Bipod flexure for 1-m primary mirror system

Abstract

We present an analytical formulation of the bipod flexure for mounting the 1-m primary mirror in a space telescope. Compliance and stiffness matrices of the bipod flexure are derived to estimate theoretical performance and to make initial design guidelines. We use finite element analysis to optimize the bipod design satisfying the application requirements. Experimental verification is achieved by vibration test with a dummy mirror system.

Analysis on the Isostatic Bipod Mounts for the HERA Mission LIDAR

“…There are two types of conformities that should be followed: radial compliance for axisymmetric mirrors to compensate for thermal expansion mismatch, and tangential compliance to prevent assembly stress from navigating towards the mirror surface. Lateral mirror supports on the edge of the mirror help in fulfilling these compliances [3,4]. Isostatic mounts can be categorized according to the type of flexure element: simple blade flexures, that are used for tangential edge support for small axisymmetric mirrors, and a bipod flexure, which is a combination of two blade flexures forming a triangle [3,4].…”

“…Lateral mirror supports on the edge of the mirror help in fulfilling these compliances [3,4]. Isostatic mounts can be categorized according to the type of flexure element: simple blade flexures, that are used for tangential edge support for small axisymmetric mirrors, and a bipod flexure, which is a combination of two blade flexures forming a triangle [3,4]. Kihm [3] presented a design for a lightweight primary mirror, with pockets in the back surface, and with three square bosses extruded at the edge of the mirror for isostatic mounting.…”

“…In this paper, the isostatic bipod mounts design of PALT is presented. It follows a similar approach to the flexure presented by Kihm [3,4], which means that the apex of the triangle formed by the flexure should point to the center of mass of the mirror to minimize surface distortion [3,4]. Each bipod flexure has a symmetric combination of two tangential blades and the radial blade: tangential blades give tangential compliance, and radial blades give radial compliance to the mirror.…”

“…Each bipod flexure has a symmetric combination of two tangential blades and the radial blade: tangential blades give tangential compliance, and radial blades give radial compliance to the mirror. Thus, when the mirror is accelerated in lateral directions or perpendicular to the mirror's optical axis, the tangential flexures compensate for this effect; however, radial expansion of the mirror due to thermal loads can be compensated for by the radial flexures [4]. The major differences from previous implementations lie in the mirror size and in the isostatic mount bipod mechanical design.…”