GBT Metrology System

For the past several years, work has been underway on various aspects of a metrology system for the Green Bank Telescope. The most significant instrument developed by the Metrology group has been a Laser Rangefinder designed to measure the 100 meter diameter steel structure in near real time in order to generate pointing and surface corrections in the face of thermal and gravitational distortions. The instrument can measure range with an accuracy of better than 100 µm for ranges up to 200 meters and is capable of measuring five ranges per second by means of a beam steering mirror. Accuracies of better than a millimeter have been demonstrated at kilometer ranges.

Several other measuring instruments are described here.

	The Rangefinder	A description of the rangefinder and the early measurements and evaluation.
	The Panel Experiment	A description of an application of three rangefinders in a full scale demonstration of their use in controlling the Active Surface of the GBT.
	Rangefinder Software	A listing of rangefinder software manuals.
	Calibration Range	A description of the indoor range that is used for the calibration of the rangefinders.
	140 Foot Experiment	A description of the ongoing experiment at the 140 Foot Telescope involving the use of four rangefinders tracking a moving target on the back-up structure of the 140 Foot Telescope.
	The Panel Setting Tool	A description of a tool that has been developed to initially set the panels on the GBT to a high precision.
	The Laser Ranging System: A Bibliography	A history of the development of the GBT Metrology system to date.

Comments or Problems:

• Please direct any comments regarding content to John Payne, jpayne@nrao.edu
• Regarding matters of style, please direct all comments to Ramón E. Creager, rcreager@nrao.edu.

This page was last modified on September 11, 1997.