Because of its greater altitude, the orbit of TOPEX/Poseidon (T/P) can be estimated to a superior accuracy to that of ERS-1. This fact can be used to reduce the radial orbit error contamination of ERS-1 altimetry through minimisation of dual crossover residuals between altimetry from the two satellites. By use of a sinusoidal orbit error approximation over arc lengths of half a circumnavigation, the dual crossover dataset has been used to refine ERS-1 radial positioning. This study has investigated the absorption into ERS-1 altimetry of geographically and temporally correlated T/P errors, particularly radial orbit errors. By modelling the periodic and geographically correlated T/P errors, some absorption of terms, including amplification of several periodic components has been demonstrated. This aliasing is influenced by the spatial and temporal sampling patterns associated with each arc, leading to highly geographically correlated absorption of T/P radial orbit errors, typically of the order of 50% of the total cumulative T/P radial orbit error.