NASA’s OSIRIS-REx Spacecraft Arrives at Asteroid Bennu

Mindy Sparks
December 6, 2018

OSIRIS-REx features a total of five instruments that will be used to study the giant space rock.

"The spacecraft is already in Bennu's gravitational* influence and, according to NASA's calculations, is set to officially arrive in orbit, just 2km above the asteroid, on Tuesday at around 4am AEDT*", CSIRO* tracking station spokesman Glen Nagle said.

Bennu is a carbonaceous asteroid - a primitive, carbon-rich piece of debris left over from the process that formed the solar system 4.6 billion years ago.

There is a small chance of Bennu slamming into Earth, but not until the 22nd century.

OSIRIS-REx is the size of a large family vehicle and will hover around the asteroid for a year before it makes its attempt at collecting the samples. Carbon is the key to the organic molecules needed for life, so finding organic molecules on a sample from Bennu would help to answer a big question about the origin of life. Getting their hands on pristine asteroid material might also yield clues about how to mine them for valuable materials and defend against wayward ones that might threaten Earth.

This series of images taken by the OSIRIS-REx spacecraft shows Bennu in one full rotation from a distance of around 50 miles (80 km).

Asked how he was feeling at the moment of arrival, principal investigator Dante Lauretta tweeted, "relieved, proud and anxious to start exploring!"

One of the primary objectives of @OSIRISREx is to understand the Yarkovsky Effect - a non-gravitational force that can change an asteroid's orbit.

That is correct. Currently the estimate is we anticipate a 1 in 2700 chance of it hitting the Earth in about 150 or 160 years from now.

A Japanese spacecraft, meanwhile, has been hanging out at another near-Earth asteroid since June, also for samples.

For a sample-return mission, the asteroid has to be the right size. "Watching the team celebrate such an unbelievable milestone brings personal joy to me in so many ways I can't even explain", Heather Enos, the Osiris-Rex deputy principal investigator said of the momentous occasion.

Osiris-Rex aims to collect at least 60 grams, or 2 ounces, of dust and gravel. This means that the components that make up the asteroid could be the same materials that formed the planets and sun in our solar system. That makes it a near-Earth asteroid, like the one Japan's Hayabusa-2 mission is now studying.

An arm mechanism called TAGSAM will reach out to collect the sample from Bennu's surface, making contact with the asteroid for five seconds in July 2020.

Osiris-Rex, an $8 million robot, was built by Lockheed Martin in Littleton, Colorado and launched from Florida's Cape Canaveral in September 2016. Its odometer read 1.2 billion miles (2 billion kilometers) as of Monday.

Why send a spacecraft to an asteroid?

OSIRIS-REx scientists expect to reveal the results of their early surveys of Bennu next week at the fall meeting of the American Geophysical Union in Washington.

OSIRIS-REx - the convoluted acronym stands for Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer - is equipped with three cameras, two spectrometers, a laser altimeter and an X-ray imaging system developed by college students.

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