Spaceflight History for August 3: MESSENGER

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CalliArcale

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Today, the MESSENGER probe is five years old! (Bearing in mind, of course, that spacecraft usually have a very long gestation period before launch.) On August 3, 2004, it blasted off from Cape Canaveral Air Station's LC17B aboard a Delta rocket. Boosted out of Earth orbit by a PAM-D upper stage, the MESSENGER probe was released to begin its long and roundabout journey to Mercury. Today, it is still en route; it isn't scheduled to arrive into Mercury orbit until 2011.

There is a reason for this, and it's rather interesting. It's intuitively obvious why a spacecraft going to, say, Saturn might take a while. It's a very long ways away. But interplanetary spaceflight is about more than just distance. It's also about energy. The whole exercise is basically a complicated ballistics exercise taking place over a very long period of time. For MESSENGER to be captured by Mercury's gravity and become the first Mercury orbiter, it will need to be close enough to Mercury's velocity vector that it's easy for Mercury to grab it. Too fast, and Mercury will only slow it a bit. Even just getting close to Mercury is challenging; its deep within the Sun's gravity well, and you need to shed most of the orbital energy you get by launching off of the Earth in order to get there. When Mariner 10 was launched towards Mercury in the 70s, they had to do something no unmanned probe had done before -- steal orbital motion from a planet. They launched Mariner 10 towards Venus, aiming it so that Venus' gravity wouldn't *quite* capture it but would slingshot it onto the Mercury encounter trajectory.

MESSENGER has to work harder, because it isn't going to just fly by Mercury a couple of times. It's going to go into orbit and map Mercury over the course of a year. (This will be tricky; Mercury has a strange resonance between its rotation and its orbit; it rotates exactly three times for every two orbits. So much of Mercury is in darkness for long periods of time.) To this end, MESSENGER encountered Earth once and Venus twice, and has already encountered Mercury twice as well. It will encounter Mercury again late next month, setting the stage for orbital insertion in 2011.

So, happy birthday MESSENGER!
 
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3488

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Thanks Calli,

Five years on the go already!!!

The launch window on Tuesday 3rd August 2004 was only 12 seconds long!!!!!!!!!!

Below a Phil Plait (The Bad Astronomer) & BAUT YouTube video giving a summary of the mission.
[youtube]http://www.youtube.com/watch?v=YhEl6ixn3ac[/youtube]

Delta 2 launch vehicle awaiting launch with MESSENGER.






Andrew Brown.
 
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CalliArcale

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I often find myself wondering how bittersweet it must feel to watch the spacecraft you've fussed over for the last few years getting packed into its payload fairing, and how much more so to see it go blazing away in the sky, never to be seen again.... I mean, I've worked with space hardware, but just components. A spacecraft controller doesn't have character, doesn't have *personality* like a whole spacecraft does. And people devote a significant piece of their career to these things. I've heard some compare it to sending your kid off to college. Part of you is sad to see them go, even as you're proud that they're embarking on their voyage.
 
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MeteorWayne

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After that, Calli, it's all in the results, and even before it's primary mission, MESSENGER has delivered.

As the results come in over the next few years, the satisfaction that those who made it happen will be something we can only feel vicariously. For them it is felt in the gut.
 
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3488

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MESSENGER launch.
[youtube]http://www.youtube.com/watch?v=wV4BxqV2m2Q[/youtube]

More MESSENGER related videos.
[youtube]http://www.youtube.com/watch?v=ebqg_KUwT7g[/youtube]

[youtube]http://www.youtube.com/watch?v=_F7qFUmKJHE[/youtube]

I agree Calli,

I can sort of see that. I was involved in the campaign to save Mars Phoenix Lander, New Horizons & DAWN from cancellation.

After going through that, following the developments of the craft, then them being tested prior to launch, then being boarded onto the launch vehicles & with me for some reason, Mars Phoenix Lander, was the worst was the fear of, that rocket may blow up or crash into the Atlantic (Mariner 8 the first attempt to orbit Mars for example), etc.

A sophisticated craft, one that as you say DOES have a personality, does have a purpose, has the potential to produce results that benefit the long term investment in the future of humanity, gets places on a glorified firework!!!! :shock: :shock: :shock: :shock:

MESSENGER is one of my favourite missions of all time, to really properly survey the innermost planet, a planet that has been neglected for far, far too long post Mariner 10.

Already our knowledge of Mercury has been revolutionized by MESSENGER & she has not actually arrived yet!!!!! The first two encounters have shown us a planet that not only has craters & scarps, but also, lava plains, lava flows, volcanoes & a planet that is evolved enough to have a dual layered core (only Earth & Jupiter moon Ganymede otherwise are known to have this unusual feature).

Also the cratering sensities & surface profile suggeasts that Mercury at one time DID keep the same face turned towards the sun (i.e what was formaly the leading hemisphere is more densely cratered than the other side), beofre the impacts that formed Caloris, Tolstoj & the newly found Rembrandt basins spun Mercury to the 2:3 resonance with the Sun.

The primary mission is just going to be awesome. Mind you the upcoming encounter next month will be pretty fascinating too, as that will involve more focussed observations than the previous two, which filled in most of what Mariner 10 missed.

It's a great mission, it really is.

Andrew Brown.
 
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3488

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MeteorWayne":2zx78fmi said:
After that, Calli, it's all in the results, and even before it's primary mission, MESSENGER has delivered.

As the results come in over the next few years, the satisfaction that those who made it happen will be something we can only feel vicariously. For them it is felt in the gut.
It certainly is Wayne.

MESSENGER has already delivered very big time & has already carried out quite a mission & as you say, it's not even the primary mission yet. :shock: :shock:

Andrew Brown.
 
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