NASA’s OSIRIS-REx Executes Low-Altitude Flyover of Asteroid Landing Site


NASA’s OSIRIS-REx probe is about to make history, but the agency isn’t taking any chances. In the coming months, OSIRIS-REx will descend to the surface of the asteroid Bennu to pick up a sample, but NASA wants to get a closer look at the area before sending the spacecraft swooping down. OSIRIS-REx has just completed its lowest pass over the site yet, just 820 feet (250 meters) from the surface. 

The scientists behind OSIRIS-REx were met with the same problem as JAXA researchers running Japan’s Hayabusa2 mission: asteroids are much less smooth than we expected. The surfaces of both space rocks are strewn with boulders and outcroppings that could cause damage to a space probe attempting to reach the surface. Hayabusa2 eventually found a place where it could tap the surface and scoop up a few grains of dust. However, OSIRIS-REx has to make contact for a longer time to collect as much as 2.1 ounces (60 grams) of material. 

Late last year, NASA identified several potential landing zones for OSIRIS-REx. After considering the options, a location called Nightingale won out. This gravel-covered pit near the asteroid’s north pole doesn’t have any major obstacles — the nearest hazard is a 23-foot-high (7-meter) boulder about 52 feet (16 meters) away from the center of the pit. The recent 5-hour flyover helped NASA verify the safety of this area. The probe left its 1-kilometer orbit and zipped across the surface to image Nightingale with its PolyCam camera. OSIRIS-REx also collected data on Nightingale with the OSIRIS-REx Thermal Emissions Spectrometer (OTES), the OSIRIS-REx Visual and InfraRed Spectrometer (OVIRS), the OSIRIS-REx Laser Altimeter (OLA), and the MapCam color imager.

NASA won’t get the smooth, open surface depicted in this picture. Bennu is covered in dangerous boulders.

OSIRIS-REx headed back into its standard orbit after the flyby, but it’s now orbiting in the opposite direction. That puts the spacecraft in position to execute its first landing rehearsal next month. It’s vital the probe gets this right — Bennu is far enough from Earth that NASA cannot control OSIRIS-REx in real-time. That means the landing and sample acquisition need to be fully automated. A second rehearsal will happen in June, taking OSIRIS-REx even closer to the surface. If everything goes as planned, OSIRIS-REx will pick up its asteroid sample in August 2020. 

NASA hopes to have the sample from OSIRIS-REx back on Earth in September 2023. A few ounces of Bennu could revolutionize our understanding of the solar system, but OSIRIS-REx has to get this landing right.

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