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Visible Infrared Thermal Imaging Spectrometer (VIRTIS)

NSSDCA ID: 2004-006A-02

Mission Name: Rosetta
Principal Investigator:Dr. Fabrizio Capaccioni

Description

The Visible Infrared Thermal Imaging Spectrometer (VIRTIS) instrument on the Rosetta spacecraft has as its primary scientific objectives to study the cometary nucleus and its environment, to determine the nature of the solids of the nucleus surface, to identify the gaseous species, to characterise the physical conditions of the coma, and to measure the temperature of the nucleus. Other objectives include helping with the selection of landing sites, providing support to other instruments and detection and characterization during asteroid flybys. VIRTIS consists of two channels: VIRTIS-M, which provides high spatial resolution visible and infrared imaging in the 0.25 to 5 micrometer range at moderate spectral resolution, and VIRTIS-H, providing high-resolution spectroscopy in the 2 to 5 micrometer range.

The VIRTIS instrument is mounted at the base of the instrument deck. The instrument is divided into four subsystems: a main electronics module, a power supply, two proximity electronics modules (one for each spectrometer), and the optics module, which houses the two spectrometers and optical systems in a cold box and two Stirling cycle cryocoolers (one for each channel) in a section mounted directly on the spacecraft and thermally insulated from the cold box called the pallet. The cryocoolers maintain the cold box at approximately 130 K and dissipate heat through the spacecraft body. The cold box is connected to the pallet by 8 titanium rods. Both VIRTIS-M and VIRTIS-H have covers which act as protection against dust contamination and provide internal calibration by means of a reflecting surface finish on the inside of the cover.

VIRTIS-M is an Offner imaging spectrometer with a silicon 256 x 388 pixel CCD to image from 0.25 to 1.05 micrometer (visible) and a mercury cadmium telluride infrared 256 x 412 pixel focal plane array cooled to 70 K to image from 1 to 5 micrometers. The optical system consists of a Shafer telescope, which is an inverted Burch telescope and an Offner relay. The pupil diameter is 50 mm, the imaging F# is 5.8 (visible) and 3.2 (IR), and the slit dimension is 40 micrometers x 10 mm. The spot diameters are less than 6 micrometers at +/- 1.8 degrees.

VIRTIS-H is a high-resolution infrared cross-dispersed echelle spectrometer. The 2 to 5 micrometer spectrum is dispersed in 10 orders on a 240 x 640 pixel mercury cadmium telluride infrared focal plane array. Light is guided by two off-axis parabolas through a cross-dispersing lithium flouride prism to a flat diffraction grating which separates orders 7 through 16 across the focal plane array. Spectral resolution varies in each order from 1200 to 3500. The pupil diameter is 36 mm, the objective is F/1.67, and the slit dimension is 28 x 142 micrometers.

Alternate Names

  • Rosetta/VIRTIS
  • VIRTIS
  • urn:esa:psa:context:instrument:ro.virtis

Facts in Brief

Mass: 23 kg

Funding Agency

  • European Space Agency (International)

Discipline

  • Planetary Science: Small Bodies

Additional Information

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

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Fabrizio CapaccioniPrincipal InvestigatorInstitut d Astrophysique SpatialeFabrizio.capaccioni@iaps.inaf.it

Selected References

  • Coradini, A., et al., VIRTIS: An imaging spectrometer for the ROSETTA mission, Planet. Space Sci., 46, No. 9/10, 1291-1304, doi:10.1016/S0032-0633(98)00025-7, 1998.
  • Coradini, A., et al., VIRTIS: The imaging spectrometer of the Rosetta mission, Adv. Space Res., 24, No. 9, 1095-1104, Aug. 1999.
  • Bonello, G., et al., The ground calibration setup of OMEGA and VIRTIS experiments: description and performances, Planet. Space Sci., 53, No. 7, 711-728, doi:10.1016/j.pss.2005.02.002, Jun. 2005.
  • Coradini, A., et al., Virtis: An Imaging Spectrometer for the Rosetta Mission, Space Sci. Rev., 128, 529-559, doi:10.1007/s11214-006-9127-5, 2007.
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