A historic second is on the horizon for NASA’s OSIRIS-REx mission. In just some weeks, the robotic OSIRIS-REx spacecraft will descend to asteroid Bennu’s boulder-strewn floor, contact down for just a few seconds and acquire a pattern of the asteroid’s rocks and mud – marking the primary time NASA has grabbed items of an asteroid, which can be returned to Earth for research.
On October 20, 2020, the mission will carry out the primary try of its Contact-And-Go (TAG) pattern assortment occasion. This sequence of maneuvers will convey the spacecraft right down to web site Nightingale, a rocky space 52 ft (16 m) in diameter in Bennu’s northern hemisphere, the place the spacecraft’s robotic sampling arm will try to gather a pattern. Website Nightingale was chosen because the mission’s main pattern web site as a result of it holds the best quantity of unobstructed fine-grained materials, however the area is surrounded by building-sized boulders. Throughout the sampling occasion, the spacecraft, which is the scale of a giant van, will try to the touch down in an space that’s solely the scale of some parking areas, and just some steps away from a few of these giant boulders.
On October 20, 2020, the OSIRIS-REx mission will carry out the primary try of its Contact-And-Go (TAG) pattern assortment occasion. Not solely will the spacecraft navigate to the floor utilizing progressive navigation strategies, however it may additionally acquire the most important pattern for the reason that Apollo missions. Credit score: NASA’s Goddard House Flight Heart
Throughout the four.5-hour pattern assortment occasion, the spacecraft will carry out three separate maneuvers to achieve the asteroid’s floor. The descent sequence begins with OSIRIS-REx firing its thrusters for an orbit departure maneuver to depart its safe-home orbit roughly 2,500 toes (770 meters) from Bennu’s floor. After touring 4 hours on this downward trajectory, the spacecraft performs the “Checkpoint” maneuver at an approximate altitude of 410 ft (125 m). This thruster burn adjusts OSIRIS-REx’s place and pace to descend steeply towards the floor. About 11 minutes later, the spacecraft performs the “Matchpoint” burn at an approximate altitude of 177 ft (54 m), slowing its descent and focusing on a path to match the asteroid’s rotation on the time of contact. The spacecraft then descends to the floor, touches down for lower than sixteen seconds and fires one in all its three pressurized nitrogen bottles. The fuel agitates and lifts Bennu’s floor materials, which is then caught within the spacecraft’s collector head. After this temporary contact, OSIRIS-REx fires its thrusters to again away from Bennu’s floor and navigates to a secure distance from the asteroid.
After the orbit departure maneuver, the spacecraft undertakes a sequence of reconfigurations to organize for sampling. First, OSIRIS-REx extends its robotic sampling arm – the Contact-And-Go Pattern Acquisition Mechanism (TAGSAM) – from its folded storage place out to the pattern assortment place. The spacecraft’s two photo voltaic panels then transfer right into a “Y-wing” configuration over the spacecraft’s physique, which positions them safely up and away from the asteroid’s floor throughout contact down. This configuration additionally locations the spacecraft’s middle of gravity instantly over the TAGSAM collector head, which is the one a part of the spacecraft that can contact Bennu’s floor throughout the pattern assortment occasion.
Overhead view of OSIRIS-REx at pattern web site Nightingale, with a parking zone for comparability. Credit score: NASA/Goddard/CI Lab/College of Arizona
As a result of the spacecraft and Bennu are roughly 207 million miles (334 million km) from Earth throughout TAG, it’s going to take about 18.5 minutes for alerts to journey between them. This time lag prevents the stay commanding of flight actions from the bottom throughout the TAG occasion, so the spacecraft is designed to carry out your entire pattern assortment sequence autonomously. Previous to the occasion’s begin, the OSIRIS-REx crew will uplink all the instructions to the spacecraft after which ship a “GO” command to start.
To autonomously navigate to web site Nightingale, OSIRIS-REx makes use of the Pure Characteristic Monitoring (NFT) navigation system. The spacecraft begins amassing navigation photographs about 90 minutes after orbit departure. It then compares these real-time photographs to an onboard picture catalog, utilizing recognized floor options to ensure that it’s on the correct course towards the location. Because the spacecraft approaches the floor, OSIRIS-REx updates the Checkpoint and Matchpoint maneuvers primarily based on the NFT’s estimate of the spacecraft’s place and velocity. OSIRIS-REx continues to make use of the NFT estimates because it descends to the floor after the Matchpoint maneuver to observe its place and descent price. The spacecraft will autonomously abort ought to its trajectory range outdoors of predefined limits.
Floor-level view of OSIRIS-REx at pattern web site Nightingale, with a parking zone for comparability. Credit score: NASA/Goddard/CI Lab/College of Arizona
To make sure that the spacecraft touches down on a secure space that avoids the area’s many boulders, the navigation system is provided with a hazard map of web site Nightingale, which delineates areas inside the pattern web site that would probably hurt the spacecraft. If the spacecraft’s NFT system detects that it’s on target to the touch one in all these hazardous zones, the spacecraft will autonomously wave off its strategy as soon as it reaches an altitude of 16 ft (5 m). This retains the spacecraft secure and permits for a subsequent pattern assortment try at a future date.
Because the spacecraft performs every occasion within the pattern assortment sequence, it’s going to ship telemetry updates again to the OSIRIS-REx crew, albeit at an especially sluggish knowledge price. The crew will monitor the telemetry throughout the tour and can be capable of affirm that the spacecraft has efficiently touched down on Bennu’s floor quickly after TAG happens. The pictures and different science knowledge collected throughout the occasion can be downlinked after the spacecraft has backed away from the asteroid and may level its bigger antenna again to Earth to transmit at increased communication charges.
OSIRIS-REx is charged with amassing at the least 2 oz. (60 grams) of Bennu’s rocky materials to ship again to Earth – the most important pattern return from area for the reason that Apollo program – and the mission developed two strategies to confirm that this pattern assortment occurred. On October 22, OSIRIS-REx’s SamCam digicam will seize photographs of the TAGSAM head to see whether or not it accommodates Bennu’s floor materials. The spacecraft will even carry out a spin maneuver on October 24 to find out the mass of collected materials. If these measures present profitable assortment, the choice can be made to position the pattern within the Pattern Return Capsule (SRC) for return to Earth. If enough pattern has not been collected from Nightingale, the spacecraft has onboard nitrogen expenses for 2 extra makes an attempt. A TAG try on the back-up Osprey web site could be made no sooner than January 2021.
The mission crew has spent the final a number of months getting ready for the pattern assortment occasion whereas maximizing distant work as a part of its COVID-19 response. On the day of TAG, a restricted variety of crew members will monitor the spacecraft from Lockheed Martin House’s Mission Assist Space, taking applicable security precautions. Different members of the crew will even be at different places on-site to cowl the occasion, whereas additionally observing security protocols.
The spacecraft is scheduled to depart Bennu in 2021 and it’ll ship the collected pattern to Earth on September 24, 2023.
NASA’s Goddard House Flight Heart in Greenbelt, Maryland, gives general mission administration, techniques engineering, and the security and mission assurance for OSIRIS-REx. Dante Lauretta of the College of Arizona, Tucson, is the principal investigator, and the College of Arizona additionally leads the science crew and the mission’s science remark planning and knowledge processing. Lockheed Martin House in Denver constructed the spacecraft and gives flight operations. Goddard and KinetX Aerospace are accountable for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program, which is managed by NASA’s Marshall House Flight Heart in Huntsville, Alabama, for the company’s Science Mission Directorate in Washington.