Gel orientation in the movies, etc.

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glstah
Posts: 2
Joined: Sun Sep 17, 2006 1:05 pm

Gel orientation in the movies, etc.

Post by glstah »

After doing this for about 6 weeks, (I never got an email, even though I registered) I've got some questions about what we are looking at, and how we're looking at it. I've read the aerogel articles on the stardust site.

1. Is the illuminiation used in the VM movies reflected or transmitted? (Polarized?) My guess is that it is reflected based on the number of 'bright' particles that are occasionally seen.

2. What is the thickness of the gel when it was in the collector cells before launch; did it change when the capsule was recovered and the collector examined?

3. The FM have a width of about 1/2 mm (500 µM). What is the depth of each focal plane as the movies are made?

4. What is the expected penetration depth for the particles the collector was expected to capture? I know this will vary with the mass, velocity and shape of the particles; but some range must have been in mind.

5. Are we looking at the gel from the 'top' (the side facing the comet) or the 'bottom'? Why?

6. Based on the few sample pictures of particles and associated tracks in aerogel on the Stardust site, it looks like the tracks narrow down from where impact was to where the particle stops; but the CMs don't show anything like this. Suddenly, there is a circle that comes into focus at the bottom of the focus range, not a continuum of concentric circles that I would expect. Or have I totally missed the concept?

Thanks for making this discovery process open to the public !

Mighty Pete
Posts: 146
Joined: Thu Aug 10, 2006 7:47 am
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Post by Mighty Pete »

All these answers are already here but spread over lots of different threads. I'll answer them here again just for you. look inside the quote for the answers.
1. Is the illumination used in the VM movies reflected or transmitted? (Polarized?) My guess is that it is reflected based on the number of 'bright' particles that are occasionally seen.
It's back illuminated, It's sitting on a mirror.
2. What is the thickness of the gel when it was in the collector cells before launch; did it change when the capsule was recovered and the collector examined?
It's one cm thick
3. The FM have a width of about 1/2 mm (500 µM). What is the depth of each focal plane as the movies are made?
It's suppose to be no more and no less 100 um into the gel.
Obviously that is not the case on some movies.
4. What is the expected penetration depth for the particles the collector was expected to capture? I know this will vary with the mass, velocity and shape of the particles; but some range must have been in mind.
It should be visible at 100 um, the dust will have stopped deeper.
5. Are we looking at the gel from the 'top' (the side facing the comet) or the 'bottom'? Why?
Top other side of the IS collector. Yes there is two that where bolted together, they are now separate. We are looking at the 'B" side. The IS collector. Opposite side of the comet collector. The comet collector was the "A" side
6. Based on the few sample pictures of particles and associated tracks in aerogel on the Stardust site, it looks like the tracks narrow down from where impact was to where the particle stops; but the CMs don't show anything like this. Suddenly, there is a circle that comes into focus at the bottom of the focus range, not a continuum of concentric circles that I would expect. Or have I totally missed the concept?
There are pictures here available of the impacts from a side view. You should find those. It's a carrot shaped hole as viewed from the side. They're posted on this forum somewhere.

There is some pictures on this thread of the comet "A" side of impacts:

http://stardustathome.ssl.berkeley.edu/ ... php?t=1039

jsmaje
Posts: 616
Joined: Tue Aug 15, 2006 8:39 am
Location: Manchester UK

Re: Gel orientation in the movies, etc.

Post by jsmaje »

glstah wrote: 1. Is the illuminiation used in the VM movies reflected or transmitted? (Polarized?) My guess is that it is reflected based on the number of 'bright' particles that are occasionally seen.
Mighty Pete is right that they do use a mirror, but read http://stardustathome.ssl.berkeley.edu/ ... .php?t=131 in which Anna Butterworth explains a bit further:
We imaged the Mir and lab aerogel in our lab in Berkeley with all the tricks we've learned in imaging aerogel: reflected light, side lighting and a mirror underneath gives the best possible contrast.

The interstellar collector tiles are all still in the collector (we're not allowed to reach over the tiles, let alone remove them!) so we can't use side lighting. The edges have an aluminum foil rim at the back, but we do use a mirror underneath the central part of the tile which has no backing - this significantly brightens up the aerogel.
We are constantly trying to improve the quality of the movies.

glstah
Posts: 2
Joined: Sun Sep 17, 2006 1:05 pm

Thanks for the Answers!

Post by glstah »

jsmaje and 'mighty pete'

THanks for your answers you gave to my questions. I couldn't find this kind of background you so speedily provided.

I've seen the 'carrot' shaped deformations and that's what prompted some of the questions.

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