NASA's asteroid-bound spacecraft slingshots past Earth

Representational image

Washington: NASA`s asteroid sample return spacecraft flew past Earth on Friday on its way to asteroid Bennu, for a rendezvous next August.

The OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security - Regolith Explorer) spacecraft came within 17,237 km of Antarctica at 12.52 pm EDT (10. 22 pm India time) on Friday, just south of Cape Horn, Chile, before following a route north over the Pacific Ocean, NASA said. 

"The encounter with Earth is fundamental to our rendezvous with Bennu," said Rich Burns, OSIRIS-REx Project Manager at NASA`s Goddard Space Flight Center in Greenbelt, Maryland.

The OSIRIS-REx spacecraft is currently on a seven-year journey to rendezvous with, study, and return a sample of Bennu to Earth. This sample of a primitive asteroid will help scientists understand the formation of our solar system more than 4.5 billion years ago.

The spacecraft launched on September 8, 2016, on an Atlas V 411 rocket. Although the rocket provided the spacecraft with the all the momentum required to propel it forward to Bennu, OSIRIS-REx needed an extra boost from the Earth`s gravity to change its orbital plane. 

Bennu`s orbit around the Sun is tilted six degrees from Earth`s orbit, and this manoeuvre changed the spacecraft`s direction to put it on the path toward Bennu.

As a result of the flyby, the velocity change to the spacecraft was 3.778 kilometres per second, NASA said. 

"The total velocity change from Earth`s gravity far exceeds the total fuel load of the OSIRIS-REx propulsion system, so we are really leveraging our Earth flyby to make a massive change to the OSIRIS-REx trajectory, specifically changing the tilt of the orbit to match Bennu," Burns said. 

The mission team also is using OSIRIS-REx`s Earth flyby as an opportunity to test and calibrate the spacecraft`s instrument suite. 

Approximately four hours after the point of closest approach, and on three subsequent days over the next two weeks, the spacecraft`s instruments will be turned on to scan Earth and the Moon, NASA said.

These data will be used to calibrate the spacecraft`s science instruments in preparation for OSIRIS-REx`s arrival at Bennu in late 2018. 

"The opportunity to collect science data over the next two weeks provides the OSIRIS-REx mission team with an excellent opportunity to practice for operations at Bennu," said Dante Lauretta, OSIRIS-REx Principal Investigator at the University of Arizona, Tucson. 

"During the Earth flyby, the science and operations teams are co-located, performing daily activities together as they will during the asteroid encounter," Lauretta added.