Mercury Probe Delayed by Ten Weeks, and Two Years

Gogo Dodo writes "Spaceflight Now reports that NASA's MESSENGER probe launch has been delayed by 10 weeks. Unfortunately, this means MESSENGER will not arrive at Mercury until 2011, a two year delay."

Taking bets...

[Gothic_Walrus]

How long before "Ten weeks != Two Years" is posted by some moron?

Remember, kiddies: Earth isn't the only planet that orbits the Sun!

Re:Taking bets...

[Neil Blender]

How long before "Ten weeks != Two Years" is posted by some moron?

But don't 10 metric weeks equal 2 Imperial years?

Re:Taking bets...

[Tango42]

That would all depend on what the hell you're talking about.

Re:Taking bets...

[freuddot]

Maybe "Ten weeks != Two Years", but according to the article :

Unable to meet that schedule, the mission will use its backup window that begins July 30 and extends 15 days.

[...]

Launch on July 30 will occur during a 12-second window opening at 2:17:44 a.m. EDT (0617:44 GMT) from pad 17B at Cape Canaveral Air Force Station

So, it still looks like a 12 second == 15 days. ;-)

Does I then qualify as "some moron" ?

Re:Taking bets...

[Gothic_Walrus]

I was actually referring to the delays...the launch window has been moved back ten weeks, and the new ETA to Mercury is two years later than the original one.

And since I'm in a good mood...no, you're not a moron. :)

Ironic: Slow Boat to the Fleet-Footed

[G4from128k]

Its ironic that a mission to the fleet-footed god of messages should take so long. I guess its revenge by those ancient Roman gods.

I'm just glad that the mission was not scrubbed.

An Understandable Shame

[Embedded Geek]

I think it's a shame they'll miss the better window, but giving more time to check out the on board diagnostics seems like a dang fine reason. I'd hate to see the thing get all the way to Mercury and then go dead. If the program mangers want this breathing space (and you can be sure they'd only consider this if they were getting a lot of warnings from within the ranks), they'd be fools not to take it. Still, the extra Venus flyby would have been nice (2 vs. 3).

I'm kinda concerned about the budget hit, though. Maintaining an engineering infrastructure on the ground for an additional two years, even one in "standby," is going to be costly. Sure, they can loan out personell to other projects during the interim, but you're going to see two more years of attrition and then retraining costs to catch up. A boom or bust in the tech cycle will simply agravate the situation (boom=more people leaving, bust=fewer new engineers to fill vacated slots).

The delay is probably acceptable, but let's hope the added budget doesn't hurt another probe.

Re:An Understandable Shame

[Ahotasu]

I bet the budget hit won't be significant --at least not due to engineering infrastructure. As an interplanetary mission (with some tricky orbital mechanics to boot), things have already been very thoroughly documented to mitigate the risk of losing knowledge about the system as time progresses. Engineering staff will (still) be busy in the first month or two following launch, then will move off onto other projects. Thus, a boom or a bust in the industry will have little to no effect on the engineering costs associated with this slip.

There's simply not enough work to keep the engineers busy while the bird flys to Mercury--automated data processing as well as monitoring by Operatins staff will take over the job of monitoring health and safety. If problems occur, then the engineers are brought back only long enough to deal with the problems. This has doubtlessly been the plan all along.

Where the cost really goes up, though, is in Mission Operations. Antenna time, operations staff, etc will eat some of the budget. I bet that's fairly trivial, though, compared to your scenario of a 'marching army'. I wonder how MESSENGER's doing in terms of budget reserves (these 'little' dollar signs NASA forces you to hedge)...

The extra time could be bad

[Xolotl]

There is another worry though - the extra two years in space also significantly increases the risk of the probe or its instruments being damaged by solar flares (as happened to Mars Odyssey [bbc.co.uk], radiation, temperature changes and debris.

Why 2 years?

[tjmsquared]

Mercury goes around the sun in 87 days. Assuming that the orbits are circles (they're pretty close) it should never be more than 86 days for the planet to be in an optimal position to launch a probe. So, why would it be off by two years? What am I missing here?

Re:Why 2 years?

[Neil Blender]

Mercury goes around the sun in 87 days. Assuming that the orbits are circles (they're pretty close) it should never be more than 86 days for the planet to be in an optimal position to launch a probe. So, why would it be off by two years? What am I missing here?

Uh, maybe an in depth knowledge of how the gravity of all the planets affects trajectories?

Re:Why 2 years?

[eingram]

This may answer [jhuapl.edu] your question. Either that or just confuse you more. ;P

Re:Why 2 years?

[Curtman]

Why not install Celestia [shatters.net] plug in the dates, and take a look. :)

Re:Why 2 years?

[lommer]

do you have a Celestia update file for messenger (either its planned trajectory, or this revised one)? I'd be interested in getting that if you do

Re:Why 2 years?

[Anonymous Coward]

What am I missing here?


a degree in astrophysics.

Re:Why 2 years?

[CXI]

Because they're planning to swing around Venus to get there, and more than once.

Re:Why 2 years?

[CheshireCatCO]

The links already posted answer the question, but the short, simple answer is "angular momentum". Specifically, the need to dump a lot of it (and, equivelently, a lot of energy). The energy changed needed to get to Mercury is actually greater than that needed to reach Pluto. This means that it's better to use the inner planets (Earth, Venus, and/or Mercury) in gravitational slingshots (but backwards of how we usually use them) to save fuel. In theory, if you jacked up NASA's budget, you could go straight there once a synodic (not sideral: it doesn't matter how often Mercury orbits, but how long it takes to get back to the same relative arrange with Earth) period. But NASA, alas, has a finite budget for this sort of thing, so slow and cheap is the way to go.

Re:Why 2 years?

[joggle]

You're correct. It needs to loose about 62% of its angular momentum, which is a pretty significant amount of energy. This is in addition to the amount of energy needed to reach earth's escape velocity in the first place and to insert into an orbit around Mercury.

Re:Why 2 years?

[Anonymous Coward]

"Loose" needs to lose about 50% of its "o"s, which is a pretty significant amount of "o"s.

Re:Why 2 years?

[lommer]

Um, no, and no.

Angular momentum refers to the linear momentum of the probe times the radius from the sun at which it is orbiting.

As for the energy, It's actually pretty tricky to lose KE + PE in space - you either have to use engines (with expensive-to-launch fuel) or sophisticated aerobraking techniques and whatnot by making close passes to other planets. In fact, when this probe gets to Mercury, if i'm not mistaken, it will still have nearly the same energy (in terms of KE and PE).

Five braking flybys, 3 of them @200km

[leonbrooks]

...which does seem pretty camel-through-eye-of-needle at ranges of tens of millions of km. Venus gets two flybys @3000km and 300km.

This is needed because Earth orbit is about 3x as energetic as Mercury orbit. Messenger needs to dump the other 2/3 of its momentum, and slingshot flybys are far and away the cheapest method for that. This requires eveything to be lined up just so.

It's a pity, really, because I suspect Mercury of harbouring numerous hermeological surprises [nasa.gov] (as surprising as Valles Marineris [nasa.gov] on

Re:Why 2 years?

[adeyadey]

What am I missing here?

Orbital mechanics is a weird game - especially with old-fashioned rockets with limited fuel/thrust, so you have to use various tricks like gravitational boosts/brakes by flying by other planets, in a sort of celestial game of pool. Sure, you could fly straight to mercury, if you use a big enough rocket - but then you would be flying by at such a huge speed you would need an even bigger rocket to carry fuel to allow you to slow down enough to make orbit. Mercury does not have a huge

Good lord...

[shiwala]

...Gates has conquered Earth and now has his sights set on another planet [msn.com]?! Oh, wait...

Who comes up with these?

[Tree131]

I wonder who comes up with these names/acronym mixes? There must be a job at NASA to name all these missions, like
MeSSEnGeR or NOAA or ECHO or SOHO (which stands for many things, including the solar observatory).

http://www.acronymfinder.com/ [acronymfinder.com]

Re:Who comes up with these?

[CheshireCatCO]

Actually, probably the team that proposed the mission in the first place. That's usually where they come from these days. Mercury is a Discovery-class mission, which means that it was proposed out of house, rather than created and designed within NASA.
I don't recongize the ECHO acronymn, but NOAA isn't part of NASA at all (it comes in under the Dept. of Commerce, I believe) and SOHO is jointly run with the European space agency, not a pure NASA endevor.

Coming up with forced acronymns and impressively use

Re:Who comes up with these?

[irokitt]

MeSSEnGeR or NOAA or ECHO or SOHO

So how long until we see names like M3553n93R or N044 or 3(H0 or 50|-|0?

Relativistic effects on the craft & orbit

[RobertB-DC]

To what extent does the "warping" of space near an object as massive as the sun affect this little spacecraft's orbital calculations? I know (but don't fully understand) that there are relativistic effects on Mercury's orbit [ucr.edu] that aren't described by pure Newtonian physics.

To what extent do the mission planners have to account for this effect? Can they even know for sure until they see what happens as they pass by Mercury those three times before orbital insertion? Or will the effect be negligible compared to the solar wind and other "normal" forces? The link above notes that Newton is only off by 43 arcseconds out of 5600, but it seems like even 0.77% could add up pretty quick.

Re:Relativistic effects on the craft & orbit

[egomaniac]

To what extent do the mission planners have to account for this effect? Can they even know for sure until they see what happens as they pass by Mercury those three times before orbital insertion?

Of course they can. We know the speed of the Sun and planets relative to us, and we know all of their masses. That's everything you need to do full relativistic calculations.

And yes, these are astrophysicists we're talking about. Of course they take this into account.

Re:Relativistic effects on the craft & orbit

[MrIrwin]

We know the speed of the Sun and planets relative to us, and we know all of their masses. That's everything you need to do full relativistic calculations.

I believe you also need to know how to convert between imperial and metric units.

Hmm.

[Trejkaz]

The best thing about this name is that if NASA ever develop teleportation technology, they can integrate it into the next version and call it "Instant MESSENGER."