The need for a more capable Anti-Submarine Warfare (ASW) sensor for the Type 23 Frigate to replace the Sonar 2031 passive towed array is driven by the noise quietening advances in the construction both of SSNs (Nuclear Propelled Attack Submarines) and SSKs (Conventionally Propelled Attack Submarines).

The Staff Target for a fully integrated, variable depth, towed active and passive sonar system, designated S2087, to counter current and future SSN and SSK threats was approved in April 1994.

The sonar will significantly improve the Type 23 Frigate’s ability to detect, classify and localise submarines at a range beyond the threat of attack.

The sonar suite will be fully integrated into the Type 23 Combat System whilst requiring minimum change to the T23 Command System (DNA(1)). Sonar 2087 will be fitted to T23 Frigates during refit and integrated with the existing bow-mounted active sonar.

GENERAL CHARACTERISTICS/TECHNICAL PERFORMANCE

Sonar 2087 will transmit at frequencies lower than those used currently in RN Surface Ship active sonars. These lower frequencies take advantage of better propagation of sound, giving greater detection ranges. In order to exploit advantageous environmental conditions, the towed body, which contains the transmit array, can be deployed to the optimum depth for detection and tracking of the target. The transmit array is physically large and heavy and the whole handling system is to be designed to fit within the constraints of the current T23 Frigate quarter-deck dimensions.

Sonar 2087 also incorporates a passive array, as passive sonar detection of submarines remains an important ASW tenet. This array must be stored and handled using the space currently occupied by the Sonar 2031 winch and will feature digital telemetry rather than the current analogue system.

The active and passive modes are capable of independent streaming, recovery and operation and will facilitate easy transition between the two, such that uninterrupted operations can be achieved with the chosen mode while the other is streamed or recovered. Both the receive and transmit arrays are independently deployable to their optimum operating depths in order to provide the best possible sonar performance commensurate with the prevailing oceanographic conditions.

Sonar 2087 will be able to operate in a wide range of environments from the deep blue ocean to littoral and from tropical through temperate to arctic waters. It is possible to deploy and recover the active and passive outboard systems in sea conditions up to sea state 6. Both systems are also capable of operation up to the maximum operating sea state of the Type 23 Frigate. Sonar 2087 should not be affected by electrical storms or lightening strike. In addition, the operation of the active towed body and the passive array should be unimpaired up to normal cruising speed. All arrays are designed to survive up to the maximum designed speed of the towing unit/vessel.

The Sonar 2087 suite will be designed to integrate with the existing T23 Sonar 2050 bow mounted sonar, the future Surface Ship Torpedo Defence system and the T23 Command System (DNA(1)) via a Combat System Highway. It should require no increase in manning over that currently required for Sonar 2031 and the extensive use of Commercial Of The Shelf (COTS) hardware, re-use of software and the imposition of ILS disciplines should ensure reduced Whole Life Costs.

COSTS / IN-SERVICE DATE (ISD) / MAJOR MILESTONES / QUANTITIES

Project Resource Cost Summary at out-turn prices to the nearest £10M: £340M VAT Inc estimated acquisition cost. A total of 16 sets are planned to be produced, 12 of which are full sea-based sets. The remaining four are shore based part sets for: a Shore Integration Facility; a contractor reference set; and an assumed maximum of two sets for the training of both operators and maintainers.

In-Service Date (ISD) is the date at which the equipment achieves Initial Acceptance and is planned for May 2006. This will be followed by the achievement of Initial Operating Capability, planned for Jan 2007.

COMMERCIAL ASPECTS

The assessment phase was completed in 2000. The two competing contractors were Babcock Defence Systems Ltd and Thomson Marconi Sonar Ltd (TMSL). Main Gate approval was given in January 2001. In March 2001 TMSL (since re-named Thales Underwater Systems Ltd) was announced as the winning contractor and the Demonstration, Manufacture and Support contract awarded to them in April 2001. The initial contract is for the supply of six ship sets. There are also fixed-price options in the contract that allow for the purchase of a further batch of six sets and the Full Operating Capability increment.

INTERNATIONAL COLLABORATION

International collaboration was considered but because of the unique UK requirements and the constraints of the Type 23 Frigates it was decided that a national programme was more appropriate.