"artificial image artifacts" Saturn Equinox (2009 Aug 25)

[cwmdavis]

Oh, oh, dirty sensor! Many need to send up the space shuttle for a cleaning ...

http://apod.nasa.gov/apod/ap090825.html

[Aqua]

Image artifacts they might be... but might some of them also not possibly be meteor(s) passing thru the ring plane?

[neufer]

Image artifacts they might be... but might some of them also not possibly be meteor(s) passing thru the ring plane?

Highly unlikely. Blame cosmic rays.

[NoelC]

The little streaks are most likely, as Neufer says, particle hits on the imager. One sees a lot of these in Hubble images, especially if the sun is active. Gives one a healthy respect for the protection given us by our wonderful atmosphere.

I'd also like to point out the banding distortion (the horizontal light and dark streaks at a more or less constant frequency)... Those are most definitely not actual light and shadow on Saturn's rings, especially considering the real shadow? near the bottom that's not horizontal.

It is possible to greatly reduce such distortion with digital processing, and it is particularly easy to remove it from an image that has virtually no other horizontal components.

Click on this small image to see a large one.



-Noel

[grump]

The little streaks are most likely, as Neufer says, particle hits on the imager.....
-Noel

And if they are not? Has anyone read "Footfall" by Larry Niven and Jerry Pournelle?
http://en.wikipedia.org/wiki/Footfall

- unserious Jim

[geckzilla]

I don't understand why the streaks are so crisp. I don't think they are any kind of flying debris but I don't understand why they are in focus, either. Which part is damaged?

[zbvhs]

Would the image artifacts be stars? If a timed exposure was required to capture the fainter details of the rings, seems like stars should become visible. (Are technical details such as exposure time published with the photographs?)

Has an explanation of the rings' structure been proposed? Why, for example, are the rings perfectly circular? (Are they perfectly circular?) Why are they orbiting in the planet's equatorial plane, i.e., zero inclination? Are they orbiting in the usual sense or is some other mechanism at work? Would gravitational perturbations caused by Saturn's moons be evident in the rings' structure?

[BMAONE23]

Would the image artifacts be stars? If a timed exposure was required to capture the fainter details of the rings, seems like stars should become visible. (Are technical details such as exposure time published with the photographs?)

Has an explanation of the rings' structure been proposed? Why, for example, are the rings perfectly circular? (Are they perfectly circular?) Why are they orbiting in the planet's equatorial plane, i.e., zero inclination? Are they orbiting in the usual sense or is some other mechanism at work? Would gravitational perturbations caused by Saturn's moons be evident in the rings' structure?

In reply to your last query about moons within the rings
http://www.nasa.gov/mission_pages/cassi ... 11653.html

More info on the Rings from WIKI
http://en.wikipedia.org/wiki/Rings_of_Saturn

[Chris Peterson]

I don't understand why the streaks are so crisp. I don't think they are any kind of flying debris but I don't understand why they are in focus, either. Which part is damaged?

They are classic cosmic ray hits on the CCD. I get them all the time on my images, and the rate is higher in space. Sometimes the high energy particles directly hit the CCD, which usually creates a really messy splash. Most often, they first strike something else, like the CCD chip packaging, surrounding camera structure, etc, and this produces a shower of lower energy particles- one or more of which may strike the sensor. When that happens they can dump a charge into one or more pixels, which shows up as a white point or a white streak. They appear to be in focus because they are affecting the pixels directly, and there is a sharp boundary between affected and unaffected pixels. Of course, there are no optics involved so "focus" really has no meaning.

[Chris Peterson]

Would the image artifacts be stars? If a timed exposure was required to capture the fainter details of the rings, seems like stars should become visible. (Are technical details such as exposure time published with the photographs?)

I haven't seen any technical exposure details published. Even edge on, this is still ice illuminated by sunlight, so I expect the exposure was pretty short. That said, there are a few bright spots that might possibly be stars- hard to say without more information about exposure and orientation. But without doubt, most of the artifacts are the product of high energy particles hitting the sensor.

[geckzilla]

Oh, so it's not like something has physically made an impact and damaged something then. Oops.

[Chris Peterson]

Oh, so it's not like something has physically made an impact and damaged something then. Oops.

It's still an "impact" when a high energy particle hits the sensor, and these impacts do occasionally cause permanent damage. CCDs degrade over time because of the cumulative damage of cosmic ray impacts.

[Andy Wade]

Thanks Chris, That's really helped my understanding. As always...