Stratéole-2 Becool: microLiDARs span the globe aboard hot-air balloon up to 22km high in the stratosphere.

Keywords : Aerosols, LiDARs, monitoring, Earth observation, remote sensing, stratosphere, troposphere.

April 13th 2022

On the night of Wednesday, August 22, 2018, the CIMEL’s microLiDAR flew for the first time in a stratospheric balloon for the validation of the project, from Timmins Air Force Base, in Ontario (Canada).

Stratéole-2 is a program of observation of the dynamics of the atmosphere in the intertropical zone developed in partnership between CNRS and CNES. The LATMOS (Atmosphere, environment and space observations laboratory) through its joint laboratory with CIMEL: CIEL), the LMD (Dynamic Meteorology Laboratory) and the CSA (Canadian spatial agency) are also collaborating in this project. 

This Stratéole-2 project called BECOOL (BalloonbornE Cirrus and convective overshOOt Lidar) mainly consists in placing CIMEL’s MicroLiDARs in stratospheric hot-air balloons and flying them around the world. The on-board aerosols microLiDARs emit lasers downwards, contrary to the initial use (the shots are normally done from the ground towards the atmosphere).

The project Stratéole-2 represents several challenges as CIMEL had to develop, in collaboration with the LATMOS a microLiDAR prototype which must correspond to the following standards:

  • Weighting less than 7 kg
  • Consuming less than 10 W
  • Resisting to harsh temperature conditions

Indeed, CIMEL’s LiDARS are well known for their robustness and their energetic Self-reliance which allows a low maintenance: practical when the LiDARs are up to 20km in the stratosphere!

Figure 1: Preparation of a stratospheric balloon before the takeoff

The program uses stratospheric pressurized balloons filled with helium 11 to 13 meters in diameter. During 3 to 4 months, they are carried by the winds all around the tropical belt and are propelled up to 20 kilometers in the atmosphere. Some can travel across 80,000 kilometers around the world (Figure 2).

Figure 2: Stratéole-2 Long-duration balloon flights across the tropics to study atmospheric dynamics and composition /

The project includes a total of three measurement campaigns realized between 2018 and 2024. Contrary to the previous one which served as a validation, the second campaign was for scientific purposes. It started in mid-October 2021 and ended in April 2022 . No less than eight microLidar balloons were released in the atmosphere from the Seychelles (Mahé). They collected valuable information which will then be analyzed for the study of atmospheric phenomena and their role in the climate. The third campaign is planned for 2024.

The objectives are to try to clarify some of the grey areas that hinder our detailed understanding of the atmosphere and its role in the Earth’s climate. BECOOL allows scientists to study atmospheric dynamics and composition such as convection or the dynamic coupling between the troposphere and the stratosphere. Exchanges and air movements between these two atmospheric layers are important and influence the whole planet.

However, the tropical region is difficult to access. Consequently, the classical methods of observation (by satellites, by plane, …) are not enough. This is why using balloons is strategic: they are the only ones able to observe these phenomena in real time and very closely to the atmosphere.

“It is a completely original mode of sampling, which is not obtained otherwise and allows results of unequalled finesse” (A.Hertzog).

Below is a quicklook from a Stratéole-2 microLiDAR taken from a balloon.

Figure 3: Quicklook LATMOS-Stratéole 2018


E. J. Jensen et al, Bull. AMS, 129-143 (2017), M. McGill et al., Appl. Opt.,(41) 3725-3734 (2002), J. S. Haase et al., Geophys. Res.L., 39, (2012), P. Zhu et al., Geos. Inst. Meth. and Data Systems, 89-98, (2015) J.-E. Kim et al, Geophys. Res. L. (43), 5895-5901 (2016), S. Davis et al., J.Geophys Res, 115 (2010) S. Solomon et al., Science (327), 1219-1223 (2010) V. Mariage et al., Optics Express 25 (4), A73-A84 (2017) ,G. Di Donfrancesco et al., Appl. Opt. (45) 5701-5708 (2006)

François Ravetta, Vincent Mariage, Emmanuel Brousse, Eric d’Almeida, Frédéric Ferreira, et al.. BeCOOL: A Balloon-Borne Microlidar System Designed for Cirrus and Convective Overshoot Monitoring. EPJ Web of Conferences, EDP Sciences, 2020, The 29th International Laser Radar Conference (ILRC 29), 237, 07003 (2p.). ff10.1051/epjconf/202023707003ff. ffinsu-02896973f


Pearl and Opal CE318-T photometers recording AOD and measurements in Canada’s high Arctic for AEROCAN.

Keywords : Aerosols, photometer, monitoring, Earth observation, remote sensing, CAL/VAL, Arctic.

March 23rd 2022

The Canadian Arctic is probably one of the best areas to conduct climatological studies, especially on global warming given the purity of the atmosphere in this zone, especially due to the absence of anthropological pollution.

Nevertheless, this rather hostile land, due to its temperatures, can make the difficulties of recording measurements very real. Consequently, there is a lack of measurements in the Arctic, hence the need to install platforms with robust and reliable measuring instruments.

Some of those platforms, especially PEARL and OPAL, have a particular emphasis on the Arctic because Canada has a significant portion of its territory in the Arctic.

The Polar Environmental Atmospheric Research Lab (PEARL) and the zerO altitude Polar Atmosphere Laboratory (OPAL) which is part of PEARL, is operated by the CAnadian Network for the Detection of Atmospheric Change (CANDAC) which is a member of AEROCAN. Formed in 2005, PEARL constitutes a network of universities and government researchers dedicated to studying the changing atmosphere over Canada.

The first task of PEARL was to renew and operate the existing laboratory at Eureka in Nunavut, which was created to contribute to the world-wide effort to intensively study the Arctic region through AEROCAN.

The AEROCAN photometer network is run as a joint collaboration between the Université de Sherbrooke and the Meteorological Service of Canada (MSC). It is a full-fledged sub-network of the much larger AERONET network of Cimel photometers and benefits from all the services that AERONET offers.


  • Understanding atmospheric change over Canada
  • Integration of measurements taken from space, aircraft, balloons and the ground
  • Provision of quality-controlled research datasets to researchers
  • Linkage with international networks for data exchange and supranational planning

In addition, PEARL undertakes measurements that are simultaneous with those made by various satellite instruments. These “validation” measurements are extremely effective because of the location of PEARL and OPAL, and they further enhance the science return of the research as they use state-of-the-art technology solutions like the CE318-T Photometer.

PEARL is located at Eureka, Nunavut (80N, 86W) on Ellesmere Island in Canada’s high Arctic, 450 km north of Grise Fiord, the most northerly permanent settlement. This photometer site is 1,100 km from the North Pole. OPAL is located about 12 km southeast of the PEARL ridge lab which is at an elevation of 610 m. This dual placement was designed to study the layer between the two sites as well as provide an element of redundancy for the AOD measurements.

Figure 1: Location of PEARL and OPAL photometer sites (upper pictures : 2007 CANDAC/Ovidiu Pancrati, bottom picture: Norm O-Neill, Université de Sherbrooke)
Figure 2: PEARL CE378 Photometer pointing to the sun for a measurement scenario
Figure 3: Latest measurements from Opal (above) and Pearl (bottom) photometers depicting AOD (Aerosol Optical Depth). Credits: NASA AERONET:


A multi-year AOD and effective radius climatology for the high Arctic showed a number of consistent features using the Cimel CE318-T Photometer:
• Spring to summer decrease of fine-mode AOD (probably attributable to biomass burning and/or anthropogenic pollution)
• Significant correlation of fine mode AOD with CO (Carbon monoxide) concentration which indicates a predominance of biomass burning aerosols throughout the entire year
• West to East decrease in AOD on a pan-Arctic scale
Another study (Antuña-Marrero et al., 2022) has been conducted for water vapor research.
It shows that it is feasible to use Cimel CE318-T Photometer AERONET observations in the Arctic for water vapor research, considering the robust quantification of its dry bias that has been established.
As a matter of fact, AERONET imposes standardization of instruments, calibration, processing and distribution that Cimel is the exclusive provider. Its IWV (Integrated Water Vapor) observations are an ideal standard dataset to re-calibrate or homogenize the rest of the instrumental IWV observations to a predefined absolute standard dataset.


  • Antuña-Marrero, Juan Carlos & Román, Roberto & Cachorro, Victoria & Mateos, David & Toledano, Carlos & Calle, Abel & Antuña Sánchez, Juan Carlos & Vaquero-Martínez, Javier & Antón, Manuel & Baraja, Ángel. (2022). Integrated water vapor over the Arctic: Comparison between radiosondes and sun photometer observations. Atmospheric Research. 270. 106059. 10.1016/j.atmosres.2022.106059.
  • AboEl‐Fetouh, Y., O’Neill, N. T., Ranjbar, K., Hesaraki, S., Abboud, I., & Sobolewski, P. S. (2020). Climatological‐scale analysis of intensive and semi‐intensive aerosol parameters derived from AERONET retrievals over the Arctic. Journal of Geophysical Research: Atmospheres, 125, e2019JD031569.
  • Mölders, N. and Friberg, M. (2020) Using MAN and Coastal AERONET Measurements to Assess the Suitability of MODIS C6.1 Aerosol Optical Depth for Monitoring Changes from Increased Arctic Shipping. Open Journal of Air Pollution, 9, 77-104.


Eureka offshore oil platform provides continuous aerosols data recorded by CE318-TV12-OC (SeaPRISM) for NASA AERONET.

Keywords : Aerosols, photometer, water radiance, monitoring, ocean properties, ocean color, Earth observation, remote sensing, CAL/VAL, SeaPRISM.

February 9th 2022

Since 2002, more than 31 OC measurement sites have been integrated on the NASA AERONET OCEAN COLOR network through offshore fixed platforms and coastal platforms all around the world. Thanks to numerous collaborations between environmental sciences and energy industries such as discussed below, the number of Ocean Color measurement sites keeps growing.

In collaboration with University of Southern California (USC), the SeaPRISM site at the oil rig platform Eureka was installed in the Los Angeles Harbor and was initially operational in April 2011. CE318-TV12-OC (SeaPRISM) photometers  are part of the AERONET network of automated instruments designed to make automated measurements of aerosols around the world.

The SeaPRISM instrument has been modified to also view the ocean surface and measure ocean color remote sensing reflectance as well as the aerosol measurements. Data is currently flowing to NASA AERONET as well as NRL-SSC (The Naval Research Laboratory detachment at  Stennis Space Center (SSC), Mississippi) and Oregon State University (OSU) for matchups. Data has been collected routinely since June 2012 to date.

Continuity of the ocean color products between ocean color satellites is required for climate studies, as well as to enhance the operational products used in ecological monitoring and forecasting, such as accurately monitoring ocean water quality and determining changes along our coastlines. In addition, inter-satellite product comparisons are essential for data continuity into the future.

The JPSS (Joint Polar Satellite System) calibration and validation team has developed an infrastructure to evaluate VIIRS (Visible Infrared Imaging Radiometer Suite) Ocean Environmental Data Records (EDRs): routinely nLw(λ) and chlorophyll are evaluated against existing satellites data measurements. Ocean color products are based on nLw( λ) from which specific products of chlorophyll, backscattering coefficients, absorption coefficients, and diffuse attenuation coefficients  are computed.

Therefore the accurate radiometric retrieval of the nLw( λ) is considered essential for the production of any ocean color product. A web-based with the VIIRS data matching the satellite data from Platform Eureka SeaPRISM was created in order to provide reliable data. The CE-318 of the oil platform Eureka helps to validate the satellite data provided by VIIRS on the JPSS.

Here are some results performed recently by the CE318-TV12-OC (SeaPRISM) located at Platform Eureka depicting the Normalized Water-Leaving Radiance.

Figure 1: Measurements performed at AERONET-OC Eureka oil platform, California – Normalized Water-Leaving Radiance [Lw]N.
Figure 2: CE318-TV12-OC (SeaPRISM) on site Eureka oil platform, California (USA).


Curtiss O. Davis, Nicholas Tufillaro, Jasmine Nahorniak, Burton Jones, and Robert Arnone “Evaluating VIIRS ocean color products for west coast and Hawaiian waters”, Proc. SPIE 8724, Ocean Sensing and Monitoring V, 87240J (3 June 2013);


The implantation of CE318-T photometers on offshore and coastal platforms constitutes a major turning point for atmospheric and ocean color applications.

Keywords : Aerosols, photometer, water radiance, monitoring, ocean properties, ocean color, Earth observation, remote sensing, CAL/VAL, SeaPRISM.

17th December 2021

The main substances that affect the color of the ocean include dissolved organic matter, living phytoplankton with chlorophyll pigments, and non-living particles like marine snow and mineral sediments. Ocean color data have a critical role in operational observation systems monitoring coastal eutrophication, harmful algal blooms, and sediment plumes. Scientists rely on satellite observations to monitor Ocean Color (OC) parameters, such as chlorophyll a concentration (Chla) and inherent optical properties of water (IOP), to better understand the role of the ocean in the Earth’s climate.

However, the current satellite measurement systems can provide only coarse spatial resolution, with relevant lack of data.

Thus, AERONET Ocean Color saw the light of day in 2002. This new component of AERONET (NASA AErosol RObotic NETwork) aims at providing more data concerning satellites measurements as there is a lack of insights in the monitoring of marine aerosols and water radiance. Since 2002, more than 31 OC measurement sites have been integrated on the network through offshore fixed platforms and coastal platforms all around the world.

Its particularity is that the measurements are taken from the radiance emerging from the sea using CE318-TV12-OC (SeaPRISM) Cimel photometers. By measuring the water radiance from the sea with instruments installed on coastal/offshore platforms or boats, Cimel improves the accuracy of satellites measurements. AERONET decided in 2015, after full validation, to accept only the CE318-T for new photometers entering the network. Below is a representative drawing of the measurement principle of the CE318-TV12-OC (SeaPRISM) photometer:

Figure 1: Measurement principle of the Cimel CE318-TV12-OC (SeaPRISM).

Many missions are conducted by AERONET-OC to collect ocean color data and measurements. Below, one of these campaigns conducted on an offshore platform (AAOT) in the Adriatic Sea.

Figure 2: AERONET OC site located in the Acqua Alta Oceanographic Tower (AAOT) in the Gulf of Venice in the Northern Adriatic Sea in July 2018.

Figure 3: Measurements performed at AERONET-OC AAOT – Scatterplot of LIOP WN(λ) versus LChla WN(λ).

Click Here to read the article!

Citation: Zibordi, Giuseppe, Brent N. Holben, Marco Talone, Davide D’Alimonte, Ilya Slutsker, David M. Giles, and Mikhail G. Sorokin. «Advances in the Ocean Color Component of the Aerosol Robotic Network (AERONET-OC)”, Journal of Atmospheric and Oceanic Technology 38, 4 (2021): 725-746, accessed Sep 17, 2021,

ESA – New remote sensing tech on satellite for atmospheric measurements

VEGA Rocket

ESA – New remote sensing tech on satellite for atmospheric measurements


On September 3rd 2020, ESA has launched 42 small satellites aboard a Vega rocket from Kourou in French Guiana for the Copernicus Project.

This new type of satellites capable of measuring CO2 emissions to the nearest kilometer and pinpointing their origin.

One of these nanosatellites, PICASSO, carries remote sensing technology developed which will be used to undertake measurements in the upper layers of Earth’s atmosphere.

PICASSO stands for Pico-Satellite for Atmospheric and Space Science Observations and it’s the first CubeSat nanosatellite mission of the Royal Belgian Institute for Space Aeronomy.

Weighing only 3.5kg, it carries two measuring instruments for atmospheric research: A Visible Spectral Imager for Occultation and Nightglow (VISION) and a system to conduct plasma measurements in the ionosphere, the Sweeping Langmuir Probe (SLP).

This project of analysis and collection of satellite data will be carried out over 5 years. The aim is to obtain as much precise information as possible on the quantification of gases in the air.

We will be able to know exactly the real CO2 emission by country, cities and the origin of gases (if it’s anthropogenic or natural).

Thanks to this initiative, more and more surveillance systems will be sent into space over the next few years, which will help develop the market for remote sensing solutions.

Cimel will be part of this development by bringing additional data thanks to its photometers and LiDARs to help calibrate and validate data from satellites.

Credits: ESA-M. Pedoussaut

Earth Observation Satellites & Ground Monitoring  Solutions – an essential synergy for Air Quality and Climate Change

Earth Observation Satellites & Ground Monitoring  Solutions – an essential synergy for Air Quality and Climate Change

April 30, 2020

Atmospheric monitoring and climate analysis are strategic missions in order to improve the understanding of air quality dynamics and climate change evolutions. This in turn is a pre-requisite for providing reliable information reports with real data measurements and to help decision makers and end-users to understand the impacts and causes of air pollution with atmospheric impacts and to act upon it.

Satellite data is key for atmospheric and climate monitoring by providing a continuous and global view of the Earth parameters. These data are essential inputs for forecast models by improving their accuracy.

By combining satellite observations with models of the atmosphere and measurements from ground-based instruments, like Cimel Remote Sensing Solutions, it is possible to measure accurately and forecast aerosols (particles suspended in the air), as well as quantify gases level (ozonenitrogen dioxidesulphur dioxidecarbon monoxide…) and several other kind of environmental parameters (planetary boundary layer, water leaving reflectance for Ocean color, solar radiation, water vapor, atmospheric concentration profiles PM2.5/PM10…).

Cimel solutions keep working continuously and automatically, to help the calibration of satellite instruments and validate their data. Furthermore, Cimel is always active to support the various research activities from the worldwide scientific community.

In this video, different aerosols are highlighted by color, including dust (orange), sea salt (blue), nitrates (pink) and carbonaceous (red), with brighter regions corresponding to higher aerosol amounts.

See more on:

Credit: NASA Goddard Space Flight Center



Aerosols, these tiny particles of the lower atmosphere, are one important component of atmosphere affecting climate (radiative effects, water cycle) and air quality.

For characterizing and monitoring aerosols, water wapor and clouds, LOA and Cimel, in collaboration with NASA’s GSFC, developed the robotic solar photometer for the AERONET network in the early 1990s. The meeting between CNRS and NASA researchers and the industrial company Cimel led to the definition of an automatic, robust, autonomous solar photometer that transmits its data by radio, providing AOD and particle size in real time. In 1998, the French component (PHOTONS) was awarded the INSU Observation Service label.

Cimel is NASA – AERONET’s exclusive supplier of automatic Sun Sky Lunar photometers (CIMEL CE318-T) operating in near real time and providing aerosol optical and columnar microphysical properties.