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Mars Probe Brings the "Weather Rock" New Respect
radioweather writes "What looked to casual observers like a malfunction, a dangling wire with
something on the end, seen in the
first photo of
the meteorological mast on NASA's
Phoenix Mars Lander,
actually
turned out to be the real instrument. Surprisingly, it is much like the
novelty 'weather rock' seen as a novelty gag around the world. The instrument
called the 'Telltale'
is described as a 'passive wind indicator' and uses an extremely lightweight
Kapton tube hanging in Kevlar fiber. Images taken of the instrument will show
the deflection of the Telltale due to the Martian wind."
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Fascinating. This may be the first time 'angle of dangle' could be used in an actual scientific context.
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Don't you hate it when... Simple makes sense?
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Simon and Garfunkle fans think.. The answer my friend is blowing in the wind...
Wonder if they included some good old fashioned Dowsing Rods to find water too?
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It definitely wins in the durability department. Dust is a real problem on mars, so wherever that weather vane pivots would have to be sealed up pretty tight.
When you're sending something into orbit or further, payload weight is a concern. Cutting weight, moving parts, and simplifying things is generally a good idea on this sort of thing.
Remember that the surface air pressure on Mars is very small compared to on Earth. So you need a much lighter and more delicate instrument for the air to be able to move it. Anything resembling a traditional weather vane would probably not respond to the tenuous Martian breezes. Even if it worked at first, it might well get stuck after the first of those Martian dust storms blew dust into its pivot. Disclaimer: Yes I am a meteorologist. No, I have not been to Mars or worked on any instrument that went there.
And they already had enough respect as a simple form of wind indicator. You may have seen one at an airport, for example. It's not a weather rock.
See, the point, or "joke" as it were, of the weather rock is that it can't actually tell you anything you wouldn't have already known due to your own senses. "If it's wet it's raining, white it's snowing, bouncing and there's an earthquake." But you could tell all those things without the rock... get it?
A wind sock isn't very sophisticated, but it tells us things that wouldn't have been as apparent without it.
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So, of course, they will collect both angle of dangle (azimuth) AND degree of dangle (intensity), both of which vary over time and circumstances. I just don't want to know what they are using for the low-budget ground based simulator. "No Jim, lay back down. Your shift isn't over."
Invenio via vel creo
Telltales have long been used in sailing. Most sails have some visible.
http://en.wikipedia.org/wiki/Tell-tale
That they are incredibly rudimentary and primitive does not diminish their usefullness, provided they're used for what they're meant for. They're not going to predict anything, for example.
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Martian weather forecasting rock
o Rock has dust on it - there has been a martian sand storm
o Rock is swaying back and forth slighly - a martian sand storm is brewing
o Rock cannot be seen - there is a martian sand storm
o Rock is white - there is frozen water on Mars
o Rock is levitating - There is a UFO with an anti-gravity beam
o Rock is floating - Rock is in orbit around planet
o Rock has gone - UFO has been here and removed rock
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I can't wait for the first manned landing with the first weather report from Mars. "Well it looks kind of windy, hold on, let me take my glove and helmet off so I can lick my finger and hold it up to get a measurement of what direction the wind is blowing...." "POOF!" "ARRRGGGGGG!"
"Mars base, this is Houston, over"
"Mars base, this is Houston, over"
"Damn, I think we lost another weatherman..."
Thank you for bringing us this "Telltale tale."
Invenio via vel creo
well, the rock can tell you if it is raining outside, foggy, and cold...all from the rocks tactile interface...
raining, rock is wet
foggy, hard to see the rock
cold, rock has ice on it...
That's why I read Slashdot, so I can find innovative and workable solutions that were dreamed up after five minutes of consideration, rather than wasting time observing and learning about the decades-long efforts of a bunch of idiot engineers who have no friggin idea how to design, launch, navigate, land, and operate an interplanetary exploration robot.
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Great, Now make your nice lightweight fragile weathervane survive 9g's of reentry and almost that amount on launch, plus numerous bumps at various times in the mission.
Touchdown on the Mars Surface was 5 miles an hour. How hard could it be. Now, crash your Toyota into a wall at 5 MPH and you might find that the 5 MPH bumpers really only work at 4.95 MPH. Oops.
It's easy to make a lightweight weathervane. It's hard to make a lightweight weathervane, get it to Mars, and still have it in working order.
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No, no, no:
If the rock is missing: Martians
To the best of my ability to read, we just spent a few million dollars so that we could learn the direction the wind was blowing. At one point. On a rock. A rock very, very far away from here. Where no humans fly, boat, or do anything else which benefits in the slightest from wind directional data.
Except, you know, that whole "understanding the environment of Mars" which benefits quite a bit from knowing about the wind. Sure it's only one location. On the other hand, it will be the only measurement we've ever had and thus a substantial increase in knowledge. They could have spent more on more sophisticated devices, compromising the mass (and dollar) budget, if you really wanted to.
It's hard for me to imagine how you could approve of the overall $420 million project, yet disapprove of this simple, lightweight, and relatively cheap instrument. If you're expecting anything discovered by the Phoenix to have a direct impact on sailing, boating, or any other thing we do here on earth, well, it's possible it will happen eventually, but don't hold your breath. So is it the entire concept of investigating other planets in our solar system that bothers you? Or is it really just the unsophisticated wind indicator?
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A dowsing rod doesn't actually detect anything (even according to practitioners) - it is simply a device to magnify subconscious body language of the operator. The theory is that the human operator detects water via poorly understood senses below conscious awareness. Some dowsers don't bother with the rods, claiming to have trained themselves to become more aware of these senses.
I know I "see" something like a flash of light whenever someone turns on a fluorescent light with magnetic ballast in another room - so I don't think the idea of additional senses is completely crazy.
Are you kidding?
On the off chance you are not: the telltale is but one tiny instrument among many others that are much more sophisticated. A freebie, if you will. The vehicle is a very complex, self-contained geological lab, including:
+ Robotic Arm
+ Robotic Arm Camera
+ Mars Descent Imager
+ Meteorological Station
+ Surface Stereo Imager
+ Microscopy, Electrochemistry, and Conductivity Analyzer
Evil is the money of root.
Design choices:
(a) tell tale: simple; robust to launching forces; reliable; lightweight; works well as long as winds are relatively constant; works poorly if winds are turbulent; gives wind speed AND direction
(b) weather vane: has moving parts including bearings that require protection from the elements; delicate structure that needs to be made robust to launching forces; heavier than tell tale; works well in any winds, although the mass of vane averages, and therefore can mask, turbulence; unless paired with anemometer (those spinning things), only gives wind direction
I'm betting that the fine engineers at NASA who are working within parameters like keeping weight down to absolute minimum, not being able to repair anything at Mars, wanting something that might potentially work for years to come, and not knowing what the range of winds they might encounter would be making a pretty good decision in selecting a tell tale style design.
But what do I know? I'm just a guy who was at Caltech for graduate school and knew people who worked at JPL.
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Quite difficult, but it is being planned...
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The kapton tube does not swing in response to wind, it just deflects. The stronger the wind, the more it deflects. Imagine that it's a spring. Ever seen a car's radio antenna flex on the highway? Same idea.
Insects use exactly the same sort of mechanism to detect gentle air movements. This is one reason it's so hard to catch a fly with your hand when the fly has landed somewhere: the air currents generated by your comparatively large and slow-moving hand are easily detected by the fly.
Put my fist through my alarm clock with its ding-dong death inside my ear. - The Blackjacks.
This is a great experiment. Please re-read the paper you linked. The telltale was selected as a budget-friendly alternative to other wind measurement instruments. It's a very simple and reliable tool that can provide valuable data. It also does the job without using the lander's valuable battery power.
Recording wind direction and relative speed allows for some basic meteorology. With some calibration it can even provide absolute wind speed. It also can be used to determine local wind conditions before deploying other experiments that might be affected by high winds in a particular direction.
You want the government to deliver results? It did.
PS: Your windsocks, while maybe not of practical use to most third graders, are still used at airports around the world to provide critical wind data to pilots.
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Fnord.
I wonder why they don't use a sonic anemometer: precise, works in any conditions and at any wind speed, no mechanical parts and it can take fast readings several times per second to measure turbulence. Yes, I've operated one in Antarctica.
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Because a sonic sonic anemometer requires power, calibration, and computer cycles. A windsock doesn't.