Some background: this location has played host to a CREWS/ICON station since June 15th, 2002. The station in its current incarnation was installed and went live on September 23, 2006. The last annual visit by AOML was in early July, 2009. There were several problems encountered in the field during this July 2009 visit, resulting in (1) the failure of the standalone air temperature sensor, (2) the failure of the RM Young Wind Monitor and Electronic Compass, and (3) the loss of communications with the station's "deep" CTD. These problems were somewhat mitigated by the existence of redundant air temperature and wind data from the still-functional Vaisala Weather Transmitter (WXT). Also, it was believed that the deep CTD could continue to run on battery power and store data locally for several months, and the "shallow" CTD appeared to be working properly.
Following this July visit, the maintenance contract expired on September 30th, 2009 (at the end of FY2009) and the station's last recorded monthly cleaning was conducted on September 10th, 2009. This means the station went unattended for a period of nearly 11 months (which is unprecedented in ICON history).
In the time since cleanings ceased, the functional shallow CTD lost its power feed from the main station (on December 24th, 2009). It continued to communicate its measurements to the station until April 10th, 2010, at which time its local battery power reserves were completely drained and the instrument went offline.
Regarding this trip in August of 2010: AOML for the first time collaborated with the good people of St. Croix's East End Marine Park (EEMP), see photo at right. We were extremely grateful for the hard work done by Paige Rothenberger, who coordinated the entire operation with AOML, and the very capable boatsmanship of Jose Sanchez who worked with us in the field. Paige and Jose made this operation go extremely smoothly and are in a large part responsible for the effort's success.
And success it was! All electronics were replaced on this visit, including the control electronics and antennae that have been operating at this site since September of 2006. We also installed a new navigation light (see photo at left) with high-intensity LEDs that increase the light's range from 3 nm to 4 nm. We were able to learn a lot about what had gone wrong during the July 2009 trip and in the time since. Accomplishments from this visit include:- The station's GOES (satellite) transmitter was replaced along with its satellite antenna and GPS antenna. The station's transmission success rate in the year to date has been about 90.3%, which corresponds to the loss of more than 2 transmissions per day (or more than 16 transmissions per week) on average. It's still very early for knowing how well the station is now transmitting, but in the eight days since the station came back online it has only dropped a total of 4 transmissions, which would represent a success rate of 97.8%.
- The station's 64 MB flash memory card was replaced with a 1 GB card. Where previously the station stored 10-minute data averages to local memory, it now stores 6-minute and 1-minute data reports locally from all instruments that report this frequently. The station will not exhaust its local memory reserves until early in 2013 (and the station will be visited much sooner than this for its next annual swapout).
- As mentioned above, the station's navigation light (which has operated in this location since 2002) was replaced with a new light.
The station's nonfunctional air temperature sensor was replaced with a new sensor. Where previously the air temperature sensor was located behind the station's solar panels, the new sensor is installed inside its own radiation shield (see photo at right). This results in much more accurate measurements. In the past, air temperature measurements from the two sensors (the standalone sensor, and the sensor integrated into the Vaisala Weather Transmitter) could differ by up to 2 °C; since the radiation shield was installed there difference has never been more than 0.51 °C.
The station's RM Young Wind Monitor and Electronic Compass (see image at right) have been replaced and are now fully functional. Whereas in the past the Wind Monitor used to be wired into the compass, which in turn reported data from both instruments, now each instrument is connected independently to the datalogger. This allows us to measure full 5-second wind gusts instead of the 1-second gusts we reported previously. The failure of these instruments in July of 2009 has been traced to a miscommunication amongst team members about the wiring of the Wind Monitor. A longer testing period in the weeks leading up to this visit ensured that this problem was not repeated.- The problem with the "deep" CTD (from July of 2010) was traced to a failure of the connector used at the top of the station. The 2006-era connectors were replaced for the Deep CTD, the Shallow CTD, and the WXT on this trip. Other connectors were thoroughly tested on land and found to be working properly. When the deep CTD's data were downloaded on this trip, we found that it operated on battery power for longer than expected, and data were retrieved for the period from July 8th, 2009 to January 4th, 2010.
The failure of the "shallow" CTD (see image at right) was determined to be due to the failure of its instrument-end connector. The second of four pins was broken and was loose. This probably occurred during the July 2009 visit but its impact was not serious enough to affect the instrument's operation until late December of 2009. The data downloaded from the instrument cover the period from July 8th, 2009 to April 10th, 2010. The problem was diagnosed on this trip and was fixed by replacing the instrument's entire cable, from instrument connection below the surface to its end at the top of the pylon (which it reaches via the pylon's internal cable conduits).
As expected, we found the station to be badly bio-fouled after its long period without cleaning. Our divers conducted five dives of approximately 60 - 70 minutes apiece to swap out the underwater instruments, document the station's condition in photos, and do an extensive cleaning of all surfaces, spectra lines, support chains and lashings.
In the eight days since the station went back online, the team has monitored the station's data feed and at the time of this writing all indications are positive. All instruments are communicating and are fully powered by the station. Transmission success rate has improved post-visit. The navigation light was seen to be working properly at nighttime. The hourly data reports are once again available online, notably the summary report and the report of six-minute wind data. The station's data feed to NDBC has resumed. The station's ecoforecast site is also fully operational.
We at AOML would once again like to express our gratitude to Paige Rothenberger and Jose Sanchez for their generous and able assistance to all aspects of this operation. We hope that this will represent the start of a long and productive collaboration.
(signed)
Mike Jankulak
[photo credits: Lecia Salerno and Mike Jankulak]