AUTONOMOUS PROFILING FLOATS – GOING WITH THE FLOW –HARDER THAN IT LOOKS - GREAT SCIENCE AND NEW APPLICATIONS

摘要

Buoyancy driven profiling drifters have been around since the late 1970’s and over 3,500 of themprovide researchers data from around the world’s oceans thanks to a global cooperative programcalled Argos. Lagrangian by design, these profiling drifters relay data such as; temperature,salinity, dissolved oxygen and other water qualities via satellite communications, as they driftwith the currents. It is the appearance of simplicity that leads some to under-estimate thechallenges faced by profiling drifters. These systems do not propel themselves, they do not needautopilots. They just sink until they become neutrally buoyant, float around at that depth forseveral days, and then float back to the surface to relay data. How hard can that be? Turns out itis harder than some would believe. The mechanical and electrical systems must be able to pumpcontrolled amounts of oil into and out of a rubber bladder at pressures that range from oneatmosphere to 10,000 psi and temperatures near freezing. And they need to do this using minimalenergy over 150 times or more. The compressibility of the hull, sensors, and antennas must beaccurately calculated to ensure near neutral buoyancy at the desired depth with minimal energyuse in adjustments. Lastly, the control systems must be robust enough to operate for yearswithout rebooting. Originally, profiling floats simply provided depth averaged drift data. ThenConductivity, Temperature and Depth (CTD) sensors were added so researchers could betterunderstand the oceans’ energy budget and study other related phenomena. As humans seekresources from greater depths and new regions profiling floats are being used in new ways.During the Deep Horizon spill, APEX floats were deployed with new sensors to better understandthe deep currents and assess the ability to identify hydrocarbons in the water column. Theseemerging applications for buoyancy engine driven systems require new sensors and energysources. Buoyancy engine driven profiling floats have been and will continue to be one of themost cost effective ocean sensing platforms available to researchers. They also will fill greaterroles in emerging missions. They may just “go with the flow” but these systems are vital to ourmaritime future.