Working with the CTD

Mon, 3 Feb 1997
[CTD] stands for Conductivity-Temperature-Depth. It's a cylindrical steel-tube frame with its namesake sensors mounted near the bottom (along with numerous optional others), and Niskin bottles mounted upright all around the outside. The Niskin bottles have snap-shut lids on the top and bottom -- they start open. We put it over the side with a boom and a winch, and lower it to the bottom, while it sends us those namesake measurements up along the cable. Then we haul it up again, sending a signal on the cable to "trip" the bottles, snapping each shut on a water sample at a particular depth. We haul it aboard and do experiments on the samples.

Sun, 9 Feb 1997
The CTD package lives in a hangar on the starboard side, amidships. We open the hangar door, and roll the package out on deck using a little railroad car mounted to the deck. The process is reminiscent of the vehicle which carries space shuttles from the assembly building to the launch site.

We use a pair of guide ropes to keep the package from swinging around as the winch operator lifts the package into the air, over the side, and drops it in the water.

To get an idea of what deployment and retrieval look like, imagine a group of tiny bright orange marshmallow men running around under a big steel swinging erector-set creation.