very small tracks

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Chuck Crisler
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Joined: Wed Aug 02, 2006 9:44 am
Location: Windham, NH

very small tracks

Post by Chuck Crisler »

In the recent article about this project, it was stated that 75% of 'dusters' find the smallest tracks, meaning that we are 7x as efficient as needed. That is the wrong word. Efficiency would be movies per hour. We are 7x as effective as needed, and I am very proud of it.

However, I have been thinking about the calibration movies. They are very effective to train us for what to look for. I assume that some of the more interesting results you have seen have been used to create more realistic calibration movies. I think that there may be one tiny problem. All of the calibration movies that depict a track show focus all the way down to the minimum focus. Is it possible for a low energy particle to create a shallow track that doesn't go very far down, so that at minimum focus height it is out of focus? Is it possible that it could appear as a small inclusion right under the surface? For that matter, could a larger particle with low energy also do that?

the moon
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Post by the moon »

I disagree that the calibration movies are an effective way to train us. They're all the same track, resized and rotated and put into different empty movies. They make people think that all tracks will look exactly like that. We need more examples of what real tracks would look like in these movies.

But on to your question. The team seems pretty sure that interstellar particles will hit fast enough to go deeper then the lowest focus. However, other stuff from unknown sources can hit at much lower speeds. They can make shallow tracks like you see in the low angle track topic.
http://stardustathome.ssl.berkeley.edu/ ... php?t=1458

fjgiie
DustMod
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I don't know...

Post by fjgiie »

Chuck Crisler wrote:Is it possible for a low energy particle to create a shallow track that doesn't go very far down, so that at minimum focus height it is out of focus?
The whole IS dust stream is moving at 30km/s relative, toward our solar system. The spacecraft was running away from the stream so as to slow down the relative impact speed and also to keep the collector away from solar particles. The IS particles should have impacted the aerogel at a speed of somewhere between 16km/s and less than 25km/s.

http://stardust.jpl.nasa.gov/mission/details3.html

We only look down into the aerogel at most 2% of the one centimeter thickness with the focus movies. (200microns/1 cm)
0.000200m times 39.37 inches/meter = 0.008 inches, the thickness of a good quality of computer printer paper. It would take a very small speck of fluffy dust moving at 20 km/s not to go deeper than that into the lightest aerogel made, would it not? Aerogel = solid smoke)

[edit]From this pdf paper it seems the impact speed could have been between 9.323 km/s and 14.946 km/s. That is still 10 to 16 times the speed of a 3000 feet per second rifle bullet.[/edit fjgiie]
Last edited by fjgiie on Sat Apr 14, 2007 6:21 am, edited 1 time in total.

DustSabre
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Joined: Sat Dec 09, 2006 4:51 pm

Post by DustSabre »

I disagree that the calibration movies are an effective way to train us.
For the most part, I certainly agree. While they are a basic way of training, you still have to scan about 300 real images before you are really going to have much experience.

Chuck Crisler
Posts: 30
Joined: Wed Aug 02, 2006 9:44 am
Location: Windham, NH

Post by Chuck Crisler »

However, as they say, this is research and we should 'expect the unexpected'. If 'they' knew everything, then this wouldn't be research.

Chuck Crisler
Posts: 30
Joined: Wed Aug 02, 2006 9:44 am
Location: Windham, NH

Post by Chuck Crisler »

We only look down into the aerogel at most 2% of the one centimeter thickness with the focus movies. (200microns/1 cm)
0.000200m times 39.37 inches/meter = 0.008 inches, the thickness of a good quality of computer printer paper. It would take a very small speck of fluffy dust moving at 20 km/s not to go deeper than that into the lightest aerogel made, would it not? Aerogel = solid smoke)
So, does this mean that if a focus movie is below the surface with the highest image that we would still likely see a track if one was present? I have been marking those as 'bad focus'.

fjgiie
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Post by fjgiie »

How deep does a track go? Can we still see it in the virtual microscope if we look down to a depth of 100 µm, micrometers or microns?

The PowerPoint slide show mentions a typical grain is 0.1 microns and a later slide mentions that the grain may penetrate 100 microns into the aerogel.

This pdf file mentions that the focus movies are a stack of 43 images spanning roughly 200 μm in focus depth.
We dusters know that a good movie will reach the surface at about one half of the focus bars. So most of the time we will be fortunate if we can see down into the aerogel 100 microns.
So, does this mean that if a focus movie is below the surface with the highest image that we would still likely see a track if one was present? I have been marking those as 'bad focus'.
If you can tell that you are just below the surface at top focus, then you can make a judgment on that movie, at least that is what I do.
If the focus goes down below 100 μm, then you may be looking below the track made by these grains that only go 100 μm into the aerogel. I cannot say that I have run into that situation before. Usually I am wishing that the focus movie had deeper focus.

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