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Air Quality Monitoring from Space

Updated: Jul 1, 2019

The EarthSense blog starts today with a short article to accompany a presentation to the Welsh Air Quality Forum on air quality monitoring from Space.

NO2 Measurements from Satellites

With a heritage from the University of Leicester's Space Research Centre, some aspects of EarthSense’s technological perspective are very tuned to the potential for actionable information to be derived from satellites in orbit around the Earth.

The majority of air quality information from satellites is derived from measurements of NO2 using scattered sunlight. In simple terms, the signature of NO2 within sunlight is very distinct, and is relatively easy for scientific instrumentation to measure multiple shades of blue light, and determine how much NO2 that light has been through.

There have been satellites using this technique in orbit since 1995 (GOME), and there are an increasing number of instruments now being launched around the world.

The challenge comes in working out what these measurements mean about the pollutant concentration at nose height, getting the fine spatial resolution that you would really like, and then getting any useful information to the end user quickly. This assumes that you’ve already overcome the large financial and technological hurdles to putting an instrument in orbit, and maintaining it.

A map showing satellite data for NO2 across Wales in August 2015
Averaged satellite data showing NO2 across the Wales, August 2015

Accessible Data

Data from the latest satellites is now pretty accessible to all, allowing anyone to download a .kml file of monthly NO2 data, to view in GoogleEarth. (an example for Wales in August 2015 is shown above).

Exciting new instruments are also due to be launched over the next decade, including Europe’s Sentinel 5P, 4 and 5 missions, which will push our data from 23km resolution (ie, one measurement for each 23x23km square on the ground) to 7km resolution.

The Sentinel 4 mission will also increase the temporal sampling (how often you measure the same spot on the Earth) from daily to hourly. This capability is replicated in Asia by the GEMS mission, and in the US by the TEMPO mission, providing great hourly global coverage from around 2020 onward.

The next challenge comes with the application of this data to systems which enable us to reduce the impact of pollution on human health and natural ecosystems. The good news is that the European Commission have invested in a range of Copernicus services, which pull in all available satellite data, and provide a stable data-feed of current concentrations, and forecast concentrations for the next 5 days through the CAMS service.

This data is relatively robust, but is at lower resolution than the raw satellite data, being approximately 50km over Europe and 100km for the global product. This is therefore not an immediate answer for many urban management systems.

EarthSense’s RapidAir modelling system is designed to assimilate any available satellite and modelled data (including direct feeds from OMI, and CAMS), and integrate these into the background field for a given urban environment. As new satellites are launched, this functionality will provide more and more valuable information to our customers.

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