The MARS Ocean Observatory Testbed

Main components of MARS


Like a power strip at the end of an oversized extension cord, the bright-orange MARS science node lies at the end of a 52-km (32-mile) cable connecting the unit to power and computers at MBARI. Electronics within the node can route electricity and data to up to eight science experiments, each of which may incorporate multiple sensors.

3-d view of MARS and Monterey Bay
A 3-D perspective of the MARS observatory site on Smooth Ridge, at the edge of Monterey Canyon. MBARI sits at the head of the canyon, about 23 miles away from the MARS site. This deep-water site is close enough to shore so that scientists can install or modify test instruments without spending days or weeks at sea. Image: David Fierstein ©2004 MBARI.
The trawl-resistant frame

The MARS science node consists of two pieces: the massive orange “trawl-resistant frame” and the electronics package, which fits inside this frame.

The trawl-resistant frame consists of a truncated pyramid made of steel plates that is 3.7 by 4.6 meters (12 by 15 feet) wide at the base and 1.2 meters (4 feet) tall. This frame protects the node's electronic components from boat anchors or commercial fishing gear. Its smooth corners and sloping sides are designed to prevent such gear from snagging. Doors on each side of the frame can be opened, allowing remotely operated vehicles to plug or unplug experiments.

The electronics package

The heart of the science node, the electronics package, consists of two titanium pressure housings suspended beneath a block of yellow buoyant foam. Inside one housing is electronic equipment for routing data and controlling power to the instruments. Inside the second housing is the equivalent of an electrical substation, to convert the high voltage in the cable to lower voltages used by science instruments. For technical details on how the science node works, see this page.

Electrical power
The MARS cable carries 10,000 volts of electricity directly to the science node. This high voltage minimizes power loss as the electricity moves through the 52-km (32-mile) seafloor cable. Within the science node, transformers convert the 10,000 volts to an instrument-friendly 375 and 48 volts (DC).

Using the eight ports on the science node, each science experiment can send up to 100 megabits per second of data back to scientists' computers on shore. Scientists, in turn are able to send commands back to reprogram or reset their instruments.

Installing the equipment
The trawl-resistant frame was installed on the seafloor during the cable-laying process. Later, the science node, with its yellow floatation pack, was lowered into the frame by ROV Ventana, a remote-controlled submarine. Each time a new experiment is added to the observatory, the ROV will use its robotic arm to plug an underwater "extension cord" from the experiment into one of eight "wet-mateable connectors" (waterproof power and data outlets) on the side of the science node. After being plugged in, each experiment will communicate directly with electronics in the science node or use a science instrument interface module to convert power and data from the science node into so that they can be used by the experiment.


The undersea cable

The MARS power and data cable follows a 52-km (32-mile) arc across Monterey Bay to the MARS observatory site. This curved route was chosen to avoid areas of rocky bottom and submarine landslides around Monterey Canyon. Along most of its route, the cable is buried about one meter (three feet) below the seafloor to minimize its effects on marine life and reduce the chance of its being snagged by anchors or fishing gear. In order to minimize the cable's impacts, MBARI scientists spent over a year studying the effects of a cable that runs offshore from Half Moon Bay.

This illustration shows the MARS science node in its trawl-resistant frame. The main MARS cable from shore enters the node from the left. On the right are four of the eight "extension cables" for individual MARS test experiments. Steel doors on the sides of the node can be opened so that remotely operated vehicles can plug or unplug connectors. Sophisticated electronics within the science node route data and convert the high voltage current in the cable to lower voltages needed by instruments. Illustration courtesy of L-3 MariPro.

MARS science node fits into trawl resistant frame
This massive orange-painted steel frame will protect the node's electrical equipment from damage by fishing nets and anchors. The frame was installed during the cable-laying process. Later, the main node, with its yellow floatation pack, was lowered into the frame by ROV Ventana. In this photo, you can see the the two pressure cylinders that contain electrical equipment for handling power and data. Photo courtesy of L-3 MariPro.

engineers work on wiring for one of the MARS node pressure canisters
Technicians Dick Littlefield and Jose Rosal work on the electronics that fit inside one of the MARS node's titanium pressure cylinders. After sealing, the canister will hang under the MARS node's yellow foam block (see above photo). Photo: Kim Fulton-Bennett (c) 2005 MBARI.


Last updated: Oct. 08, 2009