. The noise temperature can be very close to ambient temperature. Because its predetection bandwidth is very wide, a Josephson-effect radio telescope receiver can have a minimum detectable temperature better than that of a traveling-wave maser.
01 Jul 1974
TL;DR: The Very High Resolution Radiometer (VHRR) was designed for use on the ITOS D series spacecraft as mentioned in this paper, which achieved a 0.47 mile resolution made possible with a mercury-cadmium-telluride detector cooled to approximately 105 K by a passive radiator cooler.
Abstract: A primary sensor used in environmental and earth-resource observation, the Very High Resolution Radiometer (VHRR) was designed for use on the ITOS D series spacecraft. The VHRR provides a 0.47 mile resolution made possible with a mercury-cadmium-telluride detector cooled to approximately 105 K by a passive radiator cooler. The components of this system are described. The optical subsystem of the VHRR consists of a scanning mirror, a Dall-Kirkham telescope, a dichroic beam splitter, relay lenses, spectral filters, and an IR detector. Signal electronics amplify and condition the signals from the infrared and visible light detector. Sync generator electronics provides the necessary time signals. Scan-drive electronics is used for commutation of the motor winding, velocity, and phase control. A table lists the performance parameters of the VHRR.
TL;DR: In this paper, the relationship between cloud thickness and brightness counts was derived for well-developed cumulonimbus clouds, and an estimate of cloud heights corresponding to cloud-top temperature was obtained by using radiosonde data and radar images.
Abstract: Nimbus 4 data (11.5-micron) channel and ATS 3 digitized data were analyzed for three days during April and May 1970. Cloud-top temperature, as measured by the 11.5-micron channel of the satellite radiometer, shows a close negative correlation with cloud brightness measured by the ATS 3 satellite. This is especially true in well-developed cumulonimbus clouds. An estimate of cloud heights corresponding to cloud-top temperature was obtained by using radiosonde data and radar images, and the relationships between the cloud thickness and brightness counts were derived for the cumulonimbus clouds.
01 Apr 1974
TL;DR: In this article, a simple home-made radiation thermometer and directional radiometer is described, which operates in the full range of the long-wave spectrum and is made small by using a white thermocouple as a radiation sensor and a glass shutter as a reference temperature.
Abstract: SUMMARY
A simple home-made radiation thermometer and directional radiometer is described, which operates in the full range of the long-wave spectrum. Sensitivity to short-wave radiation is made small by using a white thermocouple as a radiation sensor and a glass shutter as a reference temperature.
Some sources of error in radiation thermometry with the present and other instruments are discussed.
TL;DR: In this paper, the authors describe the basic aspects of net radiometers and techniques for using them and discuss calibration techniques, basic considerations of data acquisition, and methods of modifying Net Radiometers for a variety of different applications.
Abstract: Publisher Summary This chapter describes some basic aspects of net radiometers and techniques for using them. It discusses calibration techniques, basic considerations of data acquisition, and methods of modifying net radiometers for a variety of different applications. The primary component of a net radiometer is a thermal transducer or thermopile. Two different approaches are used to minimize or equalize convection effects from its upper and lower surfaces; these are to ventilate both surfaces equally or to shield them with transparent domes. The chapter describes the most common method for calibrating net radiometers—that is, the occulting technique or shading technique . Bet radiometers are calibrated for sensitivity to short-wave radiation by simple shading techniques employing standard solarimeters for comparison. Long-wave calibrations are obtained either from special calibration chambers or from a simple flat-plate technique. The chapter indicates that popular polyethylene-shielded net radiometers have comparable sensitivities for both short- and long-wave radiation. Height placement of net radiometers is dependent upon the homogeneity of the underlying surface and its temperature relative to that of ambient air.
01 Jan 1974
TL;DR: In this article, five sets of data are described which relate the Skylab S193 radiometer and scatterometer data and S194 L-band radiometer temperature to soil moisture content of test sites in Texas and Kansas.
Abstract: Five sets of data are described which relate the Skylab S193 radiometer and scatterometer data and S194 L-band radiometer temperature to soil moisture content of test sites in Texas and Kansas. Although the analysis of the S193 data are incomplete, analysis of the L-band radiometer data show that it is highly correlated with the soil moisture content of the surface layers of soil. Various correlations and predictions based on the relationship are described in this paper.
01 Jan 1974
TL;DR: In this paper, the authors used Skylab's 13.9 GHz RADSCAT (radiometer/scatterometer) system to investigate the response of the backscatter and emission response to soil moisture variations.
Abstract: The author has identified the following significant results. Terrain microwave backscatter and emission response to soil moisture variations were investigated using Skylab's 13.9 GHz RADSCAT (radiometer/scatterometer) system. Data acquired on June 5, 1973, over a test site in west-central Texas indicated a fair degree of correlation with composite rainfall. The scan made was cross-track contiguous (CTC) with a pitch of 29.4 deg and no roll effect. Vertical polarization was employed with both radiometer and scatterometer. The composite rainfall was computed according to the flood prediction technique using rainfall data supplied by weather reporting stations.