Development of a Robotic Laser Tracker Metrology System for the CCAT Telescope
Mentor:Steve Padin, Senior Research Associate, California Institute of Technology
CCAT is a 25-meter diameter submillimeter telescope that will measure the history of star formation in the universe. The telescope has an active surface of 162 actuated segments, which will constantly adjust the surface profile to correct thermal and gravitational deformations. The initial alignment of the segments will be achieved using a laser tracker, requiring that a retroreflector target be placed at approximately 1000 locations on the surface. We have designed, prototyped, and tested a robot to transport the retroreflector and position it appropriately. As the robot navigates along the telescope's primary surface, it uses its heading and tilt to determine its position within a few centimeters. At each location, the retroreflector is oriented towards the laser tracker and then set down on the surface. The distance and angle measurements collected by the laser tracker allow the surface profile error to be measured and adjusted to 50 microns. This metrology system results in a surface that is accurate enough for a final wavefront measurement using a celestial source.