Exciting Times On Leg 2 and Much Gratitude

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Primary Node PN1B is on its’ way to Newport for loading onto the I.T Integrity Cable Ship. Credit: L. Nielson, University of Washington, V21.
The Science Interface Assembly removed from Primary Node PN1B and brought onboard the R/V Thompson, latched to the underbelly of Jason. Credit: M. Elend, University of Washington, V21.

It was under sunny skies and with much excitement that the R/V Thompson began its journey out to Primary Node PN1B to help with the recovery operations.  The nodes are ~18 ft long substations on the seafloor that provide 8,000 watts power and 10 Gb bandwidth to the underwater cabled observatory through the fiber optic cables. Last summer, unfortunately, PN1B failed. During this past year, RCA Lead Engineer Chuck McGuire and Lead Field Engineer Larry Nielson, for the Regional Cabled Observatory, led the efforts to ready a spare Primary Node and to conduct extensive testing of the node so that it could be swapped with the failed node during Leg 2.

Primary Nodes are complicated ‘beasts,’ with very heavy titanium housings, a bundle of fiber optic cables, wet mate connectors, and switches that needed to be reconfigured and tested in preparation for the installation. After a lot of long hours and hard work, testing showed that all was ready to go and the node was mobilized at the RCA Logistics Facility in Seattle for transport to Newport.

A recovery bridle is attached to the top or Primary Node PN1B. Credit: UW/NSF-OOI/WHOI, V21.

The second phase of this effort was to secure a specialized industry cable ship that could recover the heavy nodes, which weigh 14,000 lbs out of water (not including the >1200 m of attached submarine cable). The nodes include three components: 1) a Backbone Interface Assembly (BIA) that down-step high power to lower power, which is utilized by the RCA submarine secondary infrastructure – e.g. secondary junction boxes, instruments, and cabled moorings; 2) A Science Interface Assembly (SIA) that provide power and communication to the secondary infrastructure through extension cables with wetmate connectors on the SIA. Note, in contrast, the Primary Nodes are “hard wired” to the backbone cables, which can be nearly 300 km in length and which are buried, at water depths less than 1500 m, to 1-2 m beneath the sediment along the Cascadia Margin; and 3) At depths less than ~ 1500 m, the BIA and SIA are covered by a large frame to prevent possible trawling.

Primary Node PN1B almost on deck of the IT. Integrity. Credit: C. McGuire, University of Washington, V21.

A contract was secured with It International Telecom Inc to use their cable ship the IT Integrity  to conduct the critical operation of recovering the Primary Node and its two connected backbone cables, up through  ~ 1240 m of ocean water (~ 4070 feet).  To lighten the load for recovery operations, the ROV Jason dove during Leg 1 and disconnected and recovered the SIA, and disconnected a 10 km extension cable that feeds RCA infrastructure at Southern Hydrate Ridge.  They also connected a recovery bridle to the top of the Primary Node – ready for arrival of the Integrity.

On August 10th with much anticipation,  the two >200 ft long ships met at Primary Node PN1B to begin this long awaited, and exciting operation. The IT Integrity, with APL engineers Chuck McGuire, Eric Boget, and Paul Aguilar onboard, deployed a frame <100 m away from PN1B on a recovery line to the seafloor. The frame, a bit smaller than a secondary junction box, included some additional line, figure 8’ed onto the frame that terminating in a hook to attach to the recovery bridle. The ROV Jason was deployed with the R/V Thompson standing off ~1 km from the Integrity, and cautiously drove to the frame – it required recovery of the frame and a redeployment, but on August 11, Jason unfurled the figure 8 recovery line, and easily attached the hook. Significant ship-to-ship discussion occurred between the Integrity and Thompson during this operation with two lines in the water and heavy packages. Jason backed off and the Primary Node was hoisted slowly and carefully to the deck of the Integrity. Jason latched into the frame and brought it back onboard the R/V Thompson.

PN1B onboard the Integrity with backbone cables attached. Credit: C. McGuire, University of Washington, V12.

At 1940, with a huge sigh of relief and with much thanks to the APL team on the Integrity and Thompson, the IT Integrity crew, and Jason,  the NODE ARRIVED SAFELY on the deck of the Integrity.

The R/V Thompson transited to Slope Base to swap out a junction box, and the Integrity, following removal of the two backbone cables from the node, began its transit to Newport to demobe PN1B and mobilize the replacement. We are much looking forward to the final phase of this effort in the next day or so to install the new node and get the south line of the RCA up and running again.

The Integrity will arrive back at PN1B late this afternoon, to commence final installation operations.