Verification of a dimensionally stable space structure

In a parallel paper of IAF97 congress, the development of a dimensionally v ery stable carbon/carbon telescope is presented. The present paper focuses on the verification of this structure. In order to check the stability of t he telescope, the following performances were assessed: mechanical resonance frequencies and damping, dimensional stability after a series of thermal cycles, gravity load deformation, elastic deformation under static stresses simulating launch loads, residual deformation after launch loading, thermal expansion under uniform heating, deformation under nonuniform heating, stability with time under stress. The total deformations which were expected in the worse case for this long structure (565 mm were very small: defocus < 1.5 <mu>m; decentre < a few <m u>m; tilt < 10 <mu>rad. All the independent contributors to the total defor mation were of course smaller and had to be assessed. The requests for accu racy of the measurement techniques were then very high. Several techniques were used in this verification, the most interesting of which were: evaluation of geometrical stability by comparison with a Zerodur reference structure equipped with capacitive sensors, vacuum interferometry with a very stable differential interferometer, holographic interferometry. The measurement problems are discussed and the main results are summarised. (C) 2001 International Astronautical Federation. Published by Elsevier Sci ence Ltd. All rights reserved.