The Thetis profiler | Curtin’s Remote Sensing & Satellite Research Group

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 profling 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.


The RSSRG version of the Thetis (image on the left) is equipped with a unique physical and optical sensor payload, including:

IMG 1937IMG 2766-fullres

•       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

Pictures above: the RSSRG Thetis profiler in his facility at the technology park in Kensington (left). Preparing for deployment on the deck of the CSIRO R/V Linnaeus (right)

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.


Ready to go, on the back of the ute.. .. On our way to deployment ... and deployed


Data and analyses:

See some preliminary results on our poster at the Ocean Optics XXIV conference, October 2018, Dubrovnik, Croatia.
Also in Jorrit Scholze's internship report here
Here is a report to IMOS about using the Thetis data for satellite ocean colour validation
And here another report to IMOS about using the Thetis data for characterisation of the optical variability off Rottnest island



Our partners in this project (partners of the ARC LIEF supported activvity):

A/Prof. Martina Doblin, A/Prof. David Suggett, Univeristy of Technology Sydney
Dr. Nick Hardman-Mountford, Commonwealth Scientific and Industrial Research Organisation, Perth
Prof. Jean-Philippe Croué and Prof. Kliti Grice, Curtin Water Quality Research Centre
Luke Zappia, WA Water Corporation
D. Nick Caputi, WA Department of Fisheries
Remote Sensing and Satellite Research Group, Curtin University, Bentley, WA 6102
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