VST primary mirror active optics electronics

The VLT Survey Telescope (VST), a telescope with a 2.6 m. primary mirror designed and implemented by I.N.A.F. in cooperation with the European Southern Observatory (ESO), is provided with an active optics system to correct the optical aberrations due to polishing imperfections, misalignments, thermal and gravity reasons. For the primary mirror, a distributed control system is required to impose the desired force values in a sufficient number of points to maintain the optimal shape in different positions of the altitude axis. The forces are applied by means of 84 electro-mechanical actuators, provided with an electronic Primary Mirror Actuator Control Boards (M1ACB). This paper focuses mainly on the hardware electronics and is referred to the control system new version, designed in 2007, whose implementation is in progress. The new design has taken into account all the experience done on the system previous version, solving all the encountered problems of functionality and reliability.