Mechanical Jitter Measurement Results for Large Ground-Based Telescopes

摘要

In a major effort to understand limitations on the performance of ground-based optical telescopes and gimbals, the Air Force Research Laboratory (AFRL) and a contractor support team measured the vibration and jitter of several large telescopes. These measurements were conducted over a ten-year period with high bandwidth accelerometers, angular position sensors, and seismometers attached to various locations on the telescopes, mounts, and bases. Measurements were taken over a 0.1 to 1000-Hz bandwidth and at angular tracking velocities between 0.001 and 18.5 degrees per second, single-axis. Jitter power spectral densities (PSD) and root-mean-square (rms) values and ranges were determined for both dynamic tracking and quiescent condition. Many telescopes exhibited near-noise-floor level jitter (i.e., about 10 nanoradians rms) under some conditions in certain bandwidth ranges. Under very high-speed single-axis tracking conditions (i.e., 10.5-18.5 degrees per second), jitter often rose to several micro-radians rms. This paper presents and discusses the overall mechanical jitter measurement results obtained for five telescopes with emphasis on two 3.5-meter aperture-class high-tracking rate instruments.