The 8-m radio telescope solar observations

Description of the instrument and the observational procedure.

Systematic daily radio monitoring of the Sun in the 810 MHz band in the Astronomical Observatory of the Jagellonian University began in October 1957.

In the end of 1995 the old 7-m. antenna was replaced by a new 8 meter polar mounted parabolic antenna. A spiral feeder (left polarisation) of the Watkins-Johnson brand was put in the primary focus of the antenna along with a box containing pre-amplifiers and calibration circuits.

The receiver is a Hewlett-Packard spectrum analyser working in a linear regime in ten chosen channels, each with a bandwidth of 5 MHz and the following central frequencies: 275, 405, 670, 810, 925, 1080, 1215, 1350, 1620, 1755 MHz. These frequencies were chosen to keep approximately equal 135 MHz intervals between neighbouring frequencies, with two gaps (405-670, 1350-1620) where frequencies were useless due to various, mainly man-made disturbancies. The solar flux is recorded every 11 seconds. Observations are taken every day from 6.30 to 14.00 UT in the winter and from 5.00 to 15.00 UT during the summer.

Calibration measurements are performed three times a day: before, during (at 10:30 UT) and after the solar observation independently in all 10 channels. Measuring signal from two internal noise sources and the sky background far from the Sun enables convertion of the system output into a value proportional to the total solar flux density. In order to establish the set of required proportional coefficients, we compare for selected quiet days our radio spectra with the ones derived from the solar flux density values published in Geophysical Data. Occasionally simultaneous observations of the total solar flux are carried out at 810 MHz with our 15 meter radio telescope. In this way we can control a level of solar flux at this frequency through following 15m telescope observations of strong calibration sources Cas A and Cyg A.

Remarks on the presented plot

At the on-line produced plots we present rough, uncorrected data registered by the instrument, including systematic effects and earthly disturbances. Systematic effects seen on the presented curves in the sun rise and the sun set phases are mainly of environmental origin.