Phoenix Sun, Sun elevation at Phoenix lander site Options

[Paul Fjeld]

You may be thinking of this famous shot at Endurance:
.....
I'd love to see your result when it's done...

That's it! Thanks!

I also went here:
http://mars.jpl.nasa.gov/MPF/science/clouds.html
... Mark Lemmon's(!) page from Pathfinder, which maybe gives me some hints about the atmospherics - although the best descriptions are of the area around the sun. Maybe I can put some bluish, light clouds off in the distance. Got to be clouds right? Got to have other colors besides browny,pinky,orangy??... (oh yah, I'm on Mars.)

I'll put the final image up on a private/UMSF page when it's done and released. Another week if I'm lucky.

Paul

[Deimos]

Is there a group that is interested in the low-sun/sunrise look of the surface? I have seen some cool stuff of what the sun looks like rising (from Viking as well as MER) but nothing looking the other way.

Phoenix has plans for night imaging. Most of it supports atmospheric science, but some will include a photometric campaign (anit-Sun imaging is key), and I'd hope for a few midnight Sun shots. The "night-time" ("daytime" being the lander work-day) science is delayed, since the systems engineering crowd is fully occupied with the core activities involved in sample acquisition and transfer. Things like a camera pre-heat test are needed before going ahead with "first-time activities". It sounds conservative, but I certainly won't forget that attempting a wake-up for night-time MET and imaging is the last set of commands Pathfinder attempted to obey.

[Paul Fjeld]

Phoenix has plans for night imaging. Most of it supports atmospheric science, but some will include a photometric campaign (anit-Sun imaging is key), and I'd hope for a few midnight Sun shots. The "night-time" ("daytime" being the lander work-day) science is delayed, since the systems engineering crowd is fully occupied with the core activities involved in sample acquisition and transfer. Things like a camera pre-heat test are needed before going ahead with "first-time activities". It sounds conservative, but I certainly won't forget that attempting a wake-up for night-time MET and imaging is the last set of commands Pathfinder attempted to obey.

Thanks Deimos - it sure sounds like you know what you are talking about!!

My deep hope was that the interest in finding out more about "Holy(#$%@^!!)Cow" and thus an early midnight shot looking down-sun with the arm shadow through that feature, would trump engineering concerns. You have made starkly clear a professional tilt for caution! So I'll have to wait or guess what the scene will look like at midnight. Since I service the media, I'll have to guess! ('Why wait when you can speculate' is, I think, the motto...)

Thanks to the LPL PAO, I have the overnight arm position for SOL 12 so that is the view that I'm doing. It was parked over near the +Y (east) Solar Array, out of the way of the work area for photo coverage. I'm now looking more SSW through the lander from the Northeastern edge of that workspace, about a foot and a half off the surface. That great shot fredk pointed me to - MER downsun - looks to have a sun elevation of about 10 degrees (based on where the MER deck shadow cuts the Hi-gain antenna shadow) which is somewhat higher than the nearly 4 degrees at Phoenix midnight (jmknapp's thread-start post here).

Some of the effects that I would expect on the surface seem apparent in that MER hazcam pic, such as the surface brightening as you approach directly downsun (the camera shadow). But the effect of the sky to go "darker" as you move from the horizon then up is something that I want to nail down a bit. Is that an artifact of the camera and extreme fish-eye lens? I've noticed that B/W pics have a lot more interesting contrast than their color versions; Mars seems to want to blandify everything in a haze of pinkish/orangy-brown!

And then, could there have been any clouds on SOL 12 at midnight? One of the benefits of art is that I can use something akin to artist's licence here (but not a 007 licence) - that is, I need to be plausible. Of course, any painting of some clouds would have to be a lie in the specific case, but perhaps acceptable as an illustration of fact: there are clouds at the Phoenix site - this is what they could look like.

I will have a chance to correct any massive errors after the painting's first release. But before that, any speculation is welcome!

Paul

[fredk]

In that Oppy shot looking into Endurance I'd guess the sun is somewhat higher than 10 degrees - local time was only around 4:30pm (the rover may be on a significant slope itself). I'd guess 20 to 25 degrees for the solar elevation.

The sky gradient is a combination of lens vignetting and a real gradient. To see the true sky gradient, look at the MRD image on this page:
http://an.rsl.wustl.edu/mer/merbrowser/pro...FF3352P1214L0M1
This image has been corrected (flat-fielded) for lens vignetting etc. You can see that the opposition surge and sky gradient are reduced, but are still visible.

The direct link to the corrected image is:
http://an.rsl.wustl.edu/mer/merbrowser/pro...RD3352P1214L0M1

[Paul Fjeld]

I'd guess 20 to 25 degrees for the solar elevation.
...
To see the true sky gradient, look at the MRD image on this page:
http://an.rsl.wustl.edu/mer/merbrowser/pro...FF3352P1214L0M1
This image has been corrected (flat-fielded) for lens vignetting etc. You can see that the opposition surge and sky gradient are reduced, but are still visible.

Thanks!

I wonder how much that vignetting would be apparent in color and, more importantly, to the eye. I'm sorry that the MER shot has such a high solar elevation after all. I'd like to guess that the gradient effect is even more pronounced at low sun, but I've never seen any pic from Mars with that, other than the hazcam shot.

Paul

[djellison]

Using midnight mars browser with Dan Crottys calibrated Pancam imagery, you can often see quite extensive sky surveys showing what you're after, I think.

Doug

[fredk]

I wonder how much that vignetting would be apparent in color and, more importantly, to the eye.

The vignetting part of the gradient is purely a camera effect - you wouldn't see it by eye. The corrected image I linked to should be close to what the eye would see in terms of sky gradient.

[Paul Fjeld]

The corrected image I linked to should be close to what the eye would see in terms of sky gradient.

Okay, great. I'll do the >gradient< close to that.

Doug: thanks for the Midnight Mars Browser suggestion (man, I really am a newbie...). It is very cool. I need a couple of days to troll through these many years(!) of roving, but it is amazing. So is Emily's library of Phoenix raw images with the LST,Az/El and Camera ID. Sad she's on vacation...

Paul

[mchan]

Thanks Deimos - it sure sounds like you know what you are talking about!!

BTW, Deimos is the author of the Pathfinder clouds, sunrises, and sunsets page you referenced earlier.

[Paul Fjeld]

I had an inkling... this is a great site!

Saw the atmospheric shots taken from the Phoenix SOL 14/15 downlink to coincide with one of the orbiters' data takes. It looks like you can see stars in a few of the shots! I will find out what the starfield should have been at the time and see if anything fits. In daylight, I didn't think you could see stars on Mars.

Paul

[fredk]

Before you go through the trouble of fitting stars, could you point to a particular image? They took a bunch of solar filter images to characterize the noise, which might be what you're seeing. The Martian daytime sky is really quite bright...

[ugordan]

Agreed, it's exceedingly unlikely those pixels are stars. Rather, they're hot pixels in the CCD. When doing long exposures, differences in sensitivity (dark current actually) of each pixel becomes quite noticeable.

[Paul Fjeld]

Okay, that saves me some trouble. I could swear I recognized a constellation!

Paul

[Astro0]

I was struck by this image from Sol16.


I'm wondering if, when everything else is done, that near the end of the mission they could try for something like this.


Just a thought.
Astro0

[Paul Fjeld]

Cool! I've often wished that some of the operations "budget" could be used for dramatic shots like this or, at least, pictures when the sun is low. I think it would make for some very neat images that might wind up iconic.

Paul