Persee : a nulling demonstrator with real-time correction of external disturbances [2008]

Abstract : Nulling interferometry is one of the most promising methods to study habitable extrasolar systems. Several projects, such as Darwin, TPF, Pegase, FKSI or Aladdin, are currently considered and supported by R&D programs. One of the main issues of nulling interferometry is the feasibility of a stable polychromatic null despite the presence of significant disturbances, induced by vibrations, atmospheric turbulence on the ground or satellite drift for spaceborne missions. To reduce cost and complexity of the whole system, it is necessary to optimize not only the control loop performance at platform and payload levels, but also their interaction. In this goal, it was decided in 2006 to build a laboratory demonstrator named PERSEE (Pegase Experiment for Research and Stabilization of Extreme Extinction). PERSEE is mostly funded by CNES and built by a consortium including CNES, IAS, LESIA, OCA, ONERA and TAS. After a definition phase in 2006, the implementation of the sub-systems has now begun and the integration in Meudon near Paris by GIS-PHASE (LESIA, ONERA and GEPI) is planned in 2008. This paper details the main objectives of PERSEE, describes the definition of the bench, presents the current status and reports results obtained with the first sub-systems. Nulling interferometry is one of identified methods to study habitable extrasolar systems. In this context, several space-based projects have been proposed such as Darwin or its demonstrator Pegase. During the Pegase phase 0 study in 2005, CNES oriented its work towards a reduction of cost and complexity which are major issues in this kind of systems as shown by the recent results of the Cosmic Vision selection. A good understanding of the free flying requirements and their correct mitigation between the payload and the spacecrafts is a key point to achieve successfully such missions. The goal is to reduce as much as possible the constraints applying on the spacecrafts and rely on a very efficient active payload. We decided to study this question from an experimental point of view, coupling a nulling interferometer derived from the state of the art of nulling interferometry breadboards (MAII, Synapse) with a GNC simulator able to introduce realistic perturbations in the set-up. A laboratory breadboard, named PERSEE (Pegase Experiment for Research and Stabilization of Extreme Extinction), was decided in 2006 and funded by CNES R and D. It will be built in Paris at LESIA by a consortium including CNES, IAS, LESIA, OCA, ONERA and TAS. After a definition phase in 2006, the E-mail : Ferderic.Cassaing@onera.fr 1 implementation of the sub-systems now begins and the integration is planned in 2008. The main goal is the demonstration of a stable (10 h) polychromatic null in the 1.65-3.3ìm band with a 10-4 mean rejection rate and a 10-5 stability despite the introduction of realistic perturbations.

Keywords : Interferometry, fringe tracking...