Tuesday, 17 July 2012

Day 12 - Autosub Joy

Well, we’ve had an exciting few days out here and have just had our first data download from Autosub. After some rough weather and some troubleshooting, we are now collecting some of the great high-resolution data we’ve been waiting years to see.

Steve McPhail prepares to launch Autosub6000
Autosub was launched yesterday afternoon to do its first mapping mission at the seafloor. We took some test shots with the downward-facing camera to make sure the focus and lighting was set up correctly to create the habitat maps that we want. After a long dive to the seafloor, it finally reached 4800 m, oriented itself correctly in relation to the ship’s GPS and conducted a 10-minute photographic test flight approximately 3m above the seabed, which is extremely close for this kind of vehicle! Thankfully everything went exactly according to plan, and the cameras functioned very well, taking images approximately every 0.8 seconds and recording a total of 1600 for us in just 10 minutes!

A Pycnogonid, a sea spider
When we start doing the longer missions we’re going to have a lot of image processing to do. Still, even in such a short dive we still got some very good images of the benthic megafauna.

After the test run was complete, Autosub continued with its primary mapping mission, using multibeam sonar to produce an extremely detailed map of the seabed. We’ve only completed a small part of the total area we’re hoping to cover, but you can already see in the image below how the resolution of the new map compares to the map we made previously using ship-based multibeam acoustics.

Hi-res bathy data taken by Autosub
on the left vs ship-acquired data
The term bathymetry is the oceanographic equivalent to topography – the shape, highs and lows of the ocean floor. Think of the word ‘bath’. Compare the Autosub bathymetric data on the left with good quality ship-based bathymetric data on the right. The resolution in the squares on the right is about 50m, whereas the Autsub data contains more than 50 times more detail. In this image the warmer colours indicate a higher bathymetric area, whereas the deeper areas are blue in colour, ranging from about 4600 to 4850m depth.

As you can imagine we spent much of the day going through the catalogue of data that was collected in just five hours of seafloor mapping. There was lots of gathering around computer screens.
Autosub’s next mission is planned for tomorrow, the aim of which will be to continue bathymetric mapping a bit more of the study area before we start with the large-scale photographic surveys of the benthic megafauna and fish.

A Grenadier fish