Radio signals transmitted to and bounced back from an object.

RADAR is an acronym for RAdio Detecting And Ranging.

Another tool used by archaeologists to search for archaeological features beneath the topsoil.

Ground penetrating radar or GPR works by sending high-frequency radar pulses from an antenna into the ground.

Buried materials or sediments and changes in the subsoil reflect the radar pulses back up to the antenna, and by measuring the time that has passed between when the pulses were sent and when they were received; an understanding of the changes in soils, sediments, and features can be determined.

The bouncing of radio waves off objects in the solar system, with reception and analysis of the "echoes".

Radar contact with the moon was first made in 1945 and with Venus in 1961. The travel time to radio reflections allows the distances of objects to be determined accurately.

Analysis of the reflected beam reveals the rotation period and allows the object's surface to be mapped. The rotation periods of Venus and Mercury were first determined by radar. Radar maps of Venus were obtained first by earth-based radar and subsequently by orbiting space probes.

1. A dome-shaped protective enclosure for a radar antenna, made from materials that do not interfere with the transmission and reception of radio waves.
2. A blend of radar and dome.

• Radar: The electronic equipment that transmits and receives high-frequency radio waves to detect, locate, and track distant objects; an acronym composed of radio detection and ranging.
• Dome: A hemispherical or convex structure, that slopes in all directions from a central point; especially, a building.