On detection of the free inner core nutation from VLBI data

Several attempts to discover the FICN signal in VLBI nutation series made during last years failed. In this paper, we present some results of our further steps in this direction, unfortunately not successful either. We investigated several VLBI CPO series by means of spectral and wavelet analysis. It has been shown that there are several periodic signals with close amplitude around the expected FICN period without any prevailing one that can be reliably associated with the FICN. The most interesting for further analysis is a relatively stable oscillation with period of about 750–800 days, which is, however, beyond the intervals predicted in other studies. It seems to be necessary to improve theoretical estimates of the FICN period to make its search in the observational data more promising.