Clouds and aerosols, and their contribution to Earth's energy balance, are already less mysterious after the Earth Cloud, Aerosol and Radiation Explorer's first year in orbit.
EarthCARE, also known as Hakuryu (“White Dragon”), a collaboration between the European Space Agency and the Japan Aerospace Exploration Agency (JAXA), was launched just after midnight CEST on 29 May 2024.
It was a nerve-wracking moment for all those who spent over two decades developing a satellite whose fate rested at the tip of a rocket, but the successful launch marked a new beginning for ESA's most complex Earth Explorer satellite yet.
For the first time from space, we could measure the speed of falling snow and rain, and plenty more. From spectacular polar stratospheric clouds to immense international collaboration and even swarms of insects and phytoplankton, here are five things we have learned thanks to EarthCARE this year.
1. Working together for EarthCARE
Launching a single satellite instrument is a remarkable technical achievement, let alone four. Going a step further still, EarthCARE's innovative instruments all work in combination.
The first to be fired up was the Cloud Profiling Radar (CPR), which was developed by JAXA, unveiling the internal structure and dynamics of clouds for the first time from space.
That was quickly followed by the Broadband Radiometer (BBR) shedding light on Earth's energy balance, the Multispectral Imager (MSI) putting clouds into context, and the Atmospheric Lidar (ATLID), which provides detailed profiles of atmospheric particles from sea spray to cloud tops.
Within just a few months of launch, the instruments were working together to measure how much clouds and aerosols heat and cool the atmosphere.
With the satellite working well, the critical data must then get to those who use EarthCARE data to improve weather forecasts and climate models.
This requires not only technical expertise but excellent international collaboration, between ESA and JAXA, and the 16 organisations spanning 9 countries comprising the EarthCARE data, innovation and science cluster (DISC), whose algorithms are used to process the data to produce a range of science products that benefit end users.
There is also the calibration and validation community of hundreds of researchers, who have flown from the Arctic Circle to Cabo Verde, and sailed across the Atlantic Ocean, to make sure EarthCARE data are reliable and accurate.
At the 2nd In-Orbit ESA-JAXA Calibration and Validation Workshop in March 2025, we learned that all the hard work was worth it, and the early results have been hugely promising.
2. EarthCARE is making an impact
With EarthCARE orbiting at a relatively low altitude of around 400 km, the satellite does not have long in space as space weather, our planet's soupy atmosphere and gravity combine to drag the satellite back down to Earth.
We must make the most of this hard-fought opportunity. The satellite's nominal time in orbit is three years from launch, but current predictions indicate a longer mission lifetime may be possible (subject to approval, and solar activity).
Thankfully, EarthCARE is already making an impact.
In January 2025, Level 1 data became available to the public for the first time. In early spring, Level 2 data were released, meaning that 26 out of 33 products were already available to the science community within 10 months of launch.
Forecasters are working hard to assimilate EarthCARE data into weather models, which will benefit immensely from EarthCARE's observations of clouds and their radiative effects. The hope is that they will reduce biases, and therefore inaccuracies.
DISC partner ECMWF wrote a detailed look at EarthCARE's early impacts to date in their spring newsletter, which details many of the satellite's unique contributions – from better understanding of cloud microphysical properties and processes informing physical models, to direct data assimilation from EarthCARE's radar and lidar measurements.
Those interested in a comprehensive explanation of how EarthCARE can improve models and forecasts can visit a dedicated website that explores EarthCARE science.
Early results suggest that data assimilation from EarthCARE improved cloud positions, mid-level convection, cloud amount and the positions of an occluded front across several case studies.
EarthCARE also tracks smoke from wildfires and provides the most precise ever evaluation of air quality forecasts.
ECMWF aims to assimilate EarthCARE data into operational forecasts as soon as possible, and if the incredible success of assimilating data from Aeolus – which carried a similar lidar instrument – is anything to go by, the results will be highly anticipated.
In the meantime, the global atmospheric science community is already gaining unique insights into atmospheric processes.
3. Cloud observations are exciting scientists
Almost as soon as EarthCARE's Level 1 data products were released, scientists were purring over the satellite's observations of polar stratospheric clouds (PSC).
These high-altitude clouds are both spectacular and mysterious, their iridescent hues providing a marvel for polar sky gazers and atmospheric researchers alike.
EarthCARE allowed us to observe a rare band of “type II” PSCs, which stretched approximately 3,000 km from Latvia to Greenland at heights of between 20 and 30 km. More common over Antarctica, this offered scientists the opportunity to compare PSCs over either pole, offering unique insights into their distribution, occurrence, and profiles.
There was tangible excitement at the 2nd In-Orbit ESA-JAXA Calibration and Validation Workshop about the use of EarthCARE Level 1 data for studying the stratosphere, including observations of sulphate aerosols injected into Earth's atmosphere following a volcanic eruption, so we're excited to see more results as the satellite completes a year in orbit.
4. EarthCARE adds precise new measurements to space-based radiation observations
According to a recent article in AGU Advances, Earth’s energy imbalance is increasing at a rate twice that predicted by climate models.
The letter, authored by several scientists amongst the EarthCARE community, notes the importance of satellites to continue to monitor such an alarming trend to help understand the underlying causes.
Satellites like EarthCARE are critical in this regard. In EarthCARE’s case, the BBR instrument, which provides accurate measurements of the reflected solar and emitted thermal radiation that are collocated with other EarthCARE measurements.
The BBR instrument uses solar and thermal channels to capture Earth with unprecedented spatial resolution. As it observes Earth in three directions (forward, backward, and straight down), it can very accurately estimate how much sunlight is reflected and how much heat is emitted by clouds, aerosols and other features of Earth.
These BBR measurements are used to continuously evaluate radiative transfer computations -models of how energy in the form of electromagnetic radiation moves within Earth’s atmosphere- that us clouds and aerosols retrieved by EarthCARE as input. Generally, the agreement between them for thermal radiation is within 10 W/m^2.
An example of the BBR instrument’s power was shown recently after a month of severe rainfall in the Iberian peninsula.
The EarthCARE DISC team used the Level-1 B-SNG product of the BBR, as well as the MSI instrument, to capture unique insights into a major thunderstorm system observed on 11 March 2025.
Taken globally, along with information from EarthCARE’s other instruments to connect the radiation with underlying processes, scientists can better understand the role of clouds and aerosols in regulating Earth’s energy balance.
5. EarthCARE can spot a lot more than just clouds and aerosols!
ESA’s Earth Explorers, as well as being excellent at their primary objectives, often have a trick or two up their sleeves (or structural frames).
In March 2025, as EarthCARE passed over the Himalayas and Uttar Pradesh in Northern India, it detected a cloud of insects 500 km long. The weak signal in the CPR data, visible up to about 2 km above the ground, was first classified as liquid clouds and drizzle. However, when ATLID and MSI data are considered, it is clear that CPR’s initial classification of cloud was incorrect.
ATLID observes layers of continental pollution and dust, and MSI colour images confirm that the area is almost entirely cloud-free.
So how did the scientists know that this must be insects?
The CPR is most sensitive to objects on the millimetre scale -usually we’re thinking about raindrops and snowflakes- but in some parts of the world millions of insects, each up to a few millimetres in size, can be lofted up into the lower atmosphere as high as around 2 km on a warm afternoon.
ATLID, on the other hand, is sensitive to high concentrations of smaller particles like dust or smoke, tiny ice cloud particles, and especially liquid cloud droplets, so relatively low concentrations of insects will be invisible to the lidar.
While layers of pollution and dust seen by ATLID can co-exist with the insects seen by CPR, there’s no situation in which CPR would see a layer of drizzle that wouldn’t be accompanied by a strong cloud signal from ATLID. Therefore, we conclude that the CPR signal must have been from a vast plume of insects.
Insects, and even birds, are frequently observed by ground-based precipitation radars, but they have not been regularly studied with previous generations of spaceborne radars. EarthCARE’s CPR is now detecting insects in cases like this as often as several times a day, so we look forward to learning more about what insects we’re detecting, and how their distributions may change with the seasons.
Another useful spin-off of EarthCARE might be measuring ocean phytoplankton. EarthCARE’s atmospheric lidar uses two channels to measure the amount of light backscattered from atmospheric molecules like nitrogen and oxygen (Rayleigh) separately from atmospheric particles like dust or cloud droplets (Mie).
At the ocean surface, backscatter from ATLID is detected mainly by the Mie channel, but below the ocean surface, liquid water molecule scattering is detected mainly by the Rayleigh channel. This makes the Rayleigh channel ocean signals sensitive to subsurface scattering, which is influenced by the concentration of chlorophyll-a, a key pigment in phytoplankton.
Chlorophyll-a strongly absorbs ultraviolet (UV) radiation, the same as the ATLID wavelength of 355 nm which leads to a measurable decrease in Rayleigh channel ocean signals as chlorophyll concentrations (and hence absorption) increase.
Ocean regions with higher chlorophyll-a levels therefore exhibit lower Rayleigh-channel signals.