Laboratory calibration and in-flight validation of the Digital Airborne Imaging Spectrometer DAIS 7915

In the past various authors pointed out, that the value of imaging spectrometer data is closely related to the accuracy with which the data are calibrated to represent physical parameters. The AVIRIS team at JPL gave good examples on how the calibration can be performed in the laboratory and how its accuracy can be evaluated independently by means of an in-flight calibration/validation experiment(1,2,3). The first part of this paper presents the laboratory instrumentation and measurements that were brought into place at the German Aerospace Research Establishment (DLR) to calibrate the DAIS 7915 sensor. Some estimates of the accuracy of these measurements are given to allow the derivation of an overall precision of the laboratory calibration. It is the purpose of an in-flight calibration and validation campaign to check the validity of the laboratory calibration for data acquired under in-flight conditions. In a joint experiment of DLR and the Remote Sensing Laboratories (RSL) of the University of Zurich the DAIS instrument flew a standard test site in the center of Switzerland in summer 1996. In parallel to this overflight a number of ground reference measurements are acquired. The influence of the atmosphere is accounted for using the MODTRAN(4) radiative transfer code. Sample spectra from different in-flight calibration targets are displayed.