To the Cape! (part 2), For real this time! Options

[edstrick]

"Could there be an advantage in being in shadow? ..."

Yes, but. If the camera lenses were spotlessly clean, diffuse illumination would indeed have advantages. Only with the sun close enough to the field of view to cause actual lens-flares that interfere with visibility in the diffusely illuminated shadow would there be a problem. Unfortunately, post-dust-storm, the lenses are very un-clean.

When all else fails, and you think youi're going blind...... CLEAN YOUR GLASSES.
Unfortunately, the rovers can't.

[ngunn]

Yes, but. Unfortunately, post-dust-storm, the lenses are very un-clean.

Thanks for that reply, but can you clarify something for me. What is the main problem with the dust on the lenses when it comes to taking shots in the cliff shadow specifically? Is it:
1/ simple obscuration causing too-low light levels in the camera, or
2/ interference from light scattered by the lens dust washing out the darker parts of the scene?

If the former there's not much to be done I suppose. But if it's the latter? Presumably it's normal to arrange for the lenses not to be in direct sunlight, and presumably indirect illumination of the lens dust will decrease the closer in we get to the shadowed cliff, so maybe the shadow images will get progressively better for that reason??

Please correct me if I'm hopelessly off-track.

[edstrick]

"...What is the main problem with the dust on the lenses when it comes to taking shots in the cliff shadow specifically? Is it:
1/ simple obscuration causing too-low light levels in the camera, or
2/ interference from light scattered by the lens dust washing out the darker parts of the scene? "

I presume it's mostly the latter, though when dust on lenses was recently recent additions, and the camera looked up at relatively featureless sky, you could actually see out of focus globs of dust on the optics as shadows. When it's thick enough, it obscures light, and diffusely transmits it like Titan's atmosphere. But mostly, it's like driving toward the sun 20 min from sunset with a dirty windshield. Unfortunately, with the sun on the north side of the sky, it's the worst case, and its scattered glare is hard to avoid except in early morning or late afternoon, not the best time of day power-wise <regardless of other operating constraints> of the rovers.

[djellison]

Camera in shadow, means rover in shadow, means a big hit on Whrs.

The recent 4.30pm dusk panorama though, is an example of what can happen to help.

Doug

[edstrick]

"Camera in shadow, means rover in shadow, means a big hit on Whrs"

Bet you get cold, fast, too!

[djellison]

You get cold at night anyway

[ugordan]

Would it really get that cold in the shadow and fast? I take it the rarefied martian air sucks at conduction and convection so the primary means of losing heat would be radiation. The rover's not that hot in the first place, so radiative cooling ought to be slow, no?

[ngunn]

Camera in shadow, means rover in shadow

If it's within the cast shadow of the cliff, yes. But if the camera's pointed NW in the morning or NE in the afternoon it should be sufficiently far from the solar azimuth to keep direct sunlight off the lens, no? Your post suggests that something like this tactic is already being adopted.

I suppose as the sky fills a smaller and smaller solid angle as seen by the lens you get down to a limiting situation where most of the remaining illumination of the lens dust is coming from sunlit parts of the rover itself. I'm not familiar enough with the rover geometry to know how significant that would be.

Anyhow, the pictures so far have been truly spectacular. Congratulations to the rover team, and thanks too for all the great processed images posted here. What a party!

[fredk]

One additional problem to add to ngunn's list is ccd bleeding. If you're trying to image shadowed areas of the cliff, and there are adjacent sunlit areas or sky, you can get severe bleeding ruining the image if you expose for the shadowed areas.

The recent 4.30pm dusk panorama though, is an example of what can happen to help.

That reminds me: I assume you're talking about the sol 1579/80 L1 sequences. Using the rawid utility (which I found on these pages in the distant past), the 1579 sequence went from about 16:35 to 16:50 local time, and 1580 was about 15 minutes earlier.

But using Tman's filename decoder I get considerably later times: 17:45 to 18:00 on 1579 (and again 15 minutes earlier on 1580). My assumption is that rawid has gotten well out of synch, and that Tman's decoder is much closer to the truth. Can anyone clarify this?

If 18:00 is correct, that would definitely be after sunset for Oppy considering that she's in a hole, since even out on the plains the sun would set a bit before 18:00 local solar time near the winter solstice.

[Ant103]

Hi

It was hard, long, but I finally "succed" to make this huge panoramic view of Cape Verde (there already are some vignetign and flares, in spite of my efforts ).


Various resolution can be found at the end of this page (summer page because of impossibility to update my webstite):
http://www.db-prods.net/blog/?page_id=151

And I've made two desktops, one for 4:3 screens, and other for 16:9.
1280
1440

So, time to have a break .

[jamescanvin]

I'm looking for a place to post the 19mb version.

Here it is.



James (on behalf of Astro0)

[Tesheiner]

That reminds me: I assume you're talking about the sol 1579/80 L1 sequences. Using the rawid utility (which I found on these pages in the distant past), the 1579 sequence went from about 16:35 to 16:50 local time, and 1580 was about 15 minutes earlier.

But using Tman's filename decoder I get considerably later times: 17:45 to 18:00 on 1579 (and again 15 minutes earlier on 1580). My assumption is that rawid has gotten well out of synch, and that Tman's decoder is much closer to the truth. Can anyone clarify this?

From the pancam web I get 17:38 for the first picture in the 1579's sequence and 17:55 for the last one.

[fredk]

Thanks, Tesheiner. So it seems Tman's filename decoder agrees with pancam web to 5 minutes or so, which is very good. Also, Tman says that his decoder agrees well with MER Analyst's Notebook and the Mars24 Sunclock.

So that really was a late sequence!

[Astro0]

Here it is. James (on behalf of Astro0)

Thanks James.
I know you went to a lot of trouble to place that online for me.
Very much appreciated.
Cheers
Astro0

[Tman]

From the pancam web I get 17:38 for the first picture in the 1579's sequence and 17:55 for the last one.

Did you ever find out what "LST" there exactly means - is it LTST (Local true solar time)? According the differences to MER Analyst's Notebook until sol 1350 it could/should be. http://marsrovers.jpl.nasa.gov/gallery/all...8P2398R1M1.HTML from sol 1350 shows in the Notebook a difference of 2:45 minutes in the same direction.

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