The Prototype Segmented Mirror Telescope is a 1.3 m aperture, seven segment telescope, being developed as a technology demonstrator for India’s large optical-IR telescope project. For this segmented mirror telescope, a Shack Hartmann sensor based alignment device has been designed and developed. The device not only precisely captures the segment misalignment but also measures the segment focus error with an accuracy of a few microns and hence helps in the tip-tilt correction and co-focusing of the mirror segments. The device is designed to work primarily in two different modes: the Shack–Hartmann mode and the imaging mode. After completion of the alignment procedure, the final image quality can be checked in the imaging mode. The device is designed in such a way that it also has a provision to conduct the Keck kind of phasing experiment with one pair of mirror segments. To make the device cost effective, only off-the-shelf components are used. The optical design and opto-mechanical analysis of the device were carried out using Zemax and SolidWorks software. Then, the device was realized and its extensive testing was carried out in the laboratory. Here, we have presented the details of the opto-mechanical design and analysis as well as the preliminary results of performance tests conducted in the laboratory.
The segment support system of any segmented mirror telescope is considered to be one of the most critical subsystem. The segment support not only holds the mirror without altering its figure, but also features mechanism which facilitate active alignment of the segments with the help of three linear actuators. We have designed and a developed a segment support system for a proposed prototype segmented mirror telescope (PSMT). The baseline design of the PSMT segment support comprises of nine point axially supporting whiffletree coupled with a moving frame and a central diaphragm for the radial support. Our design uses large number of flexural components including flex pivots which make it friction-less system, requiring no lubrication. In this paper we present the details of our design as well as results of very extensive finite element analysis carried out to explore effect of variable gravity as well as temperature on the performance of the support system. During the course of telescope movement from zenith to horizon, interplay between axial and radial support system has also been studied in great detail. The modal analysis is also carried out to determine different natural frequencies/modes the support system is subjected. Functional and operational aspect of the segment support is also tested by conducting experiments on one fully realized system. The segment support which is primarily designed for 0.5m size PSMT segment can be easily scaled up to 1 m size segment and hence can be used for any large telescopes aimed to utilize segmented primary mirror.
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