Welcome Aboard the R/V Blue Heron
Field testing and rapid prototyping of open-source hardware on Lake Superior.
This summer, as part of the UNOLS Chief Scientist Training Cruise program, I was invited to join 4 other early career researchers on Lake Superior, aboard the University of Minnesota Duluth's flagship research vessel, the Blue Heron. During this 3 day cruise, I had the opportunity to test the OpenCTD, push the OpenROV to its breaking point, and send the Niskin3D into the field for the first time. In addition, I brought my trusty Printrbot with me to explore the feasibility of rapid prototyping research materials while at sea.
I deployed my equipment at four sites: Sterner B, West Mooring, Castle Danger, and, via small inflatable, the Apostles archipelago. The Niskin3D performed flawlessly, though the OpenROV it was mounted to suffered catastrophic flooding at 100 meters. The OpenCTD was deployed from 30 to 140 meters without issue. It logged perfectly on all casts and the 140m deployment at West Mooring is the cleanest data set, by far. I actually didn't expect the data to look as clean as it does.
The only downside is that, because Lake Superior is the second freshest large lake in the world, the salinity was too low to measure, so we still need to put the conductivity circuit through its salty paces.
I blogged the whole adventure on OpenExplorer. Go check it out!
Blue Heron carries a SeaBird Model 911 plus CTD.
- The OpenCTD logs too much. By which I mean you set it up in the dry lab, attach it the the winch, and then wait for the deployment. All the while, it's logging ambient, resulting in thousands of trash data points to clean up. A simple magnetic switch would solve that problem nicely.
- with mineral oil, the tube is functionally incompressable and we had no leaks, despite several casts to various depths.
- Casts need to be slow. On the order of 0.15 m/s slow. The temperature probes are not fast.
- You need to let the OpenCTD sit on the surface for a while, like 10 minutes if it's been in the hot sun, in order to give the probes time to equilibrate.
- The data was significantly cleaner than I expected for a first sea trial.