Juno Perijove 17, December 21, 2018 Options

[Sean]

PJ17_34-38


5 frame reprojection from Gerald

[GS_Brazil]

Full inline quote with large image removed- Admin

Great animation! These 9 frames cover how many hours?

[Sean]

start / end

PJ17_32: 17:24 UT

PJ17_40: 18:07 UT

[Sean]

PJ17_GRS animation


9 frames / 32-40

Made from Gerald's reprojected stack.

[Sean]

Detail from PJ17_34-38

[Sean]

PJ17_35 after Gerald...

[Bjorn Jonsson]

Two images showing details from PJ17_21. Compared to the original data this is enlarged by a factor of 3:



These are approximately true color/contrast images but the brightness of the haze and blue sky at the limb has been increased slightly relative to the brightest parts of the image (the contrast in the brightest areas is also slightly reduced as a result of this). The processing reveals that the amount of limb haze is variable.

[JRehling]

The GRS animation made me shiver. Wow. I'll be watching this again and again.

[Bjorn Jonsson]

The GRS animation is awesome, especially when one considers the oblique viewing angle of the original images.

But here are approximately true color/contrast and enhanced versions of image PJ17_27 ("PJ17 Equatorial Zone south"):





Juno's orbit is evolving and it's obvious from the PJ17 images that the viewing geometry is now significantly less favorable for imaging around the time of closest approach than it was earlier in the mission. The majority of the original PJ17_27 image data contains black space. If I understand correctly what's happening, this is going to get even less favorable but eventually things start getting better again (I suspect that may happen within a year but I haven't checked the SPICE reference trajectory yet).

[Kevin Gill]

Composite of JNCE_2018355_17C00038_V01 & JNCE_2018355_17C00040_V01, from the perspective/location of the former.

Been getting much better results since dropping my own renderer and using Blender.


Jupiter - Perijove 17

[Gerald]

Here is an intermediate breadcrumb of one of the topics I'm currently working on, that's analysing the dynamics of Jovian weather systems on the basis of JunoCam image pairs:

This is an excerpt of an analysis of pixel displacement fields, here applied to PJ17 Oval BA.
The upper left image is describing a steady vector potential, based on the two maps in the bottom row. This can be interpreted as the solenoid (divergence-free) component of a steady 2D-flow. The upper right is the amount of the first derivative of the vector potential, hence describes kind of a velocity. The other tiles try to visualize the vector potential and the derived velocity field.
Some disclaimers: I'm going to translate this into physically meaningful units. The velocity maps will look a little different after considering map distortions and proper scaling. So, be careful, when trying to interprete these intermediate products. The results are also subject to various systematic and statistical effects, which need to be specified and quantified for any scientifically meaningful interpretation. Nothing of this is substantially peer-reviewed. All errors are mine.
The answer to the frequently asked question of which software I'm using: A C++ compiler. Almost everything is proprietary and implemented from scratch on the basis of C-standard libraries like stdio.h or math.h. Runtime for the small example above was on the order of 100 CPU core hours. (I know, that GPUs exist. But I'm ready to write shader code only for simple algorithms.) For access to SPICE kernels, I'm saving s/c trajectory position data to text files using the NAIF/SPICE utility spy.exe.

[Xerxes]

(I know, that GPUs exist. But I'm ready to write shader code only for simple algorithms.)

Shader code? I'm afraid your conception of GPU programming is about 15 years out of date! CUDA is an ideal match for this kind of work, and even something simple like OpenMP might do well. I highly recommend that you check it out.

[Gerald]

Thanks! I'll consider CUDA or something similar for some portions of the upcoming tasks. GPU code might make sense in some cases, multithreading doesn't. I can easily load the CPUs of a given number of computers with 100% by just starting an arbitrary number of parallel processes, if I like. The above analysis is based on 300 runs distributed over the CPU cores available for the job.

[Kevin Gill]

Another composite of Perijove 17 images, this time using JNCE_2018355_17C00035_V01 & JNCE_2018355_17C00039_V01. Using the camera perspective of the former.

Lots of blending and color/contrast enhancement.


Jupiter - Perijove 17

[tanjent]

Is the great red spot really rotating noticeably in just the brief time interval of a fraction of a Perijove flyover?
I think it must be an artifact of the changing viewing angle, but Sean's GIF animation surely does give the appearance of turning a couple of degrees.