It is constrained using scintillation by the origin of a fast radio burst

The Canadian Institute for Advanced Research, National Science Foundation and the Ministry of Research and Innovation have partnered to build and operate a radio astronomy heritage site and baseband system CHIME/FRB. The CHIME/FRB is funded by a grant from the CFI 2015 Innovation Fund, contributions from the Provinces of British Columbia and Québec, and by the Institute for Astronomy and Astrophysics at the University of Toronto.