India’s Defence Research and Development Organisation (DRDO) has successfully completed the integration and testing of its Surface Wave Over-The-Horizon Radar (SWOTH-Radar) system, marking a significant milestone in the country’s indigenous radar initiative. This advanced radar system is designed to overcome the limitations of conventional line-of-sight surface radars by detecting and tracking maritime and low-flying aerial targets up to 500 kilometres away.
The SWOTH-Radar utilizes high-frequency (HF) surface wave propagation, allowing electromagnetic waves to ride along the conductive surface of the sea. This method enables the radar signal to follow the Earth’s curvature, extending its range beyond the optical horizon—a capability that standard radars struggle to achieve. The system employs a bi-static configuration, with separate coastal sites for the transmitter and receiver, enhancing detection sensitivity and reducing interference.
According to DRDO, the system can cover targets up to about 500 km away. One of the most striking claims is that SWOTH-Radar can detect stealthy vessels or aircraft—those typically designed to minimise radar cross-section—owing to the longer wave propagation and advanced signal processing. The system is also said to be resilient to adverse weather and electronic counter-measures, making it suitable for persistent maritime domain awareness.
The DRDO SWOTH system reflects two important trends: the push for beyond-horizon sensing and the drive for indigenous technological capability. As adversaries adopt low-observable platforms, conventional radars’ horizon limitations become increasingly problematic. Technologies that circumvent horizon effects, such as surface-wave, space-based, and passive radars, are gaining traction. India’s push for indigenous advanced sensors across maritime, air, and land domains aligns with national security strategy and technological self-reliance.
In the maritime domain, achieving persistent, all-weather, wide-area surveillance is a game-changer. With SWOTH-Radar, India is aiming for a sensor that can “see” beyond the immediate littoral zone, maintain continuity without depending solely on airborne or space assets, and provide advanced warning. This could reshape how maritime operations are planned, deterrence postures maintained, and security architectures configured.
Strategically, this places India in a stronger position in the maritime domain, especially in the Indian Ocean Region (IOR). The system bridges the gap between shorter-range coastal radars and airborne early warning systems (AEW & C), but with potentially lower operating costs and fewer vulnerabilities.
The extended surveillance footprint allows India to observe vessels, submarines’ periscopes, or low-flying aircraft well beyond the coastal belt. This capability is crucial for monitoring inbound traffic, potential intruders, or threats before they approach closer. The system adds a layer of detection that may complicate adversaries’ plans to operate without detection, enhancing India’s ability to protect its sea lanes of communication (SLOCs), which are vital for trade, energy, and strategic projection.
As a domestically developed technology by DRDO, the SWOTH-Radar aligns with the “Make in India” and strategic autonomy goals, reducing reliance on foreign imports or platform dependencies. Compared to expensive airborne platforms or satellites, a surface-wave over-the-horizon coastal radar may offer persistent coverage at lower lifetime operating costs and less vulnerability.
While the announcement is promising, some typical challenges for such systems include environmental conditions, clutter and signal processing, baseline and infrastructure, integration with networked systems, and counter-countermeasures. Surface-wave propagation over sea surfaces can be influenced by sea-state, salinity, temperature gradients, and other environmental factors. Distinguishing actual targets from sea-surface clutter and managing false alarms require sophisticated signal processing and filtering. The bi-static configuration requires well-placed transmitter and receiver coastal sites, with reliable communications and data linking. For full strategic value, the radar’s data must be integrated with naval command & control, maritime domain awareness networks, and other sensors.
In the broader Indo-Pacific maritime context, India’s implementation of SWOTH-Radar sends multiple signals. To adversaries and sub-regional navies, it indicates that India is enhancing its capability to detect and monitor beyond its immediate littoral zone, raising the threshold for any stealthy approach. To friendly navies and partners, the capability may facilitate shared maritime domain awareness, particularly in the IOR and adjoining waters. In strategic competition, as surface-wave over-the-horizon radar is relatively rare, this gives India a technological edge and opens avenues for maritime surveillance exports or partnerships in the future.
With integration and testing complete, the next steps for the DRDO system likely include extended trials in operational maritime scenarios, activating transmitter-receiver pairs at selected coastal locations along India’s long coastline, and linking SWOTH-Radar feeds into the Indian Navy’s and Coast Guard’s maritime picture. Future enhancements may include higher frequencies, better target discrimination, and export versions for partner nations.
The successful development and deployment of the SWOTH-Radar system not only bolster India