NH at Jupiter, Planning the Jupiter encounter |
NH at Jupiter, Planning the Jupiter encounter |
Jan 22 2006, 10:57 PM
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#1
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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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Jan 26 2006, 07:26 AM
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#2
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Junior Member Group: Members Posts: 72 Joined: 22-December 05 Member No.: 616 |
So New Horizons will take images of the Gas giant Jupiter and some of its moons?
Wondered if the lenses on the cameras are closed afterwards as some kind of protection and opened before Pluto encounter? |
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Jan 26 2006, 06:09 PM
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#3
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Forum Contributor Group: Members Posts: 1374 Joined: 8-February 04 From: North East Florida, USA. Member No.: 11 |
I think the lens cover on LORRI is designed just to open, its better to have a bit of dust on the lens than having a lens cover stick in the closed position.
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Feb 6 2006, 05:17 AM
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#4
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Junior Member Group: Members Posts: 87 Joined: 19-June 05 Member No.: 415 |
QUOTE (MahFL @ Jan 26 2006, 12:09 PM) I think the lens cover on LORRI is designed just to open, its better to have a bit of dust on the lens than having a lens cover stick in the closed position. The doors on LORRI and Ralph both open with one-time, spring loaded mechanisms. These devices are well proven and have high reliability, as almost anything is better than having the door stick in the closed position, as you said. We will know for sure in a few months. Does anyone know when they plan to open the doors and take test images? |
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Feb 6 2006, 03:47 PM
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#5
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Member Group: Members Posts: 903 Joined: 30-January 05 Member No.: 162 |
QUOTE (Comga @ Feb 5 2006, 11:17 PM) The doors on LORRI and Ralph both open with one-time, spring loaded mechanisms. These devices are well proven and have high reliability, as almost anything is better than having the door stick in the closed position, as you said. We will know for sure in a few months. Does anyone know when they plan to open the doors and take test images? I am sure there is a good reason for not doing this, but I have always wondered why these ejectable lens covers aren't made of lexan. If they don't come off, camera would still work. Must be missin' sumpthin' ? |
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Feb 8 2006, 03:07 AM
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#6
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Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
QUOTE (tasp @ Feb 6 2006, 07:47 AM) I am sure there is a good reason for not doing this, but I have always wondered why these ejectable lens covers aren't made of lexan. Lexan isn't a good choice due to outgassing and optical quality. It's fairly hard to make a cover that doesn't screw up optical performance, especially for a fixed-focus system. That said, the Galileo SSI did have a transparent cover (I'm guessing it was glass). All of the systems I've worked on (MOC 1&2, THEMIS, CTX, MARCI 98&05) had no covers at all -- we were too mass-constrained. This post has been edited by mcaplinger: Feb 9 2006, 05:57 PM -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Feb 8 2006, 12:20 PM
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#7
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
QUOTE (mcaplinger @ Feb 7 2006, 10:07 PM) Lexan isn't a good choice due to outgassing and optical quality. It's fairly hard to make a cover that doesn't screw up optical performance, especially for a fixed-focus system. That said, the Galileo SSI did have a transparent cover (I'm guessing it was glass). All of the systems I've worked on (MOC 1&2, THEMIS, CTX, MARCI 98&05) had covers at all -- we were too mass-constrained. If only they had been as thoughtful with the antenna on Galileo. Could they have put Galileo into orbit around Europa? Or was the radiation just too much for the probe towards the end of its life? -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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Feb 8 2006, 12:34 PM
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
QUOTE (ljk4-1 @ Feb 8 2006, 01:20 PM) If only they had been as thoughtful with the antenna on Galileo. As someone already said, unfolfing HGAs were used numerous times before, with no difficulties unfolding. It was a proven concept. What got Galileo in the end was all that trucking around the country, waiting to be launched literally for years. QUOTE Could they have put Galileo into orbit around Europa? Or was the radiation just too much for the probe towards the end of its life? That's an even worse situation than trying to put Cassini into orbit around Titan. There's just too much delta-V needed for it to be anywhere near feasible. Galileo was "running on fumes" at the end of its life with practically no propellant left. It also wasn't really designed to stand up to prolonged heavy radiation doses a Europa orbit would guarantee so that scenario wouldn't work in real life. -------------------- |
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