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Emily LakdawallaOctober 18, 2007

MESSENGER is on target for its January Mercury flyby

The MESSENGER mission team reports today that they have successfully completed the deep space maneuver that was designed to line the spacecraft up for its first flyby of Mercury. I'll save my usual spiel about how excited I am about the upcoming flyby (you can read what I had to say about that at the end of my news story on the last Venus gravity assist); suffice it to say I can't wait!

This item in the report from the MESSENGER team caught my eye; it illustrates how many things there are to worry about on space missions even when they're doing relatively boring things like cruising from one part of the solar system to another.

[Shortly after the main engine fired for five minutes], at 6:30 p.m. EDT, the small thrusters were fired for about two minutes, changing the probe's velocity by an additional 1.4 meters per second. This burn redistributed the propellant in the main tanks to manage location of the probe's center of mass, putting the spacecraft in a more stable mode of operation. "This action lowers the risk of having to do momentum correction maneuvers during November, when interference from the Sun will prevent communication with the spacecraft," explained APL's Jim McAdams, who helped design this maneuver.
The animation below shows MESSENGER's circuitous path to Mercury. If you watch carefully you will see "DSM-2" pop up in the animation, very close to the same position as the Venus-2 flyby, and in the upper left corner of the animation you'll see MESSENGER's course very close to the Sun immediately afterward. When MESSENGER is in conjuction with the Sun there is very little (if any) communication possible with the spacecraft; so you can see why it's such a relief for the team to have this maneuver successfully behind them. Onward to Mercury! Only three months left!
MESSENGER's journey to Mercury

NASA / JHUAPL / Carnegie Institution of Washington

MESSENGER's journey to Mercury
MESSENGER's trip to Mercury requires a total of six gravity assists (one of Earth, two of Venus, and three of Mercury) to permit it to enter orbit at the small planet close to the Sun. This animation shows that journey and the motions of Venus and Mercury using a frame of reference that holds the Earth-Sun line fixed.

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Emily Lakdawalla

Solar System Specialist for The Planetary Society
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