Stability of materials for use in space-based interferometric missions

Space-based interferometric missions such as SPIRIT, SPECS, TPF, and LISA will take measurements of the universe with unprecedented results. To do this, these missions will require ultra-stable materials and bonding techniques to be used for critical optical components such as optical benches or support structures. As an example, the telescope support structure for the LISA mission must be made of a material that is stable to better than 1 pm/ Hz at 3 mHz and whose length between the primary and secondary mirrors cannot change by more than 1.2 mum over the lifetime of the mission. Although materials such as silicon carbide (SiC) and carbon fiber reinforced polymers (CFRP) have been suggested for this use, they have not been tested to these strict requirements.;The author is part of a group at the University of Florida that is developing a materials research facility capable of testing the stability and strength of materials and bonding techniques for use in space-based interferometric missions. This work describes the techniques used to test the stability of materials at the femtometer level. Results are presented for SiC, Zerodur, a carbon fiber reinforced polymer, Super Invar, and k-180 piezoelectric material. In addition, several bonding techniques are described along with potential uses for space missions. Specific attention is paid to a promising new jointing method known as hydroxide bonding. The bonding method, bonding mechanism, and shear test strengths are presented for several material combinations. During this work, it was found that hydroxide bonding could be used to bond SiC to SiC with significant strength in a simple manner and was chosen to bond a prototype telescope support structure for the LISA mission. Initial results and discussion about further improvements to the design are presented.;Finally, investigations were done to determine the differential phase noise in counter-propagating beams through an optical fiber. Results using a polarizing Sagnac interferometer showed a differential phase noise of ∼5x10 -5 cycles/ Hz at 1 Hz. The experimental setup, noise sources, and results are presented.