In this paper, a new type of calibration mechanism based on worm drive is presented for a space telescope. This calibration
mechanism based on worm drive has the advantages of compact size and self-lock. The mechanism mainly consists of
thirty-six LEDs as the light source for flat calibration, a diffuse plate, a step motor, a worm gear reducer and a
potentiometer. As the main part of the diffuse plate, a PTFE tablet is mounted in an aluminum alloy frame. The frame is
fixed on the shaft of the worm gear, which is driven by the step motor through the worm. The shaft of the potentiometer is
connected to that of the worm gear to measure the rotation angle of the diffuse plate through a flexible coupler. Firstly, the
calibration mechanism is designed, which includes the LEDs assembly design, the worm gear reducer design and the
diffuse plate assembly design. The counterweight blocks and two end stops are also designed for the diffuse plate assembly.
Then a modal analysis with finite element method for the diffuse plate assembly is completed.