MetOp-Second Generation is a follow-on system to the first generation series of MetOp (Meteorological Operational) satellites, which currently provide operational meteorological observations from polar orbit. It is part of the EUMETSAT Polar System Second Generation (EPS-SG). From a space segment perspective, MetOp-SG consists of two series of satellites, i.e. Satellite-A and Satellite-B with three satellites of each series. The aim of the mission is to ensure continuity of the essential operational meteorological observations from polar orbit - in the 2022-2042 timeframe - to improve the accuracy, resolution, dynamic range of the measurements and to provide new measurements/instruments compared to EPS.
The paper will present the MicroWave Sounder (MWS) instrument. MWS is a cross-track scanning total power microwave radiometer. MWS is embarked on Satellite-A. It provides temperature and water vapor profiles and in addition information on cloud liquid water. MWS has 24 channels in total, covering frequency range from 23 GHz up to 230 GHz. All MWS channels are measured with a single polarisation (QV or QH). The MWS footprint ranges from 40 km at lowest frequencies to 17km at higher frequencies. The MWS instrument scans +/-49 degrees around nadir and provides contiguous or overlapping spatial sampling for all channels. MWS has a non-uniform scanning profile, which maximises the scene viewing time. A quasi-optical system is used to co-locate all channels into one “main beam”.
The MWS structural and thermal model (STM) has completed all testing at instrument level and at complete satellite level, confirming the mechanical and thermal design. The MWS engineering model (EM) test campaign is completed. The MWS Proto-Flight Model (PFM) is under its environmental and calibration test campaign and will be shipped to the Satellite-A Prime for integration, testing and launch preparation. For the MWS PFM and the recurrent models FM2 and FM3, a complete calibration system was developed to calibrate the MWS instrument in vacuum over operational temperature range and over the complete field of view. Final instrument verification will be performed during the thermal vacuum test campaign and the yearly storage health check of MetOp-SG Satellite-A. For these campaigns, specific calibration targets have been developed as well.
This paper will present the MWS instrument, including test results available. The MWS calibration approach will be described at instrument level. In addition, based on measurement results on-ground, a final performance prediction for flight will be given.
The contribution of our colleagues at RAL, Deimos, TAS Italy, DA Design, Norspace, SENER and Thomas Keating is key to meet the challenging MWS instrument mission requirements.

MetOp-SG is the follow-on of the first generation series of Meteorological Operational (MetOp) satellites, which currently provides operational meteorological observations from polar orbit. MetOp-SG Program is implemented in collaboration with EUMETSAT where ESA is developing satellite prototype, associated instruments and will procure, on behalf of EUMETSAT, recurrent satellites. MetOp-SG will consist of two series A and B of satellites with three satellites of each series, each of which designed for an in-orbit lifetime of 7.5 years to provide continuous operation for more than 20 years.
The paper will present a polarimeter instrument namely the Multi-viewing, Multi-channel, Multi-polarization Imager (3MI) instrument, embarked on Sat-A.

Polarimetry is considered today to be a crucial technique in atmospheric remote sensing for characterization of airborne aerosol parameters, their particle types and sizes, aerosol optical depths, refractive index, sphericity, height index and absorption. When such products will be used as constraints to climate models they will provide Improved Air Quality Index and Aerosol Load Masses for different particles sizes and therefore ambient particulate air pollution. Being aerosol properties fully and unambiguously derivable only by measuring Top of Atmosphere polarized radiances at several wavelengths and several viewing angles, 3MI is designed for it. 3MI will contribute as well to Numerical Weather Prediction and as secondary objective to improve cloud characterization in terms of cloud phase, microphysics (phase and effective particle size), height and optical depth. 3MI is therefore a key role player in the future of climatology, air quality and pollution characterization.

The 3MI Multi-channel and Multi-polarization properties are achieved with successive acquisitions of polarized and un-polarized spectral bands performed using a rotating filter wheel, which interposes and changes the Band Pass filters in the optical path of both the VNIR and SWIR channel. VNIR’ one covering 410 nm to 910 nm and SWIR’ one from 1370 nm to 2130 nm. Filter wheel includes two concentric coronas of filters stacks slots. The external one dedicated to VNIR channels - 21 slots and 1 shutter - and the internal one dedicated to SWIR channels - 9 slots and 1 shutter. VNIR’ slots allow to acquire 6 spectral bands with 3 different polarization axes orientation (+60°, 0°, -60°) and 3 un-polarized spectral bands. SWIR’ slots allow to acquire 3 spectral bands with 3 different polarization axes orientation (+60°, 0°, -60°). The concentricity of the two coronas allows co-registration between VNIR and SWIR channels.
The 3MI Multi-viewing property is achieved by performing forward, nadir and backward observations of the same target on Earth at different instants, using a push-broom scanning concept, a very wide-field optical design and matrix focal planes. Indeed, the VNIR and SWIR objectives are designed to provide wide angle FoV unvignetted images (+/-57° for VNIR and +/-53.5° for SWIR), thus allowing to acquire 14 views in VNIR spectrum and 12 views in SWIR spectrum for the same ground target.
In parallel an E2E simulator composed by the combination of an Instrument Data Simulator (IDS) and a Ground Processor Prototype (GPP) has been developed. GPP will be exploited to support instrument on-ground calibration and performances verification up to Level 1b1.
This paper will present the 3MI instrument design, main performances and industrial progress. 3MI on-ground calibration will be presented as well with prediction of the final performances based on PFM calibration campaign results.

MetOp-SG is the follow-on to the current, first generation, series of 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, to improve the accuracy and resolution of the measurements, and also to add new measurements/missions.

The MetOp-SG Programme is being implemented by ESA in collaboration with EUMETSAT. ESA is developing the prototype MetOp-SG satellites, including most of the associated instruments, and is procuring, on behalf of EUMETSAT, the recurrent satellites. ADS is the prime contractor for the development and production of the 2 series of MetOp-SG satellites and leads an European industrial consortium including the entities responsible for the development of 6 instruments from the total of 10 that are part of the MetOp-SG Program. RUAG-Space AB is part of this consortium and is the company developing the Radio Occultation instrument.

The MetOp-SG will consist of two series of satellites (Sat-A and Sat-B), with three satellites of each series. This mission will provide continuous operation from polar orbit for more than 20 years.

RO (Radio Occultation) instrument will be embarked on both satellites A and B. The RO mission primary objectives are to provide temperature and water vapour profiles. The RO measurements will also be used to derive ionospheric information, the tropopause height, the height of planetary boundary layers and surface pressure.

The RO instrument is a GNSS receiver tracking signals from navigation satellites at the limbs of the earth. The occultation signals are measured via two occultation antennas, one facing the satellite velocity direction and the other one the satellite anti-velocity direction. A third antenna on the zenith side is tracking satellites for determination of the satellite position, velocity and time.

The RO instrument will provide 1850 occultation measurements per day, thanks to simultaneous tracking of Galileo, GPS and BeiDou satellites. The instrument has capacity to support a 4th constellation in a possible future upgrade for e.g. GLONASS. GNSS signals on L1 and L5 frequencies are tracked by means of both Closed loop and Open loop tracking. Both data and pilot signal components can be tracked simultaneously. This allows achieving an accuracy of the bending angle retrieval better than 0.5 µrad at 35km altitude.

This paper will present the RO instrument design, main performance and industrial progress. The RO Prototype Flight Model (PFM) was successfully delivered to ADS-Toulouse in 2020, and the Flight Model 2 (FM2) to ADS- Friedrichshafen in 2021.

MetOp-SG is the follow-on to the first generation series of Meteorological Operational (MetOp) satellites, currently providing operational meteorological observations from polar orbit. MetOp-SG is required to ensure the continuity of these meteorological observations, to improve the accuracy, resolution of the measurements, and also to add new measurements/missions. The MetOp-SG Programme is being implemented in collaboration with EUMETSAT. ESA is developing the prototype MetOp-SG satellites, including many of the associated instruments, and will procure, on behalf of EUMETSAT, the recurrent satellites. The MetOp-SG will consist of two series of satellites (A and B), with three satellites in each series. This mission is part of the EUMETSAT Polar System Second Generation (EPS-SG) and shall provide continuous operation for more than 20 years, with each satellite being designed for an in-orbit lifetime of 7.5 years.

The Wind Scatterometer (SCA) instrument, the successor of ASCAT, will be embarked on all B satellites. The SCA mission primary objectives are to provide measurements of the ocean surface wind vectors, soil moisture, snow equivalent water and sea-ice extent and type. An Earth coverage of 99 % will be reached within two days, with nominal spatial resolution of 25 km.

The SCA is a real-aperture pulsed imaging radar operating in C-band (5.355 GHz). The SCA comprises the SCA Electronic Subsystem (SES) and the SCA Antenna Subsystem (SAS). The SES commands and controls the SCA instrument, allowing RF pulse transmission and echo reception. The SAS comprises 6 antennas, employing radiating slotted waveguide panels (SAS Panels) internally fed by bar-line (true time delay) as well as waveguide Beam Forming Network (BFN), and are configured in 3 antenna-pair assemblies (one MID and two SIDE antenna assemblies). After launch and release of the Hold Down and Release Mechanisms (HDRM) the two side antenna pairs (4 antennas) are deployed using the two Deployment Mechanisms (DLM). These SIDE antennas are all vertical polarised. Both MID antennas are dual-beam, with one beam being vertically and the other horizontally-polarised. Each of the antennas (HH, HV/VH and VV) acquire a continuous image of the normalized radar backscatter coefficient from two 650 km wide swaths at each side of the sub-satellite track.

In comparison to ASCAT, the required spatial resolution of the SCA is doubled, the swath width is increased and polarimetric capability is added. The main challenge of SCA is that accurate wind field measurements (wind speed and direction) require stringent radiometric stability and low bias over both orbit and lifetime. This has been addressed by very stable antennas and by a sophisticated internal calibration scheme covering the SCA electronic boxes: Digital Control Unit (DCU), RF Up-converter (RFU), High Power Amplifier (HPA) employing a Vacuum Tube Amplifier (VTA), High Power Redundancy Switch (HRS), Harmonic Filter (HFIL) and finally the SCA Front End (SFE) guiding the radar pulses and echoes to and from the relevant antenna ports.

This paper will present the SCA instrument design, calibration concept, main performance and industrial progress. The SCA Critical Design Review Close-Out was successfully achieved in March 2020. Testing of SES EM and SAS PFM was completed in 2021.

The contribution of our colleagues at CRISA (DCU), TAS Spain (RFU), Airbus Germany (HPA), CPI Canada (VTA), Honeywell UK (HRS, HFIL, SFE), SENER Spain (HDRM, DLM), Airbus Italy (BFN) and RUAG Sweden (SAS Panels) is key to meet the challenging SCA instrument mission requirements.

MetOp-Second Generation is a follow-on system to the first generation series of MetOp (Meteorological Operational) satellites, which currently provide operational meteorological observations from polar orbit. It is part of the EUMETSAT Polar System Second Generation (EPS-SG). From a space segment perspective, MetOp-SG is two series of satellites (Satellite-A and Satellite-B) with three satellites of each series. The aim of the mission is to ensure continuity of the essential operational meteorological observations from polar orbit, in the 2023-2043 timeframe, to improve the accuracy, resolution, dynamic range of the measurements and to provide new measurements/instruments compared to the first generation of EUMETSAT Polar System (EPS).
MWI (MicroWave Imager) is one of the five sensors embarked on Satellite-B and it is a conical scan total power microwave radiometer aimed at providing geolocated measurements in 26 channels ranging from 18.7 GHz up to 183.31 GHz, offering dual polarisation measurements up to 89 GHz for cloud and precipitation observations as well as water vapour and temperature gross profiles. Channels in the oxygen absorption regions between 50 and 60 GHz and at 118 GHz are one of the innovative features of MWI, enabling the retrieval of information on weak precipitation and snowfall, typically affecting the weather at high latitudes.
The MWI instrument has a direct heritage from its predecessors as the Special Sensor Microwave/Imager (SSM/I), the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and the Global Precipitation Mission Microwave imager (GMI). MWI will provide global microwave imaging data useful to retrieve information on precipitating and non-precipitating liquid and frozen hydrometeors, information on water vapour content and relevant surface characteristics (e.g. windspeed over ocean and sea-ice coverage).
The instrument collects the radiation coming from the Earth by means of a rotating antenna, composed by an offset parabolic reflector and a feed-horns cluster. The Earth is acquired at an angle of +/- 65° in azimuth for the fore view. Every rotation, two other angular sectors are used to calibrate the measurements, with the instrument looking at cold sky and at a fixed microwave calibrated target.

The required radiometric sensitivity calls for having the receivers as close as possible to the horns, thus implemented in the rotating part. The purpose of the receivers is to deliver signals, the magnitude of which is proportional to the incoming microwave power in the relevant band (i.e. brightness temperature of the scene). Depending on specific channel requirements and technical constraints, direct detection or heterodyne configuration are used. Two units in the rotating part, the Front-End Electronics (FEE) and the Control and Data Processing Unit (CDPU), perform the power distribution and receivers signal digitization. A rotating joint (PDTD) allows the transfer of the electrical signals (digitized radiometry data, TM/TC, power supplies, heater lines) between the fixed part and the rotating part.

In parallel to the hardware development of the instrument, a first version of the L1B end-to end simulator, composed by the on-board (Instrument Data Simulator – IDS) and the on-ground (Ground Processor Prototype – GPP) data processor, has been developed . The GPP has been already used to verify the performances of the MWI Engineering Model on-ground and will be also exploited for a cross-validation with the operational MWI ground processor during the satellite in-orbit verification phase.

After the finalization of the instrument design, the instrument qualification has started with a Structural Thermal Model (STM) environmental test campaign (vibration, acoustic, shock, TVAC) and continued with the Engineering Model (EM) testing finishing by the end of 2021. The EM testing is including radiometric performance under Thermo-Vacuum conditions that will be presented at the symposium. Low channels antenna testing has also been performed on the refurbished STM confirming good correlation between modeling and testing. High frequency channels antenna testing is planned to be performed on the instrument Proto Flight Model (PFM) in summer 2022. Instrument PFM is currently under integration with all the critical PFM units delivered to the instrument prime.

The present paper will provide an overview of the MWI instrument objectives and design and present the latest development status and performance assessment.

MetOp-Second Generation is a follow-on system to the first generation series of MetOp satellites, which currently provide operational meteorological observations from polar orbit. It is part of the EUMETSAT Polar System Second Generation. From a space segment perspective, MetOp-SG is a series of two parallel satellites (Satellite-A and Satellite-B) with three satellites each. The mission will ensure continuity of the of essential operational meteorological observations from polar orbit in the 2022-2042 timeframe. It is aimed to improve the accuracy, resolution and dynamic range of the measurements and to provide new measurements/instruments compared to EPS.
ICI (Ice Cloud Imager) is one of the five sensors embarked on Sat-B and it is a conically scanning total power millimeter and sub-millimeter wave radiometer. It will provide unprecedented ice cloud and in particular cirrus cloud observations such as cloud ice effective radius and cloud ice water path with a limited altitude information.
ICI is a novel instrument. It will deliver calibrated and geolocated global data in 13 channels between 183 GHz and 664Ghz in 5 frequency bands. Observations with a 3dB footprint of 16km are made at an incidence angle of 53° with an overlap of 40%.
The instrument collects the radiation coming from the Earth by means of a rotating antenna (45rpm), composed of an offset parabolic reflector and a feed-horn cluster. The scene is acquired at an angular range of +/- 65° in azimuth with respect to the flight direction. Two other angular sectors are used to calibrate the instrument looking either at cold sky or at a temperature stabilized hot calibration target once per turn.

The instrument consists of a rotating part and a fixed part. The rotating part contains the receiver front end, the back ends for the spectral detection and the control data processing unit providing the power to the rotating part and the communication to the fixed part. The rotating part is covered under a sunshield. The fixed part contains the instrument control unit the scan electronics and the calibration assembly composed of the hot calibration target and the reflector for the cold-sky view. A scan mechanism controlled by the scan electronics and a power and data transfer device connect both parts of the instrument.

In parallel to the hardware development of the instrument, a common end-to-end simulator for ICI and MWI is under development. It consists of the instrument data simulator and the ground processor prototype (GPP). The GPP will also be exploited to verify the performances of the ICI models on-ground and for a cross-validation with the operational ICI ground processor during the satellite in-orbit verification phase.

The test campaign of the engineering model has successfully been completed. The integration of the proto flight instrument model (PFM) is ongoing. The environmental and radiometric performance test campaign of the PFM will start in March 2022 followed by the EMC and the antenna test.

This paper will provide an overview of the ICI instrument objectives and design and present the latest development and performance status.