ISO 21740:2025

Overview

ISO 21740:2025 - Space systems - Launch window estimation and collision avoidance - defines the safety LCOLA (launch collision avoidance) requirements for identifying safe launch opportunities and preventing collisions between newly launched objects (launch vehicle stages, payloads, released objects) and human‑inhabited or human‑habitable space stations and vehicles. The standard prescribes how to analyse launch times, assess collision risk metrics (notably launch collision probability and standoff distance), and produce LCOLA products to support launch‑hold decisions.

Key topics and technical requirements

• Scope of safety LCOLA: Focus on collision avoidance for launches that could threaten inhabited or inhabitable space systems during ascent and early orbit.
• Launch trajectories: Trajectories for all launch vehicle stages and deployed objects - including planned disposal manoeuvres - must be developed to enable LCOLA analysis across all mission segments where conjunctions may occur.
• Ephemerides for inhabited vehicles: Collect authoritative, numerically integrated orbital states for human‑occupied systems; semi‑analytical products such as TLEs/SGP4 are explicitly discouraged for inhabited stations due to reduced accuracy.
• Close‑encounter checks: For each candidate launch time, compare launch element ephemerides with inhabitable vehicle ephemerides to identify conjunctions and assess collision risk.
• Risk metrics and thresholds: Define and apply launch collision probability and standoff distance criteria. The LCOLA approving agent sets metric thresholds and launch‑hold criteria to render collisions with human missions a virtual impossibility.
• Operational elements: Requirements cover screening timespans, analysis run sequencing, minimum standoff thresholds, and the content/format of the LCOLA product (exchange formats such as CCSDS ODM are noted as suitable).
• Annex guidance: Informative annexes provide methodologies, mission‑assurance considerations, and survey material to support implementation.

Practical applications

• Pre‑launch safety analyses to determine safe launch windows and launch‑hold decisions.
• Integration into launch range operations, mission planning, and range safety workflows.
• Supporting regulatory compliance and adherence to international guidance (e.g., UN Long‑Term Sustainability guidelines) by reducing collision risk to crewed assets.
• Mission assurance assessments to protect newly launched objects and reduce fragmentation risk during the initial orbital screening period.

Who should use ISO 21740:2025

• Launch service providers and mission planners conducting pre‑launch LCOLA analysis
• LCOLA approving agents, range safety organizations, and space agencies
• Spacecraft operators of inhabited/habitable stations and commercial SSA providers
• Systems engineers and SSA analysts implementing launch window estimation tools

Related standards (if applicable)

• CCSDS data formats (recommended for ephemeris exchange, e.g., ODM)
• ISO standards covering space traffic coordination and on‑orbit collision avoidance are closely related; ISO 21740 aligns with broader ISO space safety content (other related ISO documents are under development).