System Description

The DELOS system comprises two environmental monitoring platforms: - one in the far field (5 miles form sea floor infrastructure); and one in the near field (within 50metres of a sea floor well). Each platform comprises two parts: - the sea floor docking station that is deployed on the sea floor at the start of the monitoring program and remains for the 20 year project duration; and a number of observatory modules that are designed to perform specific environmental monitoring functions. One of each observatory module will be available to each platform. Once deployed each observatory module will have enough battery and storage capacity for autonomous operation for at least 6 months. Towards the end of the 6 month deployment period each platform will require ROV (Remotely Operated Vehicle) intervention to recover observatory modules to the surface for service, calibration and data offload. During this service period no monitoring will be possible at the sea floor however, long periods of monitoring will be possible (months), interrupted by short service periods (days). The scientific steering committee concluded that this interruption to continuous monitoring would not significantly compromise the overall scientific objectives.

Sea Floor Docking Station

The sea floor docking station is designed to be deployed at the start of the program and left on the sea floor for the 25 year project duration. It consists of a robust triangular glass fibre construction designed to withstand long term sea floor deployment and periodic service by ROV. Glass fibre is used to eliminate any corrosion effects which may affect sea floor biological processes. A major research project was conducted to determine the long term effects of glass fibre deep water immersion and the final design encompasses this research.

To minimise disturbance to sea floor animals from sea current eddying effects due to the sea floor structure the docking station is raised off the sea floor on legs. This design enables the observatory modules to sample both the water column above the docking station as well as sea floor processes below it.

Observatory Modules

Each observatory module contains a suite of related instrumentation housed within either a standard size or over-size observatory module frame. For ease of data offload and instrument programming a controller is also situated within each frame. The controller deals with different interface issues for each of the sensors and instruments enabling a standard programming interface to be presented to the user. It also acts as a backup, storing a copy of each sensors data in a central location.

Observatory modules are designed to be placed into the sea floor docking module by ROV. Each module will have sufficient battery and memory capacity to operate for a maximum of 6 months. All instrumentation including batteries and memory will be confined within the dimensions of the standard observatory module frame designs. During transportation or storage the frame protects the instruments within and also allows easy access for crane or forklift operations.

Near Field Platform Observatory Modules	Far Field Platform Observatory Modules
Camera Module	Camera Module
Oceanographic Module	Oceanographic Module
Acoustic Module	Acoustic Module
Guest Module 1	Sediment Trap Module
Guest Module 2	Guest Module 1

Periodic Service Procedure

Every 6 months the observatory modules must be removed from the sea floor platform by ROV and returned to the surface for data offload, instrument calibration, and battery charging. The illustration below shows the procedure required to service the far field platform. The near field procedure will be very similar.


A After 6 months on the sea floor Observatory modules needed to be returned to the surface for service	B Under program control or via acoustic command the sediment trap that has been collecting fallout from the surface layers reels back inside the sediment trap observatory module	C A Field Support Vessel (FSV) with ROV returns to the DELOS site and deploys an empty deployment basket (basket not shown)	D Using the ROV and ships dynamic positioning, one by one the Observatory modules are removed from the DELOS platform to the deployment basket

E The process continues until all observatory modules have been moved from the DELOS platform to the deployment basket	F All observatory modules are then recovered to the surface for service	G Whilst the observatory modules are being serviced no data collection is possible. However, the service will only take a short time (days)	H When all the observatory modules have been serviced they are redeployed in the deployment basket

I One by one the serviced observatory modules are returned to the DELOS platform	J The process continues until all observatory modules are loaded	K Once completed the FSV can leave and service the near field DELOS platform. This platform will not required any further intervention for another 6 months	L Under programmed or acoustic command the sediment trap is redeployed 100m above the DELOS far field Platform