Development of an Optical Read-Out System for the LISA/NGO Gravitational Reference Sensor: A Status Report.

I-80126. INAF OACN, Salita Moiariello 16, Napoli, Italy, I-80131. Abstract. The LISA group in Napoli is working on the development of an Optical Read-Out (ORO) system, based on optical levers and position sensitive detectors, for the LISA gravitational reference sensor. ORO is not meant as an alternative, but as an addition, to capacitive readout, that is the reference so lution for LISA/NGO and will be tested on flight by LISA-Pathfinder. The main goal is th e introduction of some redundancy with consequent mission risk mitigation. Furthermore, the ORO system is more sensitive than the capacitive one and its usage would allow a significant relaxation of the specifications on cross-couplings in the drag free con trol loops. The reliability of the proposed ORO device and the fulfilment of the sensitivi ty requirements have been already demonstrated in bench-top measurements and tests with the four mass torsion pendulum developed in Trento as a ground testing facility for LISA-Pathfinder and LISA hardware. In this paper we report on the present status of this activity pre- senting the last results and perspectives on some relevant a spects. 1) System design, measured sensitivity and noise characterization. 2) Possi ble layouts for integration in LISA/NGO and bench-top tests on real scale prototypes. 3) Search for space compat- ible components and preliminary tests. We will also discuss next steps in view of a possible application in LISA/NGO.