deployment

The deployment procedures used for the PRR600 (profiler) and the PRR610 (surface reference) are designed to follow the ocean optics protocols for SeaWiFS calibration and validation (J.L. Mueller and R.W. Austin, SeaWiFS Technical Report Series, V25, Feb 1995).  The deployment procedure for each of the instruments is outlined below:

PRR600 (profiler)

  • casts are made as close in time as possible to the SeaWiFS overpass (between 12:00 and 14:00 HST).
  • simultaneous to each cast, reference downwelling irradiance measurements are made with the PRR610.
  • to start the deployment, the sensor covers are first removed, and the sensors are checked for fouling and cleaned if necessary.
  • the instrument is then lowered into the surface of the water on the sunny side of the ship.
  • the instrument is left at the surface to temperature acclimatize for 2 minutes.
  • the instrument is brought back on board the vessel, and the sensor covers are replaced.
  • dark values are logged for one minute, and then the sensor covers are removed.
  • the instrument is returned to the water surface and again allowed to temperature acclimatize.
  • using a crane, the instrument is lowered from the water surface to approximately 170 m depth as far away as possible from the ship (to avoid ship shadow contamination).  Before October 1998, the instrument was allowed to freefall to depth; after October 1 1998, the instrument was hand-lowered to depth to minimize the amount of instrument tilt.
  • the instrument is then retrieved, using a winch to raise the instrument at an even pace.
  • the instrument is again allowed to temperature acclimatize for a minute at the surface.
  • the instrument is brought on board, and the sensor covers are replaced.  Dark counts are then again made.
  • the covers are then removed, and the whole instrument is rinsed with fresh water and allowed to dry.
  • each cast takes approximately 10 minutes to complete.
  • approximately every 6 months, a normal PRR cast is followed by a dark cast - this is a PRR cast with the covers left in place over the sensors.

PRR610 (surface reference)

  • the surface reference is placed on top of a mini laboratory on the ship's deck, free from shadow contamination.  This location is less than 20 m from the site of the PRR600 deployment.
  • note that this instrument is not  fitted with gimbals, hence the data show variability caused by ship movement as well as variations in cloud cover.  Gimbals are hoped to be fitted in the near future.

 

home

Webpage by Jasmine S. Nahorniak, Oregon State University.