NASA's Mercury Mission Ready for Flight

A NASA space probe is itsfinal days on Earth before rocketing on a mission to understand Mercury, thesolar system's innermost planet, early Monday morning.

Sitting atop a Boeing-builtDelta 2 rocket, the MESSENGERspacecraft is slated to launch Aug. 2 at 2:16:11 a.m. EDT (0716:11 GMT) fromits staging grounds at Pad 17B at Florida's Cape Canaveral Air Force Station.Though Monday space shot has a 12-second window for that day, the missionitself has 12 days to loft MESSENGER in order to reach Mercury.

MESSENGER's principalinvestigator Sean Solomon told reporters Saturday that the spacecraftrepresents a boon for astronomers hoping to understand the solar system.

"The family of the fourinner planets...share a common origin, they were formed by the same processes butcame out different," said Solomon, of the Carnegie Institution of Washington,during a prelaunch briefing Saturday. "Mercury is the most extreme of those planets."

MESSENGER, short for MErcurySurface, Space ENvironment, GEochemistry, and Ranging mission, will spend sevenyears in transit and make a number of flybys around all three inner planetsbefore settling into orbit around Mercury in March 2011. Researchers hope the$427 million probe's seven science instruments will answer a number ofquestions about Mercury's surface, interior and magnetic field, as well asprovide clues to the formation of the solar system during its one year orbitingthe planet.

The mission is also NASA'sfirst Mercury probe since Mariner 10, which flew by the planet three timesbetween 1974 and 1975. While that mission gave astronomers their first glimpseof Mercury, it only imaged half of the surface and raised more questions about theplanet's density and magnetic field than it answered.

"It has been 30 years sincewe visited Mercury last," said Orlando Figueroa, NASA director of solar systemexploration, during the briefing. "I was we're long overdue for a visit."

During its lifetime,MESSENGER will be subject to temperatures greater than 800 degrees Fahrenheit(426 degrees Celsius) in an environment where the Sun's intensity can be 11times greater than it is on Earth. The mission is a cooperative effort betweenNASA, Johns Hopkins University Applied Physics Laboratory and the CarnegieInstitution of Washington.

"It's going to be flying ina very difficult environment," said Robert Strom, a MESSENGER science teammember from the University of Arizona who worked on the Mariner 10mission. Strom said that while anorbiter mission to Mercury was always planned as a follow-up to Mariner 10'sflybys, he was especially excited about the robust and hardy nature ofMESSENGER.

"Never in my wildestimagination did I think we would have a spacecraft like this to Mercury," Stromsaid.

The Mercury path

After launch, the spacecraftMESSENGER should take 56 minutes and 43.7 seconds to reach Earth escapevelocity and start its multi-year journey to Mercury, said Kris Walsh, directorof NASA programs for Boeing's Expendable Launch Systems, during the briefing.

MESSENGER mission engineersplan to spend the next few days after launch performing checks to ensure thehealth of the spacecraft.

"We want to make sureeverything is up and running, leading into our first flyby one year later,"said James Leary, MESSENGER mission systems engineer.

That flyby, a swing by Earthin August 2005, is the first of many to help guide MESSENGER on its inwardcourse to the heart of the solar system. Following that first Earth pass, thespacecraft will also swing by Venus, not once but twice - in October 2006 andJune 2007. The spacecraft is expected to take its first look at Mercury inJanuary 2008, on the first of three flybys of the inner planet - the second isset for October of that year, with the final pass in September 2009 - beforereaching orbit in 2011.

"A lot of people have workedvery hard to get to this point, and so far we're good to go," Figueroa said."Launching is only the beginning."

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