The joint European-Japan EarthCARE satellite began its mission to improve our understanding of Earth’s climate on Tuesday, launching atop a SpaceX Falcon 9 rocket. The launch from Space Launch Complex 4E (SLC-4E) at Vandenberg Space Force Base in California took place at 3:20 PM Pacific Time (10:20 UTC).
The Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) is a joint project between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), and the sixth Earth Explorer mission to be launched as part of ESA’s Living Planet Program . The satellite, which has also been given a name Hakuryu – or white dragon – from JAXA, is carrying four instruments that will study clouds and aerosols – fine particles and liquid droplets floating in Earth’s atmosphere – and how they affect the planet’s climate.
By bringing together a range of different instruments on one satellite, EarthCARE can make different types of measurements that complement each other, allowing scientists to better understand how clouds and atmospheric aerosols interact with solar radiation and how this affects solar radiation. the planet’s radiation balance – the difference between the energy the Earth gets from the sun and what it radiates into space.
Scientists have long known that clouds have an impact on Earth’s radiation balance, both in terms of reflecting sunlight back into space and absorbing heat that would otherwise be radiated into space. The height and structure of the cloud, its water content, and the presence of different types of aerosols can change how it interacts with this system. By providing a complete picture of the internal structure of clouds, EarthCARE will help refine models used to predict changes in Earth’s climate.
The 2,200 kg EarthCARE satellite was developed by a multinational consortium, with Airbus Defense and Space as prime contractor. The power for the mission will be generated by a single deployable solar panel with a length of 11 meters. The satellite is expected to operate in a circular, sun-synchronous orbit at an altitude of 393 km and an inclination of 97 degrees for a minimum of three years.
Development of the satellite began in 2008, with the signing of a contract between ESA and Astrium Satellites, which became part of Airbus in 2013. The four instruments were built separately before being shipped for integration with the rest of the spacecraft. The tests were carried out at the European Space Research and Technology Center in the Netherlands, before final checkouts at the Airbus factory in Friedrichshafen, Germany. The satellite was shipped to the launch site in March 2024.
EarthCARE’s four instruments consist of an atmospheric LIDAR (ATLID), a cloud profiling radar (CPR), a multispectral imager (MSI) and a broadband radiometer (BBR). Atmospheric LIDAR (light detection and ranging) is used to measure the height of cloud tops and aerosols. The instrument uses a laser, which emits 26 nanosecond ultraviolet pulses with a wavelength of 355 nm, and a 62 cm telescope as a receiver. The pulses from the laser are sent into the atmosphere, where they are scattered by particles and water molecules. Some of this will be reflected back to the receiver, with the return time used to calculate the height at which scattering occurred. Comparing the wavelength of the scattered light to the emitted light will also help determine the type of scattering that occurred and therefore deduce which type of particle caused the scattering.
The ATLID instrument on board EarthCARE was built by Airbus and has a mass of approximately 500 kg.
CPR allows EarthCARE to penetrate clouds and collect data about their vertical structure. This instrument is a key part of JAXA’s contribution to the mission and was built by Japan’s NEC Corporation. CPR uses millimeter-wave Doppler radar, which sends 3.3 microsecond pulses into the atmosphere at a frequency of 94 gigahertz. Backscattered signals are received using the instrument’s 2.5 m antenna. In addition to determining the internal structure of the clouds, studying how the signal is Doppler shifted will also allow measurements of the vertical motion of the cloud and elements of its structure.
LAUNCHING SOON🚀🛰️
The #EarthCARE satellite has four instruments for cloud and aerosol observations with four synergistic detection methodologies.
The instruments provide key measurements to answer critical scientific questions regarding the role that clouds and… pic.twitter.com/4GqCnoNRve
— ESA Earth Observation (@ESA_EO) May 26, 2024
BBR, built by Thales in Britain, consists of three telescopes that measure the radiation flux detected from Earth. One of its telescopes points in the nadir direction – that is, directly down towards Earth – while the others focus on points along the satellite’s track that are ahead and behind its current position. This allows observations of the same point to be made from three different angles as the satellite moves along its orbit.
Each telescope has a single mirror and a linear sensor. A rotating chopping drum alternates the telescope’s view between unfiltered light, a filter that allows only shortwave radiation to pass through, and a constant temperature surface to maintain calibration.
The shortwave filter limits BBR measurements to only radiation from the sun reflected by the Earth. By subtracting this value from the total value without the filter, the amount of long-wave radiation emitted by the Earth itself can be calculated. These measurements are important for monitoring the planet’s radiation balance.
MSI is an imaging system consisting of two separate cameras with a common electrical and control segment, developed by Surrey Satellite Technology Ltd in the United Kingdom. A thermal infrared camera operates in three different wavelength channels, while a second camera produces images in visible, near-infrared and two short-wave infrared channels. Observations using MSI support data from EarthCARE’s other instruments by providing context to the data collected by ATLID and CPR and spectral data to help calibrate BBR’s measurements. MSI has a resolution of up to 500 m and covers a swath of 150 km of the Earth’s surface.
The EarthCARE satellite, pictured being removed from its shipping container after arriving in Vandenberg. (Credit: ESA)
EarthCARE will be launched by SpaceX aboard a Falcon 9 rocket, a two-stage vehicle consisting of a reusable booster and an expendable second stage. The launch will take place from Space Launch Complex 4E (SLC-4E) at Vandenberg Space Force Base in California.
The booster used for the EarthCARE mission is B1081.7, which made its seventh flight with this launch. The B1081 flew for the first time on August 26, 2023 with Dragon on board Stamina on the Crew-7 mission to the International Space Station, followed by the CRS-29 Cargo Dragon mission in November. After launching a group of Starlink satellites in December, the fourth launch put NASA’s PACE satellite into orbit in February. The B1081 was then used for the Transporter-10 rideshare launch in March, which marked the first launch from Vandenberg, before the most recent mission, another Starlink launch, on April 7.
ESA had originally selected the Soyuz rocket to deploy EarthCARE, with the launch to be carried out by Arianespace from the Center Spatial Guyanais in Kourou, French Guiana. After the Russian invasion of Ukraine in 2022, Arianespace’s partnership with Russia to conduct Soyuz launches ended and the launch was moved to the new Vega-C rocket. This was subsequently changed again in 2023 to Falcon 9, a decision made due to delays following the failed launch of Vega-C in December 2022, and due to changes that would have been required to the payload fairing to accommodate the EarthCARE satellite.
Falcon 9 flew a return-to-launch-site (RTLS) profile, with the first stage successfully returning to land at Landing Zone 4 (LZ-4) close to the launch pad after completing its role in the mission from Tuesday. The ability to recover and reuse the first stage has contributed greatly to the success of Falcon 9: since its maiden flight in June 2010, it has already established itself as one of the most flown rockets ever built. By some metrics, EarthCARE will mark the 350th flight or mission of the Falcon 9 and Falcon Heavy family: the first if the 2020 suborbital Crew Dragon In-Flight Abort (IFA) test is included in the count; and the latter if the 2016 Amos 6 mission, in which the rocket exploded on the launch pad while preparing for a static fire test two days before the scheduled launch, is included instead.
Despite its high flight speed, Falcon 9 has also proven to be one of the most reliable rockets in use. Apart from Amos 6, it has had only one in-flight failure and one additional partial failure to date, and has performed 320 consecutive successful launches since Amos 6 on the Falcon 9 and Falcon Heavy vehicles – the latter using two additional boosters which burn in parallel with the first stage to launch heavier payloads into higher orbits.
Render of the second stage of Falcon 9 and EarthCARE, upon fairing separation. (Credit: ESA/P. Carril)
For Tuesday’s mission, the single-core Falcon 9 will be sufficient to carry EarthCARE into its planned sun-synchronous orbit, with enough performance left to enable the booster’s return to the launch site. Falcon 9 uses RP-1 kerosene propellant with liquid oxygen (LOX) as the oxidizer. Propellant and LOX loading will occur during the final 35 minutes of the countdown, with the first stage’s nine Merlin-1D engines igniting approximately three seconds before the scheduled launch time, or T0. After takeoff, Falcon will fly a southerly downward course.
The first stage will power the ascent for approximately two and a half minutes before shutting down, separating and beginning the flight back to LZ-4. The second stage will ignite the Merlin Vacuum engine – a version of the Merlin optimized for use in space – to continue the mission. Shortly thereafter, the payload fairing will detach from around EarthCARE near the nose of the rocket. The second stage will burn for just over six minutes to reach EarthCARE’s planned orbit, with the spacecraft separating approximately ten minutes after launch.
Once separated from the Falcon 9, EarthCARE will need to deploy its solar panels and other key systems and begin testing and commissioning in space before it can be put into service.
(Main image: Falcon 9 B1081-7 time-lapse image of the EarthCARE launch from Vandenberg Space Force Base. Credit: Pauline Acalin for NSF)