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“Touch-And-Go”: OSIRIS-REx is set to land on an asteroid and collect material in October

September 29, 2020
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The spacecraft will carry out the collection attempt autonomously due to communication delays. If successful, the collection could be the largest sample recovery in decades, according to NASA.

osiris-rex

An artist’s rendering depicting OSIRIS-REx above Bennu.

Image: NASA/Goddard/University of Arizona

NASA’s Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) spacecraft has been tasked with traveling billions of kilometers to an asteroid, collect a sample of its surface, and return the material back to Earth.

Last week, NASA announced the “countdown” to the craft’s upcoming asteroid “Touch-And-Go” (TAG). OSIRIS-REx is scheduled to attempt its first TAG on Oct. 20. If successful, the attempt could yield the largest space material since the Apollo era, according to NASA.

In September 2016, the OSIRIS-REx Mission launched aboard an Atlas V 411 rocket en route to its asteroid target, Bennu. After more than two Earth years in transit, OSIRIS-Rex arrived at Bennu in December of 2018. The spacecraft would then spend months surveying its target using a suite of onboard instruments to identify a “location that is safe and scientifically interesting to collect” a sample of the asteroid, per NASA.

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During the mission’s Reconnaissance A phase, the craft conducted a series of flyovers above four potential landing sites before a final selection was made. The team selected the Nightingale site over the other finalists Sandpiper, Osprey, and Kingfisher. The area believed to be “relatively young, and the regolith is freshly exposed” meaning the Nightingale site “would likely allow for a pristine sample of the asteroid,” per NASA. Nightingale is not without its share of obstacles including “building-sized boulders” surrounding the region.

There are other logistical challenges associated with performing a collection sample from more than 200 million miles away. Due to the 18.5-minute communication delay between the craft and command on Earth, OSIRIS-REx is designed to autonomously perform the entire collection sequence, per NASA. Ahead of the collection, “the OSIRIS-REx team will uplink all of the commands to the spacecraft and then send a “GO” command to begin.”

Overall, the sample collection is scheduled to span approximately 4.5 hours. As part of the attempt, the craft will perform a series of maneuvers as it descends toward the asteroid’s surface roughly 2,500 feet below. NASA uses an everyday Earthly parking analogy to illustrate the TAG in which a “large van”-sized OSIRIS-REx attempts to “touch down in an area that is only the size of a few parking spaces” with a “few steps” separating the site from the surrounding boulders.

osiris-rex

An artist’s concept featuring OSIRIS-REx during sample collection.

Image: NASA’s Goddard Space Flight Center

In addition to speeding through the solar system at 63,000 mph, it’s important to note that Bennu is also rotating. During the cosmic park and turnabout, the craft will need to match this rotation and target a path that will bring it into contact with the specified landing site.

OSIRIS-REx will touch down on Bennu for “less than 16 seconds,” at which point it will fire one of three pressurized nitrogen containers to agitate and elevate Bennu’s surface material. The craft’s collector head is designed to catch this agitated material. At this time, the onboard Touch-And-Go Sample Acquisition Mechanism (TAGSAM) will be the only part of the spacecraft to make contact with Bennu.

Next, the craft will fire onboard thrusters to ascend from the asteroid. OSIRIS-REx is “charged with collecting at least 2 oz.” of surface material, per NASA. After the ascent, an onboard camera will image the collector head to verify a successful sample collection recovery. A subsequent “spin maneuver” will determine the mass of the sample. If this test determines the attempt to be successful, the sample will be prepped for its return to Earth.

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It’s important to remember that the craft has three pressurized chambers on board for collection purposes. If the first collection fails, the team can prepare the craft for another attempt. Although, a collection at the “back-up Osprey site would be made no earlier than January” of next year, according to NASA. In 2021, OSIRIS-REx is slated to depart from the asteroid, and, if all goes as planned, OSIRIS-REx will return to Earth with the sample in tow in September of 2023.

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