Statistics of AUV’s Missions for Operational Ocean Observation at the South Brazilian Bight.

The high costs and logistics limitations of ship-based data collection represent an obstacle for a persistent in-situ data collection. Satellite-operated Autonomous Underwater Vehicles (AUV’s) or gliders (as these AUV’s are generally known by the scientific community) are presented as an inexpensive and reliable alternative to perform long-term and real-time ocean monitoring of important parameters such as temperature, salinity, water-quality and acoustics. This work is focused on the performance statistics and the reliability for continuous operation of a fleet of seven gliders navigating in Santos Basin – Brazil, since March 2013.

The gliders performance were evaluated by the number of standby days versus the number of operating days, the number of interrupted missions due to (1) equipment failure, (2) weather, (3) accident versus the number of successful missions and the amount and quality of data collected.

From the start of the operations in March 2013 to the preparation of this work (July 2015), a total of 16 glider missions were accomplished, operating during 728 of the 729 days passed since then. From this total, 11 missions were successful, 3 missions were interrupted due to equipment failure and 2 gliders were lost. Most of the identified issues were observed in the communication with the glider (when recovery was necessary) or the optode sensors (when remote settings solved the problem). The average duration of a successful mission was 103 days while interrupted ones ended on average in 7 days. The longest mission lasted for 139 days, performing 859 continuous profiles and covering a distance of 2734 Km. The 2 projects performed together 6856 dives, providing an average of 9,5 profiles per day or one profile every 2,5 hours each day during 2 consecutive years.