SPRINT for WFAO systems

TL;DR

This paper introduces SPRINT, a method for accurately calibrating and tracking the alignment parameters in wide field adaptive optics systems, crucial for stable and optimal system performance.

Contribution

The paper extends the SPRINT strategy from SCAO to WFAO systems, addressing the complexities of multiple WFSs and DMs for improved calibration accuracy.

Findings

SPRINT effectively monitors DM/WFS mis-registrations in WFAO systems.

Simultaneous and sequential identification approaches are evaluated.

Results demonstrate enhanced stability and performance in adaptive optics systems.

Abstract

The calibration of future wide field adaptive optics (WFAO) systems requires knowledge of the geometry of the system, in particular the alignment parameters between the sub-apertures of the wavefront sensors (WFS), pupil and deformable mirror (DM) actuator grid. Without this knowledge, closed-loop operation is not possible and the registration must be identified with an error significantly smaller than the sub-aperture size to achieve the nominal performance of the adaptive optics system. Furthermore, poor accuracy in this estimation will not only affect performance, but could also prevent the closed loop from being stable. Identification is not trivial because in a WFAO system several elements can move with respect to each other, more than in a SCAO system. For example, the pairing of the sub-aperture and the actuator grating on a DM conjugated to an altitude different from 0 can depend on the size of the pupil on the WFS, the exact conjugation of the DM, the position of the guide star and the field rotation. This is the same for each WFS/DM pair. SPRINT, System Parameters Recurrent INvasive Tracking, is a strategy for monitoring and compensating for DM/WFS mis-registrations and has been developed in the context of single conjugate adaptive optics (SCAO) systems for the ESO Extremely Large Telescope (ELT). In this work, we apply SPRINT in the context of WFAO systems with multiple WFSs and DMs, investigating the best approach for such systems, considering a simultaneous identification of all parameters or subsequent steps working on one DM at a time.