Search

ESA’s Aeolus satellite observations are expected to have the biggest impact for the improvement of numerical weather prediction in the Tropics. An important case relating to the predictability of tropical weather systems is the outflow of Saharan dust, its interaction with cloud microphysics and impact on the development of tropical storms over the Atlantic Ocean.The Joint Aeolus Tropical Atlantic Campaign (JATAC) deployed on Cabo Verde (2021/2022) and the US Virgin Islands (2021) supported the validation and preparation of the ESA missions Aeolus, EarthCARE and WIVERN, and addressed science objectives regarding the Saharan Aerosol layer, African Easterly Waves and Jet, Tropical Easterly Jet, and the Intertropical Convergence Zone, as well as their relation to the formation of convective systems, and the long-range transport of dust and its impact on air quality.JATAC started in July 2021 with the deployment of ground-based instruments in the frame of the ASKOS project at the Ocean Science Center Mindelo, including the eVe and PollyXT lidars, and a W-band Doppler cloud radar. By mid-August, the CPEX-AW campaign started operations from the US Virgin Islands with NASA’s DC-8 flying laboratory in the Western Tropical Atlantic and Caribbean carrying the Doppler Aerosol Wind Lidar (DAWN), Airborne Precipitation and Cloud Radar (APR-3), Water Vapor DIAL and HSRL (HALO), microwave sounder (HAMSR) and dropsondes. In September the DLR Falcon-20 aircraft, carrying the ALADIN Airborne Demonstrator (A2D) and the 2-µm Doppler wind lidar, and the Safire Falcon-20, carrying the high-spectral-resolution Doppler lidar (LNG), the RASTA Doppler cloud radar, in-situ cloud and aerosol instruments, and dropsondes, were deployed to Sal in the frame of the AVATAR-T and CADDIWA projects. The Aerovizija Advantic WT-10 light aircraft with optical particle spectrometers, filter-photometers and nephelometers for in-situ aerosol characterisation was operating in close coordination with the ground-based observations in the CAVA-AW project.The activities continued in June 2022 when the ASKOS ground based observations were enhanced with UAV airborne in-situ aerosol measurements deployed by the Cyprus Institute, solar radiation measurements supported by PMOD/WRC, dust particle orientation measurements (WALL-E lidar), and radiosonde releases equipped with electric field-mills. NASA deployed the DC-8 aircraft all September to Sal with the 2021 payload in the framework of the CPEX-CV activity, including regular radiosonde launches. As in 2021, the Aerovizija aircraft took part with in-situ aerosol measurements during two weeks in September. JATAC was supported by dedicated numerical weather and dust simulations supporting forecasting efforts and addressing open science questions.Around 60 scientific flights of four aircraft, with an additional 25 UAV flights, were performed during JATAC. 23 Aeolus orbits were underflown, many of them with simultaneous observations of multiple aircraft collocated with ground-based observations. In addition, the science objectives were fully covered through the large number of flights, ground based cloud and aerosol observations, regular radiosondes and dropsondes.Overall, JATAC activities have resulted in a high-quality and comprehensive dataset supporting a wide range of tropical atmospheric research, the validation of Aeolus and other satellites, and have provided key reference data for the development future Earth Observation missions.

Forecasting volcanic ash atmospheric pathways is of utmost importance for aviation. Volcanic ash can interfere with aircraft navigational instruments and can damage engine parts. Early warning systems, activated after volcanic eruptions can alleviate the impacts on aviation by providing forecasts of the volcanic ash plume dispersion. The quality of these short-term forecasts is subject to the accuracy of the meteorological wind fields used for the initialization of regional models. Here, we use wind profiling data from the first High Spectral Resolution Lidar in Space, Aeolus, to examine the impact of measured wind fields on regional NWP and subsequent volcanic ash dispersion forecasts, focusing on the case of Etna’s eruption on March 2021. The results from this case study demonstrate a significant improvement of the volcanic ash simulation when using Aeolus-assimilated meteorological fields, with differences in wind speed reaching up to 8 m/s when compared to the control run. When comparing the volcanic ash forecast profiles with downwind surface-based aerosol lidar observations, the modeled field is consistent with the measurements only when Aeolus winds are assimilated. This result clearly illustrates the potential and importance of wind profiling from space for volcanic ash forecasting and hence aviation safety.

The ESA Earth Explorer CryoSat-2 was launched on 8 April 2010 to monitor the precise changes in the thickness of terrestrial ice sheets and marine floating ice. To do that, CryoSat orbits the planet at an altitude of around 720 km with a retrograde orbit inclination of 92∘ and a quasi repeat cycle of 369 d (30 d subcycle). To reach the mission goals, the CryoSat products have to meet the highest quality standards to date, achieved through continual improvements of the operational processing chains. The new CryoSat Ice Baseline-D, in operation since 27 May 2019, represents a major processor upgrade with respect to the previous Ice Baseline-C. Over land ice the new Baseline-D provides better results with respect to the previous baseline when comparing the data to a reference elevation model over the Austfonna ice cap region, improving the ascending and descending crossover statistics from 1.9 to 0.1 m. The improved processing of the star tracker measurements implemented in Baseline-D has led to a reduction in the standard deviation of the point-to-point comparison with the previous star tracker processing method implemented in Baseline-C from 3.8 to 3.7 m. Over sea ice, Baseline-D improves the quality of the retrieved heights inside and at the boundaries of the synthetic aperture radar interferometric (SARIn or SIN) acquisition mask, removing the negative freeboard pattern which is beneficial not only for freeboard retrieval but also for any application that exploits the phase information from SARIn Level 1B (L1B) products. In addition, scatter comparisons with the Beaufort Gyre Exploration Project (BGEP; https://www.whoi.edu/beaufortgyre, last access: October 2019) and Operation IceBridge (OIB; Kurtz et al., 2013) in situ measurements confirm the improvements in the Baseline-D freeboard product quality. Relative to OIB, the Baseline-D freeboard mean bias is reduced by about 8 cm, which roughly corresponds to a 60 % decrease with respect to Baseline-C. The BGEP data indicate a similar tendency with a mean draft bias lowered from 0.85 to −0.14 m. For the two in situ datasets, the root mean square deviation (RMSD) is also well reduced from 14 to 11 cm for OIB and by a factor of 2 for the BGEP. Observations over inland waters show a slight increase in the percentage of good observations in Baseline-D, generally around 5 %–10 % for most lakes. This paper provides an overview of the new Level 1 and Level 2 (L2) CryoSat Ice Baseline-D evolutions and related data quality assessment, based on results obtained from analyzing the 6-month Baseline-D test dataset released to CryoSat expert users prior to the final transfer to operations.

We describe and discuss the preprocessing and calibration steps applied to the magnetic data measured by the three “platform magnetometers” on-board the CryoSat-2 satellite. The calibration is performed by comparing the magnetometer sensor readings with magnetic field values for the time and position of the satellite as given by the CHAOS-6 geomagnetic field model. We allow for slow temporal variations of the calibration parameters by solving for scale values, offsets, and non-orthogonalities in monthly bins, and account for non-linearities as well as the magnetic disturbances caused by battery, solar panel and magnetorquer currents. Fully calibrated magnetic vector data, together with time and position, are provided as daily files in CDF data format at swarm-diss.eo.esa.int. The data show good agreement with Swarm satellite magnetic measurements during close encounters (rms difference between 1 and 5 nT for inter-satellite distances below 300 km).

The Data Innovation and Science Cluster (DISC) is a core element of ESA's data quality strategy for the Aeolus mission, which was launched in August 2018. Aeolus provides for the first-time global observations of vertical profiles of horizontal wind information by using the first Doppler wind lidar in space. The Aeolus DISC is responsible for monitoring and improving the quality of the Aeolus aerosol and wind products, for the upgrade of the operational processors as well as for impact studies and support of data usage. It has been responsible for multiple significant processor upgrades which reduced the systematic error of the Aeolus observations drastically. Only due to the efforts of the Aeolus DISC team members prior to and after launch, the systematic error of the Aeolus wind products could be reduced to a global average below 1 m/s which was an important pre-requisite for making the data available to the public in May 2020 and for its use in operational weather prediction. In 2020, the reprocessing of earlier acquired Aeolus data, another important task of the Aeolus DISC, also started. In this way, also observations from June to December 2019 with significantly better quality could be made available to the public, and more data will follow this and next year. Without the thorough preparations and close collaboration between ESA and the Aeolus DISC over the past decade, many of these achievements would not have been possible.

International audience; We highlight some of the scientific benefits of the Aeolus Doppler Wind Lidar mission since its launch in August 2018. Its scientific objectives are to improve weather forecasts and to advance the understanding of atmospheric dynamics and its interaction with the atmospheric energy and water cycle. A number of meteorological and science institutes across the world are starting to demonstrate that the Aeolus mission objectives are being met. Its wind product is being operationally assimilated by four Numerical Weather Prediction (NWP) centres, thanks to demonstrated useful positive impact on NWP analyses and forecasts. Applications of its atmospheric optical properties product have been found, e.g., in the detection and tracking of smoke from the extreme Australian wildfires of 2020 and in atmospheric composition data assimilation. The winds are finding novel applications in atmospheric dynamics research, such as tropical phenomena (Quasi-Biennial Oscillation disruption events), detection of atmospheric gravity waves, and in the smoke generated vortex associated with the Australian wildfires. It has been applied in the assessment of other types of satellite derived wind information such as atmospheric motions vectors. Aeolus is already successful with hopefully more to come.

The acquisition of atmospheric wind profiles on a global scale was realized by the launch of the Aeolus satellite, carrying the unique Atmospheric LAser Doppler INstrument (ALADIN), the first Doppler wind lidar in space. One major component of ALADIN is its high-power, ultraviolet (UV) laser transmitter, which is based on an injection-seeded, frequency-tripled Nd:YAG laser and fulfills a set of demanding requirements in terms of pulse energy, pulse length, repetition rate, and spatial and spectral beam properties. In particular, the frequency stability of the laser emission is an essential parameter which determines the performance of the lidar instrument as the Doppler frequency shifts to be detected are on the order of 108 smaller than the frequency of the emitted UV light. This article reports the assessment of the ALADIN laser frequency stability and its influence on the quality of the Aeolus wind data. Excellent frequency stability with pulse-to-pulse variations of about 10 MHz (root mean square) is evident for over more than 2 years of operations in space despite the permanent occurrence of short periods with significantly enhanced frequency noise (> 30 MHz). The latter were found to coincide with specific rotation speeds of the satellite's reaction wheels, suggesting that the root cause are micro-vibrations that deteriorate the laser stability on timescales of a few tens of seconds. Analysis of the Aeolus wind error with respect to European Centre for Medium-Range Weather Forecasts (ECMWF) model winds shows that the temporally degraded frequency stability of the ALADIN laser transmitter has only a minor influence on the wind data quality on a global scale, which is primarily due to the small percentage of wind measurements for which the frequency fluctuations are considerably enhanced. Hence, although the Mie wind bias is increased by 0.3 m s−1 at times when the frequency stability is worse than 20 MHz, the small contribution of 4 % from all Mie wind results renders this effect insignificant (< 0.1 m s−1) when all winds are considered. The impact on the Rayleigh wind bias is negligible even at high frequency noise. Similar results are demonstrated for the apparent speed of the ground returns that are measured with the Mie and Rayleigh channel of the ALADIN receiver. Here, the application of a frequency stability threshold that filters out wind observations with variations larger than 20 or 10 MHz improves the accuracy of the Mie and Rayleigh ground velocities by only 0.05 and 0.10 m s−1, respectively, however at the expense of useful ground data.

Already shortly after the successful launch of the European Space Agency satellite Aeolus in August 2018, it turned out that dark current signal anomalies of single pixels (so-called hot pixels) on the Accumulation-Charge-Coupled Devices (ACCDs) of the Aeolus detectors detrimentally impact the quality of the aerosol and wind products potentially leading to wind errors of up to 4 m/s. This paper provides a detailed characterization of the hot pixels which occurred during the first one and a half years in orbit. The hot pixels are classified according to their characteristics to discuss their impact on wind measurements. Furthermore, mitigation approaches for the wind retrieval are presented and potential root causes for the hot pixel occurrence are discussed. The analysis of the dark current signal anomalies reveals a large variety of anomalies ranging from pixels with Random Telegraph Signal (RTS)-like characteristics to pixels with sporadic shifts in the median dark current signal. Moreover, the results indicate that the number of hot pixels has almost linearly increased during the observing period between 2018-09-02 until 2020-05-20 with 6 % of the ACCD pixels affected in total at the end of the period leading to 9.5 % at the end of mission lifetime. This work introduces dedicated instrument calibration modes and ground processors which allowed for a correction shortly after a hot pixel occurrence. The achieved performance with this approach avoids risky adjustments to the inflight hardware operation. It is demonstrated that the success of the correction scheme varies depending on the characteristics of each hot pixel itself. With the herein presented categorization, it is shown that multi-level RTS pixels with high fluctuation are the biggest challenge for the hot pixel correction scheme. Despite a detailed analysis in this framework, no conclusion could be drawn about the root cause of the hot pixel issue.

The European Space Agency's (ESA) wind mission, Aeolus, hosts the first space-based Doppler Wind Lidar (DWL) world-wide. Its scientific objectives are to improve weather forecasts and to advance the understanding of atmospheric dynamics and its interaction with the atmospheric energy and water cycle. The primary data product is profiles of horizontally projected line-of-sight winds from the surface up to about 30 km, and spin-off products are profiles of cloud and aerosol optical properties. Aeolus was launched on 22 August 2018, and the Atmospheric LAser Doppler INstrument (ALADIN) switch-on was completed with first high energy output in wind mode on 4 September 2018. The on-ground data processing facility worked excellent, allowing L2 product output in near-real-time (within 3 hours of sensing) from the start of the mission. During the first 20 months in orbit, ESA, the Aeolus Data Innovation and Science Cluster (DISC), Aeolus calibration and validation (CAL/VAL) teams and industry worked on the instrument commissioning, calibration, validation and product improvements, leading to the public release of the Level 2B (L2B) wind product in May 2020. The Aeolus L2B wind data were then of such good quality that four weather centers started to use the product in their daily forecasts during 2020, and more have plans to follow in 2021. As of May 2020, the biases of the near-real-time data were on average close to the mission requirements, although the random errors were higher than expected due to lower than expected atmospheric return signal on orbit. Other issues encountered in-flight were for example drifts in the instrument alignment and nonoptimal telescope focus and temperature control, leading to drifts in the laser emitted output energy and/or internal and atmospheric path signal strength and long term evolutions on the wind product bias. A further issue encountered was a gradually increasing number of “hot pixels”, i.e. pixels with elevated background signals, appearing on the ALADIN ACCDs over time. Mitigation strategies for these issues arebeing implemented, or are considered for a potential follow-on mission. The Aeolus optical properties spin-off product (L2A) has been further improved after launch, including methods for improved aerosol and cloud backscatter discrimination. The product has been used to study smoke emissions, e.g. from the early 2020 Australian fires, and has been successfully experimentally assimilated in Copernicus Atmosphere Monitoring Service (CAMS) model C-IFS. After two and a half years in orbit, and despite of some performance issues related to the ALADIN instrument, Aeolus has already achieved most of its scientific objectives. Finally, the mission was recently extended until end 2022.

ESA supported airborne and ground-based campaigns constitute an essential element in the development and operation of satellite missions, providing the opportunity to test novel observation technologies, acquire representative data for the development of the mission concepts, processors and use cases, as well as in their calibration and validation phases once in orbit.For the Aeolus Doppler Wind Lidar satellite mission, ESA has implemented a campaign programme that started in 2007 and has continued beyond the launch of the mission on 22. August 2018. Building on the successful WindVal-I and –II campaigns with DLR’s A2D and 2µm Doppler Wind Lidar systems on-board the DLR Falcon aircraft, a number of validation campaigns have been successfully implemented: WindVal-III in November 2018, AVATAR-E in May 2019, and AVATAR-I in September 2019. In addition, ESA supported the CNES pre-Stratéole-2/TAPAPA campaign with eight stratospheric balloons having been launched from the Seychelles in November/December 2019 providing unique upper level wind data in the Tropics. The validation by stratospheric balloons has been extended in the frame of a collaboration with Loon LLC for a test case covering the months August and September 2019.As the largest impact of the Aeolus observations is expected in the Tropics, and in particular over the Tropical oceans, ESA, in close collaboration with NASA and European partners, is currently implementing a Tropical campaign in July 2021. With its base in Cape Verde the activity comprises both airborne and ground-based activities addressing the tropical winds and aerosol validation, as well as a wide range of science objectives. The location is unique as it allows the study of the Saharan Aerosol layer, African Easterly Waves and Jets, the Tropical Easterly Jet, as well as deep convection in ITCZ and tropical cyclogenesis, with a focus on the impact of Saharan dust on micro-physics in tropical cloud systems. The campaign builds on remote and in-situ observations from aircraft (DLR Falcon-20, the Safire Falcon-20, the NASA DC-8 and an Aerovizija/UNG light aircraft) and drone systems, as well as an extensive aerosol and cloud measurement programme with a range of lidar, radar and radiometer systems coordinated by NOA.This paper will provide a summary of the Aeolus campaign activities, focussing on the completed and planned post launch campaigns.

The Tropics are covering around 40% of the globe and are home to approximately 40% of the world population. However, numerical weather prediction (NWP) for this region still remains challenging due to the lack of basic observations and incomplete understanding of atmospheric processes, also affecting extratropical storm developments. As a result, the largest impact of the ESA’s Aeolus satellite observations on NWP is expected in the Tropics where only a very limited number of wind profile observations from the ground can be performed.An especially important case relating to the predictability of tropical weather system is the outflow of Saharan dust, its interaction with cloud micro-physics and the overall impact on the development of tropical storms over the Atlantic Ocean. The region of the coast of West Africa uniquely allows the study of the Saharan Aerosol layer, African Easterly Waves and Jets, Tropical Easterly Jet, as well as the deep convection in ITCZ and their relation to the formation of convective systems and the transport of dust.Together with international partners, ESA and NASA are currently implementing a joint Tropical campaign from July to August 2021 with its base in Cape Verde. The campaign objective is to provide information on the validation and preparation of the ESA missions Aeolus and EarthCARE, respectively, as well as supporting a range of related science objectives for the investigation in the interactions between African Easterly and other tropical waves with the mean flow, dust and their impact on the development of convective systems; the structure and variability of the marine boundary layer in relation to initiation and lifecycle of the convective cloud systems within and across the ITCZ; and impact of wind, aerosol, clouds, and precipitation effects on long range dust transport and air quality over the western Atlantic.The campaign comprises a unique combination of both strong airborne and ground-based elements collocated on Cape Verde. The airborne component with wind and aerosol lidars, cloud radars, in-situ instrumentation and additional observations includes the NASA DC-8 with science activities coordinated by the U. of Washington, the German DLR Falcon-20, the French Safire Falcon-20 with activities led by LATMOS, and the Slovenian Aerovizija Advantic WT-10 light aircraft in cooperation with the U. Novo Gorica. The ground-based component led by the National Observatory of Athens is a collaboration of more than 25 European teams providing in-situ and remote sensing aerosol and cloud measurements with a wide range of lidar, radar and radiometer systems, as well as drone observatins by the Cyprus Institute.In preparation for the field campaign, the NASA and ESA management and science teams are closely collaborating with regular coordination meetings, in particular in coordinating the shift of the activity by one year due to the COVID-19 pandemic. The time gained has been used to further consolidate the planning, and in particular with a dry-run campaign organized by NASA with European participation where six virtual flights were conducted in July 2020. This paper will present a summary of the campaign preparation activities and the consolidated plan for the 2021 Tropical campaign.

The European Space Agency (ESA)’s wind mission, Aeolus, was launched on 22 August 2018. It is a member of the ESA Earth Explorer family and its main objective is to demonstrate the potential of Doppler wind Lidars in space for improving weather forecast and to understand the role of atmospheric dynamics in climate variability. Aeolus carries a single instrument called ALADIN: a high sophisticated spectral resolution Doppler wind Lidar which operates at 355 which is the first of its kind to be flown in space.Aeolus provides profiles of single horizontal line-of-sight winds (primary product) in near-real-time (NRT), and profiles of atmospheric backscatter and extinction. The instrument samples the atmosphere from about 30 km down to the Earth’s surface, or down to optically thick clouds. The required precision of the wind observations is 1-2.5 m/s in the troposphere and 3-5 m/s in the stratosphere while the systematic error requirement be less than 0.7 m/s. The mission spin-off product includes information about aerosol and cloud layers. The satellite flies in a polar dusk/dawn orbit (6 am/pm local time), providing ~16 orbits per 24 hours with an orbit repeat cycle of 7 days. Global scientific payload data acquisition is guaranteed with the combined usage of Svalbard and Troll X-band receiving stations.After almost three years in orbit and despite performance issues related to its instrument ALADIN, Aeolus has achieved most of its objectives. Positive impact on the weather forecast has been demonstrated by multiple NWP centres world-wide with four European meteorological centres now are assimilating Aeolus winds operationally. Other world-wide meteo centers wull start to assimilate data in 2021. The status of the Aeolus mission will be presented, including overall performance, planned operations and exploitation. Scope of the paper is also to inform about the programmatic highlights and future challenges.

Launched in 2010, the European Space Agency’s (ESA) polar-orbiting CryoSat satellite was specifically designed to measure changes in the thickness of polar sea ice and the elevation of the ice sheets and mountain glaciers. Beyond the primary mission objectives, CryoSat is also valuable source of data for the oceanographic community and CryoSat’s sophisticated SAR Interferometric Radar Altimeter (SIRAL) can measure high-resolution geophysical parameters from the open ocean to the coast.CryoSat data is processed operationally using two independent processing chains: Ice and Ocean. To ensure that the CryoSat products meet the highest data quality and performance standards, the CryoSat Instrument Processing Facilities (IPFs) are periodically updated. Processing algorithms are improved based on feedback and recommendations from Quality Control (QC) activities, Calibration and Validation campaigns, the CryoSat Expert Support Laboratory (ESL), and the Scientific Community.Since May 2019, the CryoSat ice products have been generated with Baseline-D, which represented a major processor upgrade and implemented several improvements, including the optimisation of freeboard computation in SARIn mode, improvements to sea ice and land ice retracking and the migration from Earth Explorer Format (EEF) to Network Common Data Form (NetCDF). The Baseline-D reprocessing campaign completed in May 2020, and the full mission Baseline-D dataset is now available to users (July 2010 – present). The next major processor upgrade, Baseline-E, is already under development and following testing and refinement is anticipated to be operational in Q3 2021.The CryoSat ocean products are also generated in NetCDF, following a processor upgrade in November 2017 (Baseline-C). Improvements implemented in this baseline include the generation of ocean products for all data acquisition modes, therefore providing complete data coverage for ocean users. This upgrade also implemented innovative algorithms, refined existing ones and added new parameters and corrections to the products. Following the completion of a successful reprocessing campaign, Baseline-C ocean products are now available for the full mission dataset (July 2010 – present). Preparations are underway for the next major processor upgrade, Baseline-D.Since launch, the CryoSat ice and ocean products have been routinely monitored as part of QC activities by the ESA/ESRIN Sensor Performance, Products and Algorithms (SPPA) office with the support of the Quality Assurance for Earth Observation (QA4EO) service (formerly IDEAS+) led by Telespazio UK. The latest processor updates have brought significant improvements to the quality of CryoSat ice and ocean products, which in turn are expected to have a positive impact on the scientific exploitation of CryoSat measurements over all surface types.This poster provides an overview of the CryoSat data quality status and the QC activities performed by the IDEAS-QA4EO consortium, including both operational and reprocessing QC. Also presented are the main evolutions and improvements that have implemented to the processors, and anticipated evolutions for the future.

ESA deployed the first Doppler wind lidar in space within its Earth Explorer Mission Aeolus in August 2018. Since then global wind profiles have been acquired for the improvement of weather forecasts on short and medium term. Current calibration and validation activities indicate the demanded positive impact from different forecast centers. In addition, Aeolus provides profiles of atmospheric backscatter and extinction coefficients that are supposed to become input for air quality models. The talk will provide an overview of the encountered technical challenges in flight and some preliminary results from impact studies.

Launched in 2010, the European Space Agency’s (ESA) polar-orbiting CryoSat satellite was specifically designed to measure changes in the thickness of polar sea ice and the elevation of the ice sheets and mountain glaciers. Beyond the primary mission objectives, CryoSat is also valuable source of data for the oceanographic community and CryoSat’s sophisticated SAR Interferometric Radar Altimeter (SIRAL) can measure high-resolution geophysical parameters from the open ocean to the coast.CryoSat data is processed operationally using two independent processing chains: Ice and Ocean. To ensure that the CryoSat products meet the highest data quality and performance standards, the CryoSat Instrument Processing Facilities (IPFs) are periodically updated. Processing algorithms are improved based on feedback and recommendations from Quality Control (QC) activities, Calibration and Validation campaigns, the CryoSat Expert Support Laboratory (ESL), and the Scientific Community. Since May 2019, the CryoSat ice products are generated with Baseline-D, which represented a major processor upgrade and implemented several improvements, including the optimisation of freeboard computation in SARIn mode, improvements to sea ice and land ice retracking and the migration from Earth Explorer Format (EEF) to Network Common Data Form (NetCDF). A reprocessing campaign is currently underway to reprocess the full mission dataset (July 2010 – May 2019) to Baseline-D.The CryoSat ocean products are also generated in NetCDF, following a processor upgrade in November 2017 (Baseline-C). Improvements implemented in this new Baseline include the generation of ocean products for all data acquisition modes, therefore providing complete data coverage for ocean users. This upgrade also implemented innovative algorithms, refined existing ones and added new parameters and corrections to the products. Following the completion of a successful reprocessing campaign, Baseline-C ocean products are now available for the full mission dataset (July 2010 – present).Since launch, the CryoSat ice and ocean products have been routinely monitored as part of QC activities by the ESA/ESRIN Sensor Performance, Products and Algorithms (SPPA) office with the support of the Quality Assurance for Earth Observation (QA4EO) service (formerly IDEAS+) led by Telespazio VEGA UK. The latest processor updates have brought significant improvements to the quality of CryoSat ice and ocean products, which in turn are expected to have a positive impact on the scientific exploitation of CryoSat measurements over all surface types.This poster provides an overview of the CryoSat data quality status and the QC activities performed by the QA4EO consortium, including both operational and reprocessing QC. Also presented are the main evolutions and improvements that have implemented to the processors, and anticipated evolutions for the future.

The main payload of CryoSat is a Ku-band pulsewidth limited radar altimeter, called SIRAL (Synthetic interferometric radar altimeter), that is equipped with two antennas for single-pass interferometric capability.Due to the unique characteristics of SIRAL, a proper calibration approach was developed. In fact, not only corrections for transfer function, gain and instrument path delay have to be computed (as in previous altimeters), but also corrections for phase (SAR/SARIn) and phase difference between the two receiving chains (SARIN only). To summarize, SIRAL performs regularly four types of internal calibrations:- CAL1 in order to calibrate the internal path delay and long-term power drift.- CAL2 in order to compensate for the instrument IF transfer function.- CAL4 to calibrate the interferometer.- AutoCal, a specific sequence used to calibrate the gain and phase difference for each AGC setting.After about 10 years of operational activity of the CryoSat satellite, the performance of the SIRAL instrument are revealed to be in line or better than the expected one.In fact the calibration products, that have been designed to model a wide range of imperfections of the instrument, can be analyzed to highlight whether and how the instrument is changing over the time also as function of its thermal status. It is worth underlining here that each variation of the instrument measured by the calibration data is compensated in the Level1 processing. Inspecting the temporal evolution of the calibration data, SIRAL has been verified to be stable during its life. The performance of the SIRAL will be presented together with the outcomes of the stability analysis on the calibration data, in order to verify that the instrument has reached the requirements and that it is maintaining the performance over its life. In order to monitor the performance of the CryoSat interferometer along the mission, in orbit calibration campaigns have been periodically performed about once a year. The end-to-end calibration strategy for the CryoSat interferometer uses the ocean surface as the known external target. In fact, the interferometer can be used to determine the across-track slope of the overflown surface and the slope of the ocean surface can be considered as known starting from the geoid. Denoting by β the across-track slope of the ocean and assuming that the knowledge error of the geoid slope is negligibly small, β can be compared with the across-track slope derived from CryoSat SARin Level1b products which results in β'=η(θ-χ) where η is a geometric factor, θ is the angle of earliest arrival measured by the CryoSat interferometer and χ is the baseline roll angle. By comparison of the expected across-track slope β and the measured across-track slope β', the accuracy and the precision of the angle of arrival θ measured by the CryoSat interferometer can be assessed.In our analysis, the long-term accuracy (i.e. the closeness of the measurement to the true value) and the long-term precision (i.e. the closeness of agreement among a set of measurements) of the CryoSat interferometer have been assessed.

The European Space Agency, ESA deployed the first Doppler wind lidar in space within its Earth Explorer Mission Aeolus in August 2018. After the initial commissioning of the satellite and the single payload ALADIN, the mission has started to demonstrate the capability of Doppler lidar to measure wind from space. In order to provide the best Aeolus wind product possible, detailed monitoring of the instrument is crucial for analysis of system health, but also for the assessment of measurement performance and data product calibration. Within the last 1.2 years the different instrument modes to assess instrument and laser health, as well as the nominal wind processing indicated longterm instrument drifts. The laser beam profile has been monitored and showed an energy redistribution within the beam. The line of sight has slowly drifted, resulting in a change of incidence angle at spectrometer level. The impact of these observed drifts on the wind product are compensated on demand by updates of dedicated ground processing calibration files. This contribution will provide an overview about the Aeolus instrument modes and the observed stability that are needed to provide the Aeolus wind product. The current Aeolus performance has been assessed by various Numerical Weather Prediction centers. The positive outcome is represented by ECMWF’s decision to start using Aeolus data operationally on 9th January 2020.

The ESA Earth Explorer CryoSat-2 was launched on 8 April 2010 and from an altitude of just over 700 km and reaching latitudes of 88 degrees, monitors precise changes in the thickness of terrestrial ice sheets and marine ice. The aim of the CryoSat-2 mission is to determine variations in the thickness of the Earth's marine ice cover and understand the extent to which the Antarctic and Greenland ice sheets are contributing global sea level rise. In its 10 years of operations, CryoSat has achieved its mission objectives and has provided high-quality of data for a number of Earth science applications and opened up new research streams and triggered new scientific questions which have emerged from the previous phases. The purpose of this paper is to provide a general overview of the mission status and provide programmatic highlights in its new extended phase until 2021. It will also provide an overview of CryoSat data products covering both Ocean and Ice processing chains, presenting also the main evolutions and improvements that have implemented to the processors and anticipating evolutions for the future.

The European Space Agency (ESA)’s wind mission, Aeolus, was launched on 22 August 2018. Aeolus is a member of the ESA Earth Explorer family and its main objective is to demonstrate the potential of Doppler wind Lidars in space for improving weather forecast and to understand the role of atmospheric dynamics in climate variability. Aeolus carries a single instrument called ALADIN: a high sophisticated spectral resolution Doppler wind Lidar which operates at 355 which is the first of its kind to be flown in space. It provides profiles of single horizontal line-of-sight winds (primary product) in near-real-time (NRT), and profiles of atmospheric backscatter and extinction. The instrument samples the atmosphere from about 30 km down to the Earth’s surface, or down to optically thick clouds. The required precision of the wind observations is 1-2.5 m/s in the troposphere and 3-5 m/s in the stratosphere while the systematic error requirement be less than 0.7 m/s. The mission spin-off product includes information about aerosol and cloud layers. The satellite flies in a polar dusk/dawn orbit (6 am/pm local time), providing ~16 orbits per 24 hours with an orbit repeat cycle of 7 days. Global scientific payload data acquisition is guaranteed with the combined usage of Svalbard and Troll X-band receiving stations.The status of the Aeolus mission will be provided, including its performance assessment, planned operations and exploitation in the near future. This comprises the outcome of the instrument in its early operation phase, calibration and validation activities and a general review of the main scientific findings. Scope of the paper is also to inform about the programmatic highlights and future challenges.

Global acquisition of atmospheric wind profiles using a spaceborne direct-detection Doppler wind lidar is being accomplished following the launch of European Space Agency’s Aeolus mission. One key part of the instrument is a single-frequency, ultraviolet laser that emits nanosecond pulses into the atmosphere. High output energy and frequency stability ensure a sufficient signal-to-noise ratio of the backscatter return and an accurate determination of the Doppler frequency shift induced by the wind. This Letter discusses the design of the laser transmitter for the first Doppler wind lidar in space and its performance during the first year of the Aeolus mission, providing valuable insights for upcoming space lidar missions.

One of the candidate missions in the evolution of the Copernicus Space Component (CSC) is the Copernicus polaR Ice and Snow Topography ALtimeter (CRISTAL). The aim of this mission is to obtain high-resolution sea-ice thickness and land ice elevation measurements and includes the capability to determine the properties of snow cover on ice to serve Copernicus’ operational products and services of direct relevance to the Polar Regions. The evolution of the CSC is foreseen in the mid-2020s to meet priority user needs not addressed by the existing infrastructure, and to reinforce the Copernicus services by expanding the monitoring capability in the thematic domains of anthropogenic emissions (CO2), polar and agriculture/forestry/emergency. This evolution will be synergetic with the enhanced continuity of services foreseen with the next generation of the existing Copernicus Sentinels. New high-priority candidate satellite missions have been identified by the European Commission (EC) for implementation in the coming years to address gaps in current capability and emerging user needs. This paper describes the CRISTAL mission objectives, main mission requirements driving its design, the payload complement currently under development and its expected contributions to the monitoring of important components of Earth’s cryosphere.

CryoSat-2 is a satellite of the European Space Agency that was launched in April 2010. It is intended to monitor changes in the thickness of the marine ice, floating in the polar oceans, and to measure variations in the thickness of the vast ice sheets that overlie Greenland and Antarctica. The CryoSat-2 satellite has replaced the original CryoSat, which became lost due to a launch failure in October 2005. CryoSat-2 carries an innovative radar altimeter called SIRAL (Synthetic Aperture Interferometric Altimeter). It has two radar antennas, which met the measurement requirements for ice-sheet elevation and sea-ice freeboard with unprecedented accuracy. The satellite orbits the planet at an altitude of around 720 km with a retrograde drifting orbit inclination of 92° and a “quasi” repeat cycle of 369 days (30 days sub-cycle). CryoSat-2 is therefore able to reach latitudes up to 88° covering more than 4.6 million km2 of unexplored areas over the poles when compared with previous polar missions carrying an altimetry. The mission has achieved its prime objectives and is delivering high quality data, providing unique contributions to several Earth Science and applications domains, including ice, ocean, geodesy and hydrology, both at global and regional scales. The purpose of this paper is to provide a general overview of the mission and of its main scientific achievements after eight years in space.

Over the past 20 years, satellite radar altimetry has shown its ability to revolutionise our understanding of the ocean and climate. Previously, these advances were largely limited to ice-free regions, neglecting large portions of the Polar Regions. Launched in 2010, the European Space Agency’s (ESA) polar-orbiting CryoSat satellite was specifically designed to measure changes in the thickness of polar sea ice and the elevation of the ice sheets and mountain glaciers. To reach this goal, the CryoSat products have to meet the highest performance standards, achieved through continual improvements of the associated Instrument Processing Facilities. Since April 2015, the CryoSat ice products are generated with Baseline-C, which represented a major processor upgrade. Several improvements were implemented in this new Baseline, most notably the release of freeboard data within the Level 2 products. The Baseline-C upgrade has brought significant improvements to the quality of Level-1B and Level-2 products relative to the previous Baseline-B products, which in turn is expected to have a positive impact on the scientific exploitation of CryoSat measurements over land ice and sea ice. This paper provides an overview of the CryoSat ice data quality assessment and evolutions, covering all quality control and calibration activities performed by ESA and its partners. Also discussed are the forthcoming evolutions of the processing chains and improvements anticipated in the next processing Baseline.

Exploiting the interferometric capability of CryoSat, the interferometric phase related to the first arrival of the echo is used to retrieve the angle of arrival of the scattering in the across-track direction. This paper presents an assessment of the achievable end-to-end performance for the across-track angle that is retrieved by the CryoSat SARin acquisitions. In orbit calibration campaigns are periodically performed to monitor the performance and to calibrate the interferometer. We started from the analysis of the data acquired during the interferometer calibrations campaigns to verify if the current performance of CryoSat is in line with the system requirements. The analysis revealed that the interferometric measurements of CryoSat are exceeding the expected performance and that, by proper processing, it is possible to achieve further improvements for the accuracy on the retrieved across-track angle.

We present a new digital elevation model (DEM) of the Antarctic ice sheet and ice shelves based on 2.5×108 observations recorded by the CryoSat-2 satellite radar altimeter between July 2010 and July 2016. The DEM is formed from spatio-temporal fits to elevation measurements accumulated within 1, 2, and 5 km grid cells, and is posted at the modal resolution of 1 km. Altogether, 94 % of the grounded ice sheet and 98 % of the floating ice shelves are observed, and the remaining grid cells north of 88∘ S are interpolated using ordinary kriging. The median and root mean square difference between the DEM and 2.3×107 airborne laser altimeter measurements acquired during NASA Operation IceBridge campaigns are −0.30 and 13.50 m, respectively. The DEM uncertainty rises in regions of high slope, especially where elevation measurements were acquired in low-resolution mode; taking this into account, we estimate the average accuracy to be 9.5 m – a value that is comparable to or better than that of other models derived from satellite radar and laser altimetry.

Soon after its successful launch in August 2018, the spaceborne wind lidar ALADIN (Atmospheric LAser Doppler INstrument) on-board ESA's Earth Explorer satellite Aeolus has demonstrated to provide atmospheric wind profiles on a global scale. Being the first ever Doppler Wind Lidar (DWL) instrument in space, ALADIN contributes to the improvement in numerical weather prediction (NWP) by measuring one component of the horizontal wind vector. The performance of the ALADIN instrument was assessed by a team from ESA, DLR, industry, and NWP centers during the first months of operation. The current knowledge about the main contributors to the random and systematic errors from the instrument will be discussed. First validation results from an airborne campaign with two wind lidars on-board the DLR Falcon aircraft will be shown.

ESAs Earth Explorer Aeolus was launched in August 2018. Aboard the first spaceborne wind lidar ALADIN (Atmospheric LAser Doppler INstrument) was switched on in early September 2018 and demonstrated the capability to provide atmospheric wind profiles globally from particle and molecular backscatter. In doing so, it will contribute to the improvement in numerical weather prediction (NWP) and the understanding of global dynamics. At the same, it is a major step for powerful and frequency stabilized ultraviolet (UV) lasers for space applications. In parallel, ESA and its partners continue the development of this technology by setting up further ground tests based on Aeolus, and preparing the next milestone with ATLID (ATmospheric LIDar) for the Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) mission. ATLID is currently fully integrated and getting prepared for its on-ground testing.

We present a new Digital Elevation Model (DEM) of the Antarctic ice sheet and ice shelves based on 2.5 × 108 observations recorded by the CryoSat-2 satellite radar altimeter between July 2010 and July 2016. The DEM is formed from spatio-temporal fits to elevation measurements accumulated within 1, 2 and 5 km grid cells, and is posted at the modal resolution of 1 km. Altogether, 94 % of the grounded ice sheet and 98 % of the floating ice shelves are observed, and the remaining grid cells North of 88° S are interpolated using ordinary kriging. The median and root mean square difference between the DEM and 2.3 × 107 airborne laser altimeter measurements acquired during NASA Operation IceBridge campaigns are −0.30 m and 13.50 m, respectively. The DEM uncertainty rises in regions of high slope – especially where elevation measurements were acquired in Low Resolution Mode – and, taking this into account, we estimate the average accuracy to be 9.5 m – a value that is comparable to or better than that of other models derived from satellite radar and laser altimetry.

The main objectives of this paper are to present the status of the CryoSat ocean products and to give an overview of all associated quality control and validation activities. Launched in 2010, the polar-orbiting European Space Agency’s (ESA) CryoSat mission was primarily developed to measure changes in the thickness of polar sea ice and elevation of the ice sheets. Going beyond its ice-monitoring objective, CryoSat is also a valuable source of data for the oceanographic community. The satellite’s radar altimeter can measure high-resolution geophysical parameters from the open ocean to the coast. To enable their full scientific and operational exploitation, the ocean products continuously evolve and need to be quality-controlled and thoroughly validated via science-oriented diagnostics based on multi-platform in situ data, models and other satellite missions. In support to ESA, the CryoSat ocean validation teams conduct this quality assessment for both the near real time and offline ocean products, both over short time scales (daily and monthly monitoring) and long-term stability (annual trends). Based on the outcomes from these quality analyses and feedback from scientific oceanographic community, ESA intends to upgrade the CryoSat Ocean processing chain for Autumn 2017.

Altimeters are active microwave instruments for the accurate measurement of vertical distances (between the spacecraft and the altimeter footprint). The technology determines the two-way delay of the radar pulse echo from the Earth’s surface to a very high precision (to less than a nanosecond). The instrument is also able to measure the power and the shape of the reflected radar pulses. Since the first dedicated altimeter was launched on the Seasat platform in 1978, satellite altimetry has experienced incredible and continuous development as new sensors have been designed and have become operational. The accuracy in range measurements gradually reached values that have produced an extraordinary increase in our knowledge of many aspects of ocean and ice dynamics and variability. Mainly, the evolution of the altimeter transmitter is marked by improvements in pulse compression techniques that have substantially reduced peak power requirements, as reported in [1] and [2], for example. The altimeter missions considered in this paper operate at Ku-band. The choice of frequency is constrained by both the system and the operational requirements. Since a narrow transmitted pulse is required to achieve reasonable range precision, high-frequency operation supports both the large receiver bandwidth and the narrow antenna beamwidth requirements. The upper limit on the operational frequency is constrained by atmospheric attenuation effects that significantly degrade the performance of the altimeter for frequencies > 18 GHz. In some altimetric missions, such as Topex, the radar altimeter instrument includes a C-band transmitter so that ionospheric propagation delays can be accurately measured. Generally, the two-frequency system produces subdecimeter range precision so that very small variations (particularly in the ocean surface) can be detected.

The CryoSat-2 spacecraft is one of the Earth Explorer Opportunity missions of the ESA Living Planet programme. It is operated by the European Space Operations Centre, in Darmstadt. The CryoSat Mission objective, fulfilled by the CryoSat-2 satellite, is to provide global continuous measurements of the ice cover variations on the Polar caps and continental ice sheets plus other areas of land ice, which is being achieved thanks to the use of its multi-mode interferometer radar, SIRAL. Additionally, CryoSat-2 data is being used to support the Oceanography community with respect to the long term sea level monitoring. In April 2014, Cryosat-2 achieved four years of operations, covering six-months of commissioning and the follow on routine operations. Overall, the mission has proven to be very successful and the spacecraft overall performance very reliable. This paper first provides an overview of the CryoSat-2 Ground Segment and the implemented operational concept covering the payload operations planning cycle, automated passes, housekeeping data replay and analysis, followed by an overview of the mission and the in-flight operational status of the Satellite. The remainder of the paper will present details of the main satellite operations carried out in flight, from the post launch anomaly investigation and corrective actions through to routine operations. The routine operations will be described, for example data downlink automation, orbit maintenance manoeuvre execution, Star Tracker operations, debris collision monitoring, platform units maintenance and payload calibrations via Transponder passes. Special operations in support of the mission and also as a consequence of anomalies will be presented, addressing how and why these are executed and the issues encountered. Support to future missions and additional objectives have also resulted in some special operations, and these will be briefly described. The interfaces with the other facilities required to support and enhance the mission will be briefly described. This will include the facilities involved in the planning of routine and special operations, plus how the Flight Operations Segment interfaces with the Processing and Dissemination facilities to provide the data to different users. As conclusions, the need for stable operations to preserve data quality is highlighted and how the evolution of the current operational concepts allows the Cryosat-2 mission to fully support the all of the user communities’ needs.

Satellite radar altimetry, which was initially designed for accurate measurements of sea surface height, has been demonstrated to be suitable for land surfaces as well.

In the frame of GMES preparatory activities led by ESA, ACS has been awarded in 2006 of a contract for the development of a Missions Capacity Planning (MCP) Tool. The GMES MCP project is currently on going under the leadership of ACS and foresees the collaboration of ASTRIUM S.a.S, SPOTIMAGE and INFOTERRA S.a.S as partners of ACS and will continue up to September 2008. The main objective of the GMES Missions Capacity Planning is to allow the assessment, qualification and quantification of the fulfilment of the space observation data requirements of the future and potential operational GMES services beyond 2008, by the imaging space missions dedicated or contributing to GMES. The aim of this paper is then to present the characteristics of the MCP Tool that ACS has developed in the frame of the GMES MCP project. The Tool is based on the MAT SW formerly developed by ACS for ESA which is a multi-mission planning tool. The MCP SW suite however integrates the simulation capabilities offered by MAT and provides ad hoc user interfaces for allowing the definition of GMES Services to be simulated and type of analysis report to be produced. MCP tool development has been successfully completed in September 2007. Today MCP are supporting the Agency in the finalisation of the GMES Data Access Portfolio. Further feature extensions are under discussion to allow the managing of services requiring other types of sensors like the passive microwave ones (i.e. scanning radiometers and sounders) and radar altimeters/scatterometers.

A study by Armitage and Davidson (2014) has shown that the extra information from the CryoSat-2 (CS2) SARIn mode increases the number of valid sea surface height estimates which are usually discarded in the SAR mode due to snagging of the radar signal. As the number of valid detected leads increases, the uncertainty of the freeboard heights decreases. In this study, the freeboard heights estimated by processing CS2 SARIn level 1b waveforms are validated using the information from airborne laser and radar altimetry as well as snow radar measurements acquired during the CryoVEx 2012 and Operation IceBridge 2012 campaigns, respectively. The possible reduction in the random freeboard uncertainty is investigated comparing two scenarios, i.e. a SAR-like and a SARIn acquisition. A very good agreement is found between average airborne and satellite radar freeboards although, at the CS2 footprint scale, they do not show along-track spatial correlation. It is observed that using the extra phase information, CS2 is able to detect leads up to 2300 m off-nadir. A reduction in the total random freeboard uncertainty of ∼ 40% is observed by taking advantage of the CS2 interferometric capabilities, which enable to include ∼ 35% of the waveforms discarded in the SAR-like scenario.

Summarization: With the advent of diverse satellite altimeters and variant measuring techniques, it has become mature in the scientific community, that an absolute reference Cal/Val site is regularly maintained to define, monitor, control the responses of any altimetric system. This work sets the ground for the establishment of a Fiducial Reference Site for ESA satellite altimetry in Gavdos and West Crete, Greece. It will consistently and reliably determine (a) absolute altimeter biases and their drifts; (b) relative bias among diverse missions; but also (c) continuously and independently connect different missions, on a common and reliable reference and also to SI-traceable measurements. Results from this fiducial reference site will be based on historic Cal/Val site measurement records, and will be the yardstick for building up capacity for monitoring climate change. This will be achieved by defining and assessing any satellite altimeter measurements to known, controlled and absolute reference signals with different techniques, processes and instrumentation. Presented on