On a happy note, I woke up early this morning with my head spinning with ideas about the two CTDs that would not communicate, and the idea came to me that perhaps their "instrument transmit" and "instrument receive" wires (Tx and Rx) had been reversed in our specially-made pigtail adapters. If that was the case then I'd surely had to use "null modems" to connect to them in my office in January but perhaps I'd done just that and hadn't remembered it, due to the long delay between testing and deployment. So when we arrived at the lab, the first thing I tried was to connect to the CTDs via null modems and hurrah!, that was successful. Fortunately I had two null modems with me that I could wire into the brain connections at the top of the station later that day.
With that short delay we were still ready to leave the dock by 9am. Upon arriving at the station I connected the five underwater instruments, on the boat, to the five new cables with cable-tie markings as follows:
- "Groundtruth" CT, north side
- Deep Light Sensor, south side
- Deep CTD, south side
- Shallow Light Sensor, north side
- Shallow CTD, north side
During this dive we also removed the last two of the old cables, for these had been tangled or cable-tied and we'd been unable to recover them on Tuesday on snorkel alone. We also did a brief swim around the periphery of the station, going clockwise from pin to pin around the station. In all this dive took 49 minutes.
Next I returned to the boat to connect from my laptop (via radio) to the brain to ensure that all instruments were working properly. However, I could get no connection at all and I had not remembered noticing any lights on the brain when I turned it on, so I decided to climb again and check if any obvious connections were unplugged. I did so, powering off the brain, checking connections, and then carefully watching the lights when powering it back on. I could see the serial ports briefly light up red on startup, and the radio unit flashing red to indicate that it was waiting for a connection, so I returned to the boat and tried again. When there was still no connection, I switched radios on the boat and tried a different unit, and this time I was able to connect. At this point all instruments were reporting correctly except, alas, the two SeaBird CTDs. However I knew that the datalogger programming was written to set up the CTDs to report every six minutes, and at several points it had to wait until the exact six-minute mark before proceeding, so it might take six, twelve or even eighteen minutes before the CTDs would start reporting. I returned to the pylon to plug up its external openings and tie down all loose cables, in preparation for closing it up, while we waited to see if the CTDs would wake up on their own. When I next checked the CTDs they were fine, so I finished closing up the station top and removed the safety line and rungs.
At 4:30pm Pamela and I began our final dive to retrieve the groundtruth CT and lock down the other four instruments, and their cables, more securely. The deep light sensor (whose platform is of a different design than that used for the shallow light sensor) was sitting loosely in its mount so we attempted to gum up the loose space with aquaseal. A note for future deployments: normally I don't use mastic tape at the point where the light sensors are encircled by their mounts but for this station's deep light sensor we should make an exception.
We took some post-swapout photos of the station (like this one, below) and then returned to the dock by 5:30pm, where we spent the next two hours cleaning our gear and packing our instruments and supplies for their return shipment to Miami.
