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Autonomous Underwater Profiling Drifter (AUPD) is developed by National Institute of Ocean Technology (NIOT), Chennai, India, for the vertical profiling of the ocean. AUPD is a free-drifting profiling platform for near real-time in-situ observation of the upper 2000 m of the ocean column. It measures conductivity and temperature profiles with reference to depth. The AUPD transmits measured data through ARGOS satellite Platform Terminal Transmitter (PTT) to ARGOS regional centre as per the requirement of the International ARGO program. The AUPD ascends or descends due change in buoyancy (±250 cm3). While on sea surface (to transmit the profile data), the position of the float is derived using the Doppler shift method with an accuracy of ~100 m. NIOT developed AUPD and deployed in the Arabian Sea in 2013–2015. The AUPD is ballasted for a pre-deployment depth of 2000 m and pre-programmed for a typical profiling cycle of 2 days. The AUPD is designed with 32 bit Atmel micro-controller and a lithium battery bank provides power. It has endurance for 150 profiles. AUPD float is suitable to fulfil the demand for profiling floats for International Argo Program. This paper is focused on the development of AUPD. The paper also discusses testing and field deployment of AUPD float. [ABSTRACT FROM AUTHOR]

Drifting buoys (DBs) are widely deployed to observe near-surface ocean currents and sea surface temperature. The National Institute of Ocean Technology (NIOT), Chennai, India, had indigenised the DB with the Indian satellite (INSAT) in 2012. This paper describes the results of various studies conducted by NIOT using the indigenised DBs and also describes unique features attempted in indigenised DBs to measure the near-surface ocean current with 24 position acquisitions per day to capture small-scale surface eddies and the use of real-time geostationary satellite communication every hour. Additionally, the surface currents observed with indigenous DB are compared with DBs available in the market, Marlin-Yug (coefficient of determination R2 > 0.88) and forecast using the ocean surface current analyses real-time (coefficient of determination R2 > 0.90). Our results show that the DBs in the Bay of Bengal are carried with the East India Coastal Current in the March–May periods and the in-situ observations by the DB provide accurate surface current observations than satellite-based data. Furthermore, the new observations near the world's largest tidal mangrove and delta system, the Sundarbans and Bengal Delta, will help in further enhancing our understanding of the spatiotemporal variability in the region in terms of coastal currents and its influence on marine environments. [ABSTRACT FROM AUTHOR]