If you've read this far, have done all the exercises, and understand every step of the tutorial, it's time to use Fourier Transforms for doing HESSI tasks. You should be able to use the FFT to find the dominant frequency and period in any subset of a HESSI modulation profile. Write a program that does that for a binned score and use it to find the time of maximum modulation frequency. Then compare its speed and reliability with the autocorrelation technique.