MIRO (Microwave Instrument for the Rosetta Orbiter):
Used to determine the abundances of major gases, the surface outgassing rate and the nucleus subsurface temperature. It will also measure the subsurface temperatures of Siwa and Otawara, and search for gas around them.
The Orbiter's scientific payload includes 11 experiments, in addition to the Lander. Scientific consortia from institutes across Europe and the United States have provided these state-of-the-art instruments. All of them are located on the side of the spacecraft that will permanently face the comet during the main scientific phase of the mission.