Messenger Flies by Mercury

Riding with Robots writes "Today, more than three decades after the last spacecraft visited Mercury, Messenger buzzed just 200 kilometers above the planet's surface. During the encounter, the robotic spacecraft conducted a range of scientific observations, including imaging swaths of Mercury's surface that have never been seen up close before. A few of the first pictures are now available, with many more to come in the next few days."

Comments

Re:Zoom?

[sighted]

Those are just the approach images, the shots taken up through yesterday that show what the probe saw as it was speeding toward the planet. The close-ups taken today will be downloaded and posted over the coming hours and days. http://messenger.jhuapl.edu/gallery/sciencePhotos/

Re:Cant wait

[Mantaar]

Mercury has a dark side? Sort of. It was thought to be tidally locked, until they found out it rotates approx. thrice for every two revolutions around the sun. Mercury has quite a complex orbit, with mercurial days varying between 176 and 58.7 earthen days, as you can read up in Wikipedia

Re:Correction

[the_other_chewey]

The first images from the close approach will not be available until 01/05/08

Could we please use unambiguous date formatting?
Something like YYYY-MM-DD?
I guess you actually meant 2008-01-15 with a typo.

Re:Correction

[the_other_chewey]

How is 2008-01-05 unambiguous?

ISO 8601.
Additionally, I'm completely unaware of anyone or anyplace using
YYYY-DD-MM as a date format, and my googleing seems to confirm that.

Re:Again?

[rk]

Part of the problem, too, is that it's really tricky to get to Mercury due to the amount of delta-v you need to shed Earth orbit, plus unlike Mars, Mercury has a negligible atmosphere which makes aerobraking useless. That's why they did three slingshot maneuvers to get there. The navigation team at JPL has really outdone themselves with this flight, and are to be commended.

It actually takes more delta-v to get to the sun than it takes to leave the solar system from here. This is why that whole "send dangerous waste to the sun" is a really bad idea. It takes a huge amount of fuel and if you miss, you've got a dangerous payload in a highly eccentric orbit that almost certainly crosses the Earth's. What could possibly go wrong? :-)

And maybe it's because I'm a space nerd, but I think MESSENGER is glamorous as hell.

Re:Oops...

[dryeo]

Actually July and August were just renamed. July was Quintilis before being renamed in honour of Julius and August was Sextilis. The year used to start in March (Spring) so the month numbers were correct at one time.

Re:Again?

[rpj1288]

Actually, pointing something towards the sun wouldn't really send your payload into the sun unless you pushed really, really, really hard. To get something to approach the sun using chemical rockets, one must think about the concept of an orbit. An orbit is defined by the object's speed around its central body. Thus, in order to get closer to the sun, your payload would have to drop its orbital velocity to near enough to zero, if you want a fast collision. You would need to use energy to get to the limit of earth's gravitational influence, about 1,000,000km out. At this point, you would essentially moving with the same orbital velocity as the earth with respect to the sun. Escape velocity for Earth is about 11km/s. With respect to the Sun, the Earth has an orbital velocity of about 48km/s. This means that to get you probe to go on a straight line to the sun, you would need 59km/s of delta v, which is a hell of a lot, and delta v is (essentially) directly proportional to amount of fuel you must carry. Now, granted, you could take a more circuitous route to arrive at the sun, and use less delta v, but it would still be a significant fraction of the 59km/s.

With regards to you second question, unless the highly inclined orbit was altered again at perigee and apogee with respect to the sun, your payload would return to the Earth's orbit.

Note: I am not a rocket scientist, at least not for a while, but I have done a bit of interplanetary stuff like this. All the numbers come from google. And it is entirely possible I'm quite mistaken, but I hope this was a bit helpful.