Abstract
Spectrometer calibration and measurements of spectral radiance are often required when performing ground, aerial, and space measurements. While calibrating a spectrometer in the field using an integrating sphere is practically unachievable, calibration against a quartz halogen (QH) lamp is a quite easy and feasible option. We describe a calibration protocol whereby a professional QH lamp, operating with a stabilized current source, is first calibrated in the laboratory against a US National Institute of Standards and Technology (NIST) traceable integrating sphere and, then, used for the field calibration of a spectrometer before a ground or airborne campaign. Another advantage of the lamp over the integrating sphere is its ability to create a continuous calibration curve at the spectrometer resolution, while the integrating sphere is calibrated only for a few discrete wavelengths. A calibrated lamp could also be used for a secondary continuous calibration of an un-calibrated integrating sphere.
Highlights
IntroductionSpectrometers are often used by the remote sensing community to characterize in situ the reflectance of surface features and to perform vicarious calibrations of air- and spaceborne sensors.The spectra measured vary from specific objects and small areas (e.g., leaves, rocks) to compositeRemote Sens. 2014, 6 scenes (e.g., vegetation canopies), and, to image pixels [1,2,3]
Spectrometers are often used by the remote sensing community to characterize in situ the reflectance of surface features and to perform vicarious calibrations of air- and spaceborne sensors.The spectra measured vary from specific objects and small areas to compositeRemote Sens. 2014, 6 scenes, and, to image pixels [1,2,3]
We describe a calibration protocol whereby a professional quartz halogen (QH) lamp, operating with a stabilized current source, is first calibrated in the laboratory against a US National Institute of Standards and Technology (NIST) traceable integrating sphere and, used for the field calibration of a spectrometer before a ground or airborne campaign
Summary
Spectrometers are often used by the remote sensing community to characterize in situ the reflectance of surface features and to perform vicarious calibrations of air- and spaceborne sensors.The spectra measured vary from specific objects and small areas (e.g., leaves, rocks) to compositeRemote Sens. 2014, 6 scenes (e.g., vegetation canopies), and, to image pixels [1,2,3]. Measuring radiance rather than reflectance is necessary when performing aerial measurements for which Spectralon calibration is cumbersome [4]. On this occasion, a pre-flight absolute calibration of the irradiance received at the device’s aperture is needed. A fiber optic extension is often used to connect the spectrometer located inside the airplane to the collecting optics located in a pod at the bottom of the aircraft. In this case, the calibration of the spectrometer must be done in the field. While this calibration procedure is usually performed using an integrating sphere (described below) [5], it is not feasible to move and use this delicate and often large device in the field
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