The Beam Pattern of Reflector Antennas With Buckled Panels

On high precision reflector telescopes the transient thermal panel buckling can have an effective rms-value comparable to the errors in the adjustment of the reflector panels. Under this condition, high signal-to-noise radio holography of high spatial resolution can reveal the characteristic signature of panel buckling in the beam pattern and can map the surface deformation of the buckling, while lower signal-to-noise Moon limb scans may see the buckling only under favorable conditions. Detailed diffraction calculations, and some observations, indicate (1) that the panel buckling produces diffraction rings and/or diffraction spokes, (2) that panel buckling in azimuthal direction may have a smaller degrading effect than panel buckling in radial direction because for azimuthal buckling the energy is spread more uniformly over a large solid angle, and (3) that the coverage of the reflector aperture with buckled panels determines the multiplicity of the diffraction rings and/or diffraction spokes.