The MetOp-SG Programme is the follow-on to the current, first generation series of Meteorological Operational (MetOp) satellites, which is now established as a cornerstone of the global network of meteorological satellites. MetOp-SG is required to ensure the continuity of these essential meteorological observations, improve the accuracy / resolution of the measurements, and also to add new measurements and missions.

MetOp-SG is being implemented in collaboration with EUMETSAT. ESA will develop the prototype MetOp-SG satellites (including associated instruments) and procure, on behalf of EUMETSAT, the recurrent satellites (and associated instruments).

MetOp-SG consists of two series of satellites (Satellite A and Satellite B), each carrying a complementary suite of instruments and operating in a low Earth orbiting, polar orbit identical to that of the first generation. The Industrial contract is led by Airbus Defence and Space SAS, France as Prime contractor for the Satellite A series, and Airbus Space and Defence GmbH, Germany as Prime contractor for the Satellite B series. The planned launches of the first of each series of satellites are scheduled in 2022 and 2023, respectively, with successive launches planned every 7 years to ensure at least 21 years of operations.

The scope of this paper is to provide an up-to-date overview of the MetOp-SG space segment architecture, satellites configuration and key features and characteristics, orbit and space to ground communications links, together with a brief summary presentation of the MetOp-SG instruments (which will be covered in more depth in a separate paper). The paper will highlight the high commonality between both series of satellites, in terms of design, interfaces, development, verification and operations, and will also present the actual development status of the ESA MetOp-SG Programme, for which the Critical Design Review (CDR) for Satellite A has been successfully concluded, with the CDR for Satellite B planned in 2019.

The Meteosat Third Generation (MTG) Programme is being realised through the well-established and successful Cooperation between EUMETSAT and ESA. It will ensure the future continuity with, and enhancement of, operational meteorological (and climate) data from Geostationary Orbit as currently provided by the Meteosat Second Generation (MSG) system, the last of which MSG4/MET11 has been successfully launched and commissioned in 2015 and is currently in storage (in orbit) as a back-up to MET 9 and MET10.

The industrial Prime Contractor for the Space segment is Thales Alenia Space (France) with a core team consortium including OHB-Bremen (Germany) and OHB-Munich (Germany). This contract includes the provision of six satellites, four Imaging satellites (MTG-I) and two sounding satellites (MTG-S), which will ensure a total operational life of the MTG system in excess of 20 years.

The MTG-I and MTG-S will bring to the meteorological community a series of satellites for continuous high spatial, spectral and temporal resolution observations and geophysical parameters of the Earth based on sensors from the geo-stationary orbit. In particular, the imagery mission MTG-I will bring an improved continuation of the MSG satellites series with the Flexible Combined Imager (FCI) a broad spectral range (from UV to LWIR), covering extensive areas (global and regional), and within a variety of improved different time scales to continue and enhance the MSG services. Furthermore, MTG-I carries additional payloads composed of the Lightning Imager (LI) for lightning detection for early convection detection, the Data Collection & Dissemination and Search & Rescue Missions. The MTG-S will bring unprecedented features to the end users with a high spectral resolution (0.625 cm-1) and a high spatial resolution (4 km SSD) of the IRS instrument. The IRS mission will provide the capability to determine the altitude from which emissions emanate, providing a capability for vertical profiling of the atmosphere with respect to composition and temperature (water vapour tracking & profiling, and temperature profiling), thus allowing vertical wind vectors measurement. The IRS will support nowcasting and very-short range forecasting (VSRF), 3D fields of wind, temperature and humidity, and hence moisture convergence and convective instability, to help improve warnings of location and intensity of convective storms. In addition, within its detection bands IRS can provide accurate measurements of many atmospheric constituents including H2O, O3, NO, N2O, CO and CO2. Moreover, thanks to the GMES Sentinel-4 (S4) sounding mission embarked on MTG-S, the mission will achieve through this UVN Instrument with three spectral bands (UV: 305 - 400 nm; VIS: 400 - 500 nm, NIR: 750 - 775 nm) with spatial sampling distance around 8 km and a spectral resolution nm. The combination of the IRS and the UVN missions can support air quality and chemistry missions for the atmospheric science from geostationary.
The MTG space segment activities are at present focussed on the manufacturing and testing activities, from equipment level to the platform and instrument assemblies. Many development units/equipment have completed testing, undertaken their respective tested CDRs successfully, and the flight hardware is now being manufactured. FCI and LI CDRs are completed and the MTG-I is running.

This paper will provide an overview of the MTG satellites series features and their development status. It will provide the achievable performances wrt the associated mission requirements and furthermore, this paper will describe the improvements it will bring wrt the MSG.

The Advanced Baseline Imager (ABI) is the primary instrument on the 17th Geostationary Operational Environmental Satellite (GOES-17) series for weather and environmental monitoring. Following the launch of GOES-17 on 1 March 2018, ABI (flight model 2) experienced a degradation in its thermal system that limits ABI’s ability to shed solar heat load. The originally-specified operating temperature of ABI’s focal plane could not be maintained resulting in reduced imaging capability.

A combined government/vendor team was tasked with optimizing the operation of ABI to recapture as much performance as possible. By modifying the operational configuration, it was possible to regain imaging capability in all 16 channels for half of the year with thermally stable focal plane. The remaining half of the year is limited to degradation on 9 channels for only a few hours per day when the temperature of the focal plane rises above its nominal temperature. During the time of anomalous focal plane temperature, the original image radiance calculations produce calibration errors due to drift of detector offset and gain due to temperature drift between the time of earth measurements and associated space and blackbody reference measurements that were used to derive offset and gain.

This work will present GOES-17 ABI performance improvement achieved using algorithms that predict spacelook and blackbody measurement values at the time of earth measurements. Rather than using spacelook and blackbody measurements before and after particular earth measurements, only measurements prior earth measurements can be used due to temporal operational requirements. This predictive approach benefitted from updating the GOES-17 ABI measurement timeline to increase frequency of blackbody measurements and move spacelook measurements in positions that provide more consistency. The residual calibration error is assessed and performance improvement of higher-level products is evaluated.

Developed by CNES in partnership with Eumetsat, the IASI instrument (Infrared Atmospheric Sounding Interferometer) is flying on the European MetOp series of weather satellites since 2006. Besides acquiring temperature and humidity data, IASI also measures more than 25 other atmospheric components with high precision and is supporting the efforts of scientists monitoring Earth’s climate. To ensure continuity of service, CNES is working on the IASI-NG next-generation instrument. It will continue and improve the IASI mission in the next decades (2020-2040) in the field of operational meteorology, climate monitoring, characterization of atmospheric composition related to climate, atmospheric chemistry and environment. The performance objective is mainly a spectral resolution and a radiometric error improved by a factor of two compared with the IASI first generation ones.

While IASI was based on a Michelson interferometer, the measurement technique of IASI-NG is based on wide field passive Fourier Transform Spectrometer (operating in the 3.5 - 15.5 μm spectral range) based on an innovative Mertz compensated interferometer to manage the so-called self-apodization effect and the associated spectral resolution degradation. The instrument also has an imager that enables co-registration of the sounding points with the images acquired by the multispectral imager on the platform.

The main results of IASI mission in terms of radiometric and spectral performances will be recalled, with recent advances in terms of non-linearity corrections. Then, we will give a status of the development of IASI-NG instrument, with a special focus on data processing from level 0 raw data to level 1c, that is the removal of instrument dependent variations of the spectral response, apodization, radiometric and spectral calibration. A key aspect is the quality of the Instrument Spectral response Function (ISRF) estimation process, supported by additional in-flight measurements (metrology based on 5 lasers to determine the path difference but also monitoring of wave-surface changes and Fabry-Perot device).

As part of the Copernicus programme, EUMETSAT operates the low Earth orbit (LEO) Sentinel-3 (S3) mission that includes two optical instruments with medium spectral resolution and very high spatial resolution: the Ocean and Land Colour Instrument (OLCI) and the Sea and Land Surface Temperature Radiometer (SLSTR). With 4 platforms (A to D), S3 promises to deliver a long time series observation over 20+ years. The first platform S3 A has been flying since 16 February 2016, and the second platform was successfully launched on 25 April 2018. Built upon the legacy of the Envisat mission, the S3 OLCI and SLSTR sensors include a series of high improvements compared to the past instruments of MERIS and AATSR on ENVISAT: e.g. improved global coverage (~2-3 days sun-glint free), a higher number of spectral channels (21 for OLCI vs. 15 for MERIS, 9 for SLSTR vs. 7 for ATSR), and higher spatial resolution (300 m for OLCI, 500 m – 1km for SLSTR at nadir). In addition to its initial objectives (ocean and land), the operational S3 mission has a strong potential for weather nowcasting, meteorological, and long term global climate change applications. For those purposes, EUMETSAT is producing several near-real time (NRT) high quality essential products covering the topics of aerosols, clouds, winds, and water vapour. In this presentation, we will address the status of these products, their identified qualities, the on-going activities for improvements, and the interest for users (e.g. meteorological services). Some of these products are already being disseminated; new activities have been initiated for their evolutions; others are under preparation and evaluation.

SLSTR is a conical scanning imaging radiometer with along-track dual-view technique: a high number of scenes is then measured twice in a short time (~30 sec) with a different viewing angle. This dual-view technique, combined with 5 solar channels from the visible at 554 nm to the shortwave infrared (SWIR) at 2.25 um allows then a better distinction of aerosol scattering and surface reflectance. A multi-spectral aerosol optical depth (AOD) processor is under development in the frame of an ESA contract. In order to ensure its high and long-term quality, EUMETSAT has initiated key activities to support SLSTR AOD performance evaluation and potential evolution. EUMETSAT is also preparing a total column water vapour (TCWV) product by relying on a combined use of the dual-view and the thermal infrared channels at 10.8 and 12 um. Such an approach was successfully demonstrated with the AIRWAVES v2 algorithm for the (A)ATSR instruments. Finally, a dual SLSTR atmospheric motion vector (AMV) prototype is under development by EUMETSAT based on the experience gained with AVHRR product from the Metop-series of satellites. It will exploit the SLSTR 10.8 um channel from S3 A and B successive passes. The key regions for the users, i.e. high latitude areas, and especially the 40-60 deg. latitude band, will be covered.

OLCI is a push-broom imaging spectrometer with notably 5 channels (2 more than MERIS) in the 753.75-767.5 nm near-infared (NIR) spectral range, including 3 in the O2-A absorption. These channels will be used to derive a new EUMETSAT OLCI cloud top pressure (CTP) product, based on a 1D-var baseline approach. OLCI also includes 4 channels with water vapour absorption: 885 nm, 900 nm, 940 nm, and 1.02 um. TCWV is already retrieved over all types of surfaces, following the MERIS-like baseline algorithm. Following user feedbacks, an evolution activity has started to improve the quality over water surfaces, in particular in transition areas between medium glint and off-glint.

To process and deliver all these NRT products, EUMETSAT has extended its existing dissemination services and the Copernicus S3 ground-segment capabilities. The impacts of all these products, or their evolution, are expected to be numerous and will be highlighted in this presentation with a list of aimed users. For example, the importance of aerosol information to the numerical weather prediction (NWP) community and the national meteorological services (NMSs) is increasingly being recognized due to the significant influence of aerosols on the radiation budget and their key role in cloud processes and precipitation. A number of NMSs are actively exploring the possibility of assimilating aerosol observations (e.g. https://www.metoffice.gov.uk/research/climate/earth-system-science/aerosols). Assimilation of satellite wind products, such as AVHRR, in NWP models has shown positive impacts on the forecast scores at several meteorological agencies (e.g. ECMWF, DWD, MET Norway etc…). There is a clear need to increase the number of observations in the 40-60 deg. latitude band. Furthermore, OLCI CTP can support the EUMETSAT SLSTR AMV analyses. OLCI TCWV product also represents an asset for NWP and meteorological services.

High latitude regions, i.e. the Nordic and Arctic regions for Europe, are not sufficiently covered by near-real-time observations of Earth Observation systems for nowcasting, weather forecasting, or operational support applications, when compared to the coverage available from GEO for mid or low latitudes. For these Northern regions, users can only rely on assimilation of measurements from LEO polar orbiting satellites. This means a much lower repeat coverage of hours to sub-hour for LEO versus 10 to 15 minutes for GEO, and also the need to accommodate different geometries and sensors to get a complete picture of the regions. Thus there is a recognised user need for providing similar services in these regions to the ones available for mid and lower latitudes. It is a well-established consensus that this need could be best met using a small constellation of multispectral passive optical instruments, similar to the GEO ones, and deployed on satellites in a highly elliptical orbit (HEO), nominally using the 63.4 degrees critical inclination. Such mission concepts are or were addressed by Nordic nations. This included the PCW concept from Canada, now cancelled, and the Arktika Russian mission, currently in development.
As such, ESA with EUMETSAT have been carrying out activities since 2016 for the study and potential development of such HEO missions. The paper will provide an overview of past, present, and upcoming activities. The main focus of this work currently is the Arctic and Nordic Imager, a hosted payload mission concept. The objectives of the mission are to provide near-real-time nowcasting and operational governmental services, to characterise the linkage of Arctic and tropical atmospheres, and possibly to provide operational demonstration of near-real-time day/night imaging.
This presentation will thus report on the results of the various ESA activities, focusing on the results of a recently completed user needs study that investigated use cases and spatial, spectral, and radiometric requirements for the mission, such as that they are similar to those of the MTG FCI instrument, but with additional capacities where desirable for the Arctic and Nordic regions specifically.