This acronym used to stand for Tracor Acoustic Profiling System. That was when Tracor, Inc. was a publicly held corporation, headquartered in Austin, TX. Our office in San Diego conducted acoustical research, principally for the Navy, including some basic research on the use of multi-frequency acoustics to measure and quantify zooplankton distributions in the ocean. As a part of that research, I designed a series of acoustic sensors that eventually became TAPS. Previous systems evolved from collections of individual transducers on a frame and culminated in a 21-frequency system built (by Van Holliday and Dave Doan) on a surplus mine-hunting sonar towed body. This system drew power from shipboard equipment. The TAPS sensors were a compromise design intended to provide useful data in a portable package running on internal batteries.

Tracor was taken private in the late '80s, went through bankruptcy, and emerged as a public company once again -- only to be purchased by General Electric PLC (of England). Tracor was included in the Marconi Electronics group which, a few years later, was merged with God-knows-what-all from British Aerospace to become BAE SYSTEMS. And we were firmly advised that the BAE portion had absolutely no connection to British Aerospace and was just a name. I suppose that BAE SYSTEMS is still around -- I get my retirement check every month.

The TAPS-6 concept derived from the early MAPS systems but the design began with some 2-frequency systems used on the BITS mooring that I designed and a 4-frequency predecessor that is now in mothballs. It was an interesting challenge: to make a portable, internally-recording gadget that would act like a ctd but could resolve zooplankton size-distributions versus depth. It took a number of iterations to get it pretty close to right.

The first problem was -- what frequencies should we use? This was answered by selecting the target zooplankters: copepods. These animals are reasonably-well-modelled by a truncated fluid sphere model. Van Holliday spent several hours on his computer to select four (later six) frequencies from the 21 MAPS frequencies that seemed to work well estimating size-abundance for these zooplankters. Long after the fact, I spent some time trying to rationalize the selection of frequencies and came up with a way to select the span of frequencies needed for particular copepod sizes. Fortunately, these approaches agreed with each other pretty well.

The second problem involved the sample volumes for this system. The sample volume can be computed from the pulse length, the range, the speed of sound in water, and the beam angle of the transducer used to transmit and receive echoes. We discussed this at length; on the one hand, too small a sample volume would mean sometimes there would be very few scatterers in the sample volume -- making the assumption of volume scattering incorrect. Too large a sample volume would make it more likely that the relatively rare larger scatterers (euphausiids, ctenophores, larval fish, etc.) might contribute to the echo energy. We settled on a sample volume of about a liter using transducers with 8-12° beamwidths and a 336 microsecond transmit pulse, sampling at about 1m range. Note that this vastly simplifies the assumptions we have to make, compared, say, to an echosounder configuration where the sample volumes increase inexorably with range.

The picture above shows the original version of TAPS-6 exploded. The endcap on the right-hand side contains six acoustic transducers, resonant at 265, 420, 700, 1100, 1850, and 3000 kHz. There are six transceiver cards (with the large black capacitors) to drive these transducers. The other endcap contains a depth sensor, temperature sensor, and jacks to connect external sensors such as fluorometers or conductivity sensors. A single-board-computer and interface circuitry control the functions. A 21.6V NiCad battery supplies power for 10-14 hours of operation.

The last TAPS (TAPS-6 NewGen) was a complete re-design utilizing some concepts and designs from a series of 8-frequency systems that were built to operate on moorings. These TAPS-8 units have been used extensively in the Arctic by Jeff Napp at NOAA in Seattle. They are getting quite long in the tooth and probably are nearly ready to be replaced. The NG TAPS is used by Anne Lebourges-Dhaussy at IFREMER in Brest, France.

BAE SYSTEMS no longer makes or supports TAPS -- I made a deal with them when I retired to provide service for existing customers in exchange for the spare parts and some test equipment. If you need service or help with a TAPS, contact me using the email link below. There is little to no chance you could get me to build you one, but I could certainly provide you with drawings, schematics, code, and advice if YOU want to build one. All this information is in the public domain. Eventually, all that information will even be right here on this website. For as long as I am around, anyway …