By Subodh Sharma and Aman Routray

The stealth fighters carry a unique type of sensor that allows them to target the enemy in a passive mode i.e without emitting any radiation. This further ensures the radar cross-section of the fighter jet does not get la-di-da. This unique sensor is called ETOS (Electro-Optical Targeting System) and it has found its way into American F35 Lightning II and Chinese J20 stealth fighter. Russians on other hand did not attempt this complex sensor for its Su57 stealth fighter.

What's the difference between the OLS-35 and the EOTS in terms of  capabilities and characteristics? - Quora
EOTS of F35
High-Quality Shots Of Unpainted Chinese J-20 Stealth Fighter Offer New  Capability Insights
EOTS of J20

India is currently developing its next-generation fighter jet, Advance Medium Combat Aircraft and we reported earlier (here), AMCA will have this gem of the sensor under its nose. ETOS combines Infrared Search and Track (IRST) and Forward-Looking Infrared (FLIR) in one console. It enhances pilots’ situational awareness and allows aircrews to identify areas of interest, perform reconnaissance and precisely deliver laser and GPS-guided weapons. Additionally, this console is packed in the stealthy durable sapphire window that will ensure the stealth characteristics remain intact.

The DRDO ETOS test bed

The latest indicators suggest “that” sensor which was exclusively reported by us in October 2021 is now ready. In order to test the performance, it will now be mounted on a DRDO testbed and flight trials will start soon. DRDO has invited vendors to modify the flying testbed to carry two sensors under the nose providing 180-degree coverage on either side. The placement scheme can be seen in Image below.

DRDO’s Proposed sensor placement on Flying testbed (Image from the DRDO document)

The electro-optical sensors will be placed at an angle of -45 degrees on both the forward and rear sides. This will allow the coverage area to be maximum and keep the drag penalty under check. The scheme is also shown in the document shared by the DRDO (screengrab in the image below)

Tasks up ahead
The developed sensors will now be integrated on a flying testbed which will require the removal of a rectangular panel underneath the nose. The data transfer will use fiber optic cable instead of regular metallic conductor-based wiring. The FO allows faster data transfer and thereby reduces the overall processing time and enhances the reaction time of the aircraft.
Once the flying testbed is modified, it will then be taken to the flight testing at various locations. As of now the high altitude and hot/cold weather testing isn’t part of the program but at later stages certainly, it will be tested in those conditions.
Aircraft will be flown at altitudes upto 25,000 ft in Bangalore, Chennai and Mangalore area. The flight test plan suggest, FTB will undergo flight testing in two phases. During the first phase, the aircraft will be conducting 1 hour sortie in Bangalore. The document suggests, during this phase in total 15 sorties will be conducted. Each of these sorties will last about one hour and pan out during morning, noon, evening and night. The objective of these sorties will be to test and capture background data in industrial environment and regular terrain.
During Phase two the aircraft will fly two different routes, one between Bangalore and Chennai and second one between Bangalore and Mangalore. These will be comparatively larger sortie with a duration of around 2.5 hours. They will also pan out during morning, noon, evening and night. The objective of these sorties will be to test and capture background data in industrial environment and sea environment.
The complete project has to be completed in the coming 3 months along with the flight trials. During first month the aircraft will be modified and this newly developed ETOS sensor will be mounted on the flying test bed. In subsequent one and half month time the modified flying test bed will conduct numerous sorties in skies of Bangalore, Chennai and Mangalore. Following the completion of the flight trials by end of two and half month the vendor will then remove the sensor from the flying test bed in another 15 days and hand over the Flying test bed to DRDO.
The premier lab of Defence Research and Development Organization (DRDO) which deals with the electrooptical sensor, Instrument Research and Development Establishment (IRDE) has developed these sensors. It was believed that lab was working with two private sector startups to realise two prototype units of these sensors for the testing, validation and certification. The design of the system was supplied by IRDE and these two private sector companies fabricated the prototypes for the testing. However it isn’t clear which company was was finally selected by IRDE for the realisation of the sensor but nevertheless the sensor is now realised and is ready for the integration and flight testing.

The IRDE EOTS will have five sensors packed in a single, compact housing.

Following are the sensors:
1. Thermal Imager, 
2. CCD Camera, 
3. Eye-safe Laser Range Finder, 
4. Laser Illuminators, and 
5. Beam Generator

These five sensors together will allow AMCA to detect, track and target enemy without using the RADAR. The EOTS will also allow the aircraft to perform the air to ground missions, reconnaissance and surveillance missions.  

The EOTS once integrated with the external systems like RADAR and Electro-Optical Distributed Aperture System (EO-DAS). This sensor fusion will make the AMCA more situationally aware and extremely effective.

By Alpha Defense

Alpha Defense initially a solo venture but now a defense group by people from various demographics of India covering defense news and updates. We believe in unbiased analysis of every subject in hand. Our mission is to provide simplfiied defense information to the public.