Shipboard Calibration Procedures

Redundant temperature, conductivity and oxygen sensors provided a transfer standard to monitor sensor health. CTD conductivity and dissolved O2 were calibrated to in-situ check samples collected during each rosette cast.

Pressure and Temperature: The final pressure and temperature calibrations will be determined when CTD No 1 is returned to AOML. Comparison of redundant temperature sensors are shown in Figure 3 and suggest a steady drift over the cruise.

Conductivity: Comparison of redundant conductivity sensors are shown in Figure 4. The CTD rosette trip pressure and temperature were used with the bottle salinity to calculate a bottle conductivity. Differences between the bottle and CTD conductivities were then used to derive a conductivity correction as a linear function of conductivity. Figure 5 summarizes the residual differenes between bottle and CTD salinities using only the precruise calibrations and offset correction determined from the WIMP leg. The CTD conductivity sensor appears to have drifted slightly.

CTD Dissolved Oxygen: Comparison of redundant oxygen sensors (not shown) suggest a steady drift over the cruise. Figure 6 summarizes the residual differences between bottle and CTD oxygens, suggesting some drift during the cruise.