Overview
ISO/TR 22639:2021 - Space systems - Design guidelines for multi-geo spacecraft collocation provides practical guidance for the design and approval of spacecraft collocation in geostationary-type orbits, with particular focus on multi-geo constellations. The technical report defines a structured collocation design process covering initial considerations, separation strategy design, simulation-based evaluation, optimal strategy selection and the formal collocation agreement between operators.
Key topics and technical requirements
- Collocation design process: Stepwise workflow from operator consultation through strategy confirmation and agreement signing (orbit safety consultation, initial strategy proposals, simulation evaluation, iterative refinement, selection and formalization).
- Design considerations: Includes ITU frequency/allocation constraints and assigned orbital slots, number of collocated spacecraft, required safety separation distance (dmin - commonly 10 km by past international experience), orbit maintenance needs, orbit determination (OD) precision, flight dynamics perturbations (gravity, solar radiation pressure), fuel budgeting, central management capability, and special restrictions.
- Separation strategies: Core options described include:
- Complete longitude separation
- Coordinated station-keeping
- Absolute eccentricity separation
- Relative eccentricity vector separation
- Combined eccentricity and inclination vector separation
Annexes provide characteristics and fundamental principles of each strategy.
- Simulation evaluation: Strategies must be validated by simulation accounting for orbit perturbations, orbit control, OD errors and other error sources. Evaluation metrics include ensuring safety separation distances, acceptable orbit maintenance periods, and fuel consumption within budget.
- Collocation agreement content: At minimum the agreement should contain an introduction (motivations and parties), a summary of proposed strategies with justification, detailed parameters and data for the final strategy, and an information-exchange plan (formats, cadence and responsibilities).
Technical terms referenced include J2000 geocentric equatorial coordinates, RTN spacecraft coordinate system, inclination and eccentricity vectors, and mean longitude.
Practical applications
- Design and operation of multi-geo constellations and GEO slot-sharing arrangements.
- Flight dynamics and mission-planning for satellite operators planning collocation with existing spacecraft.
- Safety risk assessment, simulation and verification of separation strategies prior to mission execution.
- Drafting operational collocation agreements and establishing regular data exchanges between operators.
Who should use this standard
- Satellite operators and constellation managers
- Flight dynamics engineers and mission designers
- Systems integrators and operations teams involved in GEO/multi-geo deployments
- Regulatory and coordination bodies involved in orbital slot or frequency coordination
Related standards and references
- ITU regulations on frequency allocation and orbital slot assignment (referenced in considerations)
- ISO/TC 20/SC 14 working documents and related space-systems guidance
ISO/TR 22639:2021 is a practical resource for workforce members responsible for safe, efficient and compliant multi-geo spacecraft collocation planning and operations.