Launched by an Atlas V 411 rocket, OSIRIS-REx is the first NASA mission whose objective is to bring back to Earth an asteroid sample.
The target asteroid is the NEO Bennu (1999 RQ36), a primitive body with a diameter of ab out 500m.
Its orbit crosses that of the Earth, and it is a member of a potentially dangerous family of asteroids, whose probability of colliding with the Earth is small (0,037%) towards the XXIInd century.
Bennu is an asteroid rich in organic material, hardly changed since the formation of the Solar System. The mission objective is thus to better understand the formation of the Solar System, the nature and composition of these primitive asteroids which could have enriched the Earth in organic material and contributed to the birth of life ; another objective is also to study the non-gravitational forces which act on such small bodies and could alter their orbits.
The probe will take about 2 years to reach its target, and after various approach maneuvers in August 2018, OSIRIS-REx will begin a detailed study of Bennu for two years, after which a sampling process will be planned.
OSIRIS-REx carries various scientific instruments : three cameras, three spectrometers, and an altimeter to map the asteroid in the visible, infra-red and X-ray spectral domains.
OSIRIS-REx will come close to the surface of Bennu, but will not land, and will deploy a three meter long robotic arm in order to gather over 60 grams of dust from the surface.
This instrument is called TAGSAM : a perforated disc will be placed on the surface, after which a blast of nitrogen gas through the holes will raise and gather up) the regolith. The sample will be stored in a capsule similar that of the space probe STARDUST, and will be brought back to Earth in September 2023.
The capsule will land in the Utah desert (USA) in 2023 and the primitive material will be studied in detail and studied in the laboratory during the following years.
Scientific Contributions
The OSIRIS-REx mission is led by Dante Lauretta (PI), from the University of Arizona. The CNES is collaborating with NASA on this mission.
French scientists are participating in this mission.
In particular, various members of the Laboratoire d’études spatiales et d’instrumentation en astrophysique (LESIA - laboratory for space studies and instrumentation in astrophysics) from the Paris Observatory (co-investigators and associated scientists) have been collaborating actively with the OSIRIS-REx scientific team for the last 8 years, and are eagerly awaiting the first data.
The LESIA team involved in OSIRIS-REx includes :
A. Barucci, S. Fornasier, F. Merlin, C. Lantz and M. Fulchignoni.
The LESIA team has been working for 8 years on the scientific objectives of the OSIRIS-REx mission.
This collaboration is the fruit of collaborative work carried out in the context of studies for the ESA Marco Polo mission (Cosmic Vision).
The LESIA scientists were studying the physical, chemical and morphological characteristics of the target (the Bennu asteroid), well before the launch of the probe. In order to determine its thermal characteristics ; Bennu has been studied from the ground and from space using the HERSCHEL space telescope (using the the PACS instrument).
Laboratory analyses of irradiated "carbonaceous chondrite" type meteors have shown that there is a correlation between the radiation dose (the time during which there were changes, thus the age of the surfaces) and the initial composition of these primitive bodies ;
A model was thus developed, which links asteroid observations to the laboratory work, in order to understand how the surface of Bennu reacts to space weathering.
The LESIA team developed the « SpWe color imaging data products » algorithm for the « Regolith Development/Global Space Weathering Map ».
Its current role is to characterize the surface composition of the target asteroid, to study the processes which lead to changes, and to participate in the selection of a site for sampling.