Raven ES-05 AESA Brings Wider Eyes For The Gripen NG
ForcaAerea.jpgA recent report in the November issue of Brazilian magazine Revista Força Aérea by Rudnei Dias da Cunha took a hard look at the Raven ES-05 AESA for the Gripen NG which is a contender for the Brazilian Air Force’s order.
According to the report, the air-to-air and air-to-ground modes have successfully been integrated to the Raven 1000P radar prototype, achieving the expected performance. A special emphasis was given to the air-to-ground imaging capacity at great distances, with the Raven 1000P producing excellent medium-resolution to high-resolution imaging in synthetic aperture mode.
Excerpts from the report:
The Raven ES-05 is an evolution of the fire control radars of the Raven family (500E and 1000E), manufactured by Selex Galileo. Selex Galileo has the unique distinction of not only creating an array of fire control AESA radars (the Vixen E family) but also a number of AESA surveillance radars (the Seaspray E family).
The Raven ES-05 radar uses about one thousand TRMs capable of generating high-power radar beams. The radar also generates a wide array of wave and processing regimes, capable of implementing a set of air-to-air seek while tracking, combat, air-to-ground and air-to-sea modes.
In air-to-air operation, the radar is capable of listing and monitoring multiple spaced targets, making maneuvers and facing “jamming” while, simultaneously providing course corrections to semi-autonomous guidance Beyond Visual Range (BVR) missiles. In air-to-ground surveillance and target control mode, the radar provides a variety of high-resolution RF images over large terrain areas, as well as the detection of slow land vehicles. The use of AESA technology also facilitates the effective simultaneous operation of the air-to-air and air-to-ground modes.
An important technological innovation introduced by Selex Galileo in the Raven ES-05 was the “Swashplate” concept. The AESA radars had their antennas made up by a matrix of TRMs, in a flat circular configuration, without mechanical movement, attached to the bulkhead of the front fuselage of the aircraft. This type of radar antenna can move its electronic beam anywhere inside a field of view (FoV – Field of View) to detect and track targets. However, the FoV of these types of AESA is limited to about +/- 60 degrees in relation to the longitudinal axis of the aircraft and its front. The Swashplate concept consists of a mounted AESA antenna inclined in a ring with electromechanical rolling. The key-component of the Swashplate is the rotating joint that transfers the cooling liquid, control and power signals and RF signals from and to the radar receiver behind the aircraft bulkhead.
The rotating joint, as it occurs with the radar units, has to occupy the smallest space possible, with minimum operating weight and reliable manner, based on the hostile operating environment on-board a fighter jet. The inclined layout of the Swashplate allows the total scanning angle of the radar to be the same as the maximum electronic angle plus the angle of inclination, that is, an angle of 45 degrees of inclination will allow a total scanning angle of 105 degrees.
In long-range air-to-air combat, the highest FoV means that a Gripen can maneuver at an angle in relation to the viewed axis of the target (off-boresight angle) greater than what is possible with an AESA radar with fixed TRMs matrix after launching a BVR missile and still be able to send updated information to the missile. In turn, a potential enemy will be limited to deviating up to 60º of the viewed angle after launching the BVR missile. Therefore, it will still be displacing towards a missile launched by Gripen while this, in turn, will be flying perpendicularly or even away from the enemy missile. Simulations made showed that this capacity should not be underestimated and it will have a devastating effect in the engagement result of the BVR.
In a dogfight, the air-to-air WVR (Within Visual Range), the repositioning capacity of the antenna with Swashplate will enable the detection of targets “over the shoulder” of the pilot, together with helmet mounted sight and next generation air-to-air WVR missiles, with high maneuverability, will offer the Gripen NG pilot even more advantages.
Another advantage offered by the Swashplate is its use in recognition missions because the higher FoV enables images generated by the Raven radar operating in synthetic aperture mode (SAR) to be wider, offering greater coverage of the desired region.
An AESA radar allows its antenna to be used for digital information exchange (data linking) between aircrafts that “talk” a same communication protocol and Raven is not a exception to the rule. Therefore, it is possible for a Gripen NG to detect targets with its radar and digitally transmit the information to other Gripen NG fighter aircrafts without them using their own radars, with this increasing the stealth effect of the aircrafts and increase their probabilities of success in the combat. Hence, a single Gripen NG can operate as a “mini-AWACS”, able to detect targets and obtain SAR imaging simultaneously, and disclose this information to other aircrafts.
The Raven ES-05 prototype called Raven 1000P is based on the Vixen 1000E radar and was recently taken to a Gripen demo aircraft. This system was used to prove the installation ease and testing of the arm-system radar interfaces. The prototype detected air targets successfully and generated high-resolution synthetic aperture (SAR) images.
The development program of Raven ES-05 is rapidly progressing and is as forecasted. The design of the hardware is practically complete with all the main subsystems, be it in production or integration. Deliveries of software are also progressing gradually. The integration of the standard production radar will begin at the company’s headquarters in Edinburgh at the end of this year, with delivery of the first system to Saab in the beginning of 2012.
Besides the Raven ES-05, the Gripen NG will have an integrated IRST, the Skyward-G. Manufactured by Selex Galileo, both can be seen in the illustration above, and their use by Gripen NG will enable active and passive tracking, therefore increasing the capacity of the aircraft.
Selex Galileo developed a prototype version of the Raven ES-05 called Raven I000P, from the Vixen 1000ES. Since 2010, Raven 1000P has been tested in flight, showing operating modes with the radar in flight simultaneously showing the efficiency of the Selex Galileo and Saab teams in the integration of the radar to Gripen NG in a short time span.
One of the major characteristics of Raven, already present in Vixen 1000ES, is a rotating platform that allows the radar antenna to cover a scanning angle of +/- 105°. This enables the Gripen NG to move away form the target, rapidly making a curve after launching the missile, while still keeping the target in sight; with this, a terminal active phase short duration missile (i.e., after finding the target with its internal systems) can undergo trajectory corrections sent by the Gripen NG.
The Gripen NG demonstrator shows some of its weapons, such as the air-to-air WVR IRIS-T missiles at the tips of the wings and the air-to-air BVR Meteor missiles under of the wings. Selex Galileo is developing the Raven ES-05 radar to equip the Gripen NG. Based on the Vixen I000ES AESA radar, Raven will have a control hardware developed by Saab Microwave Systems that will enable Saab to own the control of the radar control software, preventing possible sales restrictions to potential buyers.