reflecting satellite system, concern is warranted about the higher power (particularly at and near the earth's surface) uplink, as well. a. Atmospheric and Ionospheric Effects 2 2 The estimated 325 mW/in (50 mW/cm ) of downlink radiation at about 3.3 GHz may result in non-negligible heating of the ionosphere (Ref. A4, El). This power density level is understood to be at about the threshold for the ionospheric modification and although localized to the region in the beam, may gradually affect a wide region of the ionosphere over time. Such interactions of the beam with the plasma in the D, E and F layers of the ionosphere are also recognized as potential concerns for long-range communications and radar users of the ionosphere (Ref. El), and also could affect the ozone layer's density with the well-articulated risks of increased ultraviolet transmission. Some concern has also been indicated about the possible long-term effects of the high radiation intensity 2 2 (greater than 14,000 mW/in (2170 mW/cm )) near the satelite on exospheric plasmas (Ref. All). However, lack of information implies little assurance is possible in any of these considerations at present. Interactions of the microwave beam with the atmosphere will result in some heating and therefore some risk of affecting weather patterns. Again, however, understanding of this potential problem appears to be minimal. Possible diffraction of the beam by the ionosphere and/or atmosphere resulting from the electron excitations caused by the beam is believed to be negligible (Ref. El). Thus, hazards on the ground resulting from beam misdirection or defocussing from this cause can be ignored. b. Biological Effects The principal concern with the microwave beam is its potential direct effects on humans and biota in the ground area and airspace near the receiving facility. Considerable controversy begins, however, with the fundamental standard that should be maintained for the allowable radiation 2 power density (Refs. A2, A4, A5). A United States standard of 65 mW/in 2 (10 mW/cm ) has been established on the basis of tissue heating potential. 2 2 A much more stringent U.S.S.R. standard of 0.065 mW/in (0.01 mW/cm ) takes
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