Avoiding Contamination of Vertical Temperature Profiles and Total Cloud Water Measured by Microwave Radiometers

Microwave-based passive sensed data from space are important inputs to the numerical weather prediction models. Contamination of radiometer data is possible from adjacent band signal sources, which could adversely impact these critical measurements. Recent Notices of Proposed Rulemaking (NPRMs) involve planned and operational constellations with thousands of satellites transmitting from Low Earth Orbit (LEO). Due to the unprecedented number of new and planned satellites, it is critical to understand all system-level parameters associated with the number of emission sources, antenna characteristics and each transmitter’s out-of-band signal characteristics that may impact that system’s compatibility with EESS operation in bands adjacent to these new systems. An important band segment for EESS is the 50 – 55.5 GHz region that is utilized by passive microwave radiometers for atmospheric temperature sounding. Global atmospheric temperature profiles are the measurements of highest importance, on a per observation basis, for the operation of Numerical Weather Prediction (NWP) models. Accordingly, it is of critical importance for the future of NWP, that these measurements remain uncontaminated by anthropogenic emissions. Guidelines for acceptably low levels of contamination in EESS bands are stated by the International Telecommunications Union – Radio Communication Sector (ITU-R) RS-2017 recommendation. Using RS-2017 as a baseline, we examine the potential impact of proposed systems and their OOBE levels on EESS measurements in the 50 – 55.5 GHz spectral region and the role of possible guard bands to help separate adjacent band radio emissions from the receiver passbands of EESS instruments.