EVOLUTION OF THE RADIO FREQUENCY INTERFERENCE (RFI) ENVIRONMENT IN NORTHERN CANADA: A COMPARISON OF UWBRAD AND LOMIRAD 500-2000 MHZ DATA FROM LOW FREQUENCY MICROWAVE RADIOMETER MEASUREMENTS OVER NORTHERN CANADA

H. Ellzey¹, M. Andrews¹, J. Johnson¹, M. Brogioni², F. Montomoli², M. Ledu-Leballeur², G. Macelloni²

¹The Ohio State University, ²CNR-IFAC

Polar regions play a fundamental role in the Earth climate system. Despite their importance, our knowledge of cryospheric processes remains limited due to their remoteness, harsh conditions and access difficulties. Remote sensing can help to overcome these difficulties, however existing sensors are mainly sensitive to near-surface properties, limiting unable to information on some key parameters. A recently-developed low-frequency ultrawideband microwave radiometer technique is able to penetrate the ice sheet to the bedrock and to measure sea ice properties. This methodology uses a portion of the spectrum that is allocated for other services to collect brightness temperature measurements because this portion of spectrum is seldom used in polar regions, In 2016, the first radiometer operating with this technique, the Ultra-Wideband Software-Defined Microwave Radiometer (UWBRAD) developed at The Ohio State University, was deployed in Northern Canada and in Greenland. In 2020, the Italian Space Agency funded the development of a European radiometer aimed at supporting the ESA Earth Explorer 12 CryoRad mission proposal. This instrument, called the Low-frequency Microwave Radiometer (LoMiRad), was deployed for the first time in 2025 in an airborne campaign over Baffin Bay. Both radiometers sample the operating bandwidth at ~ 100 kHz resolution in order to detect and filter RFI and to produce brightness temperature measurements of the natural background.

The August 2025 LoMiRad campaign follows a similar flight path to the Ultra-Wideband Software-Defined Microwave Radiometer (UWBRAD) missions over Greenland in 2016 and 2017, resulting in overlapping geographic coverage. Both instruments operate across comparable frequency ranges (LoMiRad: 400–2000 MHz; UWBRAD: 500–2000 MHz), enabling direct comparison of the radio frequency interference (RFI) encountered. Moreover, both instruments use the same antenna design and implementation, making the measurements highly similar. The comparison between UWBRAD and LoMiRad datasets is expected to expand understanding of the RFI environment over northern Canada and provide insight into its temporal consistency, supporting future mitigation of RFI effects on radiometer measurements inside and outside protected bands.