June 30, 2004

Spacecraft Cassini-Huygens will pass through Saturn's ring today and then go into orbit around the planet. At 7:11 PM US Pacific time (that's 2:01 AM GMT or 12:11 PM East Coast Australia) the spacecraft will cross the ring before swinging around the planet and crossing it again about four hours later. Hopefully it won't hit anything along the way...

Here is a timeline in US Pacific time. To work out what time it will be in your neck of the woods, you could try using this time zone calculator. 6:10 pm Spacecraft turns so its high-gain antenna can shield the craft from particles as it crosses Saturn's ring plane. 7:11 pm Passing through ring plane, ascending. 7:36 pm Engine begins burn, which will slow spacecraft down so it can be captured by Saturn's gravity. Burn lasts approximately 96 minutes. 8:54 pm Cassini captured in Saturn orbit. 9:03 pm Closest approach to Saturn of entire mission: 19,980 kilometers (12,400 miles) from Saturn's cloud tops. 9:12-9:22 pm Engine burn ends. 9:35 pm Spacecraft begins to take pictures of Saturn's rings. 10:58 pm Passing through ring plane, descending. 12:00 pm Spacecraft regains signal, and sends SOI data back to Earth. And here's a more detailed schedule. Because Saturn's rings are impervious to radio signals the spacecraft will be out of contact for most of period. The first images won't be received on earth until 6:39 AM Pacific Time.

  • ... will pass through Saturn's ring today ... Tee hee! I bet Uranus is jealous. (Sorry)
  • I spent a few moments trying to work out a wording that wouldn't prompt that joke but then I gave up.
  • This is so exciting. I'm gonna be glued to NASA tv all night (thank you DSL).
  • For the timely reminder, thanks, John Hardy.
  • Sorry again, JH. And thanks for the link.
  • QUID!!!! sheesh. ha! but where's the part about the meeting all the aliens? when does that happen?
  • saturn aliens like Dan Dare!
  • Cassini has made the first pass through the ring plane and started the engine burn.
  • WOO HOO!!! The NASA/JPL guys are drinking champagne! This is great! Cassini's passage behind the F ring in less than a minute.
  • Halfway through the burn!
  • The burn went perfectly. It's a good day for science.
  • shinything, official science-as-sports commentator for NASA/JPL. I loved it!
  • Hee. Had to live up to the futbol thread. They're getting the first images from Saturn now. The raw pix showing the unlit side of the rings are from the narrow-angle camera. The detail they're getting is pretty spectacular. Lots of fine wave patterns. Once Cassini swings around to the lit side the images should be even more incredible. This makes me so pathetically happy.
  • Wow. The higher-res pix of the lit side are incredible. latest images
  • This is an excellent thread. Some of these images are amazing.
  • This is completely amazing. I'm so glad I'm living in an era where I can see this happen. *toasts JPL* THANKS!
  • More images with close-ups!! (beautiful)
  • WOW! This is making my whole damn day.
  • Fantastic. We're so lucky to be seeing these as they happen! And thanks for the image links, monkeys.
  • Yeah, thank god we almost blew up the planet to launch this thing! (And no, it was not an illegitimate concern.)
  • Wouldn't be the planet. Maybe a small part of it. Besides, those are some really cool pictures. I mean obviously the risk panned out. It's not like we're talking a 5% chance of failure here. The rocket would be more likely to collide with a plane. Not that things don't happen, but that's a risk NASA seems willing to run. They'd be the first to go if one did go nuclear. Let's do the timewarp again.
  • Scartol has a point. If Cassini came too close to Earth during its 1999 swing-by, an "inadvertent reentry" could've occurred, causing the space probe to break up in the 76-mile-high atmosphere, and thus raining plutonium down onto Earth. In this scenario, NASA acknowledged that "approximately five billion of the estimated seven- to eight-billion population... could receive 99% or more of the radiation exposure." What would be the impact of such nuclear fallout on the Earth's population? One pound of plutonium, if uniformly distributed, could hypothetically induce lung cancer in every person on Earth. Now, nobody argued that this was an imminent scenario, but rather, the calculated risk probability was simply unacceptable. Another example:
    In July 1999 Scientific American ran a letter by Princeton University physicist Frank Wilczek, who pointed to "a speculative but quite respectable possibility" that the Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) could produce particles called strangelets. These subatomic oddities could grow by consuming nearby ordinary matter. Soon after, a British newspaper posited that a "big bang machine"--that is, RHIC--could destroy the planet. The ensuing media flurry led then Brookhaven director John H. Marburger to pull together an outside panel of physicists, who concluded that the strangelet scenario was remote, about a one-in-50-million chance of killing six billion people. (Another panel, convened by CERN near Geneva, drew a similar conclusion.) In Our Final Hour, Sir Martin Rees noted that the chances can be expressed differently--namely, that 120 people might die from the RHIC experiments. He thinks experts should debate in public the merits and risks of such work. Some researchers were not pleased with Rees's position. Subir Sarkar, a University of Oxford cosmologist who considers Rees a true "guru" for his wide-ranging perspective and contributions to astrophysics and cosmology, contends nonetheless that Rees was "irresponsible in making a big deal of the negligible probability" connected with the particle collisions at RHIC. Rees acknowledges that other doomsday scenarios rank much higher in terms of a "risk calculus." Yet he maintains that if the safety criteria used for nuclear reactors are applied--in terms of maximum acceptable probability of deaths multiplied by number at risk--the probability of global catastrophe from any particle acceleration experiment would need to be below about one in a trillion.
    Really, we can't enjoy the benefits of science without confronting the risks. I love what NASA does, and I would love to syphon some of the Pentagon's budget to pay for more space missions... but again, human civilization shouldn't be gambled with, whatever the odds.
  • BTW, can anyone tell me why most of the pics are in black & white?
  • They used the narrow-angle camera with a resolution of 50-135 meters/pixel, and only had a certain number of hours allotted for shooting pix while Cassini was orbiting that close to the rings. Color images take longer to expose, have more data to transmit and often aren't as clear, making ring structure more difficult to view. Yesterday they opted for more images of higher quality. It sounds like color images are scheduled over the next few days. /Cassini nerd
  • BTW Scartol & Wedge, thanks for the links and info about the risks of the mission. I hadn't heard about that aspect of it. Interesting food for thought.
  • Pretty.
  • I ♥ homunculus! Thanks for the updates!
  • My pleasure! It's not just Saturn: Five new moons for planet Neptune.
  • Magnificent!
  • that picture is so astounding. its difficult to process it as "real" that is very cool. thanks homunculus!
  • Jesus lives on Saturn y'know.
  • That's just damned amazing.
  • So awesome Pallas A.. SO. AWESOME. *googly*
  • That's hawt.
  • This thread needs more Holst.
  • Wow that ridge in the last picture is fasckintatin' I won't hold my breath waiting for any new information - NASA goals seem to be more political than scientific. B'zuah?
  • Ribbed for our pleasure.
  • ooooooooh purty!!