Optical Performance Variation of Slewing Mirror Space Telescope(SMT) in Space Thermal Environment

Slewing Mirror Telescop(SMT) is a subsystem of UFFO(Ultra-Fast Flash Observatory) Pathfinder. SMT has a f/11.4 Ritchey-Chretien telescope of 100mm in aperture. Based on our current understanding for Pre-flight model SMT thermal responses from the thermal-vacuum chamber test, we simulated heat distribution and the structural deformations of FM SMT. We predicted the wavefront error that was subsequently measured by a phase shifting interferometer while the temperature was increased by 5℃. The predicted and resulting SMT FM wavefront error variation are 0.0382 and 0.0369 waves respectively and these tend to satisfy 0.15 waves in system WFE requirement over the operational temperature variation range of 0 ± 7℃. The results prove that SMT is capable of producing the required performance in space orbit environment.s from the thermal-vacuum chamber test, we simulated heat distribution and the structural deformations of FM SMT. We predicted the wavefront error that was subsequently measured by a phase shifting interferometer while the temperature was increased by 5℃. The predicted and resulting SMT FM wavefront error variation are 0.0382 and 0.0369 waves respectively and these tend to satisfy 0.15 waves in system WFE requirement over the operational temperature variation range of 0 ± 7℃. The results prove that SMT is capable of producing the required performance in space orbit environment.2

Structural behavior of the SMT opto-mechanical subsystem

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.2