Cassini/Huygens Mission Update Thread

[centsworth_II]

As I understand it, the larger chute is needed to reduce the speed as the probe drops through the upper atmosphere (after the heat shield phase). As the atmosphere density increases, the smaller chute is needed to maintain the optimal decent speed. If the larger chute were kept, the probe would drop too slowly and communications would end (either when the battery dies or Cassini drops below the horizon) before Huygens reaches the ground. <div class="Discussion_UserSignature"> </div>

 

[bobvanx]

It does seem complex. But the necessity of getting through that very deep atmosphere requires it.<br /><br />Hey, it's less complex than airbags and retrorockets!

 

[fangsheath]

The third chute (stabilizing drogue) is supposed to deploy at an altitude of 110-140 km. There is about a 14-min period between the shield release and the drogue deploy, when the probe is hanging on the main chute. I believe that imagery is being acquired and transmitted during this time, so even if the drogue fails we should get some images fairly close to the surface. Hopefully, of course, everything will work properly. If Tomasko is right, the haze will clear at an altitude of about 70 km and then we should get some really nice views.

 

[Leovinus]

<i>This stereo view of Iapetus was created by combining two Cassini images, which were taken one day apart. The view serves mainly to show the spherical shape of Iapetus and some of the moon's topography.<br /><br />The prominent linear ridge in the center of the dark area -- a place known as Cassini Regio -- marks the equator quite closely. The ridge was first discovered in this set of images and was seen at higher resolution in images taken during Cassini's flyby of Iapetus on New Year's Eve 2004. Some Cassini imaging scientists have suggested that the ridge may have a causal relationship to the dark material that coats the moon's leading hemisphere. The mountain on the left is part of the ridge, and rises at least 13 kilometers (8 miles) above the surrounding terrain.<br /><br />The large basin near the terminator (at upper right) was detected in Cassini images from July and has a diameter of about 550 kilometers (340 miles). The large basin at upper left was newly detected in these images. The crater at far right (within the bright terrain) was known from the days of NASA's Voyager missions. North on Iapetus is towards the upper left. The images were obtained in visible light with the Cassini spacecraft narrow angle camera on Dec. 26 and 27, 2004. Cassini's distance from Iapetus ranged from 880,537 to 716,678 kilometers (547,140 to 445,323 miles) between the two images, and the Sun-Iapetus-spacecraft, or phase, angle changed from 21 to 22 degrees. Resolution achieved in the original images was 5.2 and 4.3 kilometers (3.2 and 2.7 miles) per pixel, respectively. </i> <div class="Discussion_UserSignature"> </div>

 

[bobvanx]

<blockquote><font class="small">In reply to:</font><hr /><p>Some Cassini imaging scientists have suggested that the ridge may have a causal relationship to the dark material that coats the moon's leading hemisphere.<p><hr /></p></p></blockquote>Yep, they are getting ready to tell us it's from Iapetus sopping up an ancient ring.

 

[thinice]

It's a Death Star covered with ice and dust! <br />http://photojournal.jpl.nasa.gov/jpegMod/PIA06166_modest.jpg<br />http://www.theforce.net/swtc/Pix/books/weg/dstc3.gif<br /><img src="/images/icons/laugh.gif" />

 

[retro555]

The article in the link below gives an interesting history of how the Huygens-Cassini communication link problem came to be recognized and solved a few years ago during cruise phase to Saturn. Also of interest to geeks like myself is that the Huygens data rate is 8192Kbps. At 2 1/2 hours estimated transmission time, that gives us a total potential data set of about 74Megabits. Not bad!<br /><br />http://www.spectrum.ieee.org/WEBONLY/publicfeature/oct04/1004titan.html

 

[claywoman]

WoW!!! that was a awesome article!! I'm saving it to read again the day before or during the operation. I'm on tenderhooks waiting for the 14th!!! Let's hope it works...really works well!!!

 

[elguapoguano]

All fingers are crossed as Huygens approaches Titan! <div class="Discussion_UserSignature"> <font color="#ff0000"><u><em>Don't let your sig line incite a gay thread ;>)</em></u></font> </div>

 

[retro555]

Five days to go! One item about the descent that concerns me is the lateral wind speed at the surface. The wind speed in the upper atmosphere is a quick 100m/s. I have heard that the wind speed at the surface is largely unknown. Given the low temperatures and lack of friction to slow molecules down, one could imagine the probe hitting the surface at a large angular velocity - that would not be a good scenario for getting data while on the surface. Comments?

 

[Leovinus]

Well if that does happen, we'll learn from it and do better next time. You said yourself that surface winds are unknown. After this drop, the surface winds will be known. That alone makes it a successful mission even if it crashes. <div class="Discussion_UserSignature"> </div>

 

[najab]

The low temperatures largely argue against high wind speeds at the surface, I would imagine. Since the atmosphere is so thick, there should be little insolation, wich should mean that the lower atmosphere will be less active than the upper.

 

[nacnud]

Low temperature != low wind speed, look at the winds on Neptune (?) 1000kmph!<br /><br />Mind you those winds are at high altitude, at the surface the wind could well be negligible if there is little mixing of the layers in the atmosphere. That’s why it is often still in the mornings, not that the wind has stopped but because the air is less turbulent. Once the sun starts heating the ground the resulting thermals mix up the air again and creat wind on the surface. Perhaps landing at dawn would reduce the risk of surface winds.<br /><br />

 

[llivinglarge]

<i>It's a Death Star covered with ice and dust!<br />http://photojournal.jpl.nasa.gov/jpegMod/PIA06166_modest.jpg<br />http://www.theforce.net/swtc/Pix/books/weg/dstc3.gif<br /></i><br /><br />THAT'S NO MOON!

 

[backspace]

NO LIVE COVERAGE, IMAGES OR DATA RELEASE ON THE 14th. LIMITED DATA RELEASE ON 15th.<br /><br />http://www.thespacereview.com/article/302/1<br /><br />*sigh*<br /><br />ESA needs to look at JPL on this one...

 

[bobvanx]

The Stardust scientists played it this way, too. It was really tough to get the raw images. They could have had a nice media event, but they held tight to their data.<br /><br />It's from the proprietary feeling these scientists and engineers feel towards their ship. They forget that the money came from the public, and so they need to pay the public back. All the science is theirs, for years of investigation and analysis. The moment of discovery and uncovery, of seeing the new info for the first time, tha belongs to everyone.<br /><br />Steve Squyres gets this. No one can take his data away from him. He and his teams worked very hard for years, but sharing the first rush doesn't change that.

 

[yurkin]

Hi retro<br />Thanks for the article. However after reading it I am much more concerned about the Huygens probe then I was before. That was a basic 2nd year engineering problem that they overlooked. The engineers that built Huygens should not have overlooked it. If they screwed that up who knows what else was done wrong. <br />

 

[titanian]

We have superficial indications that winds are not as exceptional as on Neptune. In late may, as Cassini approached the Saturn system, a cloud was detected by Del Genio and John Barbara in distant images of Titan at 38°S.Over two and a half hours the cloud ( mid latitude cloud) moved eastward at a speed of 76 mph.<br />Although the Titan atmosphere keeps all its secrets, Idare to bet that Titan shares many commonalities with Venus in terms of wind speed at the surface and greenhouse effects.<br /><br />www.titanexploration.com

 

[retro555]

Thanks for the info/replies about the winds. I am more hopeful now that the surface science instruments will get their turn. I am personnally enthusiastic about images obtained just after the probe light beam is activated near the surface.<br /><br />Also, after reading the link posted, I too am disappointed about ESL's decision not to show the images live as they are received. As with MER, I want to share in the drama and discovery. Except for Pluto, this is the last major piece of solar system real estate not yet imaged!<br /><br />Note that the Science Channel will run a special about the Titan encounter at 8pm on Thursday.

 

[claywoman]

Unfortunately, I don't get the science channel...we don't have cable or dish...What can I say, I'm poor....

 

[thechemist]

A bunch of CIS and VIMS thermal and compositional data of Iapetus were just released :<br /><br />http://photojournal.jpl.nasa.gov/targetFamily/Saturn <div class="Discussion_UserSignature"> <em>I feel better than James Brown.</em> </div>

 

[elguapoguano]

Settle down there sross. They can't release the data in a live state Huygens is pointed at Cassini, all data is uploaded to Cassini. After it lands, has the data collected (hopefully) and transmits all it's data back to Cassini will the Cassini spacecraft be able to point it's high gain antenna back towards Earth. Even when Cassini transmits data back to Earth because of the distances involved there is a 1 hour and 8 minute time delay. The article mentions the deep space network might be able to hear something of Huygens, If they do Great! If not, we gotta wait. <div class="Discussion_UserSignature"> <font color="#ff0000"><u><em>Don't let your sig line incite a gay thread ;>)</em></u></font> </div>

 

[retro555]

It's not clear if we will see any images on Friday afternoon EST during the 5pm press conference. The DSN will have received the data by then. The Planetary Society's web site has a mission timetime that states initial results won't be released to the public until Saturday.<br />However, the winner of the Society's art contest was announced and at least someone will be at the control center in Germany to see it happen. See link.<br /><br />http://www.esa.int/SPECIALS/Cassini-Huygens/SEMQ35Q3K3E_0.html<br /><br />Note the ESA's control center web cam link.

 

[remcook]

http://ciclops.lpl.arizona.edu/view.php?id=712<br /><br />the huygens landing site

 

[chew_on_this]

This is from Carolyn Porco in an e-mail to myself late last night:<br /><br /><font color="yellow">Entry into the atmosphere begins around 11:15 am Friday, January 14, in <br />Darmstadt, Germany, the location of the Huygens Operations Center, or early <br />morning hours in the States. The first set of images will likely not be <br />available for several hours after that ...p erhaps mid-morning<br />in the western US.<br /><br />The event will be covered live on CNN, and a 20-minute segment of `60 Minutes', <br />to be aired on Sunday, January 16, will be devoted to the Cassini mission, <br />including the Huygens landing.<br /><br />Needless to say, this is one occasion you will not want to miss.</font><br /><br />I agree...