Blackbody calibration sources of high accuracy for a spaceborne infrared instrument: the Along Track Scanning Radiometer

Mason, Ian; Sheather, P. H.; Bowles, J. A.; Davies, G.

doi:10.1364/ao.35.000629

Cited by 48 publications

(21 citation statements)

References 5 publications

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“…Two targets ("hot" and "cold" at approximately 301 K and 263 K respectively) are viewed every scan for calibration, and the detectors are cooled to 80 K by a Stirling Cycle cooler to ensure that the radiometric noise of these channels at 270 K is <0.05 K. The AATSR is radiometrically calibrated to a high accuracy; pre-launch calibration using high-accuracy external black bodies indicated that the AATSR BTs were within 30 mK of target temperatures for the 11 and 12 µm channels (Smith et al, 2001). The heritage of the instrument design is well proven since AATSR is the third instrument (for results for radiometric design and accuracy of the earlier ATSR-1 and ATSR-2 instruments see e.g., Mutlow et al (1994)) founded on well-designed black bodies for radiometers (Mason et al, 1996).…”

Section: Aatsrmentioning

confidence: 98%

Intercomparison of integrated IASI and AATSR calibrated radiances at 11 and 12 μm

2009

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Abstract. The mission objectives of the Infrared Atmospheric Sounding Interferometer (IASI) are driven by the needs of the Numerical Weather Prediction (NWP) and climate monitoring communities. These objectives rely upon the IASI instrument being able to measure top of atmosphere radiances accurately. This paper presents a technique and first results for the validation of the radiometric calibration of radiances for IASI, using a cross-calibration with the Advanced Along Track Scanning Radiometer (AATSR). The AATSR is able to measure Brightness Temperature (BT) to an accuracy of 30 mK, and by applying the AATSR spectral filter functions to the IASI measured radiances we are able to compare AATSR and IASI Brightness Temperatures. By choosing coincident data points that are over the sea and in clear sky conditions, a threshold of homogeneity is derived. It is found that in these homogenous conditions, the IASI BTs agree with those measured by the AATSR to within 0.3 K, with an uncertainty of order 0.1 K. The agreement is particularly good at 11 µm where the difference is less than 0.1 K. These first results indicate that IASI is meeting its target objective of 0.5 K accuracy. It is believed that a refinement of the AATSR spectral filter functions will hopefully permit a tighter error constraint on the quality of the IASI data and hence further assessment of the climate quality of the radiances.

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Section: Aatsrmentioning

confidence: 98%

Intercomparison of integrated IASI and AATSR calibrated radiances at 11 and 12 μm

2009

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“…There are two approaches to managing the internal surface of a thermal infrared blackbody cavity: one can either choose a specular surface (e.g., Geist and Fowler 1986;Fowler 1995) or a diffuse surface (e.g., Mason et al 1996). Although specular paint surfaces are easier to model using Monte Carlo methods, diffuse paint gives a slightly higher emissivity.…”

Section: B Cavity Geometry and Manufacturementioning

confidence: 99%

A Second-Generation Blackbody System for the Calibration and Verification of Seagoing Infrared Radiometers

Donlon

Wimmer

Robinson

et al. 2014

Journal of Atmospheric and Oceanic Technology

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Quasi-operational shipborne radiometers provide a fiducial reference measurement (FRM) for satellite validation of satellite sea surface skin temperature (SST skin ) retrievals. External reference blackbodies are required to verify the performance and to quantify the accuracy of the radiometer calibration system. They provide a link in an unbroken chain of comparisons between the shipborne radiometer and a traceable reference standard. A second-generation water bath blackbody reference radiance source has been developed for this purpose. The second generation Concerted Action for the Study of the Ocean Thermal Skin (CASOTS-II) blackbody has a 110-mm-diameter aperture cylinder-cone geometry coated with NEXTEL suede 3103 paint. Interchangeable aperture stops reduce the cavity aperture diameter and minimize stray radiation. Monte Carlo modeling techniques show the effective emissivity of the cavity to be .0.9999 (aperture , 30 mm). The cavity is immersed in a water bath that is vigorously stirred using a pump that slowly heats the water bath at a mean rate of ;0.6 K h 21. The temperature of the water bath is measured using a thermometer traceable to the International System of Units (SI) standards. The worst-case radiance temperature of the CASOTS-II blackbody system is traceable to the SI with an uncertainty of 58 mK (millikelvin). When operating under typical laboratory conditions using an aperture of 40 mm, the uncertainty is 16 mK. An intercomparison with the U.K. National Physical Laboratory Absolute Measurements of Blackbody Emitted Radiance (AMBER) reference radiometer found no significant differences within 75 mK (110-mm aperture) or 50 mK (40-mm aperture), which is the combined uncertainty of the comparison and the reference standard for SI traceability of ISAR radiometer SST skin records used for satellite SST validation. Applications of the CASOTS-II blackbody to monitor the calibration of shipborne radiometers are described and measurement protocols are proposed.

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“…7 Calibration of the cavity emissivity follows the approach used for the ATSR instruments in which witness samples of the black coating were measured at National Institute of Standards and Technology (NIST) and incorporated into a Monte Carlo model to account for the cavity geometry. The model was originally validated for the ATSR BBs by comparing it against a reference BB whose emissivity is higher (i.e., >0.9995).…”

Section: Thermal Infraredmentioning

confidence: 99%

Calibration approach and plan for the sea and land surface temperature radiometer

Smith

Nightingale

Mortimer

et al. 2014

J. Appl. Remote Sens

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Abstract. The sea and land surface temperature radiometer (SLSTR) to be flown on the European Space Agency's (ESA) Sentinel-3 mission is a multichannel scanning radiometer that will continue the 21 year dataset of the along-track scanning radiometer (ATSR) series. As its name implies, measurements from SLSTR will be used to retrieve global sea surface temperatures to an uncertainty of <0.3 K traced to international standards. To achieve, these low uncertainties require an end-to-end instrument calibration strategy that includes prelaunch calibration at subsystem and instrument level, on-board calibration systems, and sustained postlaunch activities. The authors describe the preparations for the prelaunch calibration activities, including the spectral response, the instrument level alignment tests, and the solar and infrared radiometric calibrations. A purpose built calibration rig has been designed and built at the Rutherford Appleton Laboratory space department (RAL Space) that will accommodate the SLSTR instrument, the infrared calibration sources, and the alignment equipment. The calibration rig has been commissioned and results of these tests will be presented. Finally, the authors will present the planning for the on-orbit monitoring and calibration activities to ensure that the calibration is maintained. These activities include vicarious calibration techniques that have been developed through previous missions and the deployment of ship-borne radiometers. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Blackbody calibration sources of high accuracy for a spaceborne infrared instrument: the Along Track Scanning Radiometer

Cited by 48 publications

References 5 publications

Intercomparison of integrated IASI and AATSR calibrated radiances at 11 and 12 μm

Intercomparison of integrated IASI and AATSR calibrated radiances at 11 and 12 μm

A Second-Generation Blackbody System for the Calibration and Verification of Seagoing Infrared Radiometers

Calibration approach and plan for the sea and land surface temperature radiometer

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