During active ionospheric research, the signal generated by the transmitter system is delivered to the antenna array, transmitted in an upward direction, and is partially absorbed, at an altitude between 100 to 350 km (depending on operating frequency), in a small volume a few hundred meters thick and a few tens of kilometers in diameter over the site.
The Final IRI (FIRI) will be the final build of the IRI. It has 180 antenna units, organized in 15 columns by 12 rows, yielding a theoretical maximum gain of 31 dB. A total of 3600 kW (3.6 MW) of transmitter power will feed it.
It is a popular target of conspiracy theories, and though many have expressed fears of the HAARP being used as a nefarious weapon, the scientists involved in aeronomy, space science, or plasma physics reject these fears as unfounded.