The OSIRIS-REx spacecraft has completed its final practice run ahead of its mission set for October.
Located 179 million miles from Earth, Nightingale—OSIRIS-REx’s primary sample collection site—is located within a crater in Bennu’s northern hemisphere. It takes approximately 16 minutes for the spacecraft to receive the radio signals used to command it, so the entire rehearsal sequence must be performed autonomously rather than using live commands.
From Maryland, the team leads the spacecraft through the four-hour rehearsal, which consists of the first three maneuvers of the sampling sequence: the Orbit Departure burn, the Checkpoint burn and the Matchpoint burn.
The OSIRIS-REx spacecraft starts by reaching an approximate altitude of 410 feet above Bennu’s surface to check its position and velocity before adjusting its trajectory down toward the third maneuver. It then descends for eight minutes to perform the Matchpoint burn at 131 feet. The spacecraft matches Bennu’s rotation to fly in tandem with the asteroid surface and then hovers directly above the sample site for another three minutes to collect material.
Using its sampling arm, the Touch-And-Go Sample Acquisition Mechanism, the spacecraft collects asteroid material before executing a back-away burn to complete the rehearsal. It also collects science and navigation images as well as spectrometry observations of the sample site, which were both made available after the event.
This practice run was the closest the spacecraft has ever been to Bennu.
For the first time, the team employed the spacecraft’s onboard hazard map to detect areas that could potentially harm the spacecraft and autonomously back-away 16 feet from any hazardous areas. It was tested to predict if the touchdown trajectory would have avoided all surface hazards.
The team also confirmed if the spacecraft’s imaging, navigation and ranging systems will operate as expected and if the OSIRIS-REx’s Natural Feature Tracking guidance system will accurately estimate the spacecraft’s trajectory after the Matchpoint burn.
During the actual mission on October 20th, the OSIRIS-REx spacecraft will touchdown onto the asteroid for several seconds, fire a charge of pressurized nitrogen to disturb the surface, and collect a sample using the onboard hazard map to avoid all hazards. The Maryland team will lead the spacecraft by sending commands beforehand and then telling it to begin, just like during its rehearsals.
“Now that we’ve completed this milestone, we are confident in finalizing the procedures for the TAG event. This rehearsal confirmed that the team and all of the spacecraft’s systems are ready to collect a sample in October,” said OSIRIS-REx Principal Investigator Dante Lauretta of the University of Arizona, Tucson on NASA’s website.
The spacecraft is scheduled to return the sample to Earth on September 24, 2023.