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The Laser Interferometer Space Antenna (LISA), with its extreme distance measurement requirements (pm over arm lengths of 2.5 million km), imposes many stringent requirements on the laser sources used for the distance metrological measurements. In particular, meeting the frequency noise, power stability and side band phase noise requirements reliably for multiple laser systems over the mission lifetime presents a considerable technical challenge. These constraints demand a robust state-of-the-art laser design and a particular attention to reliability and procurement strategy, which all pose a significant challenge. Relying on its strong metrology expertise, CSEM, Swiss Center of Electronics and Microtechnology, is, in the frame of an ESA activity, upgrading all of the metrology techniques and hardware, used to characterize a previously developed non NPRO laser system for the LISA mission. These metrology systems are the baseline for assessing the performance of LISA mission laser heads, developed by NASA. Novel metrology techniques have been developed to assess the challenging laser head specifications. The measurement of frequency stability requires combining different frequency references to cover the full frequency range spanning over more than 10 decades. The measurement of power stability requires combining several metrology approaches to cover the full frequency range and dedicated development, in collaboration with NASA, to improve the long-term measurement capability. As already demonstrated in the previous CSEM activity, sideband phase noise measurement is very sensitive to the environment and complex to perform. A dedicated and improved test setup has been implemented. After a presentation of the NASA laser head, dedicated testing philosophy approaches, encountered technical challenges and obtained test results are presented.
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