The Lockheed P-3 Orion is a four-engine, turboprop plane based on the Lockheed L-188 Electra commercial airliner. Scientists aboard the Lockheed P-3 Orion deploy Global Positioning System (GPS) dropwindsondes as NOAA Corps officers pilot and navigate the P-3 through the hurricane. These instruments continuously transmit measurements of pressure, humidity, temperature, and wind direction and speed as they fall toward the sea, providing a detailed look at the structure of the storm and its intensity. The P-3s' tail Doppler radar and lower fuselage radar systems, meanwhile, scan the storm vertically and horizontally, giving scientists and forecasters a real-time look at the storm. The P-3s can also deploy probes called bathythermographs that measure the temperature of the sea.