Showing papers on "Spectroradiometer published in 2003"
TL;DR: The Puerto Rico Dust Experiment (PRIDE) as mentioned in this paper was the first field experiment to allow direct comparison of aerosol retrievals from the Moderate Imaging Spectroradiometer (MODIS) with Sun photometer and in situ measurements.
Abstract: [1] The Puerto Rico Dust Experiment (PRIDE) took place in Roosevelt Roads, Puerto Rico from 26 June to 24 July 2000 to study the radiative and physical properties of African dust aerosol transported into the region. PRIDE had the unique distinction of being the first major field experiment to allow direct comparison of aerosol retrievals from the Moderate Imaging Spectroradiometer (MODIS) with Sun photometer and in situ aerosol measurements. Over the ocean the MODIS algorithm retrieves aerosol optical depth (AOD) as well as information about the aerosols' size distribution. During PRIDE, AODs derived by MODIS in the red wavelengths (0.66 μm) compare closely with Sun photometers. However, MODIS-derived AODs are too large in the blue and green wavelengths (0.47 and 0.55 μm) and too small in the near infrared (0.87 μm). This error in AOD spectral dependence results in retrieved particle size distributions that are small compared to in situ measurements and smaller still when compared to Sun photometer sky radiance inversions. The differences in size distributions may be, in part, associated with MODIS' simplification of dust as spherical particles. Analysis of this PRIDE data set is a first step toward derivation of realistic models for future MODIS retrievals.
192 citations
TL;DR: In this article, the authors evaluated the quality of the operational albedo retrievals in two ways: (1) by examining the algorithm performance using the product quality assurance (QA) fields and (2) by comparing retrieved albedos with those observed at ground stations and by other satellite instruments.
Abstract: [1] The first consistent year (November 2000 to November 2001) of global albedo product was produced at 1-km resolution every 16 days from the observations of the Moderate-Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA's Terra spacecraft. We evaluated the quality of the operational albedo retrievals in two ways: (1) by examining the algorithm performance using the product quality assurance (QA) fields (this paper) and (2) by comparing retrieved albedos with those observed at ground stations and by other satellite instruments (in a companion paper). The internal diagnostics of the retrieval algorithm adequately reflect the goodness of the model fit and the random noise amplification in the retrieved albedo. Global QA statistics show that the RossThick-LiSparse-Reciprocal model fits the atmospherically corrected surface reflectances very well, and the random noise amplification factors for white sky albedo and reflectance are generally less than 1.0. Cloud obscuration is the main reason for the activation of the backup magnitude retrieval algorithm. Over the 60°S to 60°N latitude band, 50% of the land pixels acquire more than six clear looks during 14–29 September 2001, and only 5% of these pixels are inverted with the backup algorithm. The latitude dependence and temporal distribution of the QA fields further demonstrate that the retrieval status mainly follows the pattern of angular sampling determined by cloud climatology and the instrument/orbit characteristics. A case study over the west coast of the United States shows that white sky shortwave albedos retrieved from magnitude inversions agree on average with those from full inversions to within 0.033 in reflectance units and have a slightly lower bias ranging from 0.014 to 0.023. We also explored the effect of residual cloud and aerosol contamination in the atmospherically corrected surface reflectance inputs in another case study over southern Africa. The quality assurance procedure of the operational MODIS bidirectional reflectance distribution function and albedo algorithm compensates for some of these residual effects and improves the albedo retrieval results by an order of 0.005 (10%) in the visible for more than 12% of pixels.
173 citations
TL;DR: A calibration experiment was orchestrated on February 7, 2001 at the Salar de Arizaro, Argentina to assess the on-orbit radiometric and spectral calibration of Hyperion and found the Hyperion cross-track response was shown to be uniform.
Abstract: A calibration experiment was orchestrated on February 7, 2001 at the Salar de Arizaro, Argentina to assess the on-orbit radiometric and spectral calibration of Hyperion. At this high-altitude homogeneous dry salt lakebed, Hyperion, Airborne Visible/Infrared Imaging Spectroradiometer (AVIRIS) and in situ measurements were acquired. At a designated calibration target on Salar de Arizaro, the radiance spectra measured by Hyperion and AVIRIS were compared. In the spectral range from 430-900 nm [visible near-infrared (VNIR)], the ratio of Hyperion over AVIRIS was 0.89, and in the 900-2390-nm [shortwave infrared (SWIR)] spectral range the ratio was 0.79. A comparison of the Hyperion radiance spectrum with a radiative-transfer-code-predicted spectrum for the calibration target showed similar results. These results in conjunction with prelaunch laboratory measurements, on-orbit lunar measurements, other on-orbit calibration experiment results, as well as comparison with Landsat-7, lead to an update of Hyperion radiometric calibration in December 2001. The compromise update was to increase the Hyperion radiometric calibration coefficients by 8% in the VNIR and 18% in the SWIR spectrometers. In addition to radiometric accuracy, the on-orbit radiometric precision of Hyperion was assessed at Salar de Arizaro. Noise-equivalent delta radiance was calculated from Hyperion dark signal data and found to be five to ten times higher in comparison to AVIRIS. Also, from a homogeneous portion of Salar de Arizaro the Hyperion SNR was estimated at 140 in the VNIR and 60 in the 2200-nm region of the SWIR spectral range. Cross-track radiometric response was assessed with the AVIRIS dataset that spanned the full Hyperion swath. Within the accuracy of the registration of the datasets, the Hyperion cross-track response was shown to be uniform. Hyperion spectral calibration was assessed with a spectral fitting algorithm using the high spectral resolution radiative transfer modeled spectra for Salar de Arizaro.
170 citations
TL;DR: In this article, a satellite-based multispectral passive radiometer technique for daytime enhancement of airborne dust over water and land has been developed, which combines color information from multiple visible channels with near and far infrared measurements, provides an improved ability to distinguish areas of dust from water/ice clouds and bright desert backgrounds in enhanced false-color imagery.
Abstract: [1] A new satellite-based multispectral passive radiometer technique for daytime enhancement of airborne dust over water and land has been developed. The algorithm, which combines color information from multiple visible channels with near and far infrared measurements, provides an improved ability to distinguish areas of dust from water/ice clouds and bright desert backgrounds in enhanced false-color imagery. While generally applicable to any sensor possessing the requisite spectral information, the method is demonstrated here using high spatial and spectral resolution digital data from the Moderate Imaging Spectroradiometer (MODIS) instruments carried aboard Earth Observing System (EOS) Terra and Aqua polar orbiter platforms.
164 citations
TL;DR: In this article, the authors defined the goal of scaling as the process by which it was established that LAI values derived from coarse resolution sensor data equal the arithmetic average of values derived independently from fine resolution data.
127 citations
TL;DR: In this paper, the estimation of soil moisture from reflectance measurements in the solar spectral domain (400-2500 nm) was investigated using a high spectral resolution spectroradiometer.
Abstract: The estimation of soil moisture from reflectance measurements in the solar spectral domain (400-2500 nm) was investigated. For this purpose, 18 soils representing a large range of permanent characteristics was considered. Reflectance data were measured in the laboratory during the soil drying process with a high spectral resolution spectroradiometer. Five approaches were compared. The first one was based on single-band reflectance and on the normalization of reflectance data by the reflectance of the corresponding soil under dry conditions. The second and the third approaches were based on either reflectance derivatives or absorbance derivatives. The fourth and fifth approaches were based on the differences of reflectance and absorbance observed in two non-consecutive bands. In the first step, the relationships were calibrated over half the dataset (nine soils) with emphasis on the selection of the most pertinent spectral bands. Results showed that, for the first approach, the bands corresponding to the h...
125 citations
TL;DR: The Digital Airborne Imaging Spectrometer Experiment (DAISEX) was carried out for the European Space Agency (ESA) in order to develop the potential of spaceborne imaging spectroscopy for a range of different scientific applications as discussed by the authors.
Abstract: [1] The Digital Airborne Imaging Spectrometer Experiment (DAISEX) was carried out for the European Space Agency (ESA) in order to develop the potential of spaceborne imaging spectroscopy for a range of different scientific applications. DAISEX involved simultaneous data acquisitions using different airborne imaging spectrometers over test sites in southeast Spain (Barrax) and the Upper Rhine valley (Colmar, France, and Hartheim, Germany). This paper presents the results corresponding to the columnintegrated aerosol optical properties from ground-based spectroradiometer measurements over the Barrax area during the DAISEX campaign days in the years 1998, 1999, and 2000. The instruments used for spectral irradiance measurements were two Licor 1800 and one Optronic OL-754 spectroradiometers. The analysis of the spectral aerosol optical depth in the visible range shows in all cases the predominance of the coarse-particle mode over the fine-particle mode. The analysis of the back trajectories of the air masses indicates a predominance of marine-type aerosols in the lower atmospheric layers in all cases. Overall, the results obtained show that during the DAISEX there was a combination of maritime aerosols with smaller continental aerosols. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0394 Atmospheric Composition and Structure: Instruments and techniques; 3360 Meteorology and Atmospheric Dynamics: Remote sensing; 4801 Oceanography: Biological and Chemical: Aerosols (0305); KEYWORDS: atmospheric composition and structure, instruments and techniques, remote sensing
59 citations
27 Aug 2003
TL;DR: In this article, the performance of a new spectroradiometer instrument based on a diode array technique during its first field deployment at the International Modeling and Measurement Intercomparison (IPMMI) has been evaluated.
Abstract: [1] The performance of a new spectroradiometer instrument based on a diode array technique during its first field deployment at the International Modeling and Measurement Intercomparison (IPMMI) has been evaluated. The instrument is a single-monochromator diode array spectroradiometer that was used to measure both actinic flux and derived values of j(O1D) and j(NO2). Spectra may be collected over the wavelength region λ = 280–450 nm at variable integration times (typically 1 s for normal operation), and data may be converted to actinic flux/photolysis frequencies using National Institute of Standards and Technology traceable calibration standards. The relative accuracy of these measurements is compared to photolysis frequencies derived using similar and contrasting experimental techniques. The instrument performed adequately in the comparison, but the problem of poor stray light rejection in the single monochromator has the potential to propagate significant errors in the derived photolysis frequencies. A full error analysis together with instrument characterization has been performed and is reported. The feasibility of using such instruments in the field for the measurement of atmospheric photolysis frequencies is also discussed.
59 citations
TL;DR: The results of the radiometric measurement comparison presented here supplement the results of previous measurement comparisons on the integrating sphere sources used to calibrate the Multi-angle Imaging SpectroRadiometer (MISR) at NASA’s Jet Propulsion Laboratory (JPL), Pasadena, CA and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) at NEC Corporation, Yokohama, Japan.
Abstract: As part of a continuing effort to validate the radiometric scales assigned to integrating sphere sources used in the calibration of Earth Observing System (EOS) instruments, a radiometric measurement comparison was held in May 1998 at Raytheon/Santa Barbara Remote Sensing (SBRS). This comparison was conducted in support of the calibration of the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Landsat 7 Enhanced Thematic Mapper Plus (ETM+) instruments. The radiometric scale assigned to the Spherical Integrating Source (SIS100) by SBRS was validated through a comparison with radiometric measurements made by a number of stable, well-characterized transfer radiometers from the National Institute of Standards and Technology (NIST), the National Aeronautics and Space Administration's Goddard Space Flight Center (NASA's GSFC), and the University of Arizona Optical Sciences Center (UA). The measured radiances from the radiometers differed by ±3 % in the visible to near infrared when compared to the SBRS calibration of the sphere, and the overall agreement was within the combined uncertainties of the individual measurements. In general, the transfer radiometers gave higher values than the SBRS calibration in the near infrared and lower values in the blue. The measurements of the radiometers differed by ±4 % from 800 nm to 1800 nm compared to the SBRS calibration of the sphere, and the overall agreement was within the combined uncertainties of the individual measurements for wavelengths less than 2200 nm. The results of the radiometric measurement comparison presented here supplement the results of previous measurement comparisons on the integrating sphere sources used to calibrate the Multi-angle Imaging SpectroRadiometer (MISR) at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) at NEC Corporation, Yokohama, Japan.
41 citations
TL;DR: In this paper, the performance of the on board calibrator for bands 1 (, 0.66 µm), 2 (, 0.86 µm) and 4 ( - 0.55 µm).
Abstract: The performance of the on board calibrator for bands 1 ( , 0.66 µm), 2 ( , 0.86 µm) and 4 ( , 0.55 µm) of the Moderate-Resolution Imaging Spectroradiometer (MODIS Terra) has been evaluated by comparison of the top-of-atmosphere (TOA) albedos measured in the three bands over a six-day period with a three-year record of TOA albedos measured in the 0.56, 0.66 and 0.86 µm channels of the Along-Track Scanning Radiometer-2 (ATSR-2). The albedo measurements were made over two radiometrically stable sites located in the Libyan desert (22°0'N, 28°30'E), Sudan, and in the Sonoran desert (32°0'N, 114°6'W), Mexico. MODIS Terra albedos are within - 2.5 per cent of those measured in the corresponding channels of ATSR-2. Analysis of the measurements, and of model-derived albedos in the three channels (bands) of the two instruments, indicates that the MODIS Terra on board calibrator for bands 1, 2 and 4 is functioning as expected, and that either of the two instruments can be used to monitor the in-orbit performance of t...
29 citations
09 Apr 2003
TL;DR: In this paper, data from the Terra MODIS (MODerate-resolution Imaging Spectroradiometer) taken at 3.7, 8.5, 10.8, 12.0 micron are used to simultaneously derive the skin temperature and the surface emissivities at the same wavelengths.
Abstract: Surface emissivity is essential for many remote sensing applications including the retrieval of the surface skin temperature from satellite-based infrared measurements, determining thresholds for cloud detection and for estimating the emission of longwave radiation from the surface, an important component of the energy budget of the surface-atmosphere interface. In this paper, data from the Terra MODIS (MODerate-resolution Imaging Spectroradiometer) taken at 3.7, 8.5, 10.8, 12.0 micron are used to simultaneously derive the skin temperature and the surface emissivities at the same wavelengths. The methodology uses separate measurements of the clear-sky temperatures that are determined by the CERES (Clouds and Earth's Radiant Energy System) scene classification in each channel during the daytime and at night. The relationships between the various channels at night are used during the day when solar reflectance affects the 3.7 micron data. A set of simultaneous equations is then solved to derive the emissivities. Global results are derived from MODIS. Numerical weather analyses are used to provide soundings for correcting the observed radiances for atmospheric absorption. These results are verified and will be available for remote sensing applications.
TL;DR: An experimental comparison of spectral aerosol optical depth τa,λ derived from measurements by two spectral radiometers [a LI-COR, Inc., LI-1800 spectroradiometer and a Centre Suisse d'Electronique et de Microtechnique (CSEM) SPM2000 sun photometer] and a broadband field pyrheliometer has been made as mentioned in this paper.
Abstract: An experimental comparison of spectral aerosol optical depth τa,λ derived from measurements by two spectral radiometers [a LI-COR, Inc., LI-1800 spectroradiometer and a Centre Suisse d'Electronique et de Microtechnique (CSEM) SPM2000 sun photometer] and a broadband field pyrheliometer has been made. The study was limited to three wavelengths (368, 500, and 778 nm), using operational calibration and optical depth calculation procedures. For measurements taken on 32 days spread over 1 yr, the rms difference in τa,λ derived from the two spectral radiometers was less than 0.01 at 500 and 778 nm. For wavelengths shorter than 500 nm and longer than 950 nm, the performance of the LI-1800 in its current configuration did not permit accurate determinations of τa,λ. Estimates of spectral aerosol optical depth from broadband pyrheliometer measurements using two models of the Angstrom turbidity coefficient were examined. For the broadband method that was closest to the sun photometer results, the mean (rms) ...
TL;DR: In this article, the results of the analysis of the spectral, global, and direct solar irradiance measurements in the visible range (400-700 nm) were made in the framework of the first Iberian UV-visible (VIS) instruments intercomparison.
Abstract: This paper presents the results of the analysis of the spectral, global, and direct solar irradiance measurements in the visible range (400–700 nm) that were made in the framework of the first Iberian UV–visible (VIS) instruments intercomparison. The instruments used in this spectral range were four spectroradiometers: three Licor 1800s equipped with different receiver optics and one Optronic 754. For the direct solar irradiance measurements the spectroradiometers were equipped with collimators with different fields of view. Parallel studies have been carried out with the data given by the spectroradiometers with their original calibration file and with the same data that is corrected, following in situ calibration of the instruments using a laboratory reference lamp. To compare the series of spectral data the relative values of mean absolute deviation (MAD) and root-mean-square deviation (rmsd) have been used. The results obtained from the measurements of global irradiance show that the Licor 18...
01 Jul 2003
TL;DR: The QASUME project as mentioned in this paper developed and tested a transportable unit for providing quality assurance to UV spectroradiometric measurements conducted in Europe, where the measurements were performed at the home sites of the instruments, thus avoiding the risk of transporting instruments to participate in intercomparison campaigns.
Abstract: QASUME is a European Commission funded project that aims to develop and test a transportable unit for providing quality assurance to UV spectroradiometric measurements conducted in Europe. The comparisons will be performed at the home sites of the instruments, thus avoiding the risk of transporting instruments to participate in intercomparison campaigns. Spectral measurements obtained at each of the stations will be compared, following detailed and objective comparison protocols, against collocated measurements performed by a thoroughly tested and validated travelling unit. The transportable unit comprises a spectroradiometer, its calibrator with a set of calibration lamps traceable to the sources of different Standards Laboratories, and devices for determining the slit function and the angular response of the local spectroradiometers. The unit will be transported by road to about 25 UV stations over a period of about two years. The spectroradiometer of the transportable unit is compared in an intercomparison campaign with six instruments to establish a relation, which would then be used as a reference for its calibration over the period of its regular operation at the European stations. Different weather patterns (from clear skies to heavy rain) were present during the campaign, allowing the performance of the spectroradiometers to be evaluated under unfavourable conditions (as may be experienced at home sites) as well as the more desirable dry conditions. Measurements in the laboratory revealed that the calibration standards of the spectroradiometers differ by up to 10%. The evaluation is completed through comparisons with the same six instruments at their homes sites.
20 Jan 2003
TL;DR: An algorithm is proposed for the spectral and colorimetric characterization of digital still cameras (DSC) which allows to use them as tele-colorimeters with CIE-XYZ color output, in cd/m2, which indicates that the digital image capture device, in raw performance, lightens and desaturates the colors.
Abstract: An algorithm is proposed for the spectral and colorimetric characterization of digital still cameras (DSC) which allows them to be used as tele-colorimeters with CIE-XYZ color output, in cd/m2. The spectral characterization consists in the calculation of the color-matching functions from the previously measured spectral sensitivities. The colorimetric characterization consists in trans- forming the raw RGB digital data into absolute tristimulus values CIE-XYZ (in cd/m2) under variable and unknown spectroradiometric conditions. Thus, in the first stage, a gray balance was applied over the raw RGB digital data to convert them into RGB relative colorimetric values. In the second stage, an algorithm of luminance adaptation versus lens aperture was inserted in the basic colorimetric profile. Capturing the ColorChecker chart under different light sources, and comparing the estimated XYZ data according to the developed color model in relation to the measured XYZ data (in cd/m2) using a tele- spectroradiometer, we verified that the proposed characterization model may be broken down into two portions. Firstly, there is the basic colorimetric profile in combination with the new luminance adaptation algorithm. Secondly, there is the linear correc- tion term due only to the mismatch of the color matching functions of the camera. Although the linear color correction term works relatively well, despite the imposed initial conditions (unknown spectral content of the scene), the separation of the proposed characterization model into two portions (raw and corrected performance) would allow the future comparison of various commercial cameras.
06 Nov 2003
TL;DR: In this paper, the impact of uncertainties in measuring the spectral response of the GUV channels on solar measurements is discussed, and the results are updated every minute on web pages, and can be accessed via the website www.biospherical.com/nsf, or the stations' intranets.
Abstract: Multi-channel moderate-bandwidth GUV filter radiometers have recently been added to the suite of instruments deployed in the US National Science Foundation Office of Polar Programs' UV monitoring network. The GUV instruments complement the stations' SUV-100 high-resolution scanning spectroradiometers, which have been monitoring UV levels in Antarctica, South America, and Alaska for more than a decade. The GUV instruments are used to help quality control SUV measurements, and to calculate total column ozone and a variety of biologically relevant UV integrals and dose-rates in real time. The results are updated every minute on web pages, and can be accessed via the website www.biospherical.com/nsf, or the stations' intranets. Online data may guide researchers on station in planning experiments, or for "first-look" analysis. The instruments underwent a detailed characterization. Their spectral response functions were measured with an apparatus that was specifically designed for this purpose. The apparatus and the data analysis method are described in detail with special attention given to a deconvolution method to correct measured data for the finite spectral resolution of the apparatus. The impact of uncertainties in measuring the spectral response of GUV channels on solar measurements is discussed. The GUV instruments are calibrated by comparison with a SUV-150B spectroradiometer, and dose-rates for 15 different biological action spectra are calculated based on an algorithm suggested by Dahlback. A comparison of calibrated GUV and SUV data indicates that erythemal (CIE) irradiance can be derived from GUV measurements to within 3% relative to the SUV up to a solar zenith angle (SZA) of 80°. A similar level of agreement can also be reached for other action spectra. Ozone values derived from GUV measurements at San Diego agree to within 3 Dobson Units (DU) with SUV ozone data and within a few DU with Earth Probe TOMS satellite observations.
23 Oct 2003
TL;DR: In this article, the spectral radiances of a high-temperature blackbody from 250 nm to 2400 nm were assigned using a spectroradiometer from the known spectral radiance of a variable temperature blackbody (VTBB) with a 0999 emissivity, and its temperature was found using ITS-90 techniques.
Abstract: For calibrations of spectral irradiance standards, a high‐temperature blackbody (HTBB) is used as a source of spectral radiance or irradiance as derived from Planck’s radiance law The temperature of such a blackbody can be determined using radiance ratios to the gold freezing‐temperature blackbody based on the technique described in the International Temperature Scale of 1990 (ITS‐90), or by using a primary thermometer, which is an absolute detector referenced to a cryogenic radiometer One of the primary motivations of using the detector‐based method is that the uncertainties in the temperature determination of a HTBB can be lower than those assigned using ITS‐90 Previous comparisons of temperatures measured using the two techniques have been at a few, selected wavelengths due to the limited measurement wavelengths of the comparison pyrometer In this study, the spectral radiances of a HTBB from 250 nm to 2400 nm are assigned using a spectroradiometer from the known spectral radiances of a variable‐temperature blackbody (VTBB) with a 0999 emissivity, and its temperature is found using ITS‐90 techniques The spectral radiances of the HTBB are also assigned using a primary thermometer These measurements are performed on four separate occasions over a period of one month The uncertainties in the detector‐based radiance temperature measurements are propagated directly from the spectral responsivity determinations, and propagating the correlations in the calculation of the uncertainties results in the detector‐based temperature uncertainty of 021 K (k = 2) at 3000 K, which is more than a factor of 6 lower than the uncertainties in the temperatures determined using ITS‐90 The agreement in radiance temperatures between the two methods is within the total combined expanded uncertainty of the temperature determination of the HTBB at 3000 K of 12 K (k = 2)
TL;DR: The spectral albedo and directional reflectance of snow and sea ice were measured using a spectroradiometer that has 512 channels in the visible and near-infrared (VNIR) region in which 16 of the 36 bands of the MODIS are covered as discussed by the authors.
Abstract: The spectral albedo and directional reflectance of snow and sea ice were measured on sea ice of various types, including nilas, grey ice, pancake ice, multi-year pack ice, and land-fast ice in the Ross, Amundsen and Bellingshausen seas during a summer cruise in February through March 2000. Measurements were made using a spectroradiometer that has 512 channels in the visible and near-infrared (VNIR) region in which 16 of the 36 bands of the Moderate Resolution Imaging Spectroradiometer (MODIS) are covered. Directional reflectance is also retrieved from the MODIS radiometrically calibrated data (Level 1B) concurrently acquired from the first National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) satellite, Terra. The locations of the ground ice stations are identified accurately on the MODIS images, and the spectral albedo and directional reflectance values at the 16 VNIR MODIS bands are extracted for those pixel locations. MODIS-derived reflectance is then corrected for the inter...
TL;DR: In this paper, reflected spectral radiance measured by the Multiangle Imaging SpectroRadiometer (MISR) on the Terra satellite has been analyzed to determine the fraction of global cloudiness that appears to be spatially homogeneous over regions of various sizes.
Abstract: Reflected spectral radiance measured by the Multiangle Imaging SpectroRadiometer (MISR) on the Terra satellite has been analyzed to determine the fraction of global cloudiness that appears to be spatially homogeneous over regions of various sizes.
09 Apr 2003
TL;DR: The NPOESS Visible Infrared Imaging Radiometer Suite (VIIRS) as discussed by the authors is an all-reflective 22-band single-sensor design, following the Critical Design Review (CDR) in Spring 2002 VIIRS provides low noise driven by ocean color for the reflective visible and near-IR spectral bands and by SST for the emissive mid and long-wave IR spectral bands.
Abstract: A new era in atmospheric remote sensing will begin with the launch of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) spacecraft in 2006, and the multiple operational NPOESS launches in sun-synchronous orbital planes (nominally 13:30, 17:30, or 21:30 local equatorial crossing times) starting in 2009 Cloud and atmosphere polar-orbiting environmental satellite data will be profoundly improved in radiometric quality, spectral coverage, and spatial resolution relative to current operational civilian and military polar-orbiting systems The NPOESS Visible Infrared Imaging Radiometer Suite (VIIRS) will provide Environmental Data Records (EDRs) for day and night atmosphere and cloud operational requirements, as well as sea surface temperature (SST) and many important land EDRs by ground processing of raw data records (RDRs) from the VIIRS sensor VIIRS will replace three currently operating sensors: the Defense Meteorological Satellite Program (DMSP) Operational Line-scanning System (OLS), the NOAA Polar-orbiting Operational Environmental Satellite (POES) Advanced Very High Resolution Radiometer (AVHRR), and the NASA Earth Observing System (EOS Terra and Aqua) MODerate-resolution Imaging Spectroradiometer (MODIS) This paper describes the VIIRS all-reflective 22-band single-sensor design, following the Critical Design Review (CDR) in Spring 2002 VIIRS provides low noise (driven by ocean color for the reflective visible and near-IR spectral bands and by SST for the emissive mid and long-wave IR spectral bands), excellent calibration and stability (driven by atmospheric aerosol and cloud EDRs, as well as SST), broad spectral coverage, and fine spatial resolution driven by the cloud imagery EDR In addition to improved radiometric, spectral, and spatial performance, VIIRS features DMSP OLS-like near-constant resolution, global twice-daily coverage in each orbit plane, and direct heritage to proven design innovations from the successful Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Earth Observing System (Terra and Aqua) MODIS
05 Sep 2003
TL;DR: In this article, the authors presented spectral results from a high-resolution FTIR spectroradiometer, Bomem DA5, which was used in the SIMVEX field trial arranged by NATO in Canada for validation of this model.
Abstract: The ship signature model ShipIR/NTCS has been selected as a NATO standard. In 2001 Norway participated in the SIMVEX field trial arranged by NATO in Canada for validation of this model. The measurements were performed on a research vessel under different meteorological conditions, when the ship was sun illuminated and shaded, and also at night. This paper presents spectral results from our high resolution FTIR spectroradiometer, Bomem DA5. Using in-house software that enables correction of non-ideal properties of the spectroradiometer, we obtained improved absolute precision of calibrated spectra. The FTIR results are most interesting for sources with signatures deviating significantly from blackbody functions, like the ship plume, sun illuminated surfaces and sea and sky backgrounds. Ship surface and sea and sky background results have been compared with ShipIR/NTCS predictions. Results from plume measurements have been compared with simulated spectra, using the FASCODE atmospheric model, and we have estimated the plume temperature and the concentration of the most important IR contributing molecules.
09 Apr 2003
TL;DR: In this article, the spectral radiance of a 51 cm diameter Spectralon sphere illuminated by an external xenon arc and by internal QTH lamps was measured using a calibration transfer standard spectroradiometer using 14 narrow ion-assisted deposition filters covering the wavelength region from 250 to 920 nm.
Abstract: Radiometric calibration of large aperture space-borne remote sensing instruments designed to measure atmospheric radiances in the 250 to 400 nm wavelength range is difficult. Historically the spectral radiance calibrations of these instruments have been derived from aperture radiances of integrating spheres illuminated internally by quartz-tungsten-halogen (QTH) lamps. Typical aperture radiances increase by a factor of 400 from 250 to 400 nm and by an additional factor of 10 from 400 to 900 nm. The characteristics of the aperture radiances of 51 cm diameter Spectralon sphere illuminated by an external xenon arc and by internal QTH lamps have been measured. The aperture radiance of the sphere illuminated externally by the xenon arc is 15 times larger at 250 nm than the radiance from internal QTH lamp illumination. The radiometric stability and the aperture uniformity at 290 nm from the two types of illumination are comparable. These measurements have been made with a calibration transfer standard spectroradiometer using 14 narrow ion-assisted deposition filters covering the wavelength region from 250 to 920 nm. The calibration scale of the transfer radiometer is tied to a NIST 1000 W FEL lamp spectral irradiance standard.
01 Jan 2003
TL;DR: The spectral reflectance of the Moon is an important property for studies of lunar geology, quantitative physical modeling of the moon, and in-flight calibration of spacecraft sensors.
Abstract: The spectral reflectance of the Moon is an important property for studies of lunar geology, quantitative physical modeling of the moon, and in-flight calibration of spacecraft sensors. Previous studies have claimed that telescopic absolute reflectance values for the Moon are greater than laboratory reflectance measurements by a factor of two. In order to confirm these results, we performed ground-based observations of the lunar surface using a visible/near-infrared spectroradiometer and compared the measured lunar surface radiance to solar radiance corrected for atmospheric scattering and absorption. These data were compared to previously obtained laboratory reflectance measurements from Apollo soil samples.
TL;DR: In this article, a calibration facility consisting of the variable temperature blackbody, the standard radiation pyrometer and the spectroradiometer is described, and the relative standard uncertainty of the KRISS spectral radiance scale is determined.
Abstract: The KRISS spectral radiance standards have been realized from 250 nm to 2.5 µm with reference to the radiance temperature scale. Based on the definition of the ITS-90, the temperature scale has been realized using a copper and silver point blackbody. This paper briefly describes the calibration facility, which consists of the variable temperature blackbody, the standard radiation pyrometer and the spectroradiometer. All of the radiating sources and the measurement system were fully controlled automatically and operated by two personal computers. The stabilities, noise characteristics, linearity and size of source effect of the spectroradiometer have been measured. Using two sheets of polarizer, the degree of linear polarization induced by the spectroradiometer and the Mueller matrix elements of the polarizer have also been simultaneously measured. For a tungsten strip lamp to be used as a spectral radiance transfer source, the current coefficient of spectral radiance, the stability in conjunction with the power supply and the degree of polarization have been measured to yield correction values at the reference condition after calibration. A mathematical model for the correction procedure and uncertainty analysis of the calibration is proposed. The relative standard uncertainty of the KRISS spectral radiance scale is determined to be 0.83% at 250 nm, 0.49% at 300 nm and less than 0.3% from 650 nm to 2.5 µm.
02 Jun 2003
TL;DR: In this paper, a viewgraph presentation reviews the concept of the Multi-Angle Imaging SpectroRadiometer (MISR), a methodology to use the MISR to retrieve aerosols over water and land.
Abstract: This viewgraph presentation reviews the concept of the Multi-Angle Imaging SpectroRadiometer (MISR), a methodology to use the MISR to retrieve aerosols over water and land. The presentation shows some of the results of the use of the MISR in graphs and charts. Multi-angle remote sensing provides unique ways of retrieving aerosol properties over many surface types, including bright deserts which are major source regions.
04 Nov 2003
TL;DR: In this paper, two recently developed different types of fast spectroradiometers measuring solar UV irradiance have been compared in a field campaign: (1) the UV Spectroradiometer on filter model basis (UV-SPRAFIMO) and (2) the modified version of the Spectro 320D by Instrument Systems.
Abstract: Two recently developed different types of fast spectroradiometers measuring solar UV irradiance have been compared in a field campaign: i) the UV spectroradiometer on filter model basis (UV-SPRAFIMO) and ii) the modified version of the spectroradiometer SPECTRO 320D by Instrument Systems. The all-weather UV-SPRAFIMO instrument combines a UV filter radiometer with 5 narrow-band (FBHM ≈ 2.0 to 2.5 nm) filters centered within ± 0.01 nm at 303.5, 309.0, 314.5, 327.0 and 387.0 nm, and an advanced neural network-based model. It allows up to 5 measurements per second to be taken that are averaged within time intervals between 5 and 30 s. The neural networks model that is embedded in the PC-based processing software converts the 5 measured irradiances into a full spectrum from 280 to 450 nm at small wavelength steps (≥ 0.05 nm). These spectra can be convoluted with user-defined slit function and integrated to broad-band and action-spectra-weighted irradiance values. Users can access the data stored in the internal data logger by a serial RS232 interface or by a modem and display them on a PC-based Graphical User Interface.
The spectroradiometer SPECTRO320D consists of a grating double monochromator with a cooled (-20°C) PMT receiver. The modified instrument version run by DWD uses a Schreder type cosine diffuser that directs the solar global irradiance via quartz fiber optics onto the spectroradiometer's entrance slit. The spectroradiometer used at the campaign was installed in a thermostatted (22 ± 0.02)°C aluminum box. The modified instrument version performs a spectral scan over the whole UV region in two subsequent parts, with a lower speed in the UV-B than in the UV-A to account for the exponential changes of solar irradiance with increasing wavelengths in the UV-B and for the almost linear change in the UV-A region. In the configuration applied in the comparison, i.e. wavelength steps of 0.2 nm within the scan range from 290 nm to 450 nm, the resulting scan time of the SPECTRO 320D was 23 s. The two spectroradiometers, which both have been absolutely calibrated in the DWD lab using FEL 1000 W halogen lamps traceable to the German Physikalisch-Technische Bundesanstalt (PTB), were used in a field campaign at Izana (Tenerife Island) at a height of 2409 m to compare measured spectral and integral values of solar irradiance. Results of that comparison and the instruments’ characteristics revealed under those special field conditions will be discussed.
21 Jul 2003
TL;DR: Both surface temperature and near-surface air temperature can be determined radiometrically from measurements of the infrared emission spectra of the surface and atmosphere, and the use of a Fourier-transform infrared spectroradiometer on ships can provide such data.
Abstract: The polar regions are considered to be particularly sensitive to climate change. The complex interactions between the surface and the overlying atmosphere are important aspects of the local heat budget, and through the atmospheric and oceanic general circulations, to global scales. The temperature difference between the surface and the lowest layer of the air is an important parameter in the surface heat budget, but difficult to measure, especially in conditions of mixed sea-ice and open water. Both surface temperature and near-surface air temperature can be determined radiometrically from measurements of the infrared emission spectra of the surface and atmosphere. The use of a Fourier-transform infrared spectroradiometer, the M-AERI (Marine-Atmospheric Emitted Radiance Interferometer) on ships can provide such data.
23 Oct 2003
TL;DR: The VNIIOFI Spectroradiometer (VSR) as mentioned in this paper was designed to measure the radiance temperature of the blackbody sources in the spectral range from 2.5 μm up to 14 μm in a cryogenic vacuum environment.
Abstract: The VNIIOFI Spectroradiometer (VSR) has been developed for the Medium Background Facility which is intended for calibrations and comparisons of low‐temperature sources in the temperature range from −60 °C up to +80 °C. The VSR is designed to measure the radiance temperature of the blackbody sources in the spectral range from 2.5 μm up to 14 μm in a cryogenic vacuum environment (liquid nitrogen cooled shroud). The VSR is based on the Circular Variable Filter (CVF) assembly with a slit aperture and an InSb‐CdHgTe two color sandwich detector with an integral Stirling cooler. The Circular Variable Filter covers the 2.5 μm to 14.1 μm region in three segments. The width of the slit equal to 1.2 mm provides a spectral resolution from 80 nm to 360 nm for the spectral range from 2.5 μm to 14.1 μm accordingly. The Circular Variable Filter assembly is rotated by a stepper motor. The Cassegrain telescope is used as a foreoptic unit. Radiation passes through the CVF and is focused on the detector with help of the ellipsoidal mirror. Radiation from a low‐temperature (77 K) blackbody is used as a reference level of radiation. The instrument has a field of view of 8.9 mrad with a distance to the object being equal to 2250 mm. The spectral and temporal characterizations of the spectroradiometer are reported. The facility for CVF calibration is described. Temperature resolutions for the calibrated sources are given for different temperatures and for different wavelengths. A brief description of the design, operation principles and specifications of the main parts of the spectroradiometer such as the Cassegrain telescope, CVF and detector assembly are presented. The measurement uncertainties of radiance temperature associated with spectral bandwidth are discussed.
01 Jan 2003
TL;DR: A rotating shadowband spectroradiometer (RSS) operating in the spectral range between 350 to 1050 nm obtained measurements of direct and diffuse components of spectral irradiance during the first diffuse irradiance IOP in the autumn of 2001.
Abstract: A rotating shadowband spectroradiometer (RSS) operating in the spectral range between 350 to 1050 nm obtained measurements of direct and diffuse components of spectral irradiance during the first diffuse irradiance IOP in the autumn of 2001. Independent measurements of the primary inputs to spectral irradiance models, including aerosol optical depth, water vapor column, and ozone column measurements, were used. A parameterized spectral surface albedo based on filter measurements provided realistic surface reflectance as a further input to the models. Plausible wavelength independent single scattering albedo and asymmetry parameter were assumed for the column based on in situ surface-based measurements typical of early autumn. Spectral irradiance measurements are compared to three models including, MODTRAN, SBDART, and SMARTS2.