Global planning: Coordinating and optimizing the availability of Earth observing satellites for weather and climate is at the core of this activity. Planning and building satellites takes many years, therefore WMO regularly assesses the status of satellites contributing to the space-based component of WIGOS. Based on this, WMO analyses whether current and planned satellite missions (and other observing systems) meet the challenges of weather and climate applications in a process called Rolling Review of Requirements. The resulting gap analyses are used to guide the evolution of WIGOS and to optimize the effectiveness of its components.
WMO has developed its "Vision for the GOS in 2025" (
) that provides a long-term goal for the development of the space-based observing systems, and extending this Vision to 2040 is underway. Satellite operators in the Coordination Group for Meteorological Satellites have agreed on a mission baseline to address the WMO requirements which nominally consists of:
- A constellation of operational geostationary satellites including at least 6 spacecraft to ensure full coverage from 50°S to 50°N with a zenith angle lower than 70°.
- A constellation of operational low-Earth orbit sun-synchronous satellites, operated around three orbital planes (equatorial crossing time in mid-morning, afternoon, and early morning)
- Other missions in sun-synchronous orbits (e.g., scatterometers, radar altimeters, radio occultation sounders, Earth radiation budget instruments , UV sounders, imagers)
- Other missions in other orbits (e.g., radar altimeters, radio occultation sounders, rain radars)
Intercalibration: To ensure data quality and consistency from these satellites, WMO promotes the intercalibration of satellite instruments and harmonization of their specifications: together with CGMS, WMO coordinates the Global Space-based Intercalibration System, aiming at consistent accuracy among space-based observations worldwide for climate monitoring, weather forecasting, and environmental applications. This is achieved through:
- monitoring instrument performances,
- operational inter-calibration of satellite instruments,
- tying the measurements to absolute references and standards, and
- recalibration of archived data.
The transition of mature research systems to operational status is encouraged when appropriate, with a view to improve operational capabilities in line with evolving requirements, while ensuring the long-term sustainability required for operational applications and climate monitoring.
Remote-sensing Radiofrequency Coordination
The availability of radio-frequency bands through adequate frequency allocations and protection measures is vital for space-based remote sensing. This use of the radio-frequency spectrum for space-based remote sensing (Earth Exploration and Meteorological Aids) is faced with a severe competition with the expansion of radio-communications.
Specific objectives of these activities are:
- to prevent any artificial emission in those natural atmospheric radiation bands that are used for passive radiometry, in particular in the microwave region.
- to secure the allocation of frequencies needed for active measurements, in particular in the microwave spectrum.
- to secure the allocation of frequencies needed for safe spacecraft operations and data download, and prevent any interference among the various satellite systems comprising the space-based observing system.
Frequency allocations are part of the International Radio Regulations that are developed and negotiated among national telecommunications authorities and eventually agreed at the World Radio Conference, which is organized on a regular basis by the International Telecommunications Union (ITU). Preparations for the World Radio Conference involve detailed studies and assessments by the various communities involved. For the meteorological community, these issues are addressed within WMO by the Steering Group on Radio-Frequency Coordination (WMO SG-RFC). Space Agencies have established the Space Frequency Coordination Group (SFCG) to coordinate their activities in this respect.
