VIRTIS-H: a high spectral resolution channel for the Rosetta Infrared Imaging Spectrometer

摘要

VIRTS, the infrared imaign spectrometer of the ESA/ROSETTA mission~1, to be launched in January 2003, is devoted to the in-orbit remote sensing study of comet P/46 Wirtanen. Within the infrared imaign spectrometer VIRTIS~2, the high spectral resolution channel, VIRTIS-H, has for main scientific objectives to study the fine spectral details of the coma and cometary nucleus,with their composition and physical parameters, in parallel with the imagign spectrometer channel VIRTIS-M~3. The instrument is a cross-dispersor spectrometer, working in the range 2-5 mum, at about approx1200 spectral resolving power. Its design consists of a telescope,a n entrance slit, followed by a collimator, and a prism separating 8 orders of a grating. An objective focuses the spectrum on the FPA. The echelle spectrum is recorded on a 270x436 infrared HgCdTe array from Raytheon/IRCOE. The temperature of the FPA is maintained at 70 K by active cooling, and the optics is radiatively cooled at 130 K. Results from the development model of VIRTIS confirm the expected performances, with laboratory spectra of gas cells and mineralogical samples as a testbed. In particular, a methane cell provides spectra at 3.3 micrometers for the purpose of performing the spectral calibration.