Telltale

The Telltale wind indicator on PHX is a mechanical anemometer designed to operate on the Martian surface as part of the meteorological package on the NASA Phoenix lander. It consists of a lightweight cylinder suspended by Kevlar fibers and is deflected under the action of wind. Imaging of the Telltale deflection with the SSI allows the wind speed and direction to be quantified

Wind measurements were made with a frequency detemined by how frequently the SSI could take images (down to once every 50 seconds).

The Telltale was designed to be capable of measuring wind speed in two horizontal components: perpendicularly to the SSI camera line-of-sight over the range 1-10 m/s with accuracy of 1 m/s for winds of 1 to 5 m/s and of 20% for winds of 5 to 10 m/s; and along the SSI camera line-of-sight over the range of 2 - 10 m/s with accuracy of 2 m/s for winds of 2 to 5 m/s and of 40% for winds of 5 to 10 m/s.

Source: Telltale Instrument Catalog File