Status Report: MESSENGER Passes the Billion-Mile Mark!
March 24, 2006

On March 23 MESSENGER reached the one-billion mile mark, placing the spacecraft about one-fifth of the way toward its destination to orbit Mercury. On that same day, in the early morning hours (UTC), the spacecraft's distance from the Sun was about the same as the Earth's distance to the Sun. "One billion miles and the team and spacecraft are doing well," says Mission Operations Manager Mark Holdridge of the Johns Hopkins Applied Physics Laboratory (APL), where the spacecraft is operated and where it was designed and built.

For a complete look at MESSENGER's journey through the inner solar system, visit the Mission Design section of the Web site at ../../../About/Mission-Design.html.

Flop Positions Spacecraft toward the Sun

The MESSENGER spacecraft performed its final "flop" maneuver for the mission on March 8, pointing the back side of the spacecraft to the Sun until June 2006. This rotation about the X-axis is performed whenever the solar distance increases beyond approximately 0.95 astronomical units (AU), nearly the distance between the Earth and the Sun. At this distance, the solar arrays do not generate enough power to operate all spacecraft components simultaneously, including instruments and heaters. The "flop" is performed to heat the back side of the spacecraft with the Sun. A "flip" maneuver reverses the effect of the "flop" maneuver by pointing the sunshade toward the Sun. This solar heating reduces the need for multiple onboard heaters, providing the necessary power until the spacecraft is closer to the Sun again. Previous flip, flop, and flip maneuvers were performed on March 8, 2005, June 14, 2005, and September 7, 2005. The spacecraft is scheduled to flip back toward the Sun on June 21.

MESSENGER's Science Team Web Site Is Up!

Even though the MESSENGER spacecraft is years away from entering its final destination of orbiting Mercury, the mission Science Team is already very busy collecting scientific data and sharing it with the larger scientific community. Those plans and results are now available on the team's new Web site; http://messenger.jhuapl.edu/soc/index.php. Check it out now to view images and data returned by the MESSENGER instruments from the successful Earth flyby on August 2, 2005, the first of six planetary flybys in the mission plan; see a bibliography of publications by project team members about the MESSENGER mission and related Mercury science, dating back to when NASA first selected the MESSENGER mission in 1999; and access a list of recent presentations about MESSENGER and related science issues made by Science Team members.

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury, and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on Aug. 3, 2004, and after flybys of Earth, Venus and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as principal investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages the Discovery-class mission for NASA.