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PFS issue on Venus Express, PFS scanner stuck in its closed position
Marz
post Mar 22 2006, 10:04 PM
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QUOTE (BruceMoomaw @ Mar 22 2006, 02:15 PM) *
Yeah, actually it was (although you'll note that I was actually sneering at US pretensions of superiority in that post, by doing a Merle Haggard imitation with a sarcastic snark at the end). My apologies. (Also, I thought Messenger was GRRRing at me, rather than at the damn PFS.)

I would imagine that solar cycling has as much chance of remedying this as anything, although it will be tricky to pull off.
If they can't correct this, it WILL be a pity to lose it -- PFS was the second most important instrument onboard. Yet again, moving parts prove to be the bane of space missions, and we have proof that it's better to err on the side of excess in designing the strength of actuators (whether motors or springs).



Dumb question, but is VIRTIS the primo instrument of VExpress? Are some mission objectives compromised if PFS remains stuck, or can VIRTIS still achieve the main science goals?

After Mars Express gave us the Great Boom Scare of '05, I wonder if some serious thought & money should be spent trying to make deploy-or-bust designs?
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djellison
post Mar 22 2006, 10:31 PM
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QUOTE (BruceMoomaw @ Mar 22 2006, 08:15 PM) *
.... Yet again....


BINGO - Alex now owes me $1 - we had a book going on how long it'd be smile.gif

He had 'increasingly obvious' for $2, and I had 'JAXA' for $3.

Good job you didnt mention the Discovery program, that would have emptied my wallet.

Doug
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Guest_BruceMoomaw_*
post Mar 23 2006, 01:34 AM
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Did I happen to mention the central relevance of this to the Discovery Program?
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GravityWaves
post Mar 23 2006, 02:21 PM
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QUOTE (Marz @ Mar 22 2006, 07:04 PM) *
After Mars Express gave us the Great Boom Scare of '05, I wonder if some serious thought & money should be spent trying to make deploy-or-bust designs?


more problems for Europe maybe they'll fix it ?... well at least Mars Express done great at Mars mars.gif
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tedstryk
post Mar 23 2006, 03:14 PM
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QUOTE (deglr6328 @ Mar 22 2006, 09:13 AM) *
I am only able to remember one instance where a stuck instrument cover was removed DURING the mission. The Viking Mars scoop cover that was shaken out over several days of back and forth motions of the motor controlling it. Are there more examples? All the others I can think of, Galileo HGA, Pioneer camera cover not popping off, Venera camera cover not popping off and some missions where solar panels fail to open, were never fixed....


The Venera incident was a bit different...the caps melted on!


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djellison
post Mar 23 2006, 03:29 PM
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For those that have not seen the BBC series 'The Planets' - a Venera scientists recalled the problem being described thus

Senior Engineer "I believe we have landed in something sticky and viscous"
Junior Engineer "Yes sir, in the sh**"

smile.gif

Doug
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The Messenger
post Mar 23 2006, 04:06 PM
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QUOTE (djellison @ Mar 22 2006, 03:31 PM) *
BINGO - Alex now owes me $1 - we had a book going on how long it'd be smile.gif

He had 'increasingly obvious' for $2, and I had 'JAXA' for $3.

Good job you didnt mention the Discovery program, that would have emptied my wallet.

Doug

You blokes will take a wager on anything! I Guess Bruce's predictability is a safe bet smile.gif

Most of the tasking in the building I work in is related to flight hardware predicability: We stress, we strain, we Eddy, ultrasound, Xray, thermal image for ply debonds and on and on. We do it in vacuum, at extreme temperatures. A chemist down-the-hall from me has even tested deployment in the 'vomit comet'. We do everything we can think of that will assure the hardware will perform the way we expect it to, where we expect it to.

What I am getting at, is I am sure they are doing these same things in Europe, and expecting the designs to work under any and all possible conditions. So why so many failures? We must not understand all the failure modes. I can't pull up the level of detail I think would be necessary for me to understand the deployment difficulties experienced by the Mars Express, and I cannot even begin to comment on whether or not the PFS problem is in any way related. But I get to wonder out-loud if the Venus Express engineers are completely on-top of the possible failure modes of the Mars probe, and if they addressed the issues.

We have a prospective of how tightly the different Huygens groups guard their data, not always sharing with each other. Did the Venus Express engineers have a detailed report on the Mar Express boom problem, and upon why Huygens channel A failed?
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djellison
post Mar 23 2006, 04:46 PM
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There is no commonality between the aparant failure of the PFS cover, and MARSIS or the Huygens problem. I know you like to think outside the box, but that's just wayyy waAYy outside it smile.gif

Doug
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hendric
post Mar 23 2006, 04:49 PM
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I've wondered if missions shouldn't start adding "engineering webcams", similar to the Hazcams on MER that are there to monitor deployments and moving parts on sciencecraft. It might not have helped Galileo, but then again knowing the exact configuration of the antenna might have allowed for some kind of partial recovery by simulating the antenna coverage pattern.


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Guest_AlexBlackwell_*
post Mar 23 2006, 04:56 PM
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QUOTE (hendric @ Mar 23 2006, 04:49 PM) *
I've wondered if missions shouldn't start adding "engineering webcams", similar to the Hazcams on MER that are there to monitor deployments and moving parts on sciencecraft. It might not have helped Galileo, but then again knowing the exact configuration of the antenna might have allowed for some kind of partial recovery by simulating the antenna coverage pattern.

In Galileo's case, while live imaging of the HGA deployment wasn't possible, I seem to recall that NIMS took an image of the spacecraft during cruise (I saw it in AW&ST) that gave a rough idea of the post-deployment antenna configuration. And analyses during cruise showed that the anomalous HGA deployment did not result in any usuable gain/side lobe patterns.


QUOTE (djellison @ Mar 23 2006, 04:46 PM) *
There is no commonality between the aparant failure of the PFS cover, and MARSIS or the Huygens problem. I know you like to think outside the box, but that's just wayyy waAYy outside it smile.gif

The only obvious commonality would be quality assurance inspections or pre-launch reviews but, as any U.S. scientist/engineer can tell you, even those can't catch everything.

This post has been edited by AlexBlackwell: Mar 23 2006, 05:24 PM
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ljk4-1
post Mar 23 2006, 05:23 PM
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QUOTE (hendric @ Mar 23 2006, 11:49 AM) *
I've wondered if missions shouldn't start adding "engineering webcams", similar to the Hazcams on MER that are there to monitor deployments and moving parts on sciencecraft. It might not have helped Galileo, but then again knowing the exact configuration of the antenna might have allowed for some kind of partial recovery by simulating the antenna coverage pattern.


In this era of miniaturization, would it be feasible to send along
a little repair robot or two to fix stuck wires, antenna, solar panels,
etc.? Or is that still just too expensive and science fictiony?

But some real robot repair tests have been made:

http://www.nasda.go.jp/press/1999/03/ets7_990319_e.html

And then there is this idea:

http://www.tsgc.utexas.edu/archive/fulltext/raptor.pdf

And this little guy:

http://www.firstscience.com/site/articles/droid.asp

Other relevant items:

http://arxiv.org/pdf/cs.RO/0601056

http://ranier.hq.nasa.gov/telerobotics_page/photos.html

Keeping on the theme of miniaturization, I think we should send out
groups of small probes to a target world, each with one or two
specific science tasks. If we lose a few, it is unfortunate, but does
not stop the overall mission. Multiple probes can cover more ground,
literally, and we won't have all our eggs in one basket.


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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."

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djellison
post Mar 23 2006, 05:30 PM
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Woudlnt it make more sense to simply spend the time, money, volume, mass and energy on making a more robust deployment mechanism in the first place? Anything dynamic and adaptable enough is going to be far far more complex than whatever mechanism it's sent to fix, and as a result, far more likely to fail that the mechanisms in question anyway smile.gif

Doug
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JRehling
post Mar 23 2006, 07:31 PM
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QUOTE (The Messenger @ Mar 23 2006, 08:06 AM) *
You blokes will take a wager on anything! I Guess Bruce's predictability is a safe bet smile.gif


The MoomawBot script I wrote in Perl was fed the text of this thread and called for a massive reduction of the manned space program. It also referred to conversations it had had with members of the Decadal Survey that can be seen as insightful and pivotal in changing their opinions.
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Guest_BruceMoomaw_*
post Mar 23 2006, 09:30 PM
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Well, you know, constant repetition is a very important tool in educating the slow...

By the way, I only got one chance to talk with members of the Solar System Decadal Survey -- during which, sure enough, one member thanked me for clearing up a misconception his subgroup had had (and printed in their first draft) about what New Horizons could do at Europa. (E-mail available on request.) See if any of YOU get invited to my Nobel Prize party.
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dvandorn
post Mar 24 2006, 12:47 AM
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QUOTE (BruceMoomaw @ Mar 23 2006, 03:30 PM) *
Well, you know, constant repetition is a very important tool in educating the slow...

True, to a point -- but the Big Lie theory of ideological control also calls for the repetition of the lie, over and over, until it's been heard and repeated so often that it's accepted without question...

Oh, and don't call those who legitimately disagree with you "slow" or "uneducated." Makes it sound more like you're pushing the Big Lie than it sounds like you're right.

-the other Doug


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