Two years and two months after it was launched from the Cape Canaveral Air Force Station, a NASA $ 800 million mission to the asteroid belt between Mars and Jupiter will reach a momentous moment on Monday, when the OXIRIS-REX spacecraft is scheduled for its rendezvous with its scientific goal: a circular asteroid rich in carbon called Bennu.
At less than 500 meters in diameter, Bennu is a small solar system body with great scientific potential: astronomers suspect that the rocky composition of the asteroid has remained more or less unchanged since it formed about 4.5 billion years ago. The collection and analysis of a sample of the asteroid can tell scientists very much about the origins of our solar system, its planets, and the source of organic molecules that can lead to life on Earth.
But before anyone can squeeze through a Bennu sample, NASA must first collect it and get it. This will take several major steps, the first being scheduled for Monday, around 9 am, when OSIRIS-REx (short for origin, spectral interpretation, resource identification, security-Regolith Explorer) will arrive at Bennu and start its long process of monitoring the surface of the asteroid. You can see the arrival of NASA Television (above), where the agency will be broadcast live from mission control between 11:45 and 12:15 ET. NASA will also launch a program to review the arrival at 11:15 AM in the morning.
After arriving in Benno, OSIRIS-REx will spend weeks maneuvering around the asteroid, collecting data on its mass, topography, and composition. The spacecraft will launch a 12-mile de-mining survey and culminate in a series of low-pass flies of about 800 feet above the surface of the asteroid before entering the orbit of the asteroid on New Year's Eve. If NASA is successful, Bennu will become the smallest object that ever orbited the agency.
The goal at that moment will be to identify a safe and scientifically promising site for samples. Note that we said "sample" site-not "landing" site. OSIRIS-REx will never touch the surface of the asteroid. Instead, in a series of maneuvers that are currently scheduled for mid-2020, the spacecraft will descend to the surface, floating only close enough to collect a sample from Bennu's surface with its long 10-foot robotic arm. The planners of the OSIRIS-REx mission aim to receive a sample of at least 2 ounces, although the spacecraft is designed to have about 4.4 kilograms of space dust. In any case, it will be the largest NASA sample collected by Apollo missions in the 1970s.
Assuming everyone has come to that point, OSIRIS-REx will leave Bennu in the spring of 2021 and begin its two-and-a-half-year journey back to Earth. But we are working ahead of ourselves: Before OSIRIS-REx is set up on the return part of its journey, you will first have to play with Bennu for several years. That dance starts today.
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