Modern armies are spread across continents, oceans and deserts — far beyond the reach of any radio tower. When a naval task force in the Indian Ocean needs orders from headquarters, or troops on a remote border outpost must report back, the signal has to travel thousands of kilometres in seconds. The answer is military satellite communications, or SATCOM: specialised spacecraft that act as relay towers in orbit, carrying the encrypted voice, video and data traffic on which modern warfare runs. This explainer unpacks how the system works, from orbits and frequencies to India’s own military satellites.

The relay in the sky

At its core, a SATCOM link is a simple idea executed with extraordinary engineering. A ground unit — a ship, an aircraft, a vehicle-mounted dish or even a man-portable terminal — transmits a signal upward on what engineers call the uplink frequency. The satellite receives it, amplifies it, shifts it to a different downlink frequency, and beams it back to Earth, where a receiving terminal picks it up. A typical operational link involves one satellite and two earth terminals, and the whole transaction takes a fraction of a second.

Military satellites differ from their commercial cousins in almost every respect that matters in a war zone. They are hardened against radiation and electronic interference, carry built-in encryption modules, and are designed to keep working when an adversary is actively trying to jam or intercept them. The ground terminals are equally specialised: auto-tracking antennas that stay locked onto a moving satellite, and software-defined radios that can be reconfigured in the field to talk to different satellite networks.

Picking an orbit: GEO, MEO and LEO

Where a satellite sits determines what it can do. Geostationary (GEO) satellites park roughly 36,000 kilometres above the equator and appear fixed in the sky, giving continuous coverage over a large region — ideal for headquarters and fixed installations, though the distance introduces noticeable signal delay. Medium and low Earth orbit (MEO and LEO) satellites fly much closer and move relative to the ground, so they must be flown as constellations that hand signals off from one spacecraft to the next; the payoff is far lower latency, which matters for real-time video and fast-moving operations.

Orbit choice is also a resilience decision. A single geostationary satellite is a fixed point in the sky — if it fails or is disabled, its communication link goes with it. A constellation of moving satellites offers redundancy: traffic can be rerouted across multiple spacecraft. That logic is driving modernisation programmes such as the US Marine Corps’ effort to supplement legacy geostationary links with proliferated constellations, on the argument that no single satellite should be a single point of failure.

Spectrum as a weapon: from UHF to EHF

Military SATCOM does not use one frequency band but a whole ladder of them, and picking the right rung is a warfighting decision. At the lower end, ultra-high frequency (UHF) narrowband links penetrate foliage and bad weather and work with small, simple antennas — excellent for troops on the move — but they are the easiest to jam and carry the least data. Wideband systems in the super-high frequency (SHF) range, such as the US Wideband Global SATCOM (WGS) constellation, deliver high data rates for video and large file transfers, though they are more vulnerable to jamming and rain fade. The X-band is widely favoured for command-and-control links because it resists interference while carrying heavy traffic.

At the top of the ladder sits extremely high frequency (EHF) — systems such as Milstar and the Advanced Extremely High Frequency (AEHF) constellation — which provide jam-resistant, low-probability-of-intercept links for strategic command and control, including communications that must survive a nuclear environment. The trade-off is steep: EHF offers the lowest data rates of all the bands.

India’s constellation: Rukmini, Angry Bird and beyond

India has been building its own military space backbone for over a decade. The first dedicated military satellite was GSAT-7, nicknamed Rukmini, launched in 2013 for the Indian Navy. With its ultra-high frequency transponders, it gave the Navy secure links to ships, aircraft and even submerged submarines across the Indian Ocean Region — capabilities previously dependent on foreign systems.

It was followed in December 2018 by GSAT-7A, known as “Angry Bird,” which serves the Indian Air Force and supports satellite-controlled operations of unmanned aerial vehicles, with the Army drawing on some of its transponders as well. The Army’s own dedicated satellite, GSAT-7B, moved forward when the Defence Ministry signed an approximately ₹3,000-crore contract (about $365 million) with NewSpace India Limited — the first spacecraft of its own for the Army, designed to provide mission-critical beyond-line-of-sight communication to troops, air-defence weapons and remotely piloted aircraft, with handover reportedly expected by 2026.

The Navy, meanwhile, received its next-generation spacecraft in November 2025, when ISRO’s heavy-lift LVM3 rocket launched GSAT-7R (also designated CMS-03). Weighing about 4.4 tonnes, it is the heaviest communication satellite ever launched to orbit from Indian soil, operates across UHF, S, C and Ku bands, and is designed to replace the ageing GSAT-7 with a 12-to-15-year operational life. Together, the constellation underpins network-centric warfare: ships, aircraft, sensors and command centres fused into a single, encrypted communication grid across the Indian Ocean Region.

The contested spectrum

None of this works unopposed. Adversaries jam uplinks, spoof signals and probe ground networks for intrusions — which is why military SATCOM layers encryption, frequency-hopping, anti-jam waveforms and cyber defences on top of the physics. “SATCOM on the move” — antennas that hold a satellite lock while a vehicle drives, a ship rolls or an aircraft banks — has become a procurement priority precisely because static communications die first in a real fight.

The direction of travel is clear: more satellites, lower orbits, heavier encryption, and a deliberate blending of military and commercial capacity. In any future conflict, the side that keeps its relays alive while blinding the enemy’s will hold a decisive advantage.

FAQs

What is military SATCOM?
SATCOM — satellite communications — uses spacecraft as relays between ground terminals. A unit transmits on an uplink frequency, the satellite amplifies and retransmits the signal on a downlink frequency, and the receiving terminal picks it up. Military versions add hardening, encryption and anti-jamming protection.

Why do armies need satellites at all?
Radio waves travel in straight lines and cannot bend over the horizon, so terrestrial radios are limited to line-of-sight ranges. Satellites can relay signals across continents and oceans in fractions of a second — the only practical way to command dispersed forces, ships at sea and aircraft in flight.

Which satellites does India use for defence communications?
India’s dedicated military communication satellites include GSAT-7 (Rukmini, Navy, 2013), GSAT-7A (Air Force, 2018) and GSAT-7R (Navy, launched November 2025), with an Army-dedicated GSAT-7B under a roughly ₹3,000-crore contract.

Compiled by the Khabar 24h Editorial Desk from publicly available sources.