Encountering an Alien, extraterrestrial interstellar species would indeed be an extraordinary, monumental, and transformative historical event in human history. Speculation of such an encounter encompasses short and long-term surmised scenarios, especially the implications for science, military preparedness, planetary security, and national sovereignty. There are invariably technological, and communication-linguistic challenges as well as societal and religious aftermath consequences.
The encounter was perhaps predicted to occur through signal detection via advanced Radio Telescopes or by direct visitation to Earth by an Alien, extraterrestrial species, or interdimensional travel. What's more, the "First Contact" circumstance would hypothetically range from a peaceful encounter to accidental confrontation (due to misinterpretation or misunderstanding) or even to a deliberate encounter (possibly an outright aggressive, hostile interaction, provoked, or unprovoked).
The tranquil night was accentuated by the indigenous coqui frog's serenade, whose sound punctuated the air surrounding the Arecibo Observatory, the World's largest (1000 meter diameter) Radio Telescope nestled in the northwest corner area of Puerto Rico. On November 16, 1974, the Radio Telescope had whispered a siren song cryptically into the cosmos, transmitting Radio signals that danced across the cosmic expanse. Little did humanity realize those signals would later beckon visitors as a directional beacon from beyond the stars. It was an ordinary Sunday evening at the Observatory until the monitoring systems detected an anomaly - a signature unlike any cosmic, Earth-based, or satellite noise hitherto ever recorded. The readings displayed a peculiar inflection tracing originating from a distant corner of the galaxy, the Globular star cluster Messier 13 (M13) Hercules constellation. The transmission partly matched the complex pattern of signals the project sent from Arecibo over three decades earlier to the very same constellation. The signal received was a message sent back from a dark void of the universe... It wasn't an echo or background terrestrial or satellite noise. The message had been (intentionally) modified!
"Hay un mensaje..."
The message forecast the actual UFO/UAP arrival and eventual downing by the US Military, sending the Alien, extraterrestrial craft, and fuselage debris toward El Yunque Tropical Rain Forest. The Alien, extraterrestrial craft site investigation, retrieval, and the finding of a non-biologic entity (NBE) would lead to an Autopsy.
The EPILOGUE of this work, importantly, provides a history of the Search for Extraterrestrial Intelligence (SETI) project and lists the key accomplishments of the SETI Arecibo Radio Telescope Observatory.