Have you ever wondered how we recover instruments from the bottom of the ocean? It's okay if you haven't, I hadn't either until about a week ago. The process doesn't involve highly trained dolphins, but in some cases is almost as cool:
Let's start with a description of the instruments. Each ocean bottom seismograph (OBS) is composed of three pieces: battery, seismometer, and recording electronics. Each piece is housed in its own, bright yellow, pressure cylinder--which weighs about 100 pounds. To make matters worse, in shallow waters (less than 1000 m depth) we need to protect the instruments from trawl nets. Thus all of the shallow water instruments are defended by square pyrimidal armored steel plate structures about as wide as I am tall. I couldn't even guess how much these weigh but to move them around the ship we need to use one of the ship's cranes.
So how do we pick these up? Well, many of the instruments have buoys attached to them by long lengths of rope. When our ship nears the instrument we send an acoustic pulse which tells the instrument to release its buoy. Then the buoy floats up to the surface and we can drag the instrument up using the rope attached to the buoy. No highly trained cetaceans necessary. A lot of the time this goes swimmingly. However, sometimes corrosion or biology prevents the buoy from releasing. That's when (cue the heroic music) Jason is deployed.
Jason is an approximately cubic, unmanned, submersible robot. It's sides are a bit longer than I am tall. The front bristles with an array of cameras and two hydraulic arms. Six thrusters, positioned throughout the body, provide Jason with full maneuverability. The robot remains connected to the ship via an umbilical cord-like tether which goes another submersible named Medea (evidently someone at Wood's Hole was a greek mythology buff). Medea is lowered from the ship via winch and steel cable and remains close to beneath the ship while Jason is free to explore the bottom to the limit of its tether. The arrangement seems a bit complicated, but is probably the best way to reduce the risk of Jason getting tangled in cables and being lost to the deeps.
The Jason team (a group of engineers and pilots on board with us) controls Jason from a special, NASA command center like room on deck. There, three pilots sit in front of a bank of about 15 computer monitors displaying various video feeds from Jason and Medea. The three pilots work together to control Jason, Medea and the ship with a collection of computers and joysticks. Behind the pilots sit the scientists (including me). We get to control the science camera with a joystick--an xbox controller, truly--and are responsible for logging events of interest. Getting to sit in the room and observe is quite exciting (I'll upload photos as soon as I return).
It turns out I have to go and help with a recovery now so I will have to describe the actual Jason dives (the exciting part) the next time I get a chance with the internet.
To be continued.........
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