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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.
Er... The speed of light's pretty quick.
Roughly a billion (10^9) miles per hour, in fact.
Tedious Bloggy Stuff - hooray?
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
Bandwidth it supposed to be roughly 1900 kbps. And that's b, not B.
Quidquid latine dictum sit, altum sonatur.
I submitted a story about this at 7 am, but it got rejected.. go figure.
Anyway, there's already some interesting photos, and more will be arriving during the day. check NASA TV for live video from mission control.
"Luck is my middle name," said Rincewind, indistinctly. "Mind you, my first name is Bad." -- Terry Pratchett
nice image showing gravitonal waves in the ringshttp://spaceflightnow.com/cassini/images/0407 01rings1.jpg
SHE does throw dice.
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
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.
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
The "Cassini" bit is named after Giovanni Domenico Cassini, a famous maths bloke.
a ti cians/Cassini.html
http://www-gap.dcs.st-and.ac.uk/~history/Mathem
http://twitter.com/onion2k
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.
"The photo sequence began around 12:30 a.m., 18 minutes or so after Cassini finished a 96-minute rocket firing to brake into orbit around Saturn. Streaking just above the rings at speeds greater than 50,000 mph, Cassini's narrow-angle camera took a series of snapshots, opening its shutter for just five milliseconds per picture to avoid blurring. Each picture was separated from those on either side by about 600 miles because of Cassini's extreme velocity."
"It takes us about a minute to take a picture and so in the time we shutter the exposure, read out the camera and get ready to take a picture again, we have crossed a thousand kilometers."
They never had a chance to get a close up of the debris in the rings. In fact, it would take a significant effort, timing it just right, to do so; and, they would risking damage by exposing the camera lens to any dust in the path. If you remember, they were turning Cassini so the big dish pointed in the direction of travel to act as a shield against any small objects in their path, as they crossed the rings.
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?
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.
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.
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.
You can listen to it pronounced in Dutch here.
"Look out honey, 'cause I'm using technology" -- Search and Destroy -- Iggy Pop
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).
Yep, it is, according to dictionary.com:
Saturnian ( P ) Pronunciation Key (s-tûrn-n, s-)
adj.
Of or relating to the planet Saturn or to its supposed astrological influence.
Archaic. Of or relating to the god Saturn or his reign.
>insert witty sig file here
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.
"Saturnian" is correct.
"Chronian" is never used, in my experience, although the stem does work into a few peculiar words, like "perichrone" (closest approach to Saturn in an orbit). Even then, I seldom hear those words used.
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.
Passing through rings is not a dangerous thing. The reason being is that the dust that makes up the rings literally has kilometers of empty space between chunks. So much so that the chances of passing through the rings and hitting something are miniscule.
"Science data from the Voyagers is returned to Earth in real-time to NASA's 34-meter Deep Space Network antennas in California, Australia and Spain. Both spacecraft have enough electricity and attitude control propellant to continue operating until about the year 2020. It is estimated that electrical power produced by the RTGs then will no longer support science instrument operation. At that time, Voyager 1 will be 150 times farther from the Sun than the Earth is -- almost 14 billion miles away. "
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.
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?!
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.
Actually, the Mercury orbiter is scheduled to launch August 2nd. Not much time left to axe it. Aside from human exploration initiative, the multi-billion-dollar missions seem at an end. Not exactly a bad thing.t us_repor t_06_29_04.html
http://messenger.jhuapl.edu/news_room/sta
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
Cassini passed through the gap between the F and G rings. So it did, technically, pass through the rings. Just through an empty space between them but still part of the ring system. And as the engine burn slowed Cassini down, it swung down and passed through the rings on the other side of the planet.
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.