NASA's OSIRIS-REx spacecraft arrives at asteroid

Rodiano Bonacci
Dicembre 4, 2018

In 2020, after 18 months of observations, OSIRIS-REx will swoop close to Bennu and extend a long robotic arm equipped with its sample-collecting instrument, called TAGSAM.

That's why NASA has spent $800 million on the Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) program, launching a spacecraft to the space rock for an up-close-and-personal inspection of Bennu. It launched in September 2016 and will spend two years up close and personal with Bennu.

The actual arrival of the spacecraft won't be a touchdown or landing on the asteroid.

On Tuesday, the spacecraft will fly within 5 miles of Bennu, which will help design future orbits and map the surface.

Yet Bennu's small size also makes it possible for OSIRIS-REx to perform carefully choreographed hairpin maneuvers around the asteroid.

Spacecrafts have never before orbited a cosmic body as small as Bennu, which measures at just 500m (1,600ft) across.

The spacecraft will use a 3-meter mechanical arm to obtain the samples, as it is not set to actually land on the asteroid. It's easier to land on, and once on the surface, there will be plenty of material to sample.

With a puff of nitrogen gas, it will blow material off the asteroid's surface, gathering as much as 4.4 pounds (2 kilograms) of rock in the head of the sample. This latest rock is named Ryugu and is about double the size of Bennu.

The arm has a full range of motion, with joints capable of movement comparable to shoulder, elbow and wrist joints.

"Relieved, proud, and anxious to start exploring!" tweeted lead scientist Dante Lauretta of the University of Arizona. Astronomers have studied Bennu intensely from a distance, and they know that it's a carbonaceous, or carbon-rich, asteroid. Then it must turn around and retrace its path back home.

Scientists estimate the asteroid formed roughly 4.5 billion years ago.

"That is why for scientists this sample is going to be far more precious than even gold". Asteroid scientists are eager for "bonanza" of discoveries that await, as one researcher at mission control put it. The asteroid fits a number of criteria that make it intriguing and convenient.

Both Bennu and Ryugu are considered potentially hazardous asteroids.

A fun, interactive program on NASA's OSIRIS-REx page takes you through the stages of the spacecraft's mission. "Asteroids, the leftover debris from the solar system formation process, can answer these questions and teach us about the history of the sun and planets".

'Bennu is likely rich in organic molecules, which are made of chains of carbon bonded with atoms of oxygen, hydrogen, and other elements in a chemical recipe that makes all known living things. If it collided with Earth, Bennu would probably cause a crater. This knocked it through space until an orbit close to Earth locked it in place. Specifically, Bennu holds clay deposits, and embedded in clay is water.

The craft also captured a look at Earth and moon in their "orbital dance" back in January.

Engineer Tim Linn explains how the Osiris-Rex will suck up asteroid dust. "When we understand Bennu, we will understand something fundamental about our solar system".

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