NOVEL METROLOGY SYSTEM FOR VERY LARGE DEPLOYABLE OR SEGMENTED ULTRASTABLE TELESCOPE EXPRO+

Objective: To develop a real-time in-orbit optomechanical metrology system enabling very large segmented or distributed aperture telescopes and their in-orbit active correction and control.Description: In 2040, progress in astro architecture and in-orbit manufacturing and integration could enable the affordable construction of very large telescopes based on either filled apertures with a large number of segments or sparse sub apertures with large numbers of distributed mirrors. These very large telescopes have the power to unlock revolutionary leaps in both Astrophysics and Earth observation thanks to their extreme resolution and collecting power. This activity targets future missions in those domains. This activity focuses on the metrology system at the core of the opto-mechanical architecture of those very large telescopes. For such telescopes to function properly, all main elements of the optical system (primary mirror segments of distributed sub apertures, M2 and other mirrors, focal plane instruments entrance interfaces) need to be extremely accurately located over large distances in order to control and correct their position via an active correction loop. Several technological solutions for sensors have been envisaged (laser truss, interferometric sensors, videogrammetry...) but their technological maturity, space implementation and organisation in a coherent metrology system interfacing with a correction loop needs to be developed. This activity encompasses the following tasks: - Review of current state-of-the-art metrology systems for large telescopes and requirements of active correction chains. - For both segmented and distributed aperture cases, study of novel metrology sensors for space applications and metrology system for ultra large telescopes allowing to control the optomechanical structures and components within the range of an active correction chain. This metrology system shall allow for combination of different technological bricks in order to address the different ranges necessary to accurately sense the position and orientation of the different optomechanical key elements. - Development of a breadboard and related data processing and software demonstrating the adequacy of such a metrology system in terms of accuracy and range. - Roadmap for the development of a full-scale metrology system based on the concept solution found.