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Unmanned Spaceflight.com _ Phoenix _ TEGA (Thermal Evolved Gas Analyzer)
Posted by: Zvezdichko May 31 2008, 06:48 PM
Hello,
According to the publication here:
http://www.space.com/missionlaunches/080530-phoenix-mission-update.html
The glitch seems to be a short circuit in a filament in a part of the instrument that ionizes the vapors before they are sent to the detector...
Does that mean that it's directly related to the DSC oven?
Posted by: rlorenz Jun 1 2008, 03:33 PM
According to the publication here:
http://www.space.com/missionlaunches/080530-phoenix-mission-update.html
The glitch seems to be a short circuit in a filament in a part of the instrument that ionizes the vapors before they are sent to the detector...
Does that mean that it's directly related to the DSC oven?
Doesnt sound like it. Remember each oven has its own heater and sense windings. This sounds like the filiament
to generate electrons to ionise the evolved gases before they pass into the quadrupole (i.e. part of the mass
spectrometer - the EGA part of TEGA)
Hopefully as the release says, they can get it up and running nonetheless. But even if the mass spec croaks
altogether there is a good chance of detecting water ice in the TA (thermal analyser, aka DSC - actually there
is a whole literature on how to run these things, whether it is a Differential Thermal Analyzer or a Differential
Scanning Calorimeter is largely an issue of software). Either way, you can detect the latent heat of melting
and evaporation.
Posted by: Skyrunner Jun 2 2008, 02:03 PM
As I understand it the part that has shorted out is one of the two carrier gas ionizers.
The ovens vaporize the soil samples; these vapors are carried by a neutral carrier gas to the mass spectrometer. But before the carrier gas is fed over the sample it is charged then accelerated. The ionizer is needed to charge the gas so it can be be accelerated (like in an ion engine). Luckily there are two coils so when one is malfunctioning the other may be used instead. It seems to me that the team has some confidence that this is the case and full functionality can be restored.
Posted by: rlorenz Jun 2 2008, 04:07 PM
The ovens vaporize the soil samples; these vapors are carried by a neutral carrier gas to the mass spectrometer. But before the carrier gas is fed over the sample it is charged then accelerated.
No. ionization occurs in the mass spec. The carrier gas is neutral - remember the baking in the
ovens must be done under 'pressure'.
Posted by: Skyrunner Jun 3 2008, 01:33 PM
Yeah, I should have known that. Next time I work with the gas chromatograph mass spectrometer we have at the faculty I shall pay more attention to the explanations of the lab technician. 
As hoped it is working with the backup ionizing filament now.
Posted by: climber Jun 3 2008, 09:19 PM
One TEGA image on sol 9 : http://phoenix.lpl.arizona.edu/images.php?gID=2662&cID=40
Looks like "something" is open now
Edit : labbeled Sol 9 but from sol 8
Posted by: mars loon Jun 3 2008, 09:23 PM
Looks like "something" is open now
At todays (June 3) telecon, Peter discussed this. One door is fully open. The other is visibly and "unexpectedly" not fully open. they are working on it.
ken
Posted by: BrianL Jun 3 2008, 11:22 PM
Are they planning to test all the doors to see if any more might have issues?
Brian
Posted by: bgarlick Jun 4 2008, 12:05 AM
Do the doors need to also be able to close for proper TEGA functioning?
If not, I imagine the doors could be forced fully open by using a corner of the scoop if need be...
Posted by: Airbag Jun 4 2008, 12:24 AM
I can't imagine so as then they would lose the ability to control what sample goes in what container - assuming the doors can not be closed again, or at least risking a door not being closed again.
Which brings up a point - can the TEGA doors also be closed again? The TEGA documentation I have read only mentions that the doors are solenoid operated, but does not say they are/can be closed prior to TEGA thermal analysis (which is not necessary since each oven seals itself).
Let's say the doors can close - but would the dirt that was not filtered through and vibrated off the screen not prevent them from doing so anyway?
But say they can not close - then could a misplaced clump of dirt not prevent the neighboring door from opening, if said clump of Mars' finest dirt was deposited along the hinges of two adjoining doors, especially if one of those doors was at a convenient angle for the dirt to slide down towards the hinge...?
Well, we'll see soon enough!
Airbag
Posted by: rlorenz Jun 4 2008, 01:16 AM
......
But say they can not close - then could a misplaced clump of dirt not prevent the neighboring door from opening, if said clump of Mars' finest dirt was deposited along the hinges of two adjoining doors, especially if one of those doors was at a convenient angle for the dirt to slide down towards the hinge...?
IIRC the doors are spring-loaded, and *released* by solenoid. No closure possible. (Opening is inhibited
by a memory-metal clutch thingy to prevent launch vibration popping it open)
Obviously, as you say, door closure is not needed for the analysis, as the oven seal takes care of isolating
the sample from the atmosphere.
As for dirt - it would need an awful lot of dirt to jam up an adjacent door. Getting enough sample is
considered more of a concern than getting too much.
Posted by: Sandro Jun 4 2008, 01:09 PM
Hi together
I just had an short idea on a possible fix for the not fully open door. Although they can operate with the door not fully open (as far as I understood) I think it could be possible to open the door with help of the robot arm.
The doors are spring loaded and if they would move the arm slightly from left to the right (on this picture http://phoenix.lpl.arizona.edu/images.php?gID=2662&cID=40 ) over the not fully open door, we could press the door again down and hope that after the pass of the arm the springs will push the door fully open.
What are your thoughts about that option?
Regards,
Sandro
Posted by: MahFL Jun 4 2008, 02:38 PM
I think the safest thing to do is just use the oven as it is, as they say the door is open enough.
Posted by: djellison Jun 4 2008, 03:03 PM
A thermal day-night cycle may well help it deploy further as well. But active intervention would be un-necessary
Doug
Posted by: bgarlick Jun 4 2008, 03:50 PM
The screen behind the TEGA doors looks very fine meshed and the soil looks very clumpy. I would not be surprised if they have a real hard
time getting any material through that screen. Is there a way for them to tell how much material is in the oven before closing the oven and starting the baking?
Posted by: nilstycho Jun 4 2008, 04:04 PM
Whenever something gets stuck on a spacecraft, the two options available seem to be (1) jiggle it and (2) heat it. I'm imagining a spacecraft with lots of little peizoelectric-cum-resisting pads that can just vibrate and heat lots of things all over the spacecraft. This is an evolution from an earlier plan whereby each orbiter would have a micro helperbot that was equipped with (1) a hammer. 
Posted by: MahFL Jun 4 2008, 04:54 PM
time getting any material through that screen. Is there a way for them to tell how much material is in the oven before closing the oven and starting the baking?
I think they would have thought about this before they launched it.........
.
Posted by: bgarlick Jun 4 2008, 05:18 PM
.Note that they did do a second dig-n-dump because they were caught off guard by how sticky/clumpy the first scoop was.
Maybe the soil's properties are not exactly what they were expecting...
Posted by: nprev Jun 4 2008, 05:33 PM
Or electrostatically clingy? Just a thought; water really is practically a mineral where Phoenix is.
Posted by: Airbag Jun 4 2008, 11:09 PM
I'm still kind of surprised that they did not use up one of the TEGA ovens for a "contingency" sample. On the Apollo missions that is pretty much the first thing they did on the first EVA of each mission - take a contingency sample of soil and rocks right outside the LEM, whatever was there. Then at least in case some emergency arises you have *some* samples.
If I were in charge I'd have dumped that very first scoop into a TEGA oven. Still have 7 ovens left, which is more than MECA can handle anyway, and what if the RA suddenly stops working...?
Airbag
Posted by: Tom Tamlyn Jun 4 2008, 11:54 PM
What a relative of mine, an engineer, likes to refer to as "the instrument of persuasion."
TTT
Posted by: JRehling Jun 5 2008, 12:43 AM
On the other hand, what if the first use of the RA were the event that made it fail and we did so retrieving an uninteresting sample instead of an interesting one. Risk is a complex thing.
Posted by: glennwsmith Jun 5 2008, 04:53 AM
I like Sandro's idea, after it has had time to open on its own.
Posted by: rlorenz Jun 5 2008, 01:55 PM
There is an actuator that vibrates the funnel to encourage material to flow down into the oven. You could think
of it as a hammer...
Posted by: centsworth_II Jun 5 2008, 03:00 PM
I wonder if that vibration extends to the screen, encouraging loosely clumped material to break up and fall through.
Posted by: Airbag Jun 5 2008, 05:02 PM
That may be, but from many reports it seems that it is the daily temperature variations that are the main source of unexpected component failures. So the longer you wait before doing something, the bigger the chance something will break.
Airbag
Posted by: rlorenz Jun 5 2008, 08:26 PM
Not in as quantitative a way as one would want (it isnt a ThermoGravimetric Analyser)
There is an LED/photodiode 'oven full indicator' that shows if soil has backed up in
the load pipe - typically because the oven is full (duh). Transient signals from that may
give an indication of stuff drizzling into the oven during loading before it gets full.
A minor role I have associated with the TEGA team (I worked on TEGA-1 on MPL) on
which I did some lab testing while still in Arizona is on seeing whether the photodiode
data can give a sample mass estimate.
ans : maybe.
(a post-hoc mass estimate can also be had from the DSC data which indicates the heat capacity of the
sample, but that is also somewhat sample-dependent)
Posted by: ollopa Jun 5 2008, 10:33 PM
Ironically, it is a "hammer" that appears to be causing the filament problem, and which could also be used as an "instrument of persuasion" in extremis.
There is a solenoid on the atmospheric gas inlet valve that gives a hefty kick when it opens and closes. The short-circuit apparently comes and goes with the operation of this valve. If the back-up filament were to fail, the fall-back would be to operate the inlet valve until the circuit closes on the primary unit and then leave it. Right now, I believe they're not operating the inlet valve - IIRC they are content to sample the atmosphere by opening the cell door, which is less optimal than venting through a small valve.
Posted by: Skyrunner Jun 6 2008, 08:12 AM
I was wondering the accuracy of the samples (on both TEGA and MECA). Obviously the payload engineers went through great lengths to make the instruments as accurate as possible. But what makes me wonder is the temperature gradient. The soil is much colder than the lander deck (and instruments). We now this from METs temperature sensors as well as engineering calculations. Small differences in temperature could (at least in theory) lead to out gassing in the sample so that immediately after the sample is scooped up it could start out gassing. After the sample is dumped in the instrument of choice (before closing its lid) or when the arm is above deck, it heats up even more, encouraging more out gassing. Yes, the out gassing shouldn't be that much but still....it make me wonder about the accuracy and the precautions taken.
Wasn't this a concern for Viking as well?
Posted by: volcanopele Jun 6 2008, 08:30 AM
Or as my old AP Physics teacher from high school would say, "If at first you don't succeed, use a hammer."
Posted by: Skyrunner Jun 6 2008, 08:40 AM
Or as the first tenet in mechanical engineering goes:
"If the brute force fails to work,
try using more of it"
Posted by: djellison Jun 6 2008, 09:20 AM
Mythbusters
"With enough lubrication, we can do anything"
Doug
Posted by: Littlebit Jun 6 2008, 05:18 PM
Soil sampling is rarely entirely representive. In the Martian polar climes, where there are radical swings in temperature and soil shifting due to growth and shrinkage of the polar cap, you would expect a dynamic stability - ultra light molecules are gone, water ammonia and such just below the surface will sublime, but not terribly quickly at these temperatures and pressures. The samples should be highly representative, maybe off a few percent in the most volatile chemicals found.
Posted by: ilbasso Jun 6 2008, 07:41 PM
"With enough lubrication, we can do anything"
Doug
Anybody remember the Firesign Theatre and Fudd's First Law of Opposition? "If you push something hard enough, it will fall over."
Posted by: mike Jun 7 2008, 07:51 AM
What about a flat plate resting long axes parallel to the eternally flat ground.. on the planet Flatia.. I suppose you could push it so hard it moves into space, at which point it will eventually fall onto something.. but it might fall onto an evil entity of some kind, like say an anti-happiness consortium
Posted by: Zvezdichko Jun 7 2008, 04:06 PM
http://phoenix.lpl.arizona.edu/06_07_pr.php - sample released, "but the instrument did not confirm that any of the sample passed through the screen."
Posted by: Harder Jun 7 2008, 05:05 PM
This first sample is "topsoil" where the 1 mm mesh screen can be expected to pass thru the finer material - or perhaps not, as we now seem to find out.
But to expect that ice-type matl scraped from deeper trenches will pass thru such a fine mesh screen seems completely impossible. I´m really flabbergasted to learn about the existence of this fine mesh screen today. Surely the design team has thought through the scenario of delivering ice and created a couple of bins without a screen? Take the test by getting a scoop of sorbet ice from your deepfreezer - the only way to get scraps of sorbet ice through any screen, no matter the mesh size, is by melting! But on Mars the sublimation will happen first.
Too pessimistric a view? I really, sincerely hope I overlook something here!
Posted by: ugordan Jun 7 2008, 05:14 PM
I was under the impression they're primarily interested in stuff potentially mixed in (dissolved?) in the ice, not ice per se. Even if ice sublimates away (and it only sublimates really fast when you have isolated small particles of ice, not loads of them), the other stuff will be left behind.
Posted by: Sunspot Jun 7 2008, 05:39 PM
Oh Dear, things don't seem to be going too well.
Posted by: 1101001 Jun 7 2008, 05:57 PM
How large to you expect the rasped ice particles to be?
http://www.lpi.usra.edu/meetings/lpsc2007/pdf/2008.pdf (PDF)
it is cutting them free. In a few seconds and in a single
operation, rasp systems cut away strong materials,
process them to sizes that are instrument-ingestible,
and capture them in a catch container.
[...]
Conclusions: Rasping with the current ISAD RASP
bit design can remove a significant fraction of H2O in
permafrost samples. This is on top of passive sublimation
that takes place as the sample is transferred to the
instruments to be analyzed.
But the fraction looked to be 10 to 30 percent depending on weather.
Posted by: Harder Jun 7 2008, 06:16 PM
Thanks for this info. It states that the rasp produces cuttings that are instrument-digestible. I can imagine that ice/permafrost as hard as stone will indeed be rasped into finer pieces which are immediately suitable to pass through the funnel of the TEGA. So why install a fine mesh screen in the first place, especialy since icy particles have some tendency to bind together and won´t pass at all thru a strainer just by the force of gravity?
Perhaps my misunderstanding is because icy particles/crystals on earth have some liquid water which creates these coagulation effects (like snow flakes) whereas on Mars liquid water is not forming at all. Even here there is a shadow of a doubt, due to the heat imparted by the rasp which might create temporary softening/melting of ice in rasp cuttings.
Posted by: bgarlick Jun 7 2008, 06:17 PM
time getting any material through that screen. Is there a way for them to tell how much material is in the oven before closing the oven and starting the baking?
Darn! It looks like my concern back on the 4th was not completely unfounded...
I wonder if they have the dexterity to use the RA scoop to manually 'smoosh' some of the soil through the TEGA screen, or at least press down on the soil on the screen with the scoop while the shakers are activated.
Posted by: brianc Jun 7 2008, 07:09 PM
I wonder if they have the dexterity to use the RA scoop to manually 'smoosh' some of the soil through the TEGA screen, or at least press down on the soil on the screen with the scoop while the shakers are activated.
A wee tap with the scoop on the end of the arm should do the trick. My wealth of DIY projects leaves with me with the conclusion that there are few jobs that can't be completed with the aid of a hammer and screwdriver and the scoop looks like the sort of thing I would use as a hammer, actually my dad (god rest his soul) may well have used the scoop edge as a screwdriver substitute, I seem to recall him using mother's cutlery as proxy-screwdrivers !
Posted by: MahFL Jun 7 2008, 07:22 PM
Oh oh, lots of head scratching at UA.
Posted by: Stu Jun 7 2008, 07:36 PM
Well, head-scratching is good, you know? Doesn't do to take success for granted, and Mars takes a perverse delight in making us work for the knowledge we gather there. This is just one more thing to work out, isn't it? This spacecraft has been tested to within an inch of its life, but they couldn't predict every possible problem. I'm sure they'll figure something out.
If all else fails, Phoenix's passenger can pat the dirt with a paw, after his heroic efforts http://www.stevethecat.com/images/mars/steverepair.jpg earlier in the mission... 
(No, seriously... packing a cat into a Faberge egg and ejecting it from Phoenix??... who thought that up? And where can I buy some of whatever they were on when they did? 
)
Posted by: belleraphon1 Jun 7 2008, 08:25 PM
Here is where litter box skills will come in handy. Yes, this may a job for Steve the Cat!!!!
Seriously.... I believe there were similar issues on Viking, and that team worked it through. I am sure this team can do the same.
Does anyone know if the scoop arm is capable of actually touching the TEGA ports? I am not sure if it can reach down that far.
Craig
Posted by: ngunn Jun 7 2008, 09:11 PM
Mars people please - I need some help with dismissing what is probably a daft idea. In the presence of salts it is possible for a wet soil to refuse to dry out completely; it just stays sticky. Is it possible for carbon dioxide ice to be saline, in the way that water ice can? Could that make it resist sublimation? For water, salt widens the gap between freezing and boiling, favouring the liquid state. Is it possible to imagine 'saline carbon dioxide' having a liquid phase on Mars, even transiently, that might make the soil sticky? I know. It's horrible. Shoot it down quickly please.
Posted by: deglr6328 Jun 7 2008, 09:45 PM
The liquid phase of CO2 is forbidden below 5 bar.
Posted by: ngunn Jun 7 2008, 10:03 PM
That's a very good start! But I need more to dismiss the idea entirely. We don't know what chemical games CO2 engages in when it is a constituent of the soil.
I suppose we also have to consider aqueous brines with excessively low melting points for the cause of the stickiness. Is there such a thing as a H2O:CO2:chloride brine?
Posted by: deglr6328 Jun 7 2008, 10:25 PM
Ionic salts are insoluble in liquid CO2 because it's non-polar and the solubility of CO2 in water at low pressure is insufficient to have an appreciable freezing point depression effect.
Posted by: helvick Jun 7 2008, 10:28 PM
Seltzer..
Posted by: elakdawalla Jun 7 2008, 10:34 PM
There's a very good reason: the business end of TEGA, the oven itself, is a tiny quartz vial only a millimeter in diameter. If they let anything bigger into the doors, it would block the opening of the oven, and you'd get no sample.
--Emily
Posted by: deglr6328 Jun 7 2008, 10:53 PM
Mightn't we expect the MARDI microphone to be used sooner than expected now for trobleshooting, ie. to listen for TEGA mesh vibration?
Posted by: Reed Jun 8 2008, 12:16 AM
Is there a diagram or detailed description of the layout of TEGA anywhere ? A quick google didn't turn up much beyond this page http://planetary.chem.tufts.edu/Phoenix/thermal_evolved_gas_analyzer.htm
Posted by: Aussie Jun 8 2008, 02:16 AM
I'm sure they will Stu. The MER team proved their innovation time and again. But Phoenix planners must have known that martian soil has clumping tendancies since Spirit took the close up on 18 January 2004. So they had a heads up and plenty of time to consider the implications of putting a fine mesh over the oven (although obviously that filter is required). With respect to rasped ice I would anticipate that they would have tested the theory in a Martian temperature/pressure simulated environment to make sure that the rasped ice didn't bond back together. They would have..wouldn't they?
Posted by: SickNick Jun 8 2008, 02:43 AM
Don't FORCE it, just use a bigger hammer...
Posted by: SickNick Jun 8 2008, 02:51 AM
The behaviour of CO2-H2O mixtures is well understood over a wide range of temperatures and pressures. At Earth-normal conditions, CO2 dissolves slightly in water to form carbonated beverages and acid volcanic/mineral water. Solubility is better at higher pressure and lower temperature. At low temperature, a joint ice (Clathrate) is formed. This can form at up to 10C (above the melting point of pure water). Again, pressure favours clathrate formation.
it is not clear wheter CO2 clathrates are stable at mars near-surface conditions, but there is almost certainly SOME clathrates in the pole caps (On earth, the polar ice contains small amounts of Nitrogen, oxygen, and CO2 clathrates because trapped gas in snow is not entirely expelled from recrystallised ice. On Earth it's a curiosity. On Mars, it *might* be important, or it might not. (If the poles had a substantial CO2 clathrate component, they could be trapping a significant fraction of a whole atmosphere's woth of CO2, for example.
Excess CO2 *can* exist as a liquid at depth, above 5.2 bars and below 30C. This is unproven, but fun to speculate on...
Posted by: dvandorn Jun 8 2008, 04:25 AM
But just remember -- when the only tool you have is a hammer, most everything begins looking like a nail...
-the other Doug
Posted by: deglr6328 Jun 8 2008, 05:48 AM
Excess CO2 *can* exist as a liquid at depth, above 5.2 bars and below 30C. This is unproven, but fun to speculate on...
=====================================
Nick Hoffman Mars Specialist
White Mars Research Unit
My heavens! It never ceases to amaze me the actual scientists and engineers who pop up on this site, it's fantastic. Though, I see that almost all of your posts were made 4 years ago Nick and so I have to ask; your 'no-liquid-water' "white Mars" liquid CO2 only theory, if it hasn't been well and truly demolished by the findings of the MER's over the past several years must be hanging by the thinnest, most gossamer thread imaginable. Are you prepared to abandon it as the evidence now appears to demand that you must?
Posted by: gallen_53 Jun 8 2008, 06:02 AM
An electrostatic clinging mechanism would be my guess as well.
I suggest that the guys at JPL smear a regolith sample flat on a metal surface of the vehicle and let it sun a bit. Then scrape it up and deposit it into the TEGA.
Another approach would be to scoop up some regolith, jiggle the sample, orient the scoop so the sample gets lots of sunlight, jiggle some more, repeat several times and then deposit the sample into the TEGA.
The trick is to encourage electrostatic discharge. Short wavelength UV reaches the Martian surface and that should accelerate electrostatic discharge if the sample is properly exposed.
Posted by: ngunn Jun 8 2008, 07:58 AM
Excellent replies from the chemists as I had hoped. I've no objection to the electrostatic-sticky explanation, but nevertheless I persist with the thought that there could be a damp-sticky component (possibly a seasonal transient one) in this soil. Abandoning foolhardy attempts to guess myself what that might possibly be I ask the experts again this wider question. Are there any plausible candidates?
Posted by: Tman Jun 8 2008, 09:03 AM
Could it be that the behavior of this sample is affected by the soil that was blown away (and probably melted too) when Phoenix landed?
Posted by: Aussie Jun 8 2008, 09:05 AM
But the dust deposited on the MER solar panels clumps? So perhaps the electrostatic explanation is not the answer. I think ngunn has asked an extremely valid question. Is there a cementation process here and if so what?
Posted by: SickNick Jun 8 2008, 09:18 AM
I don't think there is a "need" for an electrostatic clumping mechanism. The Mars soil is basically rock flour, and extremely fine gained powders (or powders with a fine component) are notorious for clumping. Perhaps it is caused by Van-der-Waals forces between exposed and damaged mineral surfaces in the very fine grains, but it is a genuine and relatively common behaviour. Wheat flour behaves just like this, even though it is compositionally very different.
How to deal with it? More difficult. A small mechanical pulveriser? A forced seive? None of these are built into the TEGA design. Maybe the soil sample can be pushed against the filter grid by the remote arm, but maybe that would just pack it worse?
Maybe the next sample can be dumped from higher up so that it gets more dispersed as it falls? SOme more dump-and-drop trials would be in order, I think. with careful photos of the clumping as the regolith falls/arrives.
maybe the sample needs to be smaller?
Time for some careful trial and error, and some practice with an appropriate physical simulant on Earth...
Posted by: Zvezdichko Jun 8 2008, 09:37 AM
Hello, I have a question which may sounds a bit silly, but anyway. At Uni we study that a soil is a substance which has three components: the mineral component (it's basically the underlying rock), the organic component (humus, peptones and so on), and gas component (CO2, nitrogen...). The Martian soil is obviously lacking the organic component (if Gas-Chromatograph aboard Vikings gave correct results). We are still waiting the results from the problematic TEGA which has some advances (slow heating etc). So why call it "soil"? In the Eastern block we call it just "grunt".
Posted by: djellison Jun 8 2008, 10:08 AM
Because that's the lazy thing to call it. Fines, regolith, whatever geologically accurate term you elect to use is fine - but 'common' english means that soil is the 'stuff' on the ground. It's a point that has been at some of the press confs.
Posted by: Zvezdichko Jun 8 2008, 10:38 AM
Once again, thank you, Doug. In the end MECA and TEGA may prove that the Martian soil is more Earth-like, with nearly neutral pH, organic material and normal concentration of salts.
Posted by: SickNick Jun 8 2008, 02:13 PM
let's see what it *does* prove, rather than pushing our own speculative agendas.
The important thing with planetary missions is to wait.
See all the data, and think what the hell it means. It's never what we expected, or imagined, or hoped. Sometimes a single image or data point is a breakthrough. other times it takes an accumulation of images and data to help us understand what's going on.
I'm itching for TEGA data. Let's all try to be patient while our good friends on the mission team work out how to get the data, despite any obstacles that may arise.
Posted by: Zvezdichko Jun 8 2008, 04:34 PM
I apologise to you then. This was my natural desire, my expectations, my heart is with that mission.
Posted by: glennwsmith Jun 8 2008, 06:39 PM
A tip o' the hat to bgarlick for his prediction, on June 4, re difficulty of getting material through the screen. Interesting, that much of the challenge of space exploration will involve what could be referred to as "fuzzy" engineering, ie, the problem of lunar dust. But the Phoenix team has a lot of options, and they will figure it out!
Posted by: Sputnik Jun 8 2008, 07:16 PM
Wouldn't a high frequency vibrator between the bottom of the receptacle and the oven itself be enough to shake some particles from the sample, into the oven?
Posted by: gallen_53 Jun 8 2008, 08:03 PM
That's the ticket! Just slowly pour it in from higher up. It'll be a bit messy but should do the trick.
Posted by: gallen_53 Jun 8 2008, 08:27 PM
Sushil Atreya (a professor at the University of Michigan) has written some papers about the accumulation of electrostatic charge on Martian dust. This publications list at http://www-personal.umich.edu/~atreya/s_publications.html by Prof. Atreya covers many diverse topics in planetary science, provides PDF links and is very interesting. I suspect Prof. Atreya would have predicted this clumping problem if anyone had bothered to ask him.
Posted by: JRehling Jun 9 2008, 12:28 AM
There was definitely some alteration of the surface -- the key answer would be, what is the displacement of native surface material as a function of distance from Ground Zero? We can make 3D micro-topo maps of the vicinity and, with the sound assumption that there was nothing special about the landing site before Phoenix dropped out of the sky, measure the local effect. It seems to be something like 6 cm of displacement at Ground Zero. The stain shown by MRO probably corresponds to the boundary of a VERY slight alteration of the surface (akin to dust devil tracks or less -- the backshell made a stain a significant fraction of the same size).
I suspect that the alteration where the arm dug first is on millimeter scales and moreover consisted largely of removal of dust rather than alteration of the stuff that's left.
By definition, the post-landing surface consists of the surface where the force of the engines was too weak to move any more material. So I think if the material's failing to fall through the only difference owing to the engines is that there might have been a VERY fine layer of dust that would have fallen through and was instead blown away. If this stuff that was collected had been powdery before, it would have blown away, too.
I highly doubt that the stuff here was melted by the rockets. It takes an awful lot of heat to get that cold of ice up to 0C and much more to melt it. The moment of landing was pretty quick, and exhaust would cool off incredibly fast in that environment.
Posted by: Sunspot Jun 9 2008, 07:21 AM
Has there been any update on the TEGA problem?
Posted by: akuo Jun 9 2008, 07:52 AM
http://twitter.com/MarsPhoenix says:
Posted by: Stu Jun 9 2008, 08:02 AM
Hey, Doug, if all else fails, they could always ask Lewis Hamilton to give Phoenix a gentle nudge...
Posted by: djellison Jun 9 2008, 10:32 AM
You think you're funny... you THINK you're funny.
Actually - that is kind of funny. Hamilton could nudge it one way, Rosberg the other
Posted by: akuo Jun 9 2008, 10:51 AM
A sol 14 image of TEGA has appeared. There is some shifting of soil over the next sample doors, at least:
http://phoenix.lpl.arizona.edu/images/gallery/lg_3567.jpg
Earlier image:
http://phoenix.lpl.arizona.edu/images/gallery/lg_3304.jpg
Edit: More images:
http://phoenix.lpl.arizona.edu/images/gallery/lg_3568.jpg
http://phoenix.lpl.arizona.edu/images/gallery/lg_3571.jpg
http://phoenix.lpl.arizona.edu/images/gallery/lg_3572.jpg
http://phoenix.lpl.arizona.edu/images/gallery/lg_3573.jpg
I'd be surprised if there wasn't a sample acquired now :-)
Posted by: jmknapp Jun 9 2008, 11:40 AM
The ice could sublimate though, right? Phoenix landed around 5pm local time so the temperature probably would have been near the max -30C.
A paper http://isis.ku.dk/kurser/blob.aspx?feltid=166862 states:
Arm will be used to obtain samples of sub-surface ice
and deliver these to analysis instruments. The process may take
several hours and there is a concern that, if the samples are not
treated appropriately, significant sublimation could take place.
Cloud physics modelling of sublimation from a single ice
particle suggests that the half-life of 1-mm-diameter particles,
even with no ventilation or solar radiation, would be less than
3 h, even at 223 K [-50C] and that smaller particles or warmer temperatures
would exacerbate the problem. Mars chamber experiments
with isolated particles freely exposed on a surface confirmed
this prediction. The procedure in Phoenix will however be to
collect a small pile of a mixture of ice chips and dust. We find
that the sublimation rate from this will be lower, especially if
the pile is a mix of ice and dust and can be kept cold and shaded.
...
(1) Single small ice particles, or loosely scattered particles are
liable to sublimate rapidly in the atmospheric conditions
anticipated during the Phoenix mission.
(2) When collected together in a pile, the sublimation rate appears
to depend primarily on surface area rather than total
mass. ...
(3) Temperature is THE critical parameter and ice samples collected
during the Phoenix mission must be kept as cold as
possible, and in the shade, while awaiting analysis.
(4) Mixtures of ice particles and dust sublimate less rapidly
than pure ice at the same temperature and in a similar container.
The lowest sublimation rates at temperatures near
−30 ◦C (CSIL, Run 14) occurred for mixtures of ice particles
with very fine dust.
(5) Actual sublimation rates on Mars may be significantly
larger in the presence of wind speeds that exceed a few meters
per second.
Posted by: MahFL Jun 9 2008, 01:09 PM
I am not convinced myself.
Also the next set of doors are well covered in dirt, as the first set did not open correctly with out anything ontop of them it does not bode well for the future. I wonder if the team had tested this situation out, I'd be astonished if they had not.
Posted by: ugordan Jun 9 2008, 01:16 PM
Hmmm... I wonder how much (if any) of the soil fell through the mesh as opposed to just consolidating and sliding downward along the mesh? It doesn't look like the soil level was depressed after the vibration, at least not noticeably. The images don't look very promising to me. Hopefully some of the smaller grains did manage to get through...
http://i108.photobucket.com/albums/n15/ugordan/vibration_2.gif
Posted by: MahFL Jun 9 2008, 01:39 PM
I still maintain they poured way too much soil onto that oven opening.
Posted by: Stu Jun 9 2008, 01:40 PM
I can't make out much "settling" or shifting either... fingers crossed that some small grains managed to sift out of the underlying crud...
I was very surprised to learn just how tiny these TEGA ovens actually are! There's a good YouTube clip http://www.youtube.com/watch?v=7RnhgjBcErs, and you can see the ovens at 6:23. Tiny!!
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Posted by: ugordan Jun 9 2008, 01:46 PM
On the brighter side, even if there was soil deposited into the oven, that small an amount wouldn't be readily obvious to the RAC. Fingers crossed.
Posted by: centsworth_II Jun 9 2008, 02:22 PM
I wonder why they started with the uppermost oven. If they had started at the bottom, excess dirt would fall away from the yet unused oven doors. As it is, if they continue from high to low, there will be quite a pile built up by the time they get to the lowest.
.... or, is the TEGA shuttered cover horizontal and only looks tilted in the image?
Posted by: djellison Jun 9 2008, 02:23 PM
The ovens are side by side, not one above the other. That oven is the same level as the other 3 on that side, and the four on this side.
Doug
Posted by: centsworth_II Jun 9 2008, 02:30 PM
Ah, now ugordan's movie makes sense to me!
(I forgot, the shape is like a gable roof.)
Posted by: djellison Jun 9 2008, 02:32 PM
Yeah - it's a very very expensive, but small, barn conversion
http://phoenix.lpl.arizona.edu/images/gallery/lg_99.jpg
Posted by: centsworth_II Jun 9 2008, 02:41 PM
It's funny seeing that salt shaker to the right in the image you link. For depositing test samples? I can't imagine the test bench doubles as a lunch room counter!
Posted by: tuvas Jun 9 2008, 03:03 PM
Poor TEGA... It just doesn't seem to be working quite as intended... I sure hope they can get all of the problems resolved...
Posted by: centsworth_II Jun 9 2008, 03:07 PM
I hope you're not saying this based on something you've heard about the second attempt to get sample into the oven.
Posted by: MahFL Jun 9 2008, 03:41 PM
http://phoenix.lpl.arizona.edu/images/gallery/lg_99.jpg
Hey did ya'll notice the salt shaker in that picture ?
Posted by: Stu Jun 9 2008, 03:49 PM
Oh surely not. I can't imagine anyone here who'd be so cruel as to drop a hint about a development they've heard about but can't share with the world yet -
Oh hello Jason, didn't see you there...!
Posted by: jmknapp Jun 9 2008, 04:08 PM
Is a press conference scheduled today? Seems like there's a lot of fodder for questions, given that TEGA is kind of the central instrument of this mission, such that "Poor TEGA" = "Poor Phoenix."
Posted by: Stu Jun 9 2008, 04:14 PM
Yep...
Media Update
NASA and the University of Arizona, Tucson, will hold a media teleconference at 11 a.m. PDT (2 p.m. EDT) on Monday, June 9, to report on the latest news from NASA's Phoenix Mars Lander mission.
Posted by: Sunspot Jun 9 2008, 04:18 PM
How many of the original science objectives can be met without TEGA?
Posted by: ugordan Jun 9 2008, 04:19 PM
Whoa, people... Getting a bit negative, aren't we?
Posted by: Stu Jun 9 2008, 04:22 PM
I was just thinking that... come on guys, first sample dump, first oven, first everything. That's why there are more than one on there; it was very unlikely everything would go perfectly the first time. I reckon the Phoenix team reading this need our support and encouragement now. Keep at it!
Edit: interesting article http://www.azstarnet.com/sn/metro/242862.php...
Posted by: MahFL Jun 9 2008, 04:36 PM
There are plenty of positive things about Phoenix of course. We have colour and 3d pics of the northern tundra. Pretty sure we see ice under the lander. Temperatures, pressures and wind direction. Microscope views of the dust/dirt. I am sure I missed a few things too.
Posted by: JRehling Jun 9 2008, 04:46 PM
To head that off, I think there's just about zero chance that the soil problem will be an impasse. If the arm can dig the stuff up in the first place, it can smash it up for at least some of the TEGA ovens. Barring some OTHER problem, the clumpiness problem will be solved.
Seeing that ice layer under the lander is a big win by itself. But as far as the scenery goes, the thrill ends at having another poster. The science of returning a panorama of this landscape is slim to none. This mission is all about TEGA and MECA.
And with MRO up there, we can get a decent panoramic reconstruction of any spot on the planet -- only the extreme foreground needs in situ imaging.
Posted by: Stu Jun 9 2008, 04:53 PM
I gave another Outreach talk this morning, at a tiny, village school here in Cumbria - just 30 or so kids in the whole school! - and treated them to my "Tourist's Guide To The Universe". Thanks to the already mentioned generosity of the Phoenix Outreach team I was able to give all my group of 22 kids a Phoenix sticker, which they were delighted with (as was their teacher, who somehow acquired one for herself...!). During the talk's Mars section I mentioned Phoenix, obviously, and mentioned the problem with TEGA, explaining that the dust wasn't falling through the grille. One student suggested - without any prompting, which I thought was very cool - using the robot arm scoop to pat at the dust and push some through. But another suggested a rather radical alternative:
"Why don't they scoop up one of those stones", he suggested, pointing at the rocks scattered around the lander, "and drop it onto the dust? That would shake it up, wouldn't it?"
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So, there you have it, Phoenix team, your solution. Obvious really!
Posted by: jmknapp Jun 9 2008, 05:32 PM
But not a televised press conference?
Posted by: ugordan Jun 9 2008, 05:35 PM
Nope, but you can still listen to it: http://www.nasa.gov/news/media/newsaudio/index.html
Posted by: jmknapp Jun 9 2008, 05:38 PM
Thanks!
Posted by: Sunspot Jun 9 2008, 05:59 PM
Let us know what you hear, my computer doesn't have sound any more. Thanks.
Posted by: Harder Jun 9 2008, 06:00 PM
Thanks indeed. With one eye on Euro 2008 I am on line, awaiting the latest from NASA.
Meanwhile I am trying to think about options to get out of the impasse, like all of us I´m sure.
Brute force in my view will not work: even if individual soil/ice particles have dimensions well inside the 1 mm square constraints of the fine mesh, particles will tend to form "bridges" above the mesh preventing more than only a few particles to fall through. I have seen this process first-hand during some physics lessons, it was very interesting to see how large a mesh size had to be to let small ballbearings fall through. Rather big, I recall!
The only thing that can help us out I believe is vibration - to break up this process of bridges forming above the mesh. I´ll keep my fingers crossed!
Posted by: ElkGroveDan Jun 9 2008, 06:11 PM
Press Conference on now...
They gave TEGA a "shake" at a higher frequency -- didn't work. Just a few particles but not enough for an analysis. But there is confirmation that the vibrator does work.
Going to try again with the vibrator. If that doesn't work they will go to a different TEGA slot and drop very small amounts of soil.
Going to operate the vibrator at different times of day to assess the effects of different temperatures.
Optimistic that when they "dribble soil on slowly it will in fact go through"
Posted by: jmknapp Jun 9 2008, 06:27 PM
some notes:
* the spring on the ground is from the bio-barrier
* the scoop has acquired another sample; it "appears cloddy." They are going to do a "sprinkle test" before delivering to MECA
* Boynton: on Saturday they found out they had a large amount of soil delivered to the screen, virtually none of it made it down through the funnel into the oven,
* they ran the vibrator at a higher frequency but just found out today that only a few particles made it to the oven. Good news is that the vibrator is indeed operational.
* They're going to try to run the vibrator again, at three different times of day (different temperatures, humidities). If that fails they are going to try to "sprinkle" a smaller amount of soil on the screen to avoid clogging it up. It should be several days before this is completed.
* Q: what is causing the clumping? A: We aren't sure what's causing the clumpiness. Maybe moisture, salts, electrostatics.
* They are confident that the detector (photocell and LED) works well.
* Q: How much material do you need in the oven? A: 20-30mg. We probably only have a milligram or so in the oven (a couple particles).
* Q: With the doors covered by a good bit of soil--will that impede future measurements? A: No. We're going to open door 5 next which should shake the soil out of the way. The springs are strong enough to do this.
* Q: Is anybody fearful that this isn't going to work? A: We think that maybe we just put too much soil into this first sample. By "dribbling" soil with future samples, we're confident we can get it to work.
* Q: Are you surprised by the cloddiness? A: No.
* Q: When do you start to get worried about this? A: At least a week or two. We have a number of things to try. We aren't optimistic about further shaking, but are more optimistic about the "dribbling" technique.
Posted by: Sunspot Jun 9 2008, 06:27 PM
They gave TEGA a "shake" at a higher frequency -- didn't work. Just a few particles but not enough for an analysis. But there is confirmation that the vibrator does work.
Well, I suppose that's good news of sorts. Maybe if they shake it for long enough they will get a good sample.
Thanks for keeping us updated.
Posted by: tuvas Jun 9 2008, 06:38 PM
I don't know anything that the rest of you don't know about what's going on with TEGA... All I can say is, it has had it's problems, at least 3 that I can name, namely the door opening, the sample entering, and the problem mentioned at the beginning of this post (Was it a broken filament or something?). That's alot of problems for an instrument. Still, it is a very difficult task they are undertaking...
EDIT: I might add while I don't know much about Phoenix operations, I do know a fair amount about how it should work. I've been to the PIT at least 3 times (The area at the UA where they did alot of testing), including once that wasn't a public tour. I've been able to learn alot about some things in operations, although I dare say there's alot of people who know more than I. I also worked on my senior design project with one of the students who worked in the PIT, so I know the most about things relating to things tested in the PIT, namely the robotic arm. Other than that...
Posted by: jmknapp Jun 9 2008, 06:40 PM
notes continued:
They will be using the rasp to vibrate the scoop to cause the material to dribble out (as a function of the angle of the scoop). This will be tried with MECA first & then if it works, the game plan is to try it with TEGA.
Q: How will you try this sprinkling on the TEGA? A: We anticipate that once we figure out how the material reacts to this sprinkling, we'll try to dribble a small amount towards the top of the screen and allow it to slide down towards the bottom of the screen. We also may use the robotic arm to crush the sample ahead of time.
Q: Where will oven 5's sample come from? A: We would anticipate it would be more towards the National Park area than where the first sample came from.
Q: Where would you be right now if there hadn't been any glitches? A: We would have been done with the first TEGA sample if everything had gone perfectly, and we'd be working with the first optical microscope sample and first wet chemistry sample by now.
Q: What is causing the clumping? A:The material may have gotten a little bit wet during the landing and exposure to the thrusters. Maybe there are salts in the soil causing salt cementation. The particles may be interlocking, as well as electrostatic forces.
Q: There are UV lights on the MECA instruments. Might these UV lights actually *create* organic molecules? A: Don't know why the MECA team included these lights.
Posted by: Airbag Jun 9 2008, 07:03 PM
Thank you both for your quick summaries; much appreciated!
Airbag
Posted by: um3k Jun 9 2008, 07:12 PM
If they're referring to the UV LEDs in the MECA optical microscope, I believe they are intended to be used to detect fluorescence.
Posted by: Harder Jun 9 2008, 07:25 PM
For me a positive signal from today´s telecon was the statement that "ice is a completely different material" (from a deeper trench). I.e. I sense confidence that the mechanics of scraping - pulverizing - screening of ice-containing materials from deeper trenches is well developed.
In fact, I wouldn´t mind to leave the topsoil alone and start "digging for gold" right away.
PS
Holland-Italy is already 2-nil before halftime, another "gold" in the making?
Posted by: ahecht Jun 9 2008, 07:28 PM
I'm not sure what the UV LED could do to the soil that sun exposure wouldt've have done already (and yes, I know why the LED is there, I just don't understand the question).
Posted by: ElkGroveDan Jun 9 2008, 07:53 PM
Actually the question was by some guy named Moose or something like that. He asked if the UV flourescence lights had possibly been included intentionally in order to identify biology. There was a long silence, I believe because they always want to be careful of these overboard sensationalist questions. They ultimately deferred and said they didn't know why the instrument was built that way.
Posted by: nprev Jun 9 2008, 08:08 PM
...what did this guy think this was, an episode of CSI? There are lots of fluorescent minerals--salt as in halite being one of them.
Hate to see the Phoenix team being dragged into possibly sticky situations like that. Bet old "Moose" there is disinvited from future pressers, and with good reason. Trying to bait people into making controversial statements in science is reprehensible.
Posted by: jmknapp Jun 9 2008, 08:10 PM
The audio will be up on the NASA site soon anyway, but if anybody doesn't want to wait, I put an mp3 of it here:
http://cboh.org/~jmk/nasatelecon060908.mp3
Posted by: BrianL Jun 9 2008, 08:12 PM
No, that's just what sells. Now, if a scientist is stupid enough to take the bait, that's reprehensible.
Brian
Posted by: jmjawors Jun 9 2008, 08:17 PM
I didn't get that impression about that guy, though I certainly could be wrong. He seemed more interested in the answer to what he thought was an interesting question, not so much creating a sensational angle for his story. Like I said, just my impression.
*shrug*
Posted by: tedstryk Jun 9 2008, 08:21 PM
On the next mission with an instrument like that, I recommend a moving robotic foot. When my electronics don't work, I usually try kicking them...sometimes it works
Posted by: jmknapp Jun 9 2008, 08:23 PM
Same here. He seemed to have a lot of detailed questions like he was following things very closely.
Posted by: Julius Jun 9 2008, 08:27 PM
Holland 3 Italy0
Nasa 0 TEGA 1
Posted by: jmjawors Jun 9 2008, 08:32 PM
I particularly liked learning of the "sprinkle tests" they are doing. Using the rasp to induce vibrations on the scoop, that's NASA problem-solving at its best! Sol 16 seems a little ambitious to me for delivery of a sample to MECA OM, though. Seems like they may need to experiment with many different scoop angles first. But I don't claim any expertise in the area, that's for sure.
Posted by: ElkGroveDan Jun 9 2008, 08:38 PM
The guy was reporting from a major space-related magazine, so he certainly knows the history of Phoenix and the mission. They have stated overtly on numerous occasions that the mission is NOT to detect biology. The mission is to detect evidence of past or present conditions that might be favorable to biology; ergo the reporter surmising that one instrument might have been designed otherwise was just plain irresponsible.
Posted by: Stu Jun 9 2008, 08:57 PM
Hmmm, interesting discussion this. Brings to the surface thoughts I've been thinking, but pushing down, for a while, but what the heck...
I have to put my hand on my heart and say that I feel... uncomfortable... when people who simply raise the question of Phoenix finding life, or evidence of past life, on Mars, are not taken seriously, because after all there is a possibility - however incredibly remote - that Phoenix might just do that, isn't there? I know, I know, it's not a mission aim, and the Phoenix team have, rightly, gone to great pains to dampen down expectations in that area, but nevertheless there is a small chance that Phoenix's instruments could turn up something... amazing.
Just to be clear here, I am not suggesting that Phoenix is going to reveal a thriving subsurface colony of microbes or anything like that! That's ridiculous, as ridiculous - if that's possible! - as claims being made elsewhere that Phoenix has already imaged skulls, bone fragments and even neurons, etc! But if I've read the literature correctly, and read interviews with Phoenix scientists correctly, then yes, there's a chance that Phoenix might find Something, so people asking about that possibility aren't nutters just to enquire about that, are they?
Here on UMSF we're spoiled; we're all - mainly thanks to each other, I'd say - very, very well educated about the geology of Mars, the Phoenix mission, and the possibility of Phoenix learning that Mars was once a much more life-friendly place than it is now. But we're a minority, and the majority of people out there who read newspapers, watch NASA TV, visit the Phoenix website(s) and others, keep seeing the word "life" with regard to Phoenix, so it's no surprise that Phoenix has come to represent the latest "hunt" for life on Mars. We here know that's not the case, but it's the public perception. We have to live with that.
And I really don't think that's necessarily a bad thing, you know? I mean, let's be honest here, if the microscope on Phoenix shows us a picture of a micro-fossil, none of us are going to moan "Oh, great, now we'll never find out the composition of those mineral grains!" will we? If Phoenix should find traces of past life in the ice beneath the landing site, none of us are going to throw our hands up in despair and say "No! I wanted to look at THAT rock over there!" are we?
So, to misquote the WOTW song, the chances of anything living being found by Phoenix are a million to one... maybe even a billion to one... but how we'd all celebrate of we beat those odds...
Anyway, not woo-wooing, really I'm not. And not defending anyone in particular. I'm just thinking outloud really, sitting here with a cat sleeping peacefully across my keyboard, wondering what Phoenix is going to find. Probably nothing. Possibly something. But either way I don't think it's necessarily wrong to ask about it.
Posted by: brianc Jun 9 2008, 09:06 PM
I would have thought best way would be to vibrate the rasp on the scoop as well as vibrate the mesh screen at the same time that they are actually dumping the sample onto the screen. That way as much agitation as possible going on which may prevent the immediate clumping onto the mesh screen.
Also could some of the problem be that the mesh itself may be getting charged electrostaticaly and may actually be 'attracting' the soil / dust particles so that they are forming a barrier on both upper and lower surfaces of the meash and hence clogging any further particles coming through. Would there be any way of discharging such static (if it exists) prior to the dump taking place ?
Posted by: jmjawors Jun 9 2008, 09:06 PM
I know we're now far afield of this thread's topic, but I would also like to add that a reporter cannot write what a specific instrument CANNOT do unless he first asks the question. There's a difference between asking a question and reporting the answer accurately and reporting on ratings-grabbing assumptions (like the recent toilet issue on the ISS -- some reporters continued to insinuate that the station may be de-manned, though that was not the case).
I'll drop the subject. I don't want to be accused of leading this thread down the wrong path (too late).
Posted by: ElkGroveDan Jun 9 2008, 09:07 PM
Good points Stu. But as you noted the vast majority of folks are highly uninformed (or should I say yet-to-be-informed ) on most of this science. Unfortunately it is that atmosphere that allows these nutters to thrive. They take bits and pieces of unrelated data and out-of-context comments and spin it all into some sensational nonsense that detracts from the true nature of the mission. The team needs to stay on message here and not allow parasitic newshounds to steal their years of hard work for one screaming headline. As you say it would be exciting, but if we so much as hint at that possibility, the popular media will devour the entire mission and lable it a failure if anything less results.
Posted by: jmjawors Jun 9 2008, 09:07 PM
Also could some of the problem be that the mesh itself may be getting charged electrostaticaly and may actually be 'attracting' the soil / dust particles so that they are forming a barrier on both upper and lower surfaces of the meash and hence clogging any further particles coming through. Would there be any way of discharging such static (if it exists) prior to the dump taking place ?
I wondered about the rasp and vibrator working together too, and wished I was a reporter on the line to ask it.
Good thought on your second idea too!
Posted by: jmknapp Jun 9 2008, 10:03 PM
Listened again to the UV LED question--the reporter (from Astronomy magazine) didn't ask if the UV light would make organics, he noted that the explicit purpose of the lights was that they would make certain minerals fluoresce, but the reporter notes they would also make organics fluoresce, sometimes in small amounts, and asked if that was a consideration in adding the UV lights to the microscopy stage.
Posted by: tuvas Jun 10 2008, 12:06 AM
I'll just add my 2 cents. If I were designing a mission like Phoenix, and I could do something simple that would allow it to detect life, then I would do it. I wouldn't say anything to the public though unless we found something, because, as all of us know, Phoenix is not meant to find life on Mars. However, there is still a chance that it could. For instance, if it landed on a Martian ant hill, it could tell something was there. Still, it would not be fun to be put on the spot like that...
Posted by: jmknapp Jun 10 2008, 01:05 AM
Relevant to that, this is interesting, from http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/10566/1/02-2617.pdf:
Extraterrestrial wet chemistry
Suites for in situ wet chemistry experiments began with the Mars environmental compatibility assessment (MECA), which consisted of a “teacup” into which a soil sample could be placed. An array of ion sensitive electrodes inserted into the teacup measured the concentrations of a wide range of ions.
MECA was scheduled to fly on the Mars 2001 lander, but because of mission cancellation has not been used on Mars. More recent designs for wet chemistry experiments start with a similar platform, but usually contain 10 or more individual test tubes rather than a single “teacup.” This allows electrodes and other probes to operate with less ambiguity. Flight-qualified prototypes of such instruments are available commercially. With such an instrument, a dye could be added to each test tube without interfering with electronic or other analysis, thus acting as an added bonus. The only instrumentation required would be a diode laser and fluorescence camera; flight-qualified versions of these components are readily available.
Posted by: tasp Jun 10 2008, 02:37 AM
Just running through some ideas here;
Viking results seemed to imply 'unusual' peroxides and superoxides in the soil, could we be seeing some kind of chemical interaction with the mesh material? Or could the mesh material be catalyzing some kind of chemical reaction in the sample?
Can the chlorides and peroxides polymerize themselves and/or CO2? Is the clumpiness telling us something related and significant as to the chemical properties of these substances??
What we are currently looking at as a significant problem with conducting these tests might actually be telling us something pretty important about these Martian materials.
Posted by: Stu Jun 10 2008, 05:28 AM
Goes with the territory I'd say, when you're working on a mission that refers to "life" in its publicity, educational and media material so often. They're big boys, they can take it, I'm sure.
Posted by: peter59 Jun 10 2008, 11:46 AM
http://www.met.tamu.edu/mars/015.html
Looks good.
Posted by: ugordan Jun 10 2008, 11:47 AM
Looks good? I'd wait until we see actual images...
Posted by: akuo Jun 10 2008, 12:20 PM
http://www.met.tamu.edu/mars/015.html seems to have the raw images for tosol already arriving, while there is nothing new at the UA site. A glitch in the UA server? :-P
Anyway the sprinkle test seems to be achieving what's intended, at least in my view.
Posted by: Astro0 Jun 10 2008, 12:36 PM
Vibrates, sprinkles, and folds your laundry.
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(Animation Sol15 sprinkle-test-prep)
Astro0
Posted by: climber Jun 10 2008, 12:58 PM
Thanks Astro.
I'm currious to know if "they" are pleased with that.
Next conference on NTV is for tomorrow 3pm (Eastern); do you know if a call conference is schedulled for tonight ?
Posted by: jamescanvin Jun 10 2008, 01:07 PM
No, I don't think there is a press conference today.
I can't imagine they are not pleased with that, looks perfect!
Posted by: ugordan Jun 10 2008, 01:12 PM
It still looks a bit clumpy to me, there appears to be a lower limit on "grain" sizes from the pictures. I hope they're small enough to pass through the TEGA mesh this time. It's about time that instrument got a break already.
Posted by: Bill Harris Jun 10 2008, 01:17 PM
>Vibrates, sprinkles, and folds your laundry
So the question begs... did this maneuver inspire your "Sample Delivery" image, or was it vice versa? 
It shouldn't be much of a suprise that there are problems with sample delivery to the TEGA ports. This regolith has evolved over thousands or millions of years under alien conditions. From the MER wheel-spinning excursions we already knew that this soil has unusual physical properties, and there will need to be in-situ tests to see how to get this material through the mesh.
--Bill
Posted by: Astro0 Jun 10 2008, 01:34 PM
> So the question begs... did this maneuver inspire your "Sample Delivery" image, or was it vice versa?
Actually when I did http://www.unmannedspaceflight.com/index.php?act=attach&type=post&id=14632 it was more a case of thinking...
"Phoenix Report: Sol 122: Still trying to get a decent sample into TEGA instrument. Another attempt tosol."
But phew, the sprinkle test does look like good news.
Astro0
Posted by: ahecht Jun 10 2008, 02:02 PM
Poor MECA, all buried in dirt. I guess they couldn't find a large enough portion of the lander deck to test this with.
Posted by: Airbag Jun 10 2008, 02:07 PM
Hm, impromptu additional thermal insulation? Now there is a thought...
Airbag
Posted by: climber Jun 10 2008, 02:50 PM
My understanding of the way they are doing the operation is : they vibrate WHILE manoeuvring the scoop so particules fall slowly and bit by bit. Is that right ?
The way I will do it (please do not blame me) : sort them out before delivering to TEGA by :
1- vibrate the scoop long enought keeping ALL the soil inside
2- check visualy if smallest are biggest are separated
3- get rid of the bigger particules if they are at the top of the scoop or if they are at the back put the little one slowly into TEGA first before the biggest one fall.
...may be it is what they are doing! Please tell me your understanding
Posted by: jmjawors Jun 10 2008, 02:58 PM
That's pretty much my understanding too, though they weren't clear at the briefing yesterday if the steps they are taking for the demonstration test would be the same as what they would use if that test was successful. What I mean is, part one of the "sprinkle test" was to try to sort out (and expel) the larger clumps over their dumping site on the surface before moving over MECA and doing the same thing. I'm not sure if this two part "sprinkle technique" will be used each time, or if it will only be used when hovering over the instrument to give a sample.
Posted by: JRehling Jun 10 2008, 04:47 PM
The apron of fallout around the bolts definitely looks like it's made of smaller particles. This case is closed. I may chew through some pens before we get the first actual data from TEGA (and the soil is the less interesting thing in comparison with the ice), but it's good to see things moving ahead.
Posted by: jamescanvin Jun 10 2008, 05:28 PM
Sprinkle from the RAC point of view
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Posted by: climber Jun 10 2008, 06:38 PM
BTW, thanks for "your" blog at the TPS.
I didn't know you've been an extragalactic astronomer, I thought you were an "extragalactic" image wizard only
Posted by: stewjack Jun 10 2008, 07:22 PM
http://www.nasa.gov/news/media/newsaudio/index.html
COMING UP:
2 p.m. EDT, Wednesday, June 11
(11 a.m. PDT) ( 6 p.m. UTC)
Phoenix Mars Lander Update
* A link to the streaming audio will appear here before the event.
Posted by: Harder Jun 11 2008, 06:10 PM
last night´s final run using the vibrator was successful - the oven is full!
Posted by: climber Jun 11 2008, 06:13 PM
It's because they tried, Harder
Posted by: Harder Jun 11 2008, 06:38 PM
Good one, Climber! France - Holland 1-0
I hope there will be a similar opportunity to refer to your nickname when Oppy is halfway up Cape Verde!
PS It looks like the other thread is now continueing with discussions on TEGA, microscopic imager, sublimation of ice in sample etc. Doug can remove this last message from me and leave yr very apt message as a good closure of this thread
Posted by: 1101001 Jun 11 2008, 06:38 PM
Yeah, soil in the TEGA oven.
It was the last of the periodic vibration tries, the seventh. Shortly after starting, the program ended prematurely, and they found: it was because suddenly the oven was full. Once started, it took just a second. It sounds like once the soil was ready, it was really ready.
(My speculation: it was a humidity change that triggered success. Is there anything else that could have changed between 6th vibe that failed and 7th that quickly worked? Temperature? The death of all the bacteria (ha!) in the sample?)
Posted by: climber Jun 11 2008, 06:52 PM
Once started, it took just a second. It sounds like once ... was ready, it was really ready.
Is there anything else that could have changed between 6th vibe that failed and 7th that quickly worked? Temperature? The death of all the bacteria (ha!) in the sample?)
Very close to constipation symptoms here on Earth
Posted by: john_s Jun 11 2008, 07:55 PM
As my aunt always used to say about ketchup: "Shake the bottle, shake the bottle, none'll come, and then a lot'll"
Posted by: Phil Stooke Jun 11 2008, 08:06 PM
" "Shake the bottle, shake the bottle, none'll come, and then a lot'll""
I remember Len Fairclough saying that to Elsie Tanner.
Phil
Posted by: ahecht Jun 11 2008, 08:07 PM
One thing that comes to mind is that the soil is electrostatically clumpy, and that prolonged exposure to UV light from the sun dissipated the charge. It could also be that the soil is icy and the ice sublimated.
Posted by: john_s Jun 11 2008, 08:49 PM
I prefer the ketchup model- you keep nudging the system until you push it over a critical threshold. Though maybe with ketchup, acoustic fluidization is important too...
John.
Posted by: ugordan Jun 11 2008, 10:05 PM
I can't believe the chances of 6 failed shakes and then the last one which noone had any hopes for works. This is great news. Looks like there's no such thing as too-clumpy soil, just inadequately shaken soil...
Posted by: Bill Harris Jun 12 2008, 12:24 AM
Are you thinking that the regolith has thixotropic properties?
I suspect that the sample underwent some sorting as it was vibrated downhill across the screen, and finally and adequate amount made it to the sample vial.
--Bill
Posted by: nprev Jun 12 2008, 12:34 AM
As I mentioned on another thread, it's hard for me to see how UV could equalize charging in clumps if elecrostatics is in fact the mechanism holding them together; would believe that laying the stuff on the metal surface of the oven port could equalize charges enough for the clumps to fall apart.
Likewise, I have a hard time believing that ice is holding them together, since this would appear to require capillary action in the soil, which in turn implies liquid water, which doesn't appear to be possible on the Martian surface. Is it possible a few cm underneath, despite the temperature (or does it warm up enough below the surface from solar absorption to make this possible)?
Something interesting's going on here; really not at all sure what. I'm betting on electrostatic effects, frankly.
Posted by: tuvas Jun 12 2008, 12:52 AM
I'm sure most of us know the electrostatic effects of Lunar dust, might it be possible with Martian dust as well?
Also, anyone know what the filter was made out of?
Posted by: Aussie Jun 12 2008, 01:41 AM
Or is it just the cornflakes syndrome. Shake it long enough and large particles rise, small ones head downwards. Hmm. Have we ended up with a selective sample of small non magnetic/charged particles not indicative of the real soil constituents.
Posted by: nprev Jun 12 2008, 02:03 AM
Could be. Unfortunately, we are left with what we can get, regardless.
Actually, if the electrostatic hypothesis is correct, we might end up with more paydirt in any case; they're looking for organics, not ferric/ferrous minerals.
Posted by: centsworth_II Jun 12 2008, 02:37 AM
Another advantage of crushing the sample somewhat before delivery. I assume they still plan to do that with all future samples?
Posted by: Greg Hullender Jun 12 2008, 03:37 PM
I liked the chart of triple points of different brines in this paper, focusing on the "Mars Surface" portion in Figure 2:
http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1689.pdf
Checking the weather report from Phoenix, the lows are about 190K and the highs are about 240K. Pure water should really be solid across the whole range, but at least some of the brines would be liquid for a good bit of that range. Clumpy wet soil doesn't seem so outrageous.
So when will we have results from the oven? And will that tell us for sure?
--Greg
Posted by: jmjawors Jun 12 2008, 03:47 PM
Look for very preliminary results in about a week (if all goes to plan), with more definitive results following several weeks/about a month after that.
Posted by: Sunspot Jun 12 2008, 04:05 PM
There's a televised press briefing tomorrow.
Posted by: 1101001 Jun 12 2008, 06:08 PM
Mixtures are odd. They sort themselves differently, depending on a lot of factors, sizes, particle friction, densities, container characteristics, interparticle gasses, frequency and amplitude of shaking, and surely more. There is both a Brazil-nut effect (http://en.wikipedia.org/wiki/Brazil_nut_effect) and a reverse-Brazil-nut effect.
But if finally there was success, then apparently conditions, for some reason, became ripe for smaller particles to descend and pass through.
Posted by: gallen_53 Jun 12 2008, 06:27 PM
You beat me to the punch. That's my guess as well. I'm glad the sample is now inside the TEGA.
I'll stick my neck out now and speculate that not much hydrocarbon material will be detected due to the presence of oxidants.
Posted by: ElkGroveDan Jun 12 2008, 06:29 PM
Maybe they'll show Astro0's image for fun.
Posted by: climber Jun 12 2008, 06:54 PM
It's already on TPS
Posted by: dburt Jun 12 2008, 07:17 PM
Checking the weather report from Phoenix, the lows are about 190K and the highs are about 240K. Pure water should really be solid across the whole range, but at least some of the brines would be liquid for a good bit of that range. Clumpy wet soil doesn't seem so outrageous...
Greg, those low temperatures are for chloride brines. Except locally, chloride salts appear to have been largely leached from the martian surface, probably owing to frost. That is, if they'd react with frost or atmospheric moisture to turn liquid now, they would have done so in the past, and the resulting brine would have dripped into the subsurface until it again froze. I (and others) have used this effect (chloride brine drip resulting from frost leaching) to explain the surface enrichment in sulfates as opposed to chlorides. Note that such dense concentrated salt solutions, for the right (calcium-rich) chemistry, should be able to melt their way downwards even into solid ice, if its summer temperature was above about 220K.
That does not mean that minor amounts of chloride salt don't remain in the soil, sufficient to render the surface soil slightly moist and sticky - this has been hypothesized for the slightly "sticky" aspect of the equatorial soils revealed by the two rovers. The observation that presumably frost-rich polar soils (we should know just how frosty soon) tentatively appear to be even stickier than soils at the equator might be consistent with your hypothesis. Dry as a bone soils with purely electrostatic interactions is another possibility, of course, at least until the TEGA results are in.
--HDP Don
Posted by: Bill Harris Jun 12 2008, 07:32 PM
We'll know more in a few days when the TEGA numbres start rolling in and we get some samples under the microscope. The idea of a sticky, hygroscopic soil is a decent first guess, but alas, too terracentric. Remember, this is a really alien world.
Ah, to have a handlens and a gloved hand at the site...
--Bill
Posted by: ElkGroveDan Jun 12 2008, 07:47 PM
Sure but like any good geologist in the field, you know you'd pull the glove off to feel it, and probably taste it too.
Posted by: marsbug Jun 12 2008, 08:40 PM
--HDP Don
Ferric sulphate has also been suggested http://www.lpi.usra.edu/meetings/gullies2008/pdf/8016.pdf, and since iron and sulphate compounds are more common than chlorides on the surface are probably more likely culprits, if it is dampness. As Doug has pointed out in the past, there are any number of things you can mix with water to lower its freezing point. Also I remember that very thin films of water adhered to grains can come under enough pressure from van deer waals forces (If I've spelt that right) to lower the freezing point to 180 kelvin. Also there are a lot of other possible causes of stickiness. We'll know better when TEGA spits out some results.
I feel like a small child in a car shouting 'are we nearly there yet' at his long suffering parents...
Posted by: dburt Jun 12 2008, 10:45 PM
Marsbug - Crystalline ferric sulfates (jarosite and so on) appear to be stable on the dry, cold surface of Mars, but an aqueous solution would be strongly acid and therefore should react with other mineral grains in the soil (e.g., feldspar, olivine, pyroxene) to neutralize itself, unless the acid were continuously being replenished, as by bacterial action on an actively weathering sulfide-rich terrestrial mine dump. In other words, the terracentric proposal in that reference seems to ignore the basic nature of the martian regolith, not to mention the lack of active weathering. On the other hand, crystalline ferric sulfates, or other sulfate salts, might themselves be sticky enough to yield the observed Phoenix soil properties. Pure speculation, without more observational and experimental data.
-- HDP Don
Posted by: Bill Harris Jun 12 2008, 11:42 PM
With (likely) iron sulfates? Gak, pa-tooey, not likely...
But yes, the urge to get up close and personal would still be there...
--Bill
Posted by: dburt Jun 13 2008, 12:03 AM
Agreed, but it also seems to be a really salty world. (This result is perhaps not unexpected, if most of its original liquid water froze solid or was lost to space.) Salts can be sticky, after all.
MODERATOR EDITED - let's not go there
-- HDP Don
Posted by: ngunn Jun 13 2008, 11:02 AM
Its a little ironic that the Phoenix instruments cannot analyse the soil until whatever is giving it its 'unusual and unexpected' property has gone away! Can someone explain (in beginners terms) how, in spite of this, the analyses will shed light on what was causing the clumping?
Posted by: MahFL Jun 13 2008, 11:14 AM
The analysis is not specifically designed to determine why the soil was clumpy. They said it might have just clumped together on the screen as they dumped too much in one go. In future they will quickly chop the soil up and only dribble a little onto a screen. The analysis will determine all of the gases that were in the soil/rock particles, that's the whole point of TEGA. Later they will dig down further and do more analysis, and finally dig and scape up the presumed water ice and test it, I guess when they do that they will get Hydrogen and Oxygen - H2O............
Posted by: MahFL Jun 13 2008, 12:15 PM
Some sol 18 pics came down.
Looks like they greatly elongated the trenches.
http://www.met.tamu.edu/mars/i/SS018EFF897802686_12540R2M1.jpg
Posted by: ngunn Jun 13 2008, 12:32 PM
No, but I'm hoping it will anyway, maybe indirectly. Of course there's so much more to learn than just this. Exciting times indeed!
Posted by: MahFL Jun 13 2008, 01:21 PM
Even if the soil was wet and later it dried out, there is always a chance some moisture remains on a microscopic level, and the TEGA will detect that. It's like damp sand v dripping wet sand, if you know what I mean, its still at some level of wetness......
Posted by: ngunn Jun 13 2008, 02:11 PM
I see. If that scenario remains a possibility would digging, sampling and closing the oven at the coldest possible time of day be advantageous?
And if it's electrostatic clumping is there any way the instruments could positively establish this? Maybe from sprinkle patterns in the microscope samples?
Brittle crust on top, clumpy underneath. 'Damp/dry' could account for both. Electrostatic charge probably only the latter, requiring a separate explanation for the crust. Perfectly possible of course.
Posted by: tuvas Jun 13 2008, 02:21 PM
I think it would be very interesting to sample some soil from the same spot again, using the new techniques so that we can get the sample in a bit faster, and see if there's any difference in the two samples.
Posted by: centsworth_II Jun 13 2008, 02:34 PM
This could be done at the end of the mission -- if nothing so interesting as to use all the remaining ovens on deeper samples shows up.
Posted by: gallen_53 Jun 13 2008, 06:09 PM
.I would guess H2O2 (lots of it) ....
Posted by: marsbug Jun 13 2008, 07:27 PM
It easily decomposes into oxygen and water if I remember, although ... here's a wild speculation to pass the time: H2O2 from the atmosphere (theorized to form during dust storms) is mixed with the soil, and then partly decomposes into a highly concentrated H2O-H2O2 mix with a freezing point low enough to stay stable in martian arctic conditions, producing dampness and making the soil stck together ... ...Nah I can't make an argument for that, I don't know what conditions it needs to decompose. (coughs and looks a little embarresed) 
Presumably TEGA could guess at which it was by looking at the ratio of oxygen to hydrogen released?
EDIT: Actually to quote wikipidea:
2 H2O2 → 2 H2O + O2
Posted by: tanjent Jun 14 2008, 02:30 AM
How will the operation of the TEGA oven affect Phoenix' overall energy budget? Do other operations have to be curtailed at certain stages of the cooking process? With the declining sun angle later on in the mission, at what stage will it cease to be possible to operate the TEGA?
Posted by: centsworth_II Jun 14 2008, 02:58 AM
I guess the question is, would any TEGA oven be saved for an extended mission, or is it predetermined that they will all be used in the 90 day primary mission. In which case your question is moot.
Posted by: tanjent Jun 14 2008, 05:15 AM
Well, Cents, my first question isn't "moot". And your comment in response to the second one assumes that there will be enough energy to operate the ovens out to the 90 day mark, which may be true, but I was trying not to take that for granted. It would be very surprising and illogical if the primary mission plan called for holding resources in reserve for a followup mission, but in practice you should bear in mind that, as we have already seen, things may not proceed as quickly as intended.
Posted by: centsworth_II Jun 14 2008, 04:54 PM
No it isn't. As a matter of curiosity, it would be nice to know what part of the energy budget goes to TEGA. I don't think it's a matter for concern though. Both solar panels are open and providing at least as much power as planned for. Barring a serious dust storm, I can't imagine that there will be energy problems for the main mission. Of course a mechanical or electrical failure can change things at any time.
Posted by: kungpostyle Jun 15 2008, 05:22 AM
Here's a question:
The ovens are single use right?
Are they really? What if you put a sample in the oven that was, say 75% water ice. Baked the living hell out of it and received a rich data set. Great, mission accomplished!
Time passes and you're on to the extended mission; one sol you dig up something interesting. Darn, wish we could TEGA this sample.
Since the water is now baked out of the original sample you've got space in that oven that wasn't there after the initial dump. You re-bake the oven at the highest temp to characterize the remaining material in the oven and account for any change that may have occurred during the intervening sols and you've got yourself a new tega oven!
Deliver new sample, run a new workup. I realize this would be a rather ill controlled experiment. You would be adding un-baked material to what would now be thrice baked material but it could be better than nothing at all.
Is this possible?
I'm assuming of course a light sprinkle of the original sample on the screen, not a massive dump like the first TEGA go 'round
Kung
Posted by: helvick Jun 15 2008, 06:51 AM
It would be very useful to have a rough idea of the energy budget overall and some details of the power requirements for the various instrumentation packages but even without that we can be pretty sure that energy budget concerns are not likely to be a major factor in limiting extended mission activities up to around Sol 150. Preflight press releases said that Phoenix could manage with just one functioning solar panel and whatever the initial power generating capacity actually was with two functioning panels she will still be generating more power from two at Sol 180 than she would have initially with just one. Ambient temperatures don't change significantly (+-10 degrees) until after around Sol 150 but they start to drop pretty fast after that, by Sol 180 they will have dropped by 25-30 degrees so power for heating is could become a significant part of the energy budget by then.
Posted by: centsworth_II Jun 15 2008, 07:09 AM
Even though heating takes a lot of energy, the TEGA ovens are so tiny that I suspect the energy requirements of the many digging activities make the robotic arm the energy hog of the mission. (Not that I know anything.)
Posted by: jamescanvin Jun 15 2008, 09:27 AM
The ovens are single use right?
Are they really?
Yes. Once the oven is closed that's it, it can't be reopened to add another sample even if you've baked what was in there to nothing.
Posted by: climber Jun 15 2008, 09:33 AM
Hopefully there will be all 8 + 4 empty ovens at the end of the mission. Same as at landing
Posted by: Airbag Jun 15 2008, 02:22 PM
Paraphrased from the "Thermal and Evolved Gas Analyzer" document: it all depends on the ambient conditions (i.e. mainly the instruments' own heaters use) but is can be as low as 9.6W with all heaters off to as much as 78.0W with all heaters on and a sample oven on.
Airbag
Posted by: Airbag Jun 17 2008, 02:14 AM
TUCSON, Ariz. – One of the ovens on NASA's Phoenix Mars Lander continued baking its first sample of Martian soil over the weekend, while the Robotic Arm dug deeper into the soil to learn more about white material first revealed on June 3.
"The oven is working very well and living up to our expectations," said Phoenix co-investigator Bill Boynton of the University of Arizona, Tucson. Boynton leads the Thermal and Evolved-Gas Analyzer (TEGA), or oven instrument, for Phoenix.
From:
http://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080616.html
Airbag
Posted by: Juramike Jun 17 2008, 04:25 AM
Space.com http://www.space.com/missionlaunches/080616-phoenix-mission-update.html says the first TEGA soil sample appears dry.
No water has been detected so far after the initial heating to 35 C, then to 175 C.
[Hmmm, if the white stuff is indeed ice, I woulda thought maybe a little bit of water crystals might've found there way into (via sublimation/deposition) pore spaces in the upper soil grains]
Posted by: jmjawors Jun 17 2008, 05:08 AM
As they said in the briefing today, remember that that sample was exposed to the sun for several days before being delivered to TEGA. Any ice in there (if there was any to begin with) would surely have sublimated by then. Bill Boynton himself said he was "not surprised" by these results.
Plus, there's no guarantee that the white stuff in the scoop ever made it into the ovens.
Posted by: climber Jun 17 2008, 06:17 AM
3d glasses! Did you go to NYC recently ?
Posted by: jamescanvin Jun 20 2008, 05:43 PM
And now for the bad news...
The doors on TEGA oven 5 have not opened properly.
The team were very confident that the soil piled up would not impede the doors. I really hope there is not a design problem here, only 1 out of 4 (2 per oven) doors have opened properly so far 
James
Posted by: jamescanvin Jun 20 2008, 06:10 PM
Animation of the attempted opening of oven 5
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Posted by: mhoward Jun 20 2008, 06:14 PM
Very strange. Here's a (very) wild speculation: Did some dirt actually drop down into the oven and, when it was detected, the door opening sequence was halted?
Posted by: jamescanvin Jun 20 2008, 06:17 PM
No. I believe that the doors are spring loaded. A catch is released and the doors open very quickly.
Note that the soil on the left door (as we look at it) has been catapulted off and can bee seen on the surface near the top-left of the image.
Posted by: ugordan Jun 20 2008, 06:18 PM
I was afraid this partial opening would occur on other doors as well.
Posted by: James Sorenson Jun 20 2008, 06:35 PM
looking at James's animation, to me it looks like the soil is pinched between the door hinges, and that is preventing the doors from opening. Just speculation .
Posted by: Tman Jun 20 2008, 06:41 PM
They stopped even a bit earlier than the first one. Are there any thoughts why they do (can) block this way?
Posted by: Juramike Jun 20 2008, 06:42 PM
How comfortable would they be trying to use the arm/scoop to sweep away some dirt from the oven doors?
(Having a little experience with automated equipment, I'd be nervous as hell).
Posted by: elakdawalla Jun 20 2008, 06:42 PM
Bill Boynton said in an http://www.planetary.org/blog/article/00001501/ that the doors were spring-loaded, and, moreover, that the springs should be powerful enough to open a door buried under an inch of soil. It seems to me that spring-loaded doors should have been one of the simpler moving parts of this machine -- I'm at a loss even for suggestions as to why they wouldn't be springing open all the way if they spring open even part way. Could there be some weird mechanical thingy going on that isn't working under Mars gravity? That seems implausible.
--Emily
Posted by: Juramike Jun 20 2008, 06:44 PM
Could soil clumps be jamming up the hinges?
Posted by: James Sorenson Jun 20 2008, 06:52 PM
Why does the door on the left in James's animation not open?, there is nothing on that door.
Posted by: Gsnorgathon Jun 20 2008, 06:56 PM
Those springs are awfully cold, and may have been for quite a while. What temperature was the lander during cruise?
Posted by: Tman Jun 20 2008, 07:15 PM
(Having a little experience with automated equipment, I'd be nervous as hell).
Or even programming moves to open them with the scoop...
Posted by: akuo Jun 20 2008, 07:34 PM
This looks worrying. Can the scoop actually reach the doors?
Posted by: Tomek Jun 20 2008, 07:52 PM
the best way to open this doors is send more then ten comands to open and close this doors , this way the soil move down from this doors .
Posted by: 1101001 Jun 20 2008, 07:54 PM
I don't understand that the doors have actuators that can flap them. They are spring loaded. You send the signal, a latch opens, and the door is supposed to pop open. There's no command for closing them.
Posted by: ngunn Jun 20 2008, 07:56 PM
That doesn't sound at all wild, it sounds quite likely (even if it is not the cause of the doors jamming). I don't see how they could have opened that set of doors even a chink without some falling in. When will we know this?
Do they have a way of deliberately doing only a partial opening - maybe to avoid throwing soil from the first dump even further along?
Posted by: elakdawalla Jun 20 2008, 07:59 PM
There isn't an actuator on the doors. Just a latch and spring. You command the latch to release the spring and the spring pops the doors open, like a jack-in-the-box. Once you've done that, there's nothing more the TEGA instrument can do to make the doors open any more -- there's no motors. The doors can't be closed once they're opened.
And I can't imagine they'd try to maul TEGA with the digging arm unless it was the last possible option. Remember they can't joystick the arm. They have to sequence its every move. I don't know what its accuracy is but for all of its normal operations -- digging and dumping -- it doesn't really need to be more accurate than a centimeter. (If somebody knows what the arm's positional accuracy is, that number would help in this conversation.) What happens if you command it to touch a door and it's a centimeter off?
--Emily
Posted by: Tomek Jun 20 2008, 08:03 PM
If it is no comand to closing them and open them again so only wibration is the way now which can make it .
Posted by: Zvezdichko Jun 20 2008, 08:05 PM
This was totally unexpected. Maybe we should wait to get the other pictures with hopes that during the Martian day it got warmer ...
Posted by: jamescanvin Jun 20 2008, 08:05 PM
That's right, it's a once only deal, now that they have been released there is no way of moving them again. (Short of using the arm as others have suggested, something I'm pretty sure we won't see until well into any extended mission and after all ovens have been tried, if ever.)
Besides I don't think the problem is with soil obstruction. The fact that both the doors opened the same amount is telling I think. And remember that the first oven had a similar problem when there was no soil anywhere near it.
Looks more like an issue with the design operating in Martian conditions to me, although I'm at a loss to come up with any good ideas as to the mechanism.
James
Posted by: hendric Jun 20 2008, 08:07 PM
Oh dear. My guess is that the doors can lift the weight of an inch's worth of soil from their top, but the soil has fallen into the hinges and is preventing them from turning. However, I find it hard to believe they didn't test this situation with actual soil of some kind. If they go with much smaller dumps in the future, it might not be a problem.
Posted by: mhoward Jun 20 2008, 08:10 PM
IIRC, in a recent call Ray mentioned that the arm goes where they tell it to within a couple centimeters. That was by way of comparing it (in fairly glowing terms) to the MER arms.
Posted by: Tman Jun 20 2008, 08:19 PM
Yes it depends on how small steps the scoop can do. Otherwise it may depends how the doors are connected with the Analyzer and which parts of it could be (or not) battered when the scoop touch the door too hard.
Posted by: Ken90000 Jun 20 2008, 08:27 PM
It troubles me that neither door opened.
Can they attempt to vibrate the mesh beneath to see if something can make it 'Pop' open?
I just hope there isn't a misalignment that has caused some slight warping of the oven doors.
Posted by: imipak Jun 20 2008, 08:31 PM
I'm sure the possibility of sample clogging the door hinges would have been obvious during design and testing, and allowed for. But then I can't believe they didn't test opening the doors with material on top in the temperature range it's designed to work at. I wonder if there's a link with the problems presumably caused by the sample's clumpiness when trying to get the first sample to fall through the screen into it's oven.
The other thing that springs to mind: is there any way that anything could have frozen out onto the mechanism, either during EDL or since landing? It's too warm on the surface now, but the TEGA would have been exposed to the atmosphere as soon as the backshell was jettisoned at an altitude of 1000m or so. Or exhaust from the thrusters,.. -I'm drifting...
Posted by: jamescanvin Jun 20 2008, 08:35 PM
Sure they can try, but remember the first oven was vibrated a LOT to get the sample in and the partially opened door on that oven hasn't moved at all, so I wouldn't hold out much hope if the same problem is responsible here.
Posted by: Juramike Jun 20 2008, 08:36 PM
[Arms waving wildly here...]
Is it at all possible that atmospheric water ice is being deposited in the hinge joints and freezing stuff up?
Posted by: fredk Jun 20 2008, 08:44 PM
Yikes. I first thought soil under the hinges like others here. But now I doubt that's it for two reasons. First, both oven 5 doors opened to the same extent, but the right one presumably would have had much more soil under the hinge. Second, the left oven 4 door opened to a similar extent as these oven 5 doors, but when oven 4 was opened, there was no soil at all on top of tega. This suggests some unusual design flaw.
Posted by: centsworth_II Jun 20 2008, 08:50 PM
Maybe during launch or landing something got knocked out of alignment. I really doubt that it is soil or freezing causing the problem.
I wonder if they will attempt to shake soil, bit by bit through the small opening or if they will open a new set of doors. I bet the team is wondering the same thing. I'm sure they will not try to use the scoop to open the doors until other doors, and shaking dirt into the small opening have been tried.
Posted by: ngunn Jun 20 2008, 09:00 PM
A random observation - the door that opened best was an end one. If something has distorted the whole panel on which the door hinges are situated maybe the end hinges would be the least affected? Perhaps the one at the other end will open symmetrically with the first, and the two middle sets only a crack?
I agree with centsworth, it should be possible to get a sample in even through a crack.
Posted by: PaulM Jun 20 2008, 09:00 PM
I wonder if when they vibrate the mesh this will cause the first sample to work its way into the second oven. Now that the first sample has spread out it looks to me as if some could even work its way into the third oven.
Posted by: ZenDraken Jun 20 2008, 09:00 PM
imipak: Agreed, they must have tested the doors exhaustively (They did, didn't they?). It's hard to see how mere soil could jam up the doors. But if water or brine or whatever got into the hinges and froze, that could be another thing altogether.
Seems like repeatedly pushing on the doors with the scoop, allowing them to spring back over and over again, might work the ice/brine/grit out of the hinges. Or how about holding the scoop against the doors and vibrating the scoop? Just a thought.
And: Howdy all. Brilliant forum you got here!
Posted by: peter59 Jun 20 2008, 09:14 PM
The doors of TEGA are angled at around 45 degrees to the horizontal, so sprinkle technique from above the top of the ajar door is probably possible and may be effective. I hope that oven #5 is not lost.
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Posted by: ngunn Jun 20 2008, 09:35 PM
Hello and welcome! It's not always this busy, but it takes a lot of people to fix a door hinge.
Posted by: elakdawalla Jun 20 2008, 09:58 PM
Question, James -- how do you know this is oven 5 and not 3? Or even some other number?
--Emily
Posted by: ZenDraken Jun 20 2008, 10:04 PM
Note for future missions: Bring a tool kit!
Seriously, a few attachments for the scoop would be really handy: A small pry-bar, something like a hammer, and a brush. Any other ideas?
Posted by: jmknapp Jun 20 2008, 10:08 PM
Magnet?
Posted by: jamescanvin Jun 20 2008, 10:08 PM
Did they not say in the teleconference that they were opening oven 5 ready for the next sample?
I posted that image while listening to the conference in that background and was pretty sure of myself then, not so sure now. Anyone else remember hearing this in the teleconference?
James
Posted by: jmjawors Jun 20 2008, 10:09 PM
I think they said oven 5 as well, both today and in a previous briefing.
Posted by: elakdawalla Jun 20 2008, 10:10 PM
Thanks. I wasn't able to listen to the teleconference very carefully today, so I didn't catch that.
--Emily
Posted by: jamescanvin Jun 20 2008, 10:17 PM
I'm glad somebody else heard 5. Because I started to doubt myself. I don't understand the numbering sequence if this really is #5, does that mean the numbering starts from 0? (0-3 on the other side) It would make more sense if this was #3 (5-8 on the other side). Or are there 5 on one side like it appears in the image peter59 posted above, unlike the 4+4 arrangement in http://www.nasa.gov/mission_pages/phoenix/spacecraft/tega.html?
Posted by: Reckless Jun 20 2008, 11:05 PM
hi all
just a long shot as I don't know the layout of the doors but is it possible that all the four doors opened and three of them bounced back partially closing.
Roy
Posted by: Shaka Jun 20 2008, 11:53 PM
O.K., brain-bashing time.
1. The first oven doors opened a substantial amount before sticking.
2. The second oven doors, several sols later, opened only a small amount before sticking.
Does this imply that there has been a progressive jamming of the hinges? A steady accumulation of something in the hinges?
3. The retro rockets exposed and heated a significant area of ice under Phoenix, producing a cloud of water vapor that permeated TEGA.
4. The exposed ice has continued to sublime, wafting more vapor through the lander.
Are there critical opposing metal surfaces within the hinges which could collect water vapor and deposit it as ice, given their ambient temperatures and shielding from sunlight or other heat sources?
Could such an accumulation prevent the surfaces sliding over each other, jamming the hinges?
Has the TEGA door operation been tested under Martian conditions including this vapor flux?
Is there any way of adding heat to the door hinge areas to clear such ice?
Posted by: centsworth_II Jun 21 2008, 01:46 AM
Ice disappears from, is not added to, surfaces in the here and now of Phoenix. I don't see how icing can be the problem. A door with little dirt on it failed to open, so I don't see how dirt can be the problem. There may be a tolerance in the mechanism that was too tight for the jostle of launch or landing, but I expect they tested to rougher extremes than were actually experienced. I guess that's just a long way of saying.... I don't have a clue!
Posted by: centsworth_II Jun 21 2008, 01:48 AM
I would hope it was designed so that this is not a possibility.
Posted by: Aussie Jun 21 2008, 01:53 AM
It may be significant that the outer door on the first set of doors opened fully, while the inner door only opened some 40 degrees. The second set of doors only opened around 25 - 30 degrees (estimated). So the common factor appears to be adjacent doors. If this is correct then there are three more ovens with outer doors which should open fully and enable material to be delivered.
I would have thought that if ice deposition is the cause of the door problems then this would result in a go/no go scenario rather than a partial failure. But if failure of the door opening mechanism on the inner sets of oven doors does preclude sample delivery to the ovens (and as Peter59 points out the angle of the ovens to the horizontal means that there is a reasonable triangular gap at the upper part of the doors) then using the arm to free the doors would be an acceptable last resort. Not as a scrape but as a hammer tap. If this fails and results in damage to a non operating door - so what?
Posted by: Paul Fjeld Jun 21 2008, 02:50 AM
Wild guessing: based on the seeming precision with which they dug side-by-side trenches (they're almost exactly the same) in a ground whose position was measured only photogrammetrically, I bet they can do better than a cm in accuracy. (Does anybody know the MER accuracy? I think the joints are the same, although the arm lengths are much greater.) They've got the entire spacecraft (and TEGA) coordinates easily to some fraction of a mm and can reach it. Why not poke the doors down and release with a simple motion? Or slide the scoop down the TEGA topside so the lip is touching just above the top door hinges, then slowly command a wrist up movement? Like popping a bottle cap...
Paul
Posted by: Juramike Jun 21 2008, 03:53 AM
Machines are beautiful things. Once commanded they will try to move the programmed distance whether it is through air, vacuum, ice, soil, or spacecraft metal. If the programming of a self-touch is off even a fraction of a centimeter it could cause serious damage to the arm or spacecraft or both.
I'd be real hesitant to try such a move before all other options have been exhausted.
-Mike
(I've programmed liquid transfer robots and seen the speed that the needle plunges down to suck up/dispense liquid. The needle doesn't care whether it plunges through air, a rubber septa, or a hand. I always give the robot arm a healthy amount of respect.)
Posted by: tanjent Jun 21 2008, 04:41 AM
James
Maybe the most urgent question is this: Are we seeing a progressive weathering process (dust, chemical, thermal, moisture, etc.) that is affecting all of the doors simultaneously and continually reducing the likelihood that they will perform properly when called upon? If not, there is no particular urgency to move on and try the next door. It allows time to test various hypotheses and potential fixes to try to get the #5 oven working as planned. But since #5 seems to be in even worse shape than #4 was, it will be nerve-wracking for the mission managers to have to worry about whether we are in a "use it or lose it" situation with respect to the remaining doors. This makes a case for trying at least one more door, maybe not immediately adjacent to the ones that have malfunctioned, before too much more time elapses. It may throw the intended sequence into some disarray, but if oven #1 works fine and dandy then we can come back and spend ten days trying to get a sample into #5 without concern that the remaining ovens will prove unusable when their turns come. If #1 behaves like #5 or worse, then maybe the TEGA-related operations (including digging) can be accelerated to identify any remaining operable doors and use them as soon as possible. In the worst case, with practice and the proper motivation I am sure the engineers can figure out how to tickle it with the robot arm when it becomes clear that other options are exhausted.
Posted by: Stu Jun 21 2008, 07:16 AM
I'm just catching up on this story after being away from UMSF last night, so apologies if my thoughts duplicate others', but it seems to me that the problem might be a build-up of dust between the two sets of doors. Thinking about it, that dirt has been sat on - and between - the adjacent door hinges for several sols now, and during that time it's been vibrated and jiggled about several times by the various activities - the multiple attempts to send material through the first oven's grille by vibrating it, robot arm operations, etc. So it seems to me that the material piled up over the gap between the doors will have settled quite a lot, with the very fine material gathering down at the bottom of the pile. Now, we've all heard the mystery of the "sticky soil" discussed, so is it possible that all the activities have led to a kind of reaction in the inverted cone of material now sitting over the gap between the doors, turning it into a kind of martian cement? That would bung up the works really fast...
Also a top-of-my-head thought... is it possible for some of the heat generated by the TEGA oven baking the first sample to radiate to the material sitting between the doors and make it react in some way? Probably not, just thinking outloud.
Boy, those TEGA guys are earning their money right now... good luck to all of you reading this. We wish you well.
Posted by: Tman Jun 21 2008, 07:54 AM
From this http://www-robotics.jpl.nasa.gov/people/Robert_Bonitz/: http://www-robotics.jpl.nasa.gov/publications/Robert_Bonitz/IPS_IEEE_Aerospace_2005_final.pdf
Guess too the only move they could do with the scoop is to poke the door down several times. It shouldn't be, but there may be already too much soil in the mechanism of the doors to allow that move with the doors.
Posted by: Paul Fjeld Jun 21 2008, 10:03 AM
Great paper, Tman!
A demonstrated accuracy of 0.8 mm was cited for the Opportunity arm. I don't think the extra lengths of the Phoenix arm would make a big difference. An important issue might be the flexing of the arm while moving into a final precise position. I really bet they could do it (after exhausting more prudent options)!
Paul
Posted by: Paul Fjeld Jun 21 2008, 11:12 AM
On Mark's http://www.met.tamu.edu/mars/025.html page, near the bottom, he has a stereo pair of the scoop at TEGA with this intriguing header:
"1302-E: SSI Documentation of RA at TEGA Teach Point & Closed Door"
Paul
Posted by: imipak Jun 21 2008, 11:59 AM
Those oven doors look awfully small and flimsy next to the RA and scoop.
Seems to me this sequence (and the arm move) doesn't make sense unless using the scoop on the doors is a serious possibility in the next few Sols.. I can think of three ways to try:
- press down and release, hoping the spring will work properly given another chance
- get the lip of the scoop into the gap and flip one door open
- a side-swipe manoeuvre to push one door open, moving the scoop along parallel with the oven-door surface of the TEGA wedge
- ...others?
EDIT: do my eyes deceive me, or does it look as if the right-hand door (as we look at it) of the current oven has opened more fully? (Or is it completely closed?) I can only see the triangular shape of the door closest to the RAC:
|
Posted by: 1101001 Jun 21 2008, 01:15 PM
That doesn't jibe with the mention at the most recent briefing that the robot arm stopped digging at the Snow White 2 trench, as programmed to do, when it hit ice. They probably use the current draw for the actuators as a sense of touch.
I don't know how fine that sense is, but there is some ability to have the arm not try to pass through something too solid. It's already encountered very hard stuff and it's still functioning.
Posted by: jamescanvin Jun 21 2008, 01:47 PM
This image was taken before the attempted opening so all your seeing is oven 4.
Tosol (26) we have: "SSI doc TEGA, 1318" which will be our first look like that since the opening.
Posted by: centsworth_II Jun 21 2008, 03:23 PM
To me, "teach point" means a rehearsal of where the scoop will be positioned while shaking the next sample into TEGA. The arm has a memory and if the position is fine, it can be told to return to it with the actual sample. Looks like standard routine.
Posted by: Paul Fjeld Jun 21 2008, 03:29 PM
Okay. Maybe I am reading too much into the header. But "closed door" is mentioned...
Paul
Posted by: ugordan Jun 21 2008, 03:32 PM
That imaging sequence was designed before the door was opened so the caption isn't likely to be referring to the failure to open - there was no way to know that beforehand.
Posted by: Paul Fjeld Jun 21 2008, 03:49 PM
Right. I just checked Emily's http://planetary.org/data/phoenix/raw/022.html and Door #5 was opened between 12:45 and 14:30 on Sol 25.
Paul
Posted by: ugordan Jun 21 2008, 05:25 PM
Sol 26 images started to come down and it http://phoenix.lpl.arizona.edu/images/gallery/lg_7039.jpg...
Posted by: Tman Jun 21 2008, 05:41 PM
Shouldn't be an issue. The arm is very solid and the final move to touch the doors could perform the scoop alone. Btw. this animation shows an accurate motion with at least two actuators http://www.nasa.gov/mission_pages/phoenix/images/press/13339.html
It looks like the distance to the MECA was rather stable and the used "sprinkle technique" sounds very interesting to vibrate on the doors too.
Posted by: Paul Fjeld Jun 21 2008, 06:24 PM
I make Door #5 to be standing up about 6-7 mm. Lots of "cushion" :-)
Paul
Posted by: SteveM Jun 21 2008, 09:23 PM
For those in a pessimistic mood, here are the minimum http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/40351/1/07-0267.pdf
4. If TEGA, analyze at least 2 soil samples to create a profile of H2O (in the form of hydrated minerals,
adsorbed water, or possibly ice at the deepest level) and mineral abundances near the surface. It shall
also analyze an atmospheric sample in its mass spectrometer.
5. If MECA, analyze the wet chemistry of 2 soil samples.
Steve M
Posted by: tanjent Jun 22 2008, 04:04 AM
Success is better defined by the taste it leaves in your mouth than by some bureaucrat's list of ex-ante bullet points.
Sure, the biggest threats to mission success are in the launching and landing phases, so if you draw up a list of success criteria before launch, you'll settle for getting to the destination safely, taking a couple pictures, and doing a little science. But at this stage you can bet nobody's going to take refuge in the pre-launch criteria if the soil analysis terminates prematurely due to "door failure". Not on the heels of MRO. Anyway, they're going to work it out.
Posted by: jamescanvin Jun 22 2008, 09:49 AM
Notice that is either TEGA or Wet Chemistry, not both for minimum mission success.
For those in a optimistic mood, we only need 3 TEGA measurements for full mission success. No evidence we won't make that, one out of two so far.
Posted by: ugordan Jun 22 2008, 02:58 PM
"1302-E: SSI Documentation of RA at TEGA Teach Point & Closed Door"
Sol 27 has the interesting sequence description, a-posteriori of what is supposed to be an open door:
"SSI Documentation of TEGA (Open!?) Door" - ActId: 1338
Poor TEGA...
Posted by: fredk Jun 22 2008, 04:00 PM
Posted by: jamescanvin Jun 22 2008, 04:09 PM
"SSI Documentation of TEGA (Open!?) Door" - ActId: 1338
Interesting. SSI took a image of TEGA yestersol with the partially open door 5. Maybe they are trying to open one of the doors on the other (visible properly with SSI) side tosol? I'd be temped to try this if I were them.
True.
Posted by: ugordan Jun 22 2008, 04:10 PM
I'm more inclined to think this is just for documenting the door No. 5. We'll see soon enough.
Posted by: centsworth_II Jun 22 2008, 04:23 PM
An optimist would say the small opening may allow just the right amount of material through to sift through the screen without clumping up in a cohesive pile (The pessimist would say the soil may clump in a cohesive pile over the small opening).
Posted by: imipak Jun 22 2008, 07:54 PM
This card-carrying pessimist is wondering if surface-film ice could be the cause of the clumpiness that prevented the sample getting through the screen of the first oven, in which case the screen will act as an perfect barrier to ice (mixed with regolith, anyway) ever making it into the oven. Anyway, let's hope purer ice collected with the scraper or rasp will be less sticky than the first soil sample, or that the soil mechanics are different with the sprinkle method.
Posted by: Littlebit Jun 23 2008, 04:07 AM
What about the actuator itself: The soleniod that releases the locking pin? Is it possible the doors are still dragging on the pin, or is it positioned so that a partially opened door is (obviously) clear of the pin?
Posted by: Ipparchus Jun 23 2008, 07:01 AM
Why don`t they just use another oven? let`s say oven no.6. We have 6 ovens left! why do they want oven no.5? we could leave it for the end of the primary mission, and if it works then OK.
Posted by: centsworth_II Jun 23 2008, 07:24 AM
They may end up doing that. But not before they spend some time trying to figure out what is going on. There are nine weeks left in the primary mission. That's one week for each of seven unused ovens with two weeks left over. Time enough to do some testing and decide on a course of action.
Right now, I'd be happy to know which oven is number six, and how the rest are numbered, just out of curiosity.
Posted by: Stu Jun 23 2008, 01:50 PM
Good TEGA article http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=2783&mode=thread&order=0&thold=0...
Posted by: fredk Jun 23 2008, 03:20 PM
I could imagine that the oven door problem is temperature related, for example. What if the chance that a door gets stuck partly open is greatest at the warmest part of the day, and if they open them first thing in the morning they will open fine?
Of course it may have nothing to do with temperature, but it's definitely worth trying to figure out what the root of the problem is before opening another oven, in case there's anything that can be done to improve the chances that they open fully.
Posted by: dvandorn Jun 23 2008, 03:28 PM
I'm imagining pretty much the reverse, Fred. I'm thinking that the springs may have become very stiff in the Martian cold, and they're just not pushing the doors far enough to have them achieve the stable "open" position. In which case, we'd have best luck during the warmest part of the day.
However, if it's not the springs that are binding but the door hinges themselves, it's possible that the metal of the doors has shrunk in the cold, just enough to make the hinges bind. If that's the case, it's possible that, again at the warmest time of day, a good sharp rap on the side of the entire TEGA device might indeed jar the doors open.
Of course, the only thing you have available to produce a good sharp rap is the robotic arm...
-the other Doug
Posted by: ugordan Jun 23 2008, 03:31 PM
I imagine the team is scrambling to test door opening here on Earth as well, trying to isolate possible failure modes in a similar environment. I can't imagine them not testing the opening mechanism under martian temperatures even before launch, though.
Posted by: centsworth_II Jun 23 2008, 04:18 PM
I have to believe there is a physical impediment blocking the doors -- something out of alignment. The spring is released, putting constant pressure on the door over the entire course of a Martian day with no change in the opening size. If temperature related stiffness or tightness is the cause, some change should be seen as the temperature changes throughout the day.
They could just place the scoop in contact with the TEGA superstructure, or even on an adjacent area, and vibrate it. This vibration may be stronger that that provided by the TEGA vibrator alone.
Posted by: Paul Fjeld Jun 23 2008, 04:32 PM
What about having only one of the #5 doors fully open? That should give them enough room to get something in, no? I'm thinking placing the scoop lip just below the height of the open doors, then gently rotating the azimuth north, pushing down slightly the more southern door #5 but catching the more north side door and pushing it up. I think the geometry works. I don't care if it goes too far into #4 since I guess they're done with that. You could only do it in one direction so don't open any doors south of it until you've tried.
Paul
Posted by: centsworth_II Jun 23 2008, 04:36 PM
I can't wait to see -- after mulling over all our suggestions -- which one they choose.
Posted by: Paul Fjeld Jun 23 2008, 07:16 PM
I'd fall off my chair if they used any of them!
Paul
Posted by: centsworth_II Jun 24 2008, 07:56 AM
Hey! Whats' going on here?
I check http://www.planetary.org/blog/article/00001519/ and see this:
"Phoenix successfully delivered a sample from the Wonderland area to the Optical Microscope on Saturday (sol 26), and managed to leave enough soil in the scoop to deliver a sample from the same location to the wet chemistry laboratory and to TEGA."
Excited, I rush to UMSF to find.... nothing. I'm starting to think maybe I'm missing something, or Emily made a mistake. Then I check http://www.met.tamu.edu/mars/028.html and find this:
|
Is that a pile of dirt I see covering the partially opened doors of oven five?
So... what's going on?
Posted by: akuo Jun 24 2008, 08:20 AM
No, that's still the dirt on the door #4. See sols 25 &26:
http://www.met.tamu.edu/mars/i/SS025EFF898425539_1302EL1M1.jpg
http://www.met.tamu.edu/mars/i/SS026EDN898525164_13180L1M1.jpg
The Phoenix team hasn't said much what are their current TEGA plans, just that a TEGA sample should be delivered eventually. I guess they let the MECA and wet chemistry deal with the samples first, as they figure out what to do with TEGA.
Posted by: TheChemist Jun 24 2008, 08:24 AM
Well, Emily says that enough sample is left for delivery to WetChem and TEGA. Not that it was actually delivered there. We'll have to wait and see.
Posted by: jamescanvin Jun 24 2008, 08:47 AM
The way I read the recent activity.
Sol 25: Acquire sample to be delivered to all three instruments Microscope, Wet chemistry and TEGA. Open TEGA doors for the sample which fails.
Sol 26: Delver sample to Microscope
Sol 27: Recover from safe mode
Sol 28: Deliver sample to Wet Chemistry
Sol29: [tosol] ???
Posted by: akuo Jun 24 2008, 09:23 AM
Nobody seems to have mentioned this bit from http://www.planetary.org/news/2008/0621_Phoenix_Scientists_Confirm_WaterIce_on.html:
Posted by: Bill Harris Jun 24 2008, 11:43 AM
Certainly, there is a design spec to ensure that everything works at Mars-ambient temperatures. Whether metric degrees or english degrees...
One simpel gotcha is the coefficient of expansion of materials. At +20o you have one clearance in the mechanism, but at -60o you have a negative clearance (ie, it binds). I once built a nice camera focusing mechanism for my telescope which had ball bearings with a perfect interference fit in the housing. At room temp. But I found that below 0o F the difference in expansion between the aluminum of the housing and the steel of the bearings yeilded a loose slip fit clearance, which resulted in inconsistent focus problems.
Also, I don't know if there is a "temperature coefficient" with springiness, but materials can become more brittle in cryo-environments, and this might affect the spring's ability to open the TEGA doors.
Mars is an alien world...
--Bill
Posted by: helvick Jun 24 2008, 12:02 PM
Young's Modulus, which is one of the measurements of the tensile elasticity of a material, definitely exhibits some temperature variation and generally (always?) reflects the fact that materials get stiffer as temperature drops. My understanding of the effect is that lower temperature should create a stiffer spring though - and unless the temperature is far higher than they expected I can't see how the springs would end up being too weak to carry out their intended task. For most normal metals the change in effect over the range of temperatures experienced by Phoenix doesn't seem likely to have any serious effect (to me) see http://www.engineeringtoolbox.com/young-modulus-d_773.html.
Young's Modulus (and the Bulk\and Sheer Moduli which are two other relevant coefficients in terms of overall elastic behavior) only applies within the strain region where Hooke's law applies and that region itself will vary with temperature. I'd be very surprised if the TEGA spring opening mechanisms hadn't been tested at all potential temperature and pressure regimes though so I'd be surprised if that was the case.
I still think it's far more likely that the debris from the previous sample delivery event has found it's way into places that weren't anticipated and what we're seeing is a hinge that is jammed as a result.
Posted by: centsworth_II Jun 24 2008, 02:48 PM
This would not explain the partial opening of oven four's door. So you would be saying that the two door opening problems have two different causes.
Posted by: Bill Harris Jun 24 2008, 03:02 PM
So much for the idea that the springs had sproinged. We've been using latches and springs to open things in a space-environment and that technique has the bugs worked out. It'll be interesting to eventually determine what caused the TEGA door problem.
--Bill
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