The mysteries of comets

Main Theme Minor bodies of the Solar System
Mission Responsibility ESA
Launch Date 2 March 2004
End of mission December 2015
Current phase E2


Rosetta is the Cornerstone mission of the ESA Horizon 2000 program dedicated to the exploration of small bodies in the Solar System. It was launched on March 2, 2004, successfully carried out the fly-by of the asteroid Steins (2008) and performed a fly-by of the asteroid Lutetia on July 10, 2010, but its primary goal is to make a series of detailed investigations on the characteristics of the comet 67P/Churyumov-Gerasimenko, which reached in august 2014 and on which landed – with the lander Philae - in november of the same year.

Scientific Objectives
The main scientific objective of the mission is the understanding of the origin of comets and the relationship between their composition and interstellar matter as fundamental elements, in order to trace the origins of the Solar System. The search of intact material is obtained through the cometary exploration since the outer reaches of the Solar System contain material rich in volatiles that have not been processed in internal areas characterized by high temperatures.

The exploration of the comet consists in the characterization of its nucleus and the coma, the determination of their dynamic properties, and the study of the morphology and composition. In particular, the study of mineralogy and isotopic ratios of volatile and refractory elements of the core will provide valuable information on the composition of the nebula that, in current models, is thought to have been the origin of the Solar System.
To achieve these objectives, the spacecraft will orbit around the comet, following it on its journey into the interior of the planetary system, and the lander Philae will carry out in-situ measurements and sample the material on the surface of the nucleus for a detailed chemical-mineralogical analysis.

Italian contribution
The Italian participation in the ROSETTA mission consists of three scientific instruments of the orbiter: VIRTIS (Visual and InfraRed Thermal Imaging Spectrometer) the PI of which is Dr. Fabrizio Capaccioni of the IAPS (INAF Rome), GIADA (Grain Impact Analyser and Dust Accumulator) the PI of which is Dr. Alessandra Rotundi of the "Parthenope" University of Naples and the WAC (Wide Angle Camera) of OSIRIS of Prof. Cesare Barbieri, University of Padua (PI Dr. Uwe Keller, MPInstitute fur Sonnensystem). Aboard the lander, there is the Italian samples acquisition and distribution system (SD2), made by Galileo Avionica and whose PI is Prof. Amalia Ercoli Finzi, Polytechnic of Milan, and the subsystem of solar panels (Polytechnic of Milan). Italy has also provided the manpower to the Lander Project Team.

VIRTIS (Visible and InfraRed Thermal Imaging Spectrometer): combines 3 observation channels in a single instrument, two of which will be used in the reconstruction of the nucleus’s spectral map. The third channel is dedicated to high-resolution spectroscopy. With these observations an attempt to trace the nature of the solid parts that make up the nucleus of the comet will be made and to trace its thermal characteristics. These data, combined with data collected by other means, will be used to select the area on which to set down the lander.

GIADA (Grain Impact Analyser and Dust Accumulator) is an instrument capable of analysing the dusts and small grains of material present in the comet's coma measuring their physical and dynamic properties, including the size, the relationship between the granular and the gaseous material, and the speed of the particles.

OSIRIS/WAC (Optical, Spectroscopic, and Infrared Remote Imaging System): OSIRIS is the main instrument of the Rosetta mission to collect images of the comet. It consists of two channels: NAC (Narrow Angle Camera), optimized to obtain high-resolution maps of the comet’s nucleus, up to 2 cm per pixel, with an ability to focus from 2 km to infinity and from 1 to 2 km; WAC (Wide Angle Camera), which is optimized to obtain a high-resolution panoramic map of the gaseous material and dust in the vicinity of the comet’s nucleus.
OSIRIS’s WAC channel is the Italian responsibility and is designed for the accurate study of the comet‘s gaseous emissions, both visible and in UV band. The images captured by this channel will be used to select the area where the lander will be put down.

The following Italian systems are present aboard the Rosetta lander:

SD2Sample Drill&Distribution: SD2 represents an element of high miniaturization, condensing high performance technologies in just 4 Kg. SD2 is able to withstand the prohibitive environmental conditions in which it will operate while seeking to penetrate the nucleus of the comet up to a depth of 20 cm. A sophisticated mechanism will allow to distribute the samples collected (diameter of approx. 2.5 mm) in special containers so as to make the study of the properties possible through some of the instruments aboard the lander. The operation of the SD2 system is managed by sophisticated software installed on the lander’s on-board computer.
Another "Made in Italy" element is the Solar Array consisting of high-efficiency solar cells able to ensure the required electrical power even at distances greater than 2 AU from the Sun.

International agreements
With regard to the Philae lander, an International Consortium was created of which the ASI is a part; in addition to the construction of SD2 and the Solar Array (SA), the ASI has co-managed the project through a Deputy Project Manager, attended the Steering Committee and provides support for the system and subsystems activities on the lander.