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."

Correction

[Kozar_The_Malignant]

>A few of the first pictures are now available, with many more to come in the next few days.

Actually, only a few approach images are available. The first images from the close approach will not be available until 01/05/08 when Messenger has finished data collection and points its antenna towards Earth and begins to transmit data. Can't wait for images of a very harsh environment.

Oops...

[Kozar_The_Malignant]

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

That should be 01/15/08. After 15:00 EST.

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/ [jhuapl.edu]

Re:Zoom?

[CheshireCatCO]

Well, it'll go into orbit eventually, so yes. Hopefully.

And even without getting a lot closer, this is *huge*. Fully 55% of Mercury's surface has never been imaged by spacecraft (and cannot really be imaged well from the ground), so we don't have a very good idea what more than half the planet looks like. This flyby, I'm told, well see about half of the un-imaged area.

great flyby animation

[imipak]

There's a really nice animation on the Flyby 1 page [jhuapl.edu]: 10Mb version [jhuapl.edu], 84Mb version [jhuapl.edu].

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 [wikipedia.org]

A good quick read

[coffee412]

Section of Reworked Venera-13 Image http://www.mentallandscape.com/V_DigitalImages.htm [mentallandscape.com] Checkout the venus pics if you havent already from the link above. Mercury surface pics would be cool.

Re:Cant wait

[CheshireCatCO]

You can't exactly put a base on the "unlit side", though. All sides get sunlight at some point. It's like saying that the humans have built Washington DC on the night-side of Earth: possibly technically true when said, but not very descriptive since that changes.

Re:Correction

[Detritus]

Month names are not portable, they need to be localized. We have an ISO standard (YYYY-MM-DD) for dates, let's use it.

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:Again?

[Tablizer]

This is assuming of course that the garbage is pointed at the sun and timed so it wouldn't get close enough to Venus and Mercury to divert it's course. Why would getting away from the sun be easier than going towards it?

If you point it right at the Sun from ground perspective, it will just come back to circle the Earth unless propelled really hard. One needs to find a way to bleed sun-orbiting speed off of it. There's no free lunch.
         

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.

Re:Again?

[Anonymous Coward]

Using a sail to tack like this works for oceangoing vessels because the hull is sitting in water, and counters the torque of the mast.

In space, with no analogous mass to counter the torque, the force of the solar wind on the sail would reorient the craft until the plane of the sail is perpendicular to the wind.

Re:Again?

[Ihlosi]

Standard movement vector of solar wind (outward) is neglected (slides along the surface), and we're acting only in perpendicular direction, our orbital speed against "zero" component of the speed vector of the solar wind.

Solar sails do not use the solar wind (i.e. charged particles) for propulsion, but the light pressure (photons). Also, you can actually control the direction of the thrust gained from from the solar sail by changing the direction in which the photons are reflected (at the expense of absolute thrust, since the effective area of the sail drops if it does not reflect the photons straight back at the sun).