This artist’s concept demonstrates the trajectory and configuration of NASA’s OSIRIS-REx spacecraft during Matchpoint’s rehearsal, which is the last time the mission will practice the initial steps of the sampling sequence before the asteroid Bennu touch. Credit: NASA / Goddard / University of Arizona
Yesterday, the OSIRIS-REx spaceship conducted its last practice match of the sampling sequence, reaching an approximate height of 40 meters (41 meters) over sample Nightingale before performing a backfire. Nightingale, OSIRIS-REx’s primary sample collection, is located inside a crater in the northern hemisphere of Bennu.
The nearly four-hour “Matchpoint” rehearsal took the spaceship through the first three of the four maneuvers of the sampling sequence: the fire away from the orbit, the “Checkpoint” fire, and the Matchpoint fire. Checkpoint is the point at which the spacecraft autonomously checks its position and velocity before adjusting the trajectory downwards after the third maneuver of the event. Matchpoint is the moment that the spaceship corresponds to Bennu’s rotation to fly in tandem with the surface of the asteroid, just above the sample site, before reaching the target location.
Four hours after leaving its 0.6-mile (1 km) safe home base, OSIRIS-REx performed the Checkpoint maneuver at an approximately 125-foot (125-meter) altitude above Bennu’s surface. From there, the spaceship continued to fall for another eight minutes to carry out the Matchpoint fire. After crashing for three minutes on this new trajectory, the spaceship reached a height of about 40 m – the closest the spacecraft has ever been to Bennu – and then carried out a backfire to complete the rehearsal.
These images were taken over a period of 13.5 minutes. The image sequence starts at about 128 meters above the surface – before the spacecraft performs the ‘Checkpoint’ maneuver – and continues to the ‘Matchpoint’ maneuver, with the last image made about 144 meters (44 meters) above the surface of Bennu. The space sampling arm – called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) – is shown in the lower part of the frame. Credits: NASA/ Goddard / University of Arizona
During rehearsal, the spacecraft successfully deployed its sampling arm, the Touch-And-Go sample acquisition mechanism (TAGSAM) from its folded, parked position to the sampling configuration. In addition, some of the instruments of space science have collected science and navigation imagery and made observations of spectrometry from the sample page, as will happen at the sampling event. These images and scientific data were downlinked to the conclusion of the event.
Because the spacecraft and Bennu are currently approximately 179 million miles (288 million km) from Earth, it takes approximately 16 minutes for the spacecraft to receive the radio signals used to command it. This time lapse prevented live command of flight activities from the ground during the rehearsal. As a result, the spacecraft performed the entire rehearsal match autonomously. Before the rehearsal began, the OSIRIS-REx team linked all of the event’s commands to the spaceship and provided the “Go” command to start the event. The actual sample collection event in October will be held the same way.
This second rehearsal provided the mission team with practice navigating the spaceship through the first three maneuvers of the sampling event and with an opportunity to verify that the spacecraft’s imaging, navigation and reach systems functioned as expected during the first part of the descent sequence.
Matchpoint rehearsal also confirmed that OSIRIS-REx’s Natural Feature Tracking (NFT) guidance system accurately estimates the spaceflight route to the Matchpoint fire, which is the final maneuver before the sample head comes into contact with Bennu’s surface. . This rehearsal was also the first time that the upcoming spaceship danger map was deployed. The danger map describes areas that could potentially damage the spaceship. If the spacecraft detects that it is on course to touch a dangerous area, it will autonomously decline once it reaches a height of 5 meters. While OSIRIS-REx did not fly as low during rehearsal, it used the hazard map to assess whether the predicted touchdown orbit would have prevented the surface of hazards, and found that the spaceflight path during rehearsal provided a safe touchdown on sampling would have allowed site Nightingale.
In the last minutes of the advent of space travel, OSIRIS-REx is also collecting new high-resolution navigation images for the NFT command line system. These detailed images of Bennu’s landmarks will be used for the sampling event, and will allow the spacecraft to focus precisely on a very small area.
“Many important systems were practiced during this rehearsal – from communications, spaceships, and most importantly, the on-board Natural Feature Tracking guidance system and hazard map,” said OSIRIS-REx lead researcher Dante Lauretta of the University of Arizona, Tucson. “Now that we have completed this milestone, we are confident in finalizing the procedures for the TAG event. This rehearsal confirmed that the team and all spaceship systems are ready to collect a sample in October. ”
The mission team has spent the last few months preparing for rehearsals for Matchpoint, while working remotely as part of the COVID-19 answer. On the rehearsal day, a limited number of personnel checked the space telemetry from the Lockheed Martin Space facility, NASA’s Goddard Space Flight Center and the University of Arizona, and took appropriate security measures, while the rest of the team performed their roles remotely.
The spacecraft will travel the entire journey to the surface of the asteroid during its first test for collection replacement, scheduled for October 20th. During this event, the OSIRIS-REx sampling mechanism will apply to Bennu’s surface for several seconds, igniting a charge of pressurized nitrogen to disrupt the surface and collecting a sample before the spacecraft leaves. The spacecraft is scheduled to return the monster to Earth on September 24, 2023.
NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides general mission management, systems engineering, and security and mission insurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the mission’s science team and science observation planning and data processing. Lockheed Martin Space in Denver built the spaceship and provided 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 Science Mission Agency in Washington.
