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Cruise Report for NBP 95-07

Seismic Data

The multi-channel streamer manufactured by Innovative Transducers Incorporated of Fort Worth, Texas, turned out to be quite an interesting system. It is a solid, oil-less cable that has differential amplifiers built into the transducer groups in the streamer. This construction makes it easier and quicker to deploy and retrieve than more traditional oil filled streamers. In a controlled and sensitive region like Antarctica, this is also a more environmentally sound streamer. Physically, the streamer was 1500 meters long, with a 300 meter leader and 1200 meter active section that contained 48 differential channels. It had groups of five phones per channel placed every five meters, and six coil sets for control of six active birds.

The streamer arrived at the ship in Punta Arenas, Chile, on two large cable spools and was in three separate sections. Two pieces of the main active section and a section of leader. To complete assembly of the streamer the sections had to be spliced and connectors installed. My experience in electronics, particularly soldering, made me a prime candidate to assist with this effort. The mid-streamer splice consisted of securing the Kevlar cords (the Kevlar cord is the strength member within the streamer cable), hand splicing over a hundred wires, and sealing and potting the splice to keep water out. A connector was then added to the deck end of the streamer and a mating connector added to the deck end of the leader section. The next step was to pull the leader section through the main deck conduits up to the watch standing console where the Oyo-DAS recorders and bird and gun control equipment are located. The large diameter and rigidity of the leader cable made it difficult to pull through the bends in the conduit. With some sturdy knot work from my rock climbing experience and an idea I borrowed from a cabinet maker I grew up next door to (using dish soap as a safe lubricant that eventually dries), we were able to get the cable in - almost. As it turned out the leader section was about twelve feet short. We ended up having to splice on another section of cable for it to finally reach the equipment racks.

On the back deck, balancing the new streamer took several people a full day's work to get the bird collars mounted on the streamer and then get the cable properly weighted. This proved to be a long day and challenging work in the freezing temperatures and driving snow. Since the weather had deteriorated, seismic data collection was deferred. A later attempt to test the gear showed problems with the air gun deployment system. Deploying the seismic streamer and air guns in rough waters is a difficult task. Despite our best attempts, the buoys and hoses for the starboard side air guns became tangled with the gun rack and tow cable, and overnight the air hoses had gotten badly chafed and one buoy disappeared. The cold temperatures and rough Antarctic water also took its toll in other areas; four of the seismic channels and one of the bird control coils did not work properly, and air gun number five was leaking and had to be shut down. Through all of the problems and complications, however, we were able to collect about sixteen hours of multi-channel seismic data.

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