NASA’s OSIRIS-REx Begins Its Countdown to TAG Asteroid Bennu’s Boulder-Strewn Surface

NASA’s OSIRIS-REx Begins Its Countdown to TAG Asteroid Bennu’s Boulder-Strewn Surface

This artist’s idea reveals NASA’s OSIRIS-REx spacecraft descending in the direction of asteroid Bennu to gather a pattern of the asteroid’s floor. Credit: NASA/Goddard/University of Arizona

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 accumulate a pattern of the asteroid’s rocks and dirt – marking the primary time NASA has grabbed items of an asteroid, which might be returned to Earth for examine.

On October 20, 2020, the mission will carry out the primary try of its Touch-And-Go (TAG) pattern assortment occasion. This sequence of maneuvers will carry the spacecraft all the way down to website 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. Site Nightingale was chosen because the mission’s main pattern website as a result of it holds the best quantity of unobstructed fine-grained materials, however the area is surrounded by building-sized boulders. During the sampling occasion, the spacecraft, which is the dimensions of a giant van, will try to the touch down in an space that’s solely the dimensions 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 Touch-And-Go (TAG) pattern assortment occasion. Not solely will the spacecraft navigate to the floor utilizing modern navigation strategies, however it may additionally accumulate the most important pattern for the reason that Apollo missions. Credit: NASA’s Goddard Space Flight Center

During the 4.5-hour pattern assortment occasion, the spacecraft will carry out three separate maneuvers to succeed in 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 ft (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 velocity 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 concentrating 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 considered one of its three pressurized nitrogen bottles. The gasoline 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 arrange for sampling. First, OSIRIS-REx extends its robotic sampling arm – the Touch-And-Go Sample 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 heart of gravity straight over the TAGSAM collector head, which is the one a part of the spacecraft that may contact Bennu’s floor throughout the pattern assortment occasion.


Overhead view of OSIRIS-REx at pattern website Nightingale, with a parking zone for comparability. Credit: NASA/Goddard/CI Lab/University of Arizona

Because 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 indicators to journey between them. This time lag prevents the dwell commanding of flight actions from the bottom throughout the TAG occasion, so the spacecraft is designed to carry out your complete pattern assortment sequence autonomously. Prior to the occasion’s begin, the OSIRIS-REx workforce will uplink all the instructions to the spacecraft after which ship a “GO” command to start.

To autonomously navigate to website Nightingale, OSIRIS-REx makes use of the Natural Feature Tracking (NFT) navigation system. The spacecraft begins gathering navigation photos about 90 minutes after orbit departure. It then compares these real-time photos to an onboard picture catalog, utilizing recognized floor options to make it possible for it’s on the precise course towards the positioning. As 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 charge. The spacecraft will autonomously abort ought to its trajectory range exterior of predefined limits.


Surface-level view of OSIRIS-REx at pattern website Nightingale, with a parking zone for comparability. Credit: NASA/Goddard/CI Lab/University of Arizona

To be certain that the spacecraft touches down on a secure space that avoids the area’s many boulders, the navigation system is supplied with a hazard map of website Nightingale, which delineates areas throughout the pattern website that would probably hurt the spacecraft. If the spacecraft’s NFT system detects that it’s on the right track to the touch considered one of these hazardous zones, the spacecraft will autonomously wave off its method 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.

As the spacecraft performs every occasion within the pattern assortment sequence, it’s going to ship telemetry updates again to the OSIRIS-REx workforce, albeit at a particularly gradual knowledge charge. The workforce will monitor the telemetry throughout the tour and can be capable of verify that the spacecraft has efficiently touched down on Bennu’s floor quickly after TAG happens. The photos and different science knowledge collected throughout the occasion might 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 gathering a minimum of 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 digital camera will seize photos of the TAGSAM head to see whether or not it comprises Bennu’s floor materials. The spacecraft may also carry out a spin maneuver on October 24 to find out the mass of collected materials. If these measures present profitable assortment, the choice might be made to put the pattern within the Sample Return Capsule (SRC) for return to Earth. If ample 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 website can be made no sooner than January 2021.

The mission workforce has spent the final a number of months making 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 workforce members will monitor the spacecraft from Lockheed Martin Space’s Mission Support Area, taking applicable security precautions. Other members of the workforce may also be at different areas 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 Space Flight Center in Greenbelt, Maryland, offers general mission administration, techniques engineering, and the protection and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona additionally leads the science workforce and the mission’s science statement planning and knowledge processing. Lockheed Martin Space in Denver constructed the spacecraft and offers flight operations. Goddard and KinetX Aerospace are chargeable 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 Space Flight Center in Huntsville, Alabama, for the company’s Science Mission Directorate in Washington.

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