Mirror figure control primitives for the Keck Observatory ten meter primary mirror.

摘要

The Keck Observatory primary mirror is comprised of 36 segments from which 216 glass temperatures and 168 measures of relative displacement are continuously read. Mirror figure adjustments are under the active control of 108 adjustable-length actuators, three per segment. We describe our collection method for mirror segment displacement data and glass temperature data and the supplying of individual control signals to the actuator controllers and sensor electronics, both located near each mirror segment, and discuss the mirror's computerized control system. Much of the sense and control electronics is close to the rear surface of the primary mirror. From an historical perspective, we describe the impact of the need to minimize heat sources and cabling, on the communications method used and on its implementation. We conclude with a brief structural overview of the hardware in use to actively maintain primary mirror figure. 4 refs., 5 figs., 1 tab.