The thing that’s crazy about Arecibo is that it’s not just a telescope — it’s also a very high power transmitter, so they’re doing astronomy with RADAR. I didn’t know such a thing was even possible until this week.
"the round trip light time to objects beyond Saturn is longer than the time the telescope can track it, preventing radar observations of more distant objects."
"The Arecibo message is a 1974 interstellar radio message carrying basic information about humanity and Earth sent to globular star cluster M13. It was meant as a demonstration of human technological achievement, rather than a real attempt to enter into a conversation with extraterrestrials."
"The message consisted of 1,679 binary digits, approximately 210 bytes, transmitted at a frequency of 2,380 MHz and modulated by shifting the frequency by 10 Hz, with a power of 450 kW. The "ones" and "zeros" were transmitted by frequency shifting at the rate of 10 bits per second. The total broadcast was less than three minutes."
