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LISA (Laser Interferometer Space Antenna) mission objective is to detect low frequency gravitational waves from space, opening a new era in astronomical science observations. Driven by ESA, the mission relies on strong partnerships with international agencies and scientific laboratories. The French instrument contribution to the LISA mission is managed by CNES with the support of French institutes such as APC (Astroparticule et Cosmologie), ARTEMIS, CEA-IRFU, LT2, L2IT, CPPM, LPC Caen and LMA. The French instrument contribution oversees the definition and realization of the ground performance testing of the optical metrology system (OMS), which is the metrological heart of the MOSA instrument aboard LISA. In this frame, end-to-end performance tests of the OMS will be performed in CNES facilities.
This paper presents the OMS test setup definition and its main thermal engineering constraints. The LISA mission requires a drastic thermal stability and a unique requirement on thermal noise filtering over the frequency range 1mHz – 1Hz. For this performance test, the optical assembly and electronic units are separated into two vacuum chambers to minimize perturbations. In the optical chamber, an optical stack composed of the Optical Bench (OB), the Beam Simulator (BSIM) and the Test Mass Simulator (TMSIM) is integrated. The OB is provided by ESA and is the heart of the system where interferometric measurements are performed. The BSIM is provided by APC and simulates the laser source coming from a distant satellite as well as the presence of a second MOSA. The TMSIM is provided by CEA and simulates the gravitational reference sensor. The electronic chamber welcomes four electronic boxes, including the LASER provided by NASA.
The modelling of the frequential domain temperature levels now needs to be confronted with real measurements. A first thermal characterization test of the setup, without any critical hardware, was conducted in 2026. The goal of this test is to measure the noise levels inside the optical chamber and demonstrate the ability to predict correctly the thermal noise propagation. This paper presents the setup and the results of this first thermal characterization test.