The structures in the ocean change on time scales shorter thanthe time required to deploy a seismic system, acquire the data and retrieve the system, that can be at least many hours. Also once the seismic system is deployed the ship cannot not stop for a CTD cast. We therefore used expendable bathy-thermograph (XBT) probes to constrain the water mass structure while shooting seismic. The XBTs provide the background thermal structure and high vertical resolution needed to corroborate the seismic data. We deployed 240 XBTs, of which 232 functioned properly along the seismic lines, ranging from once every 5 minutes to once every 40 minutes, depending upon the complexity of the water mass structure estimated from the last cast. Three different types of XBT were used on this cruise, T-5, T-7 and T-11, all manufactured by Sippican. The T-5 and T-7 sample approximately every 0.65 m down to 460 and 1850 m respectively. The T-11 samples approximately every 0.175 m down to 1850m. More information about each cast is contained in the header portion of each XBT file.
The data were recorded on a Windows 98 laptop computer afterlaunching with the Sippican hand-held launcher. The probes were launched by a two person crew; one inside monitoring the software display, and the other actually launching the probe. When the probe is loaded the inside crewman signals to start the launch, and when the display shows a sharp spike or other indication that the maximum depth has been reached, signals the end of acquisition. At the end of acquisition the outside crewman breaks the connecting copper wire and retrieves the spent XBT tube. Data were backed up frequently on the ship-board network hard drive.
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