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.
To cater the need of growing astronomical community of India, there is a proposal to install 10-12m size optical-NIR telescope, equipped with state of the art back-end instruments . A telescope of this size is possible only, when primary mirror is made of smaller mirror segments. In order to get acquainted with segmented mirror telescope technology, at Indian Institute of Astrophysics Bangalore, we have initiated a project to develop a small prototype telescope made of small mirror segments. The proposed prototype telescope will use seven hexagonal mirrors, which will be supported by simple mirror support assembly and driven by indigenously developed voice coil based actuators. We also plan to make use of in-house developed inexpensive inductive edge sensor, which can precisely sense inter-segment relative displacement. The telescope mount is supposed to be Alt-Az and secondary mirror will be supported by trusses made of steel. The primary axes like elevation, azimuth and field de-rotator will be driven by direct drive motors. Though the primary objective of this telescope is to demonstrate the segmented mirror technology, however, we have designed the telescope in such way that it can also be used to a few dedicated science cases. The telescope is planned to be installed at Hanle, Ladakh India which is also a potential site for India's large telescope project. In this paper, we will present the progress made in opto-mechanical design as well development of other sub-systems required for the PSMT. The prototyping effort is one step toward realization of a large telescope in India and it is expected to be completed in two years period.
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