NASA MESSENGER Completes Fifty Percent of Cruise Phase

On November 25, MESSENGER will have reached the halfway point in its 6.6-year cruise phase, as measured by travel time. In late January 2008 – shortly after its first flyby of Mercury – the probe’s cruise speed (relative to the Sun) will reach its highest since launch: 62.5 kilometers per second (or 140,000 miles per hour).

Highlights of the first three years, three months of the mission include a flyby of Earth one year after launch and two passes by Venus in October 2006 and June 2007. During the second half of its journey, MESSENGER and its team of scientists and engineers will be even busier.

On January 14, 2008, MESSENGER will fly within 200 kilometers of the surface of Mercury and will be the first spacecraft to pass the planet since Mariner 10 flew by in 1974 and 1975. This first flyby promises to reveal new discoveries. MESSENGER’s instruments will begin to make progress on the mission goals to:

• Map the elemental and mineralogical composition of Mercury’s surface;
• Image globally the surface at a resolution of hundreds of meters or better;
• Determine the structure of the planet’s magnetic field;
• Measure the planet’s gravitational field structure; and
• Characterize exosphere neutrals and accelerated magnetosphere ions.

This flyby event, along with two additional passes by Mercury and three deep space maneuvers, will slow the spacecraft sufficiently for Mercury orbit injection on March 18, 2011.

“The halfway point for MESSENGER’s cruise phase is more than a statistical milestone, because in less than two months we’ll have our first close-up view of Mercury,” offers MESSENGER Principal Investigator Sean Solomon. “From then until the end of the mission, we’ll be peeling back Mercury’s mysteries, many of which have perplexed the planetary science community for more than three decades.”

STAT CORNER

MESSENGER is about 68.5 million miles (110.3 million kilometers) from the Sun and 160.4 million miles (258.1 million kilometers) from Earth. At that distance, a signal from Earth reaches the spacecraft in 14 minutes and 21 seconds. The spacecraft is moving around the Sun at 61,161 miles (98,429 kilometers) per hour.

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 August 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 this Discovery-class mission for NASA.