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New Horizon Cameras
Guest_vjkane2000_*
post Apr 22 2005, 03:57 AM
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I've been wondering what the focal lengths are for the two New Horizon cameras (Ralph and Lorri). Curious to know how much Alan et al. were able to squeeze into their weight budget.
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edstrick
post Sep 12 2005, 08:44 PM
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Bob Shaw: "... but it doesn't change the fact that nowadays the problems are known yet dumb mistakes keep getting made. "

AMEN.

I think it was a BAD mistake not to have a coarse focus adjustment on the deep impact camera.

A big "Uh... I thought we knew about this..." problem... Stardust had a massive problem with condensate from outgassed crud fogging the optics. The earth-flyby image of the moon was 90% fog and 10% image.... massively blurred. Repeated heating of the camera to degass the optics got most of it, but I'm not at all sure they ever did get all of it and the Wildt comet flyby pics I think are somewhat degraded by it. NEAR's optics were significantly fogged by hydrazine byproducts during the loss-of-control event at the first arrival burn attempt that nearly lost the mission (not the camera's fault), and Cassini has had significant fogging problems between Jupiter and Saturn that I think still has some residual that makes it impossible to search for low brightness outgassing plumes at Enceladus.

Fogged optics seem to be the other problem-of-the-decade, besides out of focus cameras.
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mcaplinger
post Sep 13 2005, 09:42 PM
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QUOTE (edstrick @ Sep 12 2005, 12:44 PM)
Bob Shaw:  "... but it doesn't change the fact that nowadays the problems are known yet dumb mistakes keep getting made. "

AMEN.

I think it was a BAD mistake not to have a coarse focus adjustment on the deep impact camera.


I don't know all the details of the DI story, but I don't think you guys are being completely fair here.
You might recall that in the "old days" cameras had all-metal structures and masses of over 50 kg. For example, the Cassini ISS mass is about 58 kg, fully 4x heavier than the MOC on MGS with its graphite-epoxy optical structure. But for that mass savings, you have to work with a much trickier material. To say that all of the problems are known at this point is not really accurate.

You can usually assume that with optics, even mistakes that seem dumb with 20:20 hindsight are fairly subtle and hard to avoid once you appreciate all the details.

As for focus adjustment; it may be nice to have, but it's heavy and complex and if it fails, you can easily be worse off than before. We studied this trade very carefully for MRO CTX and ended up with no focus adjustment, and we intend to do the same for our LRO instruments. The MOC has focus control heaters, by necessity, but they have only a fairly limited adjustment range. See Ravine, M. A., et al., Graphite-epoxy optical systems: lessons learned on the way to Mars, Proceedings of the SPIE, 5179, 311-322, 2003.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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Posts in this topic
- vjkane2000   New Horizon Cameras   Apr 22 2005, 03:57 AM
- - gpurcell   QUOTE (vjkane2000 @ Apr 22 2005, 03:57 AM)I...   Apr 22 2005, 07:14 PM
|- - Bob Shaw   The sad thing about the optical calibration issues...   Apr 22 2005, 08:07 PM
||- - hendric   QUOTE (Bob Shaw @ Apr 22 2005, 08:07 PM)The s...   Sep 12 2005, 08:39 AM
|- - aharris   QUOTE (gpurcell @ Apr 22 2005, 02:14 PM)And w...   Sep 8 2005, 03:42 AM
- - edstrick   The Mariner 4 images of Mars were badly degraded b...   Sep 12 2005, 09:13 AM
|- - tedstryk   QUOTE (edstrick @ Sep 12 2005, 09:13 AM)but:...   Sep 12 2005, 10:20 AM
|- - Bob Shaw   I take the point regarding the steep learning curv...   Sep 12 2005, 08:22 PM
- - edstrick   Bob Shaw: "... but it doesn't change the...   Sep 12 2005, 08:44 PM
|- - tedstryk   QUOTE (edstrick @ Sep 12 2005, 08:44 PM)Fogge...   Sep 12 2005, 10:06 PM
|- - mcaplinger   QUOTE (edstrick @ Sep 12 2005, 12:44 PM)Bob S...   Sep 13 2005, 09:42 PM
||- - Bob Shaw   QUOTE (mcaplinger @ Sep 13 2005, 10:42 PM)I d...   Sep 14 2005, 09:44 AM
||- - dvandorn   QUOTE (Bob Shaw @ Sep 14 2005, 04:44 AM)The f...   Sep 14 2005, 10:00 AM
|- - RNeuhaus   QUOTE (edstrick @ Sep 12 2005, 03:44 PM)...be...   Sep 14 2005, 08:40 PM
- - edstrick   The Deep Impact defocus problem has distinct simil...   Sep 14 2005, 09:58 AM
|- - tedstryk   QUOTE (edstrick @ Sep 14 2005, 09:58 AM)Sadly...   Sep 14 2005, 01:18 PM
- - edstrick   Anyway.... there's essentially no such thing a...   Sep 14 2005, 10:45 AM
- - djellison   I think the MRI, as with the impactor camera ( the...   Sep 14 2005, 01:23 PM
|- - um3k   QUOTE (djellison @ Sep 14 2005, 09:23 AM)I th...   Sep 14 2005, 03:34 PM
- - djellison   Oo - my bad, thought it was a straight copy. Perha...   Sep 14 2005, 03:47 PM
- - BruceMoomaw   I've heard nothing to suggest that they didn...   Sep 14 2005, 07:55 PM
|- - tedstryk   In addition, if they can get what appear to be col...   Sep 14 2005, 08:32 PM
- - BruceMoomaw   The article on Deep Impact imaging of geological f...   Sep 15 2005, 06:16 AM
- - djellison   Well - I saw a reasonable colour image at the BAA ...   Sep 15 2005, 07:11 AM
- - edstrick   Bruce Moomaw: ".... -- if, of course, there a...   Sep 15 2005, 08:02 AM
- - MarsInMyLifetime   At risk of reopening what appears to be a dead thr...   May 26 2015, 05:48 PM
|- - mcaplinger   QUOTE (MarsInMyLifetime @ May 26 2015, 10...   May 26 2015, 06:20 PM
||- - Xcalibrator   QUOTE (mcaplinger @ May 26 2015, 01:20 PM...   May 28 2015, 02:51 PM
|- - Gerald   QUOTE (MarsInMyLifetime @ May 26 2015, 07...   May 26 2015, 08:41 PM
|- - MarsInMyLifetime   Thanks, all. I had read this on p. 12 and somehow ...   May 27 2015, 07:52 PM
|- - MarsInMyLifetime   QUOTE (Gerald @ May 26 2015, 03:41 PM) An...   May 27 2015, 08:02 PM
- - Brian Swift   Just came across a 1/2021 (open access) paper that...   Jan 5 2022, 11:44 PM


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