Bi-directional communication into the deep ocean based on OrbComm satellite transmission and acoustic underwater communication

At the end of 1997 the DOMEST projects started. The aim was the development of a moored sensor network in the deep ocean near the Canary Islands. With the implementation of a bi-directional satellite link and underwater acoustic modems, a data-link from land into the deep sea should be established on a daily basis. With DOMEST, remotely controlled measurement of element and particle transport in the deep sea will be possible. Remote control includes access to a variety of data without recovering sensors from the deep ocean. Data access will be possible at any time via the Internet and satellite communication. Sampling intervals can be changed interactively from land, status data from the instruments can be checked and it is possible to download the data subsequently. These possibilities allows an advanced sampling and probing of parameters depending on various environmental parameters, such as satellite derived ocean colour or particle input during dust storms. Communication underwater is based on 4 independent acoustic modem clients, combined with different sensors. Bi-directional data transmission between these modems is possible up to 2,400 baud. Each sensor package and acoustic modem is controlled by an integrated digital controller, responsible for hand-shaking and data-management. At the sea surface, a permanent surface buoy is moored in 3,600 m water depth. Above water, the OrbComm based satellite network establishes data transport between the moored systems and the land based ground station in Italy. At the ground station, messages are routed via SMTP into the Internet. During a scientific cruise of RV METEOR in May 1999, the first close-loop test-with a data request from a ship via satellite into the deep sea and back via satellite to the ship-has been performed successfully, within less than 8 minutes. The final configuration of the complete DOMEST mooring will be deployed at 3,600 m water depth over a maximum duration of one year. New sensors will provide high-resolution data on particle fluxes and element concentrations in the deep ocean.