Hexapod for Space Telescopes: A Review
Keywords:Hexapod, Space telescope, Thermal actuator, Refocusing mechanism, Stewart platform
Space borne telescopes are subjected to orbital loads like temperature excursion, absence of gravity, moisture
desorbption of metering structure etc, which leads to misalignment of optical system and loss of the optical performance.
Future space based large telescope will be made from number of smaller mirrors, which are aligned together to create a
larger segmented mirror. Due to orbital loads misalignment will occur in these smaller mirrors supported by large
structures and intern this willintroduce aberrations in imaging. Hence, there is a need of some technique which measures
the onboard optical misalignment and corrects it. Wavefront sensing and reconstruction is a technique, which measures
the wavefront and the aberration presents in a wavefront. This technique can be used in space based telescopes to sense
the optical misalignment by measuring an error in wavefront. It provides necessary feedback to the hexapod to restore
optical performance by realignment. Hexapod is a device which provides 6 DOF of the moving plate (platform) relative
to the fixed plate (base), all the six actuators are actuated with computed thermal field.