Multibeam echosounder

A multibeam echosounder (MBES) is a type of sonar that is used to map the seabed. It emits acoustic waves in a fan shape beneath its transceiver. The time it takes for the sound waves to reflect off the seabed and return to the receiver is used to calculate the water depth. Unlike other sonars and echo sounders, MBES uses beamforming to extract directional information from the returning soundwaves, producing a swathe of depth soundings from a single ping.

Multibeam sonar sounding systems, also known as swathe (British English) or swath (American English) ^{[citation needed]}, originated for military applications. The concept originated in a radar system that was intended for the Lockheed U-2 high altitude reconnaissance aircraft, but the project was derailed when the aircraft flown by Gary Powers was brought down by a Soviet missile in May 1960. A proposal for using the "Mills Cross" beamforming technique adapted for use with bottom mapping sonar was made to the US Navy. Data from each ping of the sonar would be automatically processed, making corrections for ship motion and transducer depth sound velocity and refraction effects, but at the time there was insufficient digital data storage capacity, so the data would be converted into a depth contour strip map and stored on continuous film. The Sonar Array Sounding System (SASS) was developed in the early 1960s by the US Navy, in conjunction with General Instrument to map large swathes of the ocean floor to assist the underwater navigation of its submarine force. SASS was tested aboard the USS Compass Island (AG-153). The final array system, composed of sixty-one one degree beams with a swathe width of approximately 1.15 times water depth, was then installed on the USNS Bowditch (T-AGS-21), USNS Dutton (T-AGS-22) and USNS Michelson (T-AGS-23).

At the same time, a Narrow Beam Echo Sounder (NBES) using 16 narrow beams was also developed by Harris ASW and installed on the Survey Ships Surveyor, Discoverer and Researcher. This technology would eventually become Sea Beam Only the vertical centre beam data was recorded during surveying operations.

Starting in the 1970s, companies such as General Instrument (now SeaBeam Instruments, part of L3 Klein) in the United States, Krupp Atlas (now Atlas Hydrographic) and Elac Nautik (now part of the Wärtsilä Corporation) in Germany, Simrad (now Kongsberg Discovery) in Norway and RESON now Teledyne RESON A/S in Denmark developed systems that could be mounted to the hull of large ships, as well as on small boats (as technology improved, multibeam echosounders became more compact and lighter, and operating frequencies increased).^{[citation needed]}

The first commercial multibeam is now known as the SeaBeam Classic and was put in service in May 1977 on the Australian survey vessel HMAS Cook. This system produced up to 16 beams across a 45-degree arc. The (retronym) term "SeaBeam Classic" was coined after the manufacturer developed newer systems such as the SeaBeam 2000 and the SeaBeam 2112 in the late 1980s.

The second SeaBeam Classic installation was on the French Research Vessel Jean Charcot. The SB Classic arrays on the Charcot were damaged in a grounding and the SeaBeam was replaced with an EM120 in 1991. Although it seems that the original SeaBeam Classic installation was not used much, the others were widely used, and subsequent installations were made on many vessels.^{[citation needed]}

SeaBeam Classic systems were subsequently installed on the US academic research vessels USNS Thomas Washington (T-AGOR-10) (Scripps Institution of Oceanography, University of California), the USNS Robert D. Conrad (Lamont–Doherty Earth Observatory of Columbia University) and the RV Atlantis II (Woods Hole Oceanographic Institution).

In 1989, Atlas Electronics (Bremen, Germany) installed a second-generation deep-sea multibeam called Hydrosweep DS on the German research vessel Meteor. The Hydrosweep DS (HS-DS) produced up to 59 beams across a 90-degree swath, which was a vast improvement and was inherently ice-strengthened. Early HS-DS systems were installed on the RV Meteor (1986) (Germany), the RV Polarstern (Germany), the RV Maurice Ewing (US) and the ORV Sagar Kanya (India) in 1989 and 1990 and subsequently on a number of other vessels including the RV Thomas G. Thompson (US) and RV Hakurei Maru (Japan).^{[citation needed]}