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** PREPUBLICATION COPY – WORDING SUBJECT TO CHANGE ** Agenda Item 1.18: Second Harmonic Emissions into 48005000 MHz Agenda Item 1.18 considers extending the existing primary and secondary radiodetermination‐satellite service (space‐to‐Earth) allocations in the band 2 483.5‐2 500 MHz in order to make a global primary allocation, and to determine the necessary regulatory provisions based upon the results of ITU R studies, in accordance with Resolution 613 (WRC 07). The primary concern for Radio Astronomy is second harmonic emissions into the 4800‐4990 and 4990 to 5000 MHz bands. Nearly all centimeter wavelength radio telescopes operate in the 4800‐5000 MHz band to study the continuum radio emission from stars, galaxies, quasars, gamma‐ray bursts and other sources of galactic and extragalactic thermal and non thermal continuum radiation. If enacted in full, this agenda item could impact radio astronomy in the 4800‐5000 MHz band as a result of second harmonic radiation. So, second harmonic radiation should be kept below the level given in Recommendation ITU‐R RA.769 in the band 4800 MHz to 5000 MHz as addressed in 5.402: The use of the band 2483.5‐2500 MHz by the mobile‐satellite and the radiodetermination‐satellite services is subject to the coordination under No. 9.11A. Administrations are urged to take all practicable steps to prevent harmful interference to the radio astronomy service from emissions in the 2483.5‐2500 MHz band, especially those caused by second‐harmonic radiation that would fall into the 4990‐5000 MHz band allocated to the radio astronomy service worldwide. Recommendation: Second harmonic radiation emissions into the 4800‐5000 MHz band should be kept below the level given in Recommendation ITU‐R RA.769 as addressed in 5.402. 31