[X] My Assistant

[Gerald]

Did anyone happen to observe Jupiter immediately before 2018-07-16T03:47:30 plus light travel time, especially recording a video?
I'm not yet quite sure, But we might have had a small (double?) impact on the night side of Jupiter's north polar region.

Admittedly, it's hard to observe Jupiter's night side from Earth, but maybe there are preceding or follow-up observations, or there has been another presumed event on the dayside at the same time.

[Gerald]

#53, and #58:


Note, that several departure images are intentionally overexposed, in order to improve quality near the terminator, especially the polar region with the circumpolar cyclones.
One of the methane band images is unsharp, obviously due to motion blur, but on the other hand, it doesn't show the stray light issues with TDI enabled for long exposure time.

Here links to according draft versions, to enhanced reprojected PNG versions, and to a first run of map products.

[mcaplinger]

One of the methane band images is unsharp, obviously due to motion blur, but on the other hand, it doesn't show the stray light issues with TDI enabled for long exposure time.

We've concluded that the issues with the methane images are not stray light per se but are being caused by blooming of charge from the visible bands migrating up into the CH4 region more than we had expected from ground testing.

We tried a couple of things: just turning the TDI off and letting the image blur alongspin (which works but obviously the images are very blurry) and moving the CH4 readout region as far as possible from the visible bands (which showed some modest improvement but isn't a panacea.) The latter will affect the geometric information in a way not currently captured in the instrument metadata. You can expect some similar tests in future perijoves.

[Gerald]

We've concluded that the issues with the methane images are ... being caused by blooming ...

Did you consider to replace TDI 64 CH4 images by pairs of TDI 32 images? Blooming would be halved, and TDI would shift the saturated pixels by 32 rows less.
Of course, required storage would be doubled for the same number of collected photons.

Btw., in the meawhile, I've rendered
hipassed maps of PJ14, part 3,
highly resolved cylindrical maps of close-ups,
and drafts of the departure sequence.
Attempts to visualize short-term southern CPC motion are on an early state.
At least this preliminary 6-image animated gif should provide an idea of the motion, and of the type of the involved vortices. The upper left vortex in the GIF is the most southern CPC, approximately the center of an almost pentagonal cluster of six circumpolar cyclones, three of which are shown. Interestingly, a pretty large anticyclone made it into the gap between those three cyclones. Note, that the FFRs (folded filamentary regions) in the lower left are cyclonic, too, like usual. In the upper right, there is another anticyclone, but its rotation isn't well-resolved in this animation. Some of the apparent motion is due to residual global geometrical distortions. And on the raw pixel level, we probably have some aliasing, which might be confused with small-scale motion.

[mcaplinger]

Did you consider to replace TDI 64 CH4 images by pairs of TDI 32 images?

Even if everything was perfect (geometric registration, digitization, etc.) a pair of images of TDI N/2 would only improve the SNR by sqrt(2) relative to a single image of TDI N.

We did some tests with lower TDI several orbits ago and will likely repeat them with the new CCD readout region, but we don't have a good model for how much this will help, and it's obviously a tradeoff between blooming and SNR.

[Gerald]

...
We did some tests with lower TDI several orbits ago and will likely repeat them with the new CCD readout region, but we don't have a good model for how much this will help, and it's obviously a tradeoff between blooming and SNR.

Here is a combined and annotated image derived from #45 and #46, roughly adjusted to the CCD filter layout:

Rather obviously, for this southern MME sequence, the blue filter doesn't cause blooming by itself. But for TDI 64, it's sufficiently saturated to let run through excess electrons from underneath the green filter. Since the green filter is about half as sensitive as the blue filter, it shouldn't cause blooming for TDI 32. But red is a little more sensitive than green. So, it might cause some blooming. Blue could swallow the excess electrons from red, since it wouldn't be saturated.
S/N would be reduced by sqrt(0.5) for a single TDI 32 image, but a pair of TDI 32 images would have a combined S/N a little higher than a single TDI 64. It's mostly a matter of available storage. We'll find software solutions to align the lower TDI images.
It might even be possible to go a little bit above TDI 32 for southern MME, but for this, a more accurate model integration would be required, including the accurate extent of especially the red filter.
I'm presuming, that the electrons behave reasonable as they should for a CCD.
Without better ideas, I'd just suggest to test TDI 32 for southern MME, maybe together with a TDI 64, to be sure about the effect.