Measuring the Effective Coefficient of Thermal Expansion of the LISA Telescope Structural Thermal Model. (Presented by Alex Weaver)

The Laser Interferometer Space Antenna (LISA) will be sensitive to gravitational waves (GW) with frequencies in the band from 10 µHz to 1 Hz. This will allow detection of GW sources that will be undetectable by ground based GW detectors and pulsar timing arrays. LISA is a joint ESA-NASA mission, with NASA responsible for contributing the 6 telescopes used for transmitting and receiving laser beams between the 3 spacecraft (SC). The telescopes will thus measure distance from SC to SC. To meet the desired strain sensitivity in the LISA band, the telescope's optical pathlength changes due to thermal fluctuations must be negligible. This requirement imposes strict limits on the Coefficient of Thermal Expansion (CTE) of the telescope structure. We at University of Florida are in the process of testing the effective coefficient of thermal expansion (CTE) of the structural thermal model of the LISA telescope, to see if this early progenitor of the telescope may already meet mission CTE requirements. Our presentation addresses the testing we have done so far, problems encountered that are important to any high-precision length measurement work, and how such obstacles have been or will be overcome. Finally, we go over preliminary results so far and address their authenticity.