Weather Watch

Large ship off SLO County shores has global mission

The ship Global Sentinel off the coast of Pismo Beach on Friday.
The ship Global Sentinel off the coast of Pismo Beach on Friday.

Over the past couple of weeks, readers have asked about a large ship stationed off Pismo Beach.

This vessel is called Global Sentinel, and its mission is to deploy submarine telecommunications cables across the world’s oceans. Global Sentinel is 478 feet long and powered by three 12-cylinder engines that drive three electric generators. She carries a crew of up to 138. You can follow her and other ships locations by visiting the Marine Traffic website.

Global Sentinel’s mission is vital. Believe it or not, satellites only transmit and receive less than 5 percent of the world’s electronic communications; over 95 percent of the world’s international communication is routed through cables laid on the ocean floor. At this time, these submarine cables link all the world's continents except Antarctica.

You may remember an old episode of “Gilligan’s Island” when a telephone communications cable was pushed into their lagoon by a big storm. In order to call home, the Professor broke into the cable by using a homemade blowtorch and tapped into the individual telephone lines. However, before they could make meaningful contact with the outside world, another storm dragged the cable back into the ocean.

Without these submarine cables that cross the world’s oceans, social media channels like Facebook, Twitter and Instagram probably wouldn’t exist. Hands down, these cables are the Internet’s largest and most important link.

One of the first persons to propose using a submarine cable to transmit data was Samuel Morse in the 1840s. The inventor of the Morse code, he submerged an insulated wire in the water of New York Harbor and telegraphed through it.

The first trans-Atlantic cable was laid in 1860 and landed in Ireland. In 1902, the first trans-Pacific cable was completed, which linked the U.S. mainland to Hawaii. These first submarine cables weren’t capable of transmitting very much information. Since these cables had no repeaters or amplifiers, extremely high voltages were required to get the data across, which produced noisy links.

Today, these cables utilize fiber optics, which can span distances of more than 8,000 miles and carry terabits of data at nearly the speed of light across the most of the earth. These modern fiber optic cables can transmit the whole of Wikipedia in one second!

These cables are typically less than three inches in diameter and weigh around 7 pounds per foot. Since these cables have to endure harsh conditions, many are buried in the ocean floor by an ocean-going plough that travels over the sea floor. Depending on the conditions, these modern cable-laying ships can deploy nearly 100 miles of cable per day. … Wildfires continue to burn throughout California. PG&E is serious about working with Cal Fire and other state and local agencies to do our part to reduce that risk — including helping educate our customers about fire safety, operating our own equipment responsibly and being prepared to respond. To learn more about how PG&E is helping to combat these fires, please visit