THE FRONTEND OF THE ICE CLOUD IMAGER ONBOARD THE METOP SATELLITE B

N. Wehres¹, G. Sonnabend¹, M. Brandt¹, J. Nies¹, A. Walber¹

¹Radiometer physics GmbH, Werner-von-Siemens Str. 4, 53340 Meckenheim, Germany

RPG (Radiometer physics GmbH) has been awarded to design, build, integrate and test the frontend for the Ice Cloud Imager (ICI) for the MetOp (meteorological Operational) Satellites Second Generation. The instrument is developed under Airbus Spain and ESA management and is an integral part of the second generation EUMETSAT Polar System.

ICI is a microwave / submillimeter wave radiometer and will provide a unique frequency range that will extend (double) the current frequency coverage of meteorological satellite applications. Currently, the Arctic Weather Satellite (AWS) with its 325 GHz receiver provides the highest frequency coverage for weather applications which is delivering data since September 2024. The 325 GHz receiver of AWS was also built by RPG.

The main topic of this presentation will be on the ICI frontend integration and testing. The frontend consists of a total of 6 receivers operational between 183 and 664 GHz. These are split in 13 ICI-channels. The test campaign will be discussed, and results including the stability and sensitivity of the individual receivers will be presented. Additionally, results from the vibration and EMC testing as well as thermal vacuum tests on the frontend will also be shown. In general, the noise temperature and short-term gain stability (1/f) of the individual receivers are key aspects to ensure the desired sensitivity at instrument level. The noise temperature is measured throughout the test campaign using the Y-factor method and shows consistent results ranging from 600 K for the 183 GHz receiver to 2300 K for the 664 GHz receivers (Ref 1, Ref 2).

The short-term gain stability is also determined and ensures that all receivers are stable up to 15s integration time, which is a mission requirement. This in turn yields a NEDT of 0.5 K up to 1.6 K (Ref 3) for the PFM instrument. This demonstrates state-of-the-art radiometric sensitivity performance and sets a reference for the coming millimeter and sub-millimeter wave instruments dedicated to atmospheric remote sensing and weather prediction.

RPG has so far delivered the PFM-ICI-frontend, FM2-ICI-frontend and FM3-ICI-frontend to Airbus Madrid where the integration of the frontend into the instrument takes place. Launch of the PFM satellite B is foreseen for spring 2026. This new generation of Metop satellites will extend the water vapor and ice cloud observations from the current ESA/EUMETSAT MetOp program over the 2026-2046 timeframe. Each of these instruments is designed to cover a minimum of 7.5 years of lifetime.

References:

1. B. Thomas et al., “Radiometric Noise Characterization of the 183-664 GHz Front-End Receivers for the MetOp-SG ICi Cloud Imager instrument – prospects for future missions”, IEEE/MTT-S International Microwave Symposium – IMS, 2023

2. B. Thomas et al., “Submillimeter-wave receiver developments for ICI onboard MetOP-SG and ice cloud remote sensing instruments”, IEEE International Geoscience and Remote Sensing Symposium, 2012

3. A. Andrés-Beivide, “MetOp-SG ICI Cloud Imager – The Story Continues!”, Proceedings of the European Microwave Week, Workshop WM01 “EuMC: Space (Sub)Millimetre-Wave Receivers for Earth Observation and Planetary Science”, 2024