The F-35 Lightning II is a single-seat, single-engine stealth aircraft used by multiple branches of the US armed forces and many allied nations around the world. Developed to operate as a multi-role strike fighter, it is highly capable of both air superiority and ground strike.

To achieve all of this, the F-35 integrates several advanced sensor systems, one of which is the Electro-Optical Targeting System (EOTS). This sensor merges forward-looking infrared (FLIR) and infrared search and track (IRST) functionality into one unit.

According to Lockheed Martin’s description: “Through EOTS, pilots have access to high-resolution imagery, automatic tracking, IRST, laser designation and rangefinding, and laser spot tracking at greatly increased standoff ranges.”

EOTS offers infrared imaging for detecting and tracking targets, laser designation for guiding precision munitions, and various other features to reduce pilot workload without adding external pods or large protrusions to the jet.

The EOTS supports both air-to-air and air-to-ground targeting while being contained within a low-drag and stealth-friendly enclosure. Its sapphire window shields the system from harsh flight conditions, allowing optical signals to pass through efficiently.

The US Air Force, US Navy, US Marines and 19 other countries operate the F-35 A, B and C models with more interested countries still considering procuring it as well.

Distributed Aperture System (DAS)

EOTS does not function alone on the F-35. The DAS includes six infrared cameras placed around the aircraft, providing a 360-degree view. These cameras feed imagery to the pilot’s helmet display, effectively allowing the pilot to see “through” the aircraft. The transparent windows for these cameras must preserve low-observable qualities.

According to Lockheed Martin's webpage, “Our goal was to hit an average of 88 DAS window panels a month, and we surpassed that mark by eight percent,” said Brett Rolston, director of the F-35 Sensors program at Lockheed Martin’s Missiles and Fire Control. The production of these windows undergoes strict tolerances to ensure optical clarity and stealth characteristics.

As the number of F-35 aircraft grows worldwide, the demand for both new and replacement DAS windows rises. Dedicated engineering teams have automated key portions of the production process, such as initial metal frame machining and painting, to keep pace with the required output. These steps have trimmed the cost of DAS windows by about 80% over the course of the program.

DAS and EOTS each uniquely enhance awareness of air and ground threats. DAS is responsible for a broad situational picture around the aircraft, while EOTS focuses on precise targeting. The synergy comes when EOTS designations feed into the mission computer, and the pilot can see the broader threat environment on the helmet display provided by DAS.

Pilots rely on EOTS for situational awareness in complex battle spaces. EOTS produces infrared imagery that detects and locks onto targets, even in low-visibility conditions. The laser designation function guides weapons like Paveway-series bombs or laser-guided Joint Direct Attack Munitions (JDAMs). The IRST aspect allows the pilot to detect and track enemy aircraft through thermal signatures, complementing the F-35’s other radar and sensor suites.

The system’s tight integration with the F-35’s mission computer means that it does not operate in isolation. Information from the EOTS feeds into the aircraft’s mission systems, where data is fused from other sensors such as the AN/APG-81 radar, the DAS, and communication links. The pilot’s helmet-mounted display receives these fused signals, enabling rapid decisions without scanning separate screens.

The rundown

As Lockheed Martin states, the F-35 EOTS features the following capabilities and specifications:

• High-performance sensors: FLIR and IRST combined
• Modular design for two-level maintenance: reduces lifecycle cost
• Automatic boresight: ensures quick alignment with aircraft systems
• Tactical and eye-safe laser: Class 4, 1.06 µm wavelength
• Laser spot tracker: detects externally designated targets
• Passive and active ranging: supports varied combat scenarios
• Guidance for laser weapons: immediate integration with common laser munitions
• Coordinate generation for GPS: direct input to F-35 avionics
• Rugged, faceted window: 2 in (5.08 cm) thickness for low-observable performance
• Single aperture design: 10 in (25.4 cm) width
• Lightweight design: 200 lb (90.7 kg) total system weight

Developing EOTS

The F-35 program, as a whole, has an overarching aim to balance high output volume and cost savings with consistent product quality, ensuring that each system in each aircraft is ready for the harshest conditions.

The team developing the EOTS achieved outstandingly low Defects Per Hour (DPH), improving the system’s reliability and driving down manufacturing costs. Fewer production defects translate directly into better affordability for operators.

The F-35 sensors program attributes these gains to dedicated teams spread across Lockheed Martin facilities and supply chain professionals who help uphold strict standards. Production data suggests that each incremental lot of EOTS has consistently met or exceeded all quality benchmarks with each successive lot.

According to a statement by Lockheed Martin, “Completing the 850th EOTS for the F-35 while achieving the highest stick rate we’ve seen represents a great accomplish by our team members who all share in the same mission of supporting our warfighters,” said Brett Rolston, director of the F-35 Sensors program.

This milestone underscores a production rate that has continued to accelerate. The remarkable stick rate exceeding 96% indicates that EOTS units integrate into the aircraft without requiring rework with nearly zero failures.

Cost reduction and efficiency

Developers expect total lifecycle cost savings to exceed $1 billion, partly due to improved reliability and simpler sustainment. As Lockheed Martin said in reference to cost improvement:

“We’re taking aggressive actions to ensure continued cost reduction and increased availability of our F-35 products,” said Brett Rolston, director of F-35 Sensors at Lockheed Martin Missiles and Fire Control. “With F-35 production increasing year after year, it is vital that we drive reliability improvements into the sensors while driving sustainment costs down to meet customer expectations.”

Additional steps, like upgrading depot test equipment configurations and expanding repair capabilities at F-35 service depots, are projected to further decrease the cost per flight hour. The overall objective is to approach or go below $25,000 per flight hour by 2025, an initiative that extends across several F-35 components.

Future developments

The Block 4 modernization program began in 2018 with the goal of integrating 75 new features onto the F-35 JSF. Lockheed Martin has already developed an advanced EOTS variant (A-EOTS) for the F-35 Lightning II.

This system provides higher resolution and improved multi-spectral sensing through a larger aperture and offers high-resolution Mid-Wave IR, Short-Wave IR, and Near IR. Retaining the same volume and weight, A-EOTS integrates seamlessly into the F-35 via a “plug and play” approach. The A-EOTS will be available to install with the Block 4 upgrade program.

EOTS data does not exist in a vacuum. The F-35’s mission computer fuses EOTS imagery with radar inputs, DAS feeds, and other sensor data. In addition to the synergy with onboard systems, EOTS can transmit target data to allied platforms through secure datalinks. This networked approach helps coordinate attacks, guiding ground forces or other aircraft to the same target.

Developers continue refining EOTS to support the F-35’s evolving mission profiles. Short-wave infrared imaging is a significant addition because it enables the sensor to detect targets under conditions limiting mid-wave or long-wave infrared. The new infrared marker helps coordinate with ground troops using specialized night-vision equipment, bridging the gap between airborne and ground-based operations.

Software-driven enhancements may include augmented image processing to identify subtle target signatures at greater distances. Machine learning algorithms could also assist in automatically classifying targets based on shape, motion patterns, or heat distribution.

Proposed sensor upgrades are anticipated with the F-35’s Block 4 update, which includes new weapons compatibility, improved data link, and expanded electronic warfare (EW) capabilities. The EOTS’s hardware has been engineered to accommodate these expansions with minimal physical changes.

“Block 4 upgrades add new and enhanced capabilities to ensure our platform remains relevant against rapidly evolving threats,” said Lt. Gen. Michael Schmidt, F-35 Program Executive Officer.

“Much like a new mobile cell phone or personal computer, TR-3 will host new Block 4 capabilities and applications with significantly more computing power and memory than the legacy infrastructure.”

The bottom line

The combined power of EOTS and systems like DAS, AN/APG-81 radar, and the F-35’s robust mission computer ensures that pilots have a comprehensive, high-quality battlespace picture. With a track record of more than 850 units delivered, combined with ongoing cost reductions, demonstrates the quality and value of the EOTS system to the F-35 program.

Anticipated upgrades, including short-wave infrared functionality and better resolution, will reinforce the F-35’s sensor advantage. EOTS remains a critical factor in the F-35’s ability to operate effectively against evolving threats.

According to the statement by Lockheed Martin, “The EOTS team continues to make strides in F-35 affordability,” said Bridget Lauderdale, vice president and general manager of the F-35 Program. “Since Low-Rate Initial Production 1, the EOTS team has reduced overall unit costs by 66%. I appreciate their focus on affordability and driving down costs.”

The ability that EOTS provides to the F-35 is vital to the JSF program. The US and its allies rely on the F-35 to be a vanguard or air power in the face of emerging threats, with deterrence through readiness and capability.