Structural behavior of the SMT opto-mechanical subsystem

Abstract

We report the current understandings of the structural behavior and of the resulting optical performance variation for the Slewing Mirror Telescope (SMT) opto-mechanical subassembly of the UFFO-pathfinder instrument. Two SMTs - i.e. pre-flight (PFM) and flight (FM) models - have been built as of today and were subjected to vibration tests simulating its launch environment. The input vibration spectrum is sine vibration, random vibration, shock and we confirm that the structural integrity of PFM and FM SMTs remained intact from visual inspection. In particular, CMM measurements for PFM SMT before and after the vibration tests revealed that the primary-secondary mirror alignment is changed by 0.20mm in decenter x, -0.01mm in decenter y, –0.19mm in defocus, -0.61° in tilt x and 0.26° in tilt y. However, such degree of misalignment would result in the optical performance variation of 30.2nm rms(0.048 waves) in WFE that is well within the performance requirement(0.15 waves). The technical details of measurements and the analysis are presented together with the results and implications.-flight (PFM) and flight (FM) models - have been built as of today and were subjected to vibration tests simulating its launch environment. The input vibration spectrum is sine vibration, random vibration, shock and we confirm that the structural integrity of PFM and FM SMTs remained intact from visual inspection. In particular, CMM measurements for PFM SMT before and after the vibration tests revealed that the primary-secondary mirror alignment is changed by 0.20mm in decenter x, -0.01mm in decenter y, –0.19mm in efocus, -0.61° in tilt x and 0.26° in tilt y. However, such degree of misalignment would result in the optical performance variation of 30.2nm rms(0.048 waves) in WFE that is well within the performance requirement(0.15 waves). The technical details of measurements and the analysis are presented together with the results and implications.