1) An interferometer 2) Interferometer 3) Russian space probe
Found on
https://www.crosswordclues.com/clue/etalon
Soviet passive geodetic satellites; Etalon means `standard.” Each is spherical and covered with 306 antenna arrays, each array containing 14 corer cubes for laser reflection. Etalons were designed and launched to enable the complete characterization of Earth`s gravitational field at the altitude and...
Found on
http://www.daviddarling.info/encyclopedia/E/Etalon.html
an interferometer consisting of two glass plates that reflect approximately half of each ray of light incident upon them and that are separated by a small, fixed distance: used to compare wavelengths and to study atomic spectra.
Found on
https://www.infoplease.com/dictionary/etalon
No exact match found.
