NASA Spacecraft Set to Shine Spotlight on Mercury

coondoggie writes to tell us Network World is reporting that NASA will this month see the realization of a mission launched in 2004, sent to explore the planet Mercury. "MESSENGER, launched in 2004, is the first NASA mission sent to orbit Mercury, the planet closest to the sun. But on Jan. 14 it will pass close by the planet and use Mercury's gravity for a critical assist needed to keep the spacecraft on track for its ultimate orbit around the planet three years from now. Still, the spacecraft is also expected to throw back some never-before -seen images, NASA said. The flyby also will gather essential data for planning the overall mission. After flybys of Earth, Venus, and Mercury, it will start a year-long orbital study of Mercury in March 2011, NASA said. "

Comments

Re:Why so long . . .

[Deadstick]

It's hinted at in the story, but the reason the probe is taking its sweet time to actually achieve an orbit is Mercury's high orbital velocity.

Well, actually, Mercury's low orbital velocity. It's more than Earth's, but when that elliptical transfer orbit reaches Mercury's orbit, the spacecraft is purely hauling ass. It actually takes a negative delta-V to match velocities.

To reach a superior planet (one outside your own orbit) you initiate the transfer orbit with a positive delta-V, then circularize it with another positive delta-V when you get there. For an inferior planet (inside your orbit), substitute "negative" for "positive" in both places.

rj