Talk:Cassini–Huygens

From Wikipedia, the free encyclopedia

Good article Cassini–Huygens has been listed as one of the Natural sciences good articles under the good article criteria. If you can improve it further, please do. If it no longer meets these criteria, you can delist it, or ask for a reassessment.
WikiProject Space
Space Portal
This article is within the scope of WikiProject Space.
Good article GA This article has been rated as GA-Class on the assessment scale.
Related projects:
WikiProject Spaceflight WikiProject Spaceflight Importance to Spaceflight: High

This article has been rated but has no comments. If appropriate, please review the article and leave comments here to identify the strengths and weaknesses of the article and what work it will need.
Cassini–Huygens is included in the 2007 Wikipedia for Schools, or is a candidate for inclusion in future versions. Please maintain high quality standards, and make an extra effort to include free images, because non-free images cannot be used on the CDs.
Other languages WikiProject Echo has identified Cassini–Huygens as a foreign language featured article. You may be able to improve this article with information from the French or Portuguese language Wikipedias.

Contents

[edit] Mission, Technology, Content etc

[edit] Contradiction : records of size etc

The Cassini spacecraft, including the orbiter and the Huygens probe, is the largest, heaviest, and most complex interplanetary spacecraft built to date ... Only the two Phobos spacecraft sent to Mars by the Soviet Union were heavier.

Both can't be right.

Maybe it should say: most complex interplanetary spacecraft built by NASA to date? Awolf002 17:58, 18 July 2005 (UTC)
The Phobos craft may have been heavier, but easily arguable as being much less complex. The sentence is a mangled concept and need to be split up. Matt Whyndham 12:29, 30 August 2007 (UTC)


[edit] Trajectory

Hey! What's the "Trajectory" section about?? Is it still being worked on? I can not see what it tries to explain, only that it adds a large graph with no apparent added "value"... Awolf002 14:10, 13 Mar 2004 (UTC)

Yes, the section is still being worked on. You can study the speed differences at planets swingby and manuevers and during the whole mission from the chart, so it's great. Yaohua2000 15:21, 13 Mar 2004 (UTC)

I see. So I suppose you plane to make an extra section with more text? I also would like to know, if you think it might be better related to the Wiki entry Gravitational_slingshot as a great example, since there the focus is actually on the features of the trajectory of space probes. What do you think?

[edit] Detailed Timeline

Another related question to Yaohua2000: Why do we need the entries in the timeline that gives distances? Is there something significant, there?

I think we can drop the "detailed timeline" entries that are only significant because of a "magic number" in the distance, once they have passed. There is no scientific or other value to them after each date. Anyone opposed? I will clean them up starting April, if nobody objects. Awolf002 15:49, 29 Mar 2004 (UTC)

[edit] First orbit

Anyone know how long the first and then subsequent orbits are going to take? There's a wonderful map of the orbit system, but some numbers would be neat. Stargoat 14:56, 1 Jul 2004 (UTC)

I've added the projected schedule of satellite encounters to the timeline page. Also see http://saturn.jpl.nasa.gov/operations/saturn-tour.cfm , though it's not dated orbit by orbit. According to Cassini-Huygens Saturn Arrival June 2004 (pdf), the first three apapsides are around 1 Sept., 2004, 1 Dec., 2004, and 1 Jan., 2005.
--wwoods 02:24, 2 Jul 2004 (UTC)
See my chart "Cassini's speed related to the Sun", which would answer your question.
It's a little hard to get numbers from the graph, though I count three periasides in 2004 and 18 in 2005.
--wwoods 22:51, 2 Jul 2004 (UTC)

[edit] Encounters with Venus

Cassini flew past Venus twice - shouldn't there be a section on that here? Did Cassini make any observations or photos? There's practically no mention of it here... User:Tom walker 11:39 GMT 21 October 2006

probably no observations (no instruments designed for it). This during the gravitational assist part of the trajectory. The main idea is to pick up velocity from the encounters, prior to going outward to the main target. Matt Whyndham 11:44, 30 August 2007 (UTC)

[edit] Titan's Ocean (Dec 20)

I can not find any JPL announcement related to proof that there is a liquid ocean on Titan! I suspect this new section added today is bogus. Please provide a reference, or I will remove it. Awolf002 18:29, 20 Dec 2004 (UTC)

You mean what? where? in the article? — Yaohua2000 18:54, 2004 Dec 20 (UTC)
oic... — Yaohua2000 18:57, 2004 Dec 20 (UTC)

Sorry, will be more precise in the future... It still looks bogus to me. Awolf002 19:55, 20 Dec 2004 (UTC)

Still no answer, and no sign of this being correct... I'll remove that section, now! Awolf002 14:06, 21 Dec 2004 (UTC)

Is the probe designed to sink or float when/if it encounters a body of water?--Confuzion 13:53, 1 Jan 2005 (UTC)

The probe is optimally designed for the descent through Titan's atmosphere, but has a good chance to survive a landing or splashdown. I think if this happens, it can float in a "hydrocarbon ocean" for a while until it sinks due to wave action or small leaks. Note: Nobody expects liquid water on Titan. Awolf002 14:22, 1 Jan 2005 (UTC)
I hardly believe it could sink due to wave action, waves (if any) will tend to be much more gentle there than here on Earth, because of the low gravity. As for small leaks, I don't know, probably there could be some, though if I were building the thing, I'd make it as airtight as possible (except instrumental openings, of course). In any case, battery power and freezing cold will be a much more serious issue once the probe reaches all the way down. --Ugo 22:48, 6 Jan 2005 (UTC)
Well, I heard that Titan has very strong winds, so the "seas" could be pretty rough. And, yes it is the openings for measuring the composition of the atmosphere that might doom the probe in the end. However, I put my money of a "squelch down" and the batteries running out. Awolf002 20:29, 9 Jan 2005 (UTC)
So, I won my own bet. The data received from Huygens is really amazing! It looks to me like it landed on top of a Methane glacier. Awolf002 11:58, 16 Jan 2005 (UTC)


[edit] Instrumentation of Cassini

It would be nice if the instrumentation of Cassini were formatted like that of Huygens. Most instruments on Cassini are more self-explanatory, but if somebody wants to take the time it would be most useful. (unsigned)

[edit] 100 times better?

We are told the "quality of the images was up to 100 times better than anything seen before." What does this mean? Resolution? Colour depth? Rated at 100 times better because of how interesting they are? Can we specify? Thanks! Intrigue 17:05, 27 Oct 2004 (UTC)

When they refer to how much better a picture is than another one, as far as I know it always means resolution. bob rulz 00:24, Oct 28, 2004 (UTC)
(P3d0) "They"? I know the Pulitzer prize, for example, doesn't rate quality by resolution alone


[edit] Huygens

Does anyone else think maybe we should move the section on the Huygens probe off to its own article? There's going to be a huge amount of information added in the next couple weeks and the article is already nearly 50Kb long....--Deglr6328 08:01, 9 Jan 2005 (UTC)

I agree with Deglr6328. Also, how about merge the timeline with the separated main articles? — User:Yaohua2000 13:39, 2005 Jan 9 (UTC)
Unless, of course, Huygens pulls a Beagle or Genesis and is swallowed by Titan without a trace of information coming back. :) Even so, splitting off the existing Huygens material from this article would significantly reduce its bulk; I'd support such a move. Bryan 18:01, 9 Jan 2005 (UTC)
A Genesis? Most of the information in Genesis is coming back. The difference with Huygens if that happens is that no information will be coming back. bob rulz 19:16, Jan 9, 2005 (UTC)
I was originally just going to say "pulls a Beagle", but I didn't want to seem like I was picking on Europe. Genesis was a similar enough recent crash to serve as a NASA analogue so I threw it in too. :) Bryan 00:07, 10 Jan 2005 (UTC)
However, as Bob points out, we got information back from Genesis - many of the aerogel particle traps were intact post landing and not thought to have been damaged or contaminated during the crash. It wasn't a total wash. Not that this takes anything away from ESA for Beagle2, either; BBC reports that some of our Mars Global Surveyor imaging may show Beagle2 landed close to the planned site on the Martian surface - http://news.bbc.co.uk/1/hi/sci/tech/4542174.stm Vfrickey 06:54, 4 Jun 2008 (UTC)
Sounds good to me too. I support. — Knowledge Seeker দ (talk) 02:48, 10 Jan 2005 (UTC)

Since nobody has given any cries of outrage at this idea, I'm going ahead and splitting the article. Huygens probe was a redirect to this article, so I'm using that as the main article for Huygens. Bryan 06:00, 13 Jan 2005 (UTC)


[edit] Huygens' landing site

Would someone like to check my math on the calculation of the angular resolution required to determine Huygens' landing site? [1] Supposedly (we'll see on the 14th of '05) using the VLBA they will be able to determine the landing site to within 1 (ONE!) kilometre on Titan's surface when it is at a distance of 1,200 million km!! [2] I've calculated this to be a resolution of about 17 nanoarcseconds. So far as I know this is the highest resolution astronomical observation ever achieved in any part of the electromagnetic spectrum except for an indirect method done once in 1997 [3] which used a shell of gas around the Vela pulsar as a lens to image down to 10 nanoarcseconds.--Deglr6328 10:21, 26 Dec 2004 (UTC)

You screwed up by a factor of 10,000. One km at 120 Gm is roughly 170 µarcsec. I fixed the article.
One over 120E6 gives the angle in radians (8,3E-10 rad), divide by 2 pi, multiply by 360 times 60 times 60 gives arcseconds (an arcsec is about 4,85 µrad).
Urhixidur 16:51, 2004 Dec 26 (UTC)
That sounds more realistic.--Deglr6328 19:46, 26 Dec 2004 (UTC)


[edit] Huygens data volume

I think someone somewhere didn't do the math properly on this one. I've read in certain places, like here [4] that Huygens will return 400 Mb of data for a full mission (how JPL gets 500MB from 400Mb is beyond me). But I've also read that Huygens will only transmit at ~8000 bits/sec [5]. Now assuming a nominal mission of 2 hours plus .5 hrs on the ground this looks like about 72 megabits or 9 megabytes to me. Where is the mistake here? Is Huygens actually going to transmit faster than this rate?

[edit] Iapetus

The page could do with a mention of the discoveries Cassini-Huygens has made at Iapetus. (unsigned)

details of all the science outputs are probably beyond the scope of WP. Matt Whyndham 12:29, 30 August 2007 (UTC)

[edit] Test of Einstein's theory of general relativity

from reading this section, I don't have a clear picture of what aspect of general relativity is being tested; what do shifts in radio waves nearing the sun have to do with gr? what methods were used in past tests? i.e. why was taking the effort to send cassini on that mission important? --Confuzion 05:38, 12 Jun 2004 (UTC)

Here is the text from the JPL news release:
"According to the theory of general relativity, a massive object like the Sun causes space-time to curve, and a beam of radio waves (or light) that passes by the Sun has to travel further because of the curvature. The extra distance that the radio waves travel from Cassini past the Sun to the Earth delays their arrival; the amount of the delay provides a sensitive test of the predictions of Einstein's theory. Although deviations from general relativity are expected in some cosmological models, none were found in this experiment."
This experiment was piggy-backed onto Cassini, because it provided a very good opportunity. It was a repeat of other space based radio tests, but this one was better designed to evaluate errors due to the interference by the Sun. The primary mission of the spacecraft, however, is still Saturn. Awolf002 12:59, 12 Jun 2004 (UTC)
Since that's a government press release and therefore public domain, I've spliced that paragraph into the relevant section of the article. :) Bryan 19:52, 12 Jun 2004 (UTC)

It may or may not be appropriate to delete this section: A paper detailing the Cassini GR experiment was submitted to GR archives at about this same time (Oct 2003), then withdrawn by John Anderson. http://arxiv.org/abs/gr-qc/0308010 "Improved Test of General Relativity with Radio Doppler Data from the Cassini Spacecraft" Since the paper has been withdrawn, unless there is a peer reviewed paper supporting this story, it should probably be deleted.

I would agree, we might want to at least reword it. Currently, "gr-qc" has no follow up article on this, so we have no idea what the result of the experiment is. Awolf002 00:35, 25 April 2006 (UTC)


[edit] The End of Cassini

What is to become of Cassini at the end of the mission in 2008? After it performs its final task (what is that, by the way?), is it going to remain in orbit of Saturn forever? Or will it fly off into deep space? Or will it crash into Saturn or Titan? (unsigned)

It would probably be crashed into Saturn, assuming that they don't approve an extended mission. I wouldn't be surprised if they performed an extended mission (many of these interplanetary probes have been getting extended missions lately; the rovers on Mars, Mars Global Surveyor, Galileo, etc). bob rulz 21:09, 23 September 2006 (UTC)
There is probably good cause to put in a new article or subsection for the Cassini ultra-extended mission. There is talk about doing a gravity-assist maneuver and flinging it back toward Jupiter (or, at least, Sun-bound) to keep it from crashing into Titan or Enceledus. Here's a summary of the various options being looked at: http://www.sstd.rl.ac.uk/news/cassini/mission/ext.html 147.145.40.43 18:27, 30 November 2006 (UTC)
That's a good summary, and pretty close to the horse's mouth. The decision will be based on the science return for the expended resource (i.e. keeping the mission ops team together for the extra year or whatever). It isn't really about whether other missions have been extended in the past. Matt Whyndham 11:54, 30 August 2007 (UTC)
Not too far outside saturn's gravity well are the Saturn Trojans possibly remnants of the early solar system and objects like Charon that put out cometary discharges. and a good place to die in the end for a plutonium laden spacecraft. could we touch Cassini down on a smaller trojan? we did it with NEAR.--Infocat13 02:23, 25 January 2007 (UTC) (spelling cleaned by Matt Whyndham 11:55, 30 August 2007 (UTC))
Crashing/landing on a moon is unlikely to be favoured because of the risk of biological contamination. Matt Whyndham 11:51, 30 August 2007 (UTC)

a mission to crash the megabomb that is the Cassini probe (it carries almost 3000x the amount of plutonium of the largest nuke ever detonated on earth) into the hexagonal opening at Saturn's pole in an attempt to create a 'second sun' and make it possible to terraform Saturn's moon Titan, maybe? 86.135.164.200 13:01, 5 August 2007 (UTC)

That's just comic-book garbage. The RTG's on Cassini are not explosive. A very specific configuration of material needs to happen for fissile material to be made into a "megabomb". See Nuclear weapon design. Randomly throwing it at a planet isn't among the options. Matt Whyndham 11:51, 30 August 2007 (UTC)
Where has all this "Lucifer Project", "2nd Sun" stuff regarding Cassini come from? Why is there concern around the amount of plutonium on this probe in relation to previous missions? Thanks —Preceding unsigned comment added by 194.221.40.3 (talk) 12:44, 23 May 2008 (UTC)

[edit] RTG

Has a decision been made to crash Cassini into Saturn yet? I didn't think so. Also, if this is done the reasoning is about biological contamination, not radiological. (re main article on 17 Sept 06) 80.177.152.35 23:33, 16 September 2006 (UTC)

[edit] Misc

I removed the "former" from in front of "Soviet Union" in reference to the Phobos probes. Those probes were launched by the Soviet Union, which still existed at the time. Nitpicky, yes...but true. Jumbo 13:29, 1 Jul 2004 (UTC)


[edit] Article, Meta, Wikipedia etc

[edit] References for Featured Article status

If this had inline references, this could easily became a FA. Anybody would be willing to fix this?--Piotr Konieczny aka Prokonsul Piotrus Talk 22:34, 29 January 2006 (UTC)

If you feel that information that should be referenced is not, either flag the article as needing more references (I can't remember the template name), or just write here which stuff should have references. The latter would be better I think. There are about 8 inline references for the instrumentation, which is pretty good. JamesHoadley 08:24, 30 January 2006 (UTC)
Oh, I didn't notice them. Well, if they are converted to proper Wikipedia:Footnotes, we can go for FAC.--Piotr Konieczny aka Prokonsul Piotrus Talk 01:12, 31 January 2006 (UTC)


[edit] GA Re-Review and In-line citations

Note: This article has a small number of in-line citations for an article of its size and currently would not pass criteria 2b.
Members of the Wikipedia:WikiProject Good articles are in the process of doing a re-review of current Good Article listings to ensure compliance with the standards of the Good Article Criteria. (Discussion of the changes and re-review can be found here). A significant change to the GA criteria is the mandatory use of some sort of in-line citation (In accordance to WP:CITE) to be used in order for an article to pass the verification and reference criteria. It is recommended that the article's editors take a look at the inclusion of in-line citations as well as how the article stacks up against the rest of the Good Article criteria. GA reviewers will give you at least a week's time from the date of this notice to work on the in-line citations before doing a full re-review and deciding if the article still merits being considered a Good Article or would need to be de-listed. If you have any questions, please don't hesitate to contact us on the Good Article project talk page or you may contact me personally. On behalf of the Good Articles Project, I want to thank you for all the time and effort that you have put into working on this article and improving the overall quality of the Wikipedia project. Agne 01:09, 26 September 2006 (UTC)


[edit] Talk refactored

I moved the sections of this talk page around, and created two main categories. Some minor (e.g. spelling) changes to talk to improve clarity. Matt Whyndham 12:29, 30 August 2007 (UTC)

[edit] Old talk

Well, shoot! I seem to have screwed something up here and lost the article entirely. Yaohua2000 used copy and paste rather than the "move page" function to move Cassini-Huygens Mission here, which left the article's history behind, and I was trying to rectify that. Bryan 01:25, 12 Mar 2004 (UTC)

Uh-oh, alright. I don't know what to say except good luck. Please note, Yonghua moved the "Cassini probe" page to "The Cassini-Huygens Mission" earlier today. I subsequently moved it to "Cassini-Huygens Mission" as the the "The" was plainly superfluous and then tried to go through various other entries to make sure the wikilinks were up-to-date, esp. those with double redirects. Some time later Yonghua moved the page to just "Cassini-Huygens". Okay, I suppose, but so much for the wikilinks I was trying to update. Why he then altered the Cassini disambig page to point to "The Cassini-Huygens Mission" is beyond me. At this point, I have no further intention to waste any time on this and will get back to work at the office, working on software related to, ahem, the Cassini-Huygens Mission. - Rbs 01:30, 2004 Mar 12 (UTC)
I've posted on the Village Pump, and I think I'm going to go on IRC now to see if there are any developers I can ask about this. Drat, drat, drat. Bryan 01:32, 12 Mar 2004 (UTC)
Okay, I'm suitably embarassed. It seems that it was simply my browser cache preventing me from seeing the history, nothing actually went wrong. Embarassed, and also relieved. Whew! :) Bryan 01:38, 12 Mar 2004 (UTC)
No. It looks like Eloquence fixed it, I assume using an admin tool. - Rbs 01:54, 2004 Mar 12 (UTC)
Actually, I think he was just reverting the article; I didn't do that before I moved it, so there would have just been a #REDIRECT there if everything went correctly. Bryan 02:05, 12 Mar 2004 (UTC)

[edit] Article picture

I don't understand why the picture for this article is so teeny. I made it a bit bigger to fill the large blank void next to the index but someone changed it back. Are people really viewing this page at like 640X480 or something?

I guess that was me (your sig with date is missing, so I'm unsure). If you want to see the full sized picture, you can click on it. So, the size of the picture in the text should be set to fit the "flow" of the text. In my oppinion it was too large and "squeezed" the TOC. Anybody else have an oppinion? Awolf002 15:46, 9 Nov 2004 (UTC)

[edit] pictures

This spacecraft has taken the most extraordinary pictures of the Saturnian system, shouldn't we have an article about the Cassini pictures? I never saw pictures like the ones of this spacecraft. most seem pure imagination, but are real. -Pedro 15:10, 25 October 2005 (UTC)

I think that the commons page for Cassini-Huygens is the closest thing. I've been wondering lately if WP should have some articles based solely around the images, but that's more magazine style, not Encyclopedia style. (I just added a link to the commons page in the article.) JamesHoadley 08:24, 30 January 2006 (UTC)

[edit] Huygens descending--artwork

Came across a new piece of artwork on NASA's site. I don't know enough to know if it's better than the one we have here, although its skies appear even less dark and smoggy. — Knowledge Seeker দ (talk) 11:07, 10 Jan 2005 (UTC)

Most of the artworks are not accuracy enough to the fact. Actually, Saturn will never rise up the horizons at the landing site. But almost all artists make Saturn visible in their work. — Yaohua2000 16:15, 2005 Jan 10 (UTC)

Thanks for letting me know, Yaohua. That's too bad—I would have thought they would have made a better effort to be accurate. — Knowledge Seeker দ (talk) 17:28, 10 Jan 2005 (UTC)


[edit] Explanation of style change

I placed the possessive form back in roman text (Cassini's → Cassini's). The Chicago Manual of Style (15th edition) recommends: "As with plurals, when an italicized term appears in roman text, the possessive s should be set in roman." They give the following examples: "the Atlantic Monthly's editor" and "Gone with the Wind's admirers." This is reasonable since the 's is not actually part of the title and can help avoid ambiguity. I welcome discussion if anyone is opposed to this. — Knowledge Seeker দ (talk) 19:23, 15 Jan 2005 (UTC)

IMHO it should be itallicised "s", like Atlantic Monthly's, simply because it's more readable on the web. I'm not sure if there is an overriding style guide on this (like an official Wikipedia policy or Web Style guide), but failing that any Manual of Style will do. JamesHoadley 08:24, 30 January 2006 (UTC)
Cassini shouldn't be italicized in the first place. NASA doesn't do so on its website for Cassini. Nor does the ESA. It's also not done consistently in the article. Starfire209 (talk) 13:12, 13 March 2008 (UTC)
Nevermind. Although the space agencies don't italicize spacecraft names, it appears that style manuals do. Starfire209 (talk) 14:02, 13 March 2008 (UTC)

[edit] Deletion of Cassini–Huygens abbreviations

For those who may be interested, there is a discussion currently over here at AfD about whether the Cassini–Huygens abbreviations article should be deleted. -R. S. Shaw (talk) 02:18, 14 April 2008 (UTC)


That article has been merged into this one. Protonk (talk) 18:01, 24 April 2008 (UTC)