GPS signal strength at Earth's surface is -130dBmW, so that'd be attowatts... A GPS satellite capable of 0dBmW would be truly scary; it'd have about a petawatt

GPS signal strength at Earth's surface is -130dBmW, so that'd be attowatts... A GPS satellite capable of 0dBmW would be truly scary; it'd have about a petawatt of electrical supply. See, e.g., http://gpsinformation.net/main/gpspower.htm http://gpsinformation.net/main/gpspower.htm