National SBAS: augmenting GNSS on your own terms

SBAS delivers sub-metre integrity and accuracy over your territory. Building it yourself means you set the coverage, the continuity rules, and the off-switch.

The dependence this ends: Dependence on foreign augmentation (WAAS, EGNOS) or none at all

The augmentation you rely on belongs to someone else

WAAS covers North America. EGNOS covers Europe. If your territory falls under neither, your aviation authority either accepts degraded approach minima or files exemptions. If it falls under one, you accept that the service level, the integrity broadcasts and the continuity commitments are set by a foreign agency with its own priorities. That is a reasonable arrangement in peacetime, with trusted partners, when cables stay intact. Recent years have tested all three assumptions.

The practical consequences are not abstract. Precision approach procedures to SBAS LPV minima (200-foot decision height, 40-metre lateral accuracy) require a certified SBAS signal. Without one, instrument approaches revert to older barometric minima, raising decision heights and reducing access in low visibility. For agricultural, survey and infrastructure users, the loss of a sub-metre integrity service simply means reverting to post-processed corrections from foreign commercial providers, with all the data-sovereignty questions that follow. A national SBAS closes both gaps under a single sovereign architecture.

What SBAS actually is, and what it is not

Satellite-based augmentation works by distributing integrity and differential correction data across a territory via geostationary broadcast. A network of precisely surveyed ground reference stations continuously measures GNSS pseudorange errors. A central processing facility computes wide-area corrections and, critically, integrity bounds: the system tells the aircraft not just 'here is a better position' but 'I guarantee the error does not exceed X, and if it does, I will alert you within six seconds'. That integrity guarantee is what unlocks precision approach procedures. The GEO satellite broadcasts this message on the GNSS L1 frequency, so any SBAS-capable receiver, including standard aviation avionics, picks it up without modification.

What SBAS does not do: it does not replace GNSS. It augments GPS, GLONASS, Galileo or NavIC signals; it does not generate ranging signals of its own. It also does not survive a complete GNSS outage. Jamming or spoofing of the underlying constellation degrades SBAS-corrected positions along with everything else. If the threat model includes deliberate GNSS denial, a separate resilient-timing or LEO-PNT layer is the appropriate complement. Those are covered elsewhere in this stack. SBAS is the right tool for integrity, accuracy and aviation certification, not for anti-jamming.

Precedents: MSAS, GAGAN and KASS set the cost and timeline envelope

Three programmes define the credible planning range. Japan's MSAS (Multi-functional Satellite Augmentation System) achieved initial operational capability in 2007, hosted on MTSAT geostationary satellites procured for meteorology, with a ground network across Japanese territory. India's GAGAN (GPS Aided GEO Augmented Navigation) reached full operational capability in 2015, using payload hosted on GSAT-8 and GSAT-10; the programme ran roughly a decade from inception and involved a ground network of fifteen reference stations. Korea's KASS (Korea Augmentation Satellite System) achieved operational service in 2023 on a dedicated GEO payload hosted on Korea's GEO-KOMPSAT-2F satellite, with a network of ground reference stations across the peninsula. All three are publicly documented programmes with national civil aviation authority certification.

These precedents suggest two broad scales. A pathfinder programme, covering a single national territory with a hosted GEO payload and a reference-station network of eight to twenty stations, sits in a cost class comparable to mid-scale national infrastructure projects: publicly reported SBAS-class programmes have ranged from low hundreds of millions upward depending on whether the GEO satellite is purpose-built or shared. A full sovereign programme adding a dedicated GEO satellite, redundant processing and a larger reference network scales accordingly. Neither figure should be taken from this page; the right starting point is a mission-architecture study that maps your territory, traffic density and existing ground infrastructure.

The ambition ladder: pathfinder to sovereign programme

The entry rung is a hosted payload. Your nation procures or arranges a SBAS payload on an existing or planned GEO satellite, builds a central processing facility, and deploys reference stations at surveyed sites across the territory. This is the GAGAN model: faster to initial capability, lower capital outlay, and it produces the operational data needed to justify a dedicated satellite later. Civil aviation certification runs in parallel with technical commissioning; expect the ICAO SARPS compliance process to be the long pole, not the hardware.

The next rung is a dedicated GEO satellite with the SBAS payload as a primary mission, potentially combined with a communications payload to share the bus cost. This is the KASS model. It gives the programme owner full control over payload parameters, orbital slot and service lifetime, but it requires an ITU filing for the orbital slot well before launch, typically five to seven years in advance of when you need the service. Spectrum coordination with neighbouring GEO operators is not optional and is rarely fast. That process should begin in the architecture phase, not after the satellite contract is signed.

The full sovereign programme adds redundant GEO coverage (two satellites for continuity), a sovereign mission operations centre staffed by nationally trained operators, and a reference-station network dense enough for integrity guarantees across all approach categories. This is a decade-scale commitment. The pathfinder phase is where you learn whether your territory's ionospheric environment, ground infrastructure and regulatory capacity support the full programme. Starting there is not a compromise; it is the professionally correct sequence.

What you own, and where the limits sit

At programme completion, the customer holds the GEO payload rights or satellite asset, the ground processing facility and its software under source-access terms, the reference-station network, the ITU filing and frequency coordination records, and a trained national operations team. Satellize's role ends at handover; the mission operations centre runs under national authority from that point. Contracts are structured so that source-access terms and hardware audit rights are agreed before signature, not negotiated after delivery.

The limits are worth stating plainly. SBAS integrity guarantees depend on the density and calibration of the reference-station network; sparse networks produce larger protection levels and may not meet Category I precision approach requirements across the full territory. The ionosphere above equatorial and sub-equatorial regions is more variable than mid-latitude environments; GAGAN's development programme spent considerable effort characterising the Indian ionosphere precisely because standard WAAS algorithms needed adaptation. If your territory straddles the equatorial ionospheric anomaly, the architecture study will need to account for that. And the GEO satellite, once launched, is in a fixed orbital slot: coverage geometry does not change, which is an advantage for aviation certification and a constraint if your territory expands or your requirements shift.

Starting the architecture study

The first concrete deliverable is a territory-coverage analysis: which reference-station sites give adequate geometry, what ionospheric model fits your latitude band, which GEO orbital slots provide adequate elevation angles across the territory, and whether a hosted or dedicated payload is the right first step. That study also maps the ITU filing timeline against your target operational date, because the filing process is the item most likely to compress your options if started late.

Satellize has delivered sovereign space programmes since 2018, including India's first privately built satellite and Tonga's communications restoration after the 2022 undersea cable break. The Tonga crop-estimation analytics programme is the one named analytics engagement we reference publicly. We do not cite other customers by name without their permission. What we can offer at this stage is a structured architecture study scoped to your territory, your aviation regulatory environment, and your existing ground infrastructure, with no obligation to proceed to build.

What this mission is built from

Geostationary orbit: Provides the geostationary orbital slot from which the SBAS integrity and correction broadcast reaches all territory within the coverage footprint.
Communications payloads: Hosts the SBAS signal-in-space payload on the GEO satellite bus, potentially alongside a communications payload to share bus and launch costs.
Sovereign mission operations centres: Houses the central processing facility, integrity monitoring and satellite command functions that the national team operates after handover.
Spectrum and ITU filings: Secures the ITU coordination and GEO orbital-slot filing required before the satellite can legally broadcast on GNSS L1 frequencies over national territory.
National licensing and space law: Establishes the domestic legal framework under which the SBAS service operates and the national civil aviation authority can certify approaches.
Engineer training programmes: Produces the nationally qualified operators and engineers who run the reference-station network, processing facility and satellite payload after handover.

What you end up owning

GEO payload rights or satellite asset, with hardware audit rights agreed before contract signature
Central processing facility and integrity-monitoring software under source-access terms
Reference-station network infrastructure at surveyed national sites
ITU orbital-slot filing and frequency coordination records
Trained national operations and engineering team qualified to run the mission operations centre
ICAO SARPS compliance documentation and civil aviation authority certification records

Handover is staged: reference stations and ground processing transfer to national operation first, followed by satellite command authority once the national team has demonstrated qualified control. Satellize retains no ongoing operational role after final handover; source-access terms mean the customer can engage any competent party for future upgrades. Launch and integration partners involved in the GEO satellite delivery maintain their own separate relationships with the customer for in-orbit support, as agreed in the tripartite terms established at contract signature.

Programme parameters

GEO satellites	1 (pathfinder, hosted payload) to 2 (full sovereign programme, dedicated bus)
Orbital slot	Territory-dependent; ITU filing required 5 to 7 years before target service date
Reference stations	8 to 20 (national territory); up to 40+ for regional or sub-equatorial programmes requiring denser ionospheric sampling
Signal broadcast	GNSS L1 frequency (1575.42 MHz); received by standard SBAS-capable avionics without modification
Accuracy class	Sub-metre horizontal (95%) with integrity; supports ICAO APV-I / LPV-200 approach minima when certified
Integrity alert time	6 seconds (ICAO SARPS requirement for aviation precision approach)
Timeline to initial capability	5 to 8 years from programme start (architecture, ITU filing, build, launch, certification); GAGAN and KASS are the public benchmarks
Operations team	Typically 15 to 30 nationally trained staff for a single-satellite national programme (reference-station monitoring, processing facility, satellite command)
Coverage	Fixed GEO footprint; elevation angle above 5 degrees across target territory is the geometric constraint on slot selection
GNSS dependency	Augments GPS, GLONASS, Galileo or NavIC; does not generate independent ranging signals; service degrades with underlying constellation

Sources

One contract, one accountable engineer

Commissioned as one programme, not a stack of contracts: spacecraft, launch, ground segment, mission control, training and handover are priced together. Source-access terms and audit rights are agreed in writing before signature. Commission a territory coverage study.