Simultaneous Crossover Adjustment for Contemporary Altimeter Missions

Since some time several altimeter satellites are operating simultaneously (ENVISAT, Jason-1, ERS-2, GFO, TOPEX/Poseidon). The large number of nearly simultaneous crossover events are used to estimate in a common adjustment radial error components of all altimeter missions. A discrete representation is used for the radial error components by minimizing both, crossover differences and consecutive differences. Differences with larger time delay are downweighted and the relative influence between crossover and consecutive differences is balanced. The discrete approach has a rank defect of one which is solved by constraining the sum of all error components of the “reference” mission to zero. Relative range biases are obtained for all but the reference mission. Statistics of crossover differences before and after the adjustment verify the estimated errors.