Five-hundred-meter Aperture Spherical radio Telescope

 

Measurement and Control System

There is no rigid structure connecting the FAST reflector and focus. Therefore it requires high-accuracy measurements of their spatial coordinate in a common well-defined reference frame. Besides, all moving parts of the telescope require real-time measurement and reaction control during operations to meet the position accuracy requirement. Various modern measurement technology will be applied to the site exploration, earth work, reflector and feed cabin support, receiver and terminal systems, and the real-time detect and health monitor of the telescope during operation in future. Large dimension, high sampling rate, high accuracy measurement and control is the key points.

We plan to build a reference datum net comprised of 10 datum station with mm-accuracy. There are two most challenging tasks to be accomplished.

(1) Real-time reaction control of the feed cabin: to read the 3-D spatial positions of the feed cabin, four API laser trackers are used to measure 4 follow-up targets in the Stewart platform. Two API laser tracker systems are used to measure the position and attitude of the lower platform, and monitor the control results.

(2) Surface scanning of the reflector: There are more than 2000 nodes, the joining points of the element panels on the reflector, and the number of nodes being illuminated is ~1000. As a plan, nine close-range instrumentations with accurate rotating platforms and digital cameras will be built to scan 1000 control nodes in the illuminated portion of the reflector during observations.

We are also developing control technology to realize the spatial positioning of the receiver in the feed cabin.