Polar patch considered in this case study as seen in the RISR FoV. RISR beam positions and measured densities at 300 km are shown, as well as the tracks from 18:00 to 19:00 (grey line) and positions at 18:46 (thick “x”) of the IPPs from the four conjunctions considered in this study. Both the CHAIN and CERTO receivers are located in Resolute Bay, but CHAIN detects signals transmitted by various GPS satellites while CERTO detects that from the CASSIOPE beacon. Included are CHAIN-GPS G10 (green), CHAIN-GPS G15 (purple), CHAIN-GPS G18 (orange), and CERTO-CASSIOPE (pink). An animation of the entire period the patch was observed is available in the Supplementary materials.