Description / Abstract: This document supersedes DO-235A. It departs from the previous assessment reports by characterizing the “external” (non-aeronautical) Radio Frequency Interference (RFI) as an aggregate effect. Terrestrial RFI sources are modeled as being distributed to the radio horizon for the Global Navigation Satellite System (GNSS) aircraft antenna. On-board non-aeronautical RFI is also characterized as an aggregate effect from multiple sources distributed throughout the passenger cabin. Explicit location-dependent GNSS inter- and intra-system RFI power spectral density values are computed based on “critical-satellite” configurations for a 30-satellite GPS constellation. RFI components for new Space Based Augmentation System (SBAS), Quasi-Zenith Satellite System (QZSS) and Galileo satellite constellations are also determined. Receiver MOPS RFI test condition modifications are proposed to better address the composite aeronautical and non-aeronautical RFI environment for certain flight phases and operations. New potential RFI sources (Mobile Satellite Service ancillary terrestrial component terminals, GPS re-radiators) are discussed. Other potential RFI sources are reviewed and a set of RFI mitigations discussed.