Visiting a distant, icy world that looks like a snowman certainly had space enthusiasts enraptured in the first days of 2019, but some other historic NASA news slipped through in the final hours of 2018 — and it might reveal just as much about our solar system.
The asteroid-chasing OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) performed its own historic maneuver on New Year's Eve. An eight-second thruster burn on Dec. 31 placed the spacecraft in orbit around 101955 Bennu, which drifts through the solar system's asteroid belt between the Earth and Mars.
By inserting itself into orbit around Bennu, OSIRIS-REx will survey the asteroid from a distance of only about 1 mile (1.75 kilometres) from its centre. Bennu's small size creates an incredibly tiny gravitational force, so maintaining that orbit will require lots of little adjustments, made by NASA and its collaborating organizations.
"The gravity of Bennu is so small, forces like solar radiation and thermal pressure from Bennu's surface become much more relevant and can push the spacecraft around in its orbit much more than if it were orbiting around Earth or Mars, where gravity is by far the most dominant force," said Dan Wibben, maneuver and trajectory design lead.
NASA also released a GIF of the various surveys OSIRIS-REx carried out after arriving at Bennu on Dec. 3, 2018. The series of images, captured between Nov. 30 to Dec. 31, helped the team more accurately determine Bennu's mass, which ensured that the orbital insertion would proceed smoothly.
You can see the GIF, captured by OSIRIS-REx black-and-white NavCam, below:
NASA/Goddard/University of Arizona/Lockheed Martin Space
The orbital period, lasting until mid-February, is expected to provide additional details about Bennu's gravity, orientation, how it spins and a better understanding of its mass. All those observations should lead to completing one of the chief objectives for OSIRIS-REx: Retrieve a sample from Bennu's surface and fly it back to Earth. In 2020, the spacecraft will extend a specially designed arm, called TAGSAM, for a brief high-five with the asteroid. The arm will blow nitrogen gas onto the surface of Bennu, kicking up handfuls of dirt, which the spacecraft will fly back to Earth in 2023.
A successful pickpocketing will give scientists a more detailed look at the kind of compounds that make up the potentially hazardous object.
Bennu is the second most likely near-Earth object to collide with our planet, only outranked by an asteroid known as 1950 DA on NASA's Palermo Technical Impact Hazard Scale. Though they're ranked as hazardous, the actual likelihood they would ever collide with Earth is incredibly low — Bennu could collide with the Earth between 2169 and 2199. 1950 DA shouldn't trouble you at all. If it were to hit at all, that impact wouldn't occur until 2880.
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