Transmitter transmitting

We completed ocean-bottom electromagnetic (OBEM) receiver deployments 20 hours ago.

An OBEM receiver being deployed from the side deck of R/V Roger Revelle

We dove right in to transmitter ops at 2:30 am this morning. This is no trivial task, so it is no surprise that we had some hiccups during our first of four transmitter deep-tow lines.

The Scripps Undersea Electromagnetic Source Instrument (SUESI) is a horizontal electric dipole transmitter rated to 500 Amps of output current. We typically deep-tow SUESI about 100 meters above the seafloor at 1.5 knots (~2.8 km/h) to collect controlled-source electromagnetic data with our OBEM receivers.

SUESI enjoying the beautiful evening weather before her first dip in New Zealand waters

There is always a learning curve during the first deployment, and this time around was no exception. It took us 3 hours to get SUESI in the water, and at first it seemed all was well.

How many people does it take to deploy a SUESI antenna?

After getting her to about 2000 meters water depth, it quickly became apparent that one of the copper electrode antennas had broken off. We were pushing 1500 Volts to SUESI, yet she only output 100 Amps of current, a clear sign of trouble.

So we pulled her back on to deck and confirmed our suspicions. The copper on the short antenna had snapped off.

Broken copper electrode on the short antenna

We went ahead with replacing the copper tubing and made the necessary adjustments to ensure it would not happen again.

We faired well in the second deployment, and now SUESI is humming along, taking in 1700 Volts and outputting 300 Amps of current with a 305 meter long antenna, which provides us with powerful dipole source moment. She is now flying safely at an altitude of 100 meters.

Second SUESI deployment is a success!! What a relief

After only two hours of sleep in the last 36 hours, it’s time for this chief scientist to get some much needed shuteye. Check back in tomorrow for some more background on marine electromagnetic methods and our science objectives during this voyage.