April 25, 2017


(Visible and InfraRed Thermal Imaging Spectrometer)

VIRTIS-OM seen here in the calibration chamber
VIRTIS-ME can be seen underneath © LESIA

VIRTIS was a visible light and infrared imaging spectrometer originally developed for Rosetta. It operated in near ultraviolet, visible light, and infrared (with a wavelength range of 0.25 to 5 µm). The instrument combined regular low-resolution spectral mapping (VIRTIS-M) using two focal planes (UV/visible light and infrared CCD) with high-resolution spectrometry (VIRTIS-H) using a 2 to 5 µm infrared detector. VIRTIS was designed to analyse every layer of Venus’s atmosphere and cloud cover, measure surface temperature and study interactions between the surface and the atmosphere.

Principle of functioning of the instrument Virtis

VIRTIS provided a complete mosaic image of Venus’s disc as observed from the satellite’s apoapsis. The Venus Express spacecraft’s orbit configuration placed it above the planet’s southern pole to make these observations. This area had never been observed directly by any previous spacecraft. A meteorological survey of the atmosphere from various altitudes was carried out. As the satellite neared its periapsis, it was able to perform observations of the surface and the atmosphere, particularly above areas exhibiting evidence of volcanic activity detected by the Magellan mission.

CNR-IASF and LESIA were Co-PI on the VIRTIS instrument. LESIA’s main responsibilities were developing the VIRTIS-H high-resolution channel from spare subsystems leftover from the Rosetta mission, and elaborating mission scenarios for the experiment. The IAS was in charge of calibrating VIRTIS.

VIRTIS main specifications

 Mapper subsystemHigh-resolution subsystem
 Visible channelInfrared channelInfrared channel
Spectral range (µm)0.25 - 1.01 - 52 - 5
Maximum spectral resolution (nm)~2~10~3
Spectral resolving power (/)100 - 200100 - 2001,000 - 2,000
Spatial resolution1.0 (default)
0.25 (high)
1.0 (default)
0.25 (high)