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| EXO data from the SWBZ1 buoy, from September of 2013 to January of 2016. |
I have spent some time going over what email and data records exist from the entire history of this buoy, in an effort to better understand:
- what went wrong with the station in the past
- what might still be going wrong with it
- whether any past data might be scientifically useful
Here is my reconstructed timeline:
- September 19th - 20th, 2013: This is when the station's data record begins, and judging from an email from Matt Previte to Jim Hendee, the actual deployment took place on Friday, September 20th. This email suggests that there were problems with the buoy's cellular service (provided by BTL, or Belize Telemedia Limited) but that some kind of workaround was allowing YSI systems at least to access the buoy's data in real time. AOML did not have any access to data from this buoy until the following April.
- October 23rd - November 14th, 2013: The buoy was completely powered down for these three weeks, judging by the jump in timestamps while data record numbers remain consecutive. Also the compass directions appear to be slightly different before/after the data break. It is likely that the buoy was recovered from its deployment site and either powered down completely or at least disconnected from the Met JB. This may have been part of an early attempt to resolve the issues relating to its cellular service. After November 14th the data record resumes and is suggestive of a buoy reporting from its deployment site (through April of 2014, anyway).
- January 7th - February 14th, 2014: While other parameters remain consistent with a buoy reporting from its deployment site, during this period there is no EXO connected. Either it was removed temporarily for some reason or it (or its communications with the buoy) failed completely.
- April 7th - 11th, 2014: The met/ocean data record ends on April 7th and the diagnostics-only data record begins on the 11th. Email from Matt Previte of YSI indicates that Jon and Albert had visited the buoy in order to work on the cellular service problem and, in fact, they fixed that problem. However they discovered "that the met canister was flawed at this site and was allowing moisture to get inside" and so it had to be removed and returned to YSI for evaluation and repair. While the Met JB was gone the buoy's Main JB electronics and datalogger continued to operate and AOML's systems started calling in (using the IP address associated with its cellular account) to collect data for the first time. Without the Met JB, however, only the Main datalogger's diagnostics tables were being populated (i.e. no met or ocean data of any kind). In fact this diagnostics data record will continue unbroken from April of 2014 to June of 2015, more than a year.
- June 27th - July 1st, 2014: Met data records were being logged for just a few day but none of the meteorological measurements are reasonable. The EXO appeared to be connected. Voltage levels seemed to be on low side. Since this is a period for which we have uninterrupted diagnostics data from the Main JB in Belize (with no sign of unusually low voltages) it is reasonable to conclude that the Met JB was powered up in some completely different location, possibly within the YSI facilities as part of their evaluation or repair of the Met JB.
- November 1st - December 2nd, 2014: Diagnostics records indicate that the main battery was not being fully charged during this month. This is possibly suggestive of some kind of human intervention but it is not known exactly what -- it could indicate that the buoy's solar panels were shaded from full sunlight for some reason or that the cable to the Solar Panel JB was disconnected temporarily. Given the timing of events before and after this month, my best guess is that YSI returned the repaired Met JB to Belize around this time, and perhaps there were some (unsuccessful) attempts to install it that impacted the charging of the battery. Note that the Met JB reinstallation failed because the JB was only connected to the met and ocean sensors but its main "umbilical" cable to the Main JB was never attached.
- June 25th, 2015: On this date the buoy (still reporting diagnostics, still without a connection to the Met JB, still without any met or ocean data reports) lost power. At about this time two other things happened: the WXT (integrated weather reporting system made by Vaisala) came loose from its mount and fell into the water, effectively destroying it. Also the buoy was physically moved from one side of the Caye to the other, where it would be closer to the dock and better sheltered from wind and seas. Later investigation suggests that the power failure was due to the solar regulator's Low Voltage Disconnect being tripped, which separates the battery from the payload (but not from the solar panels). Note that the power failure is unlikely to be related to the loss of the Vaisala WXT, because the Met and Main JBs were not connected in any way. The bare cable end left behind by the WXT had no source of power and could not possibly have caused any kind of short in the Main JB electronics.
- November 2nd, 2015: Mikes Shoemaker and Jankulak (i.e., me) visited the buoy for a few hours. This will be described in more detail in another post but we identified the issue with the solar regulator (and worked around it by rewiring the buoy to circumvent the LVD protection), bringing the buoy back online and making it reachable by cellular service once more. We noted the destruction of the Vaisala WXT, and that the Met JB's internal compass appeared to be reporting garbage data. We connected the EXO (though without any D-cell batteries installed) and left it reporting temperatures and salinities from the shallows where the buoy was moored.
- December 27th, 2015: While awaiting further repairs and eventual deployment the buoy has continued to report from its shallow mooring, but starting in late December AOML experienced communication dropouts. These communication problems are suggestive of a problem with the connection between the two dataloggers (within the Met and Main JBs) and also a potential power/recharging issue. These issues will be analyzed more thoroughly for another post.