<title>Improved precision of absolute thermal-expansion measurements for ULE glass</title>

Improvements made in the ultrasonic thermal expansion measurement methods used at Corning Incorporated have significantly increased the precision of absolute CTE measurements on ULE^TM glass. Precise CTE data were required for modeling the performance of 8-meter mirror blanks. Several repeatability and reproducibility studies for many of the measurements performed throughout the 8- meter process were performed. Measurement equipment and procedures were then improved to obtain the required precision. A volume of absolute CTE data collected during the manufacture of three 8-meter mirror blanks is summarized, showing excellent results. Comparison with previously demonstrated precision is also given.