14.1.1 — Space Traffic Management — maturity: live

Conjunction Assessment & Avoidance

Detecting, assessing and responding to close-approach events between active satellites and debris before they become collisions.

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Every satellite a nation operates is exposed to collision risk from the roughly 35,000 tracked objects above 10 cm and an estimated 1 million fragments too small for ground-based radar to catalogue reliably. A conjunction event — two objects passing within dangerous proximity — can escalate from probability spike to unavoidable impact in under 72 hours. Without an independent assessment capability, a space-operating nation is dependent on the US 18th Space Defense Squadron's public CDMs, which carry no service-level guarantee, are deliberately degraded for foreign operators, and go silent the moment the US classifies an event.

A sovereign conjunction-assessment architecture combines space-based optical and radar surveillance with ground-based phased-array tracking to generate independent state vectors and probability-of-collision (Pc) estimates. The satellite layer — a constellation of electro-optical and RF-ranging microsats in complementary LEO planes — provides in-situ observations of resident space objects that ground radar misses, particularly in the 1–10 cm regime that sits below current TLE catalogue thresholds. Fusing these observations with a national high-fidelity orbit determination pipeline closes the loop from detection to manoeuvre recommendation without any foreign intermediary.

The operational payoff is manoeuvre autonomy. A national space operations centre that generates its own Pc values, tracks its own conjunction timelines and issues its own manoeuvre advisories can protect its satellite fleet on its own schedule, share data selectively with allies, and credibly argue treaty compliance during a disputed event. It also gives the nation standing in multilateral STM forums — you cannot negotiate rules you do not have the instruments to enforce.

What matters

The US 18th Space Defense Squadron's Conjunction Data Messages are a courtesy product with no SLA and are withheld or degraded for operators from non-allied nations.
A Pc threshold of 1-in-10,000 is the de facto international manoeuvre trigger, but the quality of that number depends entirely on whose state vectors feed it.
Kessler-regime cascade in densely populated LEO shells (550 km, 1,200 km) makes timely, accurate conjunction screening a sovereign infrastructure-protection obligation, not an optional service.
Manoeuvre decisions made on a foreign authority's data create legal and escalatory ambiguity when a collision occurs near a military or dual-use asset.

Sovereignty score: 9/10 — A nation that cannot independently assess collision risk around its own satellites surrenders operational control of its space infrastructure to a foreign power that has no legal obligation to warn it.

Geopolitical exposure: US CDMs are a discretionary service and have historically been withheld or downgraded for politically non-aligned operators; a nation with military satellites cannot accept that dependency.
Escalation control: in a crisis, a disputed conjunction near a dual-use satellite requires a sovereign Pc estimate to distinguish a natural close-approach from a proximity operation — without one, the nation cannot credibly respond or stand down.
Supply-chain and continuity risk: commercial conjunction-assessment services (LeoLabs, ExoAnalytic) are US-domiciled, subject to ITAR and export controls, and can be denied at any point under US national security authority.
Treaty and liability standing: the 1972 Liability Convention requires a launching state to demonstrate due diligence; a state that relies solely on foreign data products has a weak position in any compensation or attribution dispute following a collision.

Reference architecture

Payload: Electro-optical star-tracker-class sensor (0.5 m aperture, 10th magnitude detection limit) for space-based optical surveillance of RSOs; secondary RF ranging transponder (S-band, 400 MHz bandwidth) for in-situ range-rate measurement of cooperative targets to ±10 m accuracy
Bus class: ESPA-class microsat, 150 kg dry, 600 W total power, cold-gas propulsion with 50 m/s delta-V for station-keeping and orbit adjustment
Orbit: Sun-synchronous LEO at 550–600 km and 1,100–1,200 km (two shells), 18-satellite walker constellation (9 per shell, 60° inclination offset), achieving sub-4-hour revisit on any RSO in the monitored regime; supplemented by 2 ground-based phased-array radars (UHF/S-band, 1,500 km range) at high-latitude sites
Ground segment: National Space Operations Centre with 3-station TT&C network (S-band uplink, X-band downlink); high-performance computing cluster for orbit determination (OD) running GODOT or equivalent open-source OD software; encrypted cross-link to allied SSA networks via bilateral data-sharing protocols
Software & data
Latency
Cost band
Lead time

References

Space Debris by the Numbers — ESA Space Debris Office — ESA's Space Debris Office publishes regularly updated statistics on the tracked and estimated resident space object population, including collision probability drivers. The figures underpin the urgency of independent national conjunction screening capabilities.
Conjunction Data Messages — Space-Track.org (18th SDS) — Space-Track documents the format, latency and access conditions of US-issued CDMs, making explicit that the service is provided on a best-effort basis with no guaranteed availability. Non-allied operators face additional registration and data-sharing obligations.
Space Sustainability — UNOOSA Long-term Sustainability Guidelines — UNOOSA's LTS Guidelines (adopted 2019) call on states to implement conjunction assessment processes and share relevant space situational awareness data, implicitly expecting national-level capability. States without independent assessment tools cannot meaningfully implement Guideline 2.2.
Space Traffic Management — IAA Cosmic Study — The International Academy of Astronautics' foundational STM study identifies conjunction assessment as the critical technical prerequisite for any enforceable traffic management regime. It argues that sovereign data generation is necessary for equitable participation in rule-making.
EU Space Programme SST Consortium — Service Description — EU SST provides collision-avoidance screening to European operators pooling member-state sensor networks, demonstrating that regional sovereign sensor fusion is operationally viable. Non-EU nations are explicitly excluded from the full data product, reinforcing the case for independent national assets.