The periscope is the eye of the submarine and is meant to keep a watch on the surface without it being detected by surface craft or from the air. The principle of the design of a periscope is simple and based on reflection of objects through mirrors or prisms but it is actually a complex piece of equipment. Earlier periscopes had mirrors held at 45 degrees but these were later on replaced by prisms. They were also rigidly fixed but soon periscopes were designed to be manually lowered, raised and rotated. Thus the orders ‘down periscope’ and ‘up periscope’ was dramatically shown in war movies. Standing watch at the periscope is thus called ‘dancing with the gray lady’. At greater speeds the periscope tended to bend due to pressure thus they were placed in double tubes, where the outer tube withstood the pressure. Another problem was that the rotation of the upper prism caused the image to be seen upside down which was corrected later with better design. Germany was largely responsible for modernising the submarine periscope. Length of periscopes could be as much as 18 metres (60 feet) thus when a submarine is submerged at depth equal to the length of the periscope, it is called ‘periscope depth’. Due to such large lengths, an effective periscope will require more complex arrangement of lenses and prisms and twin telescopes fitted inside the periscope tube.

The US term ‘sail’ or the British term ‘fin’ of a submarine is the tower-like structure located on the topside of the submarine. Earlier submarines housed the conning tower which included the command and communications data centre, periscopes, radar and communications masts. Now most of the functions are carried out from the hull thus sail is no longer considered as the conning tower but the tower is still in use for other purposes. Modern submarines are equipped with two types of periscopes, one on the right (starboard) side and one on the left (port) side like Los Angeles-class nuclear powered submarine USS Springfield which has a Type 2 attack scope on the starboard side and a Type 18 search scope on the port side. The Type 18 scope is limited to operations in the daylight and takes photographs with a 70mm digital camera which are then displayed on a television monitor. Some periscopes also have night vision capability, a still camera, a video camera and can magnify images. Conventional optical periscopes have a few disadvantages. First one is that when the periscope is in use then the submarine has to operate at periscope depth which is just below the surface thus it is easy to detect. Also a conventional optical periscope runs the entire height of the ship to house the periscope thus it limits the space of the sail and interior compartments. Lastly it can accommodate only one person at a time. To overcome these disadvantages a new AN/BVS-1 photonics mast has been developed which made its debut in 2004 in Virginia class of US submarines.

Photonics Mast

Electro-optic sensors are replacing the mirror-cum-lens arrangement of the conventional telescopes which have done valuable service for almost 80 years. The photonics mast (also called optronic mast) has a rotating head which emerges over the surface of the water and houses multiple electrooptical sensors. The masts are equipped with a set of separate cameras including a colour camera, a high-resolution black-andwhite camera and an infrared camera. There is also a mission critical control camera housed separately in a pressure-proof and shock-hardened casing. An eye safe laser range finder which provides accurate target range and assists in navigation, just about complete the sensor components of the photonics mast.

Photonics mast with its electro-optical sensors provide imaging, navigation, electronic warfare and communications functions

The electro-optical sensors are connected by fibre optics cable to twin work stations and the commander’s control panel. The photonics masts can be controlled by a joystick from any of these stations. Each station consists of two flat-panel displays with a standard keyboard. Interface is through a trackball and images are recorded on both video cassette and CD-ROM. The smaller size of the periscope allows more flexibility in the location of the control room. In the Virginia class of submarines, the control room is located in the more roomy second deck instead of the crowded upper deck. Photonics mast with its electro-optical sensors provide imaging, navigation, electronic warfare and communications functions. They also do not retract into the submarine’s hull but open up like a car’s radio antenna. Photonics mast also provide the submarine’s captain space, better layout and improved situational awareness.

Global Survey

The population of conventional and nuclear submarines is minuscule as compared to surface ships thus the requirement of periscopes/photonics mast is small. It is also high-tech niche business. Thus there are only few companies who develop and make periscopes/photonic masts. The companies and their products are given in succeeding paragraphs.

Airbus DS Optronics

Carl Zeiss Optronics GmbH has changed to Cassidian Optronics GmbH from October 1, 2014. Cassidian Optronics is a 100 per cent subsidiary of Airbus Defence and Space and operates as Airbus DS Optronics GmbH. Brief details of its products are:

Submarine periscopes. Airbus DS periscope systems contain a high-quality optical observation channel with a binocular tube. Their lines of sight are stabilised in elevation and azimuth by means of gyroscopes. Observation and operation are controlled directly on the periscope or from a combat system control console. The periscope systems are equipped with various high-resolution cameras. The standard configuration includes a colour TV camera, a residual light TV camera and a digital camera. Highly accurate long-range and eye safe laser rangefinder can also be integrated in addition to the passive optical rangefinder system.

SERO 400 with OMS 100. The SERO 400 periscope system can be installed and used in combination with the OMS 100 optronics mast system. The OMS 100 optronic mast system is a compact state-of-the-art optronics mast which requires no hull penetration. It is fully automatic thus ideal for missions where the sensor is exposed for an extremely short time.

SERO 250. The SERO 250 is a compact, state-of-the-art periscope system that was specifically designed for retrofit programme solutions. It can make use of existing hoisting mechanisms, periscope bearings, seals, etc. Its small size makes it ideal for boats where space is at a premium. The SERO 250 is available in an attack and search version and the search version includes a thermal imager.

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Briefly their systems are:

Series 20 Attack Periscope System. Series 20 APS attack periscope system is highly reliable and can be fitted on all types of conventional and nuclear powered submarines. It is also possible to retrofit them. The system can carry out multiple roles like surveillance, attack, navigation safety, intelligence gathering and electronic warfare self-protection. Its modular design enables the system to combine high-quality direct optical channel with four magnifications and the latest technology optronic sensors with GPS/ESM-EW antennas. In addition, the periscope includes a low head diameter and stealth features. It has low neck cross-section, high-definition optics, digital optronic sensors support and can be remotely controlled. Optronic sensors are low light level TV anti-blooming camera and a HDTV colour camera. IR camera is an optional sensor.

Series 30 Search Optronic Mast (SOM). Series 30 SOM is a modern which can be fitted on all conventional and nuclear powered submarines or can be retrofitted. It has stealth features and can carry out multiple roles like panoramic detection and identification, navigation safety, intelligence gathering and electronic warfare/optronics self-protection. The system is modular in construction, is non-hull penetrating, can simultaneously accommodate up to four advanced optronic channels and a full range of electromagnetic antenna. Its optronic sensors are third-generation high-definition 3-5 micron thermal imager, HDTV colour camera, low light level TV anti-blooming camera and eye-safe laser range finder.

Series 30 Attack Optronic Mast (AOM). Based on the Series 30 Search Optronic Mast design, it is a discreet nonpenetrating attack optronic mast which is suitable for conventional and nuclear powered submarines. It is modular in design, can simultaneously combine up to four optronic sensors and an ESM/GPS antenna. The Series 30 AOM features very low signature due to its small size above the water surface. Its fully digital technology allows a high level of optronic performances. The optronic sensors fitted are third-generation high-definition 3-5 microns thermal imager and a HDTV colour camera. Optional optronics are eye-safe laser range finder, short wave infrared thermal imager and day/night backup camera.

L-3 KEO

L-3 KEO (formerly Kollmorgen Electro-Optical) is the sole designer and manufacturer of all US optronic mast sytems. In addition, L-3 KEO has installed optronic masts on many international platforms. These systems include precise, high-resolution electronic imaging and integrated sensor packaging. Integrated sensor optics can include electronic support measures, direction finding , coplanar strip (CPS) or communication antennas, and low observables technology. L-3 KEO has also designed and produced the Universal Modular Mast (UMM) which has been chosen as common equipment for above water sensors on many US and international submarines. Calzoni, a subsidiary of L-3 KEO, designs and manufactures submarine masts, including snorkel masts, as well as hull induction valves, gas exhaust valves and seawater hull valves.

The Virginia class is one of the first submarines without a traditional optical periscope that penetrates the vessel’s pressure hull but extends upward to enable commanders of submerged submarines to view the situation on the surface

Universal Modular Mast (UMM) made by L-3 Calzoni. The UMM has been integrated and tested with the optronic, communications, satcom high data rate and electronic warfare underwater sensors. It is modular in design, re-configurable with different sensor packages, has built-in closure doors actuation system, operate at high speed at periscope depth, high elevation stroke, noiseless raising/lowering control, radar absorbing material coating is optional, drop-in/dropout installation, requires no alignment and has low life-cycle costs.

During April 2014, US Navy contracted for 16 UMM systems for the Navy’s Virginia class submarine fleet. The Virginia class is one of the first submarines without a traditional optical periscope that penetrates the vessel’s pressure hull but extends upward to enable commanders of submerged submarines to view the situation on the surface. They are also being fitted on Ohio class cruise missile submarines. The UMM can host five different sensor configurations: the photonics mast, the multi-function mast, the integrated electronic mast, the high-data-ratemast, and the photonics mast variant. The Navy’s Virginia class attack subs each have a bank of eight of these sensor masts, while the Ohio class cruise missile subs each have banks of four UMMs.

Submarine Periscopes. L-3 KEO is the sole designer and manufacturer of all US periscope systems. In addition, L-3 KEO has installed periscopes on several international platforms, including the TR1700, the T209, the Walrus, the A-19 and the Sauro Class submarines. These systems include precise, high-resolution optics, and integrated sensor packaging. Integrated sensor options can include electronic support measures, direction finding, GPS, communications antennas, thermal imaging, lowlight imaging or image intensified cameras and low observables technology.