Earth’s system is a coupled system where the different components (the atmosphere, the hydrosphere, the lithosphere, and the croyosphre) are constantly interacting at different spatial and time scales.

Atmospheric composition and thus air quality (what impacts human health as well as other lifeforms inluding agriculture) is a hot topic and active area of research. When it comes to air quality, measurements of pollutant concentrations like particulate matter and trace gases is not new and continues to develop and expand as technology keeps improving and measurement networks keeps growing.

However, like in atmospheric science and hydrology point based measurements can only do so much. For example, determining the water level or water speed at a point along a river stream requires an understanding of the surface elevation (known bathymetry when under water) and whether the point of interest is upstream or downstream the river. Similarly, how the concentration of a pollutant evolves is governed by the underlying driving forces most notably the wind field, the pollutant lifetime, and the nature of the chemical interactions that arise.

It is therefore critical that the evolution of different chemical elements (pollutants if they affect human life) are tracked and studied in detail. Some of the questions science is trying to answer when it comes to air quality include:

• What are the spatial and temporal variations of the concentrations of pollutants?
• How are local and regional air quality affected by long-range transport?
• How does air quality and climate change drive each other?
• How is air quality affected by metrology and how are pollutants dispersed by weather?
• How can fluxes between different regions be quantified or estimated?

For these and other questions to be answered monitoring is required at the appropriate scale and temporal frequency of the underlying phenomena. Here then the role of satellite-based monitoring comes into play. A number of organisations have teamed up towards the same goal of making this monitoring a reality. A “virtual” constellation of satellites will be composed of three missions that will monitor air quality from space at unprecedented quality.