NASA is almost ready to touch down on asteroid Bennu and grab a sample
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NASA’s OSIRIS-REx spacecraft has been investigating asteroid Bennu since it arrived there in 2018, sharing pictures of the distant body. But the craft didn’t just travel there to snap photos — it will also touch down onto the surface of the asteroid and take a sample to be returned to Earth.

This week, OSIRIS-REx performed its final practice run ahead of its planned touchdown. The rehearsal took four hours, during which NASA engineers checked that the spacecraft could perform its functions as intended, checking its orbit departure burn, the “Checkpoint” burn during which autonomous systems check the craft’s position and speed and adjust as needed to bring it into line with the asteroid, and the “Matchpoint” burn during which the craft matches the asteroid’s speed so it can touch down accurately and safely.

As part of the rehearsal, OSIRIS-REx also deployed its sampling arm, called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM), which it will use to scoop up a sample of rock and dust from the asteroid’s surface.

This artist's rendering shows the OSIRIS-REx spacecraft collecting a sample from the asteroid Bennu using a mechanical arm to touch the asteroid's surface.
This artist’s rendering shows the OSIRIS-REx spacecraft collecting a sample from the asteroid Bennu using a mechanical arm to touch the asteroid’s surface. NASA/Goddard Space Flight Center

“Many important systems were exercised during this rehearsal — from communications, spacecraft thrusters, and most importantly, the onboard Natural Feature Tracking guidance system and hazard map,” OSIRIS-REx principal investigator Dante Lauretta of the University of Arizona, Tucson, said in a statement. “Now that we’ve completed this milestone, we are confident in finalizing the procedures for the TAG [touch and go] event. This rehearsal confirmed that the team and all of the spacecraft’s systems are ready to collect a sample in October.”

While it was rehearsing, the spacecraft was also able to gather some science data including images of the asteroid and spectrometry observations. You can see some of the data captured in the video at the top of the page, which shows images taken by OSIRIS-REx’s SamCam camera as the spacecraft approached the asteroid’s surface. The images were taken over a period of less than 15 minutes, and during the rehearsal, the craft came within just 131 feet of the asteroid’s surface.

With everything working and the rehearsal deemed a success, OSIRIS-REx is ready to touch down on the asteroid and grab a sample on October 20, 2020. It will then return this sample to Earth for study, arriving on 24 September, 2023.

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