Frank Lehmann

79-Channel Airborne Imaging Spectrometer

The European Community and DLR are funding a 79-channel airborne imaging spectrometer (DAIS-7915) to be used for remote sensing applications such as environmental monitoring of land and marine ecosystems, vegetation stress research, agriculture and forestry resource mapping, geological mapping, mineral exploration and supply of data for geographic information systems. The DAIS sensor covers the spectral range from the visible to thermal infrared wavelengths at variable spatial resolutions from 2 - 30 m. Therefore, DAIS can also be used for the investigation of specifications for future airborne and spaceborne optical instruments for specific applications.

Preprocessing for the digital airborne imaging spectrometer DAIS 7915

The digital airborne imaging spectrometer DAIS 7915 is a new hyperspectral scanner developed for scientific and commercial applications. The design of the sensor makes a dedicated preprocessing necessary, prior to any data evaluation. Therefore, a facility is being developed at DLR to fulfill the needs of operational preprocessing. Besides that this facility is used for continuous quality control to support the hardware team in improving the performance of the instrument. The implementation of the software and the algorithms currently used are presented in this paper.

Analysis of LANDSAT TM images of Chernobyl

Abstract LANDSAT-5 TM images of the nuclear power plant of Chernobyl are analysed with the emphasis on estimating the reactor surface temperature. The investigation was done for TM channels 5 and 7 using the simulation model SENSAT developed at DFVLR. It accounts for the sensor characteristics (spectral response, IFOV) and target/background properties (size, temperature, emissivity). For the atmospheric part the LOWTRAN-6 model is used. The estimated surface temperature is 1000-1300 K for 29 April 1986, 3 days after the nuclear accident.

MOMS-02 sensor simulation and spectral band selection

Abstract MOMS-02 is a push-broom scanner with four spectral bands in the 450–810xa0nm region (each with a 15xa0m ground resolution element at a 310xa0km orbit) and a panchromatic (520–760xa0nm) stereo mode with on-track stereoscopic capability. The stereo mode employs three look angles: nadir (with a 5xa0m ground resolution element), 24° forward and backward (each with a 10xa0m ground resolution element). The sensor which is funded by the German Ministry for Research and Technology (BMFT) is scheduled for launch on a Space Shuttle mission at the end of 1991. The selection and radiometric performance of the panchromatic and the multispectral bands are discussed.

Fusion of airborne hyperspectral and multispectral images

The multi-sensor multi-resolution technique (MMT) was applied to fuse a multispectral image obtained by the multispectral scanner DAEDALUS-1268 with the resolution of 6 m and a hyperspectral image obtained by the imaging spectrometer DAIS-7915. The spatial resolution of the DAIS- 7915 image was additionally degraded to 24 m in order to simulate multi-sensor data fusion with a very different sensor resolution, as is typical for satellite sensors. Both sensors had been operated simultaneously on one aircraft. The MMT algorithm includes: (1) (unsupervised) classification of the multispectral image and mapping the classes with the high resolution of the multispectral scanner, (2) retrieval of the hyperspectral signatures of these classes from the hyperspectral image, and (3) generation of the merged image which combines the pixel size of the multispectral scanner and the spectral bands of the imaging spectrometer. Additional low-pass correction of the merged image allowed us to increase significantly its accuracy. The minimal pixel error of 6.9% was obtained when the classification was performed with 256 spectral classes.

Evaluation of GER airborne scanner data for environmental applications

In May/June 1989 the German Aerospace Research Establishment (DLR) Institute for Optoelectronics was involved in the first European Imaging Spectroscopy Airborne Campaign (EISAC). Test sites in various countries of the European Community were flown with the GER-Il Scanner. In the presented study the preprocessed and atmospherically corrected data was used for a spectral analysis of an old vegetation covered waste deposit. 2. THE GER-Il Scanner The GER-lI Scanner (Geophysical Environment Corp. ) is a 63 channel imaging spectrometer with three seperate line arrays of detectors which view the ground through the same aperture via a rotating mirror. It contains 31 channels in the visible I near infrared (VIS/NIR) wavelength region (470 nm - 840 nm sampling interval 12. 3 nm) 4 channels between 1440 nm to 1900 nm (sampling interval 120 nm) and another 28 channels in the short wave infrared (SWIR) wavelength region (2000 nm - 2450 nm sampling interval 16. 3 nm). The IFOV was selected to be 3. 3 mrad which leads to a pixel size of 10 m at 3000 m flying altitude. The high spectral and spatial resolution make this scanner a useful tool for environmental studies. 3. DATA PROCESSING As a first evaluation step the GER-Scanner data was preprocessed including a roll- lag- and slope-correction1. Comparison of ground vegetation spectra measured with the IRIS-Mark IV spectroradiometer (GER-Corp. ) during the time of the overflight yielded