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"wave" distortion patterns in Cassini ring images



 
 
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  #1  
Old July 2nd 04, 04:59 PM
Mike Flugennock
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Default "wave" distortion patterns in Cassini ring images


I'm sure there's probably some kind of simple, elegant explanation for the
wavelike banding distortion in Cassini's initial ring images, such as the
one at
http://saturn.jpl.nasa.gov/cgi-bin/g...jpg&type=image,
containing http://saturn.jpl.nasa.gov/multimedi...mages/SOI1.jpg .

I'm sure the answer probably involves rapid, periodic occultation of the
signal by chunks of ring material at such close range. I recall seeing one
image where the wave banding almost matches the dispersal patterns in the
rings.

I've also noticed a lot of "grain" in the close-up ring images; am I right
assuming this is due to having a camera close enough to begin resolving
individual chunks of "ring stuff"? (****, that thing's got real
_texture_!)

And damn, but I hope there were able to get some composite color of that
section. Still, they already got the cake, huh? (%^

Congrats again, JPL!

--
"All over, people changing their votes,
along with their overcoats;
if Adolf Hitler flew in today,
they'd send a limousine anyway!" --the clash.
__________________________________________________ _________________
Mike Flugennock, flugennock at sinkers dot org
Mike Flugennock's Mikey'zine, dubya dubya dubya dot sinkers dot org
  #2  
Old July 2nd 04, 06:20 PM
Pat Flannery
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Default



Mike Flugennock wrote:

I'm sure there's probably some kind of simple, elegant explanation for the
wavelike banding distortion in Cassini's initial ring images, such as the
one at
http://saturn.jpl.nasa.gov/cgi-bin/g...jpg&type=image,
containing http://saturn.jpl.nasa.gov/multimedi...mages/SOI1.jpg .

I'm sure the answer probably involves rapid, periodic occultation of the
signal by chunks of ring material at such close range. I recall seeing one
image where the wave banding almost matches the dispersal patterns in the
rings.


Actually, that is what the rings really look like at close range- there
is a explanation of what causes the "waves" he
http://spaceflightnow.com/cassini/040701science.html
There are also spiral rings! This is one cool looking planet.

Pat

  #3  
Old July 2nd 04, 07:59 PM
Bruce Palmer
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Default

Mike Flugennock wrote:
I'm sure there's probably some kind of simple, elegant explanation for the
wavelike banding distortion in Cassini's initial ring images, such as the
one at
http://saturn.jpl.nasa.gov/cgi-bin/g...jpg&type=image,
containing http://saturn.jpl.nasa.gov/multimedi...mages/SOI1.jpg .

I'm sure the answer probably involves rapid, periodic occultation of the
signal by chunks of ring material at such close range. I recall seeing one
image where the wave banding almost matches the dispersal patterns in the
rings.

I've also noticed a lot of "grain" in the close-up ring images; am I right
assuming this is due to having a camera close enough to begin resolving
individual chunks of "ring stuff"? (****, that thing's got real
_texture_!)

And damn, but I hope there were able to get some composite color of that
section. Still, they already got the cake, huh? (%^

Congrats again, JPL!



Black and white only I'm afraid. It was going too fast to take separate
RGB frames. A shame, too. When the Mariner Mark II was first designed
it was to have had multiple, independently targettable scan platforms,
but budget cutbacks did away with those. On the plus side, the mission
cost "only" $3.3 billion and likely would have been much more if the
original design had prevailed. Fewer moving parts also lead to a more
reliable spacecraft.

--
bp
Proud Member of the Human O-Ring Society Since 2003
  #4  
Old July 3rd 04, 06:55 AM
David M. Palmer
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Default

In article , Pat Flannery
wrote:

Mike Flugennock wrote:

I'm sure there's probably some kind of simple, elegant explanation for the
wavelike banding distortion in Cassini's initial ring images, such as the
one at


http://saturn.jpl.nasa.gov/cgi-bin/g...images/rings/i

mages/SOI1.jpg&type=image,
containing
http://saturn.jpl.nasa.gov/multimedi...mages/SOI1.jpg .

I'm sure the answer probably involves rapid, periodic occultation of the
signal by chunks of ring material at such close range. I recall seeing one
image where the wave banding almost matches the dispersal patterns in the
rings.


Actually, that is what the rings really look like at close range- there
is a explanation of what causes the "waves" he
http://spaceflightnow.com/cassini/040701science.html
There are also spiral rings! This is one cool looking planet.


The original poster was asking about something else: groups of scan
lines that are brighter and darker, giving the image a corrugated
appearance. You can tell that they are artifacts by the fact that they
are aligned with the image raster, and you can see the actual structure
of the rings underneath at an angle that follows the rings.

Also there are some of the same pictures 'after post-processing' that
don't show the banding. (Post-processing is not just to remove the
face sculptures and ring-cities from the images.)

I would guess that there's some sort of oscillation in the readout of
the CCD.

--
David M. Palmer (formerly @clark.net, @ematic.com)
  #5  
Old July 3rd 04, 07:12 AM
OM
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On Fri, 02 Jul 2004 23:55:49 -0600, "David M. Palmer"
wrote:

Also there are some of the same pictures 'after post-processing' that
don't show the banding. (Post-processing is not just to remove the
face sculptures and ring-cities from the images.)

I would guess that there's some sort of oscillation in the readout of
the CCD.


....This is the same banding I talked about last night. There's
*something* being introduced in the data pre-processing that's causing
these bands, because they look basically the same from picture to
picture. Not sure if it's the CCD, or if there's something actually
introducing the digital equivalent to TVI, but it *is* an annoying
side to some otherwise spectacular pics.

Alex? Any comments from your friends at JPL on what's up with this?

OM

--

"No ******* ever won a war by dying for | http://www.io.com/~o_m
his country. He won it by making the other | Sergeant-At-Arms
poor dumb ******* die for his country." | Human O-Ring Society

- General George S. Patton, Jr
  #6  
Old July 3rd 04, 07:21 AM
Alex R. Blackwell
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OM wrote:

Alex? Any comments from your friends at JPL on what's up with this?


I'm not sure what you are referring to. However, I understand there's a
2 Hz signal in some of the ISS raw data but these are being deconvolved
in the processed imagery. Typically, "banding" in raw imagery is due to
some hardware problem such as stray light (i.e., a "light leak" of the
type in the Mars Odyssey THEMIS system), though I haven't heard of that
problem with ISS.

--


Alex R. Blackwell
University of Hawaii

  #7  
Old July 3rd 04, 08:53 AM
Revision
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Default

Mike Flugennock wrote:
And damn, but I hope there were able to get
some composite color of that
section. Still, they already got the cake, huh?


Black and white only I'm afraid. It was going too fast to take separate
RGB frames. A shame, too. When the Mariner Mark II was first designed
it was to have had multiple, independently targettable scan platforms,
but budget cutbacks did away with those. On the plus side, the mission
cost "only" $3.3 billion and likely would have been much more if the
original design had prevailed. Fewer moving parts also lead to a more
reliable spacecraft.

--
bp
Proud O-Ring


  #8  
Old July 3rd 04, 09:14 AM
OM
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Default

On Fri, 02 Jul 2004 20:21:34 -1000, "Alex R. Blackwell"
wrote:

I understand there's a 2 Hz signal in some of the ISS raw data but these are being deconvolved
in the processed imagery.


....If I understand the imaging system, that would be just about right
to produce the TVI. Any clue as to what's producing the 2Hz
interference, or was this expected all along?

OM

--

"No ******* ever won a war by dying for | http://www.io.com/~o_m
his country. He won it by making the other | Sergeant-At-Arms
poor dumb ******* die for his country." | Human O-Ring Society

- General George S. Patton, Jr
  #9  
Old July 3rd 04, 10:02 AM
Henry Spencer
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In article ,
Revision wrote:
...When the Mariner Mark II was first designed
it was to have had multiple, independently targettable scan platforms,
but budget cutbacks did away with those...


If (dim) memory serves, by the time Cassini got to detailed design, there
was only one scan platform with precision pointing, although there was a
second low-precision one. That and some other things vanished in the big
cost-reduction scrub.

On the plus side, the mission
cost "only" $3.3 billion and likely would have been much more if the
original design had prevailed...


Moreover, it only barely survived as it was -- it would probably be dead
and largely forgotten, like its brother CRAF, had not the Huygens probe
represented a major international commitment that was difficult to cancel.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |
  #10  
Old July 3rd 04, 03:44 PM
Alex R. Blackwell
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Default

OM wrote:

...If I understand the imaging system, that would be just about right
to produce the TVI. Any clue as to what's producing the 2Hz
interference, or was this expected all along?


I haven't kept up too closely with this particular ISS issue, as opposed
to, say, the contamination problem during cruise phase, so I'm not sure
if it was unexpected or not. Fortunately, though, everyone I know who is
processing the imagery, including me, says removing the 2Hz noise is no
sweat.

--


Alex R. Blackwell
University of Hawaii

 




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