The Arecibo Observatory is a massive radio telescope and transmitter located in the Arecibo municipality in Puerto Rico. It's the largest single aperture radio telescope with a diameter of an amazing 305 meters (1000 feet), and has been enormously useful to science. In 1974, a decade after opening, it was famously used to send the Arecibo Message, a message sent to distant globular star cluster M13 (25,000 light-years away). its purpose was more demonstrative and ceremonial than a genuine contact attempt, as M13 won't be where the message was aimed when it arrives about 25,000 years from now.

And now it's in Powder Toy. Presenting the Arecibo Message & Transmitter!

It uses a simple FILT-based read-only memory device to store the 23x75-pixel message -- accurate to the real message -- that can be transmitted at any time, any number of times. The result is fully visible and mostly legible, output in chunky blocks of photons for the best visibility.