【摘要】 北京天文台的3.2厘米波段射电望远镜(PEKG 9395)自1965年开始进行太阳流量的绝对定标及每日的相对定标.设计了一个36.1厘米×29.1厘米×240厘米的角锥喇叭作标准天线校正日常使用的抛物面天线的增益,并研制了一个沸水式热噪声源作噪声功率标准.总精度约3.6—8.0％.与日本的TYKW 9400(Toyokawa Obs.,Nagoya Univ.,Toyokawa,Ja-part)流量比值的年平均值与1的偏离不大于2％.经过把用作二级标准的太阳附近背景温度修改及大气吸收改正后,周年变化几乎完全消除.一个半以上太阳活动周内观测证明,我们的绝对定标有良好的绝对精度及良好的长期和短期的稳定性.这个方法也可用于整个厘米波段及长毫米波段的绝对定标.更多还原

【Abstract】 The radio telescope (PEKG 9395) of Beijing Observatory at 3.2 cm began to practice the absolute calibration and daily relative measurement of solar flux density in 1965. A pyramidal horn used as a standard antenna for measuring gain of the paraboloid antenna used in daily calibration was designed. The size of the horn is 36.1 cm ×29.1 cm ×240 cm. As a standard noise power a hot noise source boiling water was developed. The effect temperature that the hot noise source supply is about 373 K. The rms. error is ±0.24 K.The gain of the paraboloid antenna with diameter of 2m used in daily calibration was obtained by the method to measure the solar emission using the horn antenna and paraboloid antenna in turn. The experiment arrangment is shown in Fig, 2. The experiment was carried out repeatedly in 1965, 1968, 1969, and 1978. The results were consistent and are shown in table 1. T.(h), the distribution of the background noise temperature of the paraboloid antenna directing at zenith and meridian plane, were calibrated by the hot noise source and has been taken as "second noise standard" of daily calibration. The results are shown in table 2, and Fig. 3. The total error is about 3.6% (rms)-8% (max).The mean ratio of the solar flux density in a year between PEKG 9395 and TYKW 9400 (Toyokawa Observatory,Nagaya Univ., Toyokawa, Japan) is different from one unity by a factor of 0.02 (shown in table 3 and Fig. 4). After analysing the data it was found that the annual veriation of the ratio of solar flux density between PEKG 9395 and TYKW 9400 are caused by the annual variation of Ts(h), the distribution of the background noise temperature of the paraboloid antenna, and the correct factor of atmospheric attenuation. The annual variation of the ratio was almost removed by means of modifying the background radiation by measuring daily with a gas discharge noise tube and correcting the atmospheric attenuation (shown in Fig. 5 and Pig. 6).The accidental error of daily calibration make a few progress in late years, but it was found that the accidental error raised as the solar activity increase, because more intense active regions that cause the observed value decreasing and more bursts of GRF, PBI type that cause the observed value increasing appeared in max. Years.Through observation for one and half solar cycle, it is proved that our absolute calibration and daily relative calibration have a fine absolute accuracy and a good stability of short and long term. This method may be used in all centimeter band and long millimeter band.更多还原