At each site, a sonar beacon is deployed to the sea floor. The beacon’s signal, along with satellite positioning data (GPS), is interpolated by the ship’s Dynamic Positioning System (DP), which adjusts the thrusters to hold the ship in position over the site. When operations are completed at the site, the sonar beacon releases a ballast and rises to the surface where it is retrieved. (Credit: Yuxin He & IODP) [Photo ID: exp356_132]