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.

[elakdawalla]

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:

There was more excitement yesterday. We've been turning our Earthly (and near-Earthly) telescopes on the Jupiter system too, to give us the broader context for New Horizons' snapshot of the system. Yesterday Kandis Lea Jessup and I got our first look at the first Hubble pictures of Io, taken back on Valentine's Day (these were the images we had to scramble to redesign at the end of January, after the failure of Hubble's other camera). Io was only 16 pixels across in the pictures, but that was enough to show us something very interesting at ultraviolet wavelengths: there was a huge volcanic plume rising above the edge of Io's disk. We're not yet 100% sure which volcano is generating the plume, but I have a hunch that it's Tvashtar, a volcano that obliged Cassini by producing a similar-sized plume during Cassini's Jupiter flyby in late 2000. We've seen plumes like this in Hubble images before, but they aren't particularly common, so we are excited at the prospect of getting much closer images of this thing with New Horizons next week. In fact the New Horizons schedule includes a color image specifically to look at Tvashtar's plume, on the off-chance that there might be something there to see. We just need Tvashtar (or whatever volcano is actually responsible) to keep doing its stuff for one more week. Credit: John Spencer and Kandis Lea Jessup, Southwest Research Institute, and the Space Telescope Science Institute

--Emily