Abstract
The Nobeyama Radioheliograph
began routine observations in late June,
1992, and radio full-disk
images of the Sun have been observed for 8h every day. This instrument
is a 17-GHz radio
interferometer dedicated for solar observations, which consists of
eighty-four 80-cm-diameter
antennas arranged in a Tee-shaped array extending 490m in east-west and
220m in north-south
directions. The spatial resolution is 10" and the temporal resolution is
1s and 50ms for selected
events. 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 20dB 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 LSIs of
one-bit quadra-phase
correlators for 4 x 4 combinations, (4) an ex! panded real-time
self-calibration method of gain and
phase errors using redundant antenna combinations, and (5) new image
processing techniques to
suppress large sidelobe effects due to the solar disk and extended
sources. A newly developed
control system with fully distributed computers enable us to continue
observations even in a
condition where some portions of the radioheliograph are malfunctioning.
In this paper, a detailed
description is given of the radioheliograph's hardware, with particular
emphasis on the stability
and accuracy of the total system.