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♪♪♪

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This is Bennu

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one of Earth’s closest planetary neighbors

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an asteroid roughly the height of a skyscraper

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a remnant from the dawn of the solar system,

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made of carbon-rich rocks and boulders

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And since late 2018, the place that NASA’s OSIRIS-REx mission has called home.

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When OSIRIS-REx arrived, it began wrapping Bennu in a complex web of observations 

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starting with a Preliminary Survey of its size, shape, mass, and spin.

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On New Year’s Eve, OSIRIS-REx was captured into orbit by Bennu’s miniscule gravity, 

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making it the smallest world ever to be orbited by a spacecraft.

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In early 2019, it broke orbit to conduct a Detailed Survey.

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A series of sweeping passes allowed OSIRIS-REx to study geological features

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at different latitudes and times of day,

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enabling stereo imaging and landmark-based navigation. 

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During the Detailed Survey, OSIRIS-REx globally mapped Bennu

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at only 5cm per pixel,

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the highest-resolution of any planetary body, including Earth.

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On June 12, the spacecraft entered a new orbit at an altitude of just 680 meters,

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setting another record, and establishing a home orbit for the remainder of the mission.

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In September, it began Reconnaissance on four candidate sample collection sites:

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potential locations on Bennu to touch down and collect a sample later in the mission.

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OSIRIS-REx concluded its first year at Bennu back in orbit, 

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circling the asteroid’s terminator, or boundary between day and night.

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Here, outside forces acting on the spacecraft are balanced, 

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allowing it to orbit within the same plane over time.

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Reconnaissance resumed in early 2020, with close flyovers of the primary 

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sample collection site Nightingale, and the backup site Osprey. 

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In mid-April, OSIRIS-REx performed the first of two rehearsals prior to sample collection.

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It navigated to a predetermined “Checkpoint” about 125 meters above Bennu, 

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then descended to within 65 meters before backing away.

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After the Checkpoint rehearsal, OSIRIS-REx flew one final

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Reconnaissance sortie over site Osprey.

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Then, it made a series of high-altitude maneuvers

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while rebooting its onboard processor, 

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and preparing for its second rehearsal of the sample collection event.

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♪♪♪ 

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On August 11, OSIRIS-REx departed its home orbit and made a four-hour traverse 

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to Bennu’s northern hemisphere, retracing its earlier path.

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After performing the Checkpoint engine burn to begin its descent,

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it made a second engine burn called “Matchpoint” to match Bennu’s rotation,

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before backing away at an altitude of approximately 40 meters.

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Now, the most crucial moment of the mission had arrived.

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On October 20, 2020, at approximately 11:30 am Mountain Time,

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the spacecraft departed orbit.

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A few hours before, mission controllers on Earth had sent the commands 

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for the Touch-And-Go sample collection maneuver, or TAG.

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As they watched with anticipation,

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 OSIRIS-REx steered itself to sample site Nightingale,

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maneuvering toward the small crater at the walking pace of a spider.

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At 4:11 pm, the mission received confirmation:

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OSIRIS-REx had touched down and collected its sample.

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Following TAG, the spacecraft drifted to a safe distance away from Bennu.

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By the end of October, mission controllers determined that it had 

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exceeded its goal of collecting 60 grams of asteroid material.

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They directed it to stow the sample in preparation for return to Earth.

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Before departing Bennu, OSIRIS-REx was given one final task.

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On April 7, it flew over site Nightingale

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to observe how the sample collection event had changed the surface.

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And with that, OSIRIS-REx had recorded its mark on Bennu

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and spun the last strand of its web.

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♪♪♪