NASA’s OSIRIS-REx mission will descend to the surface of asteroid Bennu later this summer to collect a sample of material. In preparation for that moment, the team completed a 4-hour rehearsal on April 14 to test the safety of OSIRIS-REx as it departed its current orbit of about 1 kilometer (0.6 miles) above Bennu. The rehearsal allowed the mission team an opportunity to check that the system's imaging, ranging, and navigation were working properly.

On its way down, OSIRIS-REx deployed its Touch-And-Go Sample Acquisition Mechanism (TAGSAM), essentially its robotic sampling arm. When the spacecraft reached the 120 meters (395 feet) checkpoint altitude, solar arrays that power the spacecraft moved into a Y-wing position so that they were safely away from Bennu’s surface. The change put the center of mass right on the TAGSAM, which will be the only part of the spacecraft that will eventually touch the surface of Bennu.

In the rehearsal, OSIRIS-REx reached an altitude of 65 meters (213 feet), the closest it has ever been to the asteroid. It then executed a back-away burn and the solar arrays returned to their standard position, the TAGSAM retracted, and the craft flew back to its original orbit. This is only the first of two rehearsals. The second one is scheduled for June 23, with OSIRIS-REx expected to descend as low as 25 meters (82 feet). The spacecraft’s first official attempt to sample material is scheduled for August 25.

Once the sample is collected, OSIRIS-REx will continue to study Bennu from orbit until 2021. At the opportune moment, the spacecraft will fire up its engine and set a course for Earth. It should arrive back to Earth with the sample in September 2023.

Several NASA mission milestones have been affected by COVID-19 precautions, but the OSIRIS-REx mission is currently not among them.