How do clouds and aerosols affect our climate?

After 20 years of thorough planning and preparation, the European Space Agency (ESA) Earthcare mission is currently in flight, already creating interesting data. I spoke to Mission Manager Björn Frommknecht to see the details.

Launched in 2024, ESA’s EarthCare mission is designed to revolutionize our understanding of global observations of clouds, aerosols and radiation, and to help us to revolutionize our understanding of how these factors affect our climate. EarthCare aims to quantify the interactions of cloud aerosol radiation, which could be correctly included in climate and numerical weather forecasting models. To achieve that goal, satellites have four instruments and measurements, and worldwide measure the vertical structure and horizontal distribution of clouds and aerosol fields along with outgoing radiation.

The EarthCare satellite successfully traveled to space on May 29, 2024, riding a Falcon 9 rocket from the Vandenberg Space Force Base in California, USA. Following the commissioning phase, the first phase of the data was made public in January 2025.

To learn more about the importance of the mission, its complexity, and the findings so far, editor Georgie Purcell spoke with EarthCare Mission Manager Björn Fromknecht.

Can you easily summarise EarthCare missions and their main objectives?

EarthCare is a collaboration project between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA). The main purpose of the EarthCare mission is included in the name. It is an Earth Observation Mission, with Care short for Cloud, Aerosol and Radiation Probe.

We are investigating the role of clouds and aerosols, their interactions with radiation from the sun, and radiation from the Earth. To achieve that, fly four equipment: Atmospheric Lidar (ATLID), Cloud Profiling Radar (CPR), Multispectral Imager (MSI), and Broadband Radiometer (BBR). One of the active sensors, Cloud Radar, was presented by Jaxa. Collaboration between space agencies and instruments is essential to this mission.

EarthCare is very special for a number of reasons. The mission was chosen in 2004, so it took a long time. It’s truly cutting-edge technology, and today ESA is the only agent to fly such atmospheric riders in space. We are progressing in Europe and that is something we can really be proud of. This achievement was possible only for the efforts of a great Earthcare team facing many challenges. I have never met a team that is more dedication, integrity, or professional than EarthCare’s. Of course, collaboration with Jaxa has helped a lot, not only with the European industry.

For many years, the mission has faced significant delays caused by major events, such as the 2011 Tohoku earthquake and tsunami, which destroyed the chip factory where some of the cloud profiling radar was built, and destroyed the chip factory that delayed the project several years. Another challenge was caused by the war in Ukraine as it was originally scheduled to take place on the Russian Soyuz rocket. After a fierce testing process, it successfully booted up on a SpaceX Falcon-9 rocket instead.

Why is it so important to shed light on the role clouds and aerosols play in regulating the Earth’s climate?

To predict how Earth’s climate will evolve, certain assumptions must be made about cloud and aerosol behavior, interactions with solar radiation, and Earth’s thermal radiation. However, there is still a lot of uncertainty surrounding this. The improvements we can make regarding this uncertainty will immediately benefit the accuracy of our climate model, particularly for long-term forecasts.

What is the importance of the four instruments used in missions?

There are two active sensors that emit radiation and can actively scan targets. Atmospheric riders are like laser pointers that emit UV light to measure distance. Measure distances and detect and profile aerosols such as dust clouds, industrial pollution, seawater, steam and more. The profiling feature allows you to discover vertical structures.

Cloud profiling radar is similar, but in the case of clouds, you can detect clouds and see the structure inside. Vertical motion can be detected, allowing you to see if anything in the cloud leaves or moves towards the satellite. If it moves, it’s precipitation. This means that the rain in the clouds can see where it rains. This is also very important information for numerical weather forecasts.

To further classify the profile, there are multispectral imaging instruments. The field of view of these active sensors, known as swaths, is relatively small (1km for cloud profiling radar and 30m for riders). Imagers with a 150km band can collect more contextual information.

The fourth device is the radiometer. At the end of the processing chain, we extend the vertical profile to 10x10km and 10km high cubes with small footprints, simulating radiation at satellite locations if the assumptions about how clouds and aerosols interact with radiation from the Sun and Earth were true. The main strength of Earthcare is that these four sensors are measured at the same time in the same place. Previous missions from other major space organizations, such as NASA’s A-Train, have used several sensors on different satellites and are flying one after another. However, as the weather changes very rapidly, even just a few seconds can make a difference. We are the only ones who can measure everything in one place, in one place. Next, compare the measured radiation with what you think should reach the satellite’s position. This difference will help you understand how clouds and aerosols interact with radiation. This information can be provided to both weather and climate models.

What were the key findings from previous missions?

Last October, Synergistic Images was released. These show that only by using both active sensors together can we obtain a full picture including the structure and radiating parts of the cloud and aerosol. Already, we have been able to see where the atmosphere heats or cools the Earth’s climate. This is a preliminary result achieved just six months after its launch, but scientists are already very excited. This is proof of the concept that both sensor quality is as expected and there is a very high chance of achieving the scientific results we are aiming for. Level 1 data was published in January, followed by Level 2 data in March. Already, the results are extremely promising.

Have you encountered any difficulties since it was released? If so, how have they been overcome?

One of the main challenges immediately after the launch was preparing a calibration and verification campaign. Measurements must be externally verified and adjusted. This can be achieved by using planes flying under satellites. Satellites are much faster than planes – planes fly at 900 km/h, while flying at 7 km/s. You need to be in the right place at the right time. There were six major calibration campaigns, a collaboration between many European countries and the US. It was a monumental effort and a very good example of collaboration.

These campaigns require careful and thorough planning. There was a target date where the instrument was very well defined to be ready to compare measurements. That was a big challenge. The radar, imager and radiometer were very fast and we ran faster than planned, but the Atrid was ready with the day’s margin. It was a very interesting and very intense experience. Again, it was a great collaboration between the industry, ESA, and Jaxa.

For ATLID, certain steps must be followed to ensure that the aerosol reflects light is at the center of the receiving telescope. This was a success, and the instruments were so well tuned that they had to readjust the ground and airborne equipment.

What’s next for the mission? When do you expect it to end?

The first batch of level 2 data was released on March 17th. These are single-sensor and two-sensor products. The more you go into the processing chain, the more sensors you will combine to generate the product. By the end of the year, we will release a fully synergistic product with the synergy of three sensors. These are the next major milestones.

Our life-limiting factor is the use of propellants, as it means a height of 400km, as it needs to fly relatively low. The lifespan of the nominal mission is three years from May 2027 to bring us, but it shows that we can extend our lifetime subject to approval from Member States.