All operations were successfully concluded.
Diving operations went as follows: in Tuesday's first dive, three of the station's eight lines/chains were cleaned. In a second dive that day, the four underwater instruments (shallow/deep CTDs, shallow/deep light sensors) were retrieved to the boat and there they were replaced with newly-calibrated instruments. Also, the "groundtruth" CT sensor was attached during this dive. The remaining lines and chains were cleaned during a dive on Wednesday, and during a final dive on Thursday the cables were secured and all loose ends were clipped or tidied (and the "groundtruth" CT was retrieved).
Surface operations began Tuesday afternoon, with the installation of the climbing rungs and safety line and the removal of the three aluminum masts and their instruments (Vaisala's "weather transmitter," an anemometer and the surface light sensor). Tuesday's operations were concluded with the removal of the "brain" control package that includes the datalogger and satellite transmitter. There were no surface operations on Wednesday; rather, Wednesday afternoon was spent in the lab swapping out the instruments on the retrieved masts and connecting them to the "brain" for testing. At this time, locally-stored data were retrieved from the memory module and a new program was uploaded to the datalogger. Surface ops concluded on Thursday morning with the reinstallation of the surface masts/instruments and the "brain." The station was confirmed to be operational from the boat (via radio transmitter) before leaving.
Some specific notes about the station follow:
The deep light sensor is mounted on a sturdy platform, but the shallow light sensor still uses the older allthread-type mount. The shallow mount is very flimsy -- it had been shored up with several connected hose clamps which broke during our work, and were replaced by us later in the week. This is a concern because the instrument had a noticeable tilt, off-vertical, when we arrived. The newly-tightened hose clamps appear to have corrected this tilt for now (see photo) but I would recommend that the entire mount be replaced with something more effective.
On Thursday morning, there was a large bird (identified to us as a booby, see photo) sitting on the upmost platform of the station, which is the satellite transmission antenna, when we arrived. This bird was extremely bold and remained on the station while I climbed to the top. After securing myself by the waist to the top of the pylon, I was able to shake the bird loose. It returned once, I scared it away once more, and throughout the rest of the morning it remained in the general area. I mention this because I noticed that the PAR values reported by the surface light sensor suspiciously dropped below the light levels reported by the underwater instruments a few times in the days since our work was completed. The presence of this bird (and others) may also affected readings from the other surface instruments.
- There has long been a problem with the wind data reported by our Vaisala "weather transmitters" on this station. Initial data from this newly-replaced instrument suggest that this is still a problem, although it will take a few weeks to make any definitive pronouncement on this point.
- For the record, the CTDs on this station are hose-clamped directly to the pylon; there are no CTD mounts in use on this station.
- This station is unique in that its internal conduits open underwater; at all other ICON stations, the cables emerge from the internal conduits just above the surface. There are two conduits, one on each side of the pylon, and each conduit has openings at three spots down the length of the (underwater) stick. However, only the uppermost conduits are used for instrument cables. The deep instrument cables emerge on one side and all other instrument cables emerge on the other side.
(signed)
Mike Jankulak