For the second time since last October, the MESSENGER spacecraft flew by Venus on 5 June, using the pull of the planet’s gravity to guide it closer to Mercury’s orbit. This is the closest pass of Venus to date as MESSENGER aimed to cruise 337 kilometers (209 miles) above the planet’s surface. The flyby coordinates with the Venus Express spacecraft currently orbiting Venus, allowing for novel dual-spacecraft observations of the planet.

Prior to the flyby, Sean Solomon, principal investigator of the mission commented, “We need this flyby to reach Mercury, so that’s our primary objective for the Venus 2 encounter. While we pass near Venus, we’ll ensure that the spacecraft and payload remain healthy, calibrate several of the science instruments, and practice many of the observations planned for the Mercury flybys. We’re also going to take advantage of this planetary encounter to make scientific observations that may lead to new discoveries.” During this flyby, Venus’ gravity changed MESSENGER’s direction around the Sun and slowed its speed from 22.7 to 17.3 miles per second—putting MESSENGER on target to fly by Mercury in January 2008.

MESSENGER first flew by Venus in October 2006, increasing the spacecraft’s orbit inclination and reducing its orbital period about the Sun. Venus was at superior conjunction at the time, preventing scientific observations and leading to a two-week blackout in radio contact.

MESSENGER has completed more than 40 percent of its 7.9 billion kilometer (4.9 billion) mile journey to Mercury. Following the this flyby MESSENGER will swing past Mercury three times in January and October 2008 and September 2009. The spacecraft will map most of the planet during these flybys and determine surface and atmospheric composition—data that will aid in planning priorities for the yearlong orbital mission, beginning in March 2011.