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Now there are three

The third and final broadband seismometer installation of this summer's cruise was completed on 17 September. It joins the two we installed at Barkley Slope and ODP 1027 to form a small networked array of seafloor seismometers. If all works out next year, we will install another broadband seismometer and four short-period seismometers at our Endeavour location.

Shifting Tactics

Original plans called for this seismometer to be deployed together with a battery pack, differential pressure gauge and acoustic current meter, but these additional components were not deployed. This decision came after a ground fault in an identical set of instruments at ODP 1027 forced us to recover them. It's hoped we will be able to augment the seismometers with back-up batteries and additional instruments during a future installation cruise.

Deployment Package
Deployment package for the ODP 889 seismometer. At left is the caisson. The seismometer rests on a foam pad in the centre. At right are blue canvas bags filled with glass beads.	Dalhousie University oceanographer Doug Schillinger (left) and Pacific Geosciences Centre instrument technician Bob Meldrum, 16 September 2009.	Dalhousie University oceanographer Doug Schillinger jokes with Pacific Geosciences Centre instrument technician Bob Meldrum prior to seismometer deployment, 16 September 2009.

We had to make another quick adjustment during deployment. The ROPOS tool basket was rigged to hold the caisson, seismometer and 14 bags of glass beads. Then the tool basket was strapped beneath ROPOS and the two lifted by crane over the water. Only when the basket was lowered to the sea surface did we discover the weight distribution was uneven. When hit by a wave, the basket slopped to one side and three bags of glass beads fell from it into the sea. We had to abort the deployment, bring it back on deck and add three more improvised bead bags.

The new bags lacked the built-in spouts on our custom-made blue bead bags so ROPOS was sent down with a kitchen knife, with which to cut the bag open and spill the beads.

Spilling the Beads
The ROPOS kitchen knife glints menacingly as the last few glass beads drain from a bag onto the ODP 889 seismometer 17 September 2009.	Glass beads spill from a bag after it was torn open by ROPOS with a kitchen knife, 17 September 2009.	ROPOS uses a knife to slice open a bag filled with glass beads, 17 September 2009.
Close-up view of glass beads filling the ODP 889 seismometer caisson, 17 September 2009.	ROPOS empties two bags at once, as the seismometer was buried in glass beads, 17 September 2009.

Standard Procedures

Except for the above variations, our deployment followed the now familiar script. We:

1. set the deployment package down on the seafloor
2. found the instrument platform and extended the seismometer connection hose
3. plugged the connector into one side of a connection plate
4. plugged the seismometer cable connector into the other side of the connection plate
5. stowed the connection plate in a 'parking position' on the seafloor
6. chose a spot for the seismometer
7. set the caisson on the spot and jumped up and down on it with ROPOS to push it down into the sediment
8. used the ROPOS zip pump to excavate the caisson
9. poured glass beads into the base of the caisson
10. put the seismometer into the caisson
11. buried it and the caisson in glass beads
12. tidied up
13. recovered

Everything went relatively smoothly except step 10 above. When ROPOS was ready to place the seismometer into the caisson, it suddenly slipped from the manipulator hand and fell a short distance from just above the caisson into it. We're crossing our fingers that the seismometer will survive that jolt. So far, we have not had a chance to power it up and test it, but we hope an opportunity will open up shortly.

Installing the Seismometer
Clouds of sediment erupt as the zip pump is switched on to begin excavation of the caisson, 17 September 2009.	ROPOS uses both arms to carry the caisson, 17 September 2009.	ROPOS sets connectors for the seismometer onto the seafloor next to a sea pen and a brittle star. Brittle stars climb sea pens and spread their legs to catch plankton and other small particles carried by the current.
The seismometer connector hose was extended through a sea pen 'forest' and connected to the seismometer cable through a connector plate that fits in this 'parking position'.	ODP 8889 instrument platform with extension hose for the seismometer, 17 September 2009.	This brittle star slowly fled the commotion as the seismometer was installed, 17 September 2009.

One step forward...

On 16 September 2009, elation and a setback transformed the R/V Thompson fantail deck into a beehive of activity. After high winds and seas forced us to forego our planned cable lay at ODP 1027, we retreated to ODP 889, where relatively milder seas allowed a quick reconnaissance and troubleshooting dive.

We were quickly rewarded for this decision when, working with our shore station, we found and eliminated a ground fault that had shut down the instrument platform and connected bottom pressure recorder at this location. We were thrilled with this discovery. It meant we could proceed with installation of three important instruments at ODP 889. The news spread quickly and soon the deck was thronged with crew and technicians readying the instruments for deployment.

...one step back.

But the excitement was short-lived. During recovery of ROPOS, the umbilical cable somehow became looped, resulting in a severe kink. The cable was badly damaged and could no longer be used. The only option was to shorten the cable, cutting off the damaged section, and re-terminate it.

The Problem
Around 100m of umbilical cable had to be removed after a damaging kink rendered it unusable, 16 September 2009.	A damaging kink in the ROPOS umbilical cable developed during recovery to ship. This kink required ROPOS to cut the cable and re-terminate it before installation work could proceed.

(Click the images to view slideshow.)

ROPOS Umbilical: More than meets the eye

The ROPOS umbilical cable is unique because it is built not only to carry a heavy load, but also electricity and fibre optic communications to the vehicle. Sealed within the cable core are five main power lines, 6 steel-sheathed fibre lines and a number of auxiliary lines. This flexible inner cable is armoured with two helical wraps of high-strength steel wire.

Inside the Umbilical
The ROPOS umbilical cable encases a bundle of separate electrical and fibre optic communications cables. All had to be re-terminated and reconnected to their respective terminals on ROPOS.

(Click the image to enlarge.)

Saws, drills, chisels...

The cable passes into ROPOS through the lifting-point bullet, a heavy steel cone that fits onto a hinge atop the vehicle. To shorten and re-terminate the umbilical cable, the damaged portion had to be cut off and removed from the lifting-point bullet – a task easier said than done. When asked how to do this, crew member Dan Cormany replied, "patience, power-tools, some swearing and cussing."

The Extraction
After considerable effort, ROPOS crew member Dan Cormany was finally able to drill, pound, twist, chisel and yank the old cable plug out of the lift point, 16 September 2009.	ROPOS crew member Dan Cormany drills the old cable out from the centre of the lifting point bullet, 16 September 2009.	ROPOS crew member Dan Cormany cuts the old cable end from the lifting point bullet, 16 September 2009.

(Click the images to view slideshow.)

Refilling the Bullet Cone

Once cleared, the new section of cable had to be cemented into the bullet. ROPOS crew members did this by splaying the shield wires, arranging them in the cone, and filling the cone with a quick-setting glue called wirelock.

The Goop
Once the lift point bullet was cleared, the shielding wires were splayed and arranged in the cone-shaped cavity , which was filled with wirelock.	ROPOS crew member Jonathan Lee spectates as Dan Cormany (left) and CSSF general manager Keith Shepherd (right) pour wire lock into the lifting point bullet, 16 September 2009.

(Click the images to view slideshow.)

Rewiring ROPOS

Once the weight-bearing portion of the cable was re-set in the lifting-point bullet, the inner electrical and fibre optic cables were then routed to their required terminals within the ROPOS termination box. Then all sub-systems had to be tested.

Wires
ROPOS crew member Kim Wallace ducks too slowly to avoid the camera shutter, 16 September 2009.	ROPOS crew members Jonathan Lee and Kim Wallace (beneath the white hardhat) work on ROPOS electrical and communications wiring, 16 September 2009.

(Click the image to enlarge.)

Success!

This intensive activity was accomplished skillfully by the ROPOS team during the afternoon of 16 September 2009. Meanwhile NEPTUNE Canada scientists, technicians and students worked alongside them, readying the ODP 889 instruments for deployment.