Abstract: There is herein described a support structure for antennas, optical systems and the like which are generally subject to non uniform dimensional changes due to temperature variations and gradients in the support structure material, the invention overcoming such dimensional changes by combining the use of a material having a low coefficient of thermal expansion and the use of a heat pipe as an integral part of the aforementioned structural member for isothermalization, to reduce the distortion resulting from residual non-zero coefficient of thermal expansion.