Ground vs. Air Sensing: India’s Multi-Domain Defence Strategy

Sensing systems that generate information and situational awareness are foundational to national security architecture. This paper examines the strategic, operational, and technological calculus between ground-based sensing systems (GBSS) and airborne sensing platforms (ASP), incorporating emerging space-based and unmanned capabilities. Drawing on NATO doctrine, U.S. Congressional and CSIS studies, DRDO programmes, and parliamentary disclosures, it finds that no single sensing domain suffices in isolation. The global trend favours a multi-domain, layered, AI-fused sensing architecture. For India—geographically vast, flanked by two nuclear-armed adversaries, and technologically aspirational—the imperative is not a binary choice but a calibrated, phased strategy that closes airborne deficits, modernises ground sensor networks, deepens space-based ISR, and builds the indigenous fusion backbone needed for credible deterrence.

1. The Sensing Imperative

Modern conflict is decided less by kinetic mass than by the speed, depth, and accuracy of situational awareness that enables its application. Battlefield decision timelines have compressed from hours to minutes. Intelligence, Surveillance, and Reconnaissance (ISR) is the engine of this transformation: a nation that “sees” comprehensively across land, sea, air, space, and cyberspace holds a decisive edge in the Observe-Orient-Decide-Act (OODA) loop. The choice between ground and air-based sensing is therefore not a procurement detail but an expression of strategic philosophy. This paper offers an evidence-based comparison of sensing architectures, maps global trends—including the accelerating shift toward space-based sensing—and charts an actionable path for India at a critical juncture of defence modernisation. Sensing is treated here not as a discrete technology choice but as the connective tissue of deterrence: the sensor that detects, the network that transmits, and the algorithm that interprets are collectively what convert raw information into decision advantage. Where a nation places its investment across these layers—and how well it fuses them—increasingly determines whether it can act inside an adversary’s decision cycle or is destined to react to it.

2. The Two Architectures

Ground-Based Sensing Systems (GBSS)—fixed and mobile surveillance radars, acoustic sensors, electro-optical/infrared towers, seismic arrays, and ELINT receivers—form the foundational layer of national defence. U.S. Army doctrine on Multi-Domain Sensing recognises ground ISR as essential for offering persistent, terrain-specific coverage without the logistical burden of aircraft. The most transformative recent shift is toward proliferated, passive sensor networks. A 2025 CSIS study concluded that replacing a small number of large, emitting radars with a networked layer of smaller passive sensors could substantially improve air and missile defence resilience, since passive sensors are inherently harder to detect and target. Ukraine’s “Sky Fortress” network of acoustic microphones and passive radio receivers, and the U.S. Army’s Long-Range Persistent Surveillance (ALPS) system, exemplify this paradigm.

GBSS strengths include persistent 24/7 coverage without crew fatigue, lower recurring costs, survivability in A2/AD environments (passive variants), immunity from being “shot down,” and easy integration with fixed C2 infrastructure. Its limitations are equally real: terrain masking restricts range, fixed installations (especially large active radars) are vulnerable to precision strike, systems cannot dynamically reposition, low-altitude/stealthy threats remain challenging, and deployment logistics in mountainous or jungle terrain are complex.

Air-Based Sensing Platforms (ASP)—AWACS, Maritime Patrol Aircraft, High-Altitude Long-Endurance (HALE) UAVs, and tactical drones—offer the greatest operational flexibility, since altitude dramatically extends the radar horizon. A 2025 Carte Nav industry survey documents the proliferation of multi-mode airborne surveillance combining SAR, GMTI/AMTI, SIGINT, and EO/IR sensors into platforms of remarkable versatility. NATO’s Alliance Ground Surveillance (AGS), operational since 2012, demonstrated the value of persistent airborne surveillance in all weather; its successor, the Allied Future Surveillance and Control (AFSC) framework, envisions a blended crewed–uncrewed network. UAVs have become the preferred tactical ISR tool, combining long endurance, secure links, and multi-spectral sensors without risking aircrew.

ASP strengths include massive area coverage (a single AWACS monitors 400+ km continuously), rapid repositioning across theatres, real-time battle management, long-endurance UAV variants at lower cost than manned aircraft, and multi-mission payload flexibility. Limitations are significant: high vulnerability in contested A2/AD environments (China’s long-range air-to-air missiles now threaten even high-value platforms), extreme lifecycle costs (a single AWACS programme can exceed $2 billion), crew fatigue and maintenance-driven coverage gaps, dependence on uncontested airspace, and disproportionate intelligence loss if a single platform is downed.

3. Comparative Assessment

(Author’s assessment, 2026)

Deduction: No domain dominates across all parameters—the case for a layered architecture is embedded in the comparison itself.

4. Global Trends: Convergence toward Multi-Domain Sensing

The space-based revolution is the most consequential trend. In 2025 the U.S. Department of Defence proposed cancelling further procurement of the Boeing E-7A Wedgetail (a programme exceeding $2.56 billion) in favour of space-based sensor constellations, citing both cost/schedule overruns and survivability concerns as Chinese long-range air-to-air missiles increasingly threaten high-altitude airborne assets. The U.S. Space Development Agency is investing roughly $88 million in space-based moving-target-indication (AMTI) research, with operational capability projected for the early 2030s—a mission once considered achievable only from crewed aircraft. Commercial constellations reinforce this shift: Spire Global’s LEO satellites, using software-defined-radio payloads, now deliver near-real-time aircraft tracking and GNSS interference detection that once required dedicated military assets.

The passive sensor network paradigm is transforming ground-based sensing in parallel. The 2025 CSIS study proposes a hybrid architecture combining passive multistatic radar, passive RF detection, acoustic arrays, and EO/IR networks into an integrated mesh. A notional 400-sensor passive EO/IR network modelled over Poland (chosen for Indo-Pacific relevance) matched current active-radar coverage at a far lower electronic signature (sensors that do not emit are sensors that survive).

Unmanned systems have democratised ISR. Ukraine has shown that platforms costing thousands of dollars now perform missions once requiring systems worth millions. The UK Ministry of Defence’s 2025 framework integrating aerial drones, ground rovers, and fixed sensors into a single “integrated reconnaissance ecosystem” reflects the operational future: not separate systems but one interconnected intelligence fabric. General Atomics’ offer of an MQ-9B configured for Airborne Early Warning is emblematic—combining HALE persistence, radar early warning, and low per-flight cost in a configuration that blurs the ground-ISR/air-ISR boundary.

AI and data fusion are the multiplier. The U.S. requested over $3.3 billion for defence AI in FY2025, much of it for ISR applications. U.S. Air Force Doctrine Note 25-1 (April 2025) envisions AI-networked sensors identifying threats without prior signatures, processing data at machine speed, and coordinating autonomous swarms. Multi-intelligence cross-domain fusion, combining EO, SAR, IR, SIGINT, and ELINT through multimodal AI, is dissolving the traditional distinction between platform types: the operative question shifts from “which platform” to “which data.” The Joint All-Domain Command and Control (JADC2) concept codifies this: the future ISR enterprise aims to fuse multi-domain data rapidly into decisive information advantage.

5. China–Pakistan Sensing Collaboration

China and Pakistan operate one of the most tightly coupled sensing partnerships in the Indo-Pacific/South Asian theatre. China’s ground radar network spans over 400 known sites across twelve bases, feeding a roughly $6 billion domestic military radar market; satellite imagery of 434 sites shows 40 percent with recent upgrade activity, including new stealth-penetrating meter-wave AESA sites near Fujian, Hainan, and Subi Reef. Pakistan’s radar inventory (YLC-2, YLC-6, YLC-18, JY-27A, DWL002) is almost entirely Chinese-supplied, making Islamabad one of Beijing’s largest radar-export recipients.

In the air, China operates three AEW&C generations, culminating in the KJ-500 (360° coverage, 720 km detection), with a next-generation “KJ-3000” reportedly under development. Pakistan operates nine Swedish Erieye aircraft—nominally more than India’s five-platform fleet—plus four Chinese ZDK-03s, many of which were pushed into electronic-warfare roles after integration problems. Operation Sindoor (May 2025), the four-day India–Pakistan exchange, delivered the sharpest real-world test: India’s destruction of a Pakistani AWACS underscored both the value and the vulnerability of airborne early warning once engaged.

The space layer is the fastest-moving and least transparent element of the partnership. China’s Yaogan, Gaofen, and BeiDou constellations, together with the world’s only geostationary SAR satellite, give Beijing persistent regional ISR; BeiDou access has been extended to Pakistan since 2018. Pakistan’s SUPARCO, which had only fifteen launches between 1961 and 2024, launched six Earth-observation satellites between January 2025 and June 2026—40 percent of its entire launch history in sixteen months, almost entirely on Chinese rockets. These are tuned for South Asian repeat coverage, with one satellite’s unusual 38° inclined orbit sacrificing global reach for near-daily revisits over the India–Pakistan–Kashmir band, imaging Indian territory roughly every two days. This surge unfortunately coincides with Indian setbacks (EOS-N1, EOS-09, and NVS-02 failures across 2025–26), raising concern that ISRO’s strategic-satellite programme may be falling behind.

In the unmanned domain, China’s WZ-7 “Soaring Dragon” HALE drone has operated near Tibet along the Indian border since December 2022, and radar payloads are increasingly migrating onto unmanned platforms. Pakistan fields one of the world’s largest UAV inventories outside the US/UK/Israel, but Operation Sindoor exposed a wide gap between declared numbers and demonstrated performance: most of an estimated 300–400 Turkish drones deployed were neutralised by India’s layered air defences.

Three deductions emerge: Pakistan’s ground and air sensing remain substantially dependent on China, which confers leverage but also creates integration problems; the space layer has closed, in months, a capability gap that would normally take a decade, with orbital geometry specifically tuned to South Asian revisit needs; lastly inventory size is a poor proxy for capability, as Pakistan’s large but multi-source UAV fleet underperformed in its only significant combat test. For India, the central challenge is no longer counting adversary radars, aircraft, and satellites, but tracking the pace and quality of the integration binding them into a single targeting picture—a pace that is currently outrunning India’s own strategic-satellite capacities.

6. India’s Strategic Position

India’s sensing requirements are shaped arguably by the world’s most demanding security environment: 15,106 km of land border across mountain, riverine, jungle, desert, and coastal terrain, facing two nuclear-armed neighbours with unresolved territorial disputes and a history of kinetic engagement.

(Sources: Parliamentary Standing Committee on Defence Report, March 2025; Tribune India; DRDO AEW&CS disclosures)

The airborne deficit is India’s most critical vulnerability. The IAF has formally sought 12 additional AEW&C aircraft. Two six-aircraft programmes are underway: the Netra Mk.2, retrofitting six ex-Air India A321s with DRDO/Airbus-developed AESA radar (Rs 19,000 crore/$2.2 billion, cleared July 2025, first delivery 2026–27, completion 2033–34, with Adani Defence & Aerospace as industry partner); and the Embraer ERJ-145 AEW&C Mk.1A with Gallium Nitride AESA radar (cleared December 2025, acquisition not yet started). A July 2024 RFI seeks six large 360°-coverage AWACS with 8-hour endurance and aerial refuelling. General Atomics’ proposed MQ-9B-AEW variant, building on India’s $3 billion, 31-aircraft MQ-9B procurement, offers a lower-cost, zero-aircrew-risk supplement to these manned programmes.

Ground-based sensing is advancing through the Comprehensive Integrated Border Management System (CIBMS), which fuses manpower, sensors, communications, and command control for real-time threat detection. The 2025–26 budget allocated Rs 5,597 crore for border infrastructure, a nearly 50 percent increase. The India–Pakistan and India–Bangladesh borders are most advanced, with a four-year plan (announced April 2025) for full electronic coverage of the Pakistan border. The China-LAC and Myanmar border remain far behind due to terrain and diplomatic sensitivities, though Rs 30,000 crore ($3.4 billion) is being invested in 500 km of dual-use Northeast railway infrastructure.

Space-based ISR is India’s emerging strength but remains thin. RISAT provides all-weather SAR, Cartosat high-resolution optical imagery, and EMISAT electronic intelligence, now operationalised under the Defence Space Agency. However, constellation density is insufficient for persistent coverage, and India lacks any space-based GMTI/AMTI capability—a gap that persists even in the United States. A proposed 52-satellite ISR constellation, if realised, would be transformative.

7. The False Binary

A recurring analytical error is to treat ground- and air-based sensing as competing alternatives. NATO doctrine, U.S. Congressional research, Chinese sensing analysis, and battlefield evidence from Ukraine and the Middle East converge on the opposite conclusion: these are complementary architectures, each covering the other’s blind spots. Ground systems offer persistence but limited reach; air systems offer reach but cost and vulnerability; space systems offer global coverage but latency and immature AMTI capability. The validated model—reflected in NATO’s AFSC, the U.S. JADC2 concept, and the UK’s integrated reconnaissance ecosystem—is a layered, networked, AI-fused sensing fabric in which every platform contributes to a common operational picture. For India, the question is not “ground or air” but how to build a networked, multi-domain, AI-enabled architecture calibrated to its threat environment and indigenous development timelines.

Five investment priorities are suggested—

a. First, close the airborne gap within five years: India’s five operational AEW&C platforms against a combined Chinese–Pakistani total exceeding 40 represents the most acute and irreversible asymmetry, demanding expedited Netra Mk. 2 deliveries, accelerated large-AWACS procurement, and serious evaluation of the MQ-9B-AEW.

b. Second, complete CIBMS and extend it to the LAC over three to seven years, replacing today’s patchwork with a terrain-adapted mesh of acoustic, seismic, EO/IR, and radar sensors.

c. Third, build an indigenous space ISR constellation over seven to fifteen years, prioritising SAR persistence, ELINT, and eventual GMTI, given technology-transfer restrictions on space sensing.

d. Fourth, build AI fusion and JADC2 architecture concurrently across all timelines, without which multi-domain investment produces data silos rather than a unified picture.

e. Fifth, invest in drone swarms and autonomous ISR over five to ten years, drawing on Ukraine’s demonstration of low-cost, expendable, swarm-capable platforms.

8. Way Forward: Policy Recommendations

Structural reforms: establish a National Sensing Architecture Directorate under the Chief of Defence Staff to coordinate multi-domain investment and eliminate inter-service duplication; create a ring-fenced ISR budget line of at least 15 percent of capital procurement; and mandate technology transfer and joint ventures on major sensing acquisitions to build indigenous capacity.

Near-term priorities (2026–2030): fast-track Netra Mk.2 with independent project oversight to avoid the delays that have historically plagued DRDO AWACS programmes; finalise large-AWACS procurement before 2028 with binding delivery timelines; induct the MQ-9B fleet on priority and evaluate the AEW variant; and complete CIBMS on the Pakistan border by 2029 before accelerating LAC deployment.

Medium-to-long-term investments (2030–2040): launch the first phase of an indigenous SAR ISR constellation (6–8 satellites by 2032); establish a National JADC2 Centre fusing space, air, ground, and maritime feeds into a real-time common operational picture; invest in quantum sensing (magnetic anomaly and gravitational detection) for submarine and underground facility detection; and develop indigenous HALE UAV capability to reduce dependence on foreign platforms. None of these investments will yield the intended deterrent effect in isolation; their value is multiplicative only when bound together by common data standards, interoperable communications architecture, and a doctrine that treats every sensor — however small or however costly — as a contributor to a single national operational picture rather than a service-specific asset.

9. Conclusion

A critical component of national security is the future of sensing. The nation that achieves persistent, multi-domain, AI-enabled awareness across land, sea, air, space, and the electromagnetic spectrum holds a decisive advantage in both deterrence and warfighting. The global evidence is unambiguous: leading military powers are fusing passive ground sensor meshes, crewed and increasingly autonomous airborne platforms, and space-based constellations into a single intelligence fabric. The question of ‘ground or air?’ is now strategically obsolete.

For India, the challenge is acute and urgent. An airborne early warning deficit of five platforms against a combined regional total exceeding forty is the most dangerous immediate gap; ground-based border sensing remains incomplete, particularly on the LAC; and the space-based ISR constellation is insufficient for persistent national security coverage. The path forward is architecturally clear though politically and bureaucratically demanding: close the airborne gap with speed and indigenous ambition, complete the ground sensor mesh with priority to the LAC, build the space-based constellation with determination, and weave every domain together through an AI-powered, interoperable JADC2 backbone. India’s strategic culture, technological base, and increasingly credible defence industry make this achievable—provided national will and investment are sustained. The most dangerous sensor gap is the one discovered only after it is exploited. India cannot afford to find out.