NASA's first asteroid sampling spacecraft is preparing for its final rehearsal before landing on the surface of asteroid Bennu to collect a sample.
OSIRIS-REx (Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer), which has been orbiting Bennu since 2018, is set to practice its final touchdown sequence on Aug. 11. before its official touchdown on the space rock in October.
The space probe, during the rehearsal, will practice the touch-and-go sample-collection sequence, which it did before last April when it performed the first two moves of the descent. OSIRIS-REx will attempt to perform a third maneuver called matchpoint burn, which will put the spacecraft closer to Nightingale -- the sample site -- than before.
Part of the third maneuver will involve OSIRIS-REx flying in tandem with Bennu's rotation for the first time. This should allow the team to perfect the move in leading the probe through the descent maneuvers. This final practice session also aims to test the spacecraft's navigation, imaging, and ranging systems, NASA said in a statement.
In addition to practicing the descent maneuvers, OSIRIS-REx will also be performing other sets of activities. Running at an average speed of 0.2 mph, the asteroid sampling probe will fire its thrusters three separate times during its descent to the asteroid's surface. The first will pull the spacecraft out of its 0.6-mile-high orbit around Bennu.
OSIRIS-REx will also attempt to achieve other milestones during the Aug. 11 rehearsal. This includes positioning its solar panels away from the surface of Bennu, gathering images for its autonomous navigation system, and extending its sampling arm.
OSIRIS-REx won't be able to descend toward the surface of Bennu until it reaches an altitude of 410 feet. Once it does, it will perform the checkpoint burn and should plummet toward the rock for approximately 9 minutes. When it reaches 164 feet above the asteroid, the thrusters will be fired three times and perform the matchpoint burn. During this move, the probe will start to slow its pace toward the surface and alight with the asteroid's rotation.
It will have to make its closest approach to Bennu, which should be 130 feet above Nightingale, before returning to orbit with a back-away burn. And if all goes well, OSIRIS-REx will remain in its orbit around Bennu until it travels all the way to the asteroid's surface during its first sample collection attempt on Oct. 20. The samples are planned for a 2023 return on Earth.
