Active SETI
the attempt to send messages to intelligent extraterrestrials
Pioneer plaque
plaque attached to the Pioneer 10 and Pioneer 11 spacecraft in case extraterrestrial life finds them
Arecibo message
1974 message into space
Cosmic Call
interstellar radio messages
Voyager Golden Record
two phonograph records included on both Voyager spaceprobes launched in August and September 1977
The Morse Message
radio message broadcast to Venus in 1962