Dive mission planning generally starts during the pre-cruise planning phase. Specific details for a given dive are finalized the night before a planned dive during a post-dive/pre-dive briefing. These are typically run by the Chief Scientist and held in the Atlantis library with science team and Alvin Group members and the ship’s master in attendance. The meetings are normally open to anyone on the cruise and serve to keep all hands aware of and engaged in the total scope of the cruise objectives. If daily open meetings are not practical, at a minimum it is generally good practice to have at least one meeting prior to commencing diving activities and another meeting at the mid-cruise point that is open to all hands.
Prior to a dive, the Expedition Leader and Chief Scientist agree on the planned equipment loading, basket configuration, and the selection of mission observers. The Chief Scientist will also provide the Expedition Leader and the Master with the coordinates of the proposed dive location(s). Both recipients will verify that this location falls within the approved dive clearance area(s).
Additionally, the selected dive position will be checked by the Surface Controller the morning of the scheduled dive. The Expedition Leader will compile and distribute the required pre- and post-dive check lists, compute the estimated variable ballast neutral buoyancy weight value and verify that all intended science mission equipment conforms to pre-cruise testing criteria. Installation of mission equipment may begin once the previous dive’s post-dive checks are complete and the vehicle main battery charging has been started.
Typical Dive Day
During normal cruise operations, launch of the DSV will take place between 0730 and 0800 hours. If an earlier launch is desired, it must be discussed with the Expedition Leader and approved by the Master. Any changes in the launch time will be posted throughout the ship the previous evening.
At 0600 hours the Alvin Group will report to the hanger and begin pre-dive of all submersible systems. The Pilot will be in the sphere readying the vehicle for the dive day. This process usually takes approximately one hour. Once the pre-dive checks are complete, the Pilot will function check any science gear on the sub, as applicable. At this time a qualified member of the science team should be on hand to operate their equipment and assist the Pilot with the function checks. If any science-supplied equipment needs to be calibrated or otherwise set up for the day’s dive, those procedures would be performed at this time.
Approximately one hour before launch time, the A-Frame Operator will begin system warm-up and checks, the Swimmers are notified to begin suiting up, and the small boat is checked and moved to its launch position. The support ship’s Bridge watch will maneuver the vessel to the dive site and begin positioning for submersible launch.
Approximately 30 minutes prior to launch time and with permission from the Bridge, Alvin is moved out of the hangar and ascent and descent weights are installed. The vehicle then continues out to the launch position under the A-frame. When agreement has been reached by all parties that all systems are go, the submersible and support ship pre-dive check lists are reviewed and signed by the Expedition Leader, Pilot, Surface Controller, R/V Atlantis Master, and Chief Scientist before the dive can commence. This practice is an important part of the Alvin safety assurance process, and the Chief Scientist is urged to review the check sheets carefully. Before signing, she/he should ensure that all sheets have been completed and that she/he has been informed of the reasons for and consequences of all discrepancies.
Note: Each sheet on the pre-dive checklist provides an indication of normal submersible conditions. If the entries are not initialed, the values recorded do not fall within the limits specified, or if equipment needed is not fully operational, the Chief Scientist should request an explanation from the Expedition Leader.
Launch and Diving
Once the vehicle is ready and the check sheets have been reviewed and signed, word is then passed throughout the ship to man the launch stations and load people into the sub.
The Launch Coordinator performs a final radio check with all-stations and the order is given to launch the submersible by the Master or his designee. The Launch Coordinator assumes operational control of the launch. The A-Frame Operator, Swimmers, Pilot, and others involved with the launch take their directions directly from the Launch Coordinator.
The launch proceeds in the following manner:
– The two Swimmers board the submersible and the loading bridge is swung back
– Both the Bridge and Surface Controller verify that the ship is at the correct launch location as provided by the Chief Scientist the night before
– The small boat is positioned astern of the support ship ready to assist the Swimmers
– The A-Frame lifts Alvin off of the deck and into the water
– The Swimmers cast off the main and aft lift lines
– The Launch Coordinator informs the Bridge “sub free of ship” and the Bridge increases the forward speed of the ship.
– The support ship then maneuvers well clear of the submersible (>150 meters)
Once free and clear of the support ship, the Swimmers remain with the sub and the Pilot conducts a series of surface checks. Following the checks, the Pilot directs the Swimmers to return to the small boat, and begins the descent.
Descent and Bottom Approach
During descent the Pilot will monitor the variable ballast (VB) system and make buoyancy changes as required to be at or near neutral buoyancy when reaching the bottom approach depth. Determination of neutral buoyancy is based on the vehicle’s rate of descent and the daily VB weight calculation sheet value.
Unless the objective of the dive is to conduct midwater research, at approximately 500 meters off the bottom the Pilot will begin to initiate startup of any submersible science mission equipment and computer programs.
At 100 meters off the bottom the Pilot will drop the first descent weight and begin to slow the descent. The Surface Controller will inform the Bridge that the sub is on bottom.
Once neutral trim has been obtained, the Pilot, using vertical thrusters, will descend the remaining distance to the sea floor and make a slow, cautious bottom approach. Once the bottom is sighted visually, a 360° sweeping turn may be made to verify the area is clear for landing. Science observers are to act as lookouts from the side windows
The Pilot will then proceed to execute the mission profile as required. This includes mandatory communications checks with the surface every 30 minutes and regular monitoring of all critical systems. The senior observer is usually designated as the Port Observer and is considered to be responsible for handling any science-specific direction.
Bottom Departure and Ascent
Typically, the submersible must be back on the surface at 1700 hrs. The Pilot must therefore anticipate the expected transit time from sea floor to surface and plan accordingly. A dive is typically ended for one of three reasons: 1) the dive day has ended, 2) the weather on the surface is anticipated to worsen, or 3) there is a technical problem with vehicle.
Once the Pilot has decided to terminate the dive, and prior to initiating surfacing procedures, the Surface Controller must be notified. The Pilot must then secure all of the science equipment and samples in the sphere and in the forward basket.
The Surface Controller will then give the submersible permission to surface at which time the Pilot will release the ascent weights and report that “Alvin is off the bottom.”
During ascent the Pilot will carry out the following activities:
– Power down all non-essential loads such as science equipment, propulsion, lights, video recorders, etc.
– Save bottom data files and close non-essential computer programs. As required, relay a science report at the earliest convenient time so that the science party can make preparations for sample handling.
Surface Approach and Recovery
At 200 meters, the Pilot will re-enable any equipment required for recovery. The support ship launches the small boat with the recovery swimmers and directs the boat towards the expected surfacing position. All systems and stations aboard the support ship are manned and ready at this time.
Once the small boat acquires a visual sighting of the submersible, it will proceed to the vehicle. The Swimmers then enter the water and transit to the submersible to establish communications with the Pilot and connect the basket safety lines.
The Master or designated Mate will move Atlantis to the vehicle and begin the recovery procedure. When the submersible is sufficiently under the A-frame, the Swimmers will attach the main lift line and the A-Frame Operator will begin the lift and recovery of the submersible.
When Alvin is back on deck, the Pilot and Observers can exit the submersible. Once all personnel are clear of the area, the submersible is pulled back into the hangar and secured. At this time the Alvin Group will help the science team remove any samples from the sub. The science party should have the appropriate personnel available to manage offloaded samples and/or equipment. At this point it is appropriate to begin reconfiguring the basket for the next dive.
Concurrently, the Alvin group will unload all contents from the sphere, complete the post-dive checks, and begin battery charging.
After dinner, the Pilot-In-Command of the next dive is typically available to complete any basket configuration that is necessary. The science team should have the appropriate personnel available to support that work as necessary.
Following the final dive of the cruise, the Alvin Group will perform a full wash down of the vehicle. All science-supplied gear will be removed and returned to the science team, and vehicle maintenance will commence.
Alvin operations normally occur during daylight hours, typically between the hours of 0800 and 1700. This schedule provides an opportunity to conduct complementary and/or independent nighttime operations with R/V Atlantis including, but not limited to: AUV operations, dredging, coring, net tows, CTD casts, and multibeam mapping. Successful nighttime AUV operations, for example, have used the NDSF vehicle Sentry to map an area of seafloor prior to subsequent diving with Alvin. Important considerations when planning nighttime operations include staffing (both science and ship’s crew) and timing relative to Alvin launch/recovery, as noted below:
- If nighttime operations require specialized personnel (e.g., for AUV operations), those scientists and technicians will normally occupy science berths.
- If ship’s crew are required to assist with nighttime operations (e.g., winch operations, vehicle launch & recovery), plans should be discussed with the ship’s Master during the pre-cruise planning process to ensure appropriate staffing. Onboard SSSG technicians are available to science 24 hours a day.
- Nighttime operations may begin as soon as the Atlantis crew has completed Alvin recovery. Note that this will typically coincide with the dinner hour and a watch change. Please consider the crew’s rest and daily activities when planning the start of nighttime operations and allow sufficient time (i.e., >1 hour buffer) after Alvin recovery.
- In order to maintain the Alvin daylight dive schedule, nighttime operations must conclude with sufficient time to transit to the dive site. Atlantis should be on station at least 30 minutes prior to Alvin launch.
Concurrent Vehicle Operations
Concurrent vehicle operations are operational periods where Alvin and other vehicles are in the water at the same time in the same vicinity. The most likely scenario is when AUV Sentry, one of the NDSF vehicle assets, is on board Atlantis as a component of the scientific research objectives. The Alvin Group has a specific operational plan for joint operations with Sentry.
Other examples of concurrent operations include operations with other AUVs, specialized scientific sampling landers, elevators, surface craft, etc. Alvin routinely operates with elevators in the water. There may be situations, however, where elevators are specialized and concurrent operations require additional planning.
Concurrent operations with other vehicles and/or platforms require a detailed discussion of the operational plans and requirements as a part of the pre-cruise planning process. The Alvin Group will evaluate the desired operations and determine if the requested plan is possible and/or permitted within the guidelines and rules for concurrent vehicle operations. The Group will then work with the science team to develop a specific operational plan.
At present Alvin does not support concurrent operations with tethered ROVs or cabled platforms that are operated on board or in the near vicinity of the support ship. Note that operations with ROVs tethered to Alvin are possible with appropriate advance planning. Additionally, the deployment of cabled platforms, equipment lowered via the ship’s winches, or freely-released elevators is not permitted during the periods Alvin is in the water. Recovery of elevators and vehicles during Alvin operations is permissible with appropriate planning.
Typical elevator platform
Two free-vehicle “elevator” lift platforms are available for remote equipment deployments and recoveries. Each platform deck is 4 ft x 5 ft and there is a vertical structural shaft in the center. A simple weight release arm is located below this shaft. 150 pounds of flotation for each elevator is normally carried aboard Atlantis.
For excessive loads both floatation packages can be combined for a single elevator use. Any additional flotation required is normally supplied by the user. Additionally, because elevators use submersible ballast steel for descent weights, the anticipated number of deployments must be specified to ensure enough steel is available. A science plan involving a large number of elevator deployments may incur added charges for ballast steel.
Precisely-located elevator drops can be accomplished using the Atlantis hydro wire and an acoustic release.
All users intending to use elevators must supply equipment water weights and dimensions well in advance of any cruise.
Pilot-In-Training (PIT) Dives
The Alvin Group is continually working to recruit exceptional team personnel and to train appropriately qualified individuals as Alvin Pilots. PIT dives are a critical component of this process—the means by which a PIT learns hands-on operation of the submersible under the watchful guidance of a certified pilot.
On each scientific cruise “training seats” are assigned on designated dives to provide for new pilot training, pilot refresher or other training requirements. We schedule one PIT evolution every five dives; i.e., a cruise with 10 dives planned will schedule two PIT dives, typically dives #5 and #10.
Personnel on a PIT dive are the PIT, the Pilot-in-Command, and one scientific observer. PIT dive activities and mission objectives should be planned as a normal scientific dive mission.
PIT dive scheduling should be included in pre-cruise planning to address any special requests or concerns. The Chief Scientist and Alvin Expedition Leader will then work out the final schedule for the dive series, including any PIT dives.
No operations over the side of the support ship are permitted during Alvin dives without prior communication and permission from Alvin Operations and the bridge officer. This includes a period of time prior to the start of the dive (pre-dive and launch) until completion of the recovery of the submersible and Atlantis small boat.
Alvin is likely to be relatively close to the support ship at any time during dive operations. Therefore, we restrict over-the-side operations to those activities that will not present a hazard to dive ops and support personnel. Typically, activities that may be approved during dives include small scale collection of surface seawater and/or sampling using lightweight equipment (small nets) or other non-hazardous activities. Larger towed equipment, CTD ops, or other cabled or crane-operated overboarding are not permitted, nor is dumping of large items (trash, solids, rocks, etc.) during dive periods.
Additionally, the Group restricts all biodegradable dumping operations (sample liquid and other biological byproducts) during the launch and recovery periods, including the periods before these operations begin. These restrictions are in place to prevent the attraction of marine predators and to ensure the safety of the Alvin assist swimmers and small boat operators during the launch and recovery periods.
Sample elevators released from the seafloor are routinely permitted during dive operations as long as the recovery times do not conflict with the planned time for Alvin launches and recoveries. Other similar activities (e.g., AUV recoveries) may be permitted with advance planning (pre-cruise) and after full review of the planned activities.