Double Type III radio burst observed by, from left to right, PSP/Fields, STEREO A/Waves, Wind/Waves, Solar Orbiter/RPW, and MEX/MARSIS on 4 December 2021. MEX/MARSIS only observed the earlier burst due to the narrow window of operation of MARSIS. Because of this limitation, only the earlier burst was considered for this study. The front of the burst in question was obtained by fitting an inverse polynomial function to manually extracted data (red line). Due to the frequency range limitations of MARSIS, the extracted fit for the Bayesian multilateration was kept at a conservative 0.5–3 MHz (white segment).