Observation Procedure

 The observation is performed by two groups: the "operator," who checks the vessel's position, operates the data recording software, and records the data in a field book, and the "field operator," who drops the probe into the sea from the stern or other exposed part of the vessel. This section describes the observation procedure using the XCTD system (Tsurumi Seiki TS MK-150N data converter, LM-3A hand launcher), which is widely used in Japan.

 Before the vessel arrives at the observation point, the observation preparations are made. After turning on the data converter, the operator starts the dedicated software on the data recording PC and completes the software observation settings. The field operator moves with the probe to the work location in the exposure area and connects the hand launcher to the data converter with the communication cable.

 Until the observation point is reached, the operator monitors the distance between the vessel and the observation point, and the field operator stays where he is. Each probe type has an upper speed limit for the vessel speed during the observation, so the operator instructs the vessel bridge to slow down below that speed. If the ship's speed exceeds the speed limit, the nichrome wire wound around the canister of the probe case will run out before the probe reaches the observation depth, resulting in the nichrome wire breaking and forcing the observation to end ( Fig. 3 ).

 One to two minutes before passing the observation point, the operator instructs the field operator to connect the probe to the launcher. The field operator follows the instructions and sets the probe (Fig. 5). Once the probe is set, the battery inside the probe will begin to be consumed. If the probe is set too early, it may run out of battery power during the observation, making it impossible to take measurements.

Fig. 5 Setting the probe on the hand launcher

コンタクトピン　Contact Pin

電極　Electrode

保護キャップ　Protective caps

篏合レバー　Fitting Lever

リリースピン　Release pin

a) Name of each part of launcher and probe b) Insert the probe into the launcher with the lever pushed up. c) Pull down the lever to engage the probe's electrode with the launcher's contact pin.

 The operator confirms on the software that the probe is connected and waits for the right moment to pass the observation point. As soon as they arrive at the observation point, the operator instructs the field operator to drop the probe, and the field operator immediately drops the probe toward the sea surface ( Fig. 6 ).

Fig. 6 Dropping the probe

a) Remove the cap from the case.　b) Pull out the release pin.　c)Tilt the launcher downwards and the probe will slide out from the case.

When the probe lands on the water, data recording starts automatically, and as the probe descends, the vertical distribution of water temperature and conductivity is drawn on the software. The field operator holds the launcher in place, taking care to orient the signal transmission wire so that it does not touch the hull of the vessel and break. The operator monitors the data and waits for the observation depth to be reached. Once the observation depth is reached or the probe has reached the seafloor, the operator instructs the field crew to cut the wire and remove the probe. The field crew follows the instructions, cuts the wire, and puts away the launcher and communication cable. The operator records the time, ship's position, depth, and other information at the beginning and end of the observation in a logbook.

 The flow of the XCTD observation workflow, divided between operators and field workers, is organized as shown in Fig. 7.

Fig. 7 Flow of XCTD observation

到着前　Before Arrival

到着直前　Just before arrival

観測点　Observation Point

観測終了　End of observation

オペレーター　Operator

船上局(データコンバータ・データ収録PC)の準備　Preparation of onboard station (data converter and data recording PC)

観測点までの距離を監視　Monitor distance to observation point

プローブセットを指示　Instructs to set probe

プローブ投下を指示　Instructs to drop probe

計測データを監視　Monitors measurement data

観測終了の確認　Confirmation of observation completion

データ処理　Data processing　

ランチャとプローブの準備　Prepare launcher and probe

現場にて待機　Standby on site

プローブセット　Set probe

プローブ投下　Drop probe

ランチャの保持　Launcher holding

ワイヤ切断　Cutting wire

ランチャの片付け　Clean up launcher