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):
|Number of Active Antenna Elements||18||48||108||180|
|Total Transmitter Power (kW)||360||960||2160||3600|
|Maximum Antenna Gain (dB)||19||24||29||31|
|Max Effective Radiated Pwr (dBW)||74||84||92||96|
|Min Antenna Pattern Width (degrees)||9||8||5|
|Frequency Range||2.8 to 10 MHz|
Note: The maximum antenna gain and ERP and the minimum width in antenna pattern all occur at the highest frequency, 10 MHz.
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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