Configuration and Engineering
ALOHA Cabled Observatory Installation
In this paper we provide an overview of the ACO system and instrumentation, the installation operation, and a sample of initial data. Sensors now connected to the ACO provide sound from local and distant sources and measure currents, pressure, temperature and salinity.
Communications protocol used in ACO
Schematics of the ACO
The video camera is working, but the lights have failed. The AMM and its instruments (CTD1, CTD2, FLNTU) are currently disabled. The pressure sensor has failed and is showing a dramatic drift
and unrealistically large oscillations.
The ALOHA Cabled Observatory (ACO) is one of but a handful of seafloor observatories worldwide connecting deep-sea science directly to the researchers who are working to understand the complex processes that occur there. This is a graphic description of the different modules that are part of the ACO.
For photos and descriptions of each module, click here.
This paper describes the communications protocol used in ACO.
The ACO is a prototypical example of a deep ocean observatory system that uses a retired cable. The ACO architecture uses highly reliable existing transoceanic cable systems to provide power and communications bandwidth.
The ACO consists of various modules as shown in Figures 1, 2 and 3. A "junction box" (JBOX) is connected to the telecom cable termination. The JBOX converts the telecom communications protocols to standard 100 Mb/s Ethernet, and has as well a hydrophone experiment module (HEM) with two hydrophones and a pressure sensor. Then the "observatory" (OBS) is connected to the JBOX. The OBS converts the dc current on the cable to 48 V and 400 V, and distributes this, the Ethernet, and timing signals to eight user ports. On the observatory are two acoustic Doppler profilers (ADPs), a temperature/conductivity instrument (MicroCat), and a light.
Two additional modules are connected to the Observatory. The AMM (ALOHA-MARS Module) seafloor secondary node and the camera. The AMM provides four additional user ports and has two CTDO2s and a fluorometer/turbidimeter (FLNTU). The camera with two lights and a hydrophone is connected to the AMM node.
In addition, a 200 m tall thermistor array/acoustic modem (TAAM) mooring system is installed. This mooring system has 10 thermistors spaced vertically; these are battery operated and recording data internally. This system is not connected to the Observatory.
AMM: The ALOHA-MARS Module (AMM) seafloor secondary node has two Sea-Bird pumped MicroCats (SBE-52MP) measuring Temperature, Conductivity, Pressure and Dissolved Oxygen (CTD1 and CTD2); and a WETLabs Fluorometer/Turbidimeter ECO-FLNTURTD-2027 (FLNTU). This module also provides four additional user ports.
(click on thumbnail to enlarge the image)