Because of the shortness of the altimeter time series
(7 years for Jason-1 on the nominal orbit and 2 years on
the interleaved orbit, 8 years for Envisat and 2.5 years for
Jason-2), and the known aliasing effects due to the 35-day
repeat cycle of Envisat and the 10-day repeat cycles of
Jason-1 and Jason-2, it is not possible to use the harmonic
analysis method to remove the tide from the altimetry data.
The classical method is to use a tide model, generally based
on or assimilated with altimetry data. It may introduce
some circularity in the validation but it is the only current
way to correct the altimetry data from the ocean tide