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RGClark
2005-Jan-07, 05:12 PM
I wanted the mini-TES spectrometer on the Spirit Mars rover to be able to determine the chemical makeup of smooth, dark inclusions seen here:

http://sciforums.com/attachment.php?attachmentid=3654

It's a closeup of a rock seen at the Spirit landing site:

A Rock Like None Before, Brushed.
"Scientists viewed a rock like none seen before on Mars when NASA's Mars Exploration Rover Spirit brushed the surface and took magnified images of this rock dubbed "Wishstone." The circular area of interest, measuring approximately 5 centimeters (2 inches) in diameter, revealed darker pieces of material randomly distributed within a lighter-colored matrix. The rock has poorly sorted granular material, with grain sizes ranging from fine to coarse and some grains that are very angular in shape. Spirit used its microscopic imager on martian day, or sol, 333
(Dec. 9, 2004) to take the four individual frames that are combined into this mosaic view."
http://marsrovers.jpl.nasa.gov/gallery/pre.../20041230a.html (http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20041230a.html)


Below I suggest holding a sample of these inclusions close to the mini-TES viewport so its resolution will be increased:

============================================
Newsgroups: sci.astro, alt.sci.planetary, sci.geo.geology, comp.robotics.misc
From: "Robert Clark" <rgregorycl...@yahoo.com>
Date: 5 Jan 2005 22:02:32 -0800
Local: Wed, Jan 5 2005 10:02 pm
Subject: Re: Smooth inclusions in Wishstone rock.
...
The mini-TES viewport is the same as the Pancam. According to this
page the Pancam is 1.3 meters above ground level and its resolution is
0.286 milliradians/pixel:

Pancams:
Panoramic Cameras aboard the Mars Exploration Rovers.
http://www.planetary.org/mars/mer-inst-pancam.html

That means it should be able to resolve something .286/1000 * 1.3 m =
.37 millimeters across.
The RATTed area in the image on this page is supposed to be 5 cm
across:

A Rock Like None Before, Brushed.
http://marsrovers.jpl.nasa.gov/gallery/pre.../20041230a.html (http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20041230a.html)

On my monitor when I click on the link for the Browse Image, the
magnified view of the RATTed area appears about 10 cm across on my
screen and I measure some of larger dark inclusions on my screen as 4
mm across. This means the actual size of the larger inclusions should
be about 2 millimeters across.
This should be well within the resolving power of the Pancam.
For the mini-TES though the resolving power is at best 8 milliradians,
which means at 1.3 m it can resolve 8/1000 * 1.3 m = 10.4 mm, too large
for the inclusions.
Is there any way for the RAT arm to scrape off a portion of a rock and
hold it close to the camera?


Bob Clark
============================================

However, I&#39;m informed that the mini-TES receives it images through a Cassegrain type telescope arrangement and can only focus down to 2 meters. So my question is: what happens when you hold something closer to the aperture than the focal length?
At 2 meters and 8 millirad resolution it can resolve objects 16 mm across. Say you have an object 2mm across and hold it 1/4 meter from the aperture. Would anything at all be observed by the imaging CCD?
I was assuming that something would be observed but it would appear fuzzy. But this is assuming an object larger than the resolution limit. I mean, like if you had a 16 mm across object and held it 1/4 m away the imaging system could resolve it but it would appear fuzzy. But this is something else when the case is of an object smaller than the resolution size at the focal length distance.
I want to be able to say that *something* will be observed by holding the smaller object sufficiently close to the aperture, even if it is fuzzy.
If so then there are various image processing techniques to clean up a blurred image so you might be able to get spectrographic information out of the blurred image.


Bob Clark

RGClark
2005-Jan-09, 02:59 PM
|
|<--------Plane at minimum focus distance to telescope.
|
|
&#092; |
&#092; |
&#092; | ________________________
&#092; | |
&#092; | |
&#092;| |
x | | <------Telescope aperture.
|&#092; |
| &#092; |
| &#092;|
| |
| /|
| / |
|/ |
x | |
/| |
/ | |________________________
/ | ^
/ | |
/ | |
/ | Region where image will not be in focus.
|
|



The resolution limit of the telescope is the vertical distance

between the x&#39;s in the diagram that lie at the minimum focus

distance. For larger distances away (towards the left), the

smallest size that can be resolved will be the distance between the

sides of the angle at that distance. Ok, so this is what I

want to be the case. Because then we can just move the small object

that normally couldn&#39;t be resolved by the telescope closer to the

aperture and an image albeit fuzzy will be produced. Then we&#39;ll use

image processing to clear up the blurred image.
However, looking at some sites on the net what I&#39;m wondering about

is that what actually happens is this:



|
|<--------Plane at minimum focus distance to telescope.
|
|
&#092; | ________________________
&#092; | |
&#092; | |
&#092; | /|
&#092; | / |
&#092;|/ |
x | | <------Telescope aperture.
| |
| |
| |
| |
| |
| |
| |
x | |
/|&#092; |
/ | &#092; |
/ | &#092;|
/ | |
/ | ^ |________________________
/ | |
| |
| Region where image will not be in focus.

That is, as you get closer to the aperture, within the minimum

focus distance, the smallest object that can be resolved actually

gets larger again. So in this case moving the small object closer

to the aperture won&#39;t help.


Bob Clark