Abstract
Measurement of distance in space by means of optical telescopes has reached to its limit in recent years. However the radio astronomy, particularly the observations of milli-second pulsars and the VLBI technology will enable us to carry out such measurement inside or outside of our galaxy, by simply extending the technology of orbit determination for deep-space missions.
Particularly the polar coordinate representation of the trajectory of a celestial body will simplify the covariance analysis of measurement accuracy and provides us with more intuitive informations, when simplified models are used, and such analysis as well as measurements will contribute very much to the development of the future astrometry.
