EVALUATION OF THE IMAGING PERFORMANCE OF THE NOBEYAMA RADIOHELIOGRAPH

The Nobeyama Radioheliograph is a radio interferometer dedicated to so lar observations at 17 GHz. Its imaging performance is concisely descr ibed on the basis of the correlator outputs. Antenna-based errors are removed by a self-calibration method. Possible causes of correlator-ba sed errors have been considered, respectively. Among them, the importa nt factors are: 1) unequal bandpass characteristics, 2) antenna pointi ng errors, 3) delay errors, and 4) noise at correlator outputs. The ex pected dynamic range of synthesized snap-shot images is 30 dB based on these correlator-based errors. However, the actual images have a 25 d B dynamic range, which may be mostly due to the image-restoration proc edure currently adopted.