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The fundamental unit of time for fringe-stopping is the sample, which at a sample rate of 1.28MHz, corresponds to about 0.7 microseconds. Delays are typically in the range of +/- 20 whole samples. The fractional component is represented in the metadata table with 32-bit floats, which we found to be sufficient - targeting a precision on the order of microsample resolution. 16-bit signed integers targeting millisample resolution were found to be insufficiently precise for fringe stopping. Corrections are performed by applying a phasor parameterised by a slope and offset derived with integer millisample precision from the 32-bit floating point input. The precision and range used in these calculations has been selected to accommodate corrections in a wide range of circumstances, with most observations making use of only a small fraction of the available resolution.
Diagram: Comparison of geometric corrections process for using Birli and fringe-stopping
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