射电天文中甚高频干涉仪系统电离层修正的一些注释

SOME NOTES ON THE IONOSPHERIC CORRECTION FOR VHF INTERFEROMETER SYSTEMS IN RADIO ASTRONOMY

本文结合射电天文中具体测量方法并考虑甚高频干涉仪系统参数与电离层参数间的关系,讨论了电离层各种修正方法的含意.结论为:(1)实时实地地测量电离层参数并以同一时间尺度对观测数据作电离层改正是评比各种方法的依据.(2)在信噪比足够的情况下,电离层模型法和双频法用10秒钟的平均观测数据作电离层修正是合理的,但在标准源校准法中,取Dmax=1km,要用约3分钟的平均观测数据作电离层修正才是合理的.(3)当不规则性尺度较基线为长时,标准源校准法可良好地消除它的影响;反之,闭合相位技术可有效地消除它的影响.(4)如果实现双频观测,则双频法是一个有效地消除电离层影响的方法.

Associating the measurement methods and considering the relations between the parameters of the equipment and those of the ionosphere, various methods of ionospheric corrections are discussed in this paper. The main conclusions are: (1) The criteria to compare various methods are that the ionospheric parameters must be measured in real time and position as the observation of individual radio source; the time interval during which the ionosp heric parameters are measured must be same as that during which the data to be corrected are me asured. (2) As the radio source is strong ennough, it is reasonable to use the mean feature of the ionsphere during about 10 seconds to mabe ionospheric correction for the ionospheric model method and dual frequencymenop. but for the reference radio point source method, taking Dmax=1 km, the mean feature of the ionosphere during about 3 minuts must be used. (3) When the scale of the irregulaties of the ionosphere is larger than the base line length, the ionospheric influence can be eliminated effectively by utilizing the reference radio point source method, as the reverse condition is true, closure phase technique is more desirable. (4) If dual frequency observation is applied, the dual frequency method is the most reasonable one to eliminate the influence of the ionosphere.