Huygens' HASI instrument(s) ?

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Adirondack M
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Huygens' HASI instrument(s) ?

Post #1by Adirondack » 09.02.2005, 09:55

One question about Jestr's descending Huygens probe (heat shield is off):

There are three legged booms at the probe.
Are these booms the HASI instrument(s) or something else?
I'm not sure, because on schematic figures the
HASI booms seem smaller, shorter and thinner.

The booms are surely no landing legs.
What are they?

I already have asked Jestr, but he did not know more than me.

Adirondack
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Post #2by Cham » 24.08.2007, 06:26

I made an highly detailed model of the huygens probe, based on several pictures I've found on the net. Currently, the orientation isn't right, relative to the ground, so I still have some work to do on it :

Image

Image

I'm not sure I'll publish this model, since I made some mistakes while interpreting the pictures I used. It's now too late to correct the mesh. :oops:
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Post #3by ElChristou » 24.08.2007, 11:24

Cham wrote:I made an highly detailed model of the huygens probe, based on several pictures I've found on the net. Currently, the orientation isn't right, relative to the ground, so I still have some work to do on it :

NICE! 8O


Cham wrote:I'm not sure I'll publish this model, since I made some mistakes while interpreting the pictures I used. It's now too late to correct the mesh. :oops:


Why it can't be corrected? it's just a mesh! it would be a pity not releasing it... :?
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Post #4by Cham » 24.08.2007, 15:20

ElChristou wrote:Why it can't be corrected? it's just a mesh! it would be a pity not releasing it... :?


Well, there are several points which trouble me :

1- because of the kind of details, it needs hardware antialiasing (FSAA), or else it's ugly and not really worth it. On my system, it's very beautifull, however.

2- the model is pretty large : it's a 5.4 MB 3ds file and contains 260 kilo-triangles. That's because there are tons of small bolts, and all the pieces have bezels (it's very nice in Celestia with FSAA, the model looks like all metal).

3- I badly interpreted some of the pictures I used, so some pieces aren't placed at the exact proper location on the model. Correcting them will be too long to do and too messy. It's not worth it.

4- I don't want to add the parachute, cables, etc. It's too long to do and I don't feel it's really worth it.

Here are two more views of the model :

Image

Image
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Post #5by ElChristou » 24.08.2007, 16:59

Cham wrote:2- the model is pretty large : it's a 5.4 MB 3ds file and contains 260 kilo-triangles. That's because there are tons of small bolts, and all the pieces have bezels (it's very nice in Celestia with FSAA, the model looks like all metal)...


Yep, bolts quickly increase the poly level... (it's why I use in general a 6 sections bolts (16 poly by bolt, not really nice, but always for a question of FPS on my config...)
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Post #6by Cham » 24.08.2007, 17:41

Just for the comparison, here are two pictures of the real thing. The first picture was taken during testing phase (I suspect this is actually a test model of huygens, not the real one which is now on Titan), the second is during the mounting on Cassini :

Image

Image

Here's a shot of the original (old) model in Celestia :
Image
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Post #7by ElChristou » 24.08.2007, 17:54

Well, returning on Adirondack question, the old model shows 3 "landing gear" (or else) and yours 2 only...

Which is the right one? (I mean there is a big mistake here, touching a crucial conceptual point... :x) What are they in reality?

(BTW, an in-between (medres, but with all correct details) would be welcome! :wink:)
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Post #8by Cham » 24.08.2007, 17:59

According to ALL the pictures I've found, there are only TWO "legs". They aren't legs, actually, I don't know what are their purposes. The model with three "legs" is clearly inaccurate.

The details shown on top of the old model are related to some testing models and small scale presentation models I saw in pictures. It's not like that, on the real probe. The real probe has (unless I'm dead wrong) two black "antennas" on top (like what is shown on my model and on the second picture above).

Watch the top-left part of the second picture in my last message. You can see a part of the ring on one of the "legs". I think it's better to call them "arms", instead of "legs".
Last edited by Cham on 24.08.2007, 18:04, edited 1 time in total.
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Post #9by ElChristou » 24.08.2007, 18:04

Cham wrote:According to ALL the pictures I've found, there are only TWO "legs". They aren't legs, actually, I don't know what are their purposes. The model with three "legs" is clearly inaccurate.

The details shown on the old model are related to some testing models I saw in pictures. It's not like that on the real probe. The real probe has (unless I'm wrong) two black "antennas" on top (like what is shown on my model and on the second picture abbove).

Watch the top-left corner of the second picture in my last message. You can see a part of the ring on one of the "legs".


Yep, saw it... (the axis seems to be the same color than the body, not grey! :wink:)

Then what about a quick low res model to at least correct the "legs" problem?
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Post #10by Cham » 24.08.2007, 18:09

ElChristou wrote:to at least correct the "legs" problem?


what legs problem ?

The color isn't obvious. There are lots of "gold" reflections from the shield, on that picture. According to some other pictures I've found, it's metallic gray. The third "leg" on the old model probably comes from the small sensor extension, as seen on the picture (see also my model). Here's a close shot of the real sensor :

Image

This " third arm" is designed to measure temperature and pressure. The small part shown with the red circle is the microphone ! :D
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Post #11by Cham » 24.08.2007, 18:18

There's a large picture of a rough model of the huygens probe there :

http://en.wikipedia.org/wiki/Huygens_probe

This was probably used as a ESA presentation model. The main features are there.

The reasons why I'm hesitating to publish my model isn't really its size (5.4 MB 3ds file and 258372 triangles aren't THAT bad). It's just that I made several "minor" errors while interpretating the pictures of the real thing, and I also had to add a few fictious details on the model, to improve its look in Celestia. The main error (it's too late now) is about the four "pads" around the "belt". Their spacing isn't correct : I placed them at 90?° of each other (like on the old model), while they aren't that symetric on the real probe. Also, I'm a bit puzzled about the level of details. It's inconsistent in some ways. :oops:

At least, my model is showing all of the main features. And lets say it's just an exercice in modeling for Celestia. :?
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Post #12by ElChristou » 24.08.2007, 19:21

Cham wrote:
ElChristou wrote:to at least correct the "legs" problem?

what legs problem ?
On the old model.


Cham wrote:The reasons why I'm hesitating to publish my model isn't really its size (5.4 MB 3ds file and 258372 triangles aren't THAT bad).
Who says it was bad? :wink:


Cham wrote:It's just that I made several "minor" errors while interpretating the pictures of the real thing, and I also had to add a few fictious details on the model, to improve its look in Celestia.
? there wasn't enough stuff on the shots? 8O (do you mean in the parachute box?)


Cham wrote:The main error (it's too late now) is about the four "pads" around the "belt". Their spacing isn't correct : I placed them at 90?° of each other (like on the old model), while they aren't that symetric on the real probeD

?? what's the problem? they are independent mesh... or not? At best as they are similar, you remove 3 of them and duplicate the remaining one has necessary... :?
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Post #13by ElChristou » 24.08.2007, 19:29

BTW, for the 3rd arm, with such a nice doc, why reducing this nice sensor structure to a simple cylinder? (for someone who don't know the probe it will give a false impression, I mean with this doc you can give the right representation...)
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Post #14by Cham » 24.08.2007, 19:35

ElChristou wrote:? there was enough stuff on the shots? 8O (do you mean in the parachute box?)

Because all the stuff on the pictures are unclear.

The pictures I've found aren't clear enough for most details. There's a lot of confusion with too much details, cables, and stuff from the environment (lab, technicians, etc). And on many shots, the probe isn't actually the same ! There are several testing and construction phases, and they are even using several models (with different features), depending on the test experiment.

ElChristou wrote:?? what's the problem? they are independent mesh... or not? At best as they are similar, you remove 3 of them and duplicate the remaining one has necessary... :?


The problem is there is some strong correlations with those four pads and the details around the probe (example : the small "wings" under the main body are aligned with the pads, and also with many of the "blades" and bolts on the upper part of the main body). At first, I assumed a perfect 90?° symetry with the pads (it wasn't obvious on many of the pictures I had). Then, I discovered later that it isn't exactly the case on some very few pictures. The difference isn't that bad, so it's not worth rebuilding the whole model. I'll leave it to another player, if the model isn't satisfying to someone.

The parachute boxes (the small cylinder on top, and the large box) are empty (both parachutes are gone), on my model. The central cylinder was containing the first (small) parachute to slow down the probe at high altitude. The large box was holding the large parachute. See also the large picture (link above) on wikipedia, about the presentation (or museum ?) model.
Last edited by Cham on 24.08.2007, 19:48, edited 2 times in total.
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Post #15by Cham » 24.08.2007, 19:44

ElChristou wrote:BTW, for the 3rd arm, with such a nice doc, why reducing this nice sensor structure to a simple cylinder? (for someone who don't know the probe it will give a false impression, I mean with this doc you can give the right representation...)


Yes, I was thinking about that detail too. I hesitated a lot to built a precise model for this piece, but then it wouldn't be very consistent with the rest. I mean, why having a part with an extremely high level of small scale details, while the rest stay at a low level ? See again the wikipedia picture of that crude presentation model. This is one reason why I'm very hesitant to publish this model : I feel "insecure" with it.
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Post #16by Cham » 24.08.2007, 20:00

Here's another view of the model. This is most probably the final version :

Image
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Post #17by ElChristou » 24.08.2007, 20:09

Cham wrote:
ElChristou wrote:?? what's the problem? they are independent mesh... or not? At best as they are similar, you remove 3 of them and duplicate the remaining one has necessary... :?

The problem is there is some strong correlations with those four pads and the details around the probe (example : the small "wings" under the main body are aligned with the pads, and also with many of the "blades" and bolts on the upper part of the main body). At first, I assumed a perfect 90?° symetry with the pads (it wasn't obvious on many of the pictures I had). Then, I discovered later that it isn't exactly the case on some very few pictures. The difference isn't that bad, so it's not worth rebuilding the whole model. I'll leave it to another player, if the model isn't satisfying to someone.
Yep, but here to me it's not such a problem. What I'm used to do with models of real stuff is to represent the main features as accurate as possible in proportion and position. Then comes what I will call secondary features, that are less important because they don't have a crucial role; example in the case of the SaturnV 3rd stage, the structure of the skirt, or some lines of bolts on the CSM, even bolts on the LB7. Those details are important to give the right "feeling" but 300 bolts or 280, for what we do it's the same... you see what I mean?
In the case of your model, seems the top structure is not as complex as the real probe, it is much more based on the model shown in the Wiki. So is the position of those 4 pads really important vis a vis the details of the body? IMHO, I don't think.

Cham wrote:
ElChristou wrote:BTW, for the 3rd arm, with such a nice doc, why reducing this nice sensor structure to a simple cylinder? (for someone who don't know the probe it will give a false impression, I mean with this doc you can give the right representation...)


Yes, I was thinking about that detail too. I hesitated a lot to built a precise model for this piece, but then it wouldn't be very consistent with the rest. I mean, why having a part with an extremely high level of small scale details, while the rest stay at a low level ? This is one reason why I'm very hesitant to publish this model : I feel "insecure" with it.


Ok, but then there is other ways to simplify this structure keeping the "feeling" of a more complex and sensible structure. Tonight I'll show you what I'm thinking in (I'm at work, no modeler under the hand)...
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Post #18by Cham » 24.08.2007, 20:18

Many of the obscure details shown on top of the real thing are a mess of cables linked to the two parachutes (we can even feel their mechanism, on the pictures I gave on the first page).

The idea to add the main parachute is hurting my mind ! :?

Since we always have the problem of fluctuating ground and horizon in Celestia, when a model is dropped on the ground, it may be preferable to show the huygens probe at some low altitude, descending with its main parachute open. This will remove that mess of cables on top of the probe, so more consistency with my model. Adding a parachute with three cables will also add more polygons to the model :x

I like the idea to have a 3d snapshot of the huygens descent, in Celestia, permanently "frozen" in time.

Image


By the way, here's a test model (obviously) :

Image

Compare the top of this probe with that one (which I assume is the real one, which is on Titan right now, since we see the shielded protection capsule being applied here) :

Image

The first one has the typical details as seen on most renderings and simulations on the net. Including our old model for Celestia. The last picture has some very different details (see for example the two black "antennas").
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Post #19by ElChristou » 24.08.2007, 22:30

Back home...

Here is an example of what I was thinking to illustrate the complexity of the sensors of the 3rd arm (or leg):

Image

(Forget the rendering (no smoothed, bad colors), it's just for the idea...)

Previous photo as reminder:

Image
Image

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Post #20by Cham » 25.08.2007, 03:38

Okay, okay, here it is, microphone included ! :P

Image

and no, I wont put a texture on the etiquette. :wink:
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