Juno PDS data Options

[Brian Swift]

Mike, were the MTF images collected during thermovac saved? (I didn't see them cataloged in the calibration report). And do you recall if the test patterns covered most of the camera field of view?

Unrelated, has there been much analysis of the PJ10 lightning search images? When I took a look, they seemed like mostly spot noise. I guess I was expecting to see see stars with the long TDI. Thanks.

[mcaplinger]

Mike, were the MTF images collected during thermovac saved? (I didn't see them cataloged in the calibration report). And do you recall if the test patterns covered most of the camera field of view?

Yes, they were saved, and no, the test patterns don't cover much of the field of view.

[Brian Swift]

Yes, they were saved, and no, the test patterns don't cover much of the field of view.

Thanks for the super quick response. No plumb-lines there.

[mcaplinger]

Unrelated, has there been much analysis of the PJ10 lightning search images?

I took a casual look when they came down. There are a large number of particle hits in these images; I see a few things that could be stars but they don't jump out as such and that wasn't what we were trying to accomplish (of course, I didn't see any lightning either but it's a long shot given the short exposure times.) There's more work to do with these images if anyone is interested.

[Gerald]

One of the questions, I've been interested in, has been: Is JunoCam able to discern Jupiter in Io shine? The answer is: Yes, it is!
Here a stretched raw, with bright Io at the right and Jupiter at the left side:


During the next years, we may see much of Jupiter's night side. So, one question will be, whether we can persue at least some of the largest storm systems even on the night side under Io shine.
Of course, detecting aurora or lightnings, or even some faint moons would be interesting, too. Another goal would be using JunoCam as a radiation flux detector on the basis of night shots.

[mcaplinger]

One of the questions, I've been interested in, has been: Is JunoCam able to discern Jupiter in Io shine? The answer is: Yes, it is!

Prove it, by plotting the expected geometric limb of the planet on this image. I think this is much more likely to be a stray light artifact.

[Gerald]

Far from anything I'd call a proof, but a first plausibility cross-check:


The first row are maps of cosines of emission angles with a HFOV of 60 degrees, and a vertical FOV of 60 degrees (vertically) centered to Jupiter.
The second row consists of according enhanced renditions derived from JunoCam raws, without trajectory nor shape model, and cropped arbitrarily.

[fredk]

Ioshine or light scattered along Jupiter's atmosphere from the daylit side? Or skyglow? Earth's night atmosphere is fairly bright due to skyglow. How bright would you expect Ioshine to be?

[Gerald]

With Io's radius of about 1820 km, I get a cross section of about 10.4e6 km². With Io's distance from Jupiter of about 420,000 km, I get a surface of a hemisphere of that radius of about 1.1e12 km². The quotient of these two areas is about 1e5.
Assuming 4000 DN for Jupiter's solar-illuminated surface with TDI 3, we should get theoretical 80,000 DN for TDI 60, such that we should be on the same order of magnitude as one DN for Io shine. Io's albedo is pretty high with about 0.63. Some binning/blurring over the noise (which I obtained by blurring an enhanced intermediately processed image) should result in a detectable signal similar to the one presumably observed.

[mcaplinger]

Far from anything I'd call a proof, but a first plausibility cross-check...

Well, maybe. There are clearly a whole lot of stray light artifacts in later images as the sunlit limb comes into the FOV (see image 10, for example) -- you can see hints of this in your version of image 6.

I wasn't expecting so many radiation artifacts in these images, but honestly we only took them because we had nothing else to take with the planet out of the FOV.

[Gerald]

I've seen the stray light in the later images - and intentionally omitted those. Then, it isn't clear, whether Jupiter's night side can't be resolved in images after #06, because of the stray light, or because Io is in Jupiter's shadow, or otherwise out of reach.
But the essential question will be, whether we'll find a way to take Jupiter images during the next solar conjunction(s), when we'll see mostly Jupiter's night side, and no Earth-based observation will be possible. If we can show, that stacked high-TDI night shots are able to resolve storm features, we could bridge some of the observational gap.
A stack of images will be suitable to remove most or all of the artifacts caused by energetic particle hits or hot pixels, and improve the signal strength.

[Brian Swift]

Anyone have suggestions on how I can determine the rotation (and tilt) of
the Junocam CCD relative to Juno spin axis?
I’m new to SPICE, but have played around with Frame Transformations
on WebGeocalc. Unfortunately, my linear algebra and geometry skills have gotten a little
rusty being underused for a few decades. Thanks.

[Gerald]

Out-of-the-hip, I can only say, that the deviation from orthonormality is small, and I'm not quite sure, whether the values are perfectly constant, since Juno's spin axis might undergo tiny changes. I've run several calibration series on Marble Movie images, and applied the results to images near these series, when highly accurate alignment was recommended. But for the alignment of close-up images, the deviation from orthonormality usually didn't play an obvious role. Errors induced by these inaccuracies are probably on a subpixel level.
I'm presuming, that the main source of residual misalignments in my processing is due to inaccuracies of my optical distortion model. I'm working on this question in small time slices between all the other event-driven activities. However, I don't rely on any of the published ik versions thus far. I think, that the Brownian approach is inherently unstable for wide angles, and I'm inclined to do the math for a different approach, maybe together with an article, if successful. I also cannot entirely rule out some small chromatic aberration, or a tiny deviation of the CCD pixel grid from square.
Other possible causes for small misalignments might be deviations of Jupiter from its idealized IAU shape, small oscillations of Juno's solar panels, or a small varying torque-free precession of Juno's spin axis.
There are several degrees of freedom that may annihilate each other partially. So, it's not quite trivial to find out the actual physical settings with a high accuracy.

[mcaplinger]

Anyone have suggestions on how I can determine the rotation (and tilt) of
the Junocam CCD relative to Juno spin axis?

If you use SPICE, all of this is managed for you by the frames system. If you have a vector in the JUNO_JUNOCAM coordinate system (which is formed by the camera boresight and the CCD line and sample directions) and you want to transform it into some other system, either inertial or not, you can just call pxform to get a rotation matrix for a particular time, and then call mxv to transform a vector from one coordinate system to another.

The raw values for what these transforms consist of are in the "frames kernel" https://naif.jpl.nasa.gov/pub/naif/JUNO/ker.../fk/juno_v12.tf but all you need to do when using SPICE is load this kernel, and the software does the rest.

As Gerald says, these angles are pretty small, so for many purposes you can just assume that Junocam is perfectly pointed along the spacecraft's -X axis.

You don't need to understand mathematically how a rotation matrix or matrix-vector multiplication work to use SPICE effectively, although it doesn't hurt.

[Brian Swift]

Mike, Gerald - Thanks for the replies.

Rotation and tilt relative to the spin axis are two of the extrinsic parameters produced from my camera modeling process, and end up being adjustable parameters to my image formation pipeline. So, I was curious how much the spin axis has changed between the imagery used for camera modeling (2016026, 2016040, 2016130) and and Perijove imagery. Changing the rotation by 0.1 degree definitely has a noticeable effect on the assembled imagery.

Gerald - in addition to your misalignments candidates, one I’ve wondered about is the effect of onboard compression on imagery with high gradients. such as point sources (which I use to produce the camera model) and Jupiters limb (which I use to judge the alignment).

I also think there is a non-radially-symetric component to misalignment.
I’m currently capturing that in p1,p2 parameters of my brown model.