On-site at last ...
Expedition scientists should begin standing watches today following the R.V. Atlantis' arrival over their study area where the Atlantis Transform and Mid-Atlantic Ridge intersect.
Play our game to learn the terms for the sides of a ship. Clue: Port has four letters and so does left. FYI: The term aft also refers to the stern. Flash animation by Wesley Bellanca, Earthguide team 2000.
Transponders
The first task for researchers and crew is deploying 12 "transponders," which are sound wave emitting (sonar) navigational beacons. The transponders are being lowered from the ship's rear (stern) and then pulled by their attached weights to the bottom, where they'll remain until our study's conclusion. Packaged inside yellow and orange colored covers that look like bolted-together oversized hard hats, the transponders are being dropped along the area where our high-tech tools will do their work.
Each transponder constantly sends and receives sonar pulses from the others. They simultaneously communicate with separate navigational sonar beacons attached to the ship's hull as well as to the three separate submersible vehicles - DSL-120, Argo II, and Alvin - that will be sent to study the underwater mountain.
This elaborate cross communications - each beacon asking the others "Are you there?" - is supposed to provide scientists pinpoint accuracy on each device's position. When researchers know that, they will also know the location of geological structures the devices are detecting.
Fig. 1. Deploying the transponders. Photo by Monte Basgall.
The transponders are enclosed in glass floats that will return them to the surface at the study's conclusion for collection and reuse when a special sonar signal severs them from their anchor weights.
After the transponder network is in place, the next task is to launch DSL-120, a side-scan sonar that will broadcast sound waves from both its sides - somewhat like a lighthouse beacon does - to get rough geological assessments along its path.
See how sonar works in our flash diagram. EG Movies: Flash animation by Aren Hansen, Earthguide team 1999.
Submersibles on-board the R/V Atlantis
On this cruise, the Atlantis is home to three of WHOI's undersea investigation tools: Alvin, Argo II and DSL-120. Only Alvin is permanently housed on the Atlantis; the other two can be transferred between ships to meet the needs of other scientific expeditions. While Alvin waits in its tall aft hanger, and Argo II and DSL-120 still rest on the deck nearby, they will all soon spring into action as this expedition reaches its peak. Join us next Tuesday to see them at work.
