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  Cassini-Huygens at Saturn: Questions, comments (Page 1)

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Author Topic:   Cassini-Huygens at Saturn: Questions, comments
Robert Pearlman
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posted 02-27-2004 06:15 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Cassini-Huygens at Saturn: questions, comments
This thread is intended for comments and questions regarding the Cassini-Huygens mission and the updates published under the topic: NASA's / ESA's Cassini-Huygens to Saturn-Titan.

Cassini launched in October 1997 with the European Space Agency's (ESA) Huygens probe. The probe was equipped with six instruments to study Titan, Saturn's largest moon. It landed on Titan's surface on Jan. 14, 2005, and returned spectacular results.

Meanwhile, Cassini's 12 instruments have returned a daily stream of data from Saturn's system since arriving at Saturn in 2004.

Among the most important targets of the mission are the moons Titan and Enceladus, as well as others of Saturn's icy moons. Towards the end of the mission, Cassini will make closer studies of the planet and its rings.

Philip
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posted 02-27-2004 06:19 AM     Click Here to See the Profile for Philip   Click Here to Email Philip     Edit/Delete Message   Reply w/Quote
Cassini-Huygens is almost at Saturn and its moon Titan...

Scott
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posted 02-27-2004 09:40 AM     Click Here to See the Profile for Scott   Click Here to Email Scott     Edit/Delete Message   Reply w/Quote
Wow! Thanks for the heads up. I read about that Huygens probe last month. It is going to simply parachute down to the surface of Titan (its atmosphere is very thick and this is possible).

Oh man this is all too much. Spirit about to peak into a crater, Opportunity in an outcrop crater surrounded by bunny droppings...and now the Huygens probe... this is so great!

Philip
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posted 06-17-2004 01:19 AM     Click Here to See the Profile for Philip   Click Here to Email Philip     Edit/Delete Message   Reply w/Quote
Amazing images! ...and that's only one of the smaller Moons!

Cassini-Huygens will pass closer to Saturn than any other spacecraft did before. The night of 30th June will be exciting...

Blackarrow
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posted 06-17-2004 04:57 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
I agree, absolutely amazing. But I worry about the orbital insertion. OK, the engine has been tested and seems to be in good condition, but it has to fire for 96 MINUTES NON-STOP to put Cassini into orbit - and the spacecraft has to pass through the ring-plane, uncomfortably close to Saturn. I will breath more easily on hearing that Cassini is in a safe, stable orbit.

Philip
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posted 06-18-2004 01:57 AM     Click Here to See the Profile for Philip   Click Here to Email Philip     Edit/Delete Message   Reply w/Quote
As I said EXCITING... check the animations at NASA Jet Propulsion website.

dtemple
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posted 06-30-2004 10:52 PM     Click Here to See the Profile for dtemple   Click Here to Email dtemple     Edit/Delete Message   Reply w/Quote
Does anyone know what type engine is being used to brake Cassini into orbit around Saturn? I was watching the NASA channel and someone said the engine and its identical backup were originally developed for the Apollo program. Is Cassini using an Apollo SPS?

Philip
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posted 06-30-2004 12:05 PM     Click Here to See the Profile for Philip   Click Here to Email Philip     Edit/Delete Message   Reply w/Quote
Anyone going to stay awake during the almost 100 minutes burn to bring Cassini-Huygens into the Saturnian system?

The spacecraft has been long underway and pasted Venus twice & Earth to get gravity assist pulls to make it, via Jupiter (Millennium fly by), to Saturn. Doing so NASA saved 75 tons of fuel (remember Cassini-Huygens is as large as a school bus!). Signals from Cassini-Huygens to Earth (and back) will take 3 hours! Fingers crossed...

Rodina
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posted 06-30-2004 12:33 PM     Click Here to See the Profile for Rodina     Edit/Delete Message   Reply w/Quote
The ring planes -- beautiful as they are -- are still almost completely empty. The risk of a strike is small.

As for the burn -- Galileo had a 38 minute burn or something -- so while 100 minutes is certainly dicey, it's nothing JPL hasn't tested and retested (and, for that matter, done in practice).

Titan's fascinated me since I was 9 -- so I'm really, really looking forward to the success of the ESA effort. I have no doubt Cassini will do its job -- but it's something we've done -- as for Huygens, ESA is doing something nobody's done before -- and if they pull it off, my hat will be off to our European friends. But I trust that they will.

Philip
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posted 06-30-2004 03:59 PM     Click Here to See the Profile for Philip   Click Here to Email Philip     Edit/Delete Message   Reply w/Quote
Rodina, the Huygens probe will be released by the end of the year... afterwards Cassini will also study Titan's atmosphere with radar.

Philip
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posted 07-01-2004 01:36 AM     Click Here to See the Profile for Philip   Click Here to Email Philip     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by dtemple:
Does anyone know what type engine is being used to brake Cassini into orbit around Saturn?
Not sure really... The main engine is used for spacecraft velocity and trajectory correction changes. To be on the safe side, there are two identical main engines: One is in use and the other is a backup. There are also 16 monopropellant hydrazine thrusters arranged in four groups of four. The thruster engines are used for attitude control and also for small velocity-change maneuvers.

But of course there's the Internet.

Davide
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posted 07-01-2004 05:47 AM     Click Here to See the Profile for Davide   Click Here to Email Davide     Edit/Delete Message   Reply w/Quote
Cassini has entered in Saturn orbit! Looks like the Saturn Orbiter Insertion was a success. I can't wait for the first images of the rings...

AlanLawrie
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posted 07-01-2004 08:56 AM     Click Here to See the Profile for AlanLawrie     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by dtemple:
Does anyone know what type engine is being used to brake Cassini into orbit around Saturn?
The engines are the R-4D 100 lb model manufactured by The Marquardt Co of Van Nuys, Ca and tested in cell 1 there. Marquardt is now owned by Aerojet, Redmond, Wa and the Van Nuys facility was knocked down two years ago.

The engine is a derivative of the Apollo SM RCS and LM RCS engines. The main difference is the nozzle has a higher expansion ratio now and is made from columbium with a silicide coating.

Versions of this engine are used as apogee engines for most of today's geo satellites.

072069
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posted 07-01-2004 09:46 AM     Click Here to See the Profile for 072069   Click Here to Email 072069     Edit/Delete Message   Reply w/Quote
Let's face it, we rock! What a great time for NASA fans

Rodina
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posted 07-01-2004 10:41 AM     Click Here to See the Profile for Rodina     Edit/Delete Message   Reply w/Quote
$3 billion for this? A bargain at twice the price. This is big science at its very, very best.

Davide
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posted 07-01-2004 11:14 AM     Click Here to See the Profile for Davide   Click Here to Email Davide     Edit/Delete Message   Reply w/Quote
Look at the first images of the rings at ciclops.org. They are still not enhanced, but they show thousands of rings. What incredible structure the rings system is...

Philip
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posted 07-01-2004 01:12 PM     Click Here to See the Profile for Philip   Click Here to Email Philip     Edit/Delete Message   Reply w/Quote
It's Cassini-Huygens... don't forget the (European) wok-shaped probe that will be released in Titan's atmosphere by the end of the year!

ALAIN
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posted 07-01-2004 01:31 PM     Click Here to See the Profile for ALAIN     Edit/Delete Message   Reply w/Quote
Okay for the probe, but what's worse, a Belgian commercial TV channel news said that Cassini reached 70000 kilometers per hour when it dove into the opening between the rings?

I believe if Cassini-Huygens would have tried to go into the split of the rings, it would have been bombarded by small rocks and ice... It didn't dive into the rings, it manoeuvred above the ring plane! (correct?)

Davide
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posted 07-01-2004 01:41 PM     Click Here to See the Profile for Davide   Click Here to Email Davide     Edit/Delete Message   Reply w/Quote
No Alan, Cassini-Huygens has crossed twice the rings plane, passing in a division between the so-called F and G rings, one of the small black bands visible on the rings structure.

I believe the maximum velocity of the spacecraft was around 10 km/sec, or 36,000 km/hour.

DavidH
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posted 07-01-2004 01:56 PM     Click Here to See the Profile for DavidH   Click Here to Email DavidH     Edit/Delete Message   Reply w/Quote
Philip, don't be too jealous of Cassini's moment in the limelight -- I'm sure that Huygens will get its fair share of press coverage a little ways down the road.

spaceuk
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posted 07-01-2004 03:14 PM     Click Here to See the Profile for spaceuk     Edit/Delete Message   Reply w/Quote
Congrats to the international teams behind Cassini-Huygens.

Early images fascinating but sure better to come.

No sign of the 'dirty dust' on the rings in early images I've seen - which Voyager spotted? Still - early great days.

Philip
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posted 07-01-2004 03:32 PM     Click Here to See the Profile for Philip   Click Here to Email Philip     Edit/Delete Message   Reply w/Quote
Nice to see some forum readers/members are interested in unmanned space flight...

Alain, VTM TV was right about the passing into the gap between the rings, but it might be something to do in the 'extended' part of the mission, the speed they mentioned was their own version of 50000 mph. The Voyager spacecraft didn't pass into the rings back in the early 1980s... amazing JPL considers Cassini-Huygens to do so or dive into Saturn as Galileo did into Jupiter!

Yes, it's also amazing what an accurate navigation was required after the Vega orbit on to Jupiter and then aiming right into the rings. Cassini-Huygens is spin-stabilised (remember, "Spinners live forever").

Philip
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posted 07-07-2004 12:43 PM     Click Here to See the Profile for Philip   Click Here to Email Philip     Edit/Delete Message   Reply w/Quote
Cassini-Huygens was looking at Titan's atmosphere and could glimpse through a hole in the clouds completely down to the surface!

spaceuk
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posted 07-17-2004 08:01 AM     Click Here to See the Profile for spaceuk     Edit/Delete Message   Reply w/Quote
Some interesting raw images on the Cassini JPL site.

The 'ropey/braided' looking F ring is of interest and a further couple intriguing shots of Titan.

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posted 07-21-2004 09:18 PM     Click Here to See the Profile for Columbiad1   Click Here to Email Columbiad1     Edit/Delete Message   Reply w/Quote
December 24, 2004 will mark the day in history being the 1st time that a deep space probe will land on a moon of one of the outer planets, Titan to be exact! Cassini will release the Huygens Probe into Titan's atmosphere on Dec. 24, 2004. My question is does the Huygens Probe contain any cameras for photos of the surface of Titan, like the Viking photos of Mars? Does anyone think we will see or find liquid pools of methane or frozen lakes of methane? So far we have photos of the surface of Earth, the Moon, Mars, and Venus... will Titan be next? Does anyone know about the Pluto Express mission any information will help? Thanks.

spaceuk
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posted 07-22-2004 07:03 AM     Click Here to See the Profile for spaceuk     Edit/Delete Message   Reply w/Quote
Huygens is only released from Cassini on 24th December 2004. It will take 21 days to coast and then descend to surface of Titan.

I expect Titan surface to look a lot like Venus surface and the plate-like layers we are seeing around Endurance crater at Mars.

Definitely craters (we have hints in images already) and possibly even volcanoes. Lakes of methane? I don't think so.

Scott
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posted 07-22-2004 09:07 AM     Click Here to See the Profile for Scott   Click Here to Email Scott     Edit/Delete Message   Reply w/Quote
Yes I am really looking forward to this. Can't wait.

DC Giants
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posted 07-22-2004 09:38 PM     Click Here to See the Profile for DC Giants   Click Here to Email DC Giants     Edit/Delete Message   Reply w/Quote
I wondered the same thing - whether the probe carried any cameras. A while back I was browsing the Cassini homepage and recall seeing something about an imager on the probe. We can only hope!

spaceuk
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posted 07-25-2004 11:13 AM     Click Here to See the Profile for spaceuk     Edit/Delete Message   Reply w/Quote
The Huygens Descent Imager and Spectral Radiometer (DSIR) is used during the latter part of the descent. It has two imagers - one visible and one infrared. It has side looking visible imager to capture horizon views and views of the underneath of Titan's cloud deck. On its descent, as it 'spins around' on its parachute system, it should be possible to build up a panorama of Titan.

If Huygens lands successfully on either a liquid, slushy or hard surface the imagers should continue to operate for anywhere from 3 to 30 minutes. Greatest success for landed operations would be on a liquid surface. A hard surface and impact may force the lower deck science packages upwards through a honeycomb material that separates them from the upper deck equipment.

I understand imager transfer rate is about 500 bps at the 10 kilometre altitude but increases to 1000 bps at one kilometre altitude.

Spectral transfer rate is 200 bps throughout.

Other equipment aboard includes:

  • HASI - Huygens Atmospheric Structure Instrument
  • DWE - Doppler Wind Experiment
  • GCMS - Gas Chromatograph Mass Spectrometer
  • ACP - Aerosol Collector and Pyrolyser
  • SSP - Surface Science Package
The descent is very steep up to parachute deployment and very little accurate knowledge exists about parachute descents in such a 'hostile atmosphere' like that which will be encountered at Titan. Most data was mainly gleaned from the Viking and Apollo experiences prior to Huygens being built.

So, I'm pretty sure it will be 'nail-biting' stuff as Huygens begins its descent through Titan's atmosphere.

Blackarrow
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posted 07-25-2004 03:27 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
How many images might reasonably be transmitted to Cassini from Huygens during the descent? I'm guessing, but surely a typical Cassini image has around a million "bits". Even at 1,000 bits per second, that would take 16 minutes to transmit one complete image. Or will they use the Galileo trick of transmitting only the difference between consecutive grey-scale values to compress the data?

spaceuk
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posted 07-26-2004 12:32 PM     Click Here to See the Profile for spaceuk     Edit/Delete Message   Reply w/Quote
I think we have to remember that this descent is a 'long descent' - of order of 3 hours.

The 10 km altitude is about 45 minutes from 'touchdown' with 1 km altitude about 5 minutes to touchdown from pre-mision charts I've seen.

The Descent Imager is switched on at about the 10 km altitude mark at about 45 minutes to go to touchdown.At that stage (with other data streams from other experiments) the composite bit rate is around 2.77 M bits. Prior to the DI being switched on the composite data rate was 0.96 M bits - so obviously a 'big increase'.

At the 1 km altitude (reading here from a chart) the Descent Images switch to hi bit rate and the composite bit rate is then 1 M bits. (I assume some science data switched off or not collecting to account for the fall in this? It doesn't elucidate in the tech paper on this.)

Post landing transmission falls to 0.5 M bits - assuming Huygens survives and can transmit for the full 30 minutes. I understand this 30 minute surface transmission is the maximum since the Cassini antenna will be targeted away from Titan after that time expires.

I don't know (yet) how many bits constitute a Huygen's DI image.

spaceuk
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posted 07-26-2004 12:56 PM     Click Here to See the Profile for spaceuk     Edit/Delete Message   Reply w/Quote
Found it! (Doesn't exactly jump-out at you on the sites though!)
  • High Resolution Imager (HRI): 160x256 pixels
  • Medium Resolution Imager (MRI): 176x256
  • Side Looking Imager (SLI): 128x256
Not 'large' images. But, hey, who cares as long as it works and we get the image/s.

spaceuk
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posted 07-27-2004 04:03 PM     Click Here to See the Profile for spaceuk     Edit/Delete Message   Reply w/Quote
Couple of interesting Saturn images amongst latest batch of 500 raw images.

One shows bright spots near the polar region. Another a bright area near the limb near terminator line - may be sunlight reflection? Another shows some layers in atmosphere. Another with a 'bright' moon in same image as partial Saturn.

spaceuk
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posted 10-09-2004 04:22 PM     Click Here to See the Profile for spaceuk     Edit/Delete Message   Reply w/Quote
Although excited to see images online from Cassini, I find those released so far (both raw and press images) fairly 'dismal'.

To my 'eyes' they appear not much better than Pioneer. The Voyager images seemed to have better 'visual quality'.

Some of the recent press images released of some of the moon's are not good images at all - nothing more than bright globes in the heavens.

Have they got a problem with the cameras or imaging mechanism? Not read anything - except that was some minor damage when passed through rings on entry into orbit around Saturn.

The non imaging science instruments though are making up with some excellent early results coming through.

Still an exciting event and maybe images will improve in future months with post processing?

Rodina
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posted 10-09-2004 11:02 PM     Click Here to See the Profile for Rodina     Edit/Delete Message   Reply w/Quote
Most of these images have been taken way away -- from six or eight million kilometers out. For the last month or two, they've just been shooting pictures because they can -- hell, they are there so why not? -- not because they're all that good.

The stuff from Saturn just before and after the burn is hundreds of times better than even Voyager. Patience, my friend.

spaceuk
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posted 10-25-2004 12:47 PM     Click Here to See the Profile for spaceuk     Edit/Delete Message   Reply w/Quote
All the best to the teams working on Cassini-Huygens flyby of Titan tomorrow.

Eagerly await the close-up images of Titan - especially the hi-res images of Huygens intended target site.

spaceuk
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posted 10-27-2004 07:44 AM     Click Here to See the Profile for spaceuk     Edit/Delete Message   Reply w/Quote
Cassini came through with flying colours last night. Congratulations to the teams involved.

The images released this morning are good.

Still difficult to 'determine' the surface but (leaving aside image blotches that appear) there seems to be craters and volcanoes down there. And what looks like deposits on certain 'down-wind' sides of these 'volcanoes'.

Wouldn't be surprised if it doesn't turn out to be a more dormant variety of Io?

Come on Huygen's - you can do it - in a few weeks and lift the veil once and for all.

mensax
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posted 10-27-2004 08:10 AM     Click Here to See the Profile for mensax   Click Here to Email mensax     Edit/Delete Message   Reply w/Quote
NASA: Titan's First Close-Up

spaceuk
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posted 11-24-2004 06:53 AM     Click Here to See the Profile for spaceuk     Edit/Delete Message   Reply w/Quote
PIA06141: If you have not seen this image of Titan, this Cassini mosaic is the best so far and shows the 'surface' fairly clearly.

A good fore-taste for Huygens.

Philip
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posted 11-24-2004 02:04 PM     Click Here to See the Profile for Philip   Click Here to Email Philip     Edit/Delete Message   Reply w/Quote
An amazing image of Titan, that Saturnian moon!


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