ESA and SpaceX Prepare to Launch EarthCARE

The European Space Agency (ESA) and SpaceX are preparing to launch the long-anticipated EarthCARE mission on May 28, 2024, set to improve climate models and weather forecasts by studying Earth’s radiation budget in new detail. EarthCARE’s studies are split into three main domains: Clouds, Aerosols, and Radiation. By characterizing these three components and their interactions, EarthCARE hopes to provide a new enhanced data set to dramatically improve models of our planet’s climate and weather.

EarthCARE stands for Earth Cloud, Aerosol, and Radiation Explorer, which are the primary science topics of the mission. Radiation is the core phenomenon at play, and refers to the thermal energy from the sun that constantly bathes the Earth. The combination of reflection, scattering, absorption, and re-radiation back into space forms Earth’s radiation budget. The radiation budget determines how much solar energy is absorbed by Earth to heat it up overall. While most energy inside the radiation budget is moved around based on interaction with the surface, both clouds and atmospheric constituents are significant intermediaries in both directions. Radiative forcing is a measure of the impact of specific factors, such as clouds, greenhouse gasses, land use, aerosols, and so on on the radiation budget.

Aerosols are solid particles or liquid droplets suspended in the air or other gasses. Examples include Sulfur Dioxide, soot, dust, various types of nitrates, and sea salt. Clouds share some similarities to aerosols, being made of water droplets and ice crystals suspended in the air, but differ by being made almost exclusively of water and being much more optically dense. This lets them provide meaningful shadowing to surface and atmospheric areas underneath them. Clouds are also often seeded by aerosols, with those small particles sticking to water vapor in the air and providing a platform to condense around.

Because clouds and aerosols both reflect the Sun’s radiation back into space, they are a critical element of Earth’s dynamic weather and climate. In order to make accurate predictions, understanding the quantity, distribution, and precise effects of different aerosols are vital. However, it is these exact data points that have the largest error bars in current prediction models. 

Clouds are extremely variable, with thickness, shape, composition, precipitation, altitude, and coverage area able to completely change within minutes to hours. The exact microscopic details and 3d structure of the clouds has a huge effect on whether they result in heating or cooling overall, so the ability to profile them thoroughly is critical for improving radiation budget predictions and models.

Aerosols do not serve a role as large as clouds, but still have non-trivial climate impacts. They can reflect radiation back into space, as has been seen in the cooler periods that often follow large volcanic eruptions and their release of massive amounts of sulfur dioxide.

Due to the role of aerosols in the formation of clouds and the importance of the minute details of cloud structure and composition for their radiative forcing impact, it is critical to look at the interactions between them to enable better climate change assessments and short range weather forecasting.

To achieve this, EarthCARE will create 3d maps of the distribution, composition, and other details for clouds and many types of aerosols and correlate them to measurements of both incoming and outgoing solar radiation. For the first time, a spacecraft will be able to observe the entire radiation budget simultaneously. We will be able to see what types of aerosols and what cloud setups are better at cooling or warming, to inform potential mitigations and even atmospheric modifications.

The mission is a collaboration between ESA and the Japan Aerospace eXploration Agency (JAXA). ESA provides the spacecraft bus, the launch, and 3 out of 4 science instruments, and operates the mission. JAXA provides the fourth instrument, the Cloud Profiling Radar. It was originally manifested to launch on an ArianeSpace Soyuz from the Guiana Space Centre, but after the Russian invasion of Ukraine, it was remanifested to a Vega-C. Vega-C, in turn, suffered a launch failure on December 21st, 2022 and a subsequent investigation. To preserve the schedule, EarthCARE was then moved to Falcon 9.

EarthCARE is the 6th mission in ESA’s Earth Explorers series. Earth Explorers is ESA’s line of earth science research satellites, akin to NASA’s fleet of earth observation missions. 10 Earth Explorers have been selected for flight to date, with an 11th to follow next year. Previous notable missions include GOCE, a gravity and ocean current mapping mission between 2009 and 2013, unique because of its very low 255 km orbit and ion thrusters to compensate for the significant drag at that altitude, and Aeolus, a 2018-2023 mission using lasers to measure wind speeds and contribute to weather forecasts.

While many earth observation missions for the past 50 years have featured radiation budget payloads, such as NASA’s Nimbus, Terra, and Aqua satellites, they focused primarily on measuring the difference between incoming and outgoing energy. Such missions could not probe the atmospheric details in the same way as EarthCARE and so could not offer the full picture, though they did a lot to point in the right direction. Only now are we ready to probe the heart of the radiation budget and explore to the fullest its ramifications for our climate and health.

Acronyms:

ESA – European Space Agency

JAXA – Japan Aerospace eXploration Agency

EarthCARE – Earth Cloud, Aerosol, and Radiation Explorer

GOCE – Gravity and Ocean Circulation Explorer

Edited by Beverly Casillas and Scarlet Dominik