... Up: Data Processing Systems . ... One of SIM's key issues is to develop a new algorithm for calculation of fringe parameters. Not only astrometric results need that new algorithm, but also real-time fringe tracking requires a new method to calculate phase and visibility fast and accurately. The formulas for the phasor algorithms for fringe estimation are presented. ... The advantages of phasor algorithms for application of fast fringe tracking and on-board data compression are discussed. ...