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TEGA - Round 2
Cargo Cult
post Jul 22 2008, 08:48 AM
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QUOTE (Solar Fan @ Jul 22 2008, 04:28 AM) *
It looks like they've successfully uttered the command "Open Sesame".

Previously, they'd been asking HAL to open the pod-bay doors - with predictably little success...

(Could this suggest that this whole side of doors may be operational? If so, second hooray!)

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Ken McLean
post Jul 23 2008, 10:58 AM
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QUOTE (Cargo Cult @ Jul 22 2008, 06:48 PM) *
(Could this suggest that this whole side of doors may be operational? If so, second hooray!)

IIRC, I believe the ovens on the ends were expected to be more likely to open fully because of the way the hinge mechanisms work. If that's true then it's more likely to suggest the other three end ovens will open too.
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centsworth_II
post Jul 23 2008, 03:07 PM
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QUOTE (Ken McLean @ Jul 23 2008, 06:58 AM) *
...it's more likely to suggest the other three end ovens will open too.

You mean the other two. The first oven opened was an end oven and one of its doors only partially opened, so it looks like we won't know exactly how each door will open until it's opened.
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BrianL
post Jul 23 2008, 05:07 PM
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My momma always said, "TEGA is like a box of chocolates. You never know what you're gonna get." smile.gif

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Skyrunner
post Jul 23 2008, 06:07 PM
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QUOTE (BrianL @ Jul 23 2008, 07:07 PM) *
My momma always said, "TEGA is like a box of chocolates. You never know what you're gonna get." smile.gif

Now lets hope she finds some shrimp

Could this whole side be opening fully instead of 'only' doors 0 and 3? They think they know which part is the problem but why could that part on this side of TEGA not be manufactured according to specs? I surely hope doors 1 and 2 work as well. Until we try there is no way of knowing. I guess they are first using the end ovens and perhaps try the other onces after that anyway.


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TheChemist
post Jul 23 2008, 09:25 PM
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Apologies, the wait is too long smile.gif
Attached thumbnail(s)
Attached Image
 
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Skyrunner
post Jul 25 2008, 08:13 AM
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Wow, thanks to Emily's Blog we now know more.

The part "not manufactured to a precise enough specification" is the "rail at the bottom". It tends to binds some doors while allowing others to open fine. While that sounds a bit sketchy to me it fuelers my hope that the other side of TEGA will be fine.

More from her blog:
QUOTE
Finally, Leslie cleared up something I've apparently been confused about for a while. The reason they're pressing toward getting an ice-rich sample for TEGA is because of concern about a possible short. This short is a "high-side" short that could affect the whole instrument. It is not the same as the short that affected oven 4; that one is "cleared," it can't possibly affect the operation of TEGA in the future.


So now we know this is another short. Not good news to hear, but on the positive side according to what Leslie Tamppari told Emily the team looking for a possible sol 60 rasp & deliver. The long wait is finally over, we just have to sit out this weekend.

Thanks Emily for that update!


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Deimos
post Jul 25 2008, 02:24 PM
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QUOTE (Skyrunner @ Jul 25 2008, 09:13 AM) *
So now we know this is another short.


No. We don't. What Emily reported is what has been discussed previously--the team is worried about a "possible" future short that could threaten all ovens. There is something unknown that caused one short (in TA 4). There are types of shorts that are local to the oven, like that one. As Emily said, there are high side shorts that affect the entire instrument. There is "no way to assess the probability of another short circuit" occurring, so prudence dictates knocking off the highest priority samples first (http://phoenix.lpl.arizona.edu/07_02_pr.php). Once there is another short, it may simply be too late to be prudent.
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Skyrunner
post Jul 25 2008, 06:17 PM
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QUOTE (Deimos @ Jul 25 2008, 04:24 PM) *
No. We don't. What Emily reported is what has been discussed previously--the team is worried about a "possible" future short that could threaten all ovens.

Misread that. I thought 'possible' meant they were note sure there is one as opposed to some new short occurring.


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jmjawors
post Jul 25 2008, 06:31 PM
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This does not clear up anything for me. Then again, I did not personally design nor do I operate the instrument so nothing is likely to make sense to me. biggrin.gif Just so long as the teams proceed cautiously, which they are, and do their absolute best to get some ice into that oven.

Have to admit though, those open doors sure were a beautiful sight.


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akuo
post Jul 25 2008, 11:42 PM
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Looks like they are finally going for it:
QUOTE
Scientists and engineers on the mission Friday prepared plans to send Phoenix later in the day that would command the robotic arm to rasp the hard soil in the trench informally named "Snow White," collect the shavings and deliver them to an oven for analysis.


It would be interesting to know more about the plan. Will the oven close immediately when its sensors confirm enough material has entered? If not, how will sublimation be avoided?


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bcory
post Jul 26 2008, 01:33 AM
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"NASA has tentatively scheduled a "mid-course" status report on the Phoenix mission July 31, when results of the latest TEGA run may be announced and new images released. The Phoenix team has asked for an extension of the nominal 92-sol (92 Earth-day) mission, and the outcome of that request may be revealed as well."

more:

http://www.aviationweek.com/aw/generic/sto...EXCITE07258.xml
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Aussie
post Jul 26 2008, 03:15 AM
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I have always been a little in awe of the expertise of the MER and Phoenix teams in trouble shooting and fault rectification at such a huge distance. But for Phoenix, to my mind they have lost the high ground with respect to design and QA and should be indulging in some navel gazing.

First the rail not manufactured to specification jeopardising a proportion of the TEGA capability. OK stuff happens and QA tests get missed, but surely not with an interplanetary lander.

Secondly, a short for oven 4 that is now '"cleared," it can't possibly affect the operation of TEGA in the future'. The cynic in me equates that to a fuse blowing. It can only happen once. But what was the inherent vulnerability that caused it in the first place?

And now a revelation that they have assessed the possibility of another short related failure mode that could have the effect of taking out the entire capability. Possibly the same cause and effect as the oven 4 short. We can only hope the probability of occurrence is low and the ice sample will be successfully tested.

Compliments to the team for identifying the possible failure mode. But that does beg the question as to why this wasn't identified before the mission. Easy to be wise in retrospect, but there does seem to have been a breakdown in their processes.
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01101001
post Jul 26 2008, 03:46 PM
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Sol 60 Raw Images

This looks like post-delivery, 0749 local time. There's a little soil on the adjacent TEGA door.
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fredk
post Jul 26 2008, 04:05 PM
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They certainly got some serious rasping done:
http://phoenix.lpl.arizona.edu/images/gallery/lg_16036.jpg
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