Control window of the servo loop. The horizontal green bar shows the flux on the PSDs (it becomes red if the flux is too low). The red point is the position of the photocenter on the PSDa (NE) and PSDb (NW). The yellow cross is the reference point: the servo loop brings back the red point toward this position. Then, the metrology gondola is stabilized around a fixed position. The scale is in microns on the PSD. On these zooms each PSD has a field of view of 18   mm at the metrology gondola level. Other technical windows used to adjust the PID (K_p, K_I, K_d) parameters or to create a matrix of interaction and the reference point are not displayed here. The “position treuil” (motorized winches positions) at the top of the window are used only for manual control.