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Showing papers on "Spectroradiometer published in 1980"


Journal ArticleDOI
TL;DR: In this article, the design and calibration of a rugged, low-cost, portable multiband radiometer is described, the instrument measures simultaneously in four bands, the spectral coverage of each being determined by interchangeable absorption filters.
Abstract: . The design and calibration of a rugged, low-cost, portable multiband radiometer is described. The instrument measures simultaneously in four bands, the spectral coverage of each being determined by interchangeable absorption filters. Simple band-pass type radiometers are seen to be complementary to conventional spectroradiometers for ground data collection in remote sensing. They have the inherent advantages of portability and speed of operation which make them particularly suitable for fieldwork in areas of complex terrain. An example of the practical use of the instrument to measure the spectral reflectance of partially vegetated surfaces in an area of complex terrain in southern Italy is presented. The increased spectral and spatial resolution of second generation sensing systems will make remote sensing of complex areas more feasible and extensive ground-based spectral measurements in such areas are a necessary step to understanding and utilizing such remotely sensed data.

79 citations


Journal ArticleDOI
TL;DR: In this paper, the spectral response of Chalmers and Fincastle soils was measured in the laboratory under controlled moisture equilibria using an Exotech Model 20C spectroradiometer.
Abstract: Spectral responses of two glaciated soils, Chalmers silty clay loam and Fincastle silt loam, formed under prairie grass and forest vegetation, respectively, were measured in the laboratory under controlled moisture equilibria using an Exotech Model 20C spectroradiometer to obtain spectral data in the laboratory under artificial illumination. The same spectroradiometer was used outdoors under solar illumination to obtain spectral response from dry and moistened field plots with and without corn residue cover, representing the two different soils. Results indicate that laboratory-measured spectra of moist soil are directly proportional to the spectral response of that same field-measured moist bare soil over the 0.52 micrometer to 1.75 micrometer wavelength range. The magnitudes of difference in spectral response between identically treated Chalmers and Fincastle soils are greatest in the 0.6 micrometers to 0.8 micrometer transition region between the visible and near infrared, regardless of field condition or laboratory preparation studied.

60 citations


Journal ArticleDOI
TL;DR: In this article, a method for inferring both the size distribution and the complex refractive index of atmospheric particulates from combined bistatic-monostatic lidar and solar radiometer observations is presented.
Abstract: A method is presented for inferring both the size distribution and the complex refractive index of atmospheric particulates from combined bistatic-monostatic lidar and solar radiometer observations. The basic input measurements are spectral optical depths at several visible and near-infrared wavelengths as obtained with a solar radiometer and backscatter and angular scatter coefficients as obtained from a biostatic-monostatic lidar. The spectral optical depth measurements obtained from the radiometer are mathematically inverted to infer a columnar particulate size distribution. Advantage is taken of the fact that the shape of the size distribution obtained by inverting the particulate optical depth is relatively insensitive to the particle refractive index assumed in the inversion. Bistatic-monostatic angular scatter and backscatter lidar data are then processed to extract an optimum value for the particle refractive index subject to the constraint that the shape of the particulate size distribution be the same as that inferred from the solar radiometer data. Specifically, the scattering parameters obtained from the bistatic-monostatic lidar data are compared with corresponding theoretical computations made for various assumed refractive index values. That value which yields best agreement, in a weighted least squares sense, is selected as the optimal refractive index estimate. The results of this procedure applied to a set of simulated measurements as well as to measurements collected on two separate days are presented and discussed.

55 citations


Journal ArticleDOI
TL;DR: A method for calibrating incandescent lamps for spectral irradiance by means of absolute radiometers is described in which a secondary radiometer is calibrated spectrally againstabsolute radiometers and then used in conjunction with a series of filters to calibrate the lamps.
Abstract: A method for calibrating incandescent lamps for spectral irradiance by means of absolute radiometers is described in which a secondary radiometer is calibrated spectrally against absolute radiometers and then used in conjunction with a series of filters to calibrate the lamps. Considering both narrowband and wideband filters, an extensive mathematical error analysis is performed. The use of narrowband filters (20–25-nm halfwidth) is found to be advantageous because very little information is required on the spectral distribution of the lamp being measured. The most serious source of error is a wavelength shift in the measured spectral transmittances of the filters, especially at shorter wavelengths; for example, at 400 nm, a wavelength shift error of 1 nm can cause an error approaching 3%. It is estimated that the accuracy of spectral irradiance measurements made using the method described here will vary between ±1 and ±0.5% from ∼350 to 800 nm. Measurements on 500-W quartz-bromine spectral irradiance standards are described. With such lamps, only four or five narrowband filters are required to cover the spectral range from the near UV to the near IR. The measured and calibration values agreed to ∼ ±0.5% on average with a maximum difference of ∼1%.

28 citations



Journal ArticleDOI
TL;DR: An attempt is made to identify potential sources of error that can occur at the various stages of the measurement process and to suggest ways in which they might be avoided or, at least, kept to a minimum.
Abstract: Systematic errors in spectroradiometry, as in other areas of metrology, are difficult to quantify. An attempt is made here to identify potential sources of error that can occur at the various stages of the measurement process and to suggest ways in which they might be avoided or, at least, kept to a minimum. The special problems that arise in the case of sources, such as discharge lamps, with complex line spectra have led to the development of a new type of spectroradiometer system, based on a continuous scan principle.

18 citations


Journal ArticleDOI
TL;DR: A method to determine the spectral irradiance of a radiation source in the vacuum ultraviolet through the use of recently developed spectral-radiance standards is described.
Abstract: A method to determine the spectral irradiance of a radiation source in the vacuum ultraviolet through the use of recently developed spectral-radiance standards is described. The method has been applied between 138 and 310 nm, and the spectral irradiances of several different light sources have been measured on an absolute scale with estimated uncertainties less than 10%.

18 citations


01 Jan 1980
TL;DR: In this paper, the reflectance signature of four rangeland plants with the LANDSAT satellite multispectral scanner (MSS) and a ground-based spectroradiometer was measured.
Abstract: The accuracy was assessed for an atmospheric correction method that depends on clear water bodies to infer solar and atmospheric parameters for radiative transfer equations by measuring the reflectance signature of four prominent south Texas rangeland plants with the LANDSAT satellite multispectral scanner (MSS) and a ground based spectroradiometer. The rangeland plant reflectances produced by the two sensors were correlated with no significant deviation of the slope from unity or of the intercept from zero. These results indicated that the atmospheric correction produced LANDSAT MSS estimates of rangeland plant reflectances that are as accurate as the ground based spectroradiometer.

16 citations


Proceedings ArticleDOI
26 Mar 1980
TL;DR: An underwater spectroradiometer, designed specifically to measure spectral irradiance in the middle ultraviolet (MUV, 280-340 nm), has been designed, constructed and used to obtain ecologically important data as discussed by the authors.
Abstract: An increase in the incidence of solar ultraviolet radiation upon oceans and lakes, as a consequence of anthropogenic diminishing of the ozone in the stratosphere, might well have a significant effect upon primary producers and other aquatic organisms in these waters. Existing data were inadequate for accurately estimating the penetration of biologically effective dosages of present and potential future levels of UV irradiance into various natural waters. An underwater spectroradiometer, designed specifically to measure spectral irradiance in the middle ultraviolet (MUV, 280-340 nm), has been designed, constructed and used to obtain ecologically important data.

12 citations




Proceedings ArticleDOI
08 Aug 1980
TL;DR: In this article, the use of microprocessor control to switch the output of a sandwich radiation detector together with control of a spctral filter so as to use the most favorable detector-filter combinations is described.
Abstract: Applying a spectral radiometer system to the broadest range of field measurements requires achieving maximum sensitivity and maximum spectral resolution over a broad band of wavelengths. A survey is made of methods of accomplishing this goal by conventional techniques and it is concluded that this requires the use of ponderous methods involving optical-mechanical control of the optical paths of multiple detectors and complex data processing to remove the effects of varying spectral sensitivity. The use of microprocessor control is surveyed and its application to specific radiometric processes is described in detail. Examples include the use of microprocessor control to switch the output of a sandwich radiation detector together with control of a spctral filter so as to use the most favorable detector-filter combinations. Also described is how the microprocessor makes possible automatic gain control, data sample averaging and data normalization to effectively remove the effects of the natural non-uniform spectral response of high-sensitivity detectors. The paper gives examples of the application of the radiometer to a reflectometer, transmissometer and other uses.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Proceedings ArticleDOI
23 Dec 1980
TL;DR: Several of the mechanisms that can alter the spectrum of the test beam are reviewed, measures that can reduce spectral coloration are discussed and spectroradiometer configurations that can be used for in situ characterization of thetest beam are described.
Abstract: Wideband longwave infrared (LWIR) attenuators used in calibration sources can introduce subtle changes in the spectrum of the test beam. As a result, there are probably no sensor calibration sources that have unimpeachable spectral purity at all levels. This paper reviews several of the mechanisms that can alter the spectrum of the test beam, discusses measures that can reduce spectral coloration and describes spectroradiometer configurations that can be used for in situ characterization of the test beam.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.