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Juno - Jupiter Orbiter
gndonald
post Sep 19 2006, 04:07 PM
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I find the current 'tussle' on the forum about this missions lack of Jupiter moon photography some what ironic, Pioneer 10/11 were essentially focused almost entirely on Jupiter to the exclusion of the satellites.

The same thing almost happened to Voyager, if the BBC documentary series 'The Planets', was accurate in its description of the 'one man' fight to have the moons included as imaging targets for Voyager.

Supposedly until the Io pictures came in the mission team was entirely composed of Atmospheric and Astrophysics specialists ready to unravel the mysteries of the Jovian atmosphere...

So in that sense this mission is a return to basics, a focus on the 'main show' namely Jupiter itself rather than what orbits around it.
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Guest_Analyst_*
post Sep 19 2006, 06:15 PM
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QUOTE (gndonald @ Sep 19 2006, 04:07 PM) *
The same thing almost happened to Voyager, if the BBC documentary series 'The Planets', was accurate in its description of the 'one man' fight to have the moons included as imaging targets for Voyager.

Supposedly until the Io pictures came in the mission team was entirely composed of Atmospheric and Astrophysics specialists ready to unravel the mysteries of the Jovian atmosphere...


Very early in the planning stage (about 1972/73) MJS 77 got cameras with Mariner 10 heritage. This has not been easy (budget etc.) and I guess this is the "dramatic fight" in The Planets. The moons have been a primary science target at least since then. JPL studied many trajectories and could only get close encounters with three moons at Jupiter. At Saturn, Titan has been a so high priority, Voyager 2 could be sent to it again if Voyager 1 failed.

As for Juno: Its not about images first, not even second. It's not a sexy mission imo, but we will learn at lot.

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tedstryk
post Sep 19 2006, 08:14 PM
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I know the images are not a priority, but there are two things I am hoping for from JunoCam. First, any serendipitous shot it can get of the four inner moons, since coverage from Galileo and Voyager is so limited and most of the moon oriented missions likely to be selected any time soon are not likely to get close to them. Secondly, a few decent Io images for temporal coverage with better resolution than we have from earth. Plus, especially if the cloud tops are in the background, these images would be great for PR.


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gndonald
post Sep 21 2006, 03:13 PM
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QUOTE (Analyst @ Sep 20 2006, 02:15 AM) *
Very early in the planning stage (about 1972/73) MJS 77 got cameras with Mariner 10 heritage. This has not been easy (budget etc.) and I guess this is the "dramatic fight" in The Planets. The moons have been a primary science target at least since then. JPL studied many trajectories and could only get close encounters with three moons at Jupiter. At Saturn, Titan has been a so high priority, Voyager 2 could be sent to it again if Voyager 1 failed.


I've watched the relevant episode again ('Terra Firma') and it's definitely implied that the argument was not about having cameras on Voyager, but about where they were going to be pointed when Voyager reached Jupiter.

QUOTE (Analyst @ Sep 20 2006, 02:15 AM) *
As for Juno: Its not about images first, not even second. It's not a sexy mission imo, but we will learn at lot.


You're absolutely right there, this is the sort of 'basic science' mission that needs to be carried out so that we can plan properly for the next major mission without any more incidents like dropping the atmosphere probe into the wrong region as happened with the Galileo's mission.

And its been a long time in coming, this sort of mission was first proposed by the designers of Pioneer 10/11, even before the first flyby of Jupiter. In that case they planned to use an 'up-rated' version of Pioneer 10/11 to carry out long term (2 yr) observations of Jupiter (or Saturn) during the late 70's/early 80's. In these craft as with Juno, particles and fields studies would have been the main objective while imaging would have taken the back seat, despite the replacement of the Imaging Photopolarimeter with a 'line scanning' imager which would have presumably produced better images.
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Mariner9
post Sep 21 2006, 05:11 PM
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I recall reading about that proposed orbiter. I vaguely remember Dr James Van Allen being one of the proponents of it.

Basically Galileo was a hybrid space vehicle in order to do both spining (which is better for the particles and fields instruments) and a stable (better for imaging) platform.

And after all the suffering involved in engineering it, a lot of those involved swore they would never try another dual-spin spacecraft again.

Cassini was supposed to be the "cheaper' vehicle... although it seems to me that at 3 billion dollars it ended up more expensive. Difficult to be sure, since Cassini was developed later and hence with inflated dollars compared to Galileo. Also, the antenna failure on Galileo introduced a lot of extra operations expenses, on a program that already was delayed several times, and redesigned a few times. I don't think I've ever seen a final tally on Galileo's costs, but I'm pretty sure it ultimately went over 2 Billion.
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Mariner9
post Sep 21 2006, 05:14 PM
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I think I was a little vague about the main point I was trying to make.

Basically there were two camps propsoing instrumentation for a Jupiter orbiter. One wanted a spinning design, the other a 3-axis stabalized.

Galileo was the "all in one" compromise vehicle that came out of that.
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Guest_Analyst_*
post Sep 21 2006, 06:18 PM
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QUOTE (gndonald @ Sep 21 2006, 03:13 PM) *
I've watched the relevant episode again ('Terra Firma') and it's definitely implied that the argument was not about having cameras on Voyager, but about where they were going to be pointed when Voyager reached Jupiter.


I have to be more specific. The cameras initially planned for MJS 77 were a simpler design than the ones finally flown (lower resolution, more noise etc.). It was because the moons were a high priority they switched to the best ones available (Mariner 10) in about the 1972/73 timeframe. So long before launch the interest in the moons forced some design changes.

This said, I am sure there have been long discussion about where to point the scan platform during the encounters, sometimes the planet scientist won, sometime the moon nerds.

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Roly
post Sep 24 2006, 12:26 PM
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Given Junocam's heritage from MSL's MARDI, I wonder how will it cope with the radiation environment around Jupiter; I seem to remember something about a giant tantalum block shield for SSI, though Juno's orbit is more benign than Galileo's, and it doesn't have to last very long.

For inner moons like Io and Europa, any estimates of the sort of resolution that might be expected, given the 15km per pixel officially provided for images of Jupiter's poles?
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Guest_vjkane2000_*
post Nov 2 2006, 03:39 PM
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Juno's camera has been quoted on their website as having a 15km resolution. Does anyone know at what distance that resolution occurs? Is it over the poles or a perijove?
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Lorne Ipsum
post Nov 3 2006, 12:18 AM
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QUOTE (vjkane2000 @ Nov 2 2006, 09:39 AM) *
Juno's camera has been quoted on their website as having a 15km resolution. Does anyone know at what distance that resolution occurs? Is it over the poles or a perijove?


Should be over the poles -- JunoCam's reason for existence (well, OK, aside from EPO value...) is for gathering polar mosaics. I don't think anybody's exactly sure (yet) whether or not JunoCam will even produce usable images at perijove, due to the radiation environment there.

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ugordan
post Nov 3 2006, 08:33 AM
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If the perijove is well inside Io's orbit, doesn't that mean much lower radiation fluxes? Also, flying over the poles you're basically above/below the main radiation belts, right?


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Guest_vjkane2000_*
post Nov 3 2006, 03:50 PM
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QUOTE (Lorne Ipsum @ Nov 2 2006, 04:18 PM) *
Should be over the poles -- JunoCam's reason for existence (well, OK, aside from EPO value...) is for gathering polar mosaics. I don't think anybody's exactly sure (yet) whether or not JunoCam will even produce usable images at perijove, due to the radiation environment there.

Lorne


I recall that the Galileo probe found that radiation dipped as it came very close to the planet. I don't remember if 'very close' was above or below Juno's perijove. Also 'dipped' is relative. It might still be quite high relative to what the camera can handle.

I would love to see detailed images of the clouds up close. Assuming the radiation can be tolerated, there are a couple of potential issues. First, the craft will be moving very quickly. I don't know if the spacecraft's spin will act as a partial counter or make the problem worse. Second, will the spacecraft nadir be on the lit side of the terminator. Even if it is, the illumination will still be fairly dark.

One suggestion that these problems can be overcome is that the proposed Italian IR instrument would take pictures during close approach. If it can do it, then there is hope for JunoCam.

Net out of all this, as much as I want to see a high resolution image of the those belts and zones, I'm not holding my breath.
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edstrick
post Nov 4 2006, 11:33 AM
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The Voyagers got considerable amounts of sampled high resolution imagery at up to some 20 or 15 km resolution <similar to Amalthea> Much of it was low contrast vaguely swirley diffuse cloud patterns with little visual "pull" to grab interest. I think little of it was in color but I don't know that. Certainly, little has ever been presented to the public, other than as archived images on the Voyager disks. I've sort of wondered what could be done with it... maybe superimpose it in synchronized wide angle shots.. I suspect some was mosaics or strips of imaging to sample Jupiter at high rez but I don't remember.
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Guest_vjkane2000_*
post Nov 4 2006, 08:49 PM
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QUOTE (edstrick @ Nov 4 2006, 03:33 AM) *
The Voyagers got considerable amounts of sampled high resolution imagery at up to some 20 or 15 km resolution <similar to Amalthea> Much of it was low contrast vaguely swirley diffuse cloud patterns with little visual "pull" to grab interest. I think little of it was in color but I don't know that. Certainly, little has ever been presented to the public, other than as archived images on the Voyager disks. I've sort of wondered what could be done with it... maybe superimpose it in synchronized wide angle shots.. I suspect some was mosaics or strips of imaging to sample Jupiter at high rez but I don't remember.


The attached Cassini image suggests that images along the terminator would tend be be washed out. However, the image was processed to highlight the brighter areas.

I've just always been struck by the beauty of cloud images from Earth orbit and hope that we could get something similar from King of Storms. But probably a wish to go ungranted.
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NMRguy
post Nov 10 2006, 09:28 AM
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As discussed above, imaging with JunoCam is a peripheral goal for the mission. But Juno will be the first Jupiter probe to be placed into a polar orbit, and we are beginning to see the advantages of this orbital inclination from Cassini (Monster Storm).

Does anyone know JunoCamís pointing direction and whether it will be able to ride along with any of the other instruments? The Juno team reports that primary science measurements are taken at Ī 3 hours from perijove for all science orbits. Furthermore, only two science modes (and thus pointing directions) are necessary for the entire primary mission. These include radiometry and gravity science.

Since the closest passes over Jupiterís polar regions are included in the primary science windows, will the team allow JunoCam to image the poles during the mission, or is this something they will focus on late in the game? Can we expect similarly informative and stunning Jupiter polar images from Juno as we will get from Cassini?
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