The path taken by SARA-G is determined by Vc + Vr, where Vc is the current, Vr is the velocity relative to the water. Vr is the sum of windage and paddling. At CSIRO we update our estimate of Vc daily using satellites. This estimate is a week old but is still valuable as a now-cast (it is not a forecast, but we will use it here as if it was, for demonstration purposes).

The plot indicates the trajectory of SARAG, from her present position until landfall, for Vr spanning a range of speeds and directions.

A table of estimated dates of landfall is at left on the big picture plot.

These calculations are repeated every hour but the system that does this is unmonitored, and not maintained 24/7. Hardware and software failures occurring during the holiday period may not be rectified for some time. Errors and ommissions in the incoming satellite data are not all detected and can cause spurious results.

That said, we are pleased to assist this historic crossing of the Tasman Sea and wish the crew well.

David Griffin