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Planetary News: Mars (2004)

MESSENGER Launches for Mercury

By A.J.S. Rayl
3 August 2004

MESSENGER lifted off in a radiant pre-dawn launch from Cape Canaveral Air Force Station at 2:15 a.m. local time this morning [11:16 p.m. Monday night, Pacific Daylight Time] and is on its way to the planet of extremes -- Mercury.

The first mission ever to orbit the planet closet to the Sun was sent on its way by a Boeing Delta II rocket from Launch Complex Pad 17B.

MESSENGER was to have launched yesterday at about the same time, but the still thick and looming clouds of Tropical Storm Alex caused launch officials to call for a 24-hour hold. As forecast, Alex moved northeast toward the Carolinas Monday afternoon, and the weather looked promising at the Cape. At 1:38 a.m., the launch vehicle and spacecraft were reported healthy, and "no weather issues" were in work. It went like clockwork from there.

At 2:05 a.m, the launch manager polled the teams; each reported they were ready to proceed. At 2:10, T -6, the spacecraft was configured for launch and put on internal power, as planned. Then, right on schedule, at 2:15 a.m., MESSENGER soared into the Florida sky.

Following the first burn of the second stage of the rocket, at 2:24 a.m., the spacecraft entered a coasting phase that lasted about 37 minutes and put it over the Indian Ocean. By 3:12 a.m, MESSENGER had separated from the third stage of the rocket and cheers were erupting in the launch control room as the mission set out on its long-awaited voyage.

"That was wonderful," said Launch Director Chuck Duvall. "We have bid MESSENGER farewell."

MESSENGER -- Short for MErcury Surface, Space ENvironment, GEochemistry and Ranging -- sped out of Earth's atmosphere at more than 25,000 miles per hour. But it won't be going straight on to Mercury. Rather, it will follow a 4.9 billion mile [7.9 billion-kilometer] flightpath designed by Chen-Wan L.Yen, of the Jet Propulsion Laboratory (JPL) that will send it looping around the Sun 15 times, and around Earth once, Venus twice, and Mercury three times, before it slips into mercurial orbit in March 2011 to begin a year-long study of this innermost planet.

The Earth flyby, which will occur one year after launch, and the Venus flybys, in October 2006 and June 2007, will use the pull of the planets' gravity to guide MESSENGER toward Mercury's orbit. Then, the Mercury flybys in January 2008, October 2008, and September 2009 will fine-tune and slow the spacecraft's speed by more than 5000 miles per hour while allowing the spacecraft to gather data critical to planning the mission's orbit phase. The spacecraft will then drop into an elliptical orbit that will take it as close to the surface as 124 miles and as distant as 9400 miles.

MESSENGER -- which will rely on solar power for much of its flight -- is only the second spacecraft to set course for Mercury. Mariner 10 flew by the planet three times 30 years ago, and gathered data on about 45% of the surface on three flybys in 1974 and 1975, and found, surprisingly, that it had a global magnetic field, as well as some permanently shadowed craters around the poles. Later ground observations found those craters may contain water ice.

If all goes as planned, the solar-powered spacecraft's suite of seven scientific instruments, which are locked onto its compact and durable composite frame, will send home the first color images of the entire planet, as well as compositional data that will answer the questions raised by Mariner 10's visit.

Mercury is the smallest, oldest, and densest of the inner, terrestrial -- or rocky -- planets, which also includes Venus, Earth, and Mars. It is also planet with the largest daily variations in surface temperature and, of those four, the least explored.

Planetary scientists are interested in knowing more about Mercury because of its extremes, which they believe will shed new light on fundamental questions about the formation of our solar system. "The family of the four inner planets -- Mars, Venus, Earth and little Mercury -- shared a common origin -- they all formed from a disc of gas and dust, the solar nebula that surrounded our young Sun," Sean C. Solomon, principal investigator, Carnegie Institution of Washington, explained during a press conference earlier this week. "They formed by the same processes and formed at the same time and yet their outcomes are extremely different. In order to understand what processes most control differences in outcome, we really have to study and learn about the most extreme of those outcomes - and that's Mercury."

The team will spend the next couple of days checking out the spacecraft "to make sure all the core components are up and ready," James Leary, MESSENGER mission systems engineer, said earlier.

The MESSENGER project is the seventh in NASA's Discovery Program of lower-cost, scientifically focused space missions. The Johns Hopkins University Applied Physics Laboratory (APL), which manages the mission for NASA's Office of Space Science and designed, built and is operating the spacecraft.