Yesterday – while many on the Earth were ringing in the New Year – the NASA spacecraft of 70 million miles (110 million kilometers) broke the space exploration record. NASA's Osiris-Rex spacecraft carried out a single, eight-second burning of its traps and entered the orbit around the asteroid near Bennu, making Bennu the smallest object that has yet to orbit the spacecraft. And Bennu is, indeed, very small. It has a mean diameter of about 1614 feet (0.306 miles; 492 meters). The burning occurred on December 31, 2018, at 6:43 PM UTC (2:43 AM EST). Dante Lauretta, chief researcher of OSIRIS-REx at the University of Arizona Tucson, said:
The team [performed] perfect maneuver for inserting orbits. With the completion of the navigation campaign, we look forward to the scientific mapping and the selection phase at the place of the mission.
Entry into orbit around Bennu is an amazing achievement that our team has been planning for years.
A statement from the team notes that Bennu – named an ancient Egyptian mythological bird related to the sun, creation and rebirth – has barely enough gravity to keep the vehicle in a stable orbit.
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The previous recorder for the closest orbit of the planetary body was the Rosetta spaceship that orbits about four miles (6.4 km) from the center of the comet 67P / Churyumov-Gerasimenko in May 2016. OSIRIS-REx is much closer to Bennu, about one kilometer (1.6 km) from the center. This distance is necessary to keep the spacecraft locked in Bennu, these space scientists say, because Bennu's gravity is only five million as strong as the Earth.
The spacecraft should orbit around Bennu by mid-February, leisurely 62 hours after orbit.
The OSIRIS-REx system manager, Mike Moreau, who is located at the NASA Space Flight Center in Greenbelt, Maryland, commented:
The design of our orbit is largely dependent on Benne's physical properties, such as the mass and the gravitational field that we did not know before we arrived.
Until now, we had to explain a wide range of possible scenarios in our computer simulations to ensure that we can safely navigate the spacecraft so close to Bennu. While the team learned more about the asteroid, we incorporated new information to consolidate the final design of the orbit.
Although OSIRIS-REx is the most stable stable orbit, the team said the Bennu gravity retreat is so weak that maintaining space flight safety requires temporary adjustments. Dan Vibben, OSIRIS-REx maneuver and trajectory design leads at KinetX Aerospace in Simi Valley, California, said:
Bennu's weight is so low, forces like solar radiation and thermal pressure from the surface of Bennu become much more relevant and can push the spacecraft into their orbit much more than if they circled around the Earth or Mars, where gravity is by far the most dominant force.
One of the key objectives of this orbital phase is to improve Bennet mass growth and gravity, features that will influence the planning of the rest of the mission, especially the short touch on the sample collection surface in 2020. In the case of Bennu, scientists can measure these characteristics only by making OSIRIS-REx very close to the surface to see how its trajectory bends from the gravitational pull of Bennu.
The OSRIS-REx mission is to deliver the sample to Earth in September 2023.
The Bennu asteroid is considered a potentially dangerous object because its orbit carries it near the Earth and is large enough to cause significant damage in the event of an impact. There are cumulative 1,700 chances to affect the Earth between 2175 and 2199.
Read more from the University of Arizona
Bottom line: NASA Osiris-Rex spacecraft successfully burns on December 31, 2018, starting at 6:43 PM UTC (2:43 AM EST) and thus went into orbit around the asteroid near Bennu. The maneuver makes Bennu the smallest object yet to orbit with a spacecraft.