4 Conclusions

The new method of combined smoothing further widens the possibilities of the original smoothing proposed by one of us three decades ago; it namely enables to combine Earth orientation parameters obtained by different space techniques, as demonstrated in the present paper. The tests made here show that it is advisable to use always such coefficients of smoothing $\varepsilon$, $\bar{\varepsilon}$ that yield approximately the same transfer functions (no matter whether leading to weak or strong smoothing). Otherwise (i.e., if much weaker smoothing is applied for first derivatives) one can easily obtain spurious peaks in the resulting series.

The practical examples of combining data from different techniques presented above show that the formal standard deviations of the results provided by analysis centers often do not reflect the real accuracy that is typically much lower, due to systematic effects.

The use of the proposed method is not strictly limited only to the problems demonstrated here - it can be as well used whenever we have independent measurements of a function of time (analytically not expressible) and its first derivatives. E.g., the method can be used to combine the comparisons of different atomic clocks with the comparisons of their frequencies. The code of the subroutine in Fortran and C++ is available on request from the authors.

Acknowledgements

This work has been supported by grant No. 205/98/1104 awarded by the Grant Agency of the Czech Republic. Its major part was developed during the first author's stay at Observatoire de Paris (IERS/CB and CNRS/URA8630) in May/June 1999.