Monday evening and Tuesday morning, all electronics components were assembled on the workbench as a final test of equipment, wiring and programming (see photo, left, of the "brain," or control unit, featuring the datalogger and GOES transmitter). Work at the pylon began Tuesday afternoon, with the installation of the temporary climbing rungs and safety lines. Next, the underwater cables were run from the waterline, through the internal conduits and up into the top chamber -- the cable for the underwater light sensor was run through the southernmost conduit and the other two cables (for the CTD, or conductivity-temperature-depth sensor, and the CT, or conductivity-temperature sensor) were run through the second, northernmost conduit.
The movement of heavy equipment was temporarily halted so that divers could install the underwater instruments and mounting brackets (see photo at right). During this period, the wiring of these cables to their connectors was completed at the top of the pylon, and the cable attachment point for the GOES transmitter's satellite antenna was checked for possible saltwater damage from its brief immersion during pylon installation. When the underwater work was complete, the station's two rechargeable batteries were hoisted aloft and installed in the upper chamber, bringing an end to the day's work.Wednesday morning, work at the pylon resumed. Two of the three aerial instrument masts were installed, one holding the station's Vaisala WXT520 (Weather Transmitter, providing data for winds, air temperature, barometric pressure, relative humidity and precipitation), complete with bird deterrent spikes, and the other other holding the RM Young Wind Monitor (a marine-grade anemometer) and Electronic Compass. A smaller mount holding the GOES transmitter's GPS antenna was attached off the side of one of the main masts which hold the satellite transmitter antenna and the navigation light. The third mast was temporarily mounted to measure its orientation (approximately 20 degrees north of due east) in preparation for installation of the surface light sensor.
Back on the boat, the surface light sensor was attached to its mount and the mast grounding wires were prepared for installation. The afternoon pylon work consisted of installing the standalone air temperature sensor, which is positioned behind one of the north-facing solar panels, and the surface light sensor on its aluminum mast. After all cables were run into the pylon's upper chamber and their connectors securely attached, it was time to install the "brain," or control unit. This package of electronics was carefully hoisted aloft and inserted into the upper chamber, taking care to lower it past the protruding wires and connectors still to be attached.
Once the "brain" was set in place, all of its connections were made: grounding wire, batteries (two), solar panels (five), transmitter satellite antenna, transmitter GPS antenna, air temperature sensor, wind monitor, electronic compass, Vaisala weather transmitter, surface light sensor, underwater light sensor, CTD and CT. At this point the station's power switch was placed in the ON position (see related blog post).
Boatside once more, a laptop was connected to an RF401 radio transmitter (powered off the boat's battery) to communicate with the newly-powered station and confirm that all instruments were functional. All equipment was confirmed to be operating as expected, except the satellite transmitter (which would be confirmed operational later that day, after several hours of transmissions were received) and the solar panels (whose correct operation is inferred from the daily rise in station battery voltages, which would not be confirmed until the next morning's sunlight). There remained only the "tidying" phase of the operation: divers/snorkelers retrieved the "groundtruth" CT (which is only connected to the station during maintenance and cleaning), clipped off the ends of all cable ties, and attached a rubber sheet to protect the underwater cables at the waterline. Aloft, all of the external openings to the electronics chamber were plugged with aquaseal and a dozen dessicant packs were left inside before closing it up. The last important step was the installation of the grounding wires to connect all of the station's aluminum masts to one another, to the lightning diffuser brush (the station's highest point), to the station electronics, and to a zinc plate on the outside of the pylon near the ocean floor. When all work was complete, the station's safety lines and climbing rungs were removed.
The team is extremely grateful to the staff of and visitors to the Little Cayman Research Centre for their hard work and warm welcome, including but not limited to Dr. Carrie Manfrino, Lowell Forbes, Jon Clamp and Brenda Gadd. Myfanwy Rowlands is also to be commended for her amazing photo and video footage from the operation.
Photo credits for this post: J. Dupont (underwater work) and M. Jankulak (control unit)
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