VIRTIS
VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) is designed to analyze and map the composition of comet 67P/Churyumov-Gerasimenko, and to measure temperature variations. VIRTIS combines a a spectro-imager (VIRTIS-M) with a n echelle spectrograph (VIRTIS-H) ; this is an optimal combination for the study of surface variations and the subtle signatures of the atmosphere and the ices. The instrument was created by a consortium of Italian, French and German laboratories.
VIRTIS-M will obtain spectra in the visible domain (0,25-1 µm) and in the infra-red (1-5 µm). The spectral dispersion is along one of the dimensions of the detectors, which the other dimension furnishes an image of entrance slit divided into 256 pixels. The motion of the probe along its path enables a second spatial direction to be swept. This channel has been designed for systematic mapping, with a spectral resolution (R = 200) such that minerals and ices can be studied.
VIRTIS-H uses a prism and a grating. The 2-5 µm spectral range is dispersed into eight orders. Since the two dimensions of the detector are already used up for the spectral dispersion, this channel can acquire only one spectrum at a time. The resolution (R = 1500-3000) has been chosen for the study of the coma and the nucleus : it enables the H2O and CO2 lines to be distinguished, and to resolve the signatures of organic matieral.
Takin from the Agenda astronomique 2014, Institut de mécanique céleste et de calcul des éphémérides de l’Observatoire de Paris, EDP sciences, p. 74
MIRO
MIRO (Microwave Instrument for the Rosetta Orbiter) is an instrument for the (sub)mllimetre domain. It is made up of a small 30 cm radiotelescope and two heterodyne receivers for 1,6 mm and 0,5 mm wavelengths. The two channels measure the thermal emission from the immediate subsurface layers (depths ranging from a few millimetrres to about ten centimetres) of the nucleus. The 0,5 mm channel is moreover coupled to a high resolution spectrometer, which enables the esmission of various gases in the coma (water vapour and its isotopes, carbon monoxide, ammonia and methane) to be measured. The scientific objectives are thus to determine, to map and to follow through time the temperature of the nucleus, the emission rates of the gasses, and the physical conditions in the coma. This will lead to a better understanding of the nature and the mechanisms governing cometary activity.
Totalling a mass of 20 kg, MIRO was constructed in partnership with the Jet Propulsion Laboratory in California, the Paris Observatory, and the Lindau Max-Planck Institute in Germany. It has already been shown to work perfectly during Rosetta’s flybys of the Earth and the asteroids Steins and Lutetia.
Taken from the Agenda astronomique 2014, Institut de mécanique céleste et de calcul des éphémérides de l’Observatoire de Paris, EDP sciences, p. 84
OSIRIS
OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) is a two camera system on board the Rosetta probe. This imaging system is vital for the success of the Rosetta mission.
OSIRIS will observe comet 67P/Churyumov-Gerasimenko, establish ist shape, its volume, and will help to determine where best to place the lander Philae. OSIRIS will observe the nucleus, its activity and its environment down to a scale of several centimetres.
Observations will begin while the comet is still hardly active and will continue until the comet has reached perihelion. OSIRIS will furnish key information on the nature of cometary nuclei and, more generally, on cometary physics (the gas and dust coma).
OSIRIS is made up of a narrow field (NAC) and high angular resolution camera, and of a wide field camera (WAC), associated with three electronics units. The NAC has been designed to obtain high resolution images of the surface of comet 67P/Churyumov-Gerasimenko through eleven filters covering the wavelenth range 250-1000 nm. The WAC has been optimized to obtain images of the immediate environment of the nucleus, through fourteen filters covering the same wavelength range, but with different wavelengths. The two systems use identical shutters, filter wheels, entry ports and detection systems. They are piloted by a common data processing unit. The total mass of sthe OSIRIS instrument is 35 kg, and it was developed by six Eurpean countries and space agencies (France, Italy, Spain, Sweden, Germany and ESA).
Since 2005, the camera has observed comet 9P/Tempel 1 (the Deep Impact event), the Earth, Mars, the asteroids Steins and Lutetia, and comet 67P from a distance of 1 au (March 2011).
Taken from the Agenda astronomique 2014, Institut de mécanique céleste et de calcul des éphémérides de l’Observatoire de Paris, EDP sciences, p. 46