SIMVEX 2001 trial - spectral IR measurements
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The ship signature model ShipIR/NTCS has been selected as a NATO standard. In 2001 several nations, including Norway, participated in the SIMVEX field trial arranged by NATO in Canada for validation of this model. The measurements were performed on a research vessel under different meteorological conditions, when the ship was sunlit and shaded, and also at night. Knowledge of the spectral distribution of signatures is essential when comparing images acquired with different IR cameras. This report presents spectral results from our high resolution FTIR spectroradiometer, Bomem DA5. Most of our measurements were made with a resolution of 0.5 wavenumbers. Using in-house software that enables correction of non-ideal properties of the spectroradiometer, we obtained improved absolute precision of calibrated spectra. The FTIR results are most interesting for sources with strong spectral variations, like the ship's plume, sunlit surfaces and sea and sky backgrounds. We also measured the ship in positions giving specular sun reflection. Sea and sky backgrounds were measured at different elevations, and the sea spectra show a significant contribution from sky reflection. Results from our spectral measurements have been compared with ShipIR/NTCS predictions. By comparing the results from plume measurements with simulated spectra, using the Fascode atmospheric model, we have estimated the plume temperature and the concentration of the most important IR contributing molecules.