The Thetis profiler

In this project, we plan to derive optical profiles at a fixed site off Rottnest island, WA (the red star on the map of the Perth area below), by deploying an autonomous in-water oceanographic profiling system, the WET Labs “Thetis”. The suite of instruments onboard the profiler has been designed so as to provide validation data for ocean colour satellite-born instruments (in particular the ESA Sentinel3-OLCI), as well as data useful for determining the productivity and quality of waters at the deployment site.

The Thetis was purchased and initially deployed (2017/18) thanks to an ARC LIEF grant (LE160100146).

Since Q4 of 2019, this activity is funded by the Australia Integrated Marine Observing System (IMOS), as part of the satellite ocean colour sub-facility.

The Thetis is a positively buoyant profiling instrument frame that has an on-board winch and 3G telemetry system. The Thetis is deployed between Rottnest Island and the Rottenest Island canyon in approximately 60m of water, and is programmed to surface 3 times per day (dawn, noon and dusk), collecting data during the ascent.

Some more details on the Thetis here if you want.

• Seabird CTD SBE49
• 2 x WET Labs ECO Triplet “bb2fl” bb (120º) @ 470, 532 (x2), 700nm Fluorometers – ex/em 370/460nm (CDOM) and 470/695nm (Chlorophyll)
• Chelsea Fast Repetition Rate Fluorometer (RGB ex, ~682nm em)
• WET Labs AC-s reflective tube spectrophotometer a and c at 400-730nm (~4nm intervals)
• 2 x Satlantic HyperOCR (radiance and irradiance)
• Satlantic SeaFET (pH)
• Seabird Dissolved Oxygen SBE43

Upon surfacing, a subset of the data is transmitted back to Curtin University via the 3G network and data is automatically processed for routine quality control. The full data record and sensor re-calibration is performed monthly.

Data and analyses