Korean VLBI Network (KVN)

Optics and Driving Performance

The KVN antennas are designed to be a shaped-Cassegrain-type antenna with an altitude-azimuth mount. The telescope has a 21 m diameter main reflector with a focal length of 6.78 m. The main reflector consists of 200 aluminum panels with a manufacturing surface accuracy of about 65 micro-meter. The slewing speed of the main reflector is 3 deg/sec, which enables fast position-switching observations. The subreflector position, tilt, and tip are remotely controlled and modeled to compensate for the gravitational deformation of the main reflector and for the sagging-down of the subreflector itself. The characteristics of the antenna optics are summarized in table below.

Main Reflector (Axisymmetric Paraboloid
Diameter D=21.03m
Focal length f=6.78m
Focal ratio f/D=0.32
Panels manufacturing accuracy 65 micrometer
Alignment surface accuracy 50-54 micrometer
Subreflector (Hyperboloid)
Diameter d=2.25m
Manufacturing surface accuracy 50 micrometer
Expected total surface accuracy (EL ~ 48 deg) 124 micrometer
Slewing speed 3 deg/sec
Slewing acceleration 3 deg/sec^2
Operating range AZ:+-270 deg, EL:0-90 deg

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Korean VLBI Network