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Tuesday, August 03, 2004

NASA Sends Mercury a MESSENGER

Despite a 24-hour delay, a NASA spacecraft bound for Mercury was successfully launched early Tuesday, the first step in a seven-year journey to the small planet.

A Boeing-built Delta 2 rocket shot the spacecraft MESSENGER off planet at 2:15:56 a.m. EDT (0615:56 GMT) on a pillar of flame above its launch pad at NASA’s Cape Canaveral Air Force Station. The on-time space shot easily made its 12-second window, with none of the delays that scrubbed a previous attempt to launch the spacecraft on Aug. 2.

“This was another great Boeing and NASA success as we bid MESSENGER farewell,” said Chuck Dovale, NASA launch director at Kennedy Space Center in Florida, after the launch.

MESSENGER, an acronym for MErcury Surface, Space ENvironment, GEochemistry, and Ranging, is the first NASA spacecraft to Mercury since Mariner 10 passed by the planet three times between 1974 and 1975.

““Mercury is very hard to get to,” explained MESSENGER science team member Ralph McNutt, from the Johns Hopkins University Applied Physics Laboratory, during the Aug. 2 launch attempt. “To get there, the MESSENGER spacecraft is about 55 percent fuel, about the same amount as the Cassini spacecraft to Saturn.”

MESSENGER is also expected to provide some hints to questions about Mercury’s density, interior and exterior composition, as well as its surface features and magnetic field. The spacecraft is taking a roundabout path to Mercury, swinging by three inner planets before entering orbit around Mercury in March 2011.

There were some weather concerns prior to MESSENGER’s liftoff. Nearby cloud cover, and the failure of launch weather balloons to reach high into the atmosphere gave launch planners some concern. But the clouds dissipated and one last batch of weather balloons reached their designated height of 90,000 feet before launch.

A good start

Cape Canveral launch officials applauded as MESSENGER’s Delta 2 booster sent the spacecraft on its way.

Four minutes into the flight, the spacecraft-rocket combo shed its first stage and ignited its second stage for a four-minute burn to reach orbit. After a 37-minute coast phase, MESSENGER’s Delta 2 booster again fired its second stage for a three-minute burn. The spacecraft’s third stage also made a short, two-minute maneuver before MESSENGER separated from its rocket and began its trip to Mercury about 59 minutes after launch.

MESSENGER then loosed its two solar panels to generate power and switched off its batteries. The event marked the end of the first leg of MESSENGER’s five billion-mile journey to Mercury. Over the next seven years, the spacecraft will swing by the Earth once, Venus twice and Mercury three times before reaching a final orbit around the small planet.

After a year of science observations, the spacecraft will have completed its primary mission.

“The mission ends with a whimper,” McNutt said, adding MESSENGER’s fuel tanks were budgeted to provide enough propellant for a single year around Mercury. “By about 2015 or 2016, gravity will crash [MESSENGER] into the surface of the planet.”

Dovale said NASA’s next science spacecraft launch will come on Oct. 7, when the agency will launch the Swift Gamma Ray Burst Explorer atop a Boeing Delta 2 in a space shot to be staged from Cape Canaveral Air Force Station.


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