Space domain awareness

Dependence on a foreign catalogue for space situational awareness is a strategic liability. This page covers what a national SDA architecture actually comprises, what it costs in effort and time, and what you own when it is done.

The dependence this ends: The US Space Command catalogue as your only source

The catalogue you do not control can be withheld

The US Space Surveillance Network has tracked objects in Earth orbit since 1957 and publishes a public catalogue through Space-Track.org. For most governments, that catalogue is the entirety of their space domain awareness. The arrangement is convenient and, until recently, felt adequate.

It is no longer adequate. The public catalogue excludes objects the United States classifies, applies shutter-control equivalent logic to what it shares and when, and provides no guarantee of continuity to foreign governments during a crisis. Several allied and partner nations discovered in 2022 and 2023 that access to certain conjunction data messages could be delayed or qualified without notice. A government that cannot independently observe, catalogue and assess what transits its airspace and approaches its assets is, in effect, flying blind on someone else's instruments.

The post-2022 environment has sharpened this. Low-Earth-orbit congestion is accelerating: the Union of Concerned Scientists Satellite Database recorded more than 9,000 active satellites by early 2024, up from roughly 2,000 in 2019. Conjunction warning volumes are rising proportionally. Governments operating sovereign satellites, national infrastructure or defence assets in orbit need to know when another object will pass close, who operates it, and whether its RF emissions are consistent with its declared function. None of that is reliably available from a foreign catalogue.

What a national SDA architecture actually comprises

SDA is not a single sensor. It is a chain: detect, track, characterise, catalogue, warn, and decide. Each link requires different hardware and different skills.

Ground-based optical sensors are the entry point for most national programmes. A modest telescope of 0.5 to 1.0 metre aperture, equipped with a cooled CCD or sCMOS detector and precise timing, can detect and track objects in low Earth orbit to a limiting magnitude sufficient to catalogue most active satellites and debris larger than roughly 10 centimetres at LEO altitudes. Multiple sites improve revisit and reduce weather dependency. Radar adds all-weather, day-night capability and is essential for accurate ranging, but capital and operating costs are substantially higher. Several nations, including France with its GRAVES radar and Australia with its C-band space surveillance radar at Exmouth, have published details of phased national sensor builds that began with optical and added radar in later increments.

RF monitoring is the characterisation layer that optical sensors cannot provide. A satellite's radio emissions, whether telemetry, beacon, or payload downlink, carry information about its operator, its mode of operation and, in some cases, its mission type. A ground-based RF monitoring network, combined with signal-mapping payloads on orbit, can correlate a tracked object's orbital position with its emissions and flag discrepancies between declared and observed behaviour. This is distinct from the RF intelligence and emitter geolocation mission covered elsewhere in this library.

Catalogue maintenance requires software: an orbital propagator, a data-fusion pipeline that ingests observations from multiple sensors, and a conjunction screening tool that computes close-approach probabilities against your own assets. The European Space Agency's DISCOS database and the underlying methods are publicly documented and provide a reference architecture. Owning this software stack, with source access, is what separates a sovereign SDA capability from a subscription to someone else's service.

The ambition ladder: from first light to full programme

A pathfinder programme establishes the legal, spectrum and technical foundation. It typically comprises one or two optical sensor sites, an RF monitoring node, and a catalogue software instance seeded with public TLE data but capable of ingesting proprietary observations. Programmes of this class, based on publicly reported national initiatives in Southeast Asia and the Middle East, have been delivered in 24 to 36 months from contract. They do not replace the US Space Command catalogue; they begin to cross-check it and build national observation history.

An operational constellation adds sensor diversity and geographic spread. Three to five optical sites across different longitudes dramatically improve revisit on any given orbital plane. Adding a phased-array radar, even a modest one, moves the programme from tracking to ranging with centimetre-class precision. At this level, a nation can issue its own conjunction data messages for its sovereign satellites and share data with allied networks on its own terms. Japan's SSA programme, which operates optical sensors at multiple sites and has published its architecture through JAXA, illustrates the multi-site optical approach before radar integration.

A full sovereign programme includes on-orbit sensors, a national space operations centre with 24-hour staffing, bilateral data-sharing agreements with at least one allied SDA network, and a formal catalogue that is legally recognised for conjunction liability purposes under the nation's space law. This is a decade-scale endeavour. France's GRAVES and the broader CNES/DGA SSA architecture, developed over roughly 15 years, is the clearest public reference for what full sovereignty looks like and what it demands institutionally, not just technically.

Cost classes are difficult to state honestly without knowing a nation's existing sensor infrastructure, spectrum licensing position and workforce baseline. Small optical sensor sites have been delivered for low single-digit millions of dollars. A multi-site optical network with catalogue software sits in the low to mid tens of millions. Adding radar and on-orbit components moves programmes into the hundreds of millions over a multi-year delivery. Satellize does not publish a price list for this mission type; the variance is too large to be useful without a site survey and spectrum assessment.

What you own and what you cannot buy away

At handover, the customer holds physical sensor hardware at agreed sites, source code for the catalogue and conjunction software under agreed licence terms, spectrum assignments registered with the ITU in the nation's name, trained operators holding current certification, and the observation archive accumulated during the programme. These are not licensed services that can be switched off.

The limits are equally concrete. Ground-based optical sensors are weather-dependent. A site with 60 per cent cloud cover loses proportionally more than 60 per cent of its observation opportunities because cloud tends to cluster in the hours around dawn and dusk, which are the optimal geometry windows for LEO observation. Radar mitigates this but does not eliminate it. A catalogue maintained by a single nation with a small sensor network will have lower object completeness than the US Space Command catalogue for the foreseeable future, particularly for objects below 10 centimetres. Conjunction warnings issued from a national catalogue carry the uncertainty of that catalogue's track quality, which improves only with time and observation volume.

The RF monitoring layer adds characterisation capability but cannot definitively attribute intent. Detecting that a satellite's emissions are inconsistent with its declared mission is a flag, not a verdict. Analysis requires human judgement and, frequently, corroboration from signals intelligence channels that sit outside the SDA programme's scope.

How Satellize structures this programme

Satellize's role in an SDA programme is architecture and integration. The sensor hardware, whether optical telescopes, RF monitoring arrays or radar subsystems, is sourced from manufacturers with established space-surveillance heritage and integrated under a single contract with a single accountable engineer. Launch procurement, where on-orbit components are included, is arranged and integrated with launch partners. Ground stations and mission control infrastructure are built to the customer's sovereignty requirements, including hardware audit rights and staged handover to national teams.

The Tonga sovereign-communications restoration programme demonstrated the staged-handover model in a compressed timeline: Satellize delivered, trained and handed over operational control to Tongan national staff. The SDA mission applies the same contractual logic, but over a longer delivery arc and with a more complex sensor network. Source-access terms for catalogue and conjunction software are agreed before contract signature, not negotiated after delivery.

The configuration components listed on this page, RF signal-mapping payloads, exploitation and analysis software, in-country data processing and operator training and certification, represent the layers that sit between raw sensor data and an actionable national picture. Each is documented separately in the Satellize space-stack library.

What this mission is built from

RF signal-mapping payloads: Characterises satellite emissions from orbit or ground to correlate tracked objects with their declared functions and flag anomalies.
Exploitation and analysis software: Provides the orbital propagation, data-fusion and conjunction-screening tools that turn raw observations into a maintained national catalogue.
In-country data processing: Keeps observation data, track files and conjunction warnings within national jurisdiction, on infrastructure the customer owns and audits.
Operator training and certification: Trains national staff to operate sensors, maintain the catalogue and issue conjunction warnings without external dependency.

What you end up owning

Physical optical sensor hardware at agreed national sites, with maintenance documentation and spare-parts inventory
Source code for catalogue maintenance and conjunction-screening software, under terms agreed before contract signature
ITU spectrum assignments registered in the nation's name for any RF monitoring frequencies
The national observation archive: every track file and RF measurement collected during and after the programme
Trained national operators holding current certification, with a documented succession-training plan
Ground station and data-processing infrastructure sited in-country, with full hardware audit rights

Handover is staged across the programme: sensor operation transfers to national staff before catalogue software, and catalogue software before conjunction-warning authority, so each capability is proven under national control before the next is transferred. Satellize retains no ongoing licence over delivered software or hardware after final handover. Integration partners who supplied sensor subsystems may retain standard manufacturer warranties; these are disclosed at contract signature.

Programme parameters

Pathfinder sensor network	1 to 2 optical sites, 1 RF monitoring node, catalogue software instance
Operational constellation	3 to 5 optical sites across multiple longitudes, optional phased-array radar addition
Full sovereign programme	Multi-site optical and radar network, on-orbit RF monitoring component, 24-hour national space operations centre
Pathfinder delivery timeline	24 to 36 months from contract to first national observation, based on published national programme precedents
Full programme timeline	8 to 15 years to full operational capability with radar and on-orbit components, consistent with French and Japanese public programme records
Optical detection floor (LEO)	Objects of approximately 10 cm and larger at LEO altitudes, dependent on aperture and sky conditions
Weather dependency	Optical sensors require clear sky; multi-site networks mitigate but do not eliminate cloud-cover loss
Minimum operator team	4 to 6 trained national staff for pathfinder; 15 to 25 for 24-hour operational centre, consistent with published SSA programme staffing models
Catalogue completeness	National catalogue will have lower object completeness than US Space Command for objects below 10 cm; improves with observation volume over time

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. Request a national sensor-site assessment.