Sea trials of HWCP - 2

We have developed a unique multidisciplinary 11-km depth rated Hadal Water Column Profiler (HWCP) which allows observations in one of the most poorly studied regions on the planet -- waters in the deep ocean trenches. This free-falling profiler makes repeated vertical profiles of temperature, conductivity, and dissolved oxygen (each with redundant sensors), turbulent microstructure (mixing), horizontal velocity, and 200 kHz bioacoustic backscatter. It also records video, and has a small 11 bottle water sampler. Its design allows for multiple profiles per day, even in the deepest ocean trenches. The HWCP was developed using funds from the W. M. Keck Foundation. As part of the Keck proposal the Dean of the University of Hawaii's School of Ocean Earth Science and Technology (SOEST) provided 2 days of R/V Kilo Moana time for testing. This testing took place in December 2021, when we successfully conducted eight cast. Four were tethered in order to verify the ballast release logic. The final four were untethered and included one at night and to approximately 2000m depth. These tests showed that the HWCP is a functioning profiler with working system integration, release logic, and functional sensors. However, more at-sea testing is needed to allow the HWCP to reach its potential as a cutting-edge scientific instrument ready for research expeditions. In particular, the descent / ascent rates, and rotation period need tuning, and on the 2021 cruise we only tested a half-scale prototype of the water sampler.