In 1979, astronomer W. T. “Woody” Sullivan worked with two undergraduates at the University of Washington to publish a now-classic paper entitled “Eavesdropping: The Radio Signature of Earth.” Sullivan et al. found that the brightest continuous signals emanating from earth came from military radar systems designed to detect ballistic missiles and track satellites in earth orbit, followed by carrier waves used in conventional television broadcasting. The researchers concluded that since 1957, when significant military radar systems began going online, “the earth has indeed become a very bright planet, in fact easily outshining the sun in certain narrow frequency ranges.”
From its inception in the 1960s to its closure in 2013, earth’s most powerful radio source was a 216.983MHz signal emanating 768kW from Lake Kickapoo, Texas. Colloquially known as “the Fence” or the “Space Fence”, the Lake Kickapoo transmitter was used to track satellites overflying the continental United States as part of the military’s space surveillance network.
If human eyes could “see” radio waves in the VHF part of the spectrum, the Fence would appear as an impossibly bright sheet emanating from the southern United States and reaching far into space. I wanted to “see” the Fence, so I created a jury-rigged radio telescope from antennas, preamps, filters, a/d converters, and a software-defined radio. This image is the result of my effort to make an image of this strange piece of infrastructure.
Although the Fence was shut down in 2013, it is being replaced with a new transmitter based at Kwajalein Atoll scheduled to go online in the early 2020s.
I wrote about the Space Fence in an essay about Vertical Geographies.