Compensation of gravity-induced structural deformations on a beam-waveguide antenna using a deformable mirror

At the NASA Deep Space Network (DSN) Goldstone Complex, located in the Mojave Desert in California, a 34-meter-diameter beam-waveguide (BWG) antenna, DSS-13, was constructed, and has become an integral part of an advanced systems program and a test bed for technologies being developed to introduce Ka-band (32 GHz) frequencies into the DSN. The antenna efficiency at 32 GHz was found to depend significantly on the elevation angle, i.e., it decreased from 45% to 35% as the elevation angle changed from 45 degrees to 20 degrees. This elevation angle dependence is due to the deformation of the main reflector caused by the resulting change in gravitational force applied to the antenna structure. A method for compensating the gravity-induced structural deformations in a large ground-based beam-waveguide antenna is presented. A deformable flat plate (DFP) is installed at the M6 mirror location in the beam-waveguide optics.