MEASURING TRACE GASES IN PLUMES FROM HYPERSPECTRAL REMOTELY SENSED DATA

摘要

Characterizing surface and atmospheric properties from hyperspectral imaging spectrometry is of major importance in earth sciences. It has been successfully applied to geological, aquatic, ecological and atmospheric research (Curran, 1994) (Goetz, 1992). Hyperspectral sensors (e.g., AVIRIS, HyMap, Hyperion) are passive earth-looking systems providing radiance images in the solar reflected portion of the electromagnetic radiation spectrum. Generally, they cover a spectral range included in the 400-2500 nm window with a few hundred contiguous bands about 10 nm wide. The nominal pixel size is about 20 m. Typical signal to noise ratios (SNR) are a few hundred. As an example, the AVIRIS spectral range is 400-2500 nm, the number of bands is 224, the spectral bands are about 10 nm wide, the spatial resolution is about 20 m, and the SNR is between 300 and 800 for the year 1995. The images depend on sun irradiance, atmospheric conditions, ground conditions, and on the system's transfer function in a complex way (scattering, absorption, reflection, averaging), leading to a strongly non-linear pixel equation (3). Fig. 1 shows a diagram of the hyperspectral observational geometry.