PERSEE: Experimental results on the cophased nulling bench

TL;DR

The PERSEE bench demonstrates nanometric phase control and nulling interferometry techniques crucial for space-based exoplanet characterization, achieving high stability and preparing for future missions.

Contribution

This work presents the first experimental validation of cophased nulling interferometry with nanometric precision, including the development of a Kalman filter for disturbance rejection.

Findings

Achieved 0.22 nm rms in OPD and 60 mas rms in tip/tilt in simplified setup

Obtained monochromatic null of 3E-5 stabilized at 3E-6

Demonstrated disturbance rejection with Kalman control law

Abstract

Nulling interferometry is still a promising method to characterize spectra of exoplanets. One of the main issues is to cophase at a nanometric level each arm despite satellite disturbances. The bench PERSEE aims to prove the feasibility of that technique for spaceborne missions. After a short description of PERSEE, we will first present the results obtained in a simplified configuration: we have cophased down to 0.22 nm rms in optical path difference (OPD) and 60 mas rms in tip/tilt, and have obtained a monochromatic null of 3E-5 stabilized at 3E-6. The goal of 1 nm with additional typical satellite disturbances requires the use of an optimal control law; that is why we elaborated a dedicated Kalman filter. Simulations and experiments show a good rejection of disturbances. Performance of the bench should be enhanced by using a Kalman control law, and we should be able to reach the desired nanometric stability. Following, we will present the first results of the final polychromatic configuration, which includes an achromatic phase shifter, perturbators and optical delay lines. As a conclusion, we give the first more general lessons we have already learned from this experiment, both at system and component levels for a future space mission.