Raw Tropomi data collected in space are not directly suitable for scientific research nor for applications. SRON and KNMI are scientifically in charge of Tropomi, making sure data are transformed into useful images and statistics. It is a monstrous job.
From 0 to 1: processing
Tropomi’s raw data are a collection of pixels, but they do not yet make a readable ‘image’. The first step is the so-called 0 to 1 processing. Starting point: information stored by the sensor. This information is not 100% pure, for it may contain distortion errors because of the instrument’s lenses. Or perhaps some diffused lighting might occur which has accidentally sneaked in. By using models, sensor information is returned to the original light that has entered the telescope. Then, important meta information is added to data like time, date and location of the observation.
From 1 to 2: interpretation
The result of Step 1 is a spectrum in which light is unravelled into several wavelengths. But having a spectrum is not enough. The next move is to analyse matters. Using existing models, lab simulations and historical satellite data, observations are interpreted at length. What exactly can we see? And how have things changed compared to previous years? The answers to questions such as these allow scientists to proceed.
From 2 to 3: products
Tropomi data are used for fundamental science, but also for ready-to-use products. For instance, to send out aviation warnings in case a volcano erupts, releasing a large dust cloud into the air. Or perhaps to communicate the expected air quality based on nitrogen dioxide measurements, or forecast UV radiation on a sunny summer’s day. With this information, beach visitors may decide which sun lotion they ought to put on.