The effect of earth orientation errors in baseline determination

Abstract

The determination of baseline lengths from certain space techniques is based on the derived coordinates of the terminal stations. As such, the estimated baselines are susceptible to systematic errors that affect the relative coordinates. One source of error is in the set of parameters which describes the continuously changing relative orientation of the Conventional Terrestrial (CTS) and Inertial (CIS) Reference frames. Due to these errors, the coordinates of each terminal station may in fact refer to a slightly different coordinate svstem, and, therefore, when used for computing the length between the stations, errors will result. The expected magnitudes of such errors and their possible presence in current solutions are investigated.

In conclusion, we find that the present level of accuracy and stability of the available parameters connecting the CTS and CIS (e.g., the ERP series) is unsatisfactory for centimeter level baseline length determinations. The available options are either the use of strictly simultaneous SLR data sets (similar to the VLBI data sets) or the improvement of the parameters connecting the CTS and the CIS. The first long-range step in the latter direction is the support of the IAG/IAU Joint Working Group COTES proposal [CSTG Bulletin, 1982], endorsed by both the IAG and IAU in various resolutions [IAU, 1983; IAG, 1982].