NASA s asteroid-bound spacecraft flies by Earth

Washington Sep 23 (IANS) 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.

--IANS
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