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ABSTRACT: In 2004, the National Institute of Standards and Technology established the ultraviolet spectral irradiance scale from 200 nm to 400 nm using the calculable irradiance of the Synchrotron Ultraviolet Radiation Facility (SURF). Since the establishment of the scale, spectral irradiance calibrations of many customer lamps have been performed in direct comparison with synchrotron radiation. However, to ensure long-term stability of the scale, three check-standard deuterium lamps were calibrated using SURF III at the same time as customer lamps were being calibrated. Here, we present the results of the long-term monitoring of the scale using these check-standard lamps to ensure customer lamps are calibrated within the expanded calibration uncertainty (k = 2) of 1.2%.
Metrologia 06/2010; 47(4):429. · 1.75 Impact Factor
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ABSTRACT: The development of a radiation thermometer calibrated for spectral radiance responsivity using cryogenic, electrical-substitution radiometry to determine the thermodynamic temperatures of the Ag- and Au-freezing temperatures is described. The absolute spectral radiance responsivity of the radiation thermometer is measured in the NIST Spectral Irradiance and Radiance Responsivity Calibrations using Uniform Sources (SIRCUS) facility with a total uncertainty of 0.15% (k=2) and is traceable to the electrical watt, and thus the thermodynamic temperature of any blackbody can be determined by using Planck radiation law and the measured optical power. The thermodynamic temperatures of the Ag- and Au-freezing temperatures are determined to be 1234.956 K (+/-0.110 K) (k=2) and 1337.344 K(+/-0.129 K) (k=2) differing from the International Temperature Scale of 1990 (ITS-90) assignments by 26 mK and 14 mK, respectively, within the stated uncertainties. The temperatures were systematically corrected for the size- of-source effect, the nonlinearity of the preamplifier and the emissivity of the blackbody. The ultimate goal of these thermodynamic temperature measurements is to disseminate temperature scales with lower uncertainties than those of the ITS-90. These results indicate that direct disseminations of thermodynamic temperature scales are possible.
Applied Optics 06/2007; 46(15):2870-80. · 1.41 Impact Factor
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ABSTRACT: A new facility for measuring irradiance in the UV was commissioned recently at the National Institute of Standards and Technology (NIST). The facility uses the calculable radiation from the Synchrotron Ultraviolet Radiation Facility as the primary standard. To measure the irradiance from a source under test, an integrating sphere spectrometer-detector system measures both the source under test and the synchrotron radiation sequentially, and the irradiance from the source under test can be determined. In particular, we discuss the calibration of deuterium lamps using this facility from 200 to 400 nm. This facility improves the current NIST UV irradiance scale to a relative measurement uncertainty of 1.2% (k=2).
Applied Optics 02/2007; 46(1):25-35. · 1.41 Impact Factor
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ABSTRACT: In radiometry, photometry and radiation thermometry, accurate measurements of the radiance, luminance or the radiance temperatures of sources requires a knowledge of the contribution from the surroundings to the measured signal from the target area. The dependence of the radiometer or the radiation thermometer on the area surrounding the target area is described as the size-of-source effect (SSE), and minimizing the radiometer's sensitivity to SSE is critical in the lowest-uncertainty optical measurements. We describe the dominant effects that influence the SSE, and show that the SSE can be reduced to <5 × 10−5 as measured using a 50 mm diameter radiance source with a 2 mm diameter, central obscuration. The SSE is found to be dependent on the internal scatter and the optical design of the radiometer. For testing the contributions to SSE, a radiometer is constructed with a 50.8 mm diameter lens in f/12 geometry with a 1 mm diameter target size. If the internal radiometer scatter is reduced, then the SSE is found to be primarily dependent on the scatter from the objective lens such as surface finish, internal lens scatter and the particulate contamination of the lens. Various combinations of objective lenses are measured for SSE, and the relative merits of increasing optical performance at the expense of additional optical elements are also discussed.
Metrologia 02/2005; 42(2):89. · 1.75 Impact Factor
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ABSTRACT: The temporal stability of the National Institute of Standards and Technology (NIST) spectral irradiance scale as measured with broadband filter radiometers calibrated for absolute spectral irradiance responsivity is described. The working standard free-electron laser (FEL) lamps and the check standard FEL lamps have been monitored with radiometers in the ultraviolet and the visible wavelength regions. The measurements made with these two radiometers reveal that the NIST spectral irradiance scale as compared with an absolute thermodynamic scale has not changed by more than 1.5% in the visible from 1993 to 1999. Similar measurements in the ultraviolet reveal that the corresponding change is less than 1.5% from 1995 to 1999. Furthermore, a check of the spectral irradiance scale by six different filter radiometers calibrated for absolute spectral irradiance responsivity based on the high-accuracy cryogenic radiometer shows that the agreement between the present scale and the detector-based scale is better than 1.3% throughout the visible to the near-infrared wavelength region. These results validate the assigned spectral irradiance of the widely disseminated NIST or NIST-traceable standard sources.
Applied Optics 11/2002; 41(28):5872-8. · 1.41 Impact Factor
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ABSTRACT: A detector-based spectral irradiance scale has been realized at the National Institute of Standards and Technology (NIST). Unlike the previous NIST spectral irradiance scales, the new scale is generated with filter radiometers calibrated for absolute spectral power responsivity traceable to the NIST high-accuracy cryogenic radiometer instead of with the gold freezing-point blackbody. The calibrated filter radiometers are then used to establish the radiance temperature of a high-temperature blackbody (HTBB) operating near 3,000 K The spectral irradiance of the HTBB is then determined with knowledge of the geometric factors and is used to assign the spectral irradiances of a group of 1,000-W free-electron laser lamps. The detector-based spectral irradiance scale results in the reduction of the uncertainties from the previous source-based spectral irradiance scale by at least a factor of 2 in the ultraviolet and visible wavelength regions. The new detector-based spectral irradiance scale also leads to a reduction in the uncertainties in the shortwave infrared wavelength region by at least a factor of 2-10, depending on the wavelength. Following the establishment of the spectral irradiance scale in the early 1960s, the detector-based spectral irradiance scale represents a fundamental change in the way that the NIST spectral irradiance scale is realized.
Applied Optics 11/2002; 41(28):5879-90. · 1.41 Impact Factor
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James J. Butler,
B. Carol Johnson,
Steven W. Brown, Howard W. Yoon,
Robert A. Barnes,
Brian L. Markham,
Stuart F. Biggar,
Edward F. Zalewski,
Paul R. Spyak,
John W. Cooper,
Fumihiro Sakuma
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ABSTRACT: EOS satellite instruments operating in the visible through the shortwave infrared wavelength regions (from 0.4 micrometer to 2.5 micrometer) are calibrated prior to flight for radiance response using integrating spheres at a number of instrument builder facilities. The traceability of the radiance produced by these spheres with respect to international standards is the responsibility of the instrument builder, and different calibration techniques are employed by those builders. The National Aeronautics and Space Administration's (NASA's) Earth Observing System (EOS) Project Science Office, realizing the importance of preflight calibration and cross-calibration, has sponsored a number of radiometric measurement comparisons, the main purpose of which is to validate the radiometric scale assigned to the integrating spheres by the instrument builders. This paper describes the radiometric measurement comparisons, the use of stable transfer radiometers to perform the measurements, and the measurement approaches and protocols used to validate integrating sphere radiances. Stable transfer radiometers from the National Institute of Standards and Technology, the University of Arizona Optical Sciences Center Remote Sensing Group, NASA's Goddard Space Flight Center, and the National Research Laboratory of Metrology in Japan, have participated in these comparisons. The approaches used in the comparisons include the measurement of multiple integrating sphere lamp levels, repeat measurements of select lamp levels, the use of the stable radiometers as external sphere monitors, and the rapid reporting of measurement results. Results from several comparisons are presented. The absolute radiometric calibration standard uncertainties required by the EOS satellite instruments are typically in the plus or minus 3% to plus or minus 5% range. Preliminary results reported during eleven radiometric measurement comparisons held between February 1995 and May 1998 have shown the radiance of integrating spheres agreed to within plus or minus 2.5% from the average at blue wavelengths and to within plus or minus 1.7% from the average at red and near infrared wavelengths. This level of agreement lends confidence in the use of the transfer radiometers in validating the radiance scales assigned by EOS instrument calibration facilities to their integrating sphere sources.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
12/1999;
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Stanford B. Hooker,
Elaine R. Firestone,
B. Carol Johnson, Howard W Yoon,
Sally S. Bruce,
Ping-Shine Shaw,
Ambler Thompson,
Robert A. Barnes,
Eplee,
Robert E,
Stephane Maritorena,
James L. Mueller
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ABSTRACT: This report documents the fifth Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Intercalibration Round-Robin Experiment (SIRREX-5), which was held at the National Institute of Standards and Technology (NIST) on 23-30 July 1996. The agenda for SIRREX-5 was established based on recommendations made during SIRREX-4. For the first time in a SIRREX activity, instrument intercomparisons were performed at field sites, which were near NIST. The goals of SIRREX-5 were to continue the emphasis on training and the implementation of standard measurement practices, investigate the calibration methods and measurement chains in use by the oceanographic community, provide opportunities for discussion, and intercompare selected instruments. As at SIRREX-4, the day was divided between morning lectures and afternoon laboratory exercises. A set of core laboratory sessions were performed: 1) in-water radiant flux measurements; 2) in-air radiant flux measurements; 3) spectral radiance responsivity measurements using the plaque method; 4) device calibration or stability monitoring with portable field sources; and 5) various ancillary exercises designed to illustrate radiometric concepts. Before, during, and after SIRREX-5, NIST calibrated the SIRREX-5 participating radiometers for radiance and irradiance responsivity. The Facility for Automated Spectroradiometric Calibrations (FASCAL) was scheduled for spectral irradiance calibrations for standard lamps during SIRREX-5. Three lamps from the SeaWiFS community were submitted and two were calibrated.
11/1999;
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ABSTRACT: The Synchrotron Ultraviolet Radiation Facility SURF III at the National Institute of Standards and Technology provides a unique opportunity for high-accuracy ultraviolet UV to infrared radiometry due to the 70-fold improvement in the uniformity of the magnetic field from the previous generation of SURF. This improvement enables the properties of the output radiation, such as spectral power, angular spread, and polarization, to be more accurately predicted based on the use of the Schwinger's equation. The radiation from SURF III is completely characterized by only three parameters, the magnetic field, the radius of the electron beam trajectory, and the electron beam current. For radiometry, the calculability of SURF III provides an important standard light source for source intercomparison. In contrast to the widely used blackbody source where the thermal radiation is completely characterized by the temperature and the emissivity of the blackbody walls, synchrotron radiation extends the wavelength range to UV and x ray which is impractical for blackbody sources. At SURF III, a new beamline, beamline 3, is constructed as a white light beamline for source-based radiometry. We describe the design of the new beamline 3 and its front-end high accuracy electron beam current monitor. This monitor not only measures one of the three fundamental parameters, the electron beam current, it also serves as an electron beam diagnostic tool. We also discuss ways to verify the calculability of SURF III using filter radiometers. © 2002 American Institute of Physics.
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ABSTRACT: In the International Temperature Scale of 1990 (ITS-90), temperatures above the freezing temperature of silver are determined with radiation thermometers calibrated using spectral radiance ratios to one of the Ag-, Au-or Cu-freezing temperature blackbodies and the Planck radiance law. However, due to the use of spectral radiance rats, the temperature uncertainties of the ITS -90 increase as the square of the temperature ratios. Recent acoustic-gas thermometry measurements have also shown that the underlying thermodynamic temperatures used in the radiance ratios in determining the Ag-and Au-fixed point temperatures could be in error. Since the establishment of ITS-90, much progress has been made in the development of radiation thermometers and blackbody sources. Cryogenic electrical -substitution radiometry is widely used in detector and radiometer calibrations, and stable, high-temperature metal-carbon eutectic blackbodies are under development. Radiation thermometers can be calibrated for absolute radiance responsivity, and blackbody temperatures determined from measurement of optical power without the use of any fixed points thus making possible direct dissemination of thermodynamic temperatures. We show that these temperatures can be measured with lower final uncertainties than the ITS -90 derived temperatures. We have shown that these "Absolute Pyrometers" can be used to determine the thermodynamic temperatures of the ITS-90 fixed points as well as also being used in bilateral comparisons of temperature scales. Many leading national measurement institutes are already utilizing detector-based temperatures in establishing spectroradiometric source scales. We believe, that due to these developments, the international temperature scale should be revised so that a thermodynamic temperature scale can be directly disseminated.
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ABSTRACT: A new source-based radiometry beamline was recently constructed at the Synchrotron Ultraviolet Radiation Facility (SURF III). The goal of this beamline is to establish a national source standard with a wide spectral range from the far ultraviolet to the infrared by using the calculability of SURF III. The new beamline is a straight-through white-light beamline with few, if any, optical components involved in delivering the radiation to the user end-station for applications such as source and irradiance intercomparisons. Due to the low tunable operating electron energy of SURF III (from 380 MeV to less than 100 MeV), the beamline is uniquely suited to work in the ultraviolet to infrared spectral range. In this paper we discuss the design of the beamline and present first results on the vertical angular distribution of the radiation determined with filtered radiometers in the ultraviolet, visible and near-infrared spectral ranges.
