A hardware demonstration has been performed in which a nominally flat, complex aspheric mirror is used to correct the high-order aberrated wavefront error of an off-axis parabolic mirror to 0.5 nm rms. The purpose of the project is to demonstrate the viability of using a static, aspheric optic to correct a telescope wavefront to the degree needed for detection of extra-solar Jovian planets. The demonstration procedure and test results are presented.
The Primary Mirror of the Keck Observatory Telescope is made up of an array of 36 hexagonal mirror segments under active control. The measurement of the relative orientations of the mirror segments is fundamental to their control. The mechanical and electronic design of the sensors used to measure these relative positions is described along with the performance of the sensors under a variety of tests. In use, the sensors will measure relative positions with a resolution of a few nanometers. This resolution and the low noise, drift and thermal sensitivity of the sensors are adequate to stabilize the primary mirror figure to the precision require for optical and infrared astronomy.
Richard Jared, A. Arthur, S. Andreae, A. Biocca, Richard Cohen, Josep Fuertes, J. Franck, George Gabor, Jorge Llacer, Terry Mast, John Meng, Tom Merrick, Robert Minor, James Nelson, M. Orayani, P. Salz, Barbara Schaefer, Chris Witebsky
The ten meter diameter primary mirror of the W. M. Keck Telescope is a mosaic of thirty-six hexagonal mirrors. An active control system stabilizes the primary mirror. The active control system uses 168 measurements of the relative positions of adjacent mirror segments and 3 measurements of the'primary mirror position in the telescope structure to control the 108 degrees of freedom needed to stabilize the figure and position of the primary mirror. The components of the active control system are relative position sensors, electronics, computers, actuators that position the mirrors, and software. The software algorithms control the primary mirror, perform star image stacking, emulate the segments, store and fit calibration data, and locate hardware defects.
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