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Y. Ghomchi, P. Drossart, A. Sémery, D. Tiphène (DESPA, Paris Obs.), A. Coradini, F. Capaccioni (IAS, Frascati), G. Arnold, J. Benkhoff (DLR, Berlin), VIRTIS Team
VIRTIS, the Visible and Infrared Thermal Imaging Spectrometer for the {\em ESA/Rosetta} mission, is a visible/infrared imaging spectrometer (Coradini et al., {\em Planet. Space Sci.}, 46, 1291; 1998), devoted to multispectral analysis of the cometary nucleus, the coma, and the dust environment of comet P/Wirtanen, the target of the Rosetta mission, during and after the coma development along the cometary orbit. The Virtis-M channel is an imaging spectrometer from 0.25 to 5~\mum at medium spectral resolution, and the Virtis-H channel, described here reaches a high spectral resolution (about 1500) in a single aperture from 2 to 5~\mum. The optics is a cross dispersing prism and a flat diffraction grating, producing a full spectrum splitted into several grating orders in the range 2--5~\mum (10 in the development model, 8 in the flight model), with a resolution of 1500 in average. The optics is radiatively cooled to 130~K and the detector is actively cooled down to 70~K.\\
A development model of VIRTIS H has been built and tested in DESPA, for optical and electronics testing. During the tests, a Rockwell TCM 3100 detector (HgCdTe, Buffered Direct Injection, size 320 x 240 pixels) has been used for engineering development, with a size smaller than that retained for the flight design. Observations have been made in white light on a point source, to make estimates of the optical properties of the design. Spectral absorption by a methane gas cell have allowed us to measure the spectral resolution. The performances of the optical system have been found to be conform to the specifications.\\
For the flight model of VIRTIS-H, HgCdTe infrared detector arrays with 435 x 270 pixels were developed by Raytheon (IR Center of Excellence). CTIA multiplexer have as much as 2 106 e- full well capacity, with pixel size of 38~\mum (square) and high sensitivity at low fluxes. This detector is currently under characterization, and the latest tests of performances in laboratory will be presented.
If you would like more information about this abstract, please follow the link to http://servirtis.obspm.fr/virtis.html. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.
The author(s) of this abstract have provided an email address for comments about the abstract: Pierre.Drossart@obspm.fr