[X] My Assistant

[Phil Stooke]

Seeing the crater would have been nice, and layering in the walls very nice, but I imagine the most important results come from the remote sensing of the ejecta composition.

In fact if there was relatively little volatile ejecta and lots of dust, as suggested so far, there may not have been a lot to see in the crater anyway. I think (admittedly on little evidence) that any difficulties may be as much caused by the comet itself as by the focus problem.

I'm an image guy so the focus thing does concern me, but if spectroscopy answers the composition questions that's probably going to be a great result. I'm not as concerned as Bruce about this. So far.

I am concerned about that cost cap decision, though.

Phil

[tedstryk]

I am concerned about that cost cap decision, though.

Phil

I will be concerned about it when it passes. So many things show up in committee and versions of bills that never see the light of day that I wouldn't have any hair left if I fretted over each one. If that decision makes it into the final bill, that spells trouble.

[edstrick]

Phil: From what I can see, deconvolving the images increases single-pixel to few-pixel noise and artifacts "several times", about what you'd expect. If the crater would have been visible in images just before shield-mode at say 5% contrast through the plume, cutting contrast several times could eat your lunch.

And unfortunately, I don't expect diddly-squat from color imaging of the nucleus now. Typically, there is very little color contrast on "small bodies" in Galileo and NEAR and Giotto images and you need to squeese out maximum signal-to-noise from the data to have anything useful. NEAR, for example, had a nasty noisy little camera and could barely see color variations in different albedo materials on Eros. Blow your signal-to-noise level on deconvolution of images of a small body, and you've lost not just single-pixel color information but lost integrating color voer enough pixels on a given feature for useful color information at all. I hope I'm, wrong, but I expect to be frustrated.

[DDAVIS]

[quote=edstrick,Jul 19 2005, 09:07 AM]
Phil: From what I can see, deconvolving the images increases single-pixel to few-pixel noise and artifacts "several times", about what you'd expect. If the crater would have been visible in images just before shield-mode at say 5% contrast through the plume, cutting contrast several times could eat your lunch.

This would be a good kind of mission to repeat on a series of small bodies for comparison, with good cameras. There is no reason to think we missed a once in a lifetime opportunity.

Don

[antoniseb]

This would be a good kind of mission to repeat on a series of small bodies for comparison, with good cameras. There is no reason to think we missed a once in a lifetime opportunity.

Yes, including trying to hit one of the hyperbolic orbit comets as they come in. If we build and keep a few Deep Impact probes around for such an occasion, we'll be ready.

[elakdawalla]

I'm having trouble with the Quicktime plugin in Adobe Imageready (stupid Quicktime 7). Can anybody convert the two Deep Impact .movs to animated GIFs for me so I can play with them?
http://photojournal.jpl.nasa.gov/catalog/PIA02125
http://photojournal.jpl.nasa.gov/catalog/PIA02130

--Emily

[um3k]

I've converted the files, Emily, but they are rather large, so I'll need your email address in order to send them to you.

[tedstryk]

Ed: Yes, but I wonder what MRI got...while its resolution is poorer, it might have the S/N ration to identify broad variations.

[elakdawalla]

I've converted the files, Emily, but they are rather large, so I'll need your email address in order to send them to you.

Thanks very much for this, um3k. I took the GIFs you sent from the ITS and the MRI and deleted 5 of every 6 frames (they were redundant). I noticed that the levels varied a lot from frame to frame (I wonder why they didn't correct that? seems like it should have been easy), so I did a quick and dirty job of adjusting the levels so that the histograms of all the ITS images looked reasonably similar, which helps to smooth out the animation a bit. For the MRI animation, I rotated the frame a quarter turn so that it matched the orientation of the ITS animation a little more closely. Finally I combined the two into one movie:

Deep Impact combined animation (1.6 MB)

You can also see it on this web page:
Year in Pictures: Deep Impact

--Emily

[um3k]

Very nice, Emily!

[Bob Shaw]

I thought the development of the ejecta plume was fascinating!

Bob Shaw

[Guest_RGClark_*]

Is it definitively known that the secondary plume did not have significantly more water than the conditions before the impact?


- Bob Clark

[ljk4-1]

Is it definitively known that the secondary plume did not have significantly more water than the conditions before the impact?
  - Bob Clark

Is there the possibility that the impact destroyed materials that could not be analyzed by the flyby craft as a result?

In preparation for a probe to land on Europa and dig/melt/blast through its ice crust, perhaps a "test" mission to a comet trying out similar methods (and getting plenty of comet science in the process without having to blow up anything) should be in first order.

I am surprised that the DI mission team thought that they would have a clear view into the crater created by the impactor, rather than the cloud of debris we saw instead. Didn't they do computer modeling?

[ugordan]

Is there the possibility that the impact destroyed materials that could not be analyzed by the flyby craft as a result?

It's possible a small amount of material in the immediate vicinity of the impact got chemically altered due to very high temperatures, but I suspect the majority of the plume material was simply "dislodged" and ejected, followed by sublimation of volatiles underneath.

In preparation for a probe to land on Europa and dig/melt/blast through its ice crust, perhaps a "test" mission to a comet trying out similar methods (and getting plenty of comet science in the process without having to blow up anything) should be in first order.

Any lander on Europa is likely to only do melting of the ice, blowing up and excavating is pretty much out of the question - you'd need to carry explosives and the ice is virtually rock at those temperatures. Also, an Europa lander that melts its way through will benefit from the surface gravity to drag it downwards, the latter is practically nonexistent on a small comet. Their respective compositions are radically different, too, comets being icy dirtballs (as opposed to dirty iceballs, which was thought until recently).

I just don't see a point in proof testing a Europa lander on a comet.

I am surprised that the DI mission team thought that they would have a clear view into the crater created by the impactor, rather than the cloud of debris we saw instead.  Didn't they do computer modeling?

They probably assumed the comet would have a much higher percentage of ice vs dust. You can't model the behaviour of something you don't know what it's made of. That's one of the reasons this mission was flown in the first place.

[ljk4-1]

It's possible a small amount of material in the immediate vicinity of the impact got chemically altered due to very high temperatures, but I suspect the majority of the plume material was simply "dislodged" and ejected, followed by sublimation of volatiles underneath.
Any lander on Europa is likely to only do melting of the ice, blowing up and excavating is pretty much out of the question - you'd need to carry explosives and the ice is virtually rock at those temperatures. Also, an Europa lander that melts its way through will benefit from the surface gravity to drag it downwards, the latter is practically nonexistent on a small comet. Their respective compositions are radically different, too, comets being icy dirtballs (as opposed to dirty iceballs, which was thought until recently).

I just don't see a point in proof testing a Europa lander on a comet.
They probably assumed the comet would have a much higher percentage of ice vs dust. You can't model the behaviour of something you don't know what it's made of. That's one of the reasons this mission was flown in the first place.

I am sure I will be told that I am missing some point here, but considering that we've known for centuries about the vast amount of material constantly blown off by comets nearing the Sun (and even far away, like Hale-Bopp), why would scientists have assumed that the crater view would be relatively clear - especially since the flyby craft wouldn't be able to hang around for very long?

It's too bad the flyby craft couldn't have gone into orbit instead to wait for the debris to settle (yes, I know that is no trivial exercise and would have added great expense to the mission) or if the flyby or some future mission could go by Tempel 1 again to see what transpired after the impact.

The reason I am making a big deal out of this is that one of the big goals of the mission (stated numerous times over by NASA) was to have the flyby craft peer into the crater to learn about the comet's interior. Yes, they got measurements of materials from the blast plume, but we did not see the interior. Like I said, how did they hope to accomplish that with such a short time period?