The fundamental output from this sub-facility is the contribution of a continuous absolute bias data stream, or time series, to the Ocean Surface Topography Science Team (OSTST). These data are vital to enable the OSTST to deliver final ‘calibrated and validated’ Geophysical Data Records (GDRs) to the global oceanographic community through its various data centres. The contribution of the absolute bias data stream and its technical detail is undertaken at the annual OSTST meetings and through regular publication in special calibration and validation issues (for example in the journal Marine Geodesy). To review these contributions, follow the links below OSTST Contributions.

The current evolution of the absolute bias time series that spans the TOPEX/Poseidon, Jason-1 and OSTM/Jason-2 missions is shown below. An absolute altimeter bias that is not equal to zero highlights that the altimeter systems, while having very good repeatability and precision can have significant offsets , and gives estimates of sea level either too high (indicated by a positive (+)ve bias value) or too low (indicated by a negative (-)ve bias value). We place conservative error estimates of ±15 mm on these mean absolute bias values (as determined from a rigorous error budget, see Watson et al 2011 for details).

The causes for the significant biases for both the Jason-1 and OSTM/Jason-2 missions remain unclear (although progress has been made on this) and further emphasises the importance of ongoing and sustained calibration and validation activities from a global set of calibration sites.