Obsession.
Although it proved to be a false alarm, the SOFAR float gang received an urgent command from US Navy Headquarters to retrieve a SOFAR float that was erroneously thought to be drifting at shallow submarine depths. You can understand their concern if you click on Instruments and scroll down to The SOFAR float – it is huge! However, knowing today that a submarine can survive a collision with a seamount, I suspect bumping into a SOFAR float might at most lead to a dent in the outer hull; the fate of float is a different matter. I was tasked with locating the float.
I joined the cruise on the RV Oceanus in Miami, Doug Webb was chief scientist. To determine the float’s position, we needed acoustic travel times from the float to preferably three different sites. We had several shore-based stations, one of which was in the Bahamas that I could visit just prior to the cruise. While the signal was barely detectable, I was moderately confident I could see it on the graphic recorder we had in operation. If valid, it meant I knew the distance to the float from that site. Not too long after we cast off from Miami (this is almost 50 years ago so I don’t recall the details), we stopped and lowered a hydrophone to listen for the float – and we heard its transmissions, and thus had a 2nd distance. We would need a third one to be able to triangulate and determine the float’s position.
Very likely I could have used a compass and a ruler on a plotting sheet to determine the float’s position, but being the recent proud owner of a programmable HP-65 calculator I decided to code it to determine the position of the float. It took me a good two days to write and validate the code, which had to be split into two parts to fit onto the tiny magnetic strip cards. Coding the HP-65 was very different, a stack-oriented structure like writing in Forth rather than Fortran. My colleagues onboard were not impressed with my obsession with the calculator, in fact they weren’t shy about showing their irritation. But when the time came I was ready. After we stopped to get a 3rd distance, I plugged in the numbers and got a position, which, as it turned out, was not far off our intended cruise track to Bermuda.
Doug Webb has designed all SOFAR floats to include a short-range acoustic command system so that by transmitting coded signals they would reply with a ‘Here I am’ ping. With another command he could cause the float to drop ballast and bob to the surface for recovery. It was thanks to this capability that Doug saved the SOFAR float program in MODE (see my August 28, 2023 post). When we got to the expected site, we lowered the command pinger to see if the float was in the vicinity. Imagine the rush I got when it replied ‘Here I am’. What a ‘wow’ moment that was - I was so proud that I put us in the right spot! I don’t know if my colleagues forgave my obsession with the calculator, but I think they were impressed that I had pulled this off, a high point in my career! We retrieved the float and continued to Bermuda.