Spherical {D}ish {H}uge {A}rray from {R}adio to {IR}

Abstract

Eight element 20m spherical dish array was constructed as a digital interferometer forsearching radio transient sources and pulsars. Wavelength ratio to IR is10000. We investigate the possibility in extending wavelength to IR.In spherical dish all segment mirrors have identical iso-curvaturewhich makes it possible to use mass-produce system. In our sphericaldish array 36x2x8 = 576 segment mirrors are used. Present surfaceaccuracy of 2mm rms must be reduced to 0.01 mm in IR which requiressmaller segment mirrors. Aberration correcting asymmetrical Gregoriansub-reflector is used in the present radio observation watching to fivedegrees from zenith and focus is at bottom in each dish. Thus the skyfrom +32 deg to +42 deg zone in declinations is observable. Only Azrotation of sub-reflector and feed horn are required. Four box PCsreading sixteen Az rotary encoder outputs of the sub-reflectors andthe feed horns control them to rotate. Main PC watching all systemis connected with the box PCs by RS485 cables. Total constructioncost of the present eight element array in radio waves was 1.2M.Present digital phase correction system might be useful in futuredigital adaptive optics system in IR Spherical Dish Huge Array.