[X] My Assistant

[mcaplinger]

Some of the images have been posted on missionjuno.

You will immediately notice that there is something weird about them. Yes, we know about this, and I'll say more about it when I can. In the meantime, anything people can do to process them would be appreciated. I've had some success using https://github.com/chunglabmit/pystripe

[Antdoghalo]

As much as I'd like to see perhaps a social media post asking for suggestions, this may just lead to a needle in a haystack of noise.

[mcaplinger]

As much as I'd like to see perhaps a social media post asking for suggestions...

We did post an explicit invitation for new ways to process the data on missionjuno, see above.

I've said elsewhere that there are very few knobs we have to turn on the camera. We can't change, or even measure, any of the internal voltages. We could adjust the companding parameters and that's something we are considering. We can change the temperature of the camera, but it's much easier to make it hotter than colder, and in general hotter is worse.

[Gerald]

...We can change the temperature of the camera, but it's much easier to make it hotter than colder, and in general hotter is worse.

There is plenty of literature that says that radiation damage of semiconductors can be annealed by heating in at least some cases.

Two of several examples:
G. Kim et al. "A study of radiation damage and heat annealing effect on the irradiated 3T active pixel sensor"

The most well-known effect of the x-ray CIS due to the radiation damage are increments in the reset voltage and dark current. These effects cause the quality of image to degrade. To overcome these problems, many sensor recovery methods are studied. Annealing is the best method among many other methods. For the assembled sensor, the heat annealing is most suitable.

C. J. Marshall et al. "Hot Pixel Annealing Behavior in CCDs Irradiated at -83°C"

Hot pixel annealing began below -40 °C and the anneal process was largely completed by the time the detector reached +20°C.

How well this applies to the JunoCam electronics is mostly outside of my access.
All I can say is that the presumably radiation-induced reddening effect seems to have temporarily reversed a little bit after the chip was heated after, I think, PJ 49 or PJ50.
For some reason I thought that this heating option for annealing was also considered for JunoCam by design. But I don't find the according reference any more.
I'm aware of the experience that annealing will never be complete.

I think that in doubt it's easier to cope with the thermal dark current than with severe radiation damage in case the heating is maintained during the flyby. If it's properly calibrated and reliable, the companding function could be offset by almost the level of the dark current. I know that we would see a lot more hot pixels. But that's something more or less systematic and reprodicible.

[mcaplinger]

There is plenty of literature that says that radiation damage of semiconductors can be annealed by heating in at least some cases.

The Junocam team is well aware of annealing. One might look carefully at the dark current in the past few marble movies for evidence of heating going back several orbits. (Dancing around the limits of what I can say here.)

I think that in doubt it's easier to cope with the thermal dark current than with severe radiation damage in case the heating is maintained during the flyby. If it's properly calibrated and reliable, the companding function could be offset by almost the level of the dark current. I know that we would see a lot more hot pixels. But that's something more or less systematic and reprodicible.

As far as we can tell, this issue is not related to dark current, which is a more gaussian noise source. And there are some limits to the amount of offset that can be put into the standard companding function due to bit sizes of registers. The images are unusable with any degree of heating. If we could reduce the temperature below the level it's at with no heating, we would do that and we believe it would help, but that's not really possible (recall that Junocam is inside a thermal-blanketed volume with just the lens looking out, and by design it's a stable not-too-hot, not-too-cold temperature in there. There's no active cooling.)