Ionospheric Research Instrument Directory References Discover 12 Greek Gods and Goddesses 26 Decade-Defining Events in U.S. History How Many Electoral College Votes Does Each U.S. State Have? 7 of History's Most Notorious Serial Killers Is Australia an Island? 10 Famous Artworks by Leonardo da Vinci History of Technology Timeline Ionospheric Research Instrument instrument Ask the Chatbot a Question Also known as: IRI Learn about this topic in these articles:HAARP In HAARPThe main instrument is the Ionospheric Research Instrument (IRI), an array of 180 radio antennas spread over an area of 0.13 square kilometer (33 acres).Read More