Two hot wire probes, respectively vertical and horizontal, were
located
about 10 mm (model scale) above the mirror surface (see
fig. 
).
Depending on the pointing angle of the telescope the speed
measurements from the two hot-wire probes will differ, and the largest
of the two values will approximate the absolute speed seeked.
Both mean (velocity ratio) and rms
(turbulence intensity)
values are given as ratios to the free flow speed.
Figure: Sketch
indicating the location of hot wire probes above the mirror surface. Both
probes were approximately 1 cm from the mirror surface.
Figure: Tap locations on upper and lower surfaces of the mirror
