APEX is a autonomous drifting profiler used to measure subsurface currents and make profile measurements. It surfaces at programmed intervals for data telemetry and geo-location via ARGOS or IRIDIUM satellite. Standard sensors include TP and Salinity; other sensor options are available .
APEX has a 4-year life and can surface approximately 150 times from a maximum depth of 2000 meters. Over 6000 APEX floats have been delivered to users in 19 nations. Floats are provided deployment-ready, and are routinely deployed from merchant ships (VOS) while moving at 20+ knots. The APEX salinity profiler has been certified by US Dept. of Defense for air deployment from C130 aircraft.
APEX floats drift at a fixed pressure (usually around 1000 meters depth) for 10 days. Then, within the relatively short time of around six hours, the floats move to a profiling pressure (usually 2000 meters deep) before rising and collecting profiles of pressure, temperature, and salinity on their way to the surface, where they transmit the data collected via a satellite link back to a ground station. The floats then sink again and repeat their missions. APEX float lifetime is about four years.