New Horizons at Io |
New Horizons at Io |
Feb 24 2007, 07:53 PM
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#101
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Senior Member Group: Moderator Posts: 3233 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
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. -------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Mar 15 2007, 09:10 PM
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#102
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Senior Member Group: Moderator Posts: 3233 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
Two more image sequences are down: ISunMon3 and Ihiresir4 (the 75-ms exposure image was released as a press release earlier, see the above posts).
The ISunMon3 image doesn't cover too much more additional terrain, with poorer resolution, than the first image returned and discussed on page 1 of this thread. So I won't cover this set, other than to say that the Tvashtar plume is visible and some surface changes are apparent at Zal, including an apparent plume ring that may confirm Zal as the location of the fainter of the three plumes seen in the recent press release image. I've attached the shorter of the three exposures taken during Ihiresir4 and annotated some interesting features. In this image you can make features along a sliver of the trailing hemisphere. No obvious surface changes are apparent, but I direct your attention to the feature I label as "Reactivated flow". Now looking at Galileo images, an inactive flow is visible. But as we have seen at Thor and now Shango Patera, just because an old flow was there before doesn't mean there wasn't a surface change. The source of this flow is a small patera located at around 29 South, 232 West. This patera is surrounded by thin, digitate flows radiating out from the source. One of these flows runs to the northeast of this small patera, and at around 70 km from the vent, greatly expands, forming the flow I marked as "Reactivated flow". Now it does look like it darkened since the Galileo era, BUT given the high phase angle, I am reluctant to go completely with that conclusion. I think more low-phase images, hopefully coming soon will show whether this flow reactivated since Galileo. -------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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