Determining the Astronomical Refraction and Building the Radio Wave Refractive Delay Model Measured(Ⅲ)——A Special Measuring Instrument

aimed at the demands of high accuracy on determining the astronomical refraction and building radio wave refractive delay corrective models varied with change in station and direction, a new instrumental error theory is presented in the paper. Its key ideas are to allow instrumental errors existing, and to consider them to be fluctuated continuously, but to measure in real time and correct them by means of corresponding measurements, at the same time, to eliminate influences of various distortions and errors, to remove all kinds of systematic error sources from observational data so as to improve accuracy of single measurement. To meet the requirements of observations from the zenith to low altitudes in several directions at observing stations in different latitudes, a general program for the instrument construction and a design plan are presented, in which a video CCD camera is used as the terminal of the receiver. Furthermore, determining methods for various instrumental errors and design demands on the measuring devices are described in the paper.