Juno Perijove 24, December 26, 2019 Options

[Sean]

Detail from PJ24_24


Detail from PJ24_23

[Brian Swift]

Animation of lens flare and Ganymede moving over CCD from PJ24_02.
Somewhat interesting to me is part of flare in lower left that gets brighter and dimmer, but doesn't change position through the spin.


At closest point in this sequence, Sun is about 2º degrees outside camera field of view.
If Sun were to be imaged by JunoCam it would only be about about 4 pixels across.
Images are displayed at realtime rate, but only cover half of a spin (the other half are just black space).

[fredk]

Somewhat interesting to me is part of flare in lower left that gets brighter and dimmer, but doesn't change position through the spin.

Dust on lens? Or a reflection of something fixed relative to the lens?

[mcaplinger]

Or a reflection of something fixed relative to the lens?

Could be a glint off the solar panels or something on the panel structure. The spacecraft was more or less spinning around the sun line at this time since it was so close to conjunction, so the illumination on the panels wouldn't have changed very much during the spin.

[Kevin Gill]

The first Southern Fisheye Composite.

JNCE_2019360_24C00042_V01
JNCE_2019360_24C00043_V01
JNCE_2019360_24C00044_V01
JNCE_2019360_24C00045_V01
JNCE_2019360_24C00046_V01

Rendered from the perspective of '43


Jupiter - Perijove 24 - Composite

[Brian Swift]

Mike, just curious, did telemetry show any increase in focal plane temp while Sun was so close to field of view?

Also, has much analysis been done on what effect imaging the Sun would have on the CCD?
Given the1/25th Sun brightness, and spin duty cycle, I could imagine having the Sun imaged on the CCD might not be fatal/damaging.

[mcaplinger]

Also, has much analysis been done on what effect imaging the Sun would have on the CCD?

Rather a lot. Even at 1 AU not enough energy lands on the CCD to damage it thermally. If you tried to image with the sun near the center of the detector, there is an electronic effect that could damage the sensor; see https://www.onsemi.com/pub/Collateral/AND9183-D.PDF for details. You may recall that there was an orbit with an unusual orientation that Junocam didn't image for, this was the reason.

I haven't looked at the temperature data but I don't expect anything significant.

[Brian Swift]

... there is an electronic effect that could damage the sensor; see https://www.onsemi.com/pub/Collateral/AND9183-D.PDF for details.

Thanks for the link. At the time I didn't understand how keeping the camera off would prevent damage.
It looks like the tech note came out post launch, so I wouldn't expect the system to have the shutter disable circuit.
Though it's not clear to me if the damage would occur if the shutter was only pulsed some duration after the Sun had moved off the sensor.

[Bjorn Jonsson]

This is an orthographic mosaic of images PJ24_23, PJ24_24 and PJ24_25 in approximately true color/contrast and enhanced versions:



The mosaic is centered on planetographic latitude 53 degrees north. North is up.

BTW I noticed a 'gap' in the PJ24 product IDs, there is an image number 38 and image 40 but it's as if 39 is missing. Is there an image PJ24_39 that still hasn't appeared at the Juno website?

[mcaplinger]

Is there an image PJ24_39 that still hasn't appeared at the Juno website?

We're keeping that one secret because of the big conspiracy, but you caught us.

Seriously, it still has a data gap that hasn't been filled in by DSN replays.

[nprev]

Possibly OT, but has any ongoing, permanent degradation (i.e hot pixels, etc.) due to radiation exposure been noted in the imager? Just curious.

[mcaplinger]

has any ongoing, permanent degradation (i.e hot pixels, etc.) due to radiation exposure been noted in the imager?

If you look very closely you can see a steady increase in warmish pixels, but nothing that affects imaging to any significant degree. At least that's what I would say, all of the images are available for anyone to examine -- we take a dedicated radiation monitoring image at the end of each pass to look for changes.

Certainly you can see a lot of transient particle hits in parts of the orbit, some orbits more than others.

As the orbit evolves the spacecraft will get more radiation dose per perijove, but so far so good.

[nprev]

Gotta say, it's performed spectacularly. Thanks, Mike.

[Bjorn Jonsson]

This is a time-lapse processed from five images (PJ24_13, 15, 17, 19 and 21):



These images were obtained over a period of 14 minutes. In effect they show a Jovian sunset from above.

The images have been reprojected to a polar map. The north pole is towards lower left and the prominent clouds at lower left are centered at planetographic latitude ~60 degrees north.

The original images have been heavily processed here. The contrast and color has not been enhanced (except for some changes in the dimly lit areas very close to the terminator) but the brightness has been greatly increased near the terminator. Some of the original images (especially the last two) are quite noisy and dark near the terminator and this results in some processing artifacts. Despite this, many interesting changes can be seen near the terminator as the sun sets, for example clouds that get more reddish and shadows that get darker and bigger.

A 'tweened' version is also available on Vimeo:

https://vimeo.com/389125877

[Gerald]

Regarding animations: Despite the increasingly challenging observational conditions, it's still (PJ24) possible to resolve the cloud motion in the south polar region:

Each of the two frames of the blink gif is a stack of four images.