Specify the wind-loading flexure of the telescope.

Arguments:

Double twind_flex

The

Example:

The following command tells the control system that a positive tail wind of tail_wind mph, makes the dish point tail_wind²*0.0000546 degrees lower than reported by the elevation encoder.

  cal_wind_flexure 0.0000546

Context:

Empirically it has been found that to peak up on a pointing source, one needs to point a bit higher in elevation than usual, when there is a tail wind. It isn't known what causes this. One possibility is that the wind-load on the more exposed top half of the dish flexes the upper half of the dish down a bit. The shift in elevation appears to be proportional to the square of the tail-wind speed, which means that it is proportional to the wind-load force, as one might expect for a flexure term.

Note that the tail-wind is the wind blowing perpendicularly onto the back of the dish. Since the weather station reports the azimuth from which the wind is coming, whereas the telescope azimuth refers to where the telescope is pointing, the tail wind is given by:

  tail_wind = wind_speed * cos((telescope_azimuth-180) - wind_azimuth)