New Images from Galileo

deglr6328 writes "New images of Jupiter's Moon Io, along with a false color image of the first isolated ammonia ice cloud discovered on Jupiter; were released yesterday on the Galileo Probe homepage. The probe is currently transmitting back (at it's maximum transmission rate of about 120 Bits per second!) data on previously recorded observations of Ganymede, Jupiter's main ring, Europa and the Jovian Aurorae. Magnetometer measurements that are now being taken in a 100 day survey of Jupiter's huge magnetosphere will be used in a joint investigation with the Cassini spacecraft, which will be making it's closest approach to Jupiter in about two months. After a broken antenna, 5 years in the Jovian environment, 2 extended missions and a total dosage of nearly 4 times the designed radiation exposure, Galileo is still doing spectacular science."

Comments

They're using the Low-Gain Antenna

[RAK]

The reason for the low bitrate is the fact that they are not using the main antenna, which failed to open long ago. Instead the engineers ingeniously reprogrammed the craft to use a low-gain antenna to transmit scientific data. The high-gain antenna was meant to transmit 134,400 bits per second (about one imaging frame per minute). Many software tricks had to be applied, as well as the use of better receiving equipment on earth, for the mission to continue as planned. Prior to the software upgrades, the low-gain antenna had a bitrate of only 8-16 bits per second! See http://www.jpl.nasa.gov/galileo/hg a_f act.html.

Wow.

[glowingspleen]

I don't know what is more impressive:

1) NASA launching a spacecraft of this kind period

2) Having it still work at all

3) Having people smart enough to jury rig it to STILL WORK! Can you imagine trying to fix something MILLIONS of miles away? That's amazing...way to go NASA.

Nearly as cool as these new moons around Saturn!

[ackthpt]

Link to Cornell site (includes photo animation!)

Yep, it's here cuz they rejected my 1337 article!


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28535 Mph

[heroine]

It seems to be going not much faster than it was when it left Earth's gravity. Didn't they perform a number of gravity assists to speed it up?

Re:i knew there was a reason i watched 2001 tonigh

[FallLine]

the chances that a republican offering a hug tax cut will win are pretty fair. if we cut those taxes who do you think will lose out? space, children, the homeles, or corporate welfare? i don't see marlboro as being too worried at the prospect.

Actually, the chances are, if tax rates get reduced, the tax revenues will increase. I know it sounds counterintuitive, but if you look at the emprical evidence tax revenues have actually risen as a result of tax cuts in most every instance. This is true, most notably with Coolidge's, JFK's, and even Reagan's. Now it is also true that there is sometimes accompanying inflation, but on average real tax revenues rise, and when they don't the loss is rather nominal. In short, the odds are slim that Bush's tax cuts will result in a need to cut government spending at all. There is room to spare and fat can be cut without needing to cut programs like NASA, education, or what have you.

That being said, I'm a little worried about Bush's tax cuts overheating the economy at this particular point in time, even though I'm going to vote for Bush.

Aliens watch Laurel & Hardy?

[Sygnus]

This plume bears a striking resemblence to Hardy from the old Laurel & Hardy movies =)

Re:120 bits per second?

[romco]

"You'd think for a few hundred million dollars they'd find something better than an AOL account?"

Galileo was launched in 1989 and probably took
two tears to build. Also keep in mind that "dependable" is far more important than "cutting edge" technology so they would have used older tech. ( I think the space shuttle is just now upgrading to pentiums from 486 'puters).

120bps is pretty impressive.

Home away from home ...

[SuperDuG]

Next generation NASA will start to make space crafts in space ... thus making bigger better spacecrafts ...

where's this post going? Well let's think about it ... if you're going to go somewhere wouldn't you want to know as much about the place as possible before you got there?

yep hence why there's probes. As for the 120 bits per second ... let's see ... how old is gallileo? Yeah that's what I thought ... and is it still working? exactly.

You don't see people whipping out their tandys and saying "hey this will work just fine for me ... it can type add and print" nope ... not NASA ... they've got a rather pricey old POS in space that even if you make fun of it ... it still rocks.

So rock on gallileo ... and would everyone quit whining about the technical specs of a device SO old. BTW ... you can't imagine a beowulf cluster on one of them ... and it doesn't run linux.

Re: some people think Galileo singlehandedly...

[deglr6328]

gave the area of compression algorithms in mathematics something of a kick in the ass, so to speak. IANAMathematician but Galileo doesuse some extremely clever tricks to achieve its mission. Three main types of compression functions are used:

1.)a low-complexity integer cosine transform algorithm, which is an integer-based version of discret cosine transform (ie. JPEG)compression, ICT algorithm, this is new and was developed at JPL.

2.) 2x2 summation mode (which includes a factor of 2 hit on resolution).

3.) Bit Adaptive, Rate-Controlled compression(BARC) a lossless compression

A science virtual machine was created in the the command and data subsystem(main computer) and integrated into the existing operating system to support editing, compression, and packetization of the science data. So Galileo was REPROGRAMMED FROM EARTH (using an upload speed of about 10 bits/second!!) on it's way to Jupiter, with the new compression algorithms. I think those scientists deserve a huge amount of credit for thier achievments.

Data Rate

[Corgha]

Alright, before I hear any more complaints about the data rate, keep in mind that Galileo is 50 light minutes from Earth. It's one thing to get 100Mbps over twisted pair copper between machines a kilometer apart, but quite another to do it by radio over about 900,000,000 times that distance (by some quick back of the envelope calculations) with a broken antenna.

Bottom line: don't mess with NASA -- chances are one of their engineers wrote your network driver.

Corgha

Reason for low data rate...

[Bryce]

When Galileo was built, NASA put a Big Huge Beefy antenna on there, that would deploy like a flower bloom, and provide Lotsa Data.

Now, this is a directional antenna - it puts out lots of data but only in a narrow cone. So they needed a backup antenna, for when the main one was not deployed or if it was not pointed right, just for basic communications (i.e., "Galileo, point main antenna towards earth"). So this antenna is omnidirectional but very small bandwidth (since you don't need bandwidth, after all.)

Yeah, the big one broke. So they have to use the dinky one for all the _data_ communication, too. :-P

This would be like your monitor burning out and having to figure out a way to use your PC speaker to do file management.

Wow, that's cool

[diablovision]

If you watch the Quicktime of Ganymede's plasma waves, you can actually make out a sinusoidal curve in the wave spectrum graph, compliments of special relativity.

politics and the space program

[jesterzog]

For the record, I don't think NASA can be completely blamed for the failed main antenna on Galileo.

Earlier this year I heard Bob Mitchell speaking about Galileo and Cassini - he's pretty much been at the top of both missions. One of the reasons that the main antenna failed to open was because it had to open in the first place, so it was a lot more complicated. (Ideally they would have built it fixed open, like Cassini is designed.)

It had to be redesigned and sent up with the antenna folded up so they could fit it in the space shuttle cargo bay. The reason it had to go up in the space shuttle was because of political interference where people wanted the shuttle to be used for some high profile missions to revive it a bit from the Challenger blowing up in 1986.

Cassini couldn't have the same problems because it was launched with the antenna open. Instead of the space shuttle, they just threw it on the back of one of these, which would have been preferable for Galileo aswell, since they can get much more effective propulsion to kick it off.

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Re:politics and the space program

[tesserae]

It had to be redesigned and sent up with the antenna folded up so they could fit it in the space shuttle cargo bay. The reason it had to go up in the space shuttle even after Challenger was because of political interference where people wanted the shuttle to be used for some high profile missions to revive it a bit from the Challenger blowing up in 1986.

Ummmm... I think you've gotten confused, somehow. Galileo was always intended to be launched by Shuttle. The launch, originally intended for 1982, slipped gradually to May of 1986 through a combination of problems, some of which were Shuttle's own delays (remember how late the first Shuttle actually flew?); the mission was supposed to be orbited with a Shuttle-specific version of the LOX/LH Centaur transstage (the Shuttle-Centaur's funding problems caused some of the delay, too). Of course, in late January 1986 Challenger exploded, so Galileo was temporarily grounded for lack of a launch vehicle.

The only real redesign that happened was when Shuttle-Centaur was finally cancelled, as being too dangerous to launch with Shuttle (liquid oxygen/liquid hydrogen in your payload bay is apparently more dangerous than in your fuel tanks... :p ). The transstage was replaced with the much-smaller Inertial Upper Stage, so the flight plan was changed to a six-year multiple-gravity-whip trajectory through the inner solar system, instead of the orignal two-year direct flight. And during the three-year layoff waiting for Shuttle to fly again, Galileo was shipped from Cape Canaveral to JPL in California and back again, spending some time in storage in the interim. It's believed that the main antenna lost some critical lubricant during this unplanned shipping and storage, and this loss caused etching of the standoff pins and sockets, so the the antenna failed to completely unfurl.

So the mission was always intended to fly on Shuttle -- and Shuttle's problems indirectly precipitated the antenna failure. You're correct in that political interference was the reason the mission was to fly on Shuttle -- but it was NASA who interferred, because they wanted Shuttle to carry all the payloads, instead of using expendable launchers (even when they'd have been more suitable). And once designed and built, it would have been very hard to convert Galileo for a Titan IV launch (for example) -- it was built to interface with the Shuttle payload bay, not a Titan payload fairing.

Unfortunately, it was NASA's fault, pretty much entirely... even though the failure was incidental to everything else which went on. Sad, but true. (I regularly work with some of these guys, and believe me, they feel as bad about it as anyone else -- it's the upper management that's cross-threaded in that org.)

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Re:About the radiation

[tesserae]

Ummmm... you're just talking about the radiation in Earth's upper atmosphere; the radiation environment near Jupiter is a completely different matter.

Remember the Van Allen radiation belts around Earth? They're composed of energetic charged particles (protons and electrons), excited to high energies by the magnetosphere, and are held in their spiraling paths by the terrestrial magnetic field. Before they were discovered (in the late 50's, by James Van Allen), people like Werner Von Braun had planned to put manned satellites in a two-hour orbit -- about 1075 miles up. This turned out to be in the lower Van Allen belt, and the radiation hazard was far too great for safety, so manned spaceflight now is generally in orbits below 250 or 300 miles.

But it's Jupiter we're talking about, and the jovian magnetic field is much stronger than Earth's; the jovian equivalent of the Van Allen belts are millions of times more energetic than the terrestrial belts. Just to give you an idea of what this means to people, compare the exposure at Jupiter (say, in the neighborhood of Io) to that around Earth.

When the Apollo astronauts went to the moon, they had to penetrate the Van Allen belts twice, going out and coming back; in doing so, they received about 2 rem radiation dose. This isn't too much: the U.S. limits radiation workers to about 25 times this, each year, based on the cancer risk. When you talk acute doses -- say, you do a pass by Io, which is in the middle of the jovian belts -- the whole-body exposure which is 50% fatal within 30 days (when untreated) is around 250-300 rad (under these circumstances, 1 rad ~ 1 rem).

Jupiter's radiation belts are millions of times stronger than Earth's, so if an astronaut spent the same time in them (about 3 hours total on a lunar mission -- but Jupiter's much larger, and so your speed would have to be hugely greater to make the transit in that time) they'd get an exposure of millions of rem. In other words, they'd be dead almost immediately -- an exposure of mere seconds would probably be lethal.

Galileo is radiation-hardened, since it was intended to survive in this environment; however, it's been there for almost three times its design limit, and it must be getting pretty fried by now. As a matter of fact, last year when it made its first really close flyby of Io, there was concern that the radiation would corrupt the computer memory and cause it to go into safe mode, or blind the camera's CCD. When that didn't happen, everyone was relieved -- and they promptly did it again!

The radiation environment is severe enough that they actually expect the spacecraft to be physically destroyed in a few hundred million years, if they left it in Jupiter orbit.

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Time to loose more money..

[68030]

This the next place we'll loose a lander to then?

For those keeping score at home...

[Anne Marie]

Jovian clouds are generally understood as comprising three distinct cloud layers: an upper layer of ammonia crystals, a middle layer of ammonium hydrosulfide, and a thick bottom layer of water and ice crystals. It's good finally to see some corroboration from the trenches.

Re:About the radiation

[inquis]

a hell of a lot, considering that the Galileo mission has gone on for much longer than it was really supposed to. Also, empty space does not provide a good barrier to radiation, no matter how you cut it.

rough conversion:

transcontinental airplane flight = 10 - 100 chest exrays. Realize that a) Galileo has been in space for a lot longer than you are on an airplane flight and b) Galileo can't have much more shielding than you would have in that plane (airplane skin + atmosphere + earth's magnetic field)

The aliens that finally find that little satellite will have to take care so that they don't burn their fingers!

-inq

Re:Backup Antenna

[chrissam]

The value of data alone that the probe is obtaining is well worth the value of increasing the transmission ability.

The slow transmission speed is due to the fact that the main (high-gain) parabolic-dish antenna failed to open correctly on its way to Jupiter. According to the JPL web site, the main antenna was supposed to be capable of up to 134 Kbps.

Instead, they had to use the less powerful, omnidirectional backup antenna, which has worked admirably over the years. Go JPL.

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Quick thoughts

[FreeJack1]

I'm kinda wondering why they couldn't transmit the data via laser or a simililar mode of transmission. At 120 bps, there's quite the antiquity of technology! The value of data alone that the probe is obtaining is well worth the value of increasing the transmission ability.

120 bits per second?

[e_n_d_o]

You'd think for a few hundred million dollars they'd find something better than an AOL account?

Did Anyone Notice?

[Anonymous Coward]

Did anyone notice the comet in image 115-A? Look to the right of Eurpoa, above the third star, and you can see it. You can hardly make it out, but once you do, it's quite spectacular. Did anyone else notice this?

As the probe approaches Jupiter. . .

[kfg]

Something wonderful will happen Dave.