Sea interferometry
a form of radio astronomy that uses radio waves reflected off the water
Sea interferometry, also known as sea-cliff interferometry, is a form of radio astronomy that uses radio waves reflected off the sea to produce an interference pattern. It is the radio wave analogue to Lloyd's mirror. The technique was invented and exploited in Australia between 1945 and 1948.
Process
A radio detecting antenna is placed on top of a cliff, which detects radio propagation coming directly from the source and radio waves reflected off the water surface. The two sets of waves are then combined to form an interference pattern such as that produced by two separate aerials. The reflected wavefront travels an additional distance 2h sin(i) before reaching the detector where h and i are the height of the cliff and the inclination (or altitude angle) of the incoming wavefront respectively. It acts as a second aerial twice the height of the cliff below the first.
Sea interferometers are drift instruments, that is, they are fixed and their pointing direction changes with the rotation of the Earth.
The interference patterns for a sea interferometer commence sharply as soon as the source rises above the horizon, instead of fading in gradually as for a normal interferometer. Since it consists of just one detector, there is no need for connecting cables or for preamplifiers.
The public source identifies “Sea interferometry” as a form of radio astronomy that uses radio waves reflected off the water. This brief keeps that definition visible, then builds a research path around interferometry, form and radio.
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Datasets, specimens, observations and peer-reviewed methods provide the appropriate test for the technical claims summarized here. The source revision retrieved here is dated Apr 17, 2024. The linked authority identifier is Q7440068. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1945 and 1948.
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This entry incorporates text from “Sea interferometry” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.