Project Artemis

Project Artemis was a United States Navy acoustics research and development experiment from the late 1950s into the mid 1960s to test a potential low-frequency active sonar system for ocean surveillance.

The receiving array terminated at Argus Island, built on the seamount's top, with data processed at the laboratory that was also constructed for the project.

World War II experience prompted the U.S. Navy to examine the threat of Soviet submarines which had been improved by captured German technology.

By 13 November 1950 a letter contract had been issued to Western Electric to develop the bottom array system exploiting low frequencies.

The Sound Surveillance System (SOSUS), its name and purpose classified, was given the unclassified name Project Caesar to cover its development and maintenance.

[2][3] Much of the study focused on undersea warfare and the need for nuclear anti-submarine submarines but also, in looking at SOSUS, recommended research and development of potential long range, active sonar systems.

[4] With respect to the Navy active sonar project designated Artemis, to run from 1958 to 1963, an understanding of the ocean environment was vital.

If the project was to succeed the full efforts of every ocean scientist, technician and laboratory on the Atlantic coast was likely required yet there were only six to seven hundred such people that were qualified.

[5] As Project Artemis was undergoing tests in the early 1960s SOSUS tracked the first U.S. ballistic missile submarine George Washington across the Atlantic in 1961.

On 6 July 1962 the SOSUS array terminating at Barbados demonstrated detection range by identifying a Soviet nuclear submarine transiting off Norway.

[7] Project Artemis experimental and system development effort's goal was to define requirements for a long range, low frequency, active, sonar capable of detecting a submerged submarine at about 500 nmi (580 mi; 930 km).

[18][19] A test was made, after several years of development, with a submarine at the design range of 1,000 km and fitted with a transponder reacting to the active array's signal for reference.

Station keeping issues of the active array ship, degradation of the receiving system modules and poorly understood ocean acoustics were involved in the failure.

The Artemis receiving array was expected to demonstrate problems with multipath reflections but experienced considerable failure with floats upon which its configuration relied.

[21] The major technological limitation was found to be computing capability, particularly speed, that forced use of analog devices for beam steering and signal processing.

The project successfully proved techniques for developing and deploying high powered, phased active hydrophone arrays.

The passive receive array field consisted of ten parallel cables with 210 modules composed of 57 ft (17.4 m) masts mounting hydrophones.

[24][25][note 3] The strings were laid on the side of the bank using the U.S. Navy large covered lighter YFNB-12, reconfigured with a long overhead boom to handle the masts.

At the upper end of the approximately 4-inch (100 mm) cable a wire rope was attached and led to an explosively embedded anchor shot into the flat coral top of Plantagenet Bank.

[citation needed][note 4] The cables led to Argus Island tower(31°56′59″N 65°10′39″W / 31.9498°N 65.1775°W / 31.9498; -65.1775), located about 24 miles (39 km) miles from Bermuda in 192 feet (59 m) of water and erected in 1960, from which the signal was conducted to the Naval Underwater Systems Center's Tudor Hill Laboratory located at Tudor Hill, Southampton, Bermuda (32°15′56″N 64°52′43″W / 32.265417°N 64.878528°W / 32.265417; -64.878528).

[27] The laboratory was adjacent to Naval Facility Bermuda which was a classified operational Sound Surveillance System (SOSUS) shore terminus.

[34] The mutual element interference problems resulted in redesign and re engineering that continued past the Bermuda experimental period to the end of the formal Artemis experiments.

[43] The face of the array was tilted upward at eleven degrees so as to insonify the desired ocean layers from the 1,200 ft (370 m) operation depth finally selected.

[45] The array development and tests continued after the main experiment at Bermuda in an effort to resolve issues with high powered active sources.

The requirements included the capability to moor the ship above the fixed site, lower a foundation and affix it to the bottom using existing ocean drilling and cementing methods.

[46] The most significant modification to Mission Capistrano was the system for operating the source array at the required depth of 1,200 ft (365.8 m) through a large center well.

A dynamic positioning system of eight large outboard engines and station keeping on a bottom fixed transducer was planned.

The military at that time considered the single greatest security threat to the USA the possibility of a submarine-delivered nuclear warhead placed near a major American city.

Rapid advances in computer technology and the development of signal processing algorithms, such as the Fast Fourier transform, quickly gave the West the superior military position using multiple passive SOSUS arrays.

With the diminished threat of the Atlantic SSBN, vessels were equipped with Surveillance Towed Array Sensor System and deployed in the Pacific.