Characterizing dimensional stability of the LISA telescope at the University of Florida*

LISA, the future space-based gravitational wave observatory, will form a constellation made of three spacecraft, separated by 2.5 Gm in a triangular formation in a heliocentric orbit. Laser links between the three spacecraft sense the position of free-falling test masses housed inside them to detect a passing gravitational wave. Along each laser link, afocal telescopes send and receive light between the two spacecraft after magnifying it 134 times. In the current performance models, the telescopes are allotted a length noise budget of 1 pm/√Hz.u_OMS in the 0.1 mHz to 0.1 Hz band, where u_OMS provides the frequency dependence, and μm-level overall length change over the mission duration. The telescopes are a NASA deliverable and the current design uses a combination of four mirrors with a 300 mm primary mirror and an overall length of 1 m. Dimensional stability measurements of the LISA telescope Engineering Development Units will be conducted at the University of Florida starting late 2022 as a part of the effort to demonstrate technology readiness level 6. This presentation will give an overview of the technology development being undertaken by our group and the progress made so far towards measuring the dimensional stability of the LISA telescope.