Technologically, at least, VENUS and MARS are halfway to NEPTUNE. Imagine several VENUS nodes and their science instruments plugged into two dozen MARS nodes all spread out over hundreds of thousands of square kilometers, and you begin to get an idea of the potential scale of a fully deployed NEPTUNE. The final challenge is to build a data and power backbone to link the far-flung nodes.
The NEPTUNE teams based their initial backbone designs on terrestrial networks. The communications system design, led by Woods Hole senior scientist Alan Chave, mirrored the mix of optical fiber and electronics employed by the Internet. At each node, the incoming optical signals would be converted to electronic data packets and fed to an electronic router. The router would then send individual packets to the node's scientific equipment or to laser transceivers for beaming down another stretch of cable to a neighboring node.
NEPTUNE's power designers, though lacking a terrestrial model of a dc distribution network to follow, nevertheless stuck to the principles of terrestrial networks. The scheme for protecting the power system from shorts and other troubles relied on several layers of relays--being used essentially as fuses--and extensive communication with the shore station.
Both designs had a potentially fatal flaw: dependence on complex electronic equipment in the nodes deep underwater. This dependence violated the credo of undersea telecommunications engineers, according to NEPTUNE Canada's Peter Phibbs, a 20-year veteran of the undersea cable industry. "The basic theory of submarine telecom systems is to put nothing underwater!" he says, a bit facetiously.
Experts at Alcatel Submarine Networks SA, in Nozay, France, the company responsible for many of the world's undersea optical-fiber data cables, drew attention to the problem. Alcatel had invited the NEPTUNE communications team to Greenwich, England, to consider a concept that would let data keep flowing through the backbone even if power were lost at a node.
Part of an optical fiber's amazing ability to transmit torrents of data comes from the fact that it can carry many wavelengths of light at once. In the original scheme, all the wavelengths of optical signals employed by NEPTUNE were to be converted to electronic ones and then transformed back into optical data again within each node. So losing power at that node would stop the flow to other nodes downstream from it.
Alcatel proposed that, instead, each node's data should be encoded on one or a few dedicated wavelengths of light. Then, passive optical filters in the backbone, which require no power to operate, would divert just the wavelengths intended for a node to that node, allowing the rest to continue on to other nodes. So, rather than have the data line pass through a node, it would run alongside it, with only that node's data diverted in. Similarly, data generated by the node's instruments would be encoded on that same wavelength and fed back into the backbone's optical fiber for transport to shore.
Noting a similar overdependence on complex electronics in NEPTUNE's power system, one of Alcatel's senior power engineers, Phil Lancaster, and JPL's Harold Kirkham decided that the NEPTUNE system that protected nodes against power outages and overloads needed to be reworked as well.
The resulting redesign "really opens a new frontier for power engineering," says IEEE Fellow Chen-Ching Liu, a professor and associate dean at the University of Washington who is an expert in power grid protection and a member of NEPTUNE's power group. As with the optical fiber, the power line in Lancaster and Kirkham's alternative design no longer runs through the node. In their approach, the backbone contains its own breakers and their simple controls, while the node resides on a spur that branches off from the backbone. The innovation that makes that possible is in how the system handles a fault.
"The traditional concept says if a segment of the cable is bad, then I try to disconnect that segment to keep the rest operating," says Liu. The result is a partial outage with much of the system unaffected. "The new concept says we can afford to shut down [the whole system], but then we bring it back as quickly as we can."
Imagine that a fishing trawler breaks open a cable and short-circuits it. The current on the cable will surge, and the shore station will automatically shut off the power. The question then is how to find and isolate the damaged part of the cable and bring the rest of the system back online. NEPTUNE's first design would have relied on instructions delivered via the communications equipment within each node to test the condition of each segment of the cable and set the system's breakers--opening them near the damage, closing them everywhere else. That presents a catch-22, because the node's rather complex communications system needs to be powered and operational for the scheme to work.
In the redesign, the breakers automatically determine whether or not they should be open or closed with a little help from a signal sent from the shore station along the power line itself--a low-voltage pulse of reversed polarity. When the voltage reverses, a timer associated with each breaker starts counting down. The timer is set to a time proportional to the voltage at the breaker. The breaker closest to the damage will have the lowest voltage among them all and will trip first, thereby isolating the trawler-torn segment. Meanwhile, the shore stations measure the total resistance of the cables and feed that information to a system simulator to determine the location of the fault, so a repair ship can be dispatched.
As impressive as its engineering has been, NEPTUNE faces an uncertain future. Whereas Ottawa awarded Canadian $62.4 million (US $51 million) to the University of Victoria to build the 30 percent of NEPTUNE that lies in Canadian waters, funds to build and install the U.S. side of NEPTUNE have yet to materialize.
The latest in a series of bureaucratic roadblocks is the National Science Board, in Arlington, Va., which controls the release of funds for "big science" projects in the United States. The board recently bumped ocean observatories, NEPTUNE included, down a notch. It seems the Arctic science research ship that took NEPTUNE's place in the funding queue enjoys vigorous support from Alaska's influential congressional delegation.
As a result, the NEPTUNE concept that began in the United States has become--at least for now--a largely Canadian venture. And the Canadians are plowing ahead. This summer the University of Victoria selected Alcatel to lead the final engineering, construction, and installation of their equipment, and data could start flowing to the Internet in a little over two years. "The Canadians have done brilliantly well at getting their act together and have shamed the U.S.," says JPL's Kirkham.
Going it alone is a decidedly mixed blessing for the Canadians. On the one hand, they have gained design freedom. Case in point: NEPTUNE Canada accepted Alcatel's communications redesign even though the Americans initially rejected it. On the other hand, NEPTUNE Canada must settle for a considerably smaller system than it had hoped to field. Bearing 100 percent of system design costs that the United States was supposed to share leaves a lot less cash to build and equip the system--about Canadian $15 million (US $12.3 million) less, in Phibbs's estimation. Barring a new infusion of cash, the Canadians' 800-km loop will host just 2 or 3 science nodes instead of 8 to 10. "We've paid the money to get in the game, and now we don't have very much left to play the game," Phibbs laments.
Nevertheless, even two nodes could produce spectacular results. In addition to Endeavor Ridge, NEPTUNE Canada will field equipment at Barkley Canyon, which boasts outcroppings of natural gas hydrate the size of small trucks. The outcroppings are the edges of methane-rich strata in the seabed whose stability, or lack thereof, could be one of the factors contributing to the pace of climate change. The hydrates themselves have also long been recognized as a potentially enormous source of energy.
Seismic surveying equipment on the NEPTUNE node should provide the first precise pictures of the underground hydrates, while a tethered robotic crawler assembled at the University of Bremen, in Germany, will monitor the hydrates' response to changing environmental conditions, such as the Northeast Pacific's rapidly warming waters.
"Today things are happening, and you do not know they are happening," says Barnes [see photos, " "]. When NEPTUNE comes online, scientists will be aware of every twitch and tremble in the hydrate field, and they'll have a front-row seat.