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US Spacecraft MESSENGER Prepares Second Flyby With Mercury

Next Monday the U.S. spacecraft MESSENGER will fly past Mercury a second time in preparation for settling in to orbit around the planet closest to the Sun. Mission controllers with the U.S. space agency NASA are anxiously awaiting the event, which will give them an opportunity to view most of the unseen surface of Mercury. VOA's Jessica Berman reports.

Monday's rendezvous with Mercury is the second of three flybys by MESSENGER, which stands for Mercury Surface, Space Environment, Geochemistry and Ranging.

MESSENGER, which was launched in 2004, is using the encounters as critical gravity assists to help ease the spacecraft into Mercury's orbit in 2011.

The flyby will bring MESSENGER very close to the planet's surface, according to Daniel O'Shaughnessy, head of guidance and control of the mission.

"MESSENGER will whizz 200 kilometers above the planet at a relative speed of nearly 15,000 miles per hour. During this time, MESSENGERwill train its suite of miniaturized instruments at portions of the planet never before seen at such a distance," he said.

NASA scientists say there will be a 17-minute blackout, during which time MESSENGER's instruments are expected to capture some 1,200 images of Mercury's rocky surface.

They say the data will be safely stored in internal batteries for analysis later.

NASA officials say the second MESSENGER encounter with Mercury will follow up data gathered during MESSENGER's January flyby, during which scientists learned new details about an enormous impact crater, volcanic structures and lava fields.

"What we're expecting is to see additional examples of the kind of geological features, the kind of geological units characterized by colors and shapes that we've seen so far," said Sean Solomon, the mission's principal investigator.

Mission managers say MESSENGER's second swing-by of Mercury will reveal thirty percent of the planet. Between MESSENGER's January rendezvous and images sent back by the Mariner missions 33 years ago, space scientists say they will soon glimpse 95 percent of Mercury's surface.

The space probe will fly past Mercury one more time in September 2009 before settling into permanent orbit in three years.