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Spirit color wheel not being used?



 
 
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  #1  
Old January 9th 04, 09:58 AM
Conan Ford
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Default Spirit color wheel not being used?

I wonder what the purpose of the color wheel is, when I see images like
this:

Go to http://photojournal.jpl.nasa.gov/cat...=pia05015click
on the high resolution version and then click on the Full-Res JPEG, (or
TIFF it you want). I've linked them below as well. Incidentally the
medium res version is missing part of the center of the picture.

medium res:
http://www.jpl.nasa.gov/mer2004/rove...2004/video.jpg
high res:
http://photojournal.jpl.nasa.gov/cat...umber=pia05015

the colors on the color wheel do not at all look like the color wheel
he
http://www.jpl.nasa.gov/mer2004/rove...s/image-2.html

Specifically, there is no green or blue visible on the color wheel in
the mars images, unlike the images on the page showing the color wheel
alone. In addition, the blue has been changed to a brilliant red. I'm
wondering the point of a color wheel when it does not appear to be used
properly.
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  #2  
Old January 12th 04, 04:32 AM
Andrew K.
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Default Spirit color wheel not being used?

Conan,

Assuming that you mean the 4 color blocks in the corners of the sundial, I
suspect the scientists and engineers are using, and will continue to use, this
information. The image you refer to has been released for public consumption
and is probably not being used by the scientists and engineers.

I don't know the details about the design of the PanCam, but most color imagers
used on spacecraft are actually black & white (i.e. a single ccd). Color
images are created by using a "filter wheel" inside the imager. As a result,
in order to get a full color image, three separate images are required.

As for the colors being different, I can think of several possibilities

1) If the PanCam is of the design I describe above and the software calibrated
to the "correct" colors as seen on Earth prior to launch, then this is how the
colors would appear to us (human beings). -- the most likely scenario, IMHO.

2) This is one of several images that are being used to determine how the
colors change as the sun moves and as the particulate levels change. We use a
similar technique here to determine the levels and types of pollution in the
air.

3) Properly calibrated, the image may have looked like places here (e.g., the
Painted Desert in the USA) rather than another planet, so the public affairs
office decided not to release such an image at this time.

4) Properly calibrated, the image may look like a computer generated picture
instead of a real one.

5) The data for one of colors at the location of the sundial was bad (CRC
mismatch on that particular packet).

I have several other possibilities in mind, but this is a start.

Andrew K.

Conan Ford wrote:
I wonder what the purpose of the color wheel is, when I see images like
this:

Go to http://photojournal.jpl.nasa.gov/cat...=pia05015click
on the high resolution version and then click on the Full-Res JPEG, (or
TIFF it you want). I've linked them below as well. Incidentally the
medium res version is missing part of the center of the picture.

medium res:
http://www.jpl.nasa.gov/mer2004/rove...2004/video.jpg
high res:
http://photojournal.jpl.nasa.gov/cat...umber=pia05015

the colors on the color wheel do not at all look like the color wheel
he
http://www.jpl.nasa.gov/mer2004/rove...s/image-2.html

Specifically, there is no green or blue visible on the color wheel in
the mars images, unlike the images on the page showing the color wheel
alone. In addition, the blue has been changed to a brilliant red. I'm
wondering the point of a color wheel when it does not appear to be used
properly.


  #3  
Old January 13th 04, 09:58 AM
Jouni Tulkki
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Posts: n/a
Default Spirit color wheel not being used?

Conan Ford wrote in message news:[email protected]
I wonder what the purpose of the color wheel is, when I see images like
this:

Go to http://photojournal.jpl.nasa.gov/cat...=pia05015click
on the high resolution version and then click on the Full-Res JPEG, (or
TIFF it you want). I've linked them below as well. Incidentally the
medium res version is missing part of the center of the picture.

medium res:
http://www.jpl.nasa.gov/mer2004/rove...2004/video.jpg
high res:
http://photojournal.jpl.nasa.gov/cat...umber=pia05015

the colors on the color wheel do not at all look like the color wheel
he
http://www.jpl.nasa.gov/mer2004/rove...s/image-2.html

Specifically, there is no green or blue visible on the color wheel in
the mars images, unlike the images on the page showing the color wheel
alone. In addition, the blue has been changed to a brilliant red. I'm
wondering the point of a color wheel when it does not appear to be used
properly.


This is because most images have been taken using L2 (infrared), L5
(green) & L6 (blue) filters. Using infrared filter makes a big
difference to the calibration colors, because of the paints that are
used. The difference between infrared and red in mars lanscape is much
smaller. In other words, even though the color wheel looks strange,
the landscape should have quite realistic colors.
  #4  
Old January 15th 04, 03:04 PM
Carlos Santillan
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Default Spirit color wheel not being used?

Conan Ford wrote in message news:[email protected]


This picture appeared on a UFOs article, surely out of context:


http://www.rense.com/general47/MarsB...PLJan10-04.jpg
  #5  
Old January 16th 04, 02:21 PM
b
external usenet poster
 
Posts: n/a
Default Spirit color wheel not being used?

The reason that the color wheel looks off is that pictures red component
was taken from the 750nm (near-IR) filter, instead of the red filter at
673nm. In near IR, the blue corner is extremely reflective and so looks
pink

Conan Ford wrote:
I wonder what the purpose of the color wheel is, when I see images like
this:

Go to http://photojournal.jpl.nasa.gov/cat...=pia05015click
on the high resolution version and then click on the Full-Res JPEG, (or
TIFF it you want). I've linked them below as well. Incidentally the
medium res version is missing part of the center of the picture.

medium res:
http://www.jpl.nasa.gov/mer2004/rove...2004/video.jpg
high res:
http://photojournal.jpl.nasa.gov/cat...umber=pia05015

the colors on the color wheel do not at all look like the color wheel he
http://www.jpl.nasa.gov/mer2004/rove...s/image-2.html


Specifically, there is no green or blue visible on the color wheel in
the mars images, unlike the images on the page showing the color wheel
alone. In addition, the blue has been changed to a brilliant red. I'm
wondering the point of a color wheel when it does not appear to be used
properly.

  #7  
Old January 17th 04, 03:19 PM
Pat Flannery
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Posts: n/a
Default Spirit color wheel not being used?



Carlos Santillan wrote:

This picture appeared on a UFOs article, surely out of context:


http://www.rense.com/general47/MarsB...PLJan10-04.jpg


YIKES! The guy on the right! MARTIAN ZOMBIE! RUN!

Pat

  #8  
Old January 21st 04, 11:10 PM
Joe Knapp
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Posts: n/a
Default Spirit color wheel not being used?


"b" wrote in message
...
The reason that the color wheel looks off is that pictures red component
was taken from the 750nm (near-IR) filter, instead of the red filter at
673nm. In near IR, the blue corner is extremely reflective and so looks
pink


If people really wantg to try their own color balance, one could get the raw
images from, for example:

http://marsrovers.jpl.nasa.gov/galle...irit_p002.html

There is in that collection a series of shots of the color wheel, with file
names:

http://marsrovers.jpl.nasa.gov/galle...0P2100L2M1.JPG
http://marsrovers.jpl.nasa.gov/galle...0P2100L5M1.JPG
http://marsrovers.jpl.nasa.gov/galle...0P2100L6M1.JPG

That is a series of three shots, from MER 1 (M1), left camera (L), filters
L2, L5 and L6 which is roughly red, green, blue.

According to the pancam technical document at
http://athena.cornell.edu/pdf/tb_pancam.pdf the filters' central wavelengths
and bandpasses are as follows (nanometers):

LEFT CAMERA/ RIGHT CAMERA


L1. EMPTY R1. 430 (SP) *

L2. 750 (20) R2. 750 (20)

L3. 670 (20) R3. 800 (20)

L4. 600 (20) R4. 860 (25)

L5. 530 (20) R5. 900 (25)

L6. 480 (25) R6. 930 (30)

L7. 430 (SP)* R7. 980 (LP)*

L8. 440 Solar ND R8. 880 Solar ND


*SP indicates short-pass filter; LP indicates long-pass filter

http://eosweb.larc.nasa.gov/EDDOCS/W...or_Colors.html

  #9  
Old January 23rd 04, 02:51 PM
Beau Webber
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Posts: n/a
Default Spirit color wheel not being used?

"Joe Knapp" wrote in message igy.com...
"b" wrote in message
...
The reason that the color wheel looks off is that pictures red component
was taken from the 750nm (near-IR) filter, instead of the red filter at
673nm. In near IR, the blue corner is extremely reflective and so looks
pink


According to the pancam technical document at
http://athena.cornell.edu/pdf/tb_pancam.pdf the filters' central wavelengths
and bandpasses are as follows (nanometers):

LEFT CAMERA/ RIGHT CAMERA


L1. EMPTY R1. 430 (SP) *
L2. 750 (20) R2. 750 (20)
L3. 670 (20) R3. 800 (20)
L4. 600 (20) R4. 860 (25)
L5. 530 (20) R5. 900 (25)
L6. 480 (25) R6. 930 (30)
L7. 430 (SP)* R7. 980 (LP)*
L8. 440 Solar ND R8. 880 Solar ND


*SP indicates short-pass filter; LP indicates long-pass filter

http://eosweb.larc.nasa.gov/EDDOCS/W...or_Colors.html


Here to hoping Spirit recovers from its transmission problems -

It has been worying me for some time that there appear to be
no identical red/green/blue filters for the left and right cameras -
how does one get full colour stereo pictures - perhaps interpolation
or perhaps it is approximate ?

anyone know ?
  #10  
Old January 23rd 04, 06:32 PM
mlm
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Posts: n/a
Default JPL Mars Image names (was Spirit color wheel not being used?)

"Joe Knapp" wrote in
gy.com:

....

There is in that collection a series of shots of the color wheel, with
file names:

http://marsrovers.jpl.nasa.gov/galle...53017ESF0200P2
100L2M1.JPG


....
That is a series of three shots, from MER 1 (M1), left camera (L),
filters L2, L5 and L6 which is roughly red, green, blue.


Can anyone shed light on the naming system JPL uses for their raw image
filenames? This is what I have figured out on my own:

Eg: 2 P 126553081 ESF 0200 P 2100 L6 M1 .JPG

2 = MER-2 (Spirit aka MER-A)

P = Pancam

9-digit decimal number = seconds since Jan 1, 2000
so: '126553081' would be 4-Jan-04 17:36. (4 hours slow though ??)

ESF/EFF/EDS = ? -- I note EFF is the predominant type; files are larger

4-digit decimal number = ? ('0200' in this case)

P = ?

4-digit decimal number = ? ('2100' in this case)

L = Left 'eye'
6 = Filter number 6

M1 = ? (I don't think Mer-1, as that is Opportunity)

Thanks for any insight.

Mark

PS Thanks v. much Joe for filter information.
 




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