Huygens Probe Lands on Titan

WillDraven writes "CNN, NASA and the ESA are reporting that the Huygens space probe has entered the atmosphere of Saturn's moon Titan after traveling 2.2 billion miles. Pictures from the moon's surface should be available sometime this afternoon" according to the NASA TV schedule. What we know so far is that Huygens landed successfully and sent at least the carrier signal from the surface to Cassini for 90+ minutes, more than expected, and that Cassini has successfully repointed at the Earth and begun relaying the data it received, beginning with test packets. Huygens now sits on Titan, silent forever, while we wait to see whether or how much valuable data Cassini obtained and can send back. Update: 01/14 17:20 GMT by M : So far: they report zero lost packets in the transmission, but one of the two independent data-collection systems is apparently giving some problems. Update: 01/14 21:40 GMT by J : The news is pretty much all good: a very successful mission. Expect to see many photos within hours, but for now apparently only three have been released. Ice blocks or rolling stones -- let the debates begin!

Comments

Re:Any pics yet?

[dtolman]

Spaceflightnow.com indicates that they are now recieving data - so we could be getting the goods as early as this afternoon...

Minor explanation

[Cyclotron_Boy]

They didn't stop recording data because Huygens went silent. Rather, Cassini had to turn to transmit its load of data. Cassini had to turn for a number of reasons ranging from the azimuth and elevation of the lander (now it is more than a probe...) with respect to the horizon, to the maximum data storage capability of Cassini itself. Not that the poster said anything wrong, it was just misleading. I believe Huygens was still transmitting at least carrier verified by Colorado (not sure which radiotelescope picked it up in the US) after Cassini was tasked to turn away. We just couldn't listen much longer, and Huygens' batteries weren't supposed to do more than 4.5 hours anyway (IIRC).
-F

Re:Minor explanation

[Anonymous Coward]

The main reason that it stopped when it did was that cassini went below the horizon with respect to huygens, making it impossible to relay. It was always planned this way, since the only way to get a longer window would be for cassini to burn ALOT of fuel (probably more than it's carrying), and enter titan orbit. We may see a carrier signal from huygens well after the data relay window is over, but huygens doesn't have the transmitting power to get real data directly to earth without the relay.

Re:Minor explanation

[Cyclotron_Boy]

Correction: Since the internal temperature of the probe has been recorded as 25 degrees C (while outside the probe is much colder), the batteries could last as long as 7 hours. However, the transmitter onboard isn't strong enough to get data to Earth directly without a relay (like Mars Orbiter for the Mars Rovers).

Re:Regarding the permanent silence of Huygens...

[FortKnox]

Two reasons:
1.) Its antenna is only strong enough to send signals to cassini, and cassini only 'see' Huygens for so long before it sets over the Titan planet.
2.) Its battery life is very short (because they knew they'd only have such a short time to transmit the data to cassini).

The planet IS harsh (like -290F), but its built to survive it long enough to talk to Cassini until it sets.

GO ESA!

[segal_loves_pandas]

This part is an European Space Agency project. You can find out more at: http://www.pparc.ac.uk/Nw/cassini_huygens.asp There is a link to the ESA/PPARC webcast there too. (PPARC is th British Research Council for Particle Physics and Astronomy.

images to be posted at ...

[MoobY]

The images will be posted from the moment they are available at

http://www.lpl.arizona.edu/%7Ekholso/data.htm

Re:Congrats to the ESA

[slungsolow]

Here is a page with the examples of the image output.

http://www.lpl.arizona.edu/~kholso/test_images.htm

Pretty neat.

Re:stupid hippies avoiding danger

[maynard]

Citations please.

I'm not technically competent to argue the safety risks. I do think the debate is worth engaging, and I definitely think using terms like "stupid hippies" to define those arguing in the opposition helps no one understand the deeper issues. So, your references: the Wikipedia article on plutonium appears to debunk the statement "most toxic sumstances known to man" by comparing plutonium to highly toxic organics like boltulism among others. I assume it's an LD50 comparison.

All isotopes and compounds of plutonium are toxic and radioactive. While plutonium is sometimes described in media reports as "the most toxic substance known to man", there is general agreement among experts in the field that this is incorrect. As of 2003, there has yet to be a single human death officially attributed to plutonium exposure. Naturally-occurring radium is about 200 times more radiotoxic than plutonium, and some organic toxins like botulism toxin are still more toxic. Botulism toxin, in particular, has a lethal dose in the hundreds of pg per kg, far less than the quantity of plutonium that poses a significant cancer risk. In addition, beta and gamma emitters (including the C-14 and K-40 in nearly all food) can cause cancer on casual contact, which alpha emitters cannot.

However, the author(s) note:

However, it must however be noted, that in contrast to naturally occuring radioisotopes such as radium or C-14, Plutonium has been manufactured, concentrated and isolated in large amounts (100s of metric tons) during the cold war for weapons production. These piles (whether in weapons form or otherwise) pose a significant toxicologic risk - not least due to the fact that there is no feasible known way to destroy them (whereas that can be easily done with biological posisons).

--M

Plutonium Toxicity

[caveat]

From the excellent Nuclear Weapons FAQ:

Although plutonium presumably exhibits chemical toxicity like other heavy metals, this effect is insignificant (in fact, unobservable) compared to its radiotoxicity. Plutonium's toxic properties are due to the fact that it is an active alpha emitter. Alpha particles are hazardous only if they are emitted inside the body (i.e. the plutonium has been ingested).
...
Swallowing 500 mg (7 curies) of plutonium as a finely divided or soluble material can cause death from the acute exposure of the GI tract in several days to a few weeks. Inhalation of 100 mg (1.4 Ci) of plutonium as particles of optimal size for lung retention can cause death from lung edema in 1 to 10 days. An inhaled dose of 20 mg (0.28 Ci) will cause death by fibrosis in about 1 month. In doses much below these values, the chronic carcinogenic effects become the important ones.

It's not botulinum toxin, but it IS some pretty nasty stuff to have in you.

Re:stupid hippies avoiding danger

[deglr6328]

"Now if it were a gamma emitter, well that's a very different story"

Right. That's what I'm saying. It IS a gamma emitter too.

Planetary Society's blogging from mission control

[FleaPlus]

I'd like to point out again that Emily Lakdawalla of the Planetary Society is running a blog from Huygens mission control in Darmstadt, Germany. The blog is being updated as events happen.

I particularly enjoyed this quote from the blog:

He [John Zarnecki, the PI on the Surface Science Package] also said that it looks like the probe lasted about 147 minutes, which is 12 minutes longer than the predicted 135, but is "well within the error bars" of the predictions. However, he said this was still an early result--he didn't want to say for certain, because the members of a team had a bet on, and the number "looked suspiciously like the one I picked," Zarnecki said. ...

But, when pushed, scientists can't help doing just a little bit of speculating. That's how they work. So here are a couple of little initial tidbits of speculative potential facts that they have mentioned.

Number 1: Since the probe lasted for a really long time, it's "probably a good conclusion" that the probe landed on a solid, not a liquid surface, Lebreton said when he was pushed. Of course, that doesn't rule out John Zarnecki's "squelchy" surface prediction.

Number 2: One thing that may have helped the probe last a long time was that it appeared to stay unexpectedly warm. At an elevation of only 50 kilometers (about 30 miles) above the surface, her interior was still at a balmy 25 C (77 F), despite the outside temperature being a frigid -180 C (-290 F). Lebreton wasn't ready to say what this might mean. It could be overperformance of the spacecraft, but it could also mean a wide variety of unexpected things about the atmosphere. For those of you who like instant results, I think you'll be disappointed on an answer to this question, because after all Huygens was a mission focused almost entirely on Titan's atmosphere, so it's going to take a very long time to synthesize scientific conclusions from all of this.

Blog address

[SuperKendall]

People might want to know where they can read this blog - the address is here.

Thanks for the info though I did not know the blog existed, and it's always fun to get more intimate details than news reports or press releases can provide.

First picture released!

[BTWR]

here!

Thank Boris Smeds

[csb]

The Huygens probe was saved from probable failure, due to the inability of Cassini's receiver to compensate for the doppler effect:

Titan Calling How a Swedish engineer saved a once-in-a-lifetime mission to Saturn's mysterious moon (by James Oberg)

Without this guy, things would have gone a lot differently! I found this article in RISKS digest 23.65 (always worth a read).