Does the Site Test Interferometer Measure Fluctuations on the Right Time Scales?
The site test interferometer measures the rms path length fluctuations over a 300 m baseline, but the total power problem requires knowledge of fluctuations on baselines of 1-10 m. We produce a temporal structure function from the interferometer’s phase time series (Holdaway et al. 1995), which provides information about the path length variations on time scales down to 1 s. Our site test data shows no evidence for deviations from a constant power law down to 1 s. However, at 1 s we are often affected by the interferometer’s instrumental function, and it is not clear if we could see a change in the structure function. We will assume that the structure function which we derive on time scales between 1 s and the turnover time, typically 20-60 s, is representative of the structure function on time scales of 0.1 s to a few seconds.
