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2009 CHIRP CRUISE

March 1-6, 2009
aboard the R/V Manta

As part of a Memorandum of Agreement between Texas A&M University Galveston (TAMUG) and Flower Garden Banks National Marine Sanctuary (FGBNMS), TAMUG is granted a certain amount of shiptime on board the R/V Manta each year. This expedition was run under that agreement.

The purpose of this expedition was to survey the ocean floor at Sabine Bank and an area outside of Galveston. This was the first mission of its kind on board the R/V Manta.

Participants

R/V Manta Crew:

Captain Chuck Curry
Mate Deborah Brock
Deckhand Wes Haizlip
Sean Guss, TAMUG volunteer

Scientific Crew:

Dr. Tim Dellapenna, TAMUG, Principle Investigator
Kyle Johnson, TAMUG Graduate Student, Tech II
Andres Cardeuss, TAMUG Graduate Student, Tech II
Jim Flocks, USGS
Dana Weise, USGS
Jordon Sanford, USGS

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Special Equipment

This expedition made use of two different types of sonar (echo sounding) equipment called CHIRP and SWATH. CHIRP (Compressed High Intensity Radar Pulse) is a type of sonar that is towed a short distance behind the boat, while Swath is a type of side-scan, single-beam sonar operated off the side of the boat.

Preparation

On Thursday and Friday, February 26-27, 2009, large equipment, including the CHIRP and SWATH, arrived at the vessel and was loaded on board. Sunday, March 1, the USGS scientists arrived from St. Petersburg, FL with the remainder of the equipment necessary for the trip. After a full day of fitting, retro-fitting, wiring and computer setup, the R/V Manta was ready for a 12:45 p.m. departure on Monday, March 2.

Sonar Surveys

Four people on the back deck of a boat getting ready to lower equipment into the water using an overhead cable.
Deploying the CHIRP off the back deck of the R/V Manta. Photo: FGBNMS

Once outside the Galveston jetties on March 2, the side-mounted SWATH and the CHIRP survey equipment were deployed. A series of 10 test lines were run to determine that all equipment was working properly. The equipment was then brought back on board for the two and a half hour transit to Sabine Bank.

Upon arrival at location all equipment was re-deployed and by 7:30 p.m. survey operations were underway. Winds began to pick up through the night and by Tuesday morning (March 3) winds were 17 to 20 knots and seas were 3-4 feet, making the 4 knot ride less than enjoyable. However, even with the change in weather conditions the scientific crew continued to receive good data from the equipment.

The side mount holding the GPS antenna and SWATH remained rock steady despite the conditions. A few adjustments to the towing configuration had to be made to reduce stress on the calibrated pulley, but the alternate setup worked well.

By 12 p.m. Wednesday, March 4, the R/V Manta had completed over 200 miles of survey lines on Sabine Bank and equipment was removed from the water for transit to the next survey area off of Galveston. Seas remained at 3-4 feet but turned into a rolling swell for a more comfortable ride.

The remaining 48 hours of the cruise were spent running survey lines across the traffic lanes outside of Galveston.

Anchoring Drill

Before returning to the dock on Friday, March 6, the crew of the R/V Manta and the scientists on board conducted an anchoring drill in preparation for coring operations scheduled for the week of March 23.

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General Observations

Overall the week long CHIRP mission went very well. A total of 580 miles were covered and, as the first trip of this type on the Manta, it was a learning experience.

The 3-4 foot seas were in the upper limits for successful and safe survey operations. Lab space was fully used and computer equipment in the labs was stable.

Computer equipment lined up along a counter in the inside lab of the R/V Manta.
Computer equipment set up in the lab space of the R/V Manta. Everything was stable even in 3-4 foot seas. Photo: FGBNMS

Equipment deployed well off the stern of the vessel and also off the side-scan mount. However, deploying the side-scan was labor intensive and ideas were brought to the table on mechanical aids to assist in that effort. It was also agreed that a Hypaq monitor needs to be permanently mounted on the bridge.

Initial observations of the data indicate that the returns had what was believed to be a slight reflection from the port pontoon of the Manta. This did not corrupt the data, but might be eliminated in future surveys by lowering the SWATH instrumentation a little.

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