NASA probe completes final practice before asteroid sample collection –

NASA probe completes final practice before asteroid sample collection –

Washington, Aug 13 (IANS):NASA’s OSIRIS-REx spacecraft has performed its final practice before making its first attempt to grab a sample from asteroid Bennu’s surface in October.

During the practice run of the sampling sequence this week, the spacecraft reached an approximate altitude of 40 metres over sample site Nightingale before executing a back-away burn, NASA said on Wednesday.

“This rehearsal confirmed that the team and all of the spacecraft’s systems are ready to collect a sample in October,” OSIRIS-REx principal investigator Dante Lauretta of the University of Arizona, Tucson, said in a statement.

Nightingale, OSIRIS-REx’s primary sample collection site, is located within a crater in Bennu’s northern hemisphere.

The approximately four-hour “Matchpoint” rehearsal took the spacecraft through the first three of the sampling sequence’s four manoeuvres: the orbit departure burn, the “Checkpoint” burn and the Matchpoint burn.

Checkpoint is the point where the spacecraft autonomously checks its position and velocity before adjusting its trajectory down toward the event’s third manoeuvre.

Matchpoint is the moment when the spacecraft matches Bennu’s rotation in order to fly in tandem with the asteroid surface, directly above the sample site, before touching down on the targeted spot.

Four hours after departing its 1-km safe-home orbit, OSIRIS-REx performed the Checkpoint manoeuvre at an approximate altitude of 125 metres above Bennu’s surface.

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