The Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) mission, is the sixth Earth Explorer Mission of the European Space Agency ESA in cooperation with the Japan Aerospace Exploration Agency (JAXA). With its payload, consisting of 2 active and 2 passive instruments, it will provide data to improve the understanding of the processes involving clouds, aerosols and radiation in the Earth’s atmosphere, addressing uncertainties in global models for climate predictions but also strong weather events in numerical weather prediction.
Flying in a sun-synchronous orbit at 393 km altitude with a 14:00 descending node, the mission produces data from the 4 co-aligned instruments, an Atmospheric UV LIDar (ATLID), a Multi-Spectral Imager (MSI), a Broad-Band Radiometer (BBR) and JAXA’s Cloud Profiling Radar (CPR). This payload data is processed individually and in a synergetic manner by the ground segment into a large number of EarthCARE data products which include among others vertical profiles of aerosols, liquid water and ice, observations of cloud distribution and vertical motion within clouds.
After years of development, manufacturing, integration and testing, and overcoming technological and technical challenges, the EarthCARE satellite has been integrated and functionally tested at the facilities of the prime contractor, Airbus Defence and Space GmbH in Friedrichshafen (Figure 1). It is currently being prepared for the environmental test campaign. All teams, covering the satellite, launcher, operations, ground segment, mission data processing and products generation, validation and scientific exploitation are currently in full preparation for the EarthCARE launch in 2023 and subsequent commissioning and exploitation phases.
This paper will present a general overview of the EarthCARE mission, its main objectives, requirements and design. It will give a general view of the past and present development, assembly and testing activities for the EarthCARE space and ground segments, validation and science preparations and will address the main challenges encountered and associated lessons learned. The current status and most importantly, the plans for the remaining activities towards launch, commissioning and exploitation will be described in detail.
EarthCARE CPR has been developed by Japan Aerospace Exploration Agency (JAXA) and National Institute of Information and Communications Technology (NICT) for the Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) mission. This is the world’s first cloud radar that measures vertical profiles of the cloud and its vertical motion.
The CPR is a 94GHz pulse radar and measures altitude and Doppler velocity from received echo. Its minimum sensitivity is greater than -35dBZ and the Doppler velocity measurement accuracy is less than 1.3m/s. To achieve those performances, the CPR equips a big reflector with diameter of 2.5m. The observation altitude can be changed with Low (16 km), Middle（18 km), High (20 km).
CPR was transported to Europe in March 2021 and was handed over to ESA/Airbus in April 2022. Then CPR integration to EarthCARE satellite and test was completed by ESA/Airbus in June 2021.
This presentation introduces CPR overview and the latest status of preparation towards launch.
The EarthCARE payload consists of two active and two passive instruments that will provide collocated images, enabling synergistic use of the data that will be used to derive information about atmospheric processes. ESA has developed three of the instruments, an ATmospheric LIDar (ATLID), a Multi-Spectral Imager (MSI) and a Broad-Band Radiometer (BBR). JAXA has developed a Cloud Profiling Radar (CPR).
The objective of the BBR is to derive instantaneous, broadband, top of atmosphere fluxes, with an accuracy better than 10 Wm-2. The instrument development was led by TAS-UK, with an Optics Unit from RAL (UK). 10 x 10 km scenes fore, nadir and aft on the satellite ground track are obtained, with measurements made in shortwave and longwave channels, using three telescopes, each with a linear, microbolometer array, operating with push-broom motion. Thereby, matched short and long wave scenes are provided from the three telescope views, that are spatially coincident, from different observation angles, and with small separations in observation time. Whilst a 10 km scene size defines the performance requirements, BBR field of view is configurable and can therefore also be processed, for instance, in a 21 km long and 5 km wide configuration (21 km due to CPR cycles of 7 km length). On-board calibration is performed using views to blackbodies and a solar illuminated diffuser.
The objective of MSI is to provide contextual information on the horizontal structures of clouds, more specifically cloud type and cloud optical and microphysical properties over sea and land surfaces. Further, it has a goal to provide information concerning aerosol over sea surfaces, to supplement the ATLID aerosol measurements in an across-track dimension. The instrument development was led by SSTL (UK), which also built the three channel Thermal Infrared (TIR) camera, whilst a four channel Visible, Near infrared, Short-wave infrared (VNS) camera has been built by TNO (NL). The instrument collects data over a 150 km swath that is pointed slightly across track in order to reduce sun glint. The VNS camera operates in pushbroom, to collect data over four focal planes employing linear photodiode arrays. Calibration is via closed shutter dark images and a view to a solar illuminated diffuser. The TIR camera is equipped with a 2-D microbolometer array and uses Time Delay Integration in order to increase the signal to noise ratio. Calibration is via a blackbody and a view to cold space.
ATLID objective is the provision of vertical profiles of optically thin cloud and aerosol layers, characterising aerosol optical properties and measuring the altitude of cloud boundaries while detecting small ice particles and water droplets. It will complement cloud observations from the CPR. Airbus Toulouse (F) has led the development of ATLID, with the laser transmitter assembly integrated by Leonardo (I). The instrument is a bistatic, high spectral resolution lidar that emits short laser pulses in the UV, at a repetition rate of 51 Hz. The 620 mm aperture receiving telescope filters the return signal through the optics of the instrument focal plane assembly, separating the signals backscattered by the atmosphere to provide measurements of the aerosol (Mie) and molecular (Rayleigh) components. The Mie co and cross-polarised components are also distinguished. After initial calibration on orbit ensures best alignment between the transmit and receive channels and best receiver focus, a coarse spectral calibration is performed. A fine spectral calibration is then regularly undertaken, as well as calibrations to monitor the detectors, spectral and polarisation cross talk and lidar constants.
This paper will provide an overview of the design and function of the instruments with results from their on-ground calibration and their performance predictions.
The interactions between clouds, aerosols and solar and terrestrial radiation play key roles in the Earth’s Climate. It has been recognized that, despite a long history of satellite observations, further high-quality novel observations are needed for atmospheric model evaluation and process studies. In particular, the importance of true height-resolved global observations of cloud and aerosol properties has been recognized as being essential to making progress. EarthCARE is an upcoming ESA/JAXA mission to fly in 2023 which will focus on making these observation.
The four EarthCARE instruments provide synergistic observations of cloud and aerosol profiles, precipitation and broad-band solar and thermal fluxes are:
• A 94 GHz, Doppler Cloud Radar (CPR) supplied by JAXA which will be the first 94 GHz radar in space with Doppler capability, to measure (thick) cloud profiles, vertical ice particle velocities and precipitation.
• An advanced 355 nm High-Spectral Resolution Lidar (ATLID) including a total depolarization channel
• A Multispectral imager for narrow-band TOA radiances (MSI) to provide across-track scene context information and additional cloud and aerosol information.
• A 3-view Broad-Band Long- and Short-Wave Radiometer for TOA radiance (BBR) to measure the outgoing emitted, respectively, reflected, broad-band solar and thermal radiation at the top of the atmosphere.
The ESA scientific retrieval processors are fully exploiting the synergy of these observations. EarthCARE will provide twenty-five science (Level 2) products generated by seventeen separate processors. These products include nadir profiles of cloud, aerosol and precipitation properties along with constructed three-dimensional cloud-aerosol-precipitation domains and associated with calculated radiative properties, such as heating rates The final L2 processor compares the forward modelled top-of-atmosphere broad-band radiances and fluxes based on the constructed 3D atmospheric scenes with those measured by the BBR in order to assess and improve the quantitative understanding of the role of clouds and aerosols on radiation. In the autumn of 2021 the seventeen individual processors were chained together for the first time to simulate the full processing chain from input L1 signals to the final L2 retrievals.
The presentation will provide an overview of the scientific data products, processors and preparations for in-orbit validation.
Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) mission is designed to produce the maximum synergetic collaboration of European and Japanese science teams. The EarthCARE products will be developed and distributed from both JAXA and ESA. Continuous exchanges of information have been conducted between Japan and Europe through the Joint Algorithm Development Endeavor (JADE). CPR, ATLID and MSI Level-2 provide cloud mask, cloud phase and cloud microphysics (such as cloud effective radius, liquid water content, optical depth, etc) for the respective sensor products, together with the synergy products by using the combination of the sensors. Further, the CPR provides the Doppler velocity measurement (which gives the vertical information of the in-cloud velocity), and precipitation products. ATLID Level-2 includes aerosol flagging, aerosol component type (such as dust, black carbon, sea salt and water soluble), as well as the aerosol optical properties including aerosol extinction. The cloud and aerosol products will be used to derive the radiative flux at shortwave and longwave, whose consistency with the BBR will be checked to produce the final radiation product by 4-sensors.
Validation activities are necessary to distribute the scientific products whose quality and reliability are assured. The JAXA is planning the validation activities by utilization of the existing observation network, campaign observation, and cross comparison with other satellite data.
Furthermore, a wide range of application research activities will be planned to achieve the mission objectives. EarthCARE observation data will contribute to understanding cloud, aerosol, and radiation processes, evaluations and improvements of climate models and numerical weather prediction (NWP) models, and atmospheric quality monitoring. The Intergovernmental Panel on Climate Change (IPCC) report published in August 2021, “Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the IPCC”, summarizes that the cloud feedback remains the largest contribution to overall uncertainty, and contributions to mitigate the uncertainty can be expected by new insights by the EarthCARE observations.
This presentation will introduce JAXA Level 2, Validation and Applications Preparation.
The EarthCARE mission, implemented in cooperation with JAXA, will be the largest and most complex ESA Earth Explorer mission built to date, and its products will contribute fundamentally to the understanding of the climate system. The combination of two active (lidar and radar) and two passive instruments (imager and radiometer) instruments will provide synergistic observations of cloud and aerosol profiles, precipitation and broad-band solar and thermal fluxes.
ESA and JAXA defined and are coordinating a joint EarthCARE Scientific Validation Implementation Plan. This presentation will then focus on the ESA-coordinated Validation activities, in particular on validation of the Level 1 products of the ESA instruments (the atmospheric lidar instrument (i.e. ATLID), the broad band radiometer (i.e. BBR), and the multi-spectral imager (i.e. MSI)) and on the ESA-developed Level 2 products. These ESA Validation activities have been the outcome of an ESA announcement of opportunity that was issued in 2017 and for which more than 30 proposals had been received. A broad peer review of this program took place in 2018 during the 1st ESA Validation Workshop in Bonn (held in concomitance with the 7th EarthCARE Science Workshop), to assess the scope of the proposed activities. A second workshop was held online in March May 2021 to review the validation approaches and methods. Here, also the broader context was addressed, with EarthCARE products contributing to space-borne Earth observation data record together with those with from earlier and later missions /instruments such as Aeolus, Calipso, Cloudsat, CERES, GPM, Aeolus Follow-On, and ACCP/AOS. Many of the workshop recommendations concerned common practice consolidation for aerosol and cloud profile validation, which will be addressed in a dedicated poster.
The EarthCARE product validation will begin during the 6-month commissioning phase and will continue during the entire exploitation phase of at least 2.5 years
In preparation of this exploitation phase, ESA intends to foster EarthCARE application development via its Research Opportunity announcements under its broader Atmospheric Science Cluster scheme. The presentation will give very brief guidance on this mechanism, in particular the schedule of open and upcoming calls.
A further preparation activity for exploitation of EarthCARE data that is already well underway is aimed at achieving readiness for EarthCARE data assimilation.: The high-resolution, profiling observations of clouds from EarthCARE will contain a wealth of information on the current atmospheric state and therefore have the potential to improve the initialisation of weather forecasts. To fully exploit this, ESA and the European Centre for Medium-Range Forecasts (ECMWF) have been working closely to ensure that EarthCARE’s observations can be assimilated at a global numerical weather prediction centre as soon as possible after launch. Observing system experiments where CloudSat radar reflectivity and CALIPSO lidar backscatter are assimilated in the ECMWF integrated forecast system (IFS) have revealed the power of EarthCARE’s novel observations to have a direct benefit on forecasts of temperature, humidity and winds. Including EarthCARE data within the IFS will also allow the data to be monitored against model forecasts and thus provides an invaluable validation tool for the rapid detection and diagnosis of observation issues.