Phases of Completion of the IRI

The Ionospheric Research Instrument (IRI) is the primary tool that will be used to study ionospheric physics in the HAARP program. The IRI will be used to induce a small, localized change in ionospheric temperature so that resulting physical reactions can be studied by other instruments located either at or close to the HAARP site.

An Environmental Impact analysis was completed prior to beginning construction of the IRI. The Record of Decision that resulted from this process permits the construction of an antenna array with a maximum size of 180 antenna elements, arranged in 15 columns by 12 rows. This final array will not be completed for several years. Instead, the IRI will be completed in smaller phases beginning with the Developmental Prototype (DP) and continuing with the filled DP (FDP), the Limited IRI (LIRI) and ending with the full size or final IRI (FIRI).

The following table compares all of the IRI phases with each other for several of the major electrical characteristics (An HTML 2.0 version is also available):

Comparison of IRI Phases
Number of Active Antenna Elements18 48108 180
Total Transmitter Power (kW)360 9602160 3600
Maximum Antenna Gain (dB)19 2429 31
Max Effective Radiated Pwr (dBW)74 8492 96
Min Antenna Pattern Width (degrees) 985
Frequency Range2.8 to 10 MHz
Modulation TypesCW/AM/FM/PM

Note: The maximum antenna gain and ERP and the minimum width in antenna pattern all occur at the highest frequency, 10 MHz.

Also take a look at the Comparison Chart that shows how the various phases of HAARP relate to other high power facilities operating in the High Frequency spectrum.

The degree to which the IRI will be useful as a research tool is also a function of the phase of completion. The DP, for example, is only minimally useful for ionospheric studies. Beginning with the FDP, however, meaningful research will be possible. The LIRI will provide a capability about equivalent to the best existing facility, and the FIRI will reach the final, world class capability envisioned at the program's conception.


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Last updated July 2, 1996.