1
$\begingroup$

Reading about ping pong ball anemometers I discovered that the Mars Phoenix Lander had an anemometer of this design, and there are images and GIFs of it moving. When imaged from one or two different angles, it gives an estimate of wind velocity and direction. But imaging is a lot of bandwidth and memory (especially back then).

There was also a LIDAR instrument, but I don't know how demanding it was for power, or bandwidth, and if it could be pointed in at least a few directions fast enough to establish the direction of the wind, nor do I know if the direction was important.

After reading Wikipedia's article on Phoenix's Meteorological station I get the idea that they were looking for times when the wind was minimal, so that they could do sample loading without losing the smallest particles due to wind.

Wouldn't a hot-wire anemometer have used much less bandwidth and been easier to read? I think that as long as the air temperature is measured approximately, and certainly the pressure would be available from the weather station, this should work fine.

Also this looks a bit on the heavy side for a payload to Mars, compared to a hot wire, but that's just my perception.

GIF from images transmitted from Mars of the telltale on the Phoenix Mars Lander

above: GIF from images transmitted from Mars. From the The Telltale project page on the Mars Simulation Laboratory. Also archived here.

enter image description here

above: Instrument as delivered to NASA. From the The Telltale project page on the Mars Simulation Laboratory. Also archived here. That's a 45 degree mirror below the telltale providing a simultaneous view from below.

Improve this question
$\endgroup$
9
  • $\begingroup$ I suspect hot-wire anemometers don't work very well at the very low pressure of mars atmosphere. $\endgroup$
    – Uwe
    Commented May 28, 2017 at 8:46
  • 1
    $\begingroup$ Not to mention low density atmosphere that is predominantly CO2. Calibrating a hot wire anemometer for such conditions would have taken some effort. Looking at the 2D movements of a dangling objects would be simpler. $\endgroup$
    – Fred
    Commented May 28, 2017 at 9:04
  • $\begingroup$ @Uwe Why do you think so? Rate of collisional heat loss would scale with rate of collisions ($\sim \rho v$ or $\sim \rho \sqrt{T_{atm}}$) while rate of radiative heat loss would scale as $\sim T_{wire}^4$ so as long as the temperature were not so high that radiative cooling was dominant, I'm thinking that it should be a straightforward, stable, calibrated correction. If I'm wrong, then that would be the basis of a good answer! However I do need to adjust the question wording, since there is a $T_{atm}$ dependence. $\endgroup$
    – uhoh
    Commented May 28, 2017 at 9:13
  • 1
    $\begingroup$ A paper about using hot-wire anemometers at low pressure: enu.kz/repository/2011/AIAA-2011-1166.pdf read bottom of page 2. $\endgroup$
    – Uwe
    Commented May 28, 2017 at 9:46
  • 3
    $\begingroup$ According to the Wikipedia page, hot wire anemometers are fragile, using wire thickness on the order of micrometers. That might make it difficult to make one robust enough to survive launch and landing. $\endgroup$
    – Hobbes
    Commented May 28, 2017 at 9:49

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.