Simulating atmosphere phase screens for dilute arrays

We have developed a new algorithm for simulating atmospheric phase screens that is extremely efficient and flexible. It retains the N log N efficiency of algorithms based on the FFT and is able to take advantage of the small amount of atmosphere actually sampled by highly dilute arrays such as NPOI. Additionally, there is flexibility in the technique to relax (or adopt) the traditional "frozen screen" approximation. We describe the basis for the algorithms and how the code has been structured. Timing estimates are developed and we show preliminary results from the code which exhibit the correct behavior of phase difference power spectra with baseline.