_ CRUISE
REPORT _ CRUISE
REPORT
Latitude: 39.5dN - 41.75dN
Longitude: 71.4375dW - 70.0625dW
HERE for a detailed cruise map. John S. Schlee, USGS
John A. Grow, USGS
Thomas Aldrich, USGS
Bill L. Jaworski, USGS
Frank Jennings, USGS
Perry Parks, USGS
Richard Sylwester, USGS
Dennis Edwards, USGS
Michael Kerkmann, USGS
Felicity Oram, USGS
Joseph Burden, Raytheon
Frank Wood, SEI
Jack Mago, Geometrics
Donald Price, Price Compressor Co.
The vessel left Woods Hole at 1645z on 27 September 1975. The gradiometer was deployed off Gay Head at 1915z; followed by the 3.5 kHz system and the minisparker. Interference problems were found between the minisparker and the gradiometer. A signal line going to the gravity hut from the gradiometer was found to be picking up noise from the minisparker. Also, the gradiometer tow cable had some problems. It was a new cable with a special floatation covering. Each of the two sensors on the cable had stabilizing fins, lead weights a few meters forward of each sensor, depth controllers, and a drag chute on the rear sensor. The lead weights seemed to cause the cable to tow too deep and were removed. Following that, the gradiometer performed well with only minor noise from the minisparker. In the future, however, the gradiometer should be run in such a way that it is cycled with the minisparker, i.e., it's polarizing when the minisparker is firing.
The minisparker performed well. The hydrophone array had an intermittent problem which required switching to a different lead-in cable. From that point on, it worked well.
The gravity system worked well. It was found that it is not advisable to cruise at speeds greater than 10 knots because of the excessive vibrations in the gravity hut.
The 3.5 kHz system started out fine but as deeper water was reached, the bottom returns were lost. An attempt was made to use the Edo transceiver which helped for awhile but is also failed in deep water. The Raytheon technician was seasick and not very useful for servicing. The system would be considerably better if a 12 transducer array were mounted in the well.
On 28 September the airgun system was tested. The hydrophone array was deployed with no problems and operated properly. The airguns were towed in two groups. One group of three airguns were towed from a "sled". The fourth airgun was towed separately. Except for minor rigging problems, the single airguns presented no problems. The group of three airguns did present some problems and required using the oceanographic winch, crane and numerous tag lines. This rigging was to be changed before the next cruise. The biggest problem with the airgun system turned out to be the circuit breakers on the air compressor motors. They were too small to handle the load.
Following the airgun system test, it was decided to head back onto the shelf where a test could be run on the gravity system, in a low gravity gradient area, to calibrate the filter coefficients in the gravity data acquisition system.
Following that test, the FAY returned to Woods Hole arriving at 1230z, 29 September 1975. All of the geophysical systems were tested, problems identified, and 440km of usable gravity data were obtained.
