Thanks for this information. I’m the one who alluded to GPS technology: technically, the article did not.
Would there be NO type of transponder of that size detectable by satellite (for example, I thought RFID devices were very small and inexpensive)? That is, does the device literally have to “transmit” a signal as opposed to having some form of unique “signature” detectable by satellite?
Put another way, if a satellite can detect something as small as neutrinos http://www.isv.uu.se/thep/talks/os/060505-SNOW.pdf why can’t it detect something on the ground that’s emitting an admittedly feeble signal? Sorry if this is an absurdly naive question. I’m not a technical person, so don’t waste time on a technical explanation. Your say-so “can’t be done” is fine by me. I’m just curious.
RFID chips work over a distance of just a few feet. Satellites are hundreds of miles away, and the power goes up as the cube of the distance. From a few feet to a few hundred miles would take a hundred million trillion (10^17) times as much power. We're talking Obama deficit sized numbers here.