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Mars Probe Brings the "Weather Rock" New Respect

Posted by timothy on Tue May 27, 2008 10:32 AM
from the if-tail-is-wet dept.
NASA Space Science
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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Submission: "Weather Rock" a real instrument on Mars P by radioweather (1088475)
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  • It picks winner of any sports game, series, etc., everytime, in advance.

    Yours for only 5 easy payments of $19.95!

    The Sports Bookie Rock.

    Get yours now!

  • AOD (Score:5, Funny)

    by Stanistani (808333) on Tuesday May 27 2008, @10:38AM (#23556901) Homepage Journal
    Fascinating. This may be the first time 'angle of dangle' could be used in an actual scientific context.

  • Don't you hate it when... (Score:5, Insightful)

    by tiedyejeremy (559815) on Tuesday May 27 2008, @10:38AM (#23556903) Homepage Journal
    Don't you hate it when... Simple makes sense?
  • 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?

    • Dowsing rods don't detect anything (Score:5, Informative)

      by CustomDesigned (250089) on Tuesday May 27 2008, @11:24AM (#23557625) Homepage Journal
      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.

      • Re: (Score:3, Insightful)

        by gardyloo (512791)
        Dowsing rods actually do an awfully good job at detecting idiots!

      • I know I "see" something like a flash of light whenever someone turns on a fluorescent light with magnetic ballast in another room.
        And I thought I was the only one who saw light when someone turn on the lights...
  • Why didn't they put in a lightweight weather vane with a small fan? That way they could tell direction and velocity. With the rock you can basically gauge the initial wind, but once it starts swinging in the opposite direction its practically impossible to tell if the deflection is from an opposing wind or merely the pendulum swinging. It becomes even more useless if there are sudden changes in wind speed/direction since it will just seemingly bounce round in random directions none of which are reflective o
    • 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.

    • Re:Why not a weather vane? (Score:4, Interesting)

      by TheRedSeven (1234758) on Tuesday May 27 2008, @10:50AM (#23557101) Homepage
      From TFA:

      The Telltale consists of a gallows that is mounted on the top of the Meteorological Mast of the Lander. The active element of the instrument is an extremely lightweight Kapton tube hanging in Kevlar fibres. Images taken of the instrument will show the deflection of the Telltale due to the wind. A mirror is mounted below the active part to enable better direction information. (My emphasis)
      The wonderful addition of a high-tech "mirror" allows multiple perspectives that would allow you to detect direction. Looks like some overpaid engineer already thought of this.

      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.

    • Re:Why not a weather vane? (Score:5, Interesting)

      by hcpxvi (773888) on Tuesday May 27 2008, @10:50AM (#23557105)
      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.

      • Re: (Score:3, Interesting)

        by dargaud (518470)
        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 [gdargaud.net].

        • Re: (Score:3, Insightful)

          by DerekLyons (302214)
          Because a sonic sonic anemometer requires power, calibration, and computer cycles. A windsock doesn't.
        • 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.

    • A weather vane requires a free moving bearing or bushing which would not do well in a dusty/gritty environment like Mars.
    • Two reasons

      1) Reliability, there is bugger all that can go wrong with a tell tale
      2) Weight, a vane and a fan are going weigh grams more than the tell tale and when sending something to Mars those things count.

      Personally I love this sort of engineering you can almost imagine the meeting

      "We've got 5 grams and we need to tell where the wind is coming from"
      "Weather, vane with a fan?"
      "Nope to heavy"
      "Hang on how about just something hanging down from a stick"

      And thus extensive engineering and testing was born (it

    • Re: (Score:2, Funny)

      by Anonymous Coward
      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...

    • Re:Why not a weather vane? (Score:5, Funny)

      by Scratch-O-Matic (245992) on Tuesday May 27 2008, @11:15AM (#23557501)
      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.

    • Re: (Score:3, Interesting)

      by pz (113803)
      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 wi

    • Re:Why not a weather vane? (Score:4, Interesting)

      by pz (113803) on Tuesday May 27 2008, @11:40AM (#23557883) Journal
      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.

    • Re: (Score:3, Interesting)

      by WebCowboy (196209)

      Why didn't they put in a lightweight weather vane with a small fan?

      Actually a vane and fan is inferior for this particular purpose. This "rock on a string" can be used to determine both direction and intensity of winds just as well, plus it is lighter and mechanically less complex than a vane and fan--important in the very cold and dusty environment on Mars. The rotating parts would more easily wear, freeze or seize up more easily in such an environment.

      With the rock you can basically gauge the initial wind, but once it starts swinging

      If a wind is sustained the rock would not swing. Furthermore sensors and computer analysis of the motion can provide

    • Re:Why not a weather vane? (Score:5, Funny)

      by mazarin5 (309432) on Tuesday May 27 2008, @12:27PM (#23558631) Journal

      but once it starts swinging in the opposite direction its practically impossible to tell if the deflection is from an opposing wind or merely the pendulum swinging.
      Because the motion of a simple pendulum is one of the last great unsolved problems in physics?

  • It's called a 'wind sock' (Score:5, Informative)

    by Chris Burke (6130) on Tuesday May 27 2008, @10:51AM (#23557123) Homepage
    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.

    • Re: (Score:3, Informative)

      by jrumney (197329)
      They're calling it a telltale, which from the description sounds more accurate than windsock, as a telltale is not hollow. Telltales (usually thin strips of nylon, sometimes on smaller yachts just bits of string) are used on the leading and trailing edges of sails to indicate the flow of air over and off the sail.

  • Telltale's (Score:4, Informative)

    by penguinstorm (575341) on Tuesday May 27 2008, @10:53AM (#23557165) Homepage
    Telltales have long been used in sailing. Most sails have some visible.

    http://en.wikipedia.org/wiki/Tell-tale [wikipedia.org]

    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.
    • In case anyone is interested, a telltale in sailing is used to properly shape the sail for smooth airflow over the airfoil created by the sail, rather than for determining the direction or strength of the wind.

  • Martian weather forecasting rock (Score:5, Funny)

    by mikael (484) on Tuesday May 27 2008, @10:58AM (#23557227)
    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
    • 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 was a martian sand storm

      o Rock is levitating - caution: martian sand storm

      o Rock is floating - seriously, you guys, martian sand storm

      o Rock has gone - martian sand storm

  • Can't wait... (Score:5, Funny)

    by slashname3 (739398) on Tuesday May 27 2008, @10:58AM (#23557235)
    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..."

  • Obligatory (Score:3, Funny)

    by FurtiveGlancer (1274746) <furtiveglancer@@@aol...com> on Tuesday May 27 2008, @10:58AM (#23557241) Journal
    Thank you for bringing us this "Telltale tale."
    • 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?
    • 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

    • Re: (Score:3, Informative)

      by trongey (21550)
      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

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