Comet observation from Mars, comets close encounters to Mars in 2013 and 2014 Options

[mcaplinger]

Hopefully the PDS images will be a help in solidly confirming it when they are released.

Obviously the science team (of which Deimos is a member) already has the best available images.
If you're proposing a scenario where no one on the camera team can see the comet and you find it in the PDS images, that would be a triumph of amateur processing, but (with all due respect) doesn't seem especially likely.

The HiRISE image suggests the target is not very bright, but on the other hand, the exposure times for a linescan system are probably pretty short.

[fredk]

ISON shouldn't have a trail that follows the stars, but should move between long exposure frames and have its own movement or trail if the images were taken with very long exposure.

Actually I meant pointlike apart from any motion, ie pointlike if you could image it with a very short exposure. (Actually psf-like, of course.) I was getting at the difference in scale between pancam and the hirise image - unfortunately we're not told the hirise scale.

ISON must have moved between the MER and MSL sky positions in about 7 hours. But that separation is only very roughly 10 times the star trail lengths, which presumably correspond to ~1 minute exposures. So the comet's motion relative to the stars would be roughly 7 hours/10 minutes ~ 40 times slower than the stars' trailing (sidereal) motion. So the comet's motion in a ~1 minute exposure should be essentially the same as the stars, so I'd expect a trail for ISON with very similar length and orientation as the stars' trails. (This ignores the different locations of MER and MSL, though it would be a coincidence if they conspired to cancel out the comet's motion.)

[djellison]

Hopefully the PDS images will be a help in solidly confirming it when they are released.

We will know long before then.

[Gerald]

I'm curious though exactly how he processed those.

There is some tolerance in processing FredK's image taken as starting point. Here a graphics which should provide sufficient detail of how a resulting image with a position estimate can be obtained:


I don't think, there is a simple yes/no-answer, whether or not ISON is seen in the images. The above processing is just a draft showing that the images are worth a closer look.
A more detailed statistical discussion about acceptable a-priori knowledge, the resulting conditional probabilities and confidence levels of some properties of ISON (like position or brightness) will be needed. That's worth a paper, but clearly outside the limitations of a short post.

[djellison]

That's worth a paper....

Not with the raw JPG's it isn't. By the time calibrated images are in the PDS, we'll have seen the results already from the science team, I'm sure.

[Gerald]

No doubt, they'll do it (with the calibrated images)!
And I'm fully confident, they'll take the time necessary to do it in an appropriate way.

[fredk]

Pancam L1 from 3443 - presumably the ISON field again. Differences of two frames, stacked (with rotation), averaged, and 1 pix Gaussian blurred:

Some further S/N improvement could be had by including more differences with the third frame. I don't have the software to check where ISON was at the time these frames were taken.

[James Sorenson]

I have to now agree with everyone that what I was seeing was just noise in the previous images. Fred I again used your image after processing my own, here is the Starry Night simulation overlay onto yours. This must have been around close approach to Mars on October 1st.



Animation
http://www.flickr.com/photos/43581439@N08/...in/photostream/

[fredk]

Some modelling of the particle flux at Mars during the Siding Spring encounter here. Subscription needed for the full paper, but all of the paper's figures appear to be free for all to see. Also a popular news story based on the paper here.

The predicted fluence is roughly 0.1 (potentially damaging-sized) particles per square metre. My sense is that the uncertainties in calculating that value are huge. Still, it is interesting (and a bit disconcerting) that the predicted fluence is within an order of magnitude of 1 particle per square metre.

[Greenish]

NEOWISE image of C/2013 A1 (and apparently Hubble did recently too), and discussion of planned encounter activities/risks to Mars orbiting & surface assets.

http://www.jpl.nasa.gov/wise/newsfeatures....elease=2014-026

[TheAnt]

At a distance of a mere 170 000 kilometers its not just a risk but could also be one fantastic opportunity for observation of comet C/2013 A1.
Lets see what will be proposed.

[JohnVV]

the tail is over exaggerated ( about a factor of 10-20 )
https://picasaweb.google.com/lh/photo/jAPqG...feat=directlink

from Gale on Oct. 19 2014

[Explorer1]

Hubble took a look; two jets are evident!

http://mars.nasa.gov/news/whatsnew/index.c...amp;NewsID=1615

[Paolo]

a detailed analysis of the Siding Spring encounter appeared today on the arXiv site: Trajectory analysis for the nucleus and dust of comet C/2013~A1 (Siding Spring)

[SteveM]

a detailed analysis of the Siding Spring encounter appeared today on the arXiv site: Trajectory analysis for the nucleus and dust of comet C/2013~A1 (Siding Spring)

Fragment impacts very unlikely. A picture worth a thousand words.