The AUV Sirius is our workhorse platform. It conducts most of the surveys associated with our IMOS AUV Facility program. This vehicle is a modified version of a mid-size robotic vehicle called Seabed built at the Woods Hole Oceanographic Institution. Sirius is 2.0m long by 1.5m high by 1.5m wide and weighs approximately 200kg. It has a maximum speed of 1m/s and can descend to depths of 700m. It is specifically designed for undertaking high resolution benthic optical and acoustic imaging work and is equipped with a full suite of oceanographic instruments. These include a high resolution stereo camera pair and strobes, a 330 kHz multibeam sonar, depth and conductivity/temperature sensors, a 1200 kHz Doppler Velocity Log (DVL) including a compass with integrated roll and pitch sensors and a flurometer to measure coloured dissolved organic matter (CDOM) and chlorophyll-a and backscatter. Data is time-stamped and logged on the vehicle’s on-board computer. A variety of navigational sensors including GPS, Ultra Short Baseline Acoustic Positioning System (USBL) and forward looking obstacle avoidance sonar, enable precise tracking of the vehicle. This permits survey data collected by Sirius to be geo-referenced at high precision.