Yesterday, the OSIRIS REx spaceships performed their last practice run of the sampling sequence and reached an approximate height of 40 meters (40 meters) above the Nightingale test site before performing a backfire. Nightingale, OSIRIS-REx’s primary sample collection site, is located within a crater in Bennus’ northern hemisphere.
The approximately four-hour “Matchpoint” test took the spaceship through the first three of the sampling sequence’s four maneuvers: progress burn, the “Checkpoint” burn, and the Matchpoint burn. Checkpoint is the point where the spacecraft autonomously checks its position and speed before adjusting its trajectory to the event’s third maneuver. Matchpoint is the moment when the spacecraft matches Bennus’ rotation to fly in tandem with the asteroid surface, directly above the test site, before touching the targeted site.
Four hours after leaving its 0.6 km (1 km) safe home track, OSIRIS-REx performed the checkpoint maneuver at an approximate height of 125 meters above Bennus’ surface. From there, the spaceship continued to sink for another eight minutes to perform the Matchpoint firing. After sinking on this new orbit for another three minutes, the spaceship reached a height of about 40 m – the closest spacecraft ever has been the Bennu – and then performed a backward burn to complete the rehearsal.
These images were taken over a period of 13.5 minutes. The image sequence begins approximately 420 feet (128 meters) above the surface – before the spaceship performs the “maneuver” Checkpoint – and goes through the “Matchpoint” maneuver, with the last image taken approximately 144 feet (44 meters) above the surface of Bennu. The spacecraft’s sampling arm – called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) – is visible in the lower part of the frame. point: NASA/ Goddard / University of Arizona
During the rehearsal, the spaceship successfully sent its sampling arm, the Touch-And-Go Sample Acquisition Mechanism (TAGSAM), from its folded, parked position out to the sample collection configuration. In addition, some of the spacecraft’s instruments collected scientific and navigational images and made spectrometry observations of the test site, which will occur during the test collection event. These images and scientific data were linked to Earth after the event ended.
Since the spacecraft and Bennu are currently approximately 179 million miles (from 288 million km) from Earth, it takes approximately 16 minutes for the spacecraft to receive the radio signals used to command it. This time delay prevented direct command of flight activities from the ground during repetition. As a result, the spacecraft performed the entire repetition sequence autonomously. Before the start of the rehearsal, the OSIRIS-REx team connected all the event commands to the spacecraft and then provided the “Go” command to start the event. The actual sample collection in October will be conducted in the same way.
This second repetition gave the mission team practice navigating the spaceship through the first three maneuvers of the sampling event and an opportunity to verify that the spacecraft’s imaging, navigation, and range system worked as expected during the first part of the descent sequence.
The Matchpoint rehearsal also confirmed that OSIRIS-REx’s Natural Feature Tracking (NFT) guidance system accurately estimated the spacecraft’s trajectory after the Matchpoint firing, which is the last maneuver before the sample collection head comes in contact with Bennus’ surface. This repetition was also the first time that the spacecraft’s boarding pass was used. The danger map delimits areas that could potentially damage the spacecraft. If the spacecraft detects that it is about to touch a dangerous area, it will autonomously back away when it reaches a height of 5 m. would have avoided surface risk, and found that the spacecraft’s path during the rehearsal would have enabled a safe touchdown on the test site Nightingale.
During the last minutes of the spacecraft’s descent, OSIRIS-REx also collected new, high-resolution navigation images for the NFT control system. These detailed images of Bennus landmarks will be used for the sampling event and will allow the spaceship to really focus on a very small area.
“Many important systems were exercised during this rehearsal – from communications, spacecraft, and most importantly, the onboard Natural Feature Tracking guidance system and hazard map,” said OSIRIS-REx Chief Investigator Dante Lauretta at the University of Arizona, Tucson. “Now that we have made this milestone, we are convinced to complete the procedures for the TAG event. This rehearsal confirmed that the team and all the spaceship systems are ready to collect a sample in October. “
The mission team has spent the last few months preparing for Matchpoint rehearsal while maximizing remote work as part of covid-19 response. On the rehearsal day, a limited number of employees monitored the spacecraft’s telemetry from Lockheed Martin’s facility, NASA’s Goddard Space Flight Center and the University of Arizona, with appropriate security measures, while the rest of the team performed their roles remotely.
The spacecraft will travel all the way to the asteroid’s surface during its first provincial gathering attempt, scheduled for October 20. During this event, the OSIRIS-REx sampling mechanism will touch Bennus’ surface for several seconds, fire a charge of nitrogen under pressure to disrupt the surface, and collect a sample before the spacecraft backs away. The spacecraft is scheduled to return the sample to Earth September 24, 2023.
NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides comprehensive mission management, systems engineering, and security and mission insurance for OSIRIS-REx. Dante Lauretta from the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the scientific team and the mission’s scientific observation planning and computing. Lockheed Martin Space in Denver built the spacecraft and provides flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington.