Overview
ISO/TS 21979:2018 provides a standardized engineering procedure to estimate the worst-case and confidence level of radiation fluence on satellites using a quasi-dynamic model of Earth’s radiation belts. Rather than relying on static average models, this Technical Specification uses long-term activity indices and a quasi-empirical approach to reproduce temporal fluctuations of the Van Allen belts and produce a probability distribution of expected fluence for a given orbit and mission duration. It is intended for satellite design and similar engineering purposes.
Key topics and technical requirements
- Quasi-dynamic radiation belts model: Uses easily obtainable input indices that correlate with belt variability (e.g., Sunspot number, F10.7, solar wind speed, Kp/ap, Dst, IMF).
- Fluence calculation procedure (Annex A): stepwise method including
- conversion of orbit to magnetic coordinates (B/B0 and L-value),
- calculation of daily average particle fluence over a recurrence window (30 days used as an example),
- accumulation over the proposed operation period,
- generation of histograms and probability distributions to derive worst-case and confidence levels.
- Supported models: Example quasi-dynamic implementations described include the CRRESELE model (Annex B) and the MDS-1 radiation belt model (Annex C).
- Particle populations covered: Magnetically trapped electrons (~100 keV to tens of MeV) and protons (~100 keV to ~1 GeV), including inner/outer belt and slot region considerations.
- Data requirements: The technique is applicable when at least ~10 years of driving-parameter data are available to capture long-term variability.
- References to fluence metrics: Cumulative fluence and confidence level definitions are tied to ISO 12208:2015 methods.
Applications and who uses it
ISO/TS 21979:2018 is useful for:
- Satellite designers and systems engineers - to size shielding, electronics hardness, and design margins based on quantified worst-case environments.
- Radiation effects analysts - to produce probabilistic fluence inputs for single-event and total-dose analyses.
- Mission planners and spacecraft operators - for launch-date sensitivity studies and operational risk assessments.
- Space weather modelers - to validate or compare quasi-dynamic approaches against physics-based models.
Practical uses include defining design margins, selecting radiation-hardened components, planning mission timelines, and deriving probability-based environmental requirements.
Related standards
- ISO 12208:2015 - methods for cumulative fluence and confidence level definitions (referenced for calculation principles).
- ISO 16457:2014 - terminology related to solar indices (used for definitions such as sunspot number).
Keywords: ISO/TS 21979:2018, quasi-dynamic model, Earth’s radiation belts, radiation fluence, worst-case fluence, confidence level, satellite design, CRRESELE, MDS-1, space environment.