Abstract: A positioner supports an antenna at an optional rotating angle and the mirror surface of the antenna at different rotating angles is measured. A computer expands the measured value into series using polar coordinates system associated with the measuring system, whereby the intrinsic deformation of the mirror surface under the zero-gravity condition and the deformation due to gravity are separately measured.

Abstract: An extendible structure includes at least three extendible longerons and a plurality of integrated radial spacers. Each spacer includes a plurality of legs integrally formed therewith to radially extend from the central part thereof. The distal end of each of the spacers is connected to a corresponding one of the extendible longerons. In the extended state of the extendible structure, at least three longerons are deployed in parallel with one another with space intervals among them in the lateral direction which intersect with the direction of extension of the longerons, and the spacers support the longerons with the horizontally spaced interval within a plane substantially perpendicular to the direction of extension of the longerons. In the collapsed condition of the extendible structure, each of the longerons is collapsed in a loop form, and the spacers are laid one upon another inside the loop formed by the longerons while the legs of the spacers are twisted.

Abstract: An extendible structure of the invention is constructed by connecting the radially projecting legs of the spacer with differing longerons through the joints, and then fastening one joint with adjacent another joint at a diagonally opposed position with a bridle. In the extended state of the structure, the spacers are within a plane which is substantially perpendicular to the direction of extension of the structure and the bridles are extended in the diagonal lines between the adjacent joints to thereby form the longerons in a mast-shaped three-dimensional structure, while, in the collapsed state of the structure, the longerons are collapsed in a loop form and the spacers are laid one upon another inside the loop formed by the longerons to thereby produce a cylindrical form in its outer appearance.