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sts60
2004-Oct-28, 01:26 PM
I thought about putting this in the Face thread, but it seemed different enough to warrant its own.

Any idea what the little "bullseye" in the right-hand side of
this picture (http://www.esa.int/images/TitanFirstCloseUp_01_L.jpg) is? There seems to be a fainter "echo" of it at its 8:30 position too. If we put aside the probable explanations (Zetas, HAARP satellite mind-control facility, secret Nazi weapons-development outpost), I would guess image artifact(s); or could meteoroids thumping into a slushy surface make those marks? They're might regular.
http://www.esa.int/images/TitanFirstCloseUp_01_L.jpg

Add: there's a third faint bullseye above the other two, forming a more-or-less isoceles triangle. I didn't notice any others. Have to look at the higher-resolution images...

Ut
2004-Oct-28, 01:31 PM
Dust on the instruments.

sts60
2004-Oct-28, 01:47 PM
Indeed. A JPL page (http://www.nasa.gov/mission_pages/cassini/multimedia/pia06138.html) describes one such dot as "a camera artifact not removed by initial processing". Add in the fact that the same three dots appear in more than one image, and I'll buy that.

iFire
2004-Oct-28, 01:49 PM
Ut and sts60, you're just paid government disinfo agents trying to hide the secret Saturn moon bases! [-X

:P

But for real, I wondered what the heck they were when I first saw some of these pictures. I never thought of them as like some ultra-conspirancy, becuase I saw them in other pics as well, but they still looked freaking weird.

Argos
2004-Oct-28, 01:54 PM
Dust on the instruments.

Where that dust come from?

badprof
2004-Oct-28, 02:19 PM
Hi Argos,

There are plenty of possible sources. During manufacture, during transport, during preparations for launch, even interplanetary dust during flight.

Given the considerable amount of these dust specks I see on my CCD images despite all attempts to keep the optics dust-free, I would say that the engineers who built the camera system did a remarkable job keeping dust out!

Cheers,

Maurice

Ut
2004-Oct-28, 02:50 PM
It's government certified, conspiracy grade dust from the dust mines on Mars. Cassini picked it up at the dust processing plant on the far side of the Moon.

sts60
2004-Oct-28, 02:59 PM
The fact that I called them "bullseyes" in my OP and "dots" in my second post should tip you off that I'm a whistleblower trying to reveal it through the use of inconsistent terminology... what's that pounding on my door? What the...? Oh, no... ARRRGHHH.. <urk>....dkfdksflkddsafflkalka;fsa;dlslsad

Argos
2004-Oct-28, 03:04 PM
Hi Argos,

There are plenty of possible sources. During manufacture, during transport, during preparations for launch, even interplanetary dust during flight.

Given the considerable amount of these dust specks I see on my CCD images despite all attempts to keep the optics dust-free, I would say that the engineers who built the camera system did a remarkable job keeping dust out!

Cheers,

Maurice

So, in spite of all precautions, clean rooms, surgeon outfits, itīs possible to contaminate an alien environment.

tracer
2004-Oct-28, 03:21 PM
So, is this a regular visible-light photo of Titan's visible surface (i.e. the top of Titan's atmosphere), taken using one of Cassini's zoom-in close-up cameras -- or is this, say, some kind of radar or thermal image of the planet's solid surface?

Evan
2004-Oct-28, 03:34 PM
Dust. This is the vicinity of Saturn we are talking about. A place that contains trillions of tonnes of dust particles, aka rings. Not to mention that the solar system is a very dusty place. Just look in my garage.

sts60
2004-Oct-28, 05:33 PM
...So, in spite of all precautions, clean rooms, surgeon outfits, itīs possible to contaminate an alien environment.
There's more to it than that for spacecraft that go to places that might have aboriginal life - they are thoroughly sterilized. While no method is 100% foolproof, it's pretty good. See the relevant NASA page (http://planetaryprotection.nasa.gov/pp/index.htm).

NASA has a guy with the title of Planetary Protection Officer. He's the guy with the BFG strapped to his hip and the master key for the orbiting atomic laser cannons dangling from his neck. Well, OK, the reality isn't quite as cool.

mike alexander
2004-Oct-28, 08:29 PM
I think it's a radio button: Click Here for Black and White.

2004-Oct-28, 11:33 PM
I thought about putting this in the Face thread, but it seemed different enough to warrant its own.

Any idea what the little "bullseye" in the right-hand side of
this picture (http://www.esa.int/images/TitanFirstCloseUp_01_L.jpg) is? There seems to be a fainter "echo" of it at its 8:30 position too. If we put aside the probable explanations (Zetas, HAARP satellite mind-control facility, secret Nazi weapons-development outpost), I would guess image artifact(s); or could meteoroids thumping into a slushy surface make those marks? They're might regular.
http://www.esa.int/images/TitanFirstCloseUp_01_L.jpg

Add: there's a third faint bullseye above the other two, forming a more-or-less isoceles triangle. I didn't notice any others. Have to look at the higher-resolution images...

They look like classical "dust donuts". As soon as I saw the image I emailed the URL to my Techniques of Observational Astronomy class and asked for comments.

Here is another example from a webCam
http://www.webcam-astrophotography.com/mars/18-july-2003.html

A dust particle very close to the detector surface casts a shadow on the image. If you know the scale of the image you can calculate the distance of the particle from the surface and hence learn which optical surface is involved.

Harvestar
2004-Oct-29, 05:59 AM
At least it's not a pine needle on the dewar window, like what I had in my May run at the VATT. grrrrr.... Dust you can usually flat field out of an image (if it doesn't move around)...

Then there's the (live, and later pulverized) moths my friend found in her images at the 61" at the beginning of Sept. That was a funny story... not.

2004-Oct-29, 10:16 AM
At least it's not a pine needle on the dewar window, like what I had in my May run at the VATT. grrrrr.... Dust you can usually flat field out of an image (if it doesn't move around)...

Then there's the (live, and later pulverized) moths my friend found in her images at the 61" at the beginning of Sept. That was a funny story... not.

Here is a sequence of flats taken while Richard Kowalski was doing an automated cal of his system at Quail Hollow Observatory. A good example of dust donuts.
http://www.astro.ufl.edu/~oliver/ast3722/lectures/CCDImaging/movingDonuts.gif

ngc3314
2004-Oct-29, 12:38 PM
At least it's not a pine needle on the dewar window, like what I had in my May run at the VATT. grrrrr.... Dust you can usually flat field out of an image (if it doesn't move around)...

Then there's the (live, and later pulverized) moths my friend found in her images at the 61" at the beginning of Sept. That was a funny story... not.

Yeah, done that. I formulated a rule that dead insects can flat-field pretty well, but live ones definitely don't. Check out http://www.astr.ua.edu/gifimages/m65.html and the linked image of what we found upon opening the filter wheel.

Tranquility
2004-Oct-29, 04:34 PM
Question though:

Shouldn't these dust particles appear in other photos too, if they are dust on the camera?

Evan
2004-Oct-29, 04:36 PM
Some of the particles are on the filters which are changed depending on wavelength used for the pics.

Tranquility
2004-Oct-29, 04:40 PM
Some of the particles are on the filters which are changed depending on wavelength used for the pics.

So shouldn't we see more bullseyes on pics taken with the same filter? (or is it somehow cleaned when it's changed)

iFire
2004-Oct-29, 04:42 PM
Question though:

Shouldn't these dust particles appear in other photos too, if they are dust on the camera?

They do. (http://www.badastronomy.com/phpBB/viewtopic.php?t=17200) You might have to scroll around though...

Argos
2004-Oct-29, 06:39 PM
Here is a sequence of flats taken while Richard Kowalski was doing an automated cal of his system at Quail Hollow Observatory. A good example of dust donuts.
http://www.astro.ufl.edu/~oliver/ast3722/lectures/CCDImaging/movingDonuts.gif

In the sequence you linked the atmospheric dust particles are gently deposited over the sensor. In the case of the spaceship, the particles (meteoroids) would rather collide with the ship due to their relative speeds, and not simply deposit. The damages to the lenses should be more severe and the area affected in the image should be larger. Since the pattern of the donuts is similar for both cases, it seems to indicate that the Cassiniīs dust was deposited there prior to the launching.

Edited for grammar

Tranquility
2004-Oct-29, 06:40 PM
Question though:

Shouldn't these dust particles appear in other photos too, if they are dust on the camera?

They do. (http://www.badastronomy.com/phpBB/viewtopic.php?t=17200) You might have to scroll around though...

Thanks!

Evan
2004-Oct-29, 07:22 PM
Argos,

I think it highly unlikely that Cassini left the shop with dust on the optics. Nasa in their Imaging FAQ (http://saturn.jpl.nasa.gov/faq/raw-images.cfm#q7) states "Because there is no way to clean the cameras in space, more of these spots may appear as the Cassini mission progresses."

Obviously they are from the spacecraft environment. Impacting particles don't have to hit the optics. They could hit any part of the spacecraft and generate a local cloud of highly charged debris, some of which may find it's way to the optics.

iFire
2004-Oct-29, 07:34 PM
Question though:

Shouldn't these dust particles appear in other photos too, if they are dust on the camera?

They do. (http://www.badastronomy.com/phpBB/viewtopic.php?t=17200) You might have to scroll around though...

Thanks!

You're welcome. I would've posted the specific images but I am at school and don't have the time to search for the pics without getting cought. 8-[