NASA's OSIRIS-REx clears last hurdle before Earth return

NASA's OSIRIS-REx spacecraft successfully performs a critical trajectory adjustment, preparing to deliver asteroid Bennu samples to Earth on September 24th.
Rizwan Choudhury
OSIRIS-REx spacecraft unfurled its robotic arm on Oct 20 2020.
OSIRIS-REx spacecraft unfurled its robotic arm on Oct 20 2020.

Credits: NASA/Goddard/University of Arizona via Flickr 

NASA's OSIRIS-REx spacecraft executed a crucial trajectory-correction maneuver yesterday. Firing its Attitude Control System (ACS) thrusters, the spacecraft pointed toward our home planet. This slight adjustment ensures it will be in the optimal position to release its precious sample capsule—containing rocks and dust from asteroid Bennu—63,000 miles (or 102,000 kilometers) above Earth’s surface on Sunday, September 24.

As per NASA, the spacecraft had to change its velocity by a minute yet pivotal ½ mph (less than 1 kph) relative to Earth. While seemingly minor, the adjustment was of utmost importance; without it, OSIRIS-REx would have zoomed past Earth, its invaluable cargo going unreturned.

NASA's OSIRIS-REx clears last hurdle before Earth return
he yellow diamonds indicate the dates of spacecraft maneuvers that slightly adjust its trajectory to get it closer, and then pointing at, and then above Earth.

Critical timing and coordinates

Post the trajectory adjustment, the spacecraft is now prepared to release the sample capsule at 8:42 am MDT / 10:42 am. EDT. The capsule will enter Earth's atmosphere at a strategically calculated speed and angle. It is expected to land 13 minutes post-release within a predetermined 36-mile by 8.5-mile (58-kilometer by 14-kilometer) area. This landing zone has been marked out on the Department of Defense’s Utah Test and Training Range, southwest of Salt Lake City.

Ground teams will quickly transport the capsule via helicopter to a temporary clean room to avoid contamination. A recent rehearsal in Utah, involving the collection and helicopter transport of Earth rock samples, was described by NASA as their most realistic drill yet. During the recovery, the team will also collect nearby rock samples to assess potential contamination of the capsule.

Next adventure

While the spotlight is undoubtedly on the sample return, OSIRIS-REx has more celestial journeys to embark upon. Roughly 20 minutes after the sample capsule's release, the spacecraft will ignite its engines again. This time, the goal will be to divert the spacecraft from Earth and propel it towards its next mission: asteroid Apophis in 2029, under the new mission name OSIRIS-APEX (OSIRIS-Apophis Explorer).

OSIRIS-REx, the first U.S. mission to gather samples from an asteroid, will return to Earth on September 24, 2023, bearing geological treasures from asteroid Bennu. The material—rocks and dust initially collected in 2020—promises to serve as an astronomical time capsule. Scientists anticipate that the pristine samples will offer unprecedented insights into the formative years of our solar system, approximately 4.5 billion years ago.

Fine-tuning the journey home

While the current adjustments have set the spacecraft on course for its landmark capsule release, NASA engineers haven't ruled out further trajectory tweaks. If deemed necessary, the spacecraft may fire its thrusters again on September 17, executing a final maneuver before its capsule release a week later.

OSIRIS-REx is about 4 million miles, or roughly 7 million kilometers, from Earth. It is hurdling through space at approximately 14,000 mph (nearly 23,000 kph), all set for its historic rendezvous with Earth later this month.

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