A Prototype of Fast-steering Secondary Mirror (FSMP) for the Giant Magellan Telescope (GMT) has been developed by the consortium consisting of institutes in Korea and the US. In 2014 the FSMP development was finalized by combining the two major sub-systems, the mirror fabricated and the mirror cell with the tip-tilt control parts. We have developed an assembly procedure in which potential difficulties, such as handling without contacting mirror surface, and optimizing bonding process, have been resolved. Supporting jigs were produced, and optimized bonding techniques have been developed. The assembled FSMP system was installed in a test tower, and stability of the system were checked. Performance of the FSMP system will be evaluated in static and dynamic environments for the validation of the FSMP system operation as the future works.
We revisit the method of synthetic wavelength interferometry (SWI) for absolute measurement of long distances using the radio-frequency harmonics of the pulse repetition rate of a mode-locked femtosecond laser. Our intention here is to extend the nonambiguity range (NAR) of the SWI method using a coarse virtual wavelength synthesized by shifting the pulse repetition rate. The proposed concept of NAR extension is experimentally verified by measuring a ∼13-m distance with repeatability of 9.5 μm (root-mean-square). The measurement precision is estimated to be 31.2 μm in comparison with an incremental He–Ne laser interferometer. This extended SWI method is found to be well suited for long-distance measurements demanded in the fields of large-scale precision engineering, geodetic survey, and future space missions.