Volume of space to be sampled

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Martino
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Volume of space to be sampled

Post by Martino »

I did some quick calculations with the following assumptions;
1) Stardust traveled a total of 282 million km at about 18 km / sec relative to the sun with the dust collector open
2) There's a total of .1 sq meter of aerogel surface, 132 cells, and 1.6 million non-overlapping focus movies.
3) Interstellar particles were not moving relative to the sun (known to be false!)

This suggests:

The collector swept out a volume of space approximately 28.2 cubic km.
Each cell represents about .2 cubic km.
Each focus movie samples a relatively modest 18,000 cubic meters, about the size of a good sized building. This will be more if the focus movies overlap.

According to the Stardust website, the collector was exposed when the spacecraft was going in the same direction as the interstellar particles, and considerably slower than them -- they were catching up to the spacecraft with a relative velocity of about 8 km per second. Therefore the volumes of the interstellar medium sampled will be less than half those I came up with above.

Martino
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Volume of space

Post by Martino »

Thanks for the comments.

I was looking for a ballpark number to have in my head when viewing a movie. The volume per movie will be about twice what I said if you are right about the larger field of view.

My information source for the velocity of interstellar dust was the URL http://www.lpi.usra.edu/meetings/dust2005/pdf/4023.pdf

They say "In Fig. 1 (b), direction oftwo dust particles (b, e) corresponds to that of typical interstellar particles, which should correspond to the direction of the solar system moving against the surrounding interstellar gas cloud with a relative velocity 26km/s [4]. "

I estimated spacecraft velocity by measuring from the images at http://stardust.jpl.nasa.gov/mission/details.html , also the geometry relative to the sought-for particles. Not too precise(!) but then I was only trying to arrive at an order of magnitude.

dangermite
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Fermi Problem

Post by dangermite »

Hey Martino,

Sounds like a Fermi problem ("How many piano tuners are ther ein Chicago?", etc). Taking what you know and applying it logically to arrive at a solution = sign of a good physicist.

dm

danajohnson
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Post by danajohnson »

Any guesstimation, on the total for the return package? Many high altitude flights have attempted to collect Brown-lee particles. Should we be expecting a higher population of local system random items captured than the interstellar wind would bring from a greater distance? If any particles are present in the first 12-13 cells, we could make an extension of the successful finding.

Martino
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Post by Martino »

Not many. The detector on NOZOMI (see http://www.lpi.usra.edu/meetings/dust2005/pdf/4023.pdf) was active for a substantial time in roughly the same region of space, relative to the sun. It only encountered a few particles with velocities and directions expected for interstellar particles. I can't see any reason why this experiment would see substantially higher populations per unit volume, but we can always hope.

Wolter
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Post by Wolter »

Look here: http://stardust.jpl.nasa.gov/mission/details3.html for details on stardust collection.
And here http://stardust.jpl.nasa.gov/science/de ... l#scigoalsyou will find under 1.2 that the goal is to collect up to 100 IS particels.
Just dusting... Image

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