Ganymede Flyby - PJ34, June 7, 2021 Options

[volcanopele]

Now that we are a month out from the Ganymede encounter, I'm creating a special thread just for this encounter.

A few basic facts about the encounter:

The encounter takes place June 7, 2021 at 16:56:07.972 UTC at an altitude of 1042 km from Ganymede's surface. The central latitude and longitude of the close approach point is 23.58 N, 57.62 W. The inbound leg occurs over Ganymede's nightside while the outbound leg covers the dayside, allowing for imaging of Ganymede's leading and sub-Jovian hemispheres.




The best imaging opportunities occur after closest approach, with dayside imaging possible between +00:15 and +06:45 at distances between 1050 km and 5690 km above Ganymede's surface (though the first pass will be along the terminator and the last pass will only capture a bit of the bright limb). This allows for JunoCAM images with resolutions between 0.71 and 3.82 km. The best imaging opportunity in my opinion is centered at +01:45 when Juno is 1,515 km above Ganymede. This allows for imaging at around 1 km/pixel, doesn't cover the terminator or too much of the limb, and allows for detailed imaging of Perrine Regio and Tros crater, a prominent ray crater within Phrygia Sulcus. A Cosmographia screen shot of the center time for this pass is below.




I've updated my simulation video of the encounter, now making use of updated trajectory and now has real orientation information.

https://www.youtube.com/watch?v=H_UO3EFB6l0

[MarcF]

If I'm correct, the highest resolution pictures should be taken at low sun angle, so I expect spectacular scenes. Especially, we will be able to see details of the topography of Tros crater, one of the youngest craters on Ganymede. Can't wait.

[Brian Swift]

Mike, any chance you can share preliminary/(final?) junocam commanding parameters for Ganymede encounter?
I'm checking out my pipeline and would rather use your commands than make up my own.

Tangentially related... typically, when is the deadline for delivering commands for uplink to Juno for a perijove?

[TrappistPlanets]

Now that we are a month out from the Ganymede encounter, I'm creating a special thread just for this encounter.

A few basic facts about the encounter:

The encounter takes place June 7, 2021 at 16:56:07.972 UTC at an altitude of 1042 km from Ganymede's surface. The central latitude and longitude of the close approach point is 23.58 N, 57.62 W. The inbound leg occurs over Ganymede's nightside while the outbound leg covers the dayside, allowing for imaging of Ganymede's leading and sub-Jovian hemispheres.




The best imaging opportunities occur after closest approach, with dayside imaging possible between +00:15 and +06:45 at distances between 1050 km and 5690 km above Ganymede's surface (though the first pass will be along the terminator and the last pass will only capture a bit of the bright limb). This allows for JunoCAM images with resolutions between 0.71 and 3.82 km. The best imaging opportunity in my opinion is centered at +01:45 when Juno is 1,515 km above Ganymede. This allows for imaging at around 1 km/pixel, doesn't cover the terminator or too much of the limb, and allows for detailed imaging of Perrine Regio and Tros crater, a prominent ray crater within Phrygia Sulcus. A Cosmographia screen shot of the center time for this pass is below.




I've updated my simulation video of the encounter, now making use of updated trajectory and now has real orientation information.

https://www.youtube.com/watch?v=H_UO3EFB6l0

so will we get any new map coverage (like the poles)?
and will we get any good stereo DEMS from the encounter?
i want more complete ganymede DEMs then just tiny chunks

nice video


only if juno had a ganymede and europa lander, we could land something on those 2 moons like cassini and huygens, but juno's original mission was to study jupiter witch needs no landers because jupiter is a gas planet

we need landers to go on ganymede and europa some day

[Antdoghalo]

No to the pole coverage but yes to the color imagery and yes to improving resolution in some areas. It is likely stereo coverage will allow some DEM's to be made of this region eventually.

[TrappistPlanets]

No to the pole coverage but yes to the color imagery and yes to improving resolution in some areas. It is likely stereo coverage will allow some DEM's to be made of this region eventually.

wait juno can take stereo (3d) imagery, or do you need 2 different view of the same spot to make a stereo image for a DEM?
how reliable would the DEMS of that area of ganymede be that juno saw (according to the video simulation)?

the region that i am curious about elevation (perrine regio area) is in fact going to be clearly visible during the juno flyby (according to video)

[volcanopele]

The issue isn't coverage or even viewing angles, the issue will be resolution. The best resolution images will be at ~0.7 km/pixel, and some of the best images will be closer to 1–2 km/pixel. Whether there is enough topography for that scale to be useful is a good question.

[mcaplinger]

Mike, any chance you can share preliminary/(final?) junocam commanding parameters for Ganymede encounter?

Sorry, no, because of the way we command these the details go outside the boundaries of the Junocam team.

Jason's animation gives you a good flavor of the likely timing, but of course the spacecraft spin phasing cannot be predicted in advance with any accuracy. We are almost certainly not going to try any imaging of the nightside because of time and data volume constraints. In rough terms, imaging will start around 16:57:30 +/- 15s and continue at 1-minute cadence for a while (TBD just how long, Ganymede leaves the field by 17:03:30 or so anyway but there are other constraints.)

FWIW, the kernels on the public NAIF site are the same ones we use.

[JohnVV]

for those that do not have these bookmarked already

the public orbital kernels are here
ftp://naif.jpl.nasa.gov/pub/naif/JUNO/kernels/spk/
and the rotational kernels are here
ftp://naif.jpl.nasa.gov/pub/naif/JUNO/kernels/ck/

you will also need other kernels like the framing one and the leap-second to do any spice calculations
ftp://naif.jpl.nasa.gov/pub/naif/JUNO/kernels/fk/
ftp://naif.jpl.nasa.gov/pub/naif/JUNO/kernels/lsk/

[Brian Swift]

Sorry, no, because of the way we command these the details go outside the boundaries of the Junocam team.

Jason's animation gives you a good flavor of the likely timing, but of course the spacecraft spin phasing cannot be predicted in advance with any accuracy. We are almost certainly not going to try any imaging of the nightside because of time and data volume constraints. In rough terms, imaging will start around 16:57:30 +/- 15s and continue at 1-minute cadence for a while (TBD just how long, Ganymede leaves the field by 17:03:30 or so anyway but there are other constraints.)

FWIW, the kernels on the public NAIF site are the same ones we use.

Thanks Mike. I'm lazy. Didn't want to knock out an encounter planner if you already had the numbers available.

So, are you saying the plan is to collect a series of full spin images, with spin phasing hopefully known well enough to keep Ganymede off the start/end seam?

For Jupiter images, does flight software (realtime attitude) determine image start times?

Should we expect TDI=1?

I haven't run the numbers yet, do you know if motion blur is going to be particularly bad?

[mcaplinger]

So, are you saying the plan is to collect a series of full spin images...

That would not be possible, because it takes a lot longer than a spin to read out a full spin of data (over two minutes, in fact.)

One might assume that whatever magical process we used for, say, the PJ29 images of Ganymede (10 frames more or less centered on Ganymede) might be employed here in some form, but alas, I can't describe the details.

[Brian Swift]

... but alas, I can't describe the details.

Is this due to information being MSSS proprietary, or something that is going into a future publication, or ITAR spacecraft commanding concerns, or something else?

Can you comment on how INTERFRAME_DELAY is determined?

Also, do you know if there is going to be a post-Ganymede encounter press conference? And if there is, if "they" (the powers that be)
are considering holding back the raw images until after the press conference?

[mcaplinger]

Is this due to information being MSSS proprietary, or something that is going into a future publication, or ITAR spacecraft commanding concerns, or something else?

I've already said as much as I can for reasons I cite upthread. It's certainly neither of the first two.

Can you comment on how INTERFRAME_DELAY is determined?

It can be directly commanded or it can be computed onboard based on spacecraft attitude knowledge (this is described in the Junocam paper so I feel OK saying that.) It would be an interesting exercise to compare the actual attitude in the reconstructed C kernels to that in the predicted C kernels, as that would give you a sense of how well this is known in advance.

Also, do you know if there is going to be a post-Ganymede encounter press conference? And if there is...

If there is, no one has told me about it. https://en.wikipedia.org/wiki/Loaded_question

I will say that many people have done a lot of work over the past few months planning this sequence. It would have been less stressful to start with a more distant encounter, but we'll see how it goes.

[volcanopele]

It would have been less stressful to start with a more distant encounter, but we'll see how it goes.

Just think of this and the Europa flyby as dress rehearsals for the Io flybys

[Brian Swift]

Understood Mike. Thanks for the response. Checking on value of INTERFRAME_DELAY for past few perijoves, looks like it is almost always .370, so I just use that as a fixed value.

Here is a visualization of what I think the imaging opportunities are for the PJ34 Ganymede encounter.
It was produced by running a raw data test pattern image through my pipeline using metadata generated
based on the SPICE available 5/26. (Hopefully I don't have the wrong side of Ganymede illuminated or
something upside-down.) https://youtu.be/SzHtDbhAF7E

Table of timings for my data takes which include one frame of padding at beginning and end.

P34_9001 to P34_9005 are on dark side.
P34_9021 didn't produce any imagery on the target even though the encounter planner thinks it should see 7 degrees of the limb.

CODE

imageId START_TIME STOP_TIME duration totalFrames limbPoints terminatorPoints
P34_9001 2021-06-07T16:53:19.678 2021-06-07T16:53:25.968 6.29 17 92 0
P34_9002 2021-06-07T16:53:48.459 2021-06-07T16:53:56.599 8.14 22 143 0
P34_9003 2021-06-07T16:54:17.627 2021-06-07T16:54:27.247 9.62 26 185 0
P34_9004 2021-06-07T16:54:47.170 2021-06-07T16:54:57.530 10.36 28 207 0
P34_9005 2021-06-07T16:55:17.088 2021-06-07T16:55:27.448 10.36 28 218 0
P34_9006 2021-06-07T16:55:47.014 2021-06-07T16:55:57.374 10.36 28 240 21
P34_9007 2021-06-07T16:56:16.943 2021-06-07T16:56:26.933 9.99 27 233 99
P34_9008 2021-06-07T16:56:47.252 2021-06-07T16:56:56.872 9.62 26 216 102
P34_9009 2021-06-07T16:57:17.568 2021-06-07T16:57:26.448 8.88 24 212 105
P34_9010 2021-06-07T16:57:47.521 2021-06-07T16:57:56.401 8.88 24 254 61
P34_9011 2021-06-07T16:58:17.857 2021-06-07T16:58:26.367 8.51 23 271 27
P34_9012 2021-06-07T16:58:47.822 2021-06-07T16:58:55.962 8.14 22 250 8
P34_9013 2021-06-07T16:59:17.795 2021-06-07T16:59:25.935 8.14 22 237 0
P34_9014 2021-06-07T16:59:48.146 2021-06-07T16:59:55.546 7.4 20 215 0
P34_9015 2021-06-07T17:00:18.127 2021-06-07T17:00:25.527 7.4 20 205 0
P34_9016 2021-06-07T17:00:48.478 2021-06-07T17:00:55.138 6.66 18 182 0
P34_9017 2021-06-07T17:01:18.837 2021-06-07T17:01:25.127 6.29 17 167 0
P34_9018 2021-06-07T17:01:48.822 2021-06-07T17:01:54.742 5.92 16 145 0
P34_9019 2021-06-07T17:02:19.185 2021-06-07T17:02:24.365 5.18 14 111 0
P34_9020 2021-06-07T17:02:49.915 2021-06-07T17:02:53.985 4.07 11 83 0
P34_9021 2021-06-07T17:03:20.650 2021-06-07T17:03:23.240 2.59 7 25 0