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Cassini-Huygens Reaches Orbit Around Saturn
Mick Ohrberg writes "The probe Cassini-Huygens is now officially in orbit around Saturn. Last nights' retro-burn was completed according to plan, down to the second, which in and of itself is an amazing feat, considering all data received is 1h24m old, as well as 900 million miles away. I must say, it was fairly exciting to watch the webcast, and see the signal fade behind the A-ring, and all but disappear behind the B-ring - all in (somewhat delayed) real-time. The SOI (Saturn Orbit Insertion) also saw Cassini-Huygens whisk by Saturn at around 68,000 mph at an altitude of about 12,000 miles from the cloud tops - the closest to the gas giant the probe will ever be during its planned 4-year mission, for instance the much awaited Huygens mission to Titan."
Not sure when the article was written but there are already raw and press images released as well as some others. The quality isn't as good as some may think and it really doens't show much detail into the rings at all.
Hmmm.
wikipedia has a great bit of information on the history of this project including a section called "Plutonium power source and controversy".
steal this sig
The NAME, I say I say the NAME, son is Christiaan Huygens. Associate of the Protestant Defender and natural philosopher.
Quod scripsi, scripsi.
Bandwidth it supposed to be roughly 1900 kbps. And that's b, not B.
Quidquid latine dictum sit, altum sonatur.
considering all data received is 1h24m old
And we bitch when our CounterStrike match lags 300ms?!
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Won't it be closer when its orbit finally decays to 0?
If you open your mind too wide, people will throw trash in it.
nice image showing gravitonal waves in the ringshttp://spaceflightnow.com/cassini/images/0407 01rings1.jpg
SHE does throw dice.
"It feels awfully good to be in orbit around the lord of the rings," said Charles Elachi, director of the Jet Propulsion Laboratory. "It's going to be a huge leap in our understanding of the Saturnian system.""This has just been an incredible ride," he said. "This wasn't NASA going into orbit around Saturn, it's the Earth going into orbit around Saturn because 17 countries made this happen. This is the way exploration should be done: by the Earth."
if only we could do more things like this
SHE does throw dice.
Try and imagine this small piece of machine, an artificial eye, open to the wonders of our solar system, falling through the infinite depths of space, so that we can forget for a moment, all the troubles and tribulations around us, the cold steel and the raging fire and look beyond the physical confines of what makes us human and gaze in awe at this small contraption carrying a message of hope, of peace, of our thirst for knowledge in a never ending journey towards everything that is unknown.
Rapid Nirvana
Voyager-I took only 9 hours to transmit it's signal from Neptune to Earth in 1998, and that is with 70's technology. So for a probe launched in 97 using superior compression algorithms, it kinda makes sense..
it's called a f'en link - try this next time:
Pretty pictures
Casual Games/Downloads
It would be interesting to see how it looked like meanwhile it was in the ring system?
Or when it was nearby enough to see the massive amounts of rocks inside.
Or didn't it pass through the actual rings?
Beware: In C++, your friends can see your privates!
There wasn't much danger of a serious collision. They passed through a gap in the rings and the probe was checking the region out several weeks ago for possible threats. Besides, Cassini will be using the high-gain antenna dish as a shield when passing through the rings, so the spacecraft itself isn't in a lot of danger.
Just like Huygens I'm Dutch, and thus I was taught a lot about him in school during the physics hours.
The biggest thing Huygens brought the physica is the 'Huygens source'. A simplified explanation: A Huygens source starts sending out sound (air vibration) because the source itself got vibrated by another source. So, a Huygens source doesn't 'create' sound, but simply relays it.
Of course this is really simplified and in reality it's fairly more complex.
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The antenna had to be moved into position to be a shield. You never know what lame part may mess up and ruin the whole show. I think what concerned me (as someone who knows nothing) was that it had to do a few things just right in order to make it and it's really hard to account for all of the variables.
They appearantly sling-shot it by using several planets.
:-\
Check the Spacecraft Trajectory
Appearantly they used nuclear power too.
It's all I could find though
I think we can keep recursing like this until someone returns 1
i believe it seperates from Cassini on the 25th, and lands on Titan 22 or so days later in January
I was at the small (public) meeting held at Goddard Space Flight Center just last night, regarding Cassini's SOI.
Basically they did a few basic things to mitigate risk when attempting this.
- Massive retro burn to decrease velocity: Saturn's gravity was speeding the probe up.
- Aimed at the space between rings so it go through *mostly* empty space... twice, since it had to come back through the rings on its way back out.
- Flipped the craft around 180-degress so the high-gain antenna dish would act as a shield for the rest of the probe. (pretty clever if you ask me).
I'm just happy to see that it worked. Although I wonder what condition the dish is in now.
yes. it is little strange date. BUT - Beagle was not ESA developed - it was private briutish project, his mothership Mars Express was ESA project. Ant she is succesful. And not only lander is ESA developed. Also Cassini itself, the mothership, contains lots of European work.
SHE does throw dice.
It's in there this time. See:
http://www.cnn.com/2004/TECH/space/07/01/cassini.o rbit/index.html
See, you could have listed all of that stuff under 'a lot' like I did in my post. I don't understand you guys and your need to sound smart. :) You didn't have to go to the meeting either. You could have waited and read the CNN.com article like I did. (giggle.. sorry too much coffee) Then you wouldn't have had to leave your house.
considering all data received is 1h24m old, as well as 900 million miles away Recieving old data is easy. Receiving data that is 900 million miles away is very hard. The spacecraft is 900 million miles away. The data must be here, or we could not have received it. ;)
You know its really easy to take for granted the fact that in the last 50 years we have gone from a confined world to launching interplanetary probes billions of miles away. I think we are all a little desensitized from watching too much star trek/star wars and setting our expectations way too high. It really struck me this weekend when i was sitting on the beach with my girlfriend, relaxing and said "the cassini probe is going into orbit around saturn this week." She just smiled, because shes not that geeky, but really, never have humans ever been able to say something like that in matter-of-fact conversation. Now its the norm. Hooray for us:)
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No matter how thin you slice it, its still baloney.
I find myself curious what compression algorithms they are using... is it lossless?
:-)
I was reading an interesting page on how the cameras process the data and on some of the technical aspects regarding the images - the FAQ on the raw images available for downloading.
Apparently, there are both lossless and lossy compression schemes, and it sounds like the compression is done within the cameras themselves - it's not like, say, the Mars Rovers which have a fairly big processor in the middle doing all the work. I don't think it mentions the specific compression algorithms themselves; I wouldn't be surprised if the lossy one is a form of JPEG. I know that was used on Mars Pathfinder, also launched in 1997...
The raw images I have seen are pretty messy, and for trulyspectacular views of Saturn, its rings and its moons it's probably best to wait for them to be processed properly. The FAQ details some of the ways in which they're processed on the ground, too - anyone want a go themselves?
Tedious Bloggy Stuff - hooray?
This is a great day for science and I'm glad that we didn't give into the protesters back in 1997 (to prevent the mission) and 1999 (to stop Cassini from flying past Earth on its way back to Saturn after a gravity slingshot around Venus).
BUT - Beagle was not ESA developed - it was private briutish project ...
So you could say that its life was nasty, briutish and short?
(Badum-TISH!)
I'm sorry.
Tedious Bloggy Stuff - hooray?
Although somebody has pointed out that they did qualify it as the closest approach during the 4-year planned mission, note that Galileo survived 6 years beyond its 2-year planned orbital mission, and sent back data even as they intentionally crashed it into Jupiter to keep if from possibly contaminating one of Jupiter's moons in the future. I wouldn't be surprised if a similar fate is in store for Cassini-Huygens: both a significantly extended mission, followed by a controlled "disposal" when its usefulness has been wrung dry.
While the risk of the Pu RTGs breaking open if Cassini had hit the Earth on those slingshot maneuvers was non-zero, the risk to human health was non-existant. The stupid - 'toxic enough to kill every human on Earth' line was complete BS.
For one, it's know that at least 3 RTGs have burned up on reentry, one US and two USSR. We didn't all die.
Second, while Plutonium is toxic, it's not that bad - caffeine has a lower fatal dose than Plutonium.
Actually, the speed of light in vacuum is exactly 299,792,458 m/s (metres per second)[side note: the meter is defined by the speed of light, the space light travels in 1/299792458 of a second], or 186 000 miles per second. Which is 1116000 miles per minute, or 669600000 miles per hour.
1900kbps (kilobits per second) = 1.9 Mbps (megabits per second). That comes to roughly 237kBps (kilebytes per second). My cable modem at home downloads (normally) at around 350kBps, so that still sounds pretty snappy to me.
Unless I'm missing something, you can take the data and compress it until it's the size of Jessica Simpson's brain but it won't make any difference in the transmission time - 'c' is pretty much constant in this context.
There is no such thing as 'chocohol' or 'workahol'.
It's not several billion - it's only 900 million miles away, plus or minus 2 AUs or so. ;)
Cassini TRAVELED several billion miles to get there - its path looks like an archimedes spiral because of the multiple slingshot maneuvers it used to gain speed. This is also why it took so long to get there.
They did not use the sun's gravitational pull; they used the gravity fields of Venus (twice), Earth, and Jupiter to overcome the sun's gravitational pull.
The "risk" of a Columbia/Challenger type accident - breaking apart from a launch vehicle failure or atmospheric stresses - had nothing to do with the slingshot trajectory, and the RTG was packaged against that contingency. The risk of the slingshot maneuver around earth leading to an accident was infinitesimal.
As the linked article discusses at greater length, the wisdom of the plan was disputed by some, but calling it "very dangerous" is getting close to tin foil hat territory.
Nothing very remarkable. It was launched on a big chemical booster with various upper stages. It then did the usual gravitational dance passing by Venus, Earth (twice) and Jupiter before getting to Saturn. It has a few small rocket engines on board, a biggish one that it just fired for 96 minutes to get into orbit around Saturn, and a bunch of tiny ones for attitude control and fine steering. From here on, though it will basically use the gravity of Saturn's various moons to "bounce" around and visit them.
It does have a nuclear electrical source on board but that is not used for propulsion.
I found the FAQ interesting too, and am truly amazed by the beauty of the images (I definitely want a 6-foot wall poster of Jupiter and the moons).
Given the problems with bits being cut off from images due to time/memory constraints, I wonder if it would be possible to design camera sensors so that the returned pixels are ordered so that you could get increasing resolutions through time ie. First the (even,even) pixel coordinates first, then (odd,odd), finally followed by (even,odd)/(odd,even) so that you'd always get a full image if at a lower resolution.
Vintage computer adverts: http://www.vintageadbrowser.com/computers-and-software-ads
Yes, I realize I should know this one already, but I can't seem to recall ever hearing his name actually said out loud and it aggravates me that I mentally stumble through every instance of his name in print.
This space intentionally left (almost) blank.
Most of our planet names come from the Latin form. Sometimes I see the Greek name used as the adjective. In this case it would be "Chronus", even more awkward.
The retro burn wasn't to mitigate collision danger in the rings, it was to get inbto orbit around Saturn (instead of flying off out of the solar system). The dynamics mean that you get the most benefit from the least fuel by burning it as close to Saturn as possible. Given the difficulty of getting fuel that far, this must be the dominant consideration in the planning of the manouver. Having decided how long they needed to burn and where, then they could consider other issues.
M-W has you covered. Most astronomers I know pronounce it like "Hoi-gens" (hoi like in "a-hoy", gens with a hard g).
(plonk!)
of course i wanted to write density waves :) my mistake. "Look at that structure, it's so regular!" marveled imaging team leader Carolyn Porco as a picture came in showing well-defined bands of brightness and darkness. "I'm wondering if we're looking at a density wave. This looks like it might be a density wave, but I'm not quite sure."
Density waves, caused by gravitational interactions with nearby moons, are thought to be "kissing cousins" of the waves that produce the spiral structure seen in galaxies like Earth's Milky Way.
"These are regions where the rings are communicating gravitationally with the moons exterior to them," Porco explained. A few moments later: "Oh my God, look at that! ... These density waves are like books, just waiting to be read."
story
SHE does throw dice.
thanks the other poster for the correction. the article is here i just mistaken the words :)
SHE does throw dice.
The "slingshot" maneuver is a pretty common with deep space missions. The reasoning behind it is to not only speed up the spacecraft, but also conserve fuel. Conserving fuel may be more important than you think. Fuel is heavy and the more you need, the heavier your spacecraft will be. The heavier your spacecraft, the more fuel you'll need to turn since you're trying to turn a heavier object. An easy way to gain speed without using much fuel is to use the gravity of the planets. Cassini flew by Venus twice and then Earth once picking up more and more speed each time until it went by Jupiter. It picked up some final additional speed from Jupiter's gravity and now a few years later, here we are at Saturn.
It's a common misconception that the plutonium would have caused catastrophe should the rocket have exploded. Had the rocket exploded on takeoff, the total land area infected would have been quite small. Only if you were present at the launch would you need to be concerned. If the rocket had gotten into the higher atmosphere before exploding, the plutonium would have dissapated to the point that it wouldn't have much of an effect. Even if the plutonium stayed concentrated, again it would have only affected a small area as in the case of exploding seconds after launch. In short, even if the worst had happened, it'd be localized and not something which would kill all life around us. I am much much much more concerned with the health risks of breathing in smog around JPL rather than worried about JPL's RTGs.
Indeed. But who knows what kind of monstrous compression algorithms they're using. I read that we're still receiving data from Voyager 1. I couldn't find any data on the transmission speed, but considering it's 8.4 billion miles out, signals taking 10 hours to reach it, and this time increasing by 30 minutes each year. It's estimated that the fule supply will run out around the year 2020.
Quidquid latine dictum sit, altum sonatur.
Are you saying that the speed of light has increased with technological improvements?/p?
Trollish , if partially true. Saturn sans rings is probably, though debatably, marginally less interesting than Jupiter. Stuff like the uncertainty over the length of its day shows that it has some surprises in store, though.
But Titan sure has to be the most interesting object in the Solar System at the moment, if only because it's the biggest bit of unexplored surface left. The good probability of extraterrestrial oceans is also pretty damn cool. Go, Huygens!
Don't know where you got that....but it's too high. From JPL: "3-axis stabilized; power supplied by 3 RTG (628W at EOM); 4 meter HGA supporting S-, X-,Ku-, Ka-band signals, X-band telemetry at 249 kbps, 2 backup LGAs for emergency commanding..."
So ~250kbps max but I doubt they get that at saturn orbit, it's probably more like ~120-140kbps. Compare to mars rovers direct to earth 11kbps and 256kbps for the through-orbiter relay.
- "Hear that?! The percolations are imminent! Cease your ingress!"
This image shows all three imaging problems. There appears to be a short cosmic ray streak in the lower left quadrant veering about 30 degrees downward and to the right, there may be some speckle in the black band or it may be a real signal (the white dots in the black band) and there's banding throughout the entire image that spreads from the white regions to the black and back to the white.
What is that horizontal waviness in the picture?
There is a low level source of noise in the camera's signal as it comes out of the sensor and gets converted to numbers. This noise adds and subtracts a small amount to the signal in a cycle. When the data is put into an image, one can see it as bright and dark bands in the image. The amount of noise is very small and is not noticeable in most images. Images that are of black sky or very dark can show this noise. The camera records the baseline of the signal for each line so this noise can be removed in later processing. Both cameras are affected by this noise but the Narrow Angle Camera is worse.
Next to the earth, Titan may be the most chemically complex body in the solar system. It remains to be seen if it geologically complex. I have a feeling the real show will start tomorrow with the first Titan flyby. Cassini should be able to see/detect liquid hydrocarbons if they are there with IR imaging, IR spectrascopy and radar. A major world is about to be revealed with some of the best instruments ever flown.
an ill wind that blows no good
Bandwidth it supposed to be roughly 1900 kbps. And that's b, not B.
That's actually quite a lot... that's 1.9 Mbps.
Some examples of bandwidth needs:
MPEG2 encoded for standard play on DVD - 2Mbps
Typical DivX encoding - 1Mbps
High res MP3 - 300 Kbps
Compare it to ADSL, which in my area tops out at 1.5 Mbps on the downlink, and Road Runner, which until May was only guaranteeing 2Mbps on the downlink. And those companies have a copper wire that goes into my home; that 1.9Mbps is being broadcast over huge distances with two puny little radio dishes on each end...
I am disrespectful to dirt! Can you see that I am serious?!
Can anyone explain the seemingly horizontal waves that are running through all of the rings? They seem to be fairly uniform and direction and size. However, the orientation does not seem to be radial from the planet itself or any other object... Any conjecture out there as to what has caused this? They almost seem like an artifact in the images themselves.
Also, is anyone else a little disappointed that these are the best images we're going to get of the rings or are there going to be better pictures in the future? This is the closest the spacecraft is going to get to the rings, yet I really was hoping to see the individual components of the rings themselves. I've seen the intro to Voyager, and I wanted to see tumbling boulders...
Is Cassini the last of the billion-dollar deep-space probes? I don't see much else funded. Theres and on-again, off-again flyby to Pluto next decade. The Mercury probe Messenger was axed in the current White House budget. The next four launch-cycles to Mars are being worked on. But these are relatively inexpensive, small things in the couple hundred million range. Maybe a few more lunar and comet missions in the works too.
The previous NASA administrator Goldin promoted the faster-cheaper-smaller (and less reliable) probe model. I guess the initial Hubble troubles and the decade-long Galileo & Cassini projects spooked him out. At least Cassini will last for 4 to 10 years.
Second, while Plutonium is toxic, it's not that bad - caffeine has a lower fatal dose than Plutonium.
While I agree with the gist of your point, plutonium is fairly toxic. Death from a month comes from quantities as low as 50 mg inhaled; 80 micrograms inhaled is probably sufficient to cause cancer. Ingestion LD-50 is estimated to be 500mg or so for an average sized person.
LD50 of caffeine is 150mg/kg, give or take, or 10 grams ingested.
It's nowhere up there with neurotoxins; and it certainly couldn't wipe out all life on earth. But an (extremely) low probability event could kill a few hundred people.
I have to comment on this to say it's completely wrong. The fastest anything could go in the solar system using gravitational assists is still on the the order of 10s of km/s. This is because, from the planet's point of view, the incoming speed is the same as the outgoing speed. Only because the planet is moving is any energy gained. Therefore, the absolute maximum speed increase from going around a planet is your initial speed plus twice the planet's speed around the sun (on the order of 10 km/s). As the speed increases, the planets are less able to deflect the orbit, so less and less is gained from encounters
I don't know if this has already been mentioned, but there are 616,800 hand-written signatures from 81 countries on a disc inside Cassini. I remember when I was in 7th grade and my entire class sent in our signatures to NASA. Now it's seven years later and my name is billions of miles away in space. How cool is that?
see sig. see sig run. run sig run.
Actually, the RTGs are shielded even more than the typical black box in a jet. They are specifically designed to withstand a rocket blowing up or re-entry. So the only real worry is being hit in the head as it comes down. So, at most, one person may be killed by an RTG.
There's also the error correction code they're using (Viterbi-encoded convolution codes) which multiplies the amount of data the probe has to send by a factor of 6.
A probe sent today would use Turbo codes or LDPC (Low Density Parity Check) codes, which nearly reach the Shannon limit for channel capacity. The Shannon limit is a theoretical limit -- we could get faster encoders and decoders than LDPC codes (encoders particularly need work), but they're about at the end of the road for channel capacity. (These codes will work on 1s and 0s, but they can also take into account the analog strength of each bit measured to improve their performance. Decoding them involves iteratively forming and testing beliefs about what an encoded codeword should decode to.)
I wasn't able to locate what error rate can be corrected by the Viterbi code they're using now, or how much lower their bitrate could be with the same amount of correction if they were using a code that met the Shannon limit. Help?
My sibling poster handled the comment about independent action; I'll just add a thought on the delay factor, in general. I'm not familiar with Cassini's design, but I work on geosynchronous satellites, including their ascents to orbit. Most designs are capable of stored commands, which allow the ground to program a maneuver in advance. These programmed maneuvers can be time-tagged to specific epochs. So, as long as you have a solid, synchronized timing source on the satellite/probe, you're able to get the maneuvers to come off at any time you want with relative ease. Of course, the trick is knowing the correct time for a particular maneuver. For this, orbital analysts have fairly sophisticated tools and the smarts to use them. Yes, it is all in the planning.
...they passed through the ring plane, in the huge gap between the F and G rings.
Passing through the rings themselves would likely have been disastrous.