Eavesdropping: The Radio Signature of the Earth

Abstract

In addition to searches for purposeful signals, those attempting interstellar communication should also consider the possibility of eavesdropping on radio emissions inadvertently "leaking" from other technical civilizations. To understand better the information which might be derivable from radio leakage, the case of planet earth is considered. The most detectable and useful escaping signal arise in a few BMEWS-type radar systems and in normal television broadcasting. A model including over 2000 television transmitters is used to demonstrate the wealth of astronomical and cultural information available from a distant observer's careful monitoring of frequency and intensity variations in individual video carriers (program materials is not taken to be detectable).

Measuring the global 21-cm signal with the MWA-I: improved measurements of the Galactic synchrotron background using lunar occultation

“…Earthshine is known to contaminate the brightness temperature of the Moon (see Sullivan et al 1978;Sullivan & Knowles 1985;McKinley et al 2013;Vedantham et al 2015). Radar studies of the Moon by Evans (1969) find that the reflective properties of the Moon at radio wavelengths depend strongly on both the angle of incidence of the radiation and on wavelength.…”

Choosing a Maximum Drift Rate in a SETI Search: Astrophysical Considerations

“…An exception to this is the review of Oliver & Billingham (1971) which used the drift rate of an Earth-like planet with an 8 hour day, thereby accidentally defining a common literature standard used by some of the searches above. Sullivan et al (1978) considered the Doppler drift of signals leaving the Earth, while Cornet & Stride (2003) pointed out that correlating "anomalous microwave phenomena" observed with telescopes such as the ATA to known drift rates within the solar system could allow for localization of a signal to a particular body. Harp et al (2016) notes that orbital or rotational motion of a transmitter in an exoplanetary system can produce a drift rate, but does not quantify what upper limits on this motion might be.…”

“…In fact,(Sullivan et al 1978), via examination of the Earth's radio signature, even raises the possibility of measuring the presence of a plasmasphere, the jitter from wind tilting the tallest transmitters, the inclination of the earth's axis, and the transmitters' antenna sizes.…”

Do potential SETI signals need to be decontaminated?

“…In what follows it is argued that particular care needs to be taken in the way messages are handled when they are received. A third possibility is that the galaxy may contain artifacts like TV or radar leakage signals [5].…”