STRAP for the VLT instruments

Optimal removal of tip-tilt or image motion is essential for Adaptive Optics. The tilt loop residual jitter considerably affects the performance of the AO, given the high noise propagation coefficients of this term. Therefore we have dedicated efforts for the development of a state-of-the-art servo-loop with optimized sensor and loop-control strategies. The System for Tip-tilt Removal with Avalanche Photodiodes (STRAP) is being tested and will be implemented in a number of VLT instruments. It is compliant with the ESO VLT standards in hardware and software. We report here the rationale and a description of STRAP in its components and subsystems.