The Galileo space probe yesterday concluded its mission by entering the Jovian atmosphere and disintegrating at 1957 hours GMT. During its 14 year mission, Galileo sent back more than 14000 images, and highlights of the mission involved watching a comet crash into Jupiter and finding evidence of large oceans under the ice of Jupiter’s moon Europa.
Galileo really tested the ingenuity of the people controlling the mission at JPL, who firstly had to figure out a way for the probe to reach Jupiter despite having to use a much less powerful rocket to launch it from the space shuttle than originally intended, and then later to find a way for it to complete its mission despite the failure of its high gain antenna, meaning that data could only be transmitted at a much lower rate than originally intended.
However, ways were found, and Galileo ended up being an utterly magnificent success. We criticise the present form of NASA a lot, usually with good reason, but this mission is one that was ultimately got right. To everyone connected with it, might I offer a hearty “well done”. I’ll miss watching the photos and data come in.
The Sun (or possibly the Mirror – occupational hazard of reading tabloids belonging to the person in front of you on the bus) managed one of the best headlines I’ve seen for ages – “Galileo Magnifico”.
Mama mia!
Phew! That’s a relief!
john b: Probably the Sun. They have the best headline writers.
c: Why is it that if you utter the word “Uranium” or “Plutonium”, then otherwise normal people come turn into complete barking moonbats, and conclude that most of the population of Iraq are dying of radiation emissions from U-238 (which are actually close to nonexistent) or that NASA are going to use Galileo to turn Jupiter into a star, or…. One kind of wonders what these people were doing when we were getting educations.
Yes, Michael… although I can’t stand NASA the organization, some of the finest engineers and scientists I know work there and are deeply committed to doing things right.
The problem is, as a certain one of our ex-NASA readers could relate, that the middle management sucks.
Does anyone know why Galileo was intentionally destroyed?…I could understand if it posed a risk of contaminating one of the galilean moons with bacterial life, however from what I know Galileo wasn’t orbiting close to any of them. Just seems strange to me, personally I think we should try to keep as many of our probes as possible out in the solar system and functional…if only to leave as markers for some alien race millions of years from now that comes snooping around to find out why the episodes of Survivor XXXVII stopped being transmitted….
C: Thanks for the link to Badastronomy!!
I have been meaning to peruse some conspiracy sites. I was imagining some of the ‘truth’ they had uncovered as to exactly what happened.
/sarcasm on
NASA wants us to believe it was crashed onto Jupiter, but I want to know what *really happened*. The Truth Is Out There!! This is just another hoax by NASA, just like the Moon Landing Hoax.
I’m so glad we have such clever people who are able to see through all these lies. I bet the folks who work at the HAARP stations have been putting in overtime getting those ‘brain washing waves’ out so we’d believe this latest NASA fable.
Make sure your tinfoil hats are fastened on securely. Don’t fall victim to the ‘HAARP Brainwashing Waves’.
/sarcasm off
Hopefully we’ll land on Jupiter one day and collect the remains of this probe to place in a museum.
I’m surprised that Greenpeace isn’t protesting against NASA for littering on other worlds.
Matt: Once Galileo ran out of fuel there would be no way to predict where it went in the long term. When you have that many large objects exerting forces on a small object, then your uncertainty as to where it is going to be increases steadily as you move into the future. Eventually it gets close enough to one of the large objects that its orbit is changed dramatically, and its subsequent location becomes completely unpredictable. With the possibility of life on Europa and maybe even elsewhere, mission control decided to destroy Galileo now rather than run the risk of it biologically contaminating one of the moons later.
(Even if we could predict the orbits of all the objects in the Jovian system including Galileo forever, there is the possibility of some outside object – say another comet – coming into the Jovian system, too. This could have more or less the same effect – sending Galileo somewhere completely unpredictable).
As Michael says, orbital predictions are handled using what we computer programmers call “brute force”. The program iteratively calculates the position of all objects based on the previously calculated position.
That means that it’s subject to the “butterfly effect” where extremely small errors in describing the initial condition of the system begin to cascade. Eventually your prediction bears no resemblance to reality. (The term comes from weather research, where the use of computers for predictive purposes is subject to the same kind of problems. The statement was that a butterfly taking off in the Amazon today changes the path of thunderstorms in Oklahoma in a year.)
Galileo was in an extremely eccentric elliptical orbit, where it spent almost all of its time well away from the system on the sunward side, and every couple of months made a close pass through the middle of the system. That kind of orbit is particularly vulnerable to cascading change because the exact position of the moons each time it goes through makes a really big difference.
But when you’re talking about the “butterfly effect”, it’s really surprising just how small an influence needs to be in order to throw off the result, if you look far enough out. For instance, the gravitational effect of Saturn and its moons would actually cause small changes which over the course of decades would alter our ability to predict.
All of which means that there was no way to guarantee that it wouldn’t hit Europa eventually, in decades or centuries. There was no benefit at all to leaving it in orbit but at least some risk (however tiny), so crashing it into Jupiter was deemed prudent.
Besides which. the instruments continued to run during its final moments and data was being sent back until the last, and they may actually have gotten some valuable data out of it.
“Hopefully we’ll land on Jupiter one day and collect the remains of this probe to place in a museum.”
It burned up in Jupiter’s atmosphere. And even if any fragments survived, they’d sink deeper into Jupiter’s atmosphere and be destroyed there.
And as to “landing on Jupiter” it’s not at all clear that Jupiter has a surface; that’s not known but it seems extremely unlikely. If there’s a rocky core down there, it is unlikely to be very large, and that deep in Jupiter the atmospheric pressure is so great as to dramatically compress the gas and make it change physical state, to something more like a liquid metal.
But even if there are adequate quantities of heavy elements down there, which form a ball in the center, it would not have a solid surface. Residual heat from the formation of Jupiter is mostly concentrated at its core and it would be well beyond the melting point of the kinds of rocks that make up the surface of the earth. (Even our crust is quite thin, with most of the mass of the planet molten, and we’ve got nothing on Jupiter for inner heat.)
One of my in-laws, Margi Kivelson, was intimately involved in the project, and would be happy to hear your praise. In addition to seeing the end of a project that took so much of her time, her husband Daniel, also a physics professor at UCLA, passed away this summer from sudden onset brain cancer. Tough summer.
Perhaps I’m prejudiced, but I suspect Margi’s involvement made a difference. Smart bunch those Kivelsons. Here’s her son Steve and daughter Val.