The EarthCARE cloud monitoring satellite has been delayed by more than 10 years in flight

finally. The EarthCARE satellite is scheduled to launch on Tuesday, May 28, from Vandenberg Base in California (USA) to study clouds in the Earth's atmosphere. The mission, led by the European Space Agency (ESA) in cooperation with the Japanese Aerospace Agency (JAXA), will last for at least three years. “We see clouds every day, but we don't understand how precisely each type of cloud interacts with radiation from the sun.”“, explains Kutska Wallace, EarthCARE mission and photonic payload manager. The 2.2-ton satellite, which will be placed in orbit 390 kilometers above the Earth, will be responsible for studying the interior of these droplet clusters, from the largest to the thinnest.

4 tools for dissecting clouds

Cumulus, stratocumulus, cirrus… The composition of clouds varies depending on their height. Thus, they behave differently on the climate: some, such as high-altitude cirrus clouds, which are composed of ice, allow solar radiation to pass through, warming the Earth. Others, such as cumulonimbus clouds, which are composed of water vapor and located at low altitudes, on the contrary, cool the atmosphere by reflecting solar radiation back into space. To analyze the structure of the clouds in detail, the EarthCARE satellite will take a vertical slice of the clouds — a view that no other satellite has yet provided, according to the European Space Agency.

To accomplish this feat, the satellite was equipped with four instruments. The Lidar device – detection by laser imaging and ranging – developed by Airbus, will make it possible to analyze microclouds and identify aerosols. “The lidar emits pulses of ultraviolet light that last 26 nanoseconds. We can then calculate the location of each group of molecules or particles in the cloud based on the time it takes for the light to return.he explains Kutska Wallace. Lidar also makes it possible to infer the origin of the cloud. It determines, for example, whether a group of particles comes from desert dust, or whether it contains a high concentration of salt and therefore comes from the ocean, a volcano, or even from human pollution.

Lidar, on the other hand, cannot analyze thicker clouds. The Japanese space agency JAXA was responsible for equipping the satellite with a cloud profiling radar (CPR). It will make it possible to peer through opaque cloud layers to determine their liquid and solid water composition. The speed of the particles contained in the clouds will also be measured. A radiometer, provided by Thales Alenia Space, will measure the temperature of the clouds, while a multispectral imager will provide information about their shape.

We are 10 years late in the complex development of lidar

The project is now more than ten years late. The European Space Agency turned to manufacturer Airbus in 2008 for an initial sum of €263 million and is scheduled to launch in 2013. “The entire project, including the construction of the satellite and the launch, cost us 800 million euros with a cost increase of 80% compared to the initial budget.”says Kutska Wallace, who has been working on the project for 17 years. Among the culprits: selecting ultraviolet light from lidar. “UV allows us to achieve better resolution. But it also tends to darken the lenses if there is the slightest dust on the glass. However, the UV signal used in this lidar is very strong, which amplifies this phenomenon.”

As for take-off, the satellite also suffered disappointments. The launch was scheduled to take place from a Russian Soyuz launch pad, before being suspended in March 2022 after the Russian invasion of Ukraine. The European agency then turned to the Vega rocket from the European manufacturer ArianeGroup. The launch model found itself stranded on the ground after defects were discovered and the first commercial flight failed. Finally, the European Space Agency has set its sights on SpaceX's reusable American Falcon 9 rocket.