Preflight and Vicarious Calibration of Hyperspectral Imagers

摘要

We developed a calibration plan for a hyperspectral sensor and then designed, built, and calibrated three major instruments to support such calibrations. The instruments included two transfer radiometers, one covering the visible and near infrared using a silicon detector, and another covering the short-wave infrared using a cooled InGaAs detector. The third instrument was an improved model of an autotracking solar radiometer (ASR) that incorporated two, cooled InGaAs detector bands in addition to the typical 10 silicon detector bands of the previous model ASR. The transfer radiometers were delivered to the USAF calibration laboratory. The solar radiometer was used in the field and at the University of Arizona to collect optical depth data for calibration and testing and for the vicarious calibration of ARTEMIS. Prior to the launch of ARTEMIS we made measurements at Kirtland for a preflight radiance calibration. After the launch of the ARTEMIS sensor, we provided vicarious calibration information from a number of field campaigns to assist the USAF in radiometric calibration of the sensor. We used the new ASR (along with an older 10-band radiometer) to collect atmospheric data, and field spectrometers and reference panels to collect ground reflectance data. We then used MODTRAN-5 to compute a top of atmosphere radiance spectrum covering the range of 350 to 2500 nm and provided that, along with the reflectance spectrum of the ground surface and spectral optical depth, to the USAF for the calibration of ARTEMIS. We have continued to use and calibrate the ASR in order to better understand the limitations and use of the additional SWIR bands.