Susumu Kawashima

The Nobeyama radioheliograph

A new 17-GHz radio interferometer dedicated for solar observations was constructed in two years at Nobeyama, Nagano. It consists of eighty-four 80-cm-diameter antennas arranged in a tee-shaped array extending 490 m in east-west and 220 m in north-south directions. Since late June of 1992, radio full-disk images of the Sun have been observed for 8 h every day. The spatial resolution is 10 and the temporal resolution is 1 s and also 50 ms for selected events. Every 10 s correlator data are synthesized into images in real time and displayed on a monitor screen. The array configuration is optimized to observe the whole Sun with high spatial and temporal resolution and a high dynamic range of images. Image quality of better than 20 dB is realized by incorporation of technical advances in hardware and software, such as (1) low-loss phase-stable optical-fiber cables for local reference signal and IF signals, (2) newly developed phase-stable local oscillators, (3) custom CMOS gate-array LSTs of 1-b quadraphase correlators for 4/spl times/4 combinations, and (4) new image processing techniques to suppress large sidelobe effects due to the solar disk and extended sources. >

Solar Activity Observed with the New Nobeyama Radioheliograph

The new Nobeyama Radioheliograph was completed in March 1992 after two years of construction. It is a T-shaped array operating as a multiple spacing grating-type radio interferometer at 17 GHz and is dedicated to full disk solar observations. Routine observations began in late June, 1992, after three months of system integration, fine tuning, and test observations. During the course of test observations it was shown that major items of the system performance exceeded the designed values, and that the image quality or the dynamic range of the images is better than the designed value. In the three months of routine observations two X-class flares, several M-class flares and a number of small flares were observed. In this report we present a summary of initial observational results and preliminary comparisons with YOHKOH HXT and SXT observations.