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Under Construction
HiStar Package This page provides information on the following: More practical information like specifications (including shipping weights, sizes etc.), lab, deck and ship requirements, and a packing list of the complete package can be found on the Loan Requirements page. The data product section describes the steps in processing, and what level of data is provided.
DESCRIPTION The package has been put together on a stainless steel cage and is generally referred to as the HiStar package as it is built around 2 hyperspectral absorption and beam attenuation meters, made by WET Labs and called by them HiStars. Also on the cage is a SeaBird CTD, altimeter, MODAPS+ sub unit, and (optionally) a backscattering meter. The MODAPS+ sub unit is one part of the MODAPS+ system which coordinates the power distribution and data acquisition. This system and therefore part of the HiStar package includes the sea cable and MODAPS+ deck unit. At this time we are also adding one or two ac-9 meters to the cage. For a list of what exactly comprises the package see the packing list in the specifications section of the Loan Requirements page.
HiStars are visible light spectrophotometers using dual optical paths to determine the transmittance due to absorption and attenuation. A white light source and 3 Zeiss spectrometers provide approximately 3.3 nm resolution in the visible portion of the spectrum from 400 - 726 nm. Sea water is pumped through each of the two removable flow tubes during a profile. It is anticipated that a 0.2 micron pore-size filter will be attached to the intake to one of the HiStar units to provide the absorption coefficient associated with dissolved materials. The other unit will be run unfiltered to provide the total absorption coefficient. The absorption coefficient of the particulate component can be derived from the two sets of measurements. For more details on theory or construction contact us or WET Labs. AC-9s The AC-9 measures spectral absorption and spectral attenuation over 9 wavelengths, also via dual optical path measurements. Further specifications of the AC-9 can be found at WET Labs. The WET Labs site also provides useful technical notes: Tech Note 002 (AC-9 data processing) Tech Note 003 (AC-9 manual correction) Tech Note 004 (AC-9 Quick Start Guide) AC-9 Protocol
A Sea-Bird SBE 25 sealogger CTD measures pressure, temperature, and conductivity. Several other parameters can be derived e.g. descent rate, salinity, density etc. Technical specifications on the CTD can be found from the Sea-Bird homepage. The CTD also powers and collects data from a PSA-916 sonar altimeter, tech specs to be found at Datasonics homepage. WET Labs MODAPS+ The MODAPS+ system controls and coordinates the power and data
acquisition for the instruments on the HiStar package. It consists
of a submersible unit on the cage The sub unit allocates power to all instruments and collects and
concentrates the data from all the instruments into one data stream.
The deck unit provides the power and receives and splits out the
data stream. More detailed technical specifications of the MODAPS+ system at WET Labs.
The HOBI Labs HydroScat-6 backscattering meter is not a portion of this package, but does exist in the SIMBIOS instrument pool and we anticipate that investigators may like to be able to mate the two systems together. This instrument measures the backward scattering coefficient at 6 wavelengths, there are also 2 fluorometer channels and a depth sensor. See the HOBI Labs homepage.
CALIBRATIONS An important part of the package's use is calibration, without good calibration data, results are much more difficult sometimes impossible, to process to a reasonable degree of confidence. It is recommended that, depending on the workload the package is working under, time for calibrations should be set aside each day (1 - 2 hours). Calibration casts are profiles run with 2 (or more) instruments using 0.2 micron filters on either both absorption or both attenuation sides. This allows direct comparisons to be made and offsets to be calculated.
In the future we will have a calibration histories page for all our instruments showing their factory and field calibration values. MODAPS+ is a system which among other things, integrates the data from the package into a single archive file. This saved archive file includes a time stamp on each instruments' data so that after extraction, the data sub-sets can be merged together as desired. Before merging, however, there is some preliminary processing. This preliminary processing consists of applying instrument factory calibrations and getting the data formats ready to be merged. The data is usually merged such that one or two ac-9's can be merged with the CTD data and because of file size concerns only one HiStar at a time with the CTD data. At the present time, data from the HydroScat is not merged on time, into the above files. It is processed separately after extraction and inserted into the merged files based on pressure. Hopefully these 'raw' merged files will be provided to the PI before leaving the ship, or else shortly thereafter. However they require further work before being considered fully 'processed' and also suitable for submission to SeaBASS. The in-the-field-calibrations will be applied as part of this next level of processing, and this level includes corrections for temperature, salinity and scattering. The 'processed' data set shall be provided to the PI within approx. 1 month of the end of the cruise.
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HiStars
SBE 25 CTD
and a deck unit / host computer in
the lab communicating with each other in real time via the sea
cable.
The host computer (usually referred to as part
of the deck unit) logs the data and its software is the control
interface for the system, e.g. switching instrument power on/off,
setting baud rates etc. The data may be fed to separate computers
straight from the deck unit, allowing instruments to be monitored in
real time as desired. When saved to the archive file the data from
each instrument is time stamped and this allows later merging of any
or all instruments based on time. See the data product page for
further steps and explanations in data processing.
Backscattering Meter
The pure water instrument calibrations are
performed on deck. "Clean" (pure) water is pumped through
the instrument and this calibration data is used to keep track of
instrument drift, if that occurs. Also with data from many
calibrations decisions can be made on how the 'cruise' offset(s) is
to be defined. For the complete calibration procedure read the
soon-to-be document: How to do a water calibration on HiStar or ac-9
(under construction).
SUBMISSION TO SEABASS IS THE RESPONSIBILITY OF
THE PI. SeaBASS requires specific header and data formats. There are
descriptions and examples on the