Since the New Horizons Jupiter Encounter thread is already getting pretty long, I decided to create a thread dedicated to New Horizons' observations of the most interesting object in the solar system: Io. Info on upcoming observations comes from the jupiter_timeline_static.xls document john_s posted, and the preview images are from Celestia (note that each image is scaled so that the pixel scale is ~correct, and represents a smaller FOV than LORRI)

Today, February 24, New Horizons conducts three observations of Io with the LORRI camera as well some observations of Io's atmosphere with ALICE. These observations have the lowest phase angle for Io of the entire encounter. Phase angle continues to increase as NH approaches Jupiter and Io.

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The first observation, ISunMon1, shows Io's sub-Jovian hemisphere (Clat=5.5 S, Clon=340.2 W) from a distance of 7,856,307 km. The resolution with LORRI would be 38.8 km/pixel. Pele is on the limb at lower right and Masubi is on the limb at lower left. Ra Patera is near center.

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The second observation, ISunMon2, also shows Io's sub-Jovian hemisphere (Clat=5.5 S, Clon=15.1 W) from a distance of 7,575,510 km. The resolution with LORRI would be 37.5 km/pixel. The Tvashtar plume might be poking above the limb at upper left.

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The third observation, ISunMon3, shows Io's leading hemisphere (Clat=6.0 S, Clon=84.7 W) from a distance of 6,627,459 km. The resolution with LORRI would be 32.8 km/pixel. The Zamama plume might be visible just above center on the left limb.

It only gets better from here. Not sure how NH downlink works, but there is a DSN window right after the last Io observation, hopefully at least one frame from each observation will be returned. Maybe they can do the Huffman window right around where Io is... Tomorrow contains four more observations of Io, highlighting Pele and an eclipse.

Jason, in case you didn't see it, here's the brand new image of Io from Hubble that John posted on the blog yesterday:

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--Emily

Cool, certainly looks like it could be Tvashtar. Given the viewing geometry, there is a slightly better candidate in an unnamed patera at 61N, 143 W, but given that it was only seen as a hot spot once, Tvashtar would be the better candidate.

More Hubble images now down- the Tvashtar(?) plume continues to be active through at least February 22nd, so there's a good chance that it will be active during the flyby too. Hubble only sees the plume in the ultraviolet, so it's not a sure thing that we'll see it at longer wavelengths with New Horizons, but I think the chances are quite good, particularly after closest approach when high phase angles will make it more visible.

That's a good point. Given the phase angles of these early images, it maybe rather difficult to resolve most of the plumes on Io.

The only Io images we'll get down before the second week of March are ISunMon09, taken at 8:40 on 2/26, which will be sent down during the downlink immediately following on the 26th, and IHiRes05, taken at 11:00 on 2/28, which will come down during the downlink starting at 15:52 on 2/28. The limitation is as much the time needed to compress the images and prepare them for downlink, given how busy the spacecraft is, as the actual transmission time. Both will show the same hemisphere of Io, centered on longitude ~65, with Prometheus on the limb and Tvashtar also near the limb. I goofed slightly in selecting these two as our early downlink images, given their similar geometry, but there *were* a lot of constraints.

John.

Today, February 25, New Horizons conducts three monitoring observations of Io with the LORRI camera focusing on the trailing hemisphere, as well some observations of Io's atmosphere with ALICE and an observation of Io while it is in eclipse with the LORRI, ALICE, and RALPH instruments. As noted in the post above, these observations won't be returned until next month.

Please keep in mind that these are simulations of the LORRI frames from Celestia, not the LORRI frames themselves...

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The first observation, ISunMon5, shows Io's trailing hemisphere (Clat=3.0 S, Clon=225.4 W) from a distance of 5,276,976 km. The resolution with LORRI would be 26.1 km/pixel. Pele is visible at lower left and Prometheus is at center right. If Loki's plume(s) are active, then it *might* be visible at upper left.

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The second observation, ISunMon6, shows Io's trailing hemisphere (Clat=3.0 S, Clon=253.1 W) from a distance of 5,217,587 km. The resolution with LORRI would be 25.8 km/pixel. Pele is now just below center and Loki has rotated into view at upper left. Prometheus' plume might be visible at center right, though as noted in the above posts, this might not be the best viewing geometry for observing Io's plumes given LORRI's wavelength range.

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The third observation, ISunMon7, shows Io's trailing hemisphere (Clat=3.0 S, Clon=308.1 W) from a distance of 5,184,145 km. The resolution with LORRI would be 25.6 km/pixel. Pele is now visible at lower right. Loki is now visible near center. Not sure where Loki is in its geological clock, but the SNR of LORRI might be enough to allow one to see where the overturn front is in Loki Patera.

The final observation is Ieclipse1, an observation of Io in eclipse. RALPH will be active during the eclipse, allowing for an observation of Io's current volcanic activity. Loki should be easily visible in the LEISA images, depending again on where it is in its geological clock...

Thanks for the inside look at the downlink. As always, the NH team is making us feel like real insiders.

What's the likely turnaround for these images to make it onto the SOC page? I remember things like the MER landings and Deep Impact where the first download images were just popping in right there on NASA TV but also situations like Huygens where there was a lot of stitching and sifting.

And what can we expect from the downlink that just happened?

Incidentally, what sort of compression are you using?

<clink> Tvashtar still has that enormous ring.

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Woohoo, 2 new Io images!
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And an eruption! Is that Jupitershine illuminating Io's night side or an internal reflection?

A little experiment on you guys- we posted the images about 40 minutes ago and were wondering how long it would take someone to notice them and spot the plume! We'll be doing a proper press release image in a few hours.

John.

John seems to have a little too much time on his hands, wouldn't you say, gents?

Yeah, he'd better get that press release done before us guys scoop you!

Damn. Looks like two of them. Didn't notice Tvashtar popping off too!

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Edit...oopsie. My monitor washed out ugordon's pic. This is awesome.

Umm, where do you see the second plume?

Hi eveyone. This is my first post to UMSF. Here is my take on "plume finding" on Io.

I thought I saw one on the center limb. Didn't realize that the Tvashtar plume was clearly visible in your pic.

Good eyes, exploitcorporations! There is a very small plume on the center limb (around 9 o'clock)- that's Prometheus.

John.

That's spectacular and one can even easily discern the plume's umbrella-like shape. This is not a surprise because with extreme contrast enhancement plumes are visible in some of the low-phase Voyager 1 clear filter images of Io (for example C1636826.IMQ) despite Voyager 1's more primitive camera.

Makes me wonder what the Voyager 1 Jupiter encounter would have been like had the Internet and powerful computers been common back then and if the image release policy was MER/Cassini/NH-like. One thing is certain: The plumes would have been discovered *before* the Io flyby.

I see the small one at 9 o'clock, the large hazy one at 11 o'clock, and two small features around 2 o'clock which are either big mountains peeking over the limb or smaller forelit plumes.

Are those a couple on the terminator, too?

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edit...sorry, I keep getting out of sequence. kabooom.

Nope, those are mountains on the terminator

Knowing the viewing and lighting geometry or the *exact* time the image was obtained would be lovely - then I could make a hi-res computer rendering to check what these features near the terminator are...

EDIT: Didn't see John's reply (these are mountains) before I wrote this.

Here is the plume image.

Note the double ring around Masubi!

GREAT IMAGES, john_s!!!! This is such a good day, for other spacecraft images as well...

Great pics, thanks for putting them up so quickly. Hoping for more the coming days

Quick question for John about the lecture you'll be giving tomorrow:

Will it be recorded and put on the web ?

Those mountains look from the map like they might be part of the big complex to the east and northeast of Ukko Patera about 10W 40N.

Great catch on the 9 c'clock plume, Exploitcorporations! I wrote it off as scattered light/topography, but a little sharpening brings out the nebulosity of the feature nicely.
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Bjorn, we already know the time when the image was taken: 2007-02-26 08:40:04 UTC

sorry, but I have to add another wow! happy days

Apparently slooh.com will be trying to do something to broadcast it- they have a 7-day free trial membership.

And siravan's image was interesting, showing the plume in the short-exposure image- I hadn't noticed it in that frame, having concentrated on the long exposure frame. And ugordan's view of Prometheus is better than anything I'd come up with so far. Nice stuff!

John.

Looks like Prometheus shows up okay in the short exposure too, waaaay stretched:

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Too bad that doesn't look like a very good option. For the trial you need to get yourself the most expensive account and cancel within a week. That's something I don't really like, and wouldn't be an option for me anyway, as I don't have a creditcard.

If there's a way you could get me a videoclip of the lecture I'll put up a torrent to share it, and archive it on my webserver later. If that fails I also would be happy with just a sound recording and the slides of the lecture, so I can make a flash movie out off it to share with the world

I was too excited to notice .

Here is a shaded computer rendering showing the area visible in NH's photo in detail:
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And a diagram-like one:
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There's something that looks like mountains like the terminator as had been indicated by John.

Sorry I have been slacking off on the image previews. I've been sick the last couple of days and today has been extremely hectic at work!

I'll try to get the last two days work up tonight. Nice work everyone on these images that showed up this morning. I've only had a short amount of time to look at them unfortunately.

clink clink clink clink

Someone should subtract this image from the New Horizons image in photoshop to spot the biggest surface changes.

Wahoo! Great images everyone. You could have a NH pic of the day for the next few months as the rest of them stream down!

"Someone should subtract this image from the New Horizons image in photoshop to spot the biggest surface changes."

What, like this?

It's a good idea, but Io looks so different in different fliters that it's no use unless the filter matches exactly. However, this is a first look at the question.

A is the big plume deposit - that does look different between old and new images. B is a smaller but real change. There are lots of smaller changes, but they get messed up by the filter issues. Wait for the real data - then it will be possible to do something.

Phil

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I'm wondering if the big new streak pointing southwest in the lower right quadrant of the new photo is new, or if it just doesn't show up in the low-res chunk of the composite image that happens to be there.

Interesting ratio, Phil. Looks like something big happened at Shango Patera

Here's a processed image from both exposures, with color data from the rendered view. Hope this helps in identifying changes. At least is a nice new Io image!



Some changes are visible :-)

The map that Bjorn presents includes some Voyager data as well, so some of the changes seen between NH and this simulated view may actually be changes that occured between Galileo and Voyager. Check out this view from Galileo:

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Here is the aforementioned press release.

While trying to match Bjorn's rendered view to the LORRI image, I notice the right hand side (near the terminator) features are way off while the left hand side fits perfectly. It's as though at a single longitude someone ripped off the texture and misplaced it?

Yesterday, February 26, New Horizons conducts one monitoring observation with the LORRI camera focusing on the leading hemisphere, two "HiRes" observations with LORRI and RALPH instruments focusing on the leading and anti-Jovian hemisphere, as well some observations of Io's atmosphere with ALICE during a stellar occultation.

Please keep in mind that these are simulations of the LORRI frames from Celestia, not the LORRI frames themselves...with one exception

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The first observation, Iocc1, is a stellar occultation of Io's atmosphere using the ALICE instrument. LORRI will also get a single frame shows Io's leading/pro-Jovian hemisphere (Clat=6.6 S, Clon=35.1 W) from a distance of 4,546,235 km. The resolution with LORRI would be 22.5 km/pixel. The Tvashtar plume should be at its fullest extent at upper left since Tvashtar is right on the limb.

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The second observation, ISunMon9, shows Io's leading hemisphere (Clat=7.1 S, Clon=68.2 W) from a distance of 4,085,950 km. The resolution with LORRI would be 20.2 km/pixel. This observation is now on the ground so I don't think I need to discuss this much, but the Tvashtar and Prometheus plumes are visible along the bright limb, and volcanoes such as Lei Zi Fluctus and Masubi are highlighted.

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The third observation, Ihiresir1, marks the start of high resolution observations at Io. The observation consists of both LORRI and RALPH frames (to look at Io in color and to examine the current distribution of hot spots). It will show Io's leading hemisphere (Clat=8.6 S, Clon=145.7 W) from a distance of 3,065,158 km. The resolution with LORRI would be 15.2 km/pixel. Prometheus is now front and center from this viewpoint. If Pillan is active, its plume might be visible at left.

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The final observation, Ihires1, shows Io's anti-Jovian hemisphere Clat=8.6 S, Clon=145.7 W) from a distance of 2,880,909 km. The resolution with LORRI would be 14.2 km/pixel. The observation consists of both LORRI and RALPH frames (to look at Io in color and to examine the current distribution of hot spots). Prometheus has now rotated over to the right and Pele is now on the limb. *Maybe* its plume will be visible. The Tvashtar image above gives me hope.

"Io: Where the weather is also geology."

You can use that one.

I know. I just wanted to bring that up because I am sure someone will mention the change around Kanehekili, which was something we saw with Galileo.

Today, February 27, New Horizons conducts three, high-resolution mapping observations with LORRI and RALPH and an eclipse monitoring observation with LORRI, RALPH, and ALICE. The observations today focus on Io's anti-Jovian and trailing hemispheres.

Please keep in mind that these are simulations of the LORRI frames from Celestia, not the LORRI frames themselves...with one exception

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The first observation, Ihires2, shows Io's anti-Jovian hemisphere Clat=9.1 S, Clon=203.0 W) from a distance of 2,691,322 km. The resolution with LORRI would be 13.3 km/pixel. The observation consists of both LORRI and RALPH frames (to look at Io in color and to examine the current distribution of hot spots). Pele has now rotated into view at lower left. The Prometheus plume should be visible at the terminator.

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The second observation, Ihiresir2, shows Io's trailing hemisphere (Clat=8.9 S, Clon=238.2 W) from a distance of 2,645,200 km. The resolution with LORRI would be 13.1 km/pixel. Pele continues to be prominent in this observation, that includes compositional measurements from RALPH. How hot will Pele be in LEISA data? Will the Pele ring look different in MVIC data?

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The third observation, Ihires3, will show Io's trailing hemisphere (Clat=8.4 S, Clon=267.2 W) from a distance of 2,679,220 km. The resolution with LORRI would be 13.3 km/pixel.

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The final observation, Ieclipse3, shows Io's trailing hemisphere Clat=7.6 S, Clon=300.3 W) from a distance of 2,748,703 km. The resolution with LORRI would be 13.6 km/pixel.

Correct, I wanted the highest possible resolution rather than the most recent appearance so most of the Jupiter facing hemisphere is from Voyager data. IIRC Galileo was scheduled to image at least the right half of what's visible in the NH image at fairly high resolution (much higher than Voyager) very late in its mission but went into safe mode.


Hmm... a part of the right hand side was made from low-res Voyager data IIRC so there may be some positional inaccuracies but some of these differences seem to be due to surface changes between Voyager 1 and NH. I probably need to check my map - the Voyager USGS map I used as a reference when reverse engineering the viewing geometry of the Voyager images may also have been inaccurate (it was based on Voyager data only and also didn't make use of all of the useful Voyager images). No hi-res and useful map incorporating Galileo data was available to me back then but that situation has improved .

All I can say is WWW!!!!!!! (WOW WHATTA WEEK And thank goodness for the internet).

Io AND Titan ..... what a strange solar system we have met...... can't wait for the rest of New Horizon's data
............... cna't wait for Pluto/Charon...................

Craig