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.

Radio Navigation

During early days aboard Michelson three different hyperbolic navigation systems were used to provide control for the survey mission. All utilized the measurement of time and phase of signals from pairs of shore based radio transmitters to determine the ship's location. Those points of constant time/phase difference appear as hyperbolas on a nautical chart.

Measurements from two pairs of stations yield intersecting lines of position which can provide a position fix. Below, hyperbolic line A of station pair M-S1 intersects line B of pair M-S2. That intersection of two lines of position (LOPs) is a fix.

Loran C was the main, everyday radio navigator. Michelson had two Loran receivers, initially the SPN-28, originally intended for aircraft use, requiring a 400 hertz AC power supply. Later these were replaced with WPN-3A receivers, with optical analog to digital converter outputs feeding the NAVDAC computer, which calculated position data and sent to a printer for the on duty oceanographer.

There was good coverage throughout the ship's operating areas. Loran C was somewhat susceptible
to sky wave interference at longer distances from the transmitting stations. In the receivers at that time, ten microsecond errors could be a problem despite transmitted phase coding and receiver envelope matching. Phase comparison of the signals was made at the 100 khz transmitter frequency, 10 microseconds being the period of one cycle. Overall, Loran C had long range and good accuracy, there being nothing better available until the advent of satellite based systems. 

Most radio navaids typically referred their transmitters as master and slave stations, because the slaves were phase locked to the master station's signal, either through over the air synchronization or later using ultra stable cesium beam clocks. Now, in the world of non offensive speech, the generally acceptable, politically correct terms are master and secondary stations.

Two other radio position fixing systems were installed on Michelson at different times:

Decca Navigator in the early 1960s. Widely used in Europe and the UK, Decca stations transmitted continuous wave signals in the range of around 70 to 125 khz, each being a multiple of a basic frequency called "f" (about 14 khz). Decca receivers made phase comparisons at f. Four Decca transmitters, master (6 times f), red (8f), green (9f) and purple (5f), comprised a chain. Signals from two pair of stations were required to fix a position. Once a minute, each master/secondary station pair transmitted lane identification signals. Decca lanes and lines of position were printed on nautical charts of their service areas.

First used in the 1940s, Decca was widely thought to be the ancestor of Loran C because it was the original radio navigator to use signal phase comparison. Regrettably, it suffered from skywave signal contamination making night time use less than reliable.

A Decca Navigator system descripton can be found here.

Position fixing using Decca. Phase differences between master/secondary station pairs were displayed on decometers. A lane identification feature located the receiver between the correct pair of adjacent hyperbolic lines of postion.

Lorac was a proprietary system owned by Seismograph Service Corporation, then an Oklahoma oil exploration services company. Three stations, a red, green and center station transmitted continuously in the 1.7 to 2.5 mhz spectrum. Red and green frequencies differed from that of the center station by two audio frequencies, typically 240 hz and 600 hz. These difference signals were detected at the reference station and used to amplitude modulate that station's transmitter. Phase comparison at the receiver was made between the center/red and center/green difference frequencies and those transmitted by the reference station. For my article on how Lorac worked have a look here.

The Navy's underwater test range in the Bahamas had a Lorac chain, which Michelson used while conducting seemingly endless sea trials in 1964. Readings were taken manually from the Lorac receivers and position fixes computed off line with the Bendix computer. The biggest problem I noticed with Lorac was its lack of lane identification. Two receivers furnished came with strip chart recorders which helped maintain lane count. A Seiscor tech rep came along too.

Once we had the Lorac lane count flown out to us from Patrick Air Force Base. A Navy ET who had previously been aboard Michelson brought us the correct count in a Lorac equipped helicopter.

How Did Lorac Work?

Why, one might ask, are you describing an obsolete radio navigational aid when now we now have the great ubiquitous GPS to tell us where we are and how to get where we think we want to go? Perhaps because between Loran C in the navy and Decca with its namesake company these "hyperbolic" systems kept me gainfully employed and out of trouble for about seven years. Also, it's intellectual curiosity. Lorac was a bit of a mystery. Despite having used it while Michelson was in the Bahamas I never fully understood how it worked. There is not much detailed information on the web other than a coast guard officer's masters thesis and a couple to oil survey field reports.

And it worked pretty well. Lorac meaning "long range accuracy", was a product of the Seismograph Service Corporation of Tulsa, Oklahoma, which owned the patents. Equipment was built by a subsidiary called Seiscor for both civil and military markets. They also supplied technical support in the field. 

Originally intended for oil exploration surveys, Lorac transmitter chains covered the US gulf coast from Texas to the Florida panhandle during the late 1950s to 1960s. 

The navy was a big user of Lorac for inshore and coastal surveys as well as in sea searches to locate lost ships and aircraft. Ruggedized field deployable tactical  transmitters and receivers were used by regular navy survey ships of that time. A photo of AN/SRN-7, the navy's Lorac receiver, is below.

AN/SRN-7 US Navy Lorac receiving equipment. From left: antenna coupler, indicator and receiver.
Michelson used the permanent Bahamas Lorac chain for several months during 1964. We had two sets of receiving equipment and the services of a Seiscor field engineer aboard. Position fixes were obtained from visual readings of the receiver phasemeters entered manually into the ship's Bendix general purpose computer.

Lorac transmitters operated in the 1.7 to 2.5 mhz spectrum, then also the home of Loran A and the 160 meter amateur (ham) radio band. This is just above AM standard broadcast. Like Loran C, Decca and other radio navaids, Lorac was a "hyperbolic" phase comparison system. 

The useful range of a Lorac system was a bit over 100 miles in the daytime, but perhaps half that at night due to skywave interference. Accuracy was said to be within 2 1/2 feet at best.

There appears to have been two slightly different flavors of Lorac; the drawing below describes the variety used in the Bahamas in 1964. This was called Lorac B.

Three land based stations transmitting unmodulated continuous wave signals were called green, red and center. In this example frequencies of the green and red stations differed from that of the center station by 600hz and 240hz respectively. These three signals were received at the reference station and the difference signals (audible tones of 600hz and 240hz) detected. 

Amplitude (AM) modulated by the two tones, the reference station transmitted on a frequency unrelated to the other three but in the same band. Green and red stations did not need to be phase locked to the center station as minor variations would be reflected in the reference station's two modulating tones as well.

Aboard ship, the Lorac receiver measured the difference in phase between the green/center 600hz difference (beat frequency) and the 600hz modulation on the reference station's signal. Similarly, the red/center 240hz beat frequency was compared with the reference station's 240hz modulation. Phase meters indicated the green and red phase differences. 

Counters kept track of the lane counts, a lane being about 80 meters wide along the baselines between station pairs. Width of Lorac lanes diverge from the green/center and red/center baselines since points of equal phase describe hyperbolas. Thus, Lorac was potentially very accurate as the smallest movement of the mobile (shipboard) receiver meant a large phase difference. 

Being that no means of lane identification was provided, Lorac receivers had to be calibrated at a known geographic position at the beginning of a survey.

Another version of Lorac operated without a reference station in a time shared green/red mode. Instead of radiating a single frequency, the center station switched between two different ones at 10 times per second. Both differed from the green and red frequencies by audio tones, just as in the above diagram. This switched green/red mode was called Lorac A.

Both the green and red stations were furnished with Lorac receivers. Green received the center and red signals and used the difference (beat) frequency to modulate its transmission during the "green mode". Similarly, in the "red mode" the red station modulated its signal using the center/green beat frequency.

As well as being more economical, Lorac A switched mode was probably used to allow a greater choice of operating frequencies in the narrow band available. It also may have prevented interference from the adjacent Loran A chains which operated in the same frequency band.

All of this was a bit more complex, but very clever, very accurate and worked essentially the same as the four station Lorac B.

Until GPS came along Lorac was probably the most accurate radio navaid for survey control. While it lacked the range of Decca and Loran C it was widely used by the US Navy as well as by the oil industry.

Update 1/18: An excellent system description of Lorac can be found in Review of Marine Navigation Systems and Techniques, archived on the web. This is dated 1965, a Department of the Navy, Bureau of Ships publication. Here is a link to the chapter on the Lorac radio navigator.


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.