Overview
ISO/TR 16158:2021 - "Space systems - Avoiding collisions among orbiting objects" - is a technical report that provides guidance for collision avoidance, conjunction assessment, and collaborative operations to sustain the space environment. The document outlines a practical workflow for perceiving close approaches, estimating collision probability, tracking cumulative survival risk, and planning manoeuvres to avoid collisions. It emphasizes that all conjunction assessment techniques are statistical, variable in uncertainty, and require high-quality orbit data and operator collaboration.
Key topics and technical requirements
- Collision avoidance workflow: End-to-end process from orbit data ingestion to decision-making and manoeuvre execution.
- Orbit data requirements: Metadata and trajectory inputs needed for credible conjunction assessment (epoch, coordinate frames, force models, estimation errors); aligns with ISO 26900 data expectations.
- Perceiving close approaches:
- Orbit propagation over intervals of interest
- Initial filtering approaches (including all‑against‑all screening)
- Elimination techniques (sieves, toroidal elimination, apogee–perigee filters)
- Conjunction screening methods:
- Symmetric keepout and bounding-volume approaches
- Probability‑based techniques and maximum-probability estimation
- Probability contour visualization and topology (informative annexes)
- Probability of survival and cumulative risk:
- Trending of collision risk over time
- Cumulative survival probability and Bayesian assessment approaches
- Operational considerations:
- Manoeuvre capability and spacecraft characteristics
- Quality indicators for orbit data and metadata needed for operational judgments
- Consequence and traffic impact assessment: Guidance on assessing population risk and broader traffic effects.
- Informative annexes: Nomograms and visual tools to relate object size, positional uncertainty, and collision probability.
Practical applications and users
ISO/TR 16158:2021 is intended for:
- Satellite operators and mission planners for conjunction screening, risk-informed manoeuvre decisions, and operational procedures.
- Space situational awareness (SSA) providers and sensor networks to standardize data products and filtering workflows.
- Risk analysts and safety engineers assessing cumulative survival probabilities and population-level impacts.
- Regulators, insurance underwriters, and collaborative frameworks establishing information exchanges and interface control documents (ICDs).
Practical benefits include improved decision support for manoeuvre planning, consistent interpretation of collision probability metadata, and enhanced interoperability among operators exchanging orbit and conjunction data.
Related standards
- ISO 26900 - referenced for essential orbit data content and metadata.
- Work prepared by ISO/TC 20/SC 14 (Space systems and operations).
Keywords: ISO/TR 16158:2021, collision avoidance, conjunction assessment, collision probability, orbit data, satellite operators, space situational awareness, manoeuvre planning, cumulative probability of survival.