Characterization of Radiometer Radio Frequency Interference (RFI) Caused by Ku-Band Downlinks from Low-Earth Orbit
The drastic increase of Low-Earth Orbit (LEO) micro-satellite (“micro-sat”) constellations in recent years has raised concern in the meteorology and weather remote sensing communities due to the ability of these constellations to contaminate signals in nearby portions of the electromagnetic spectrum dedicated to science and weather observations. This is especially true since the majority of operational LEO satellites have downlinks within the microwave regime and have the potential to contribute significantly to the radio frequency interference (RFI) environment, decreasing the measurement accuracy and creating coverage gaps for weather sensors operating around these bands. For instance, the Advanced Microwave Scanning Radiometer 2 (AMSR2) has a 10.65 GHz band which has observed RFI contamination due to spectral leakage from communications systems. Even low-level RFI can manifest as weak polarization signatures within 3rd and 4th Stokes parameters. RFI sourced from OneWeb and Starlink is difficult to accurately characterize given the intermittent nature of the downlink signal structure, the pseudo-random coding of the message content, the transmitter beam-forming scheme, and the sheer number of on-orbit transmitters. The problem is further confounded by the proprietary nature of the Starlink and OneWeb downlink strategies, which requires that studies of the micro-sats’ beam-forming and signal structure be reverse-engineered by researchers. Several recent studies, many of them passive-radar-focused, have successfully characterized the transmit signals from these mico-sats via a combination of inferences from FCC filings and reverse-engineering based on direct downlink signal data recordings. This work presents a simulation of OneWeb-sourced RFI which couples the aforementioned reverse engineering efforts with electromagnetic scattering and propagation models. Case-studies of RFI simulations, as well as mitigation and compensation strategies, will be discussed in the final presentation based on these simulation results. The propagation of RFI-induced errors into the final wind vector product will also be qualitatively discussed. This work will assist future studies of RFI flagging and mitigation for radiometer-based wind vector retrievals, particularly as the microwave spectrum becomes increasingly congested with high-bandwidth communications waveforms.
IMPACT
Accomplishment: Successfully characterized interference sources for spaceborne satellites; Result: Improved and expedited design process for future weather satellites, saving an estimated $3 million in design/testing costs
PRESENTER
Ouellette, Jeffrey
jeffrey.d.ouellette4.civ@us.navy.mil
202-767-2526US Naval Research Laboratory
CO-AUTHOR(S)
Brant, Tyler
tyler.a.brant.civ@us.navy.milBrand, Lodewijk
lodewijk.w.brand.civ@us.navy.milLong, Christopher
christopher.d.long50.civ@us.navy.milBettenhausen, Michael
michael.h.bettenhausen.ctr@us.navy.milCATEGORY
Weather & Ocean Modeling & Sim
SECONDARY CATEGORY
Comp Electromagnetics & Acoustics
SYSTEM(S) USED
Narwhal