April 24, 2001
N.B. Palmer

Hello Jose et al.,

We are now off in earnest having completed our BIOMAPER-II testing and dropped off the pilot.
We are just now at -52 21.214°S; -69 12.753°W. Seas are pretty calm now, but this is not likely to last.

The testing went well and we determined that the SeaBeam did not interfere with the HIT acoustics.
So it looks like we will be using SeaBeam along the survey trackline. But we do have a lot of noise
from the ship's the engines and propellors on the 43 kHz which we were able to reduce some by altering
the propellor pitch and which propellor was doing the propulsion. There was also a substantial increase
in noise on the 43 and 120 kHz frequencies from the operation of the stern side thrusters. The latter, however,
will not be significant except for things like when the CTD is in. Still on the 43 kHz, we have 20 dB noise
on that frequency above what we had with BIOMAPER-II in the water at the dock. We also saw the same
kind of noise on the 120 kHz that was observed on the Gould during our first sets of noise measurements in
the straits (but not at the dock). Then, for no reason we could determine, it went away and we did not see it
again. We found no effect from the ship's Furuno and speed log (both located on the bridge), or the
Bathy 3.5 kHz sounder. Sam made up new threshold files based on these noise tests and we did a finally run
with those files before the pilot boat arrived. So noise or not we are ready to start the survey once we get there.

So much for now. I hope your sailing is better than at the start.

Cheers, Peter