NASA’s Osiris-Rex spacecraft orbits around asteroid Bennu

NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft entered orbit around an asteroid, Bennu, the smallest object ever to be circled by a human-made spaceship. The spacecraft, 110 million kilometres away, carried out a single, eight-second burn of its thrusters on Monday. The spacecraft is the first-ever US mission designed to visit an asteroid and return a sample of its dust back to Earth. "Entering orbit around Bennu is an amazing accomplishment that our team has been planning for years," said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson. The spacecraft is orbiting Bennu about a mile from its centre.

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It's official! I'm in orbit around #asteroid Bennu -- now the smallest body ever orbited by a spacecraft. My snug path around the asteroid also sets a new record for the closest orbit of a planetary body by any spacecraft. #HappyNewYear, indeed! More ➡️ https://t.co/fwL3FEVU9m pic.twitter.com/ceavR7ju6i

— NASA's OSIRIS-REx (@OSIRISREx) December 31, 2018

"Bennu has a gravity force only five-millionths as strong as Earth's,” NASA said. Each orbit by OSIRIS-REx will take 62 hours. Bennu is also considered potentially dangerous. It poses a slight risk -- a one in 2,700 chance of colliding with Earth in 2135.

The spacecraft is aimed to at least collect 60g of dust and gravel. However, Osiris-Rex won’t be landing on asteroid Bennu but, rather use 3-metre mechanical arm to vacuum up particles in 2020. The spacecraft will head towards Earth in 2021. 

On August 17, spacecraft’s PolyCam camera obtained the image from a distance of 2.2 million kilometres. 

At Bennu, the spacecraft spent the first-month performing fly-by of Bennu’s north pole, equator and south pole, at distances ranging between 11.8 and 4.4 miles (19 and 7 km) from the asteroid. The spacecraft will extensively survey the asteroid before the mission team identifies two possible sample sites, which will allow the team to pick one for sample collection, scheduled for July 2020. After the sample collection, the spacecraft will head back towards Earth before ejecting the “Sample Return Capsule” for landing in the Utah desert in September 2023.

The name of the spacecraft and asteroid come from Egyptian mythology. Osiris is the god of the afterlife, while Bennu represents the heron and creation.

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In 2010, Japanese space agency JAXA’s Hayabusa spacecraft crash-landed into the surface of its target asteroid and managed to return a few micrograms of material. Hence proving sample collection from an asteroid is possible.