Measurement of the temporal phase stability of the medium

The temporal phase stability of the medium was measured at a site used for the collection of synthetic‐aperature sonar data. These measurements were conducted over a two‐year time span, and were made at several different heights‐above‐bottom. Results obtained show that for small heights‐above‐bottom, the standard deviation of the phase is as small as 0.04 radians over a 20‐min measurement interval. At larger heights‐above‐bottom, the standard deviation of the phase is much larger, getting as large as 0.31 radians over a 2‐min interval for one measurement.