EXO Sonde performance at Speyside / Angel's Reef, 2013-present

This post is part of a planned series of posts to share the results of my recent evaluation of data produced by all of the CREWS/CCCCC buoys over their lifetimes, from 2013 to the present.  This post will discuss the performance of the EXO Sondes, which were deployed to collect sea temperature and salinity data but are also capable of monitoring other 'water quality' parameters such as turbidity, algae, fDOM, pH and DO.

At the Speyside / Angel's Reef buoy (ARTO1), performance by the EXO Sonde has been generally poor.  The Speyside EXO was first deployed on November 25, 2013 and this analysis is based on data collected through June 4, 2015.  Although this period spans a total of 556 days, ARTO1 experienced a few short maintenance operations that brought the buoy temporarily to land, so that the actual length of deployment over this period was only 552 days, or about 18 months' worth.

Here is a graph of sea temperature (°C, in blue) and salinity (PSU, in red) from ARTO1, plotted against decimal year:

Please click on this image to see it in larger form.

Over the course of the last year and a half, the EXO Sonde at Speyside has had four periods of time during which the EXO could be said to have produced reasonable sea temperature and salinity data:

• Nov 25, 2014 to Jan 22, 2014 (58 days, after which Sal goes bad)
• Mar 20, 2014 to Jun 6, 2014 (78** days, after which Sal goes bad)
• Sep 11, 2014 to Sep 22, 2014 (11 days, after which Sal goes bad)
• Mar 26, 2015 to May 8, 2015 (43 days, after which Sal goes bad)

**The 78-day period from March 20th to June 6th, 2015 includes a moment on May 20th when salinities abruptly drop by about 1 PSU and then continue to fall slowly for 17 days before becoming very obviously corrupted.  The May 20th drop occurs at the time when the EXO appears to have been physically disconnected from the buoy for two hours, judging from the absence of voltage data.  An actual salinity drop coincident with this (presumed) maintenance operation is not likely, though it is not clear whether this salinity drop should call into question the integrity of the salinity data record prior to this time or subsequent to it.  This analysis avoids the question by giving the EXO the benefit of the doubt and assuming that both pre- and post-drop data are reasonable, up until the probe very obviously fails on June 6th.  However a more conservative analysis would score this performance as 61 days (pre-drop) or 17 days (post-drop) of reasonable data, rather than the 78 days listed here.

As of this writing the conductivity probe at ARTO1 is nonfunctional, and has reported corrupted salinity data since May 8th and corrupted sea temperatures since June 3rd.

Based on these statistics the EXO's conductivity probe, which reports both sea temperatures and conductivities (from which salinities are calculated), has performed reasonably well for 190 days out of the buoy's 552 operational days, or about 34% of the time.

A similar analysis performed on this buoy's sister station at Buccoo Reef, Tobago (BUTO1) found that that EXO performed reasonably well for 263 days out of that buoy's 464 operational days, or about 57% of the time.  The complete analysis for that EXO may be found at this link.

(signed)
Mike Jankulak

May 2015 maintenance - Angel Reef

The Buccoo Buoy was inspected on 11 May 2015. While the anchor ropes and metal base required cleaning, the sonde, probes and protective case were relatively unfouled. Badic maintenace was conducted on the sonde. None of the probes required the copper antifouling tape to be replaced.  The sacrificial anode was replaced.

A calibration was not conducted on this trip, and the sonde was cleaned and re-installed.

Data from the Sontek ADP was collected. The unit seems to be working fine and the data looks good.

The status of RMY RH sensor remains the same.

March 2015 maintenance - Angel Reef

ARTO1 was inspected ans serviced over the period 14-17 March 2015.  Minimal cleaning was required at this site. Anchor ropes and buoy base were cleaned.

The copper coating on the sonde probes was still intact and in good condition and was not replaced. Calibration of probes was conducted.  However, the sonde was in re-installed until a 7 days later. The probes were maintained in a moist environment until the sonde could bere-installed.

The RMY temp/RH installed the previous month was not collecting data. The unit was inpsected and reinstalled, but the problem persists. On further correspondence with C-ARMs two other options will be looked at to correct the problem.

The Sontek ADP was also deployed on this trip.

Cellular communication was confirmed, but no RF communication could be achieved on the day.

The next visit is scheduled for the end of May 2015

February 2015 maintenance

Following the annual maintenance check conducted over the period 10-13 November 2014,  a further check was conducted from 4-5 February 2015.  The buoy was brought to shore and most instruments were functioning and we had no problem connecting via RF but there was no cellular connection. TheRMY tem/RH MET sensor previously removed in Nov 2014 for servicing was successfully re-installed.

The EXO2 sonde was calibrated and reinstalled.  The Conductivity/Temp sensor seems to be defective.  Temperature reading were quite low (as much as 15 deg C below ambient- ambient was checked against a handhelp YSI temp/conductivity probe). This seems to be a recurring problem. OIn september 2014 the Cond/Temp probe was found to be faulty, which was eventually returned to and replaced by YSI.

Minimal fouling was noted, but the unit was repainted with anti-fouling paint.  All anodes and copper coating seemed intact. and the probe would not calibrate conductivity. All was downloaded from both loggers.

Speyside CREWSannual maintenance

The Speyside CREWS was given an annual maintenance check over the period 10-13 Nov 2014. The buoy was brought to shore and all instruments were functioning and we had no problem connecting via RF but there was no cellular connection.  All data for the last year was downloaded from both loggers and is now in the hands of TT IMA.  The programs were re-loaded and the electronics were reset.  Cellular communications was restored immediately afterward.  The RMY temp/RH is in need of service/calibration  but all other MET sensors seem to be measuring accurately.  The Temp/RH was removed for service and sonde recalibrated  prior to re-deployment on the 11 Nov 2014.

On the previous basic servicing (September 2014), the sonde was not functional due to erupted batteries in the battery well.  These were replaced.  The Temp/Cond was also found to be faulty, which was eventually returned to and replaced by YSI.

The breakage of the wiper parking garage has been noted as a regular problem with the CREWS inhibiting the proper settling of the wipers, and may be something the design team should look at.

April 2014 scheduled maintenance

The Angel Reef CREWS given a basic maintenance service on 21st April 2014. No obvious physical damage was noted. Fouling was minimal and consisted of 3 barnacle spat.  The wiper "garage" was replaced, and the coper coating on the CT probe.  The failure of the Turbidity probe to pass the QC test remains unresolved (the same issue exist for BUTO1), even though it all seems right during the cal.  Recommended action is a firmware upgrade.

Possible error with barometric readings. Pressure ranges from 1013-1015 millibar throughout the day. A 1millibar change suggest a 10m displacement.

Angel Reef (ARTO1) Scheduled CREWS Maintenance

The Angel Reef CREWS (ARTO1) was serviced on 20/03/2014 after several months of basic maintenance. In January 2014 anomalous temperature and conductivity reading were detected and it was scheduled for maintenance in March 2014.

Pre-cal CTD

Depth: 1.11m     
Temperature: 26.98
Conductivity: 55352
Salinity: 35.14

Little fouling was noted at this site.  Mooring lines, the buoy and the hardware attached to the buoy remained intact and with no noticeable damage.  Mooring lines and the buoy  were fouled with few gooseneck barnacles, sessile barnacles and tufts of green filamentous algae.  The anchors remained intact with no cracks or weaknesses noticed.  The western most subsurface buoy has shifted up to the surface of the water, and will be adjust on next visit.

Little fouling was noted on the EXO2 and on the protective casing. Most of the copper coating surrounding the probes remained intact, but given the lenth of time since the last service they were changed.  The probes were thoroughly cleaned of all barnacles, algae and other encrustations. All debris removed from the threading and krytox gel reapplied to all ports prior to reconnection to the base unit.  On recalibration it was noted that the conductivity/temperature probe was faulty (during calibration it registered temperature of 1.xx e-9 and conductivity readings of 96500 in the conductivity standard) and has been replaced with a new probe.  The faulty probe has been sent to YSI from examination. The new probe passed calibration process.  A QC result was generated during the TSS calibration process for reasons undetermined.  This also occurred during the first installation of the CREWS.

Exterior of base of sonde on removal from CREWS

Exterior of top of sonde on removal from CREWS

Inside of protective cover of sonde on removal from CREWS

Some colonisation on sonde and state of sacrificial anode

Still intact copper coating

Some colonisers on cleaning brush and probes

barnacle growing on cleaning brush

Minor tear on copper coating