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Visible and Infrared Thermal Imaging Spectrometer (VIRTIS)

NSSDCA ID: 2005-045A-02

Mission Name: Venus Express
Principal Investigators:Mr. Pierre Drossart
Principal Investigators:Dr. Giuseppe Piccioni


The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) is an imaging spectrometer combining two subsystems, a mapping spectrometer and a high resolution spectrometer, with three observing channels. It is designed to allow the analysis of all layers of the atmosphere and the clouds, make measurements of surface temperature and study surface / atmosphere interaction phenomena.

The mapping spectrometer subsystem is a Shafer telescope matched through a slit to an Offner grating spectrometer. The Shafer telescope consists of five aluminium mirrors mounted on an aluminium optical bench. The primary mirror is a scanning mirror driven by a torque motor. The Offner spectrometer consists of a relay mirror and a spherical convex diffraction grating, both made of glass. It has a field of view of 0.25 milliradians and consists of two channels. The visible channel uses a silicon charge coupled device (CCD) with a spectral range from 0.25 to 1.0 microns with a maximum spectral resolution of approximately 2 nanometers and a spectral resolving power (lambda/delta lambda) of 100 - 200. The CCD is operated at 155K. The infrared channel uses a mercury cadmium telluride (HgCdTe) infrared focal plane array (IRFPA) with a spectral range of 0.95 to 5 microns, maximum resolution of approximately 10 nm, and a resolving power of 100 - 200. The IRFPA is cooled to 70K by a Stirling cycle cooler.

The high resolution spectrometer subsystem is an echelle spectrometer. The incident light is collected by an off-axis parabolic mirror and then collimated by another off-axis parabola before entering a cross-dispersion prism. After exiting the prism, the light is diffracted by a flat reflection grating, which disperses the light in a direction perpendicular to the prism dispersion. It has one infrared channel using a HgCdTe IRFPA with a spectral range of 2 to 5 microns, a maximum resolution of about 3 nm, and a resolving power of 1000 - 2000. The field of view is 0.5 to 1.5 milliradians. The detector is cooled to 70K by a Stirling cycle cooler.

The optical subsystems are housed inside a cold box cooled to 130K by a radiative surface supported on a truss having low thermal conductivity. Two sets of electronics and two cryogenic coolers for the detectors are mounted on the pallet supporting the truss. The cold box is rigidly mounted on the pallet but thermally isolated from it. The pallet and cold box together form the optics module, which is mounted inside the spacecraft arranged so that the observing axes of the optical subsystems are normal to the nadir pointing wall of the spacecraft. The electronics module, containing the digital electronics and power supply, is mounted separately.

The Venus Express VIRTIS is based on the VIRTIS instrument flown on the Rosetta spacecraft.

Alternate Names

  • VenusExpress/VIRTIS


  • Planetary Science: Geology and Geophysics

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Mr. Pierre DrossartPrincipal
Dr. Giuseppe PiccioniPrincipal
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