We successfully recovered all 38 OBEM instruments 24 hours ago, and the data look great. Below is a first glimpse at a spectrogram from the time series recorded by one of the receivers. Channels 1-2 and 3-4 show the magnetic and electric field data, respectively.
Notice the bright, Christmas tree-like feature on December 19. This is the signal from SUESI flying over the receiver. The horizontal stripes at 0.25 Hz, 0.75 Hz, etc are the fundamental and harmonic frequencies from our source waveform (we transmit a 0.25 Hz waveform).
Elsewhere, you can see a diurnal variation from blue to green at around 0.1 Hz. That signal is being generated by tidal currents, aka the motion of the ocean. After some more processing, we will be able to retrieve magnetotelluric data, a passive source method that relies on interactions between the sun and Earth’s magnetic field.
All in all, things are looking good. Indeed, we have now redeployed 35 of 42 OBEM receivers in a mere 16 hours. In 8 hours time, we will be putting SUESI in the water again to collect our second profile of controlled source data!! Best Christmas present EVER. Let’s just hope the weather plays nice.