The Calibration Home Base for Imaging Spectrometers: Present Activities in an Overview

Abstract

The Calibration Home Base (CHB) at the Remote Sensing Technology Institute of the German Aerospace Center DLR-IMF) is an optical laboratory designed for the calibration of imaging spectrometers for the VNIR/SWIR wavelength range. Radiometric, spectral and geometric characterization is realized in the CHB in a precise and highly automated fashion. This allows performing a wide range of time consuming measurements in an effcient way. The implementation of ISO 9001 standards in all procedures ensures a traceable quality of results. DLR-IMF owns a Norsk Elektro Optikks A/S HySpex airborne imaging spectrometer system. Consisting of two separate devices (VNIR-1600 and SWIR-320me) the setup covers the spectral range from 400 nm to 2500 nm. This system, which is available to the public for flight campaigns, has been thoroughly characterized in the CHB. Due to the latter, the Level 1 data produced by this HySpex system is of very high quality. While the manufacturers calibration has been compared to device parameters determined in the CHB, additional parameters have been measured. These include, among other data, spectral response and line spread functions. DLR-IMF will support the calibration and characterization campaign of the future German spaceborne hyperspectral imager EnMAP. In the context of this campaign, a procedure for the correction of imaging artifacts, such as caused by stray light, is currently being developed. Goal is the correction of diffuse in-band stray light as well as ghosts down to a level of a few digital numbers in the whole wavelength range 400-2500 nm. Compared to EnMAP the HySpex sensors have the same or higher spectral and spatial resolution. Therefore, airborne data will be used to prepare for and validate the spaceborne systems data. Hyperspectral snapshot or single frame sensors offer the possibility to simultaneously acquire hyperspectral data in 2 dimensions. Recently, these rather new spectrometers have arisen much interest in the remote sensing community. Different designs are currently used for "smaller scale" observation such as by use of small unmanned aerial vehicles. In this context the CHBs measurement capabilities are currently extended such that a standard measurement procedure for these new sensors will be implemented. The CHB and the airborne Hyspex sensors are made available to the public through the user service Optical Airborne Remote Sensing and Calibration Home Base (OpAiRS).