Overview
ISO 20930:2018 - Space systems - Calibration requirements for satellite-based passive microwave sensors - defines end-to-end calibration requirements and verification methods for passive microwave instruments from design and manufacturing through ground testing and on‑orbit operation. It applies to microwave radiometers and sounders (typical bands ~1 GHz to 200 GHz) and standardizes procedures to reduce inter-sensor bias and improve the radiometric quality of antenna brightness temperature products used for weather, hydrology and climate applications.
Key topics and technical requirements
- Scope and objectives
- Requirements cover sensor design, analysis, manufacturing, ground tests, on-orbit self-calibration and validation.
- Includes procedures for on-orbit inter-comparison and preparation for cross-calibration.
- Instrument components addressed
- Cold Calibration Target (CCT), Warm Calibration Target (WCT), Main Reflector (MR), Receiver (Rx), Noise Calibration Source (NCS), Antenna sub-system (ANT), and Data Processor (DP).
- Pre‑launch (design & ground test)
- Precise specification and verification of instrument characteristics; submission of engineering formulas/parameters to ground processing.
- Requirements for CCT/WCT design (reflectivity, emissivity, spill‑over patterns), antenna pattern measurement/modelling and uncertainty budgeting for antenna brightness temperature (Tb).
- On‑orbit calibration
- Self‑calibration strategies using WCT/CCT and procedures to eliminate bias, characterize sensitivity, perform deep‑space manoeuvres and maintain radiometric resolution.
- Validation methods including use of Standard Reference Targets (SRT) and ground‑based ancillary data (see informative Annexes A–D).
- Processing and data quality
- Level‑one processing requirements to convert raw measurements to radiometrically and geometrically compensated Tb products.
- Emphasis on minimizing bias (e.g., sub‑Kelvin accuracy targets relevant to climate and sea surface temperature monitoring).
Practical applications and users
ISO 20930:2018 is intended for:
- Satellite system and payload engineers responsible for design, verification and manufacturing of passive microwave sensors.
- Calibration and ground processing teams who implement radiometric correction, uncertainty budgets and Level‑1 processing.
- Mission managers, agencies and satellite operators coordinating cross‑calibration and inter‑satellite consistency.
- Remote sensing analysts, meteorologists, hydrologists and climate scientists who rely on consistent microwave observations for soil moisture, precipitation, snow cover, sea ice and atmospheric profiling.
Practical benefits include improved weather‑forecast inputs, more accurate sea surface temperature and soil moisture products, and reduced effort in post‑processing bias compensation.
Related standards
- Normative references cited in ISO 20930: ISO 10795:2011 (space systems programme management and quality - vocabulary) and ISO 14302 (space systems - electromagnetic compatibility requirements).
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