NASA is about to conduct an important rehearsal event for its asteroid-sampling spacecraft, OSIRIS-REx. The spacecraft is expected to reach its closest distance to its target, which is asteroid Bennu.
OSIRIS-REx was officially launched by NASA on September 8, 2016. Its main objective is to safely land on asteroid Bennu in order to collect samples from its surface. Once it has completed its objective, the spacecraft will take off from the asteroid to bring the samples to Earth.
Practicing OSIRIS-REx's descent
Given the asteroid's rotation and harsh terrain, landing on it is not an easy step. This is why on April 14, NASA will carry out a rehearsal for the descent stage of OSIRIS-REx. The rehearsal event, known as Checkpoint, will last for about four hours. It will involve bringing the spacecraft down from its safe-home orbit, which is about 1 kilometer above Bennu.
Then, at about 125 meters from the asteroid, the spacecraft will adjust its positioning and speed in preparation for its descent. It will then continue to descend towards the asteroid until it reaches the 75-meter mark, which will be the closest distance between the spacecraft and the asteroid.
Preparing for the actual landing
As noted by NASA, the Checkpoint will allow the team behind OSIRIS-REx to ensure that all of its instruments are functioning properly before embarking on the actual descent, which is scheduled for August 25. Specifically, the rehearsal will enable the team to test the spacecraft's navigation system known as Natural Feature Tracking (NFT)
Through the NFT, the spacecraft will be able to take photos of the asteroid's surface as it prepares to land. These images will be used by the system to make course-corrections and other adjustments for its descent on the asteroid. "Checkpoint rehearsal also gives the team a chance to confirm that OSIRIS-REx's Natural Feature Tracking guidance system accurately updates the spacecraft's position and velocity relative to Bennu as it descends towards the surface," NASA explained.
Checkpoint will serve as the first practice run for OSIRIS-REx's mission. NASA will conduct a second rehearsal on Jun. 23 before landing the spacecraft on the asteroid.