NH at Jupiter, Planning the Jupiter encounter |
NH at Jupiter, Planning the Jupiter encounter |
Jan 22 2006, 10:57 PM
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Member Group: Members Posts: 706 Joined: 3-December 04 From: Boulder, Colorado, USA Member No.: 117 |
I think the Jupiter encounter deserves its own thread.
I've just been taking a first look at the Jupiter encounter geometry. You can do the same using Mark Showalter's excellent on-line ephemeris tools at the PDS rings node, which by good fortune happens to include a New Horizons ephemeris (calculated over a year ago) for our actual launch date, January 19th. We'll have an updated ephemeris soon, but this one's already good enough for planning. As Roby72 noted in the Star 48 thread, the satellites are (annoyingly) all on the opposite side of Jupiter at closest approach. We'll still get good views of all sides of Io because Io rotates in only 1.8 days and we'll be pretty close to Jupiter for that long. We'll get fairly good coverage on Europa too, for the same reason. But we won't get very close to Ganymede or Callisto. Luckily Io is our highest priority satellite target and Europa is next, so we'll do OK. |
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Feb 10 2006, 03:09 PM
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Member Group: Members Posts: 509 Joined: 2-July 05 From: Calgary, Alberta Member No.: 426 |
Geez, that's too bad.
This really serves to drive home the point that Jupiter's (Hill) sphere of influence is enormous. There are something like fifty of those "outer gravel" satellites known, and we won't be getting close to *any* of them? They're spread pretty thin. We're not completely dead yet, though. There's still a year to go before the Jupiter encounter. If we're really lucky, someone will find another one of those little buggers right close to New Horizons' path. Granted, this would pretty much take a miracle, but it's always possible. [Edit: We might have a bit more luck with a targeted search for Centaurs, though... could it be done?] |
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Feb 10 2006, 07:12 PM
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
QUOTE (Rob Pinnegar @ Feb 10 2006, 07:09 AM) Geez, that's too bad. This really serves to drive home the point that Jupiter's (Hill) sphere of influence is enormous. There are something like fifty of those "outer gravel" satellites known, and we won't be getting close to *any* of them? They're spread pretty thin. With orbital radii of about 12.5m km, we could think of it as a big circle with a diameter of 25m km that NH is passing through twice. It's actually quite unlikely that you'd come within 1m km of any of 50 of them -- this isn't bad luck, it's the way this game is set up. Additionally, the satellites have common orbits (in various subgroups) so the probability of an equatorial flyby hitting one of their orbits is not modeled by 50 independent events. If a group crosses the jovian equatorial plane at what is currently Jupiter-leading or Jupiter trailing, then of course a close Jupiter flyby would have no chance of coming near any such body. Given enough random Jupiter flybys, we'll probably see the great majority (over 80-90%) fail to image any outer satellite, then maybe one such flyby will image two or three of them. Although the radial angle alone gives many many ways for an encounter NOT to happen! Imagine if instead of putting a deorbit module on HST, we instead moved it to a distant Jupiter orbit (2 or 3x Callisto's orbital radius at perijove) while it still had some life left. We'd get Galileolike coverage of the inner system all the time, and we would eventually get some great images of the outer satellites! Of course, HST weighs about 4.5 times as much as Galileo did... |
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