Explorer 49
Date: 10 Jun 1973

Explorer 49 was to be placed into lunar orbit in order to be able to use the Moon as a shield against radio interference from Earth as it listened for radio emissions from the rest of our solar system, the galaxy and beyond.


The spacecraft achieved lunar orbit and was used successfully to study low-frequency radio emissions from sources including the Sun, Jupiter, the galaxy and extra-galactic sources.


With its vast antenna array, Explorer 49 was the largest (in physical dimensions) lunar orbiter of the 20th century.

Credit: NASA