MIRO (Microwave Instrument for the Rosetta Orbiter) is an instrument which works in the submillimre wavelength range.
Its purpose is to study the nature and the mecanisms underlying the activity of comet 67P/Churyumov-Gerasimenko.
The first results show that comet 67P/Churyumov-Gerasimenko sends into space the equivalent of two glasses of water (one glass = 150 ml) per second, even though it is still in a rather cold region of space 583 million de kilometres from the Sun.
These observations were made on June 6th last, when the probe was about 350000 kilometres from the comet.
The instrument’s PI, Sam Gulkis, indicated that the emission of water vapour by the comet was expected, but he was surprised that it was detected at such an early stage.
According to him, if the comet continues to degas at this rate, it could fill an olympic size swimming pool in about 100 days; he also considers that as the comet approaches the Sun, the rate of production of water vapour will increase significantly.
Water is an important volatile component of comets, as is carbon monoxide, methane and ammonia.
The purpose of MIRO is to find the abundance of each of these components
to understand the nature of cometary nuclei, the degassing process, and where it takes place on the cometary surface.
The structurre of MIRO
With a total mass of 20 kg, MIRO is made up of a small 30cm radio-telescopese and two heterodyne receivers working in the 1,6 mm and 0,5 mm wavelength range.
The two chennels measure the thermal emission of the immediate subsurface layers (depths ranging from a few millipetres to about ten centimetres) of the nucleaus.
The 0,5 mm channel is furthermore coupled to a high resolution spectrometer, for the measurement of the emission of various gases (water vapour and is isotopes, carbon monoxide
ammonia and methanol) in the coma.
The scientific objectives are thus to determine, map and follow over time the temperature of the nucleaus, the gaseous emission rates and the physical conditions in the coma.
MIRO was built in partneship with the Jet Propulsion Laboratory in Californie, the Paris Observatory - via the Laboratoire d’Etude du rayonnement et de la matière en astrophysique and the Laboratoire d’études spatiales et d’instrumentation en astrophysique - and the Lindau Max-Planck Institute in Germany.
It has worked successfully during Rosetta’s flybys of the Earth and the asteroids Steins and Lutetia.
ESEP participants
- LESIA : Jacques Crovisier, Dominique Bockelée-Morvan, Nicolas Biver, Emmanuel Lellouch, Cédric Leyrat, Thérèse Encrenaz
- LERMA : Pierre Encrenaz, Gérard Beaudin Participation technique (LERMA) : Maurice Gheudin, Jean-Michel Krieg, André Deschamps