NASA Spacecraft Set to Shine Spotlight on Mercury 71
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. "
No, no, no...didn't they read the book? (Score:3, Informative)
Why so long . . . (Score:4, Informative)
It's pretty easy to get into an elliptical orbit which stretches from Earth's orbit around the Sun to Mercury's orbit around the sun. But getting into a circular orbit means matching Mercury's velocity, and doing so in a way that lets a "burn" be made to actually enter into an orbit around the planet. As I recall, you need a total velocity change of 40 kps to get into orbit around Mercury. That more than twice the change required to get into an orbit around Mars.
It's pretty impressive that NASA figured out a way to do this with a gravity assist. A proposed European probe would have used an ion rocket to make the velocity change.
not JPL!! NSFW gay porn video link! (Score:2, Informative)
Scam redirect!
Gay male porn video link in parent!
Re:Why so long . . . (Score:5, Informative)
Not the first mission to Mercury (Score:4, Informative)
"http://www.jpl.nasa.gov/missions/past/mariner10.html"
It was also the first mission to use a gravity assist. At the time of launch the rotation period of Mercury was unknown. By an amazing coincidence, every pass of the spacecraft photographed the SAME FACE of the planet, as its rotation period matched exactly the interval of Mariner 10's return.
Re:Refrence for Mecury day (Score:4, Informative)
http://www.enchantedlearning.com/subjects/astronomy/planets/mercury/ [enchantedlearning.com]
"Until 1962 it was thought that Mercury's "day" was the same length as its "year" so as to keep that same face to the Sun much as the Moon does to the Earth. But this was shown to be false in 1965 by doppler radar observations. It is now known that Mercury rotates three times in two of its years. Mercury is the only body in the solar system known to have an orbital/rotational resonance with a ratio other than 1:1 (though many have no resonances at all)."
Re:Orbital Mechanics FTW (Score:3, Informative)
While its impossible to calculate these trajectories exactly by hand, its easy enough for a computer to do so, and if you can give a rough starting place, optimization techniques will find solution. Trade studies are done to find the best method overall, as in any other engineering practice.
Hope that helps some... it sounds like a fun problem to work out.
Trail blazed by Mariner 10 (Score:2, Informative)
Well it may be the first to technically orbit Mercury, but
Mariner 10 used a Solar orbit to swing-past Mercury three
times.
http://nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=1973-085A [nasa.gov]
It was also the first probe to use plentary gravity assistance,
in this case Venus, to change course. La plus ca change...
Imagery here:
http://nssdc.gsfc.nasa.gov/imgcat/html/mission_page/MC_Mariner_10_page1.html [nasa.gov]
Re:Of course they've never been seen. (Score:2, Informative)
Here's a current map [nasa.gov] of Mercury.
There has been some interesting Earth-based radar observations using Arecibo's radio telescope. These observations give us an idea what to expect to see in the blank areas. Here's a map [unmannedspaceflight.com] combined with radar observations. There are also various recent Earth-based optical observations [skyandtelescope.com] using lucky-imaging techniques, but the images lack detail for accurate mapping.
So to be pedantic the Messenger will take detailed never-before-seen images of never-before-imaged-in-detail and never-before-imaged-at-all -areas of Mercury. In few weeks we'll get a new map of Mercury!