New Horizons at Io Options

[volcanopele]

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.


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.


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.


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.

[siravan]

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

[Exploitcorporati...]

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

[john_s]

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

John.

[Bjorn Jonsson]

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.

[JRehling]

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

John.

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.

[Exploitcorporati...]

Are those a couple on the terminator, too?



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

[john_s]

Nope, those are mountains on the terminator

[Bjorn Jonsson]

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.

[siravan]

Here is the plume image.

Attached thumbnail(s)

 

[volcanopele]

Note the double ring around Masubi!

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

[DEChengst]

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 ?

[Exploitcorporati...]

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.

[ugordan]

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.


Bjorn, we already know the time when the image was taken: 2007-02-26 08:40:04 UTC

[remcook]

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

[john_s]

Quick question for John about the lecture you'll be giving tomorrow:
Will it be recorded and put on the web ?

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.