Sugar Tree is the name of a bistatic radar Over-the-horizon radar built by the US in the 1960s. The key idea in Sugar Tree was a reinvention of Klein Heidelberg Nazi German radar system developed for use in the

Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

. Sugar Tree was a "covert hitchhiker using

Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...

, surface-wave

HF radio High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten ...

broadcast signals and a remote sky-wave receiver to detect Soviet ballistic missile launches". The key idea, in other words, is to receive radar reflexions without oneself transmitting a radar signal by using instead some other signal, typically one that originates from the adversary. Willis, N & Griffiths, H (eds), Advances in Bistatic Radar, SciTech Publishing, Raleigh, NC 2007, cited in Willis & Griffiths " Klein Heidelberg – a WW2 bistatic radar system that was decades ahead of its time". http://www.cdvandt.org/K-H%20final.pdf

References

Radar Passive radars Cold War military radars of the United States Missile defense {{mil-stub