Mars rovers provide another perspective on farside solar activity

[tniickck]

looking at the farside activity GIF i would say this group almost or already decayed
Movie.gif (900×350) (stanford.edu)

[Philalethes]

15 minutes ago, Sapphire828 said:

I was under the impression that the colored dots in the background were dead pixels or issues with the camera sensor. If they are consistent, maybe they could be used to discern the orientation of the camera when the photo was taken?

If they really are just noise then they definitely won't be of any use at all. They wouldn't give any more information about the orientation of the camera than the resulting image as presented, which is sadly none at all.

I tried running the surrounding imagery through Astrometry.net, but it didn't find any matches at all; I also had a hard time finding a match manually by trying to estimate the position along the ecliptic, so I doubt that's ultimately a viable way to do it after all. Maybe it is just noise too (I sent NASA an email asking about it, maybe I'll get an answer).

Too bad, the quest for a way to find the Mastcam orientation continues.

Edited August 24, 2023 by Philalethes

[hamateur 1953]

3 hours ago, tniickck said:

looking at the farside activity GIF i would say this group almost or already decayed
Movie.gif (900×350) (stanford.edu)

Yes. It most certainly looked promising! Even up to the very last. Bummer.  Flux falling off unfortunately as well.  I’m not throwing in my towel yet, it may reform as others have before. 

Edited August 24, 2023 by hamateur 1953
Fluxed

[Philalethes]

Alright, here's a second attempt at figuring out the orientation roughly speaking (after the first was revealed to be an abject failure by the point made by Aten). Looking over the images from that day we see two different images taken ~45 minutes apart:

This, to me, especially combined with the red and blue hues of the surrounding colored pixels, indicates to me that we are indeed looking at surrounding stars, as I initially suspected (although exactly which stars we're looking at was clearly totally wrong on my part). At least this rules out fluctuating noise, but as suggested by Sapphire above I suppose it could still potentially be dead pixels; still seems a bit strange that those dead pixels have the exact hues you typically find in stars, though. Would definitely love more input from people who know more about camera technology on this matter.

In any case, if we assume that those are in fact stars, then we can at least use these two images to find a rough approximation of the ecliptic, as the "Martian ecliptic" will only differ from the actual ecliptic by less than 2 degrees. Tracing a rough line between the centers of the two discs:

This is however not necessarily the orientation as seen in the other imagery, because near the solstices that orientation will be tilted by ~7.25° to the ecliptic, while near the equinoctes it will be tilted ~0°; so here we need to figure out roughly what the case would be if Earth were at that position in its orbit. Given the aforementioned ~135° angular separation between Earth and Mars it means Earth would be at the equivalent of ~137 days before the day it was taken, i.e. ~141 days before today, which would be around April 5; at that point the Solar tilt would have just passed the March equinox and be at around ~2° right of vertical here. So, using the online protractor again and drawing up the new orientation (blue) and central meridian (red), it would look more like this:

Actually not that far from the previous suggestion, even though that's most likely entirely by chance. That does however mean the previous estimate can be used as a basis to simply recalculate based on the spot's position relative to the central meridian.

Here the spots are located at ~8E as per my estimate using an overlay, we could say 10E just to be generous; that would mean an additional 8 degrees, increasing the previous estimate by ~14 hours, so instead of around 14:30Z today it'd rather be around 04:30Z tomorrow (08-25T04:30Z).

This of course still hinges on the supposition that those are in fact stars and that we're seeing the relative movement of Sol across them, but hey, at least it's something. Anyone who wants is of course free to pull apart and unravel whatever mistakes I might have made.

4 hours ago, tniickck said:

looking at the farside activity GIF i would say this group almost or already decayed
Movie.gif (900×350) (stanford.edu)

That doesn't look too great. At least it does seem to also suggest we should be seeing it today or tomorrow, whatever might be left of it anyway.

Edited August 24, 2023 by Philalethes
Solar W and E

[Sapphire828]

Nice work! I think Aten is correct, to see the sunspots from Mars surface during the day, a majority of the light would have to be filtered and the stars light would likely not be visible. Red and blue pixels would make sense for star colors but there are green pixels too. I'm pretty sure they are artifacts of the camera. The vertical lines are artifacts too. 

There is a vertical line that is on the left of the solar disk pointing to a green pixel. This can be seen as far back at Sol 749 (Mar30, 2023). With the rover moving around on the surface, it would be improbable to have that line line up perfectly with the same "star". I'm pretty confident these are artifacts, seems like the radiation at the surface is affecting the electronics. 

Good idea using the pictures 45min apart to estimate the ecliptic. The Stanford farside website suggests the next spot coming over should be appearing soon, but doesn't look as strong as expected, maybe it did decay quickly? 

Patiently waiting... 

[tniickck]

good news-there is something on the limb around S15 that looks like 2 spots or a single one. waiting for newer image

[Philalethes]

3 minutes ago, Sapphire828 said:

Nice work! I think Aten is correct, to see the sunspots from Mars surface during the day, a majority of the light would have to be filtered and the stars light would likely not be visible. Red and blue pixels would make sense for star colors but there are green pixels too. I'm pretty sure they are artifacts of the camera. The vertical lines are artifacts too. 

There is a vertical line that is on the left of the solar disk pointing to a green pixel. This can be seen as far back at Sol 749 (Mar30, 2023). With the rover moving around on the surface, it would be improbable to have that line line up perfectly with the same "star". I'm pretty confident these are artifacts, seems like the radiation at the surface is affecting the electronics. 

Good idea using the pictures 45min apart to estimate the ecliptic. The Stanford farside website suggests the next spot coming over should be appearing soon, but doesn't look as strong as expected, maybe it did decay quickly? 

Patiently waiting... 

I still don't think they're correct, and I do still believe they are stars based on what I'm seeing. There is a somewhat green tint to the light of the "whiter" stars, but that is most likely because the camera is correctly registering the fact that "white" stars are emitting slightly more green light than of other frequencies; it also explains why the green tint is fainter than the red and blue hues of the other stars. I do agree that the vertical lines are likely artifacts, but they appear to be artifacts stemming from the light of the stars, as you can make out faint lines running down from most of them if you look closely; you also see diffraction spikes on many of the stars, another telltale light-based artifact. I'm certainly no expert on camera technology either, but they definitely don't look like dead pixels at all to me, but rather exactly as I'd expect light sources to look like. Yet another sign is that two of them appear to be covered as they are passed by, and another one is revealed from beyond the disc; this is difficult to explain if they really are just somehow dead pixels, as you can make out that it is indeed the case if you look very closely. As you suggest it would also be an idea to look at other images, but I do not see any trace of any of those artifacts in any of the other images I looked at from the past week or so, only in the images of the sunspots where the same (presumed) light sources are present.

So personally I'm rather confident about the opposite at this point, i.e. that they really are stars, but I could definitely be wrong. The above is simply my reasoning for why I believe that to be the case.

It should also be noted that if we can assume that the rover didn't move at all during this time and that the image was taken from the exact same position and in the same orientation, then you can use the exact same reasoning to determine the approximation to the ecliptic regardless, as all you really need is the path of the movement between the two images relative to the orientation of the surface. I don't know if that is a reasonable assumption or not, but my first guess would be that it probably is, and that they likely kept the rover still and the camera positioned in the same way for the consecutive shots over the hour or so it took them. If they really are stars we're seeing then that's of course the case indeed, but it's rather if they're not that it could potentially still be a fair assumption.

And yeah, sadly it did look from the imagery tniickck posted that it had been decaying, but I guess it's hard to say for sure with farside imagery. Presumably we'll soon get an actual view of it so we can check out what it really looks like.

PS:

Here's the source of the two images in question for anyone who wants to check for themselves and see what they think: this is the first image from 12:50:30Z and this is the second from 13:36:51Z, both from August 20, 2023.

[tniickck]

it is badly seen, but at least something @Philalethes

looking at 19:30 image i can certainly say it is a penumbra (dont know how is it called correct in english)

Edited August 24, 2023 by tniickck

[Philalethes]

22 minutes ago, tniickck said:

it is badly seen, but at least something @Philalethes

looking at 19:30 image i can certainly say it is a penumbra (dont know how is it called correct in english)

I still have a hard time seeing anything clearly yet, but maybe you have elven eyes. As for the terms both umbra and penumbra are used in English to refer  respectively to the dark blacker area in the middle and the surrounding more orange areas.

[hamateur 1953]

44 minutes ago, tniickck said:

good news-there is something on the limb around S15 that looks like 2 spots or a single one. waiting for newer image

I am hoping for some solid activity as are we all.  And an assignment so at least we may mourn its demise!  Haha. 

[tniickck]

20:00

[Sapphire828]

@Philalethes I have one more counter for the camera artifacts theory... on the right of the solar disk there is a longer vertical blue-ish line that points to a green pixel near the top of the image. In the recent pictures (Sol 880,884,888) this is consistent, but if you go back to Sol 749 the blue-ish vertical line is faint but the green light is not there.

Additionally, there are some very faint red and green spots on the Sol 749 picture that still match the Sol 888 spots in the near vicinity. 

The gif you posted earlier really helped to show these changes. It would be interesting to see another gif over a longer time scale.

[Philalethes]

55 minutes ago, Sapphire828 said:

@Philalethes I have one more counter for the camera artifacts theory... on the right of the solar disk there is a longer vertical blue-ish line that points to a green pixel near the top of the image. In the recent pictures (Sol 880,884,888) this is consistent, but if you go back to Sol 749 the blue-ish vertical line is faint but the green light is not there.

Additionally, there are some very faint red and green spots on the Sol 749 picture that still match the Sol 888 spots in the near vicinity. 

The gif you posted earlier really helped to show these changes. It would be interesting to see another gif over a longer time scale.

Looking at the imagery I still really don't see anything like it on any of the other images. Perhaps you could provide some of the earlier and more recent images where you believe you're seeing it and when they were taken so I could take a look. Also, the lights in question are clearly consistent from image to image in the ones in question, so if they were really artifacts you'd expect to see all of them in all the images, and that really doesn't seem to be the case at all.

So I still don't believe the gif is showing any such changes at all, just slight variations in the light-based artifacts that I still assume are from stars; but again, I could still be wrong, I'm certainly not ruling that out.

[Sapphire828]

Here's what I'm seeing: Turn up your screen brightness & clean your screen
[Top right quadrant is where I'm seeing the main changes]
https://giphy.com/gifs/tiZOXxvIKVZvrhfDpm/fullscreen

May 6, 2021 (Sol 75) at the local mean solar time of 12:36:00.
Sept. 12, 2021 (Sol 200) at the local mean solar time of 16:37:18.
Feb. 7, 2023 (Sol 700) at the local mean solar time of 12:44:49.
May 21, 2023 (Sol 800) at the local mean solar time of 12:14:07.
Aug. 20, 2023 (Sol 888) at the local mean solar time of 13:36:51.

There should be different constellations behind the sun at each of these points in the year.
https://www.solarsystemscope.com/

I'm thinking radiation is causing these artifacts (sensor/electronic damage) and they seem to be permanent.
As time goes forward they don't disappear, but rather new ones appear.

***Sol 300, 406, 512, and 600 still have these red, blue, green lights but are not consistent with the gif.
**Sol 200, 300, 406 is an interesting sequence, here it looks like stars shifting and does not fit the camera artifact theory.
*I'm not completely sure at this point, maybe same optics but sometimes uses different sensors (?)
 

[Philalethes]

3 hours ago, Sapphire828 said:

Here's what I'm seeing: Turn up your screen brightness & clean your screen
[Top right quadrant is where I'm seeing the main changes]
https://giphy.com/gifs/tiZOXxvIKVZvrhfDpm/fullscreen

May 6, 2021 (Sol 75) at the local mean solar time of 12:36:00.
Sept. 12, 2021 (Sol 200) at the local mean solar time of 16:37:18.
Feb. 7, 2023 (Sol 700) at the local mean solar time of 12:44:49.
May 21, 2023 (Sol 800) at the local mean solar time of 12:14:07.
Aug. 20, 2023 (Sol 888) at the local mean solar time of 13:36:51.

There should be different constellations behind the sun at each of these points in the year.
https://www.solarsystemscope.com/

I'm thinking radiation is causing these artifacts (sensor/electronic damage) and they seem to be permanent.
As time goes forward they don't disappear, but rather new ones appear.

***Sol 300, 406, 512, and 600 still have these red, blue, green lights but are not consistent with the gif.
**Sol 200, 300, 406 is an interesting sequence, here it looks like stars shifting and does not fit the camera artifact theory.
*I'm not completely sure at this point, maybe same optics but sometimes uses different sensors (?)
 

You're right, in those images you can see the same "lights" in the exact same positions, that means they definitely can't be stars after all. I guess there must indeed be something about pointing the camera directly towards the disc that causes them to appear somehow.

Then the hope that the aforementioned reasoning about the orientation remains correct hinges on the hope that the rover and camera remain completely still for the duration of the images, but we don't know that for sure; maybe I'll get a response from NASA on that one at some point.

If it turns out not to be the case, i.e. that the rover and/or camera moves between shots, then I don't see how you could possibly figure out the orientation, at least not without imagery over consecutive days to give you some idea about how the sunspots themselves move.

Edit:

Actually, thinking even further about it, of course even if the rover and the camera remains completely still the observed movement will mostly be due to the rotation of Mars rather than the apparent movement of Sol due to the orbit of Mars (if the "lights" had really been stars then that movement would have had to have been due to the orbit, but that's evidently not the case), so I think that hope is pretty much done for at this point; that renders the second attempt a dud too.

In other words, at this point I think the only way you could reliably figure out the orientation would be to have imagery over consecutive days to see the movement of the sunspots themselves.

Edited August 25, 2023 by Philalethes
grammar & edit

[Sam Warfel]

Little late to this discussion, but I thoroughly enjoyed reading over the research.
I am aware it's settled at this point, but I did want to mention that those bright pixels in the background look like classic hot pixels to me, a phenomenon often seen in astrophotography.  Some pixels are dead/defunct, and overflow to their maximum brightness, even with no light coming into the camera.  This can clearly be seen in the calibration frames used in astrophotography called "dark frames", made with the same exposure as the lights (real pictures), but with lens caps in place so the image train is completely dark, revealing what is hot pixels and noise.
This is further confirmed by the green, magenta, and blue appearance of the pixels in the rover images, being from the RGB pixels of the sensor itself.  There are no green looking stars, and the colors are too saturated to be a natural picture of the stars, let alone through atmosphere in the day.
I do agree that it is probably possible to image the stars during the day from Mars, since it is possible on Earth with proper filters.  However, it would be very difficult, require filters that Perseverance probably does not have, and require careful processing and composition back with the sun images, which I am all but sure the team is not doing each time.
Anyway, just thought it was interesting.  I upload a copy of one of my dark frames, a 2 minute exposure taken with my DSLR, so granted, probably a different image sensor technology than the rover, but likely similar.  Also, the ambient temperature affects the degree of noise and hot pixels, my DSLR shows many in the summer and few in the winter, when temps are far below freezing.  Does anyone know what the daytime temps on Mars are at this time of year?  Hot, or cold?  It's possible we may see seasonal variation in the degree of hot pixels, if the temps swing widely.  Or, maybe it's due to some radiation on Mars that is blocked here, and not a classic hot pixel.
That being said, as you can see, the hot pixels in the mastcam images look remarkably similar to the ones in my dark frame, in color, distribution, etc.
Interesting comparison!

(have to click on image to see the small hot pixels, download and zoom in for best view).

[Philalethes]

7 minutes ago, Sam Warfel said:

Little late to this discussion, but I thoroughly enjoyed reading over the research.
I am aware it's settled at this point, but I did want to mention that those bright pixels in the background look like classic hot pixels to me, a phenomenon often seen in astrophotography.  Some pixels are dead/defunct, and overflow to their maximum brightness, even with no light coming into the camera.  This can clearly be seen in the calibration frames used in astrophotography called "dark frames", made with the same exposure as the lights (real pictures), but with lens caps in place so the image train is completely dark, revealing what is hot pixels and noise.
This is further confirmed by the green, magenta, and blue appearance of the pixels in the rover images, being from the RGB pixels of the sensor itself.  There are no green looking stars, and the colors are too saturated to be a natural picture of the stars, let alone through atmosphere in the day.
I do agree that it is probably possible to image the stars during the day from Mars, since it is possible on Earth with proper filters.  However, it would be very difficult, require filters that Perseverance probably does not have, and require careful processing and composition back with the sun images, which I am all but sure the team is not doing each time.
Anyway, just thought it was interesting.  I upload a copy of one of my dark frames, a 2 minute exposure taken with my DSLR, so granted, probably a different image sensor technology than the rover, but likely similar.  Also, the ambient temperature affects the degree of noise and hot pixels, my DSLR shows many in the summer and few in the winter, when temps are far below freezing.  Does anyone know what the daytime temps on Mars are at this time of year?  Hot, or cold?  It's possible we may see seasonal variation in the degree of hot pixels, if the temps swing widely.  Or, maybe it's due to some radiation on Mars that is blocked here, and not a classic hot pixel.
That being said, as you can see, the hot pixels in the mastcam images look remarkably similar to the ones in my dark frame, in color, distribution, etc.
Interesting comparison!

(have to click on image to see the small hot pixels, download and zoom in for best view).

Great information, exactly the type of more in-depth knowledge about camera technology I suggested would be useful to know here, even more so when it's based on first-hand experience; also a very poignant example showing the effect clearly. I still find it interesting how some of the ones in the Mastcam imagery looks very similar to diffraction spikes, extending outwards and seemingly beyond one pixel (almost like it's "spilling over" into the nearby pixels), which definitely played a role in fooling me. The vertical lines are also interesting, I'm not sure to what extent the phenomenon you just described also covers these, but if you know more about it I'd love to hear it.

And yeah, the point about the processing and filtering that would have to be done is a good one that I thought a bit about, it would be unlikely that they'd do something like that for a camera that, as Aten said, is meant to take photos of rocks and dirt. The imagery from the site is also supposedly raw, which I assume would preclude compositing.

Hopefully the next time there's a big spot visible they'll snap some images on consecutive days so we can figure out the orientation, or maybe NASA could possibly calculate it from the rover and camera's position and orientation and make it clear. At least I don't see any other way now that using the background as a reference has been decisively exhausted; if anyone else has any ideas I would love to hear them.

[3gMike]

4 hours ago, Philalethes said:

Great information, exactly the type of more in-depth knowledge about camera technology I suggested would be useful to know here, even more so when it's based on first-hand experience; also a very poignant example showing the effect clearly. I still find it interesting how some of the ones in the Mastcam imagery looks very similar to diffraction spikes, extending outwards and seemingly beyond one pixel (almost like it's "spilling over" into the nearby pixels), which definitely played a role in fooling me. The vertical lines are also interesting, I'm not sure to what extent the phenomenon you just described also covers these, but if you know more about it I'd love to hear it.

And yeah, the point about the processing and filtering that would have to be done is a good one that I thought a bit about, it would be unlikely that they'd do something like that for a camera that, as Aten said, is meant to take photos of rocks and dirt. The imagery from the site is also supposedly raw, which I assume would preclude compositing.

Hopefully the next time there's a big spot visible they'll snap some images on consecutive days so we can figure out the orientation, or maybe NASA could possibly calculate it from the rover and camera's position and orientation and make it clear. At least I don't see any other way now that using the background as a reference has been decisively exhausted; if anyone else has any ideas I would love to hear them.

I've been checking to see what sensors are used on Mastcam. Some interesting data is available here  https://mastcamz.asu.edu/cameras/tech-specs/

I found it particularly interesting that the left and right cameras are treated differently, which could possibly explain why you are seeing different artefacts in different images.

I agree with Sam that these seem to be single pixel 'traps' where charge is held due to damage from radiation. The vertical lines look like transfer smear.

Whilst it may be possible to image stars in daylight, just before sunset, with the camera pointing away from the Sun, it is unlikely that any of the spots in these images could be stars due to the limited dynamic range of the sensor. If you look at the specs for the sensor you can see that Full-well capacity is around 25,000 electrons, with dark noise around 27 electrons. The image is digitised to 11 bits giving a dynamic range of 2048. Making a comparison between brightness of Sun to that of the brightest star -Sirius- (as seen from Earth)we find a dynamic range of 10^10 would be required. So it seems clear that we cannot be seeing stars in these images.

[hamateur 1953]

Great link @3gMike  

[Philalethes]

12 hours ago, 3gMike said:

I've been checking to see what sensors are used on Mastcam. Some interesting data is available here  https://mastcamz.asu.edu/cameras/tech-specs/

I found it particularly interesting that the left and right cameras are treated differently, which could possibly explain why you are seeing different artefacts in different images.

I agree with Sam that these seem to be single pixel 'traps' where charge is held due to damage from radiation. The vertical lines look like transfer smear.

Whilst it may be possible to image stars in daylight, just before sunset, with the camera pointing away from the Sun, it is unlikely that any of the spots in these images could be stars due to the limited dynamic range of the sensor. If you look at the specs for the sensor you can see that Full-well capacity is around 25,000 electrons, with dark noise around 27 electrons. The image is digitised to 11 bits giving a dynamic range of 2048. Making a comparison between brightness of Sun to that of the brightest star -Sirius- (as seen from Earth)we find a dynamic range of 10^10 would be required. So it seems clear that we cannot be seeing stars in these images.

Checking the data sheet is certainly never a bad idea! And yeah, I was about to suggest the two different cameras as a possible explanation for why only some of the images have the same pattern of pixels, but I haven't gone through and checked if that's the case.

I'm still a bit curious as to what the explanation for the extension of what I thought would only be single pixels in the case of the type of artifact we're talking about, i.e. why they don't seem confined to a single pixel. Cropping out one of them it looks like this:

That's 32x32, and zooming in to see it more clearly, here is a resized version: 

This is what I initially suspected was diffraction spikes, as it definitely does resemble that. I'm curious as to what causes this; if the images are really raw, then I would assume that precludes e.g. any smoothing that would smear out a single pixel, and that this is part of the type of artifact being described. Would definitely like to understand how that works. Also of interest is how the right and left spikes seem to have a faint red shimmer at the ends, while the top and bottom ones have a faint blue shimmer instead. If someone knows, please explain!

As for the point about the dynamic range, I'm not entirely sure if it makes sense to think about it that way, but maybe I just don't understand camera technology well enough (or optics, heh). If I'm not mistaken at least the dynamic range refers to how many different values can be assumed between completely black and completely white, and doesn't necessarily refer to the maximum difference in brightness of two objects can be registered. So even if a certain number of pixels are totally saturated by an extremely bright source, that doesn't necessarily preclude other pixels from not being saturated by that same source at all (e.g. in the case of zero atmosphere, although on Mars the atmosphere is thin, but that's besides the point), and thus able to register much fainter sources of light.

In other words I would assume you could still, if you were to track the sky extremely carefully, expose an image for long enough and have the additional light of the stars register at their respective positions on the sensor even with direct sunlight present within the image (I also assume you'd need special technology not to burn out your sensor from the extremely bright light there). You'd of course end up with a resulting image in which the difference in brightness between the two is at most the dynamic range you have rather than the actual difference in brightness (which in this case would be a billion times greater), but the way I see it you could still potentially capture both in the same image anyway. At least that's how I imagine one could possibly do it; I'm certainly no longer suggesting that's the case here, as I've realized by now that that would be totally unfeasible. Yet another point for those who have a good grasp on camera technology to address if they feel impelled!

In any case it's definitely interesting to delve more into how imaging technology in general works, even if it sadly apparently in this case can't be used to give us information about exactly when sunspots seen from Mars will be visible from Earth.

Edited August 26, 2023 by Philalethes
typo

[3gMike]

19 hours ago, Philalethes said:

Also of interest is how the right and left spikes seem to have a faint red shimmer at the ends, while the top and bottom ones have a faint blue shimmer instead.

That is interesting - the appearance of a central green with reds to left and right and blues to top and bottom is consistent with the configuration of adjacent pixels in the standard Bayer filter arrangement, but how that relates to this 32 x 32 pixel image is more difficult to understand. Very odd!

 

19 hours ago, Philalethes said:

So even if a certain number of pixels are totally saturated by an extremely bright source, that doesn't necessarily preclude other pixels from not being saturated by that same source at all (e.g. in the case of zero atmosphere, although on Mars the atmosphere is thin, but that's besides the point), and thus able to register much fainter sources of light

Agreed, but the image of the Sun is not saturated in this case, so even Sirius would be below dark noise level.

[Philalethes]

42 minutes ago, 3gMike said:

That is interesting - the appearance of a central green with reds to left and right and blues to top and bottom is consistent with the configuration of adjacent pixels in the standard Bayer filter arrangement, but how that relates to this 32 x 32 pixel image is more difficult to understand. Very odd!

That's definitely very interesting, I see exactly what you mean when looking at that arrangement. I don't know much about how exactly that would work here either (or how it works in general), but given the similarity it's not a stretch to think that it must be involved somehow. In the data sheet you provided earlier it's confirmed that the camera does indeed use that for its filter, and there's even an in-depth article about the filter of the camera here, which also explicitly shows that configuration. It does make sense that it must be some physical filter that's doing it, at least given the basic assumption that the images being "raw" means no processing has been done on them. 

Also, I realized that the resizing tool I'd used had done some unwanted processing to smooth out the result, here is the image upscaled preserving the individual pixels, for anyone interested:

51 minutes ago, 3gMike said:

Agreed, but the image of the Sun is not saturated in this case, so even Sirius would be below dark noise level.

Oh yeah, for sure, you certainly wouldn't see any detail on the disc itself in that case, it'd of course be oversatured to the brim, and you'd necessarily have to composite different images with different amounts of exposure to get anything like that (which it's clear by now has not been done here, and the camera probably wouldn't be able to capture anything like that no matter what either I would guess).

[Sapphire828]

Updated gif: https://giphy.com/gifs/Lqlm9nzouRwODlbAJu/fullscreen
There's a shift downward of the solar disk from Sol 888 to 889 and the big sunspots are still visible.
The picture taken on Sol 890 was taken earlier in the Martian day and the disk seems to be rotated with the sunspots at the top of the disk.
We should have seen it by now...too bad there are multiple days of sun pictures missing (Sol 891 through present) right when it presumably decayed.

There is also an interesting red "hot pixel" on the solar disk in the last picture Sol 890.

[Philalethes]

59 minutes ago, Sapphire828 said:

Updated gif: https://giphy.com/gifs/Lqlm9nzouRwODlbAJu/fullscreen
There's a shift downward of the solar disk from Sol 888 to 889 and the big sunspots are still visible.
The picture taken on Sol 890 was taken earlier in the Martian day and the disk seems to be rotated with the sunspots at the top of the disk.
We should have seen it by now...too bad there are multiple days of sun pictures missing (Sol 891 through present) right when it presumably decayed.

There is also an interesting red "hot pixel" on the solar disk in the last picture Sol 890.

In hindsight I think Aten's initial suspicion might have been correct, and that it was actually 3415 we were seeing, with the equator near vertical as they suggested; that would actually check out fairly well if I'm not mistaken (but clearly I make mistakes all over the place, so don't take my word for it).

[arjemma]

On 8/24/2023 at 10:02 PM, Philalethes said:

I still don't think they're correct, and I do still believe they are stars based on what I'm seeing. There is a somewhat green tint to the light of the "whiter" stars, but that is most likely because the camera is correctly registering the fact that "white" stars are emitting slightly more green light than of other frequencies; it also explains why the green tint is fainter than the red and blue hues of the other stars. I do agree that the vertical lines are likely artifacts, but they appear to be artifacts stemming from the light of the stars, as you can make out faint lines running down from most of them if you look closely; you also see diffraction spikes on many of the stars, another telltale light-based artifact. I'm certainly no expert on camera technology either, but they definitely don't look like dead pixels at all to me, but rather exactly as I'd expect light sources to look like. Yet another sign is that two of them appear to be covered as they are passed by, and another one is revealed from beyond the disc; this is difficult to explain if they really are just somehow dead pixels, as you can make out that it is indeed the case if you look very closely. As you suggest it would also be an idea to look at other images, but I do not see any trace of any of those artifacts in any of the other images I looked at from the past week or so, only in the images of the sunspots where the same (presumed) light sources are present.

So personally I'm rather confident about the opposite at this point, i.e. that they really are stars, but I could definitely be wrong. The above is simply my reasoning for why I believe that to be the case.

It should also be noted that if we can assume that the rover didn't move at all during this time and that the image was taken from the exact same position and in the same orientation, then you can use the exact same reasoning to determine the approximation to the ecliptic regardless, as all you really need is the path of the movement between the two images relative to the orientation of the surface. I don't know if that is a reasonable assumption or not, but my first guess would be that it probably is, and that they likely kept the rover still and the camera positioned in the same way for the consecutive shots over the hour or so it took them. If they really are stars we're seeing then that's of course the case indeed, but it's rather if they're not that it could potentially still be a fair assumption.

And yeah, sadly it did look from the imagery tniickck posted that it had been decaying, but I guess it's hard to say for sure with farside imagery. Presumably we'll soon get an actual view of it so we can check out what it really looks like.

PS:

Here's the source of the two images in question for anyone who wants to check for themselves and see what they think: this is the first image from 12:50:30Z and this is the second from 13:36:51Z, both from August 20, 2023.

I am not a camera expert either but I know a thing or two about photo editing. If there were dead pixels then those pixels would be dead on all photos taken with the same camera during the same time span. I have downloaded some images and have compared them on pixel level. Those pixels aren't dead on all photos and therefore it's not logical that they somehow are only dead on the photos of the sun. From what I have seen when I have compared the photos I would say that those are stars. I can't tell for sure though and I'm not 100%. This is just my evaluation on the raw photos that are available.

EDIT!
I have now found the pixel on three other photos so maybe they are artifacts after all? Very hard to tell.

Edited September 3, 2023 by arjemma