NASA's OSIRIS-REx mission and the asteroid Bennu have had a date planned for two years, and just after noon ET today, they finally got to meet face to face. The $800 million mission was launched in September of 2016, and if all goes according to plan, it will return a sample to Earth in September, 2023. This will hopefully provide a sample of between 60g and 2,000g of surface regolith material (the layer of material covering solid rock). "The low-gravity environment is one of the foremost challenges in conducting this mission", Rich Burns, OSIRIS-REx project manager at NASA's Goddard Space Flight Center, said in a NASA video.
NASA targeted Bennu for its sample mission for a number of reasons.
The long-awaited rendezvous officially kicks off the start of the ambitious mission to study a near-Earth object that could hold the key to understanding the origins of our solar system, and life itself. So close that it's considered a Potentially Hazardous Object (PHO), an object with an orbit that brings it close to Earth, and that's large enough to do serious damage if it struck.
This asteroid, named Bennu after a mythological Egyptian bird, by 9 year old student Michael Puzio in a contest by the Planetary Society, was selected from over 500,000 asteroids known in our Solar System as it was an Apollo-class near earth object (NEO) between 0.8 and 1.6 AU from the Sun (Earth is 1 AU). Its proximity to us made it a prime target for OSIRIS-REx. Too small, around 200 meters or less in diameter, and it spins so fast you can't land on it. Now that OSIRIS-REx is at Bennu, the craft will stay about 12 miles (20 kilometers) away from the asteroid.
"Now that we've arrived, we will explore [Bennu's] surface through a series of flybys and orbital campaigns that allow us to determine which areas on Bennu are the safest and have material that can be ingested by our sampling mechanism", Daniella DellaGiustina of the University of Arizona told Sky and Telescope. The primitive asteroids like Bennu resemble what Earth looked like when life began, containing organic molecules, volatiles, and amino acids that may have been the precursors to life on Earth.
OSIRIS-REx, launched in September 2016, will come even closer to Bennu in the coming month and spend nearly one year scrutinising the asteroid before selecting a location that is safe and scientifically valuable to collect the sample.
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Contact with Bennu will not significantly change its orbit or make it more risky to Earth, Lauretta stressed. It has a nice suite of instruments to do its work.
On Tuesday, the spacecraft will fly within 5 miles of Bennu, which will help design future orbits and map the surface. This means OSIRIS-REx can match its velocity and touch down briefly. Lauretta said there was a chance of sending the carrier spacecraft on an extended mission after that, but for now, he wants the team to stay focused on the primary mission.
On its first attempt, OSIRIS-REx will swoop down more than 410ft (125m) from its orbit around Bennu. "We'll do this first globally, and from there prioritize two candidate sample sites".
During the five-second maneuver, compressed nitrogen gas will shoot into the collector, stirring up and lifting small rocks and soil.
The dust will be captured in the sampler head.
If all goes well, the craft will bring the sample back to Earth in September 2023.
The SRC will separate from the spacecraft and enter Earth's atmosphere, to be collected at the Utah Test and Training Range.