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MESSENGER Mission News
September 26, 2009

MESSENGER on Mercury's Doorstep
MESSENGER is approximately two days from its third encounter with Mercury. If you look at our "Where Is MESSENGER?" page, which displays the spacecraft's trajectory status, you'll see that it is practically on Mercury's doorstep. This will be the team’s last opportunity to practice at Mercury before orbit insertion, so many of the instrument command sequences have been assembled to be similar to how they will operate during the orbital phase of the mission, which begins in March 2011.

MESSENGER’s mission design and navigation teams met Friday at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., to discuss the spacecraft’s current trajectory to determine if a last-minute corrective maneuver would be needed. According to the latest trajectory determination from the navigation team, the spacecraft is very close to its intended flight path, and no correction is necessary.

“The spacecraft is less than 100 meters from the flyby altitude of 228 kilometers,” said APL’s Eric Finnegan, the MESSENGER Mission Systems Engineer. “Once again, the guidance, navigation, and control teams have been successful in passively solar sailing the spacecraft towards the targeted aim point, conserving propellant for potential future exploration.”

On Friday afternoon, the deep space network antennas locked in on MESSENGER for continuous coverage. The command load for the encounter has been completed and verified. The first part of the command load is onboard the spacecraft and ready for execution starting tonight. The spacecraft will continue to gather approach images, while the operations team monitors the spacecraft. You can view the latest image online at http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=328.

The operations and engineering teams will gather in the operations center at APL early Monday morning to make one last assessment of the spacecraft before the closet approach observation sequence begins, rotating the probe away from the Earth to view once again the closest planet to the Sun.

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.

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