NASA probe Osiris-Rex becomes ancient asteroid's first visitor


Reuters reported that from that stage, the spacecraft will begin gradually tightening its orbit around the asteroid, spiraling to within just 6 feet of its surface.

"For the past several months, Bennu has been coming into focus as I approached", the probe's Twitter account said.

NASA scientists chose 101955 Bennu for the OSIRIS-REx mission because of its unique supply of unadulterated carbonaceous material, one of the building blocks of life.

The craft has now traveled more than a billion miles since launching in September 2016. "This successful test shows that, when the time comes, TAGSAM is ready to reach out and tag the asteroid".

By 2021, the window for OSIRIS-REx's slow return to Earth will open, and it'll set itself on a path that will bring it by the the third planet in September 2023. The spacecraft will then make two more polar flybys, giving the team on Earth a chance to get to get comfortable with the spacecraft's navigational capabilities near Bennu. This means that although it's now 76 million miles away, it gets fairly close to Earth every six years.

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This will be made all the more hard as the heat of the sun will alter the craft's trajectory slightly, meaning mission control back on earth must keep a close watch to issue course corrections and keep the probe in place before it can establish a stable orbit early in 2019. NASA scientists think the 484-meter-wide rock was once part of a much larger asteroid, which suggests was as large as the USA state of CT (which is 110 miles wide and 70 miles long), that was blown apart by some colossal collision a billion years ago. Over the next several days, a team led by Distinguished Professor Daniel Scheeres will take the first stab at calculating a simple, but critical, number: Bennu's mass.

In addition, it is larger than 200 meters and so does not spin rapidly (which would complicate sample retrieval), and it is a primitive carbon-rich leftover from the beginnings of the solar system, with organic molecules, volatiles, and amino acids that could tell us how life began on Earth.

Starting in October, OSIRIS-REx performed a series of braking maneuvers to slow the spacecraft down as it approached Bennu.

Osiris-Rex aims to collect at least 60 grams (two ounces) of dust and gravel, the first such attempt by the U.S. after a smaller mission to another asteroid by Japan. A sampling arm attached to the probe will rest on the surface for about five seconds.

The spacecraft will also carry a laser altimeter, a suite of cameras provided by the University of Arizona, spectrometers and lidar, which is similar to radar, using light instead of radio waves to measure distance. But there are other asteroids like Bennu out there, and the more we understand them, the better. For example, the probe's measurements, and those of researchers studying the returned sample, should reveal a great deal about the resource potential of Bennu-like asteroids. No spacecraft has ever orbited such a small body. The robotic explorer Osiris-Rex pulled within 12 miles (19km) of the diamond-shaped object on Monday and will go into orbit around it on 31 December.