The MESSENGER spacecraft has a complicated series of planetary flyby trajectory adjustments that allows it eventually to go into orbit about Mercury. A brief summary of the major mission milestones is shown below: a detailed discussion may be found on the mission design page. It is easy to find out where MESSENGER is at any time by going to the orbit calculator. The Delta Velocity in the rightmost column below clearly shows how the planetary flybys change MESSENGER's orbit far more than DSMs.

Adjustments Per Major Event

Event | Date | Rationale | O-Velocity | M-Velocity | ΔVelocity |

Earth | Aug 2 2005 | Reduce perihelion and aphelion | 33.1 km/sec | -- | 5.96 km/sec |

DSM-1 | Dec 12 2005 | Target Venus flyby 1 | 32.7 km/sec | -- | 0.32 km/sec |

Venus 1 | Oct 24 2006 | Reduce perihelion and aphelion Rotate orbit Increase orbit inclination | 35.0 km/sec | -- | 5.46 km/sec |

Venus 2 | Jun 5 2007 | Reduce perihelion and aphelion Rotate orbit Increase orbit inclination | 40.6 km/sec | -- | 6.96 km/sec |

DSM-2 | Oct 22 2007 | Target Mercury Flyby 1 | 40.7 km/sec | -- | 0.20 km/sec |

Mercury 1 | Jan 14 2008 | Reduce perihelion and aphelion Rotate orbit Increase orbit inclination | 41.9 km/sec | 7.1 km/sec | 2.30 km/sec |

DSM-3 | Mar 17 2008 | Target Mercury Flyby 2 | 41.8 km/sec | -- | 0.07 km/sec |

Mercury 2 | Oct 6 2008 | Reduce aphelion Rotate orbit | 43.7 km/sec | 6.6 km/sec | 2.46 km/sec |

DSM-4 | Dec 6 2008 | Target Mercury Flyby 3 | 43.4 km/sec | -- | 0.24 km/sec |

Mercury 3 | Sep 29 2009 | Reduce aphelion Rotate orbit | 45.2 km/sec | 5.3 km/sec | 2.85 km/sec |

DSM-5 | Nov 29 2009 | Target Mercury Orbit Insertion | 45.0 km/sec | -- | 0.18 km/sec |

Mercury 4 | Mar 18 2011 | Mercury orbit insertion | 47.9 km/sec | 3.9 km/sec | 0.82 km/sec |

M-Velocity = MESSENGER's velocity relative to Mercury when closest to Mercury

ΔVelocity = effective velocity change in MESSENGER's trajectory

DSM = Deep Space Maneuver

A more detailed discussion of MESSENGER's trip through the inner solar system can be found in the frequently asked questions page and the mission design page.

Back to the Earth Flyby Images Page

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