KATPoint Delay CalculationTechnical Debt

KATpoint takes a very simplistic approach to delay calculation. This needs to be improved for the longer baselines of SKA (particularly MID) but ideally we should preserve the simple interface and usability qualities of KATpoint.

Traditionally, Radio Telescopes use calc/solve for delay calculation, but other alternatives exist. Calc/Solve has a number of problems, primarily because it is a set of file driven Fortran programs with a history, rather than a callable software module. The initial goal would be to evaluate alternatives and adopt an approach which would provide a simple C or C++ library similar (or associated with) the SOFA library for positional astronomy.

Attached are a couple of papers that give a bit of background. 

• 039_gordon_etal.pdf is a description of Difxcalc – which is a wrapper around Calc11 for the DiFX Correlator, which overcomes many of the problems NRAO and ALMA have had using Calc 9, but still is not a callable library.
• Klopotek16.pdf is a comparison of different VLBI delay calculation packages. I do not know whether any of them have better interfaces than Calc, and why Calc has been adopted for non-VLBI systems.

I also have some emails from various people in the field if that is useful.