by Max Barry

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by Albion invicta. . 60 reads.

Verhun Defence Systems - 'Clear Sky' AESA Radar

The V-AESA-R1 "Clear Sky" is naval radar system designed and developed by Verhun Defence Systems.

The V-AESA-R1 Clear Sky is a multi-function dual-face active electronically scanned array radar produced by Albion-based Verhun Defence Systems. It is encased in a rotating dome made from high-carbon steel and is covered with an anti-radar paint. It was developed primarily as a component of the Norstham developed Fleet Air Defence System (FADS) naval air defence system, however, Verhun have stated that the system will be compatible with other regional systems.

Clear Sky was developed from the ground-up to function as a multi-function radar that can detect all types of targets out to a distance of 400 km. Additionally, it is capable of tracking hundreds of targets at any one time. FADS uses this information to assess and command target priorities, and calculate the optimum launch time for its JAMM/JAMM-ER missiles.

Clear Sky AESA Naval Radar

2012 composite photographed at
less than one second interval showing
Clear Sky antenna rotation


Solid-State AESA Radar


Albion invicta


Verhun Defence Systems

Unit Cost



2011 -


2012 -


In Service

Primary Users

Albion invicta


24 GHz (S band)


~400 km


25 kW


Long and Medium-Range Search
Surface Picture Search
High-Speed Horizon Search
High-Angle Search and Track
Multiple Target Tracking and
Multiple Channel Fire Control


Development of Clear Sky, an operational derivative of the Albion Naval Radar Project (ANRP) technology demonstrator, which began in 1989, and it was first publicly revealed in 1991. No prototype was constructed at that time Verhun Defence Systems estimated that Clear Sky would be ready for production in 1994.

In 1993, Albion wanted a standard air defence warship for itself and its international partners. The ship proposed to meet this need, the Tranquility Light Destroyer would sail with the ANRP multifunctional radar for the target acquisition and fire control roles. Due to delays in finalising the design and partner differences, the initial baseline design was delayed until 1994. This pushed the entry-to-service date to 2002, meaning that the Nngjng build schedule matched Clear Sky's schedule. Accordingly, Albion Invicta suggested that Clear Sky replaces other radar systems within the international partners in order to substantially increase the ship's combat efficiency. At the time, other partner nations did not want Albionite dominance over the project forcing Albion Invicta to go independent of the Tranquility project.

After withdrawing from the multi-national project, Albion Invicta decided to go it alone with the Tranquillity class destroyers. An order for the first batch of three Tranquillity destroyers was placed by the end of 2000. In July 2001 it was announced that the second batch of three destroyers had been ordered. This order, bringing the total of Nngjng ships to six, came three years earlier than expected. Initially, 12 Tranquillity class ships were to be produced, but the quantity was reduced to eight vessels. The program was later capped at six destroyers.

Being the first naval radar developed in Albion for a prolonged period of over a decade years, the designs of the Clear Skies radar have experienced several major revisions and the prototype differs significantly from the production version. The very first prototype of the series Qngtiān featured the main array in the four-metre diameter octagon S-band array configuration, with a total of 3456 transceivers for searching and tracking, and a small 60 centimetres diameter C-band array with an approximate area of 0.3 square meters to control surface-to-air systems. As the control requirement became more stringent, the design of Qngtiān proved to be inadequate and the production versions adopted a different array layout instead.


The production version of Clear Sky radar has a new S-band array with more than five thousand transceivers in each face, with increased range of four hundred kilometres. The first production version of Clear Sky is V-AESA-R1 on Tranquillity destroyers and it utilises air cooling system, which is to be replaced by a liquid cooling system in its future onboard any future planned destroyer and frigate upgrades.

Conventional radars, consisting of a rotating transmitter and sensor, have limited power, are vulnerable to enemy jamming and perform only one function - with separate units therefore required for surveillance, tracking and targeting.

As an active array, Clear Sky uses software to shape and direct its beam allowing several functions to be carried out at once and, through adaptive waveform control, is virtually immune to enemy jamming. Active arrays have both longer range and higher accuracy than conventional radars. The beam-directing software uses sophisticated algorithms to schedule looks so that the potentially hundreds of active tracks are maintained with maximum accuracy.

Clear Sky uses two planar arrays to provide coverage over only part of the sky; complete coverage is provided by rotating the arrays, essentially similar to the way conventional radar systems operate. This is in contrast to the Norstham-built fixed-array as part of their FADS program, fixed in multiple places to provide continuous coverage of the entire sky. Whilst this may seem to be a disadvantage, the Clear Sky radar rotates at 30 revolutions per minute, with two back-to-back arrays, meaning no part of the sky lacks coverage for more than one half second on average - the precise time varies as the beams can also be swept back and forth electronically. In addition, the use of a smaller number of arrays allows the system to be much lighter, allowing placement of the arrays at the top of a prominent mast rather than on the side of the superstructure. Placing any radar emitter at higher altitude extends the horizon distance, improving performance against low-level, sea-skimming targets; Clear Sky is at approximately double the height above the waterline than the arrays of its regional equivalents.

Verhun have also claimed that Clear Sky eliminates the need for several separate systems. They suggest that on the Tranquillity destroyer, a long-range 3D radar that is designed to work in partnership with Clear Sky "really is superfluous and is not needed to perform the mission of the ship". Verhun Defence Systems believes that the reason the large volume search radar has been incorporated into FADS is "more of a historic nature, associated with [the] work sharing issues" that were a huge problem during the multi-national efforts in the late 20th Century.

Some tasks are difficult to combine, for example (long range) volume search takes a lot of radar resources, leaving little room for other tasks such as targeting. Combining volume search with other tasks also results either in slow search rates or in low overall quality per task. Driving parameters in radar performance are time-on-target or observation time per beam. This is perhaps the key reason why the Albionite Navy selected a long range radar to complement Clear Sky on their destroyers.

The performance of both the Clear Sky radar and JAMM/JAMM-ER missiles will give the Albionite Navy a highly-capable anti-air warfare capability.


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