MICROWAVE SOUNDER FOR METOP-SG SATELLITE-A INSTRUMENT STATUS AND IN-ORBIT RADIOMETRIC PERFORMANCE

G. Tennant¹, M. Newey¹, G. Sykes¹, S. Dutta-Chowdhury¹, B. Grandclaude², D. Schobert³, A. Graziani³, M. Labriola⁴

¹Airbus Defence and Space Ltd, ²AIRBUS, ³ESA/ESTEC, ⁴EUMETSAT

The Microwave Sounder (MWS) will serve weather and climate applications from launch in 2025, until at least 2047.

MWS is a total power radiometer that has been selected by ESA as part of the MetOp-SG program, with Airbus Defence and Space Ltd, chosen as the instrument prime contractor. MWS measures the brightness temperature at various altitudes and delivers calibrated and geo-located atmospheric temperature and water-vapour sounding data, in all weather and illumination conditions. MWS is therefore an essential instrument for the provision of operational meteorology, offering significant improvements in measurement performance over MetOp First Generation and indeed all microwave sounders currently operating on meteorological satellites.

MWS measures the total power, atmospheric brightness temperature in 24 channels over the spectral range from 23.8 – 229 GHz. Footprints are ranging from 40 km at the lowest frequency to 17 km at the highest frequencies. The 24 channels covering 7 frequency bands, split the Earth radiation into the required frequencies for Numerical Weather Prediction (NWP). The 14 channels in the 50.3 GHz to 57.6 GHz band are fully redundant.

The MWS program of three instruments has completed at instrument level. Whilst the FM2 and FM3 instruments are in long-term storage with their respective satellites at the MetOp-SG Satellite Prime in Toulouse, the Proto-flight model (PFM) has been launched aboard the first Satellite-A on 12th August 2025. One week later on 20th August, the instrument was powered on, and one day later the first science was retrieved. This heralded the start of the In-Orbit Validation (IOV) campaign, where several in-orbit tests would be performed to validate instrument functionality and performance.

The first of these tests (IOT-1) concentrated on ensuring that receiver channel gain was optimised and that receiver NEdT and Allan Variance performance was comparable to on-ground test results.

The next test (IOT-8) switched the instrument scan cycle to acquire its cold space calibration view in each of the three pre-programmed positions. This was to determine if any space views were contaminated by near-field platform obstructions.

Subsequent tests involved tuning the ground processor to correctly flag and ignore the presence of the moon in the field of view (IOT-6), to verify the geo-location of the footprint (IOT-7) and to verify the scan angle bias in the earth scene by means of a satellite roll manoeuvre which points the instrument’s earth scene towards deep space (IOT-9).

This paper will present the results and conclusions of the MWS instrument IOV phase via the data processing performed to level 1b with the specific MWS Ground Processor Prototype (GPP), and key performance parameters verified by dedicated instrument validation software.