LOAC sensor

General description

The aerosols study in the troposphere and stratosphere is of major importance for the study of climate and the air quality. Among the numerous instruments available, the state of the art is made up of aerosol particle counters providing distribution in diameters, yet most of them are very sensitive to the nature of aerosols introducing some biases in the retrieved size distribution. The LOAC is the result of a Private and public collaboration between the CRNS-LCP2E and Environment SA, Meteomodem is in charge of the distribution. The LOAC is an instrument compact and robust enough to be used at surface or launched under a balloon or even a UAV. This new original and versatile aerosol counting instrument doesn’t uses any lenses only a laser beam ant two scattering measurement angles, respectively at 12 and 60 ° enabling to determine the concentration of aerosols (numbers of aerosols per cm3) for 19 size classes between 0.2 and 100 micrometers . The combination of the two measurement angles allows also to determine the typology of the aerosols according to 4 main families of particles (Carbons, Droplets, salt and Minerals. The instrument can be used to document the physical properties of aerosols in the lower and middle atmosphere during specific events like pollution, transported sands, volcanic ashes, and for long-term monitoring.

LOAC is already involved in several research programs of atmospheric studies (determination of concentration and nature of tropospheric and stratospheric aerosols). In particular, LOAC has recently provided accurate measurements of the size distribution of Sahara sands transported over Mediterranean Sea. He also has been rewarded during the “Les respirations 2015 préCOP21”.

Characteristics of the sensor

Principle of Measurement

2 angles of measurement. The first is approximately of 12° and is almost insensitive to the nature particles of particles whereas the second of 60° is strongly sensitive to the refractive index of the aerosols. By combining these two angles of measurement, it’s possible retrieve accurately the size distribution and assess nature of the particles crossing the laser.

- Light and compact: 300g
- Pump: from 1,3 until 3,00
- No lense: no risk of misalignment
- Measures every 10 seconds
- Automatic check every ten minutes
- Real time stray light correction applied

- The LOAC can realize measurement, not only at the ground (LOAC Recorder), but also behind all kinds of balloons in the troposphere and stratosphere (LOAC telemetry)


More than 100 LOACs manufactured and sold worldwide

Permanent network measurement in three main sites in France:

- OAG in Paris: for analysis of the variations in concentration of the nature of urban aerosols and mainly during strong pollution events.
- Ground based measurement at SIRTA dedicated to the detection of Fog events.
- CNRS Orleans for the monitoring and identification of troposphere and stratosphere aerosols.


- Meteorological services: Particles/Aerosol Research, Physical documentation of aerosol properties, study of specific events such as sand plume, volcanic eruptions, strong pollution events…
- Research: laboratories, Specialized atmospheric Research institutes, Universities for several type of Study from the detection of fog to monitoring of urban pollution
- Air quality control authorities such like Cities/ Regions…