VST telescope primary mirror active optics actuators firmware implementation

Abstract

The VST (VLT Survey Telescope) is a 2.6 m class Alt-Az telescope in installation phase at Cerro Paranal in Northern Chile, at the European Southern Observatory (ESO) site. The VST is a wide-field imaging telescope dedicated to supply databases for the ESO Very Large Telescope (VLT) science and to carry out stand-alone observations in the Ultraviolet to Infrared spectral range. The VST is provided with an active optics control system to actively compensate the optical aberrations; it is based on 84 actuators controlling the shape of the primary mirror and a hexapode for secondary mirror positioning. The present paper focuses on the implementation of the microcontroller programming firmware for the Primary Mirror Actuators Electronic Control Board. The most relevant problems encountered during the implementation of this real time multitasking distributed control application are described; optimization problems due to low performing hardware platform, not provided with operating system, are also reported. Several described topics are applicable to other distributed control systems, requiring closed loop control system and communication capability with a higher level computer.