IMAGING SPECTROSCOPY FOR 2-DIMENSIONAL CHARACTERIZATION OF AURORAL EMISSIONS

A large throughput transmission spectrometer, with a grating on a pris m as the diffraction element, has been developed to study altitude dis tributions of auroral emissions. The imaging spectrometer disperses sp ectrally in one dimension while spatial information is preserved in th e orthogonal direction. The image is projected onto a CCD array detect or. Image processing methods have been developed to calibrate for wave length, uniform field, spectral sensitivity, curvature of field, and s patial mapping. Single images are processed to represent a measured si gnal brightness in a unit of Rayleighs/pixel, from which area integrat ions can be made for desired spatial-spectral resolution. System perfo rmance is similar to 1.5-nm resolution over a 450-nm bandwidth (420-87 0 nm). Two spectrometer systems of this design were operated simultane ously, one with additional optical instruments and an incoherent scatt er radar at Sondrestrom, Greenland, and the other at Godhavn, Greenlan d, which lies 290 km to the northwest and nearly in the magnetic merid ian of Sondrestrom. The developed system, calibration method, and exam ples of performance results are presented. (C) 1998 Optical Society of America.