The author mentions http://www.projectrho.com/public_html/rocket/spacewardetect...., which has a link to this from 1998: https://groups.google.com/forum/#!topic/rec.arts.sf.science/....

Me, I'm not a physicist and have no idea what I'm talking about, but I do know that if you're looking for a campfire in the desert and the desert is the size of Utah and Nevada, you're going to have a hard time.