Fast hyperspectral information production by AISA airborne imaging spectrometer.

The AISA airborne hyperspectral imaging spectrometer is an excellent tool for fast-paced, repetitive measurements. Key features of AISA are small size, low power consumption, affordability and fast turn-around-time in data processing. This makes it an excellent means of production for businesses in precision agriculture, environmental monitoring, water-quality studies and other fields where quickly changing, dynamic conditions have to be observed. The fast turn-around-time in data processing allows for delivery of processed data and images in typically less than 24 hours after initial measurement. AISA provides full programmability for wavelength range, channel selection and integration time even during flight. The default wavelength range of AISA is 430 - 900 nm with a spectral sampling of 1.63 nm at 450 nm The spectral resolution is 1.8 nm when using a 25 mm entrance slit. The field of view (FOV) of AISA is 20 degrees when using a 25 mm lens. Image swath width is 384 pixels, which includes data from the fiber-optic downwelling irradiance sensor (FODIS). A configuration with 60 spectral channels, full swath including FODIS, 52 ms integration time and 77 m/s (277 km/h) flight speed from a flight altitude of 4000 m above ground gives a raw pixel size of 4 m*4 m. An integrated GPS/INS unit with differential GPS capability, a three-axial inertial attitude sensor and real-time Kalman filtering for three-dimensional navigation solution processing is integrated with the AISA system. This provides one pixel accuracy for rectification and georeferencing of measurement data without using a stabilized platform. The output from the CaliGeo data processing software package is a radiometrically calibrated, rectified and georeferenced hyperspectral image or image mosaic. This image is ready for use in advanced data analysis and visualization systems. Apparent reflectance can also be calculated in CaliGeo using the downwelling irradiance data from FODIS.