Galápagos Rift Expedition 2011

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3. Galápagos Rift Expedition 2011
4. Background
5. Seirios

Scientists and engineers exploring the deep ocean with a remotely operated vehicle (ROV) are now able to see a lot more of what they are doing and where they are going. NOAA’s innovative and newly designed camera sled Seirios illuminates the ROV from above, giving operators on board the support ship an expanded view of the ROV as well as enhancing visibility in the surrounding areas.

These broader perspectives promise to increase not only our understanding of how to investigate a remotely explored area, but also to literally shed light on a location’s features and inhabitants and to capture high-quality images to share with the world. The camera sled Seirios and the ROV, the Institute for Exploration’s (IFE) Little Herc, both carry the most advanced underwater high definition (HD) video cameras available today. Paired with the system’s 3,200-watt HMI lighting technology, these cameras capture the true colors experienced at depth.

The first explorers to benefit from Seirios are participants in the Galápagos Rift Expedition 2011 (GALREX 2011). During the Leg 1 of this Ocean Explorer mission, the exploration team aboard the NOAA ship Okeanos Explorer mapped the Galápagos Rift, searching for areas of active hydrothermal venting. Now on Leg 2, a team of scientists and engineers returns to investigate key locations up close with cutting-edge exploration technology: a tethered, two-body system that couples Seirios with Little Herc, a veteran ROV completely rebuilt from scratch. GALREX 2011 marks the maiden voyage for this combined exploration package.

Various images from the Seirios Camera Sled and sensor platform.

NOAA Develops the New System

NOAA’s Office of Ocean Exploration and Research (OER) developed Seirios. A major re-design and overhaul of the camera platform originally owned by OER, Seirios combines significant modifications, new design and fabrication, and engineering upgrades to existing components, with an impressive array of underwater cameras and sensors. Seirios is designed to operate as a stand-alone towed vehicle or in tandem as the second body with a free swimming remotely operated vehicle, such as Little Herc. When operated in tandem with Little Herc, Seirios also acts as a depressor, which decouples Little Herc from the ship’s heave (up and down movement). In its dual role, Seirios could be towed alone in relatively close proximity to the seafloor or attached to the ROV where it “flies” several meters above it.

Seirios improves on the previous equipment in the following ways:

1. it is able to carry more cameras, sensors, and lighting to increase the types, amount, and quality of imagery and data collected during explorations;
2. it better illuminates the ROV from above, providing unprecedented ROV visibility as well as significant improvement in the ROV pilot’s overall perspective of the surrounding seafloor;
3. it carries two HD video cameras that increase the effective viewing area to almost 360 degrees, giving explorers a better sense of place during exploration.

Given these factors, the GALREX 2011 team expects to collect stunning imagery during this leg of the cruise. It should be better than anything to date.

The Seirios Solution

In either configuration (stand alone or in tandem), Seirios brings significant tools to deep-sea exploration and offers solutions to problems researchers using the old camera platform encountered at sea. To start with, scientists and engineers needed Seirios to be much more versatile. The original camera platform was not designed to be towed, and its shape and configuration did not allow for proper camera-to-light separation.

To address this, the NOAA OERdesign and engineering team, in collaboration with IFE, gave Seirios an entirely new shape, designing and building its stainless-steelframe as a towable body. The original camera sled was conical. At its base, it measured about 6 feet in diameter; at its top, it was just over 3 feet. The overall height was just under 7 feet, and the entire unit weighed about 2,200 lbs. The new shape — long and rectangular — increases Seirios’ capability to perform beyond the boundaries of the original role as strictly a depressor for the ROV. At 12 ft long, 3 ft wide, and just under 5 ft high, the Seirios frame tows much better than the original frame did through the water column. Under the right conditions, towing Seirios allows for very efficient use of time during exploration.

Seirios also features a larger area for packaging important equipment. Almost one-third of this new frame is open space, which increases the distance cameras can be separated from lighting. This reduces optical backscatter (light reflecting off particles or plankton) and allows for much higher quality imaging.

Seirios can be enhanced even further. Future advances in lighting and camera technology promise to allow far greater illuminating and optical capacity at power requirements similar to those we operate with now. New sensors or advanced technologies that measure water properties (chemistry, temperature, turbidity) and map features (laser and side scan and multibeam sonar) can be added to help scientists better understand the water column and the geological features being explored.

ROV Little Herc

In the deep dark world of ocean exploration, Seirios is exciting — even glamorous — with its lights and myriad abilities to expand the types of imaging and data sensors it can carry. Used in tandem, the ROV Little Herc, however, gets us down to the very important details. Little Herc is a simple ROV capable of working at depths of 4,000 m (13,123 ft). At about 6 ft long, 4 ft high, and 3 ½ ft wide, it weighs in at about 1,000 lbs and carries 800 watts of lighting. Nimble and compact, Little Herc was not designed to compete with its bigger ROV brothers but to take stunning close-up images in close proximity to the seafloor. It has no manipulator arms or other tools typical on ROVs, because its sole mission is to explore and characterize the seafloor using sensors that beam data back via our satellite system. Little Herc’s thrusters enable the operator, who controls the vehicle from a system on board the ship, to move it in all directions. Up and down, side to side, and a rotational pirouette: the ROV moves with the fluidity of a helicopter.

Power and Control

Seirios is powered and controlled from the NOAA support ship Okeanos Explorer. Essentially, Seirios is tethered to the Okeanos, and it receives power that has been transmitted from the ship over 8,000 meters (26,246 feet) of 17-milimeter (2/3-inch) diameter electro-optical-mechanical cable. This custom-made cable assembly is the “heart” of our system, and the mechanical loads imposed on it at sea require its breaking strength exceed 40,000 lbs. The cable is stored on a traction winch, which is mounted below decks on board the ship.

The ship’s generators provide about 450 VAC 3-phase power to a ship-mounted power distribution unit (PDU). Electrical engineers designed the PDU to take that 450 VAC 3-phase power, boost it to about 2,800 VAC, and send it down the 8,000 m of cable. When the power reaches the camera-sled, it is reduced back down to 480 VAC, and then further distributed to Little Herc via a 40 m (120 ft) soft tether that connects the two vehicles together.

Also contained in this 8,000-m cable are 3 optical fibers — each smaller in diameter than a strand of human hair. All vehicle control and data and video transmission is done over these fibers.

Speed at Depth

It’s a common question: how fast can the vehicles travel? Indeed,speed is often looked at with respect to efficiency, but high speeds are not always desirable in the work that we perform. For instance, if we pushed the control to full forward speed on Little Herc, the ROV might reach 2 knots; but details in the images it would capture from the seafloor would be a blur. The same holds true for Seirios. We can tow the vehicle at 2 to 3 knots as a stand-alone system, but if we were doing anything other than very broad reconnaissance, the images would not be very valuable.

Seirios and Little Herc are designed to go as deep as 4,000 m (13,123 ft). Future modifications to Seirios will soon push that limit to 6,000 m (19,685 ft).

Operation: A Team Effort

Working in the ROV control room onboard the Okeanos, four people — a navigator, ROV pilot, ROV co-pilot, and video engineer — are directly responsible for operating Seirios and Little Herc.

The navigator keeps track of both vehicles’ positions in relation to each other on the bottom as well as in relation to the real world. This person also must know where their positions are in relation to the ship. The navigator communicates with the ROV pilots and the ship’s bridge, choreographing the “dance” among all parties and their respective equipment.

The ROV pilot “flies” Little Herc, and the ROV co-pilot “flies” Seirios. Together, the pilot and co-pilot keep the vehicles in proper relative position so Seirios is at no time “tugging” on Little Herc.

Completing the team, the video engineer controls the HD video cameras and is responsible for all aspects of the image quality, related to both cameras and lenses. This person must follow the pilots’ lead, ensuring the subject matter being videoed (or captured) is always in focus and has sufficient lighting.

Equipment

Seirios carries two HD video cameras, and 2,400 watts of very high intensity lighting called hydrargyrum medium-arc iodide (HMI) lighting. The most significant advantage of HMI lighting is the color temperature. At 5,600 Kelvin, the lights produce illumination equivalent to sunlight, which is essential to reproducing the true colors of objects and marine life underwater. Choosing from three types of reflectors, we can determine the beam pattern of each light. (Water clarity, however, is always the determining factor for light penetration.) The amount of light on Seirios has been substantially increased by both the number of lights as well as our ability to concentrate all the lights in one common direction. The original camera sled carried only 1,600 watts of lighting and we could never concentrate more than 800 watts in any one direction.

Seirios also carries two, 5-horsepower electric thrusters that allow it to move both rotationally and laterally. Depth sensors, an altimeter, ultra-short baseline (USBL) acoustic tracking, sector scan imaging sonar, a conductivity-temperature-depth (CTD) sensor and several other “task” cameras are all standard equipment. With the upgrade to a towable and thruster-actuated camera sled system, the introduction of a compass and full color scanning sonar gives us directional reference as well as obstacle avoidance and the ability to see beyond the range of our cameras and lighting. This is particularly helpful when we explore the surrounding terrain.

Seirios Operating Configurations

There are two operational modes for Seirios: two-body (coupled with an ROV) or towed alone. In both modes, Seirios is suspended from the ship by an electro-optical mechanical cable, which is hydraulically reeled in and out to raise and lower Seirios to and from the seafloor. In the two-body mode, Seirios is not only tethered to the surface by the electro-optical mechanical cable but is also attached to the ROV by a 40-m (120-ft) electro-optical soft cable. The surface cable attaches to the top of the Seirios; and the soft cable (connecting Seirios to the ROV) attaches to the aft end of the vehicle.

In the two-body configuration, Seirios operates about 10 m (32 ft) above the seafloor. The ROV works directly below it, moving around much like a dog on a leash. In this mode, Seirios also acts as a depressor, decoupling movement and minimizing the degree of heave that reaches Little Herc.

The Brightest Star

Aptly named for the brightest star in the night sky, Seirios also takes on the role of the undersea “sun.” With 2,400 watts of lighting and its normal proximity flying above the ROV, Seirios adds significant illumination to the surrounding work area we are exploring. This enables explorers at the ROV controls (back on the Okeanos and at Exploration Command Centers)to see the environment surrounding most of the ROV, as opposed to the narrow area visible with only the ROV’s lights. Suddenly, the ROV has context in the seafloor and water surrounding the vehicle. For example, a curious shark swimming toward the back of the ROV to investigate the vehicle will be visible to the explorers. In years past, this was not the case. Who knows what might have been missed, lurking in the dark, just outside of view.

Impressive Images and Valuable Perspectives

The end result of the decoupling action and site illumination in a two-body configuration is the ability for both vehicles to collect very impressive images during exploration. The main HD camera on Seirios is located on the front and mounted on a controllable tilt mechanism. By tilting this camera and also rotating the camera sled with its thrusters, Seirios can easily follow all of the movements of the ROV. This not only keeps the 2,400 watts of light focused on the ROV work area but also allows us to get beautiful images of the ROV as it works on the seafloor.

The additional bonus is the perspective this view affords the ROV pilot. Things the pilot could not see easily before are often revealed in Seirios’ forward-looking HD camera. A second HD camera is positioned in the center of the camera sled’s stainless-steel frame and mounted on a pan/tilt mechanism. The entire assembly (both camera and pan/tilt) is also attached to a pressure-actuated hydraulically driven bracket that telescopes up and down with the ascent and descent of the camera sled.

When Seirios is on the deck of the ship, this assembly is tucked up into the frame. When the vehicle is launched and begins its descent, the increasing water pressure moves this assembly downward below the frame, where the camera can rotate almost 360 degrees. This allows the co-pilot, who controls the operation of Seirios, to have a constant view of what is around the camera sled when it is working near the seafloor. In areas of very steep topography, this view is extremely important, because it affords both obstacle avoidance and situational awareness. This can mean the difference between operating the equipment safely or fouling it on the bottom, and either damaging or losing it entirely.

Secondary Mode of Operation: Seirios Towed Alone

Without an ROV attached to it, Seirios can be towed at speeds faster than what is typically practical in the two-body configuration (about 2 knots). The towed-alone configuration allows for a more efficient reconnaissance when the goal is to cover greater distances in situations where a general observation process is acceptable. The main drawback to this mode, however, is the operational sea state. In the towed alone mode, Seirios is the only visualization tool; the inability to decouple the heave of the ship most often means the images must be gathered from greater distances off the seafloor. Dragging Seirios along the bottom — or even just having it hit the bottom — is never an acceptable mode of operation. The new camera sled is far to valuable to science to put it at risk.

Deployment and Recovery

One of the trickiest parts of our at-sea operation is the launch and recovery of the two vehicles when operating them in tandem. Rough sea-states and heavy currents are normally the two major factors that affect this process. During the launch, Little Herc is the first vehicle to be put in the water. It is lifted over the port side of the aft quarter of the ship’s fantail by our ROV lift crane and released from the lift hook after all critical control systems are checked. Directed by the ROV dive supervisor, the ship’s deck crew operates the crane. The ROV pilot who is stationed inside the ROV control room is controlling the ROV.

While this process is unfolding, the ship is either being held in position with the ship’s thrusters, or it is being moved slowly forward maintaining a very slight headway. Seirios, at this time, is still strapped down on the centerline of the fantail underneath the lifting A-frame. As soon as Little Herc is in the water, it is driven directly aft of the ship until it reaches the end of its tether. At this point, Little Herc is being towed very slowly backwards. This puts a significant tension on the tether that connects Little Herc to Seirios. Next, Seirios is lifted off the deck by the ROV traction winch, using the main electro-optical-mechanical cable that runs through the sheave on the top of the aft A-frame. Once Seirios is raised off the deck, the A-frame is boomed outward toward the stern of the ship until Seirios is completely suspended over the water. The winch operator, who is stationed one deck above the aft deck, where he maintains a birds-eye view of the activity, then lowers it into the water.

Once Seirios is in the water, the two vehicles begin their descent. As they descend, the vehicles stay streamed out aft of the ship, maintaining a 40 m separation between each of the vehicles so they never accidentally come in contact with each other. The descent rate is about 15 to 25 m/minute. Upon reaching 50 m depth, the vehicles are stopped and checked prior to continuing on to the seafloor.

The vehicles are recovered much the same way, only the process is now reversed. The vehicles are brought up from the seafloor until they reach 50 m depth. They are held there until all personnel required for the recovery are in their proper places. When everyone is ready, Seirios is brought to the surface using the traction winch, while Little Herc ascends at the same rate using its vertical thrusters. Again, while this is occurring, the ship is either holding position or moving slightly forward into the wind and/or current.
When both vehicles arrive at the surface, Little Herc must be streaming well aft of the ship. This is done to make sure the vehicle stays well clear of the ship’s propellers. When this configuration is secure, Seirios is the first to be brought up on deck. As is it lifted from the water up to deck level, the A-frame is boomed inward until Seirios is completely over the deck of the fantail. It is then lowered onto to the deck and immediately secured with cargo straps.

A lift line attached to Little Herc (which was/is temporarily married to the 40 m tether that separates Seirios from Little Herc) is now stripped away and attached to a small pulling winch mounted on the ROV lift crane. The winch is engaged, pulling Little Herc slowly backwards toward the ship until it is close enough to be lifted out of the water by the lift crane. Once this is done, Little Herc is swung over the side and returned to its dolly on the fantail. This completes the process of recovery.