Starboard side profile of USNS Michelson from the original drawings.
Not pictured are the #5 and #6 lifeboats, on each side just aft of the #4 hold.
The kingposts just forward of the superstructure were removed.
Only #4 hold retained its cargo handling gear.
The OC Hoist was installed later at the stern.

50 Years of Multibeam Sonar

First conceptual diagram of slant range and sonar observed area in BOMAS (Bottom Mapping Sonar) proposal to the US Navy from General Instruments, the system developer.

An article in Hydro International magazine tells the story of how multibeam sonar was developed in the early 1960s. Originally conceived as an airborne radar mapping system, the concept of beam formed imaging was proposed to the US Navy, which immediately understood its application for use in hydrographic surveys.

Diagram from General Instruments proposal to the US Navy.
BOMAS (Bottom Mapping Sonar), later called SASS (Sonar Array Sounding System), was first installed in 1963 aboard USS Compass Island, a Navy electronic system test vessel. SASS, developed by the contractor General Instruments, was intended to produce contour maps of the ocean bottom. Sixty-one beams, each one degree wide, fanned out beneath the ship. Gyro information was used to stabilize the return echoes for roll and pitch.

Contrary to reports elsewhere on the web, the first SASS survey ship deployment was on  USNS Michelson at the Brooklyn Navy Yard (NY Naval Shipyard) in early 1964. Michelson was to proceed directly to its new operating area in the Pacific, but as the SASS (and associated systems) required further testing. Operating out of ports in Florida, sea trials were conducted in the waters around the Bahamas during spring and summer of 1964. Michelson finally deployed to the Pacific in the autumn, via Panama. SASS was  subsequently installed aboard sister survey ships USNS Dutton and USNS Bowditch.

Usefulness of SASS was initially limited by the lack of  large scale digital data storage at that time. Increased computer power, digital signal processing and the use of GPS for control have improved multibeam sonar. Michelson's SASS was the grandfather of all survey systems, side scans and fish finders in use today.

Read the story in Hydro International here.

Sonar Bathymetry

Mapping the ocean bottom requires continuous measurement of depth using sonic means and accurate recording of the data, referenced to time and geographic position. From when Michelson was put into service through c. 1964 a single beam sonar was used to acquire depth information. This "trackline" method involves steaming along preset North/South and East/West lines in a checkerboard pattern to cover the area to be surveyed. Accumulated data is later plotted to create maps (charts) of the underwater topography.

The sonar transmitter/receiver, was located in the survey control center. Michelson was equipped with the SQN-6 (XN-1) sonar, essentially a modified UQN-1B depth finder set. Nearly every naval vessel of that time had a UQN-1B on the bridge. This was the successor to the "lead line" used to measure depth in the days of sailing ships.

UQN-1 Sonar Depth Finder with cover off (left) and closed.
According to the UQN-1B tech manual the sonar transmitter delivered 800 watt pulses at an audio frequency of 12 khz. Somehow I remember that our sonar, for whatever reason, pulsed ("pinged') a bit higher at approximately 14 khz, controlled by a pair of quartz crystals. The indicator scope and recording mechanism in the SQN-6 cabinet was not used. The unit's transmitter ping was keyed by a separate precision depth recorder (PDR) which also took the SQN's receiver output to be recorded. Two large glass tetrode tubes furnished the powerful audio frequency output. These 4-65A tubes were commonly used in radio transmitters of that time. 

Few people could hear the 14 khz sonar pings, at about the human ear's high frequency hearing limit. Most of the time I could hear it below decks in the living areas, barely audible if listening carefully, a ping every 1 1/2 seconds. American TV sets had horizontal sweep oscillators running at 15.750 khz. I could hear that sound from TVs when I was younger!

4-65A Tetrode
The second sonar element was the transducer. This was the thing that transmitted the pings down into the water and received the resultant echoes. An off-the-shelf UQN-1B came with a transducer made for simple depth finding use. Ours was stabilized such that the transducer always pointed straight down, in line with the local vertical. This electro mechanical apparatus was located down a vertical trunk below the fourth deck, two levels beneath our living area. It probably had some sort of gyro reference to help keep it stable.

Electrically, the transducer was magnetostrictive. Electrical pulses (pings) applied to it changed its shape, converting the transmitter's pulses to acoustic mechanical energy in a narrow beam.

Looking at the stabilized transducer could make you seasick. It stood straight up while the ship rolled and pitched around it. The whole affair worked quite well, keeping the sonar beam more or less straight down unless we experienced really heavy seas. 

Our two precision depth recorders (PDR) were in survey control. Mechanical monsters, each about the size of a washing machine, initiated the transmitter's pings and recorded the results. These worked in a similar manner to plotters but with an electrified stylus instead of ink and printhead. The sonar guy spent a lot of time fiddling with these intensive care machines. A company called Timesfax made them, which identifies the origin of the technology. Fax (facsimile) was invented to transmit low resolution newspaper quality photos over phone and radio circuits.

A wide (26-28") roll of electrosensitive paper was loaded into the PDR's left side. The paper ran horizontally across the top to the take up roller on the right side. A track for the styluses ran from front to back on the machine's left. When turned on, a stylus would start its trip across the width of the paper.

The first point to be marked was the start line corresponding to sea level. After moving a very short distance the stylus encountered the keying block. Here contacts closed very briefly, initiating the transmitter's output (ping). The stylus would then record a short black mark where the sonar heard its own outbound ping. The stylus continued to travel across the paper. If the sonar receiver heard a return echo it would cause the stylus to mark the paper accordingly. One trip across the paper's 24 inch wide track took 1 1/2 seconds and represented a scale of 0 to 600 fathoms. One fathom equals six feet.

Timesfax Precision Depth Recorder (PDR) Operation. Click for larger image.

As the first stylus reached the 600 fathom mark (exactly 24 inches from the start line) another stylus started its trip across the paper, marking the start, keying the transmitter and recording return echoes. Another stylus appeared every 1 1/2 seconds, the equivalent of 600 fathoms of depth. The PDR also recorded some sort of time codes as well as manually inserted event marks. Trace intensity was adjustable.

Another type of PDR, this one from EDO Corporation.
All this actually worked well if everything was adjusted correctly. Before each trip our sonar guy had to check with the first mate or the bosun to get the ship's draft in order to set the keying block to correspond with how deep we were in the water. Precise stuff, indeed.

So what happens if the depth is greater than 600 fathoms? I knew somebody would ask that. Well, if the depth below the keel were say, 1000 fathoms, then the echo return would appear on the next pass across the paper, making that the 600-1200 fathom range. Periodically the oceanographer was required to make a phase check. He could disable the normal pinging, initiate a single ping manually from the next stylus pass, then listen with headphones for the return echo, noting on the PDR paper in which pass (or phase) the return was heard. Simple, huh?

Again, all of this electro mechanical stuff sounds hopelessly complex but it was the best we had and best there was at the time!

An example of a PDR bottom profile trace. Paper moved through this PDR from left to right, giving a continuous profile of the ocean bottom.

The Michelson Mission

Ocean surveys on Michelson involved obtaining continuous depth, time and geographic position information while at sea in the ship's operating areas. Every effort was made to insure measurement precision within the limits of mid 1960s technology. All of this was used to create paper maps, known nautically as charts, of the ocean bottom. These showed an amazing variety of hills, ridges, sea mounts and undersea canyons. In some areas the bottom was very flat.

Nautical chart of the Norwegian Sea from the British Hydro Office.
Another chart of this area can be seen at at greater detail here.

Charts were created right on board the ship by civilian cartographers working for the Navy Oceanographic Office (NAVOCEANO). Data on the earth's gravity and magnetic field were also collected. Occasionally we stopped at various mid ocean locations to obtain water temperature and salinity information as well as bottom core samples.

Michelson's operating areas during my tenure aboard included the North Atlantic ocean (in winter!), above and below the arctic circle. Later we surveyed in the Mediterranean for a few summertime months. During sea trials of new equipment, Michelson spent an extended amount of time around the Bahamas working out of ports in Florida. At the time I left the ship, we were conducting surveys in the Western Pacific.

Michelson was operated by the Military Sea Transportation Service (MSTS), the transport and special missions arm of the navy. MSTS ships were manned by civilian merchant marine officers and crewmen. MSTS is now (since 1970) known as Military Sealift Command (MSC). 

Besides the actual crew and NAVOCEANO civilians, a small (20-25) US Navy detachment was aboard to maintain the survey electronics and provide logistical support .

Michelson's Operating Crew

Michelson’s operating crewmen were civilian merchant mariners, employed by the Military Sea Transportation Service (MSTS), now called Military Sealift Command. The crew was quite large compared with those on ships today. Generally there were three groups of seamen: the deck crew, the engineers and the stewards.
Perhaps this is the elusive
W. T. Hatch (?)
Besides the captain, officially “the master”, deck officers included a first officer (chief mate), a second mate and two third mates, or one third and a fourth mate.  On most merchant ships the first mate is in charge of the deck, cargo, fuel and ballast. The second mate is the ship’s navigator. Aboard Michelson one of the third officers was in charge of safety and lifeboats. The second and two third mates stood watches on the bridge, four hours on and eight off. Traditionally, the second officer takes the four to eight o’clock watches, as during these hours ships usually enter  port.  The first mate was a day worker.

The deck department included both able seamen (AB) and ordinary seamen (OS). An AB stood watch on the bridge (or pilothouse) and steered the ship, acting as quartermaster, directed by the watch officer. Another AB and an OS were also assigned to each watch as lookouts or relief quartermasters. The bosun was in charge of another group of seamen who during the day maintained the decks and hull, scraping, priming and painting. Off watch seamen earned overtime pay doing this as well. One of the ABs also functioned as carpenter.

There were a variety of people in the engineering department. Under the chief engineer and first assistant engineer were three watch standing officers in the engine room, along with the oilers and firemen/water tenders. Day workers included wipers, a refrigeration engineer, machinist,  plumber, chief electrician and second electrician. Steamships required a lot of labor in the engine room.

The chief steward ran the ship’s housekeeping department. On a cruise ship this would be called the hotel staff. The cooks, one of whom was also a baker, messmen, mess assistants, laundryman and utilitymen reported to him. Utilitymen made the beds and cleaned cabins and passageways.

Other crew members included the radio officer, one or more yeomen who acted as department clerks, a purser and perhaps an assistant purser. Altogether, there were about 55 in Michelson's operating crew. The above information was more or less correct as of 1962-64.  I understand that in later years some job positions were combined or made redundant.

Michelson's Navy Detachment

About 20 to 25 US Navy sailors comprised Oceanographic Detachment Three (OCDET3). The group’s commanding officer (CO) was a lieutenant commander. Reporting to him was the executive officer (XO), a junior officer. Both were from the navy reserve. A third officer, usually an ensign, served as electronics maintenance officer (EMO). Eligible enlisted men with good technical skills were sometimes commissioned as electronics officers. Officers promoted from enlisted ranks are called "mustangs". I don’t know why such a small group of navy men required three officers to run it. Perhaps some matters required multiple signatures.

Most enlisted men were technical types, electronics technicians (ET), interior comm electricians (IC) and sonarmen (SO). They were aboard to maintain the electronics that supported the survey mission. A yeoman (YN), hospital corpsman (HM), photographer (PH), a storekeeper (SK) and one or two quartermasters (QM) filled out the navy crew. All had recently completed training for the mission or had years of experience in their fields. Most were first, second or third class petty officers along with one or two chief petty officers.

Navy men aboard Michelson were treated as passengers, having nothing to do with operating the ship. That was the job of the Military Sea Transportation Service (MSTS) merchant mariners. 

Oceanographers and Tech Reps

Civilian oceanographers from the Navy’s Oceanographic Office (NAVOCEANO) in Washington conducted surveys and collected the geographic data and sonar soundings, creating ocean bottom contour maps, called charts. Navy guys usually referred to NAVOCEANO people as cartographers. 

While underway and in the ship's operating area one cartographer was always on duty in the survey control center. While surveying the duty cartographer had "the conn", giving the mate in the pilot house (bridge) directions as to course and speed. His NAVOCEANO comrades worked below in a room called hydroplot, later oceanoplot, charting the accumulated data.

Continuous readings of the earth's magnetic field and gravity were collected. One person tended to the gravity meter more or less full time. Occasionally another took ocean salinity and temperature measurements. The 10 or 12 in the NAVOCEANO staff reported to the senior scientist, alternately known as the senior civilian or survey party chief.

In 1962 and 1963 two field engineers from the Sperry Gyroscope Corp. were aboard, one to offer technical help with the navigational computer, called NAVDAC, while the other supported the radio navaid (Loran C) that supplied control for the surveys. At that time Sperry was sort of the overall systems manager for our mission's electronics.

Perhaps a NAVOCEANO survey party ashore searching for a watering hole?

Reporting Aboard

#A few days after Thanksgiving in November 1962 Michelson was tied up starboard side to a pier at the Harland & Wolff shipyard in Belfast, Northern Ireland. After a long transatlantic flight in propeller airplanes via Gander, Newfoundland and Glasgow, Scotland I arrived in the middle of the night. An empty chair greeted me at the top of the gangway. Nobody was in sight. Poking my head through the hatch, I found a few of the merchant marine crew hanging out in the bosun's cabin. One of them told me "just go down those stairs over there ... that's where the Navy is". Thus began a most memorable two year cruise on a survey ship.

Flying Tiger

How I traveled from New York to Northern Ireland, or Flying With the Tigers.

Along toward the end of November in 1962 I reported into MSTS (Military Sea Transportation Service) Atlantic, which then resided in a massive collection of huge warehouses, piers and railroad tracks on the south Brooklyn waterfront. This was the Brooklyn Army Terminal, once the home of troopships and freighters transporting war materiel. MSTS was the navy's own steamship company, operator of survey ship USNS Michelson.

Brooklyn Army Terminal, probably c. 1950.

I was there to receive back pay and travel authorization to reach Michelson which I understood was in port at Belfast, in British Northern Ireland or to be there soon. Two other sailors destined for TAGS ships were in attendance, one headed for Barcelona to meet Dutton and the other destined for Athens, where Bowditch was expected at nearby Piraeus.

The MSTS disbursing office handed me a minor windfall of cash, as I had been on an independent per diem assignment for about three months in Rochester, New York, attending Friden Flexowriter school. Following that, they gave me my travel papers.

Before leaving the Army Terminal, I had a quick look at the travel authorization. It had me going to Athens instead of Belfast. This was a problem. While it might be an interesting trip it would put me in the wrong place, headed for the wrong ship. Perhaps I could get a free tour of Europe this way. And maybe captain's mast. No, not a good idea.

As all this was clearly incorrect, it was back to the MSTS travel office. My complaint was met by a scowl rather than an apology. An hour later the problem was sorted out. All I had to do was appear at McGuire Air Force Base in New Jersey on the following Sunday for my flight across the Atlantic. I was free to leave. Saying goodbye to the other navy guys, one of whom I was to see again in Barcelona, I headed for my parents' house on Long Island.

On Saturday I took the train to New York. I was going to stay in a hotel overnight to avoid missing connections. It was kind of a long Greyhound ride down to McGuire AFB, which was adjacent to Fort Dix, then the army's boot camp. 

Lockheed L-1049H Super Constellation. Typically, five were needed to fly it: captain, first officer, 
radio operator, flight engineer and navigator.

A happy surprise was that my transatlantic trip was to be aboard a chartered Flying Tiger Lines Lockheed Super Constellation rather than an MATS (Military Air Transportation Service) air force transport plane. There were a few other things I didn't know:
  • The Flying Tigers had been crashing these graceful looking planes quite frequently.
  • The transatlantic trip would take 14 hours, including a refueling stop at Gander.
  • This flight was going to Scotland, while I was supposed to go to Northern Ireland.
  • Piston powered planes make a dreadful droning noise if the engines are not synchronized.
By 1962 all the major airlines had switched to planes with jet engines, the Boeing 707 and Douglas DC-8. The big holdout was TWA, which kept on flying their Lockheed Constellations pending arrival of Howard Hughes' choice of jet transport, the very fast but commercially unsuccessful Convair 880. So, the military got to ride on the surplused slower planes with propellers. Oh well.

Most flights stopping to refuel at Gander, Newfoundland were westbound, but our Flying Tiger headed east toward Scotland stopped there anyway. It was evening by the time we arrived. A truck with a lighted FOLLOW ME sign greeted us upon landing. We followed him to the terminal. There, another lighted sign, this one much bigger, read GANDER, which I recall seeing in some semiforgotten movie.

Ours was the only plane there. The terminal was empty but the gift shop, restaurant and bar were open. Thinking to have a drink (or two) of the local libation, I told the barman "I'll have a Canadian ale". Years later I learned that screech, a distilled spirit like rum, was the local stuff in Newfoundland.

An hour later we were off again. I had brought the Sunday New York Times along to have something to read. One of the flight crew walking by told me "you should hang onto that until you get where you're going ... they'll like to read it". He was right.

Dinner was a baloney sandwich, apple and candy bar, all served in a little white cardboard box. Apparently this was the standard egalitarian form of catering on MATS planes, so we got the same on our charter flight just to show us we were nothing special. 

Our flight arrived at Prestwick Air Force Base (now Glasgow Prestwick airport) in Scotland at around dawn. There a UK customs official lectured the military passengers against bringing in contraband items then let us go. The helpful military travel office there provided me with directions to get to Northern Ireland. No one else was headed there.

I was to take a taxi into Paisley (they pronounced it "Pees-lee") where I was supposed to catch a train to Glasgow. Then I had to make my way to the BEA (British European Airways) city ticket office where I could hang out until a bus connected with my flight from Glasgow's Renfrew airport to Belfast in the evening. Simple, huh?

I left my stuff with BEA and walked around Glasgow a bit, had lunch, then spent the rest of the day relaxing and waiting in their office/city terminal. From somewhere two MSTS merchant mariners appeared, both headed for Belfast and Michelson. One was a relief first mate, the other guy I don't remember. We were all waiting for the same flight.

One of BEA's Viscounts.
Our airport bus appeared at around sunset. BEA's short flight to Belfast was on a Vickers Viscount. BEA and BOAC (British Overseas Airways Corp) merged in 1974, renamed British Airways.

All three of us shared a taxi from the Belfast airport to the Harland & Wolff shipyard. There in the yard where RMS Titanic was born was USNS Michelson, to be my home for the next two years.

Michelson at Sea

Starboard side view of USNS Michelson (TAGS-23) in 1961.  Click image for large view.

Three Survey Ships

Michelson was one of three survey ships put in service in late 1958. All were Victory class cargo vessels (VC-2) converted in much the same way with similar deep ocean survey equipment and electronics. All were dedicated to the same project. The Military Sea Transportation Service (MSTS), now known as Military Sealift Command (MSC), operated them with merchant marine crews, US Navy detachments and civilian oceanographers.

Initially, USNS Bowditch (TAGS-21), USNS Dutton (TAGS-22) and Michelson (TAGS-23) operated out of Norwegian ports, principally Bergen, surveying in the Norwegian Sea.

Bowditch and Dutton were named for the authors of the two standard American textbooks on shipboard navigation. Michelson’s name commemorates the discoverer of the speed of light, Albert Abraham Michelson (1852-1931), a Polish immigrant who became a US Navy commander and professor of physics at the US Naval Academy in Annapolis.

Both USNS Bowditch and USNS Dutton had long survey careers, steaming until 1988 and 1989, respectively. Michelson was found unseawothy by the US Coast Guard and was taken out of service in 1975. It was replaced by USNS H. H. Hess (TAGS-38), a C4 hull (ex. SS Canada Mail) in 1978. Hess suffered a boiler meltdown and in 1992 it too went out of service.