International Journal of Enhanced Research in Science Technology & Engineering, ISSN: 2319-7463 Vol. 2 Issue 7, July-2013, pp: (77-82), Available online at: www.erpublications.com Page | 77 Opto-mechanical design and analysis of a refractive multi element lens assembly for space applications Mayur D Pawar 1 , Bijoy Raha 2 , Chandru B T 3 , Venkateswaran R 4 , Krishna Murthy T 5 , 1 M. Tech. Student (Machine Design), Department Of Mechanical Engineering, EWIT, Bangalore-91 2 OEND, Scientist/Engineer-SD, LEOS-ISRO, Bengaluru-58 3 Asst. Professor, Department Of Mechanical Engineering, EWIT, Bangalore-91 4 Head, OEND, Scientist/Engineer-SG, LEOS-ISRO, Bengaluru-58 5 Group Director, OPG, Scientist/Engineer-G, LEOS-ISRO, Bengaluru-58 Abstract: The objective of this work is to design and analyse the multi element lens assembly for space borne application, in which refractive optical systems are used in remote sensing applications with high resolution optical imaging performance at satellite orbital height of about 600km from earth surface. To achieve such high optical performance it is essential to design highly stiff, thermally and mechanically stable optical mounts for geometrical positioning of the Opto-mechanical system so as to withstand dynamic launch loads and thermal loads during on-orbit conditions. Key words: Micro Yield Stress (MYS), Peak To Valley (PV), Optical Elements, Mechanical Mount, Opto- Mechanical Design. I. INTRODUCTION Opto-mechanical design involves many disciplines such as Material Science, Mechanical design, Optics design, Fabrication and Thermal design aspects. The Opto-Mechanical design deals with Design, Analysis, Fabrication, Assembly and Qualification of the Optical systems incorporating optical components mounted in mechanical housing. In order to ensure consistent optical performance of mounted optical components having surface figure accuracy better than λ/6 (PV), where λ is the reference wavelength. Strain free mounting of optical elements and positioning the components of an optical system relative to each other are the major design considerations in Opto-mechanical design. Both micro- level strain and stress are the major design criteria for Opto-mechanical designs. The space borne optical systems should have sufficient stiffness to withstand rocket launching loads, minimum weight for better agility and requisite thermal properties to ensure minimum displacements, thermal stresses and thermal gradients for thermal loads. Hence, the selection of material and geometry optimization of design is based on strength to weight ratio (E/ρ) & moment to area ratio (I/A) and thermal conductivity to thermal coefficient of expansion ratio (K/α).The performance of optical assembly requires stringent control of dimensional stability, geometrical positioning, alignment accuracies and optical surface deformations against static, dynamic and thermal loads. While designing such optical systems, the designer has to take into account various factors such as manufacturing limitations of the lens and mount, assembly and interface effects, static, dynamic, gravity release, on-orbit thermal and other environmental loads such as vibration, shock etc. Analytical relationships are given for estimating selected important attributes of design such as contact stress due to forces imposed during assembly and temperature change or acceleration. This paper gives the details of Finite element analysis requirements, FEA of lens assembly, performance of lens assembly. II. LENS MOUNTING REQUIREMENTS The following critical requirements are summarized for Lens Mounting.  The Gravity effects must be removed / minimized by the support system for a given size and geometry of the lens.  The reaction forces generated by the support system must exactly balance out the weight of the supported lens acting along gravity vector i.e. this F z = weight of the lens (if gravity vector along Z axis )  All other reaction forces in other degrees of freedom & bending moments must balance out to Zero, i.e. F x, F y, R X, R Y , R z, M = 0  The support system must be semi-kinematic in nature so that lens can be supported on the support system for repetitive testing.