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Satlantic Radiometer Time Series

The Satlantic Radiometers are light sensing devices that measure wavelengths and intensities of light in the ocean. They are usually deployed as a pair to measure light from above (downwelling light) and light from below (upwelling light).

Revision History

  1. 20110302: Beta product released
  2. 20140602: Major revision to better include ancillary data (depths, tilts), filtering, reliability fixes, improved documentation

Formats

This data is available in a binary .raw format. Content descriptions and example files are provided below.

RAW

This format corresponds to the data files produced by the Satlantic data acquisition software. This file format, together with associated calibration files, can be interpreted by Satlantic post-processing software (e.g., SatCon, ProSoft).

New RAW files are started at the start of each day or when the driver is restarted (this should account for configuration changes, site changes, etc).

In operation with the vertical profiling system (VPS), the radiometers are usually started and stopped at the beginning and end of each cast segment, 'up' or 'down', through the water column. This effectively breaks RAW files into cast segments. A cast specific data product, that explicitly segments the data into casts, will be made available with future improvements. For now, it is recommended that users compare the start and end dates of the files returned with the cast times that they can determine from plotting utility or from time series scalar plots of CTD pressure on the VPS. (To use the reference to plotting utility, change the date as needed and scroll down to see the depth data). When a file spans multiple casts, Prosoft's higher level analysis may not be useful or correct, see below.

RAW files are produced from data output from the radiometer. Prior to February 2014, the radiometers on the VPS did not have tilt sensors (Satlantic Downwelling Radiometer HOCR-ICSW (12106) Details | Documentation, Satlantic Upwelling Radiometer HOCR-RO8 (12107) Details | Documentation). These radiometers also do not have pressure sensors to measure the water. Such ancillary data is crucial for analysis, so for all radiometers, data for tilt and water depth is added as ancillary sensors into the RAW files. For the VPS radiometers, pressure data from the CTD (most likely device 12102) is converted to water depths using the International Thermodynamic Equation of SeaWater (TEOS-10). For the VPS radiometers, when necessary, tilts are provided by the on-board gyro, a Crossbow 440 Inertial System.

To ingest the ancillary data, the calibration files and instrument parameters need to document what has been added. A calibration file named MPR001.cal provides this information (for more on the RAW and cal file formats, see the file format specification). The analysis of the RAW files also requires the relative positions of the sensors; this information is built into the .cfs parameters file (provided below). The relative positions are discussed in the Prosoft manual, see page 15: '6.5.2 Configuring Sensor Distances'.

Calibration Files (.cal, .sip, .cfs)

Calibration files have several formats that all may be used with Satlantic's post-processing software ProSoft. CAL files are the raw format. They contain necessary metadata on the RAW file structure so they must accompany the RAW files in order to be read by any software. CAL files also contain information on the wavelengths measured and the intensity calibrations. Because a single radiometer may have multiple sensors and a RAW file may contain data from several devices, several CAL files may be needed for a RAW file. Therefore, to ease file handling, CAL files may be zipped together in a single .zip file; for emailing, security reasons, etc., these zip files are renamed to a SIP file. However! a SIP file does not contain all the information needed to read and process a RAW file: we still need the relative positions and the 'Frame Type' may need to be modified. This information is captured in a CFS file. Unlike a SIP file, CFS files only contain references to the source CAL files. So to use a CFS file, you will also need to have the CFS and referenced CAL files together in the same directory. To that end, the necessary CFS and CAL files are provided to users with RAW files together in a zip file. The necessary CFS and CAL files are determined dynamically by data availability as the RAW files are generated. In this way, users will always have the calibration files they need to process the data; expand the zip file and the data is ready to process.

SIP files are available in the instrument documentation pages (see the child pages of the radiometer home page).

Quick Start and Tips for processing the RAW file data using ProSoft

(Underlined text refers to user interface elements in ProSoft)

  1. Visit the Satlantic ProSoft webpage to download and install the post-processing software.
  2. Request Radiometer RAW data products from data search, download and unzip, creating a new working directory where ProSoft can create new files as it processes the raw data.
  3. Start ProSoft.
  4. Import instrument configuration and calibration: in the Processing Context / Current Instrument, click Import, navigate to the working directory, select a CFS file, then press save once it's done reading the file. (If you've done this step before, select the Current Instrument you will be working on.)
  5. Create a new/default Current Parameters, click New under current parameters, then Save As..., name it something like 'Default'. (You may create additional instances of Current Parameters and edit as necessary) 
  6. Process the data: select Multi-Level Processing Level 1 --> 4. This will bring up a window to select the RAW file to process (locate the working directory, then 'Add' a file to process. Recommend only working on one file at a time, as each file is likely from a different cast, unless the files span midnight. This is essential: make sure that the name of the RAW file you select corresponds to the selected Current Instrument you wish to process - check the date range and serial number in the CFS file-name you loaded in step 4, select a RAW file that fits within the time range and matches the serial number (i.e. HOCR-R08W). For a download of a single cast segment, there are normally 2 CFS files and 2 RAW files, one pair for upwelling and downwelling radiometers. Additional CFS files are added only when necessary.
  7. If ProSoft asks to confirm the pressure tare initial values, press ok.
  8. If there is a problem with the processing (ProSoft freezes), read the manual, see the following tips or contact us. We encourage our users to get familiar with the operation of ProSoft, see the ProSoft User Manual for more information. In addition, here are some tips to attempt to get ProSoft to work. First, restart, investigate and experiment with the Current Parameters. Following the steps above, but instead selecting Single-Level Processing, users should always be able to get to level 2. From there, users can visualize and export the data. For a problem in reaching level 2s, try turning off the 'Profile Edit' (this will disable exclusion of bad data, but you shouldn't have any problems prior to level 2s) Also try turning off 'Deglitch Profiler Data'. For problems in level 3, experiment with the bin intervals - larger can work. For level 4, some products are not supported. We've also found some problems with the progression of data. ProSoft appears to prefer a down-cast followed by an up-cast. In level 4 processing, water depth variation due to surface may cause problems. Users may need to combine files to get this to work, while cutting out some data at the top of casts. As noted above, we are working on improving this data product by integrating cast delimitation so that we can provide RAW files that are much easier to process.
  9. View or extract data from the HDF files produced, see the 'Tools' menu. Create ASCII data products, see the 'Ascii' menu. A quick with the HDF data viewer is a great way to get an initial sense of the data.
  10. Repeat steps 4 thru 9 for the remaining RAW files.

Discussion

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Following the steps above, but instead, selecting Single-Level Processing, users should always be able to get to level 2. From there, users can visualize and export the data.

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