2019: DOAS measurement technique "Bike-DOAS" observes the composition of the troposphere from a bicycle.
Monitoring the composition of the troposphere has become a key topic in Earth observation from space. The Sentinel-5P satellite is an example of an endeavor of ESA in this field. Scientists of BIRA-IASB are heavily involved in data processing from TROPOMI.
Measurements from orbit can only be reliably interpreted if in parallel ground-based validation measurements are performed. Validation networks with Differential Optical Absorption Spectrometers (DOAS) are being set up at this purpose worldwide. So why not tie a DOAS to the back of your bike and “sniff” the air while you ride?
Delivery year: 2019
TROPOspheric Monitoring Instrument (TROPOMI) is a Dutch instrument on board ESA’s Sentinel-5 Precursor satellite that was placed in orbit in October 2017. Its main target is to localize pollution and monitor its composition. BIRA-IASB is involved in the data processing of the TROPOMI instrument, and in particular sulphur dioxide (SO2), formaldehyde (HCHO) and ozone (O3) algorithm development and validation.
In parallel to the flight of TROPOMI, ESA has organized the CINDI-2 campaign to test and inter-compare a wide range of Multi Axis DOAS (MAXDOAS) and other DOAS-type instruments. In a next step, the ESA FRM4DOAS project has set up an operational system to process MAXDOAS data from the Network for the Detection of Atmospheric Composition Change (NDACC) for validation of Sentinel-5P products.
Bike-DOAS design drawings (external and internal)
BIRA-IASB is involved with its own MAXDOAS but uses also a mobile-DOAS operated from a car. What you can measure from a car, you can also measure from a bike. From this straightforward reasoning the Bike-DOAS experiment was born.
Bike-DOAS installed on one of the foldable bicycles of BIRA-IASB
In a stationary MAXDOAS, a scanning mechanism is used to allow differential absorption measurements. A mobile DOAS is smaller and more lightweight by definition, and has no scanner. It records scattered light from two directions, zenith and 30° off-axis. It is extremely appropriate for measuring the chemical composition (e.g. NO2) of the lower troposphere.
The Engineering service of BIRA-IASB has designed and manufactured a mechanical structure that houses the spectrometer, together with a microcomputer, a GPS for geo-localization of the measured data, an optical entrance system and a battery.
Sentinel 5P – TROPOMI satellite. Credits ESA.
The design is very robust, supporting shocks and vibration, and is usable in different weather conditions. The main material is aluminum that has been surface treated and coated for better resistance against corrosion. Nevertheless, the box has a manual shutter that permits the biker to close the spectrometer and protect the entrance mirror and optics in case of rain.
The Bike-DOAS box is easily and securely mountable on the luggage rack of any bike. A simple command button is installed on the box allowing to switch on and off the DOAS at any time.
The Bike-DOAS computer can be remotely accessed by a tablet or smartphone which allows the operator to keep track of the measurements and instrument health.
Sniff’n ride (The bike) (2017-2018)
