Detection, identification, interception and destruction are the four vital essentials of Air Defence (AD) operations. Detection is the key function, which in turn leads to the other three progressive activities. Radar remains the primary active sensor to detect targets in air and space coupled with many other passive sensors. Rapid advancements in radar technologies over the years have greatly improved the probability of detecting airborne targets and their detection ranges.
Radars need to detect airborne intruders at the earliest to neutralise them well before they enter forbidden territory and provide AD cover to air operations in enemy territory. However there is a limit to which ground radars can be elevated to enhance the LoS. Thus, the need evolved to mount surveillance radar on transport aircraft. An aircraft with surveillance radar flying at high altitude achieves unlimited LoS and can detect, track and identify aircraft flying even at low-level beyond a distance of 400 km. This requirement led to transport aircraft being modified to carry surveillance radar. This eventually evolved as today’s airborne surveillance platforms known as Airborne Warning And Control System (AWACS) and Airborne Early Warning & Control (AEW&C) system. Large detection ranges of AWACS/AEW&C systems provide trans-border visibility deep inside enemy territory while flying well inside friendly territory. The trans-border visibility enables early detection, identification and threat analysis of possible air intruders while providing AD cover to own aircraft executing missions in enemy territory. AWACS/AEW&C systems besides early detection and identification are force enhancer by virtue of their capability to manage the air-battle, execute networked Command & Control (C2) functions and guide fighter interceptors.
All modern AWACS/AEW&C systems are made up of a suite of several sensors, communications and computing systems that truly make them a C4ISR system. The main sensor of all AWACS/AEW&C system is the Primary Radar (PR) coupled with Secondary Surveillance Radar (SSR) for Identification of Friend or Foe (IFF) to detect airborne targets and ships at large distances in all weather conditions. To mount surveillance radar on transport aircraft and operate it while flying is an extremely complex engineering process and only few countries have successfully designed and developed airborne surveillance platforms.
India felt the need to develop indigenous AWACS/AEW&C in the early 80s. Defence Research & Development Organisation (DRDO) formed Airborne Surveillance Warning And Control (ASWAC) Project Office in July 1985 to carry out a feasibility study for the development. Based on the feasibility study, ASWAC Project Office was converted into Centre for Airborne Systems (CABS) on 01 February 1991 and entrusted the responsibility of design & development, testing, evaluation and certification of airborne surveillance systems.
Immediately after its formation, CABS undertook a project to convert an Avro aircraft into an Airborne Surveillance Platform (ASP). CABS successfully developed and demonstrated critical technologies related to PR and data-links. Unfortunately, the Avro aircraft modified as ASP met with an accident in 1999 plunging CABS into despair. CABS resurrected when Indian Air Force (IAF) initiated a case to procure AWACS from Israel and in parallel IAF also projected a need for DRDO to develop an AEW&C system on an executive jet aircraft. IAF and DRDO jointly evolved broad Operational Requirements, based on which DRDO submitted a proposal for Government approval in August 2004. Cabinet Committee on Security (CCS) approved the proposal for indigenous AEW&C within a week of its submission with a mandate to develop AEW&C on Embraer-145 executive jet.
‘Netra’ the indigenous AEW&C is equipped with the 1st indigenous AESA based PR that includes electronics, transmit receive modules, antenna array etc. designed and developed by DRDO and manufactured in India. An indigenously developed Active Antenna Array Unit (AAAU) is mounted over the aircraft fuselage on four pylons to house the PR and SSR. The AAAU houses front-end electronics of PR and SSR, their cables, cooling system and has two radar antenna arrays mounted back-to-back facing outwards in the AAAU to detect targets on either side of the aircraft. Externally the AAAU is designed to minimise drag and withstand aerodynamic/inertia/aero-elastic loads in flight. The PR offers multi-function, multi-mode capability with highly agile beam steering and electronic beam stabilisation. SSR is another important sensor used to detect aircraft, identify friends or foes while working in tandem with the PR.
In addition, Netra is equipped with indigenous RWR-ESM-SPS integrated system. RWR uses wideband multi-bit digital receivers to obtain high probability of intercept while highly sensitive narrowband multi-bit digital receivers are used for ESM. RWR-ESM combine accurately finds direction of emitters leading to their accurate localisation. The ESM also identifies the type of fighter aircraft detected by the PR based on their radar emissions. MAWS provides spherical coverage around the entire aircraft for autonomous detection and tracking of missile threats and displaying real-time threat scenario in the cockpit. RWR-ESM and MAWS are integrated with CMDS for dispensing chaff and infra-red flares appropriately as per the detected threat.
Mission System fuses multi-sensor geometric, kinematics and attributes data of each target detected by PR, SSR, ESM and CSM to create a single track. Air Situation Picture (ASP) of the entire surveillance area is created by displaying all detected tracks simultaneously in real-time on a powerful and ergonomically designed HMI on all OWS for better situation awareness and quick decision making. The system simultaneously identifies and classifies all detected airborne targets and ships, tracks assigned targets and provides automatic threat evaluation on the ASP. LoS and satellite data-links are used to integrate and exchange data in real-time with ground-based Integrated Air Command & Control System (IACCS) of IAF to ensure common ASP both on the ground and on-board Netra.
Operators’ Cabin in Netra has indigenously developed Operator Work Stations (OWS) and communication system. Intercept Control & Battle Management (IC&BM) tools help operators to very effectively control fighter aircraft to attain and sustain air-superiority in contested airspace. IC&BM enables advanced threat evaluation, weapon assignment, intercept control, air-battle management, guidance and recovery. The voluminous data received through various sensors are presented to operators in easy to interpret formats like symbols, textual windows, histograms, spectrum display, waterfall display etc., which improves efficiency and minimises reaction time. The OWS supports multiple projection and coordinate systems with option to select various map layers on the display. Audio interface on the OWS enables operators to access all communication channels and data-links with press of a button while controlling networked fighter aircraft or interacting with IACCS. Two distinct playback modes provide tools to analyse entire mission data and also conduct post-mission debrief.
Embraer-145 aircraft modified for Netra flew its 1st sortie on 6th December 2011 in Brazil. Following this the aircraft was ferried to India in August 2012 and the mission systems developed by DRDO labs along with industries were installed and integrated on the aircraft. Thereafter, extensive development trials and flight testing of the mission systems was carried out jointly by designers and test-crew of CABS and IAF in over 1,000 sorties. Flight tests were conducted over all types of terrain spread across most parts of India wherein 64% of the testing effort was devoted only towards validating the performance of mission systems. Embraer-145, the Netra platform, was also modified for Air-to-Air Refuelling (AAR) and in the process AAR sorties were flown by a transport aircraft for the very first time in India. Performance of all active and passive sensors were evaluated and validated in IAF exercises involving large number of aircraft during large force engagement missions before induction of Netra in IAF.
Netra participated in the Republic Day Fly-Past for the 1st time on 26th January 2017. On 14th February 2017, Hon’ble Defence Minister late Shri Manohar Parrikar handed over the key of 1st indigenous AEW&C aircraft to the Chief of the Air Staff in a ceremony held in Aero India Exhibition in Bengaluru. In pursuant to its mandate CABS has successfully delivered ‘Netra’ AEW&C Systems to IAF, which are being operated extensively by IAF.
CABS has also successfully developed various mission support systems required on the ground to ensure seamless operations of a complex system-of-systems like the AEW&C system. A Mission Parameters Library containing technical and operational data for all onboard systems is prepared before missions in the Mission Planning & Analysis Station (MIPAS) and uploaded in the AEW&C system. During mission, AEW&C system records all data and videos generated by all its sensors, communication and navigation systems. After mission, MIPAS is used to download, playback, analyse all recorded data and videos, and generate Mission Report on basis of data collated by the AEW&C system. Ground Exploitation Station (GES) has been developed to provide communication interface between the AEW&C system while flying and the IACCS on ground to enable real-time exchange and dissemination of tactical information and decisions. Operator Training Station (OTS) has been developed to provide simulated environment for tactical training, C2 functions, air-battle management and behaviour of airborne sensors in dynamically changing combat scenarios in a very realistic manner. OTS has options to either train on simulated scenarios based on computer generated friendly and enemy forces or on mission scenarios recorded during actual missions flown earlier. AEW&C system is very software intensive platform; accordingly, a Mission Software Support Facility (MSSF) has been developed for software maintenance and configuration management of all software of the system.
The journey to this achievement was arduous and eventful as the AEW&C programme went through several moments of excitement and despairs, ups and downs. The design teams at CABS, DRDO labs at Electronic & Radar Development Establishment (LRDE), Defence Electronic Research Laboratory (DLRL), Defence Electronics Application Laboratory (DEAL) and Defence Avionics Research Establishment (DARE) ably supported by IAF Project Team at CABS, Centre for Military Airworthiness & Certification (CEMILAC), Directorate General of Aeronautical Quality Assurance (DGAQA), DRDO HQ, Air HQ, Aircraft & Systems Testing Establishment (ASTE) and squadrons of IAF, etc. worked closely along with Indian industries to catapult India into the select league of seven nations along with USA, Russia, Israel, Sweden, Brazil and China that have successfully designed and developed airborne surveillance platforms.
CABS is now well poised to take a large leap in sustaining the effort towards developing airborne surveillance systems not only for IAF but also for other agencies. The design capability and expertise gained during the AEW&C programme makes DRDO very confident of undertaking D&D of next-generation airborne surveillance systems consisting of contemporary AWACS/AEW&C systems, maritime patrol/reconnaissance aircraft and aircraft equipped with Synthetic Aperture Radar for intelligence gathering, surveillance, reconnaissance and targeting of enemy ground forces in battlefield. Cabinet Committee on Security (CCS) has recently approved a project for DRDO to develop more AEW&C systems for IAF.
AEW&C Programme has helped the country achieve full self-sufficiency in all the systems, technologies and software except for the aircraft platform. Based on the success of the AEW&C Programme, it has been decided to henceforth design and develop all airborne surveillance systems indigenously. AEW&C programme has paved the way for complete self-reliance and made India ‘Atmanirbhar’ in airborne surveillance systems.