NASA selects asteroid sample site for OSIRIS-REx
NASA has made its final selection of the site on asteroid Bennu where the space agency's Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-Rex) unmanned deep space probe will collect a sample for return to Earth. The site, designated "Nightingale," was chosen after a year of analyzing four candidate sites for the one that best balances scientific value against safety.
According to Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona in Tucson, Arizona, the OSIRIS-Rex team spent months comparing the Sandpiper, Osprey, Kingfisher, and Nightingale sites to find the one with the most fine-grained material that could be the most easily accessed. Of these, Nightingale came out as the front runner.
Nightingale is in a far northern region of the asteroid, which has a lower temperature and is in a relatively young crater 460 ft (140 m) across, where the surface material is likely well-preserved. This will give scientists a better view of Bennu's history. However, the crater has a smaller safe area for the probe to touch down than the planners would like and there is a large boulder present on the eastern rim, so OSIRIS-Rex will have to approach and back out with great care.
OSIRIS-Rex operates autonomously and is programmed to retreat from the sampling site if its onboard computer concludes it's too hazardous. If it's determined that a second attempt isn't possible, the spacecraft will be ordered to move to the Osprey backup site.
Now that the primary site has been chosen, Mission Control will now concentrate on more detailed surveys of the two sites, followed by rehearsals and the actual sampling attempt in August 2020. OSIRIS-Rex will then depart for Earth in 2021 for an arrival home in September 2023.
"Bennu has challenged OSIRIS-REx with extraordinarily rugged terrain," says Rich Burns, OSIRIS-REx project manager at NASA’s Goddard Space Flight Center. "The team has adapted by employing a more accurate, though more complex, optical navigation technique to be able to get into these small areas. We'll also arm OSIRIS-REx with the capability to recognize if it is on course to touch a hazard within or adjacent to the site and wave-off before that happens."