DOLAN

The DOLAN Buoy has been maintained in the frame of the european MERSEA project. MERSEA ended in April 2008.
The DOLAN buoy has been finally recovered on the RV Poseidon cruise PO365. Also the DOLAN database server has been shut down end of 2008.
The DOLAN Buoy has been proved to be very reliable during the last years in terms of power supply, software stability and acessability via the Iridium satellite link.

 DOLAN_Iridium_Workshop_Tempe_full.pdf

Slices for the presentation at the Iridium workshop at the Iridium Satellite LLC in Tempe, Arizona in April 2006

The last maintenance was carried out in November 2007.
The following sensors are online:
- Air temperature
- Air relative humidity
- barometric pressure
- Microcat @ 0.5 m
- Microcat @ 10m
- Microcat @100m (problems in power supply)
- GPS via ORBCOMM
- GPS via INMARSAT mini-C
- fluorometer @100m (problems in power supply)
current problems:
- houskeeping data indicates a malfunction of the windgenerator
- the 10m microcat does not send data according to the schedule
(possible empty Microcat battery)

The existence of the DOLAN moorings, located 60 nm north of the Canary Islands, are going back to the terminated BMBF funded project Data transmission in the Ocean and lateral acoustic network in the deep sea (DOLAN), which in fact was the prologation of the prototype testbed DOMEST. The main element of the DOLAN buoy mooring is the bi-directional satellite telemetrie, installed at the DOLAN data buoy. Finally, after termination of the project the mooring systems were converted to the EU-project ANIMATE and afterwards to the MERSEA_IP.
The main focus of MERSEA_IP is the installation of a European Marine Environmental Monitoring and Forecasting system. For this reason, several bio-geochemical sensors are now attached to the DOLAN mooring line and implemented into the satellite telemetrie. The overall scientific goal is to get access to actual weather data from the buoy, CT-data from below the buoy out of several depths and Fluorometer and Nutrient data from 100 m waterdepth.

The components of the DOLAN system

The infrastructure of the DOLAN buoy has been improved during the last years in order to meet the changing scientific requirements.
The DOLIX computer has been developed and was installed first in 2004 for testing purposes.
A new CAN bus telemetry has been developed in 2005 and was integrated into the DOLAN mooring first in December 2005.
The current focus is on near realtime data transmission of meteorological data as well as data from chemical sensors in the upper 100m of the water colum.
The whole system consists of the following subsystems:

Sensors
There are currently two groups of sensors in the online telemetry integrated. The first group consists of meteorological sensors like air temperature, the relative humidity and barometric pressure. The wind speed and direction is calculated and averaged from the wind sensor and compass readings.
The second group contains oceanographic data ike salinity, temperature and pressure from 0,5m, 10m and 100m as well as fluorometer and nutrient data from 100m depth.

Telemetry Computers
The sensors are connected to one of the two telemetry computers, the ORBCOMM Telemetry computer and the DOLIX computer.
The ORBCOMM telemetry computer is based on a simple but reliable microcotroller board with four serial RS232 interfaces. The received data is prepared for the transmission via the ORBCOMM transceiver.
The DOLIX computer is based on a low power Linux computer which can record data from several interfaces like 10baseT, RS232/422/485 and CAN bus. The sensor data as well as housekeeping data can be stored on a cf card and selected data can be sent via the IRIDIUM satellite link. It is also possible to access the system, upload new software, download files and control the whole system with a data call to the iridium modem.

Satellite Links
There are currently three satellite links installed. The ORBCOMM link is used for the telemetry of sensor data, The DOLIX computer uses the IRIDIUM link for data transmission and system maintenance. The INMARSAT mini-C link is currently only used for tracking purposes.

Supervisory and Power control
It is essential for an autonome system to have an good control on the housekeeping data of the system. This includes the monitoring of temperatures as well as power consumption and voltage control of the different systems. A fault detection shall help to disable systems which show a malfunction or trigger corrective actions. This Power control board can be controlled by the DOLIX computer. The logging of the housekeeping data will be performed by autarc dataloggers and the DOLIX computer.

Database & online quality control
The data sent via the different satellite links are achieved in the DOLAN database in Bremen. The data is extracted automatically from the raw data and the readings are quality controlled by algorithms implemented in perl. The scientific quality controlled data goes into the database and is accessable via SQL querys. This could be done directly by Open Office documents, Excel or other software which can handle ODBC datasources.
The DOLAN homepage displays the charts by the use of PHP scripts and offers also a data extraction page. This page will provide a comma separated file (csv) for the import into other software tools.