United States Coast Guard C-130 Loadmasters dropping an Aerial eXpendable Conductivity-Temperature-Depth (AXCTD) probe from the open back ramp during an Arctic Domain Awareness Flight over the Beaufort Sea. Obstacles included broken ice coverage approaching 90% and a low stratus cloud layer. The crew on the flight deck has located an open water gap large enough to hit, and the dropmasters are awaiting the command to "drop-drop-drop".
Upon hitting open water, an AXCTD probe deploys a float with a radio transmitter, establishes a radio link to the circling aircraft, and transmits the data as a sensor probe falls through the water measuring temperature and salinity through a long, fine wire. The oceanographic profile measured by this drop may be viewed here .
In the foreground secured to the ramp is an Airborne Expendable Ice Buoy (AXIB) buoy readied for deployment by parachute to drift with the ice reporting atmospheric pressure, air, and sea surface temperature via the ARGOS satellite system.