New Horizons at Io |
New Horizons at Io |
Feb 24 2007, 07:53 PM
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Senior Member Group: Moderator Posts: 3242 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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Apr 8 2007, 08:11 AM
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Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
I keep wondering on the engineering "strategy" of building a mini-Hubble as an outer planets spacecraft.
By that, I don't mean s miniaturized hubble telescope, but a spacecaft that would be essentially a 1 meter or 1.5 meter telescope. Imagine a cassegranian (as a visual example, though we'd probably want all reflecting optics) telescope in a 1-axis fork-mount. The BASE of the mount would be the main spacecraft bus and the BIG X/Ka or whatever band antenna to Earth. ALL of the high power remote sensing instruments would be in bays behind the main mirror, like the instruments on Hubble, with the highest resolution camera at the center of the focal plane pickoff point. The vehicle's normal mode of operation would be Hubble-like... Instruments all pointing in one direction, but not necessarily overlapping fields of view (unless you can use dichroic mirrors to split (for example) visible and near-IR from thermal IR, etc and share the same fileld of view). The whole telescope could slew toward and away from the beam-angle of the antenna (usually toward the Earth) with one degree of freedom, while spacecraft rolls along the antenna-axis would take care of aximuth pointing. Use of big photon-grabbing light-bucket optics will give spectrometers a far better tradeoff on area resolution and spectral resolution and signal-to-noise ratio than with Voyager/Galileo/Cassini dedicated instruments, while the sheer diffraction limited resolution increase of the big optics will give the spacecraft the ability to leisurely do whole hemisphere high resolution (kilometer to 100 meter) mapping at 10 times the range of Galileo or Cassini, and permit a Cassini like mission to take frame-filling long range monitoring images instead of of the 50 to 100 pixel icy satellite images it can currently take. Small, secondary instruments, like Wide-Angle cameras or extreme-ultraviolet spectrometers can be mounted "parasitically" on the main telescope, like finder scopes on a Celestron or the like. My question is to what extent has mission designs like this been considered compared to the sorts of things we're flying now, with or without scan platforms, with or without near continual telemetry to Earth. What are the drawbacks to such a design, what are the advantages? |
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