Testing at Main Endeavour Field
One of the most exciting accomplishments of the Fall 2010 installation and maintenance cruise
on the R/V Thompson was the successful deployment of instruments at the Main Endeavour Vent Field (MEF). After laying a 6 km cable across the precipitous mid-ocean ridge terrain from the node to the instrument platform site, five unique instruments were deployed: a short-period seismometer, BARS (Benthic and Resistivity Sensor), RAS (Remote Access Water Sampler), COVIS (Cabled Observatory Vent Imaging System) and an HD video camera. The HD camera developed problems shortly after deployment and had to be retrieved, but the other instruments were fully operational, providing researchers with unprecedented real-time data and a new perspective on this fascinating region.
Unfortunately, the month of October brought an unwelcome development. On October 20th, communication from the shore to the junction box on the MEF Instrument Platform was lost, and the instrument data streams stopped. One of the principal objectives of the July 2011 installation and maintenance cruise was to visit MEF and perform some underwater detective work to determine what went wrong at Main Endeavour.
Engineers developed a test plan with several contingencies: The first step was to test the junction box using a specially-designed testing kit which was sent down with ROPOS. If the junction box was found to be faulty, a new junction box and instrument platform was ready on the ship for replacement. If it was found to be operating properly, then some diagnostics on the cable would be performed. If communication could not be restored through the cable, then the individual instruments would be tested using test protocols supplied by the researchers responsible for the instruments. A test result showing a faulty cable would mean that MEF could not be brought online until September due to the necessity of installing a replacement cable. Unfortunately, this turned out to be the conclusion of our engineers.
On visual inspection, one of the cables which was supposed to be oil filled appeared very flat, which could put pressure on the optical communication fibres.
In a last ditch attempt to salvage the cable, we tried poking hole in the “oily,” to allow water to seep in and relieve pressure on the fibres. We tried puncturing the oily in several places with an awl, but unfortunately nothing happened. Based on these results, the installation of Tempo-mini will have to be postponed to September when we will have a new cable to replace the one currently installed. However, the good news from the tests is that the existing junction box, RAS and COVIS have all been confirmed to be working, and are ready to begin streaming data again whenever communications are restored.