ERS-1 and ERS-2 altimeter data are often regarded as inferior products, especially with respect to the ``the high-accuracy TOPEX/POSEIDON mission''; an unfortunate misconception. In fact, the mission goals on performance of the principle altimeter measurements (range, significant wave height and wind speed) and of the radiometer were equally tempting, and careful analyses show that levels of noise, precision and stability are competative.
What hampered ERS-2 is its ERS-1 heritage. This satellite, in turn, suffered the loss of the PRARE tracking device and from product and algorithm definitions anno 1990 and the reluctance to change those in a later stage or reprocess; some important recalibrations to the measurements were never applied and most geophysical corrections became rapidly out of date, surpassed by more accurate ones. Finally, both satellites require dedicated gravity field models and orbit determination procedures to minimise orbit errors.
Combination of recalibration algorithms, updated geophysical corrections and precise orbits provides a harmonised and accurate ERS-1/2 altimeter product that allows the reconstruction of many ocean parameters with equal efficiency as other altimeters, but with the denser 35-day repeat coverage.
The procedures and new analyses on precision and stability are discussed.