THE RADIO FREQUENCY PROCESSING UNIT OF THE COPERNICUS IMAGING MICROWAVE RADIOMETER: AN UPDATE

V. Tocca¹, T. Botticchio¹, F. Lolli¹, L. Simone¹, S. Savstrup Kristensen², J. E. Balling²

¹Thales Alenia Space Italy, ²DTU

The Copernicus Imaging Microwave Radiometer (CIMR) programme is part of the Copernicus Expansion Sentinels (CopEx), an Earth-monitoring initiative led by the European Union (EU) and carried out in partnership with the EU Member States and the European Space Agency (ESA) established to fulfil the growing need amongst European policy-makers to access accurate and timely information services to better manage the environment, understand and mitigate the effects of climate change, and ensure civil security.

To ensure the operational provision of Earth-observation data, the Copernicus Space Component (CSC) today includes a series of space missions called ‘Sentinels’, which are being developed by ESA; some of these have already entered their operational life, some are being commissioned, and the remaining are targeted for launch in the coming years.

In the framework of the Sentinels ecosystem, the EC Polar Expert Group (PEG) and Joint EC Communication, identified the need of an Imaging Microwave Radiometry Mission in order to have the capability to observe a wide range of floating sea ice and related ocean parameters in cloudy but non-precipitating atmospheric conditions both day and night. This class of missions is well suited to monitor the Polar Regions if low-frequency (1-37 GHz) multi-band (L, C, X, K, and Ka) measurements are employed.

The Copernicus Imaging Microwave Radiometer mission, the CIMR mission, will provide continuity of current missions monitoring the Polar Regions, notably improved in terms of measurement bands, spatial resolution, temporal resolution and geophysical accuracy in support of Copernicus Services [1].

This article describes the HW architecture and main functionalities of the Radio Frequency Processing Unit (RFPU), which is part of the CIMR programme’s payload instrument. The RFPU is the instrument unit dedicated to the digitization of the incoming analogue signals, digital signal processing of these signals and transmitting the processed signals, both scientific and diagnostic, to the platform via a Space Wire (SpW) interface.

The RFPU is highly configurable from a CAN Bus interface as far as the digital processing Radio Frequency Interference (RFI) core is concerned. Different threshold values and other operational parameters, such as accumulation and integration times, can be set in real time to adjust and modify the RFPU behaviour to cope with different kind of RFIs, leveraging 4 different RFI mitigation algorithms: i) anomalous amplitude, ii) cross-frequency, iii) Kurtosis, iv) Polarimetry.

The FPGAs in the RFPU lodge the VHDL-RTL hard-coded RFI detection algorithms (Anomalous Amplitude, Cross-frequency, Anomalous Polarimetric Amplitude, and Kurtosis) using time-frequency division of each sample into a matrix of time bins and spectral sub-samples [2]. The downlinked data for all samples consist of the full modified Stokes vector, both filtered and non-filtered. Additionally it is optionally to downlink diagnostic data containing both the full modified Stokes vector and the fourth order moments for each matrix element in the time-frequency matrix.

An extensive test campaign is being done to thoroughly test the Unit in different RFI scenarios and verify its performances.

This article describes the HW architecture and main functionalities of the RFPU devised for the CIMR programme and gives a status update of the current development and the ongoing activities.

REFERENCES

1. N. Skou and D. Le Vine, “Microwave Radiometer Systems: Design and Analysis”, second edition, Artech House, 2006.

2. Steen S. Kristensen, Jan E. Balling, Sten S. Søbjærg, Niels Skou, “On-Board Radio Frequency Interference Processor for the Copernicus Imaging Microwave Radiometer”, IGARSS 2022 – 2022 IEEE International Geoscience and Remote Sensing Symposium.