Washington, Jan 23 (IANS): NASA's OSIRIS-REx mission to bring an asteroid sample to Earth has successfully executed a 620-metre flyover of the site designated "Nightingale".

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

To perform the pass this week, the spacecraft left its 1.2-km safe home orbit and flew an almost 11-hour transit over the asteroid, aiming its science instruments toward the 16-m wide sample site before returning to orbit, NASA said.

Science observations from this flyover are the closest taken of a sample site to date.

The primary goal of the Nightingale flyover was to collect the high-resolution imagery required to complete the spacecraft's Natural Feature Tracking image catalogue, which will document the sample collection site's surface features - such as boulders and craters.

During the sampling event, which is scheduled for late August, the spacecraft will use this catalogue to navigate with respect to Bennu's surface features, allowing it to autonomously predict where on the sample site it will make contact.

Several of the spacecraft's other instruments also took observations of the Nightingale site during the flyover event.

A similar flyover of the backup sample collection site, Osprey, is scheduled for February 11, NASA said.

Even lower flybys will be performed later this spring -- March 3 for Nightingale and May 26 for Osprey -- as part of the mission's Reconnaissance C phase activities.

The spacecraft will perform these two flyovers at an altitude of 250 metres, which will be the closest it has ever flown over asteroid Bennu's surface.