Miniaturization of the Rafter optical design for cubesat environment

RAFTER (Ring Astrometric Field Telescope for Exo-planets and Relativity) is a TMA telescope concept aimed at astrometric missions, and providing a wide FOV and high optical response uniformity over an annular region around the optical axis. This paper describes and analyzes the process of miniaturization and implementation of this idea into a Cubesat for technology demonstration purposes, and to evaluate its feasibility by analysing the performance and challenging aspects of different designs, calculating their mechanical and thermal tolerance sensitivity. We outline the critical aspects of the payload that can be tested and optimized in the framework of a dedicated CubeSat mission, in order to demonstrate the enabling technological contributors crucial to the development of a future larger scale mission. We present the results of tolerance analyses based on the inverse sensitivity of optical elements. These tolerances are then used as input for a Monte Carlo test to verify the overlapping effects given the multiple degrees of freedom. The results are presented for different sizes of the optical instrument, and a discussion on imaging capabilities for various instrument sizes is proposed. A configuration proposal is then developed: this involves mounting the optical elements into two groups. Tolerance analysis between the positions of these two groups is then conducted, and the results are compared to the scenario in which all mirrors are free to move according to all their degrees of freedom.