Attachment Radiation Hazard Rep

This document pretains to SES-LIC-INTR2019-00217 for License on a Satellite Earth Station filing.

IBFS_SESLICINTR201900217_1616679

Radiation Hazard Analysis Fixed Customer Premises Earth Station Terminal Introduction This analysis calculates the non-ionizing radiation levels for a SpaceX fixed customer premises earth station terminal (“CP terminal”). The calculations performed in this analysis comply with the methods described in FCC Office of Engineering and Technology Bulletin, Number 65 (Edition 97-01) (“Bulletin 65”). This analysis demonstrates that SpaceX CP terminals are compliant and will not result in exposure levels exceeding the applicable radiation hazard limits. Bulletin 65 and Section 1.1310 of the Commission's rules specify two separate tiers of exposure limits: one for Occupational/Controlled Exposures and one for General Population/Uncontrolled Exposures. Limits for Occupational/Controlled Exposures apply in situations where persons are exposed as a consequence of their employment and are fully aware of and can control their exposure. These limits also apply in situations where a person is transient through a location where such limits would otherwise apply provided the person is made aware of the potential for exposure. The limits for General Population/Uncontrolled Exposure apply in situations in which the general public may be exposed, or in which persons that are exposed as a consequence of their employment may not be fully aware of the potential for exposure or cannot exercise control over their exposure. SpaceX will typically deploy its CP terminals in General Population/Uncontrolled Environments. Accordingly, this analysis discusses only the Maximum Permissible Exposure (“MPE”) limit for those types of exposures, which for the Ku-band frequencies used by these CP terminals is a power density equal to 1 mW/cm2 averaged over a thirty-minute period. 1 As described in the definitional section below, this report analyzes the maximum power density levels in the vicinity of a CP terminal antenna in three regions: (1) the far field, (2) the near field, and (3) near the main reflector surface. These radiation regions were analyzed using the definitions and formulas in Bulletin 65 for aperture antennas. Note that the SpaceX CP terminal is a flat phased array, such that the other region normally included in analyses for parabolic dishes (i.e., between the main reflector and the feed) is not applicable in this case. 2 The results of this analysis are summarized in Table 1, which identifies the potential exposure under worst-case operating conditions. CP Terminal Description The CP terminal transmits bursts of information at designated times that are assigned to the terminal by the network. The duty cycle of the uplink transmissions is controlled by the network and independently monitored by the software controlling the CP terminal; this ensures that the transmit duty cycle of a terminal cannot exceed 11% under any circumstances. 1 See 47 C.F.R. § 1.1310(e). 2 Bulletin 65 also calls for consideration of the transition region between near field and far field. However, the power density in the transition region will be less than the maximum power density in the near field and more than the minimum power density in the far field for the purpose of evaluating potential exposure. Accordingly, if the analysis demonstrates compliance for both the near field and far field, it necessarily demonstrates compliance for the transition region. 1

The CP terminal is a flat phased array capable of steering its beams to track NGSO satellites passing within its field of view. As the terminal steers the transmitting beam, it also adjusts the power to maintain a constant level at the receiving antenna of its target satellite, compensating for variations in antenna gain and path loss associated with the steering angle. At the phased array’s equivalent of an “antenna flange,” the highest transmit power (4.06 W) occurs at maximum slant, while the lowest transmit power (0.76 W) occurs at boresight. There is no difference in transmit power between CP terminals at the center or edge of the spot or between clear sky or heavy rain conditions. Explanation of the Analysis The “Calculated Values” in Table 1 are the exposure rates calculated using the formulae from Bulletin 65 for a system with continuous (100% transmit duty cycle) transmission. SpaceX terminals, however, transmit only short bursts of data periodically as instructed by the network and are neither designed for nor capable of continuous transmission. Therefore, in order to compute the effective radiated energy of a SpaceX CP terminal, the terminal’s maximum possible transmitter duty cycle has been used to adjust the values calculated using the Bulletin 65 methodology. Accordingly, the calculated figures reflect the total potential for human exposure based on the length of time that the CP terminal transmits energy during a rolling thirty-minute period. Results of Analysis This analysis demonstrates that the SpaceX CP terminal is not a radiation hazard because the terminal does not exceed the MPE limit of 1 mW/cm2 averaged over a thirty-minute period. Conclusion This radiation hazard analysis demonstrates that SpaceX CP terminals will not result in exposure levels exceeding the applicable MPE limits. 2

Definitions 1) Far Field Region The far field region extends outward from the antenna surface, beginning at a distance of 0.6𝐷𝐷 2 meters where the D is the diameter of the antenna. The maximum power density is calculated πœ†πœ† using the equation recommended in Bulletin 65. 2) Near Field Region The near field region is a volume co-incident with the direction of the main beam extending 𝐷𝐷 2 outward from the antenna surface the length of the near field 4πœ†πœ† meters. 3) Transition Region The transition region is located between the near field region and the far field region. This region has a power density that decreases with increasing distance. Therefore, the power density in the transition region will be less than the maximum power density in the near field and more than the maximum power density in the far field for the purpose of evaluating potential exposure. 4) Region Near the Antenna Surface The power density near the antenna surface can be estimated as equal to four times the power divided by the area of the main reflector surface (phased array illumination is uniform). 3

TABLE 1: RADIATION FROM SPACEX FIXED CP TERMINAL Input Parameters Antenna Diameter D = 0.48 m Frequency f = 14.5 GHz Power into antenna w/ beam at boresight Pmin = 0.76 W Power into antenna w/ beam at slant Pmax = 4.06 W Aperture efficiency [%] η = 56.7% Cosine loss w/ beam at slant loss = 0.551 Maximum Transmit Duty Cycle DTx = 11 % Calculated Values 𝑐𝑐 Wavelength πœ†πœ† = = 0.0207 π‘šπ‘š 𝑓𝑓 πœ‹πœ‹π·π·2 Area of Reflector 𝐴𝐴 = = 0.181 π‘šπ‘š2 4 πœ‚πœ‚4πœ‹πœ‹πœ‹πœ‹ Antenna Gain w/ beam at boresight πΊπΊπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š = = 3012.0 πœ†πœ†2 10 log(πΊπΊπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š ) = 34.79 𝑑𝑑𝑑𝑑 πœ‚πœ‚4πœ‹πœ‹πœ‹πœ‹ Antenna Gain w/ beam at slant πΊπΊπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š = 𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙 = 1658.6 πœ†πœ†2 10 log(πΊπΊπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š ) = 32.20 𝑑𝑑𝑑𝑑 𝐷𝐷2 Length of Near Field 𝑅𝑅𝑛𝑛𝑛𝑛 = = 2.78 π‘šπ‘š 4πœ†πœ† 𝐷𝐷2 Beginning of Far Field 𝑅𝑅𝑓𝑓𝑓𝑓 = 0.6 = 6.68 π‘šπ‘š πœ†πœ† Power Density Calculations with Beam at Boresight π‘ƒπ‘ƒπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š πΊπΊπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š π‘šπ‘šπ‘šπ‘š Power Density in Far Field 𝑆𝑆𝑓𝑓𝑓𝑓 = 𝐷𝐷𝐷𝐷𝐷𝐷 2 = 0.04 4πœ‹πœ‹π‘…π‘…π‘“π‘“π‘“π‘“ 𝑐𝑐𝑐𝑐2 4πœ‚πœ‚πœ‚πœ‚π‘šπ‘šπ‘šπ‘šπ‘šπ‘š π‘šπ‘šπ‘šπ‘š Power Density in Near Field 𝑆𝑆𝑛𝑛𝑛𝑛 = 𝐷𝐷𝐷𝐷𝐷𝐷 = 0.10 𝐴𝐴 𝑐𝑐𝑐𝑐2 4π‘ƒπ‘ƒπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š π‘šπ‘šπ‘šπ‘š Power Density at Antenna Surface π‘†π‘†π‘Ÿπ‘Ÿπ‘Ÿπ‘Ÿπ‘Ÿπ‘Ÿ = 𝐷𝐷𝐷𝐷𝐷𝐷 = 0.18 𝐴𝐴 𝑐𝑐𝑐𝑐2 4

Power Density Calculations with Beam at Slant π‘ƒπ‘ƒπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š πΊπΊπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š π‘šπ‘šπ‘šπ‘š Power Density in Far Field 𝑆𝑆𝑓𝑓𝑓𝑓 = 𝐷𝐷𝐷𝐷𝐷𝐷 2 = 0.13 4πœ‹πœ‹π‘…π‘…π‘“π‘“π‘“π‘“ 𝑐𝑐𝑐𝑐2 4πœ‚πœ‚πœ‚πœ‚π‘šπ‘šπ‘šπ‘šπ‘šπ‘š π‘šπ‘šπ‘šπ‘š Power Density in Near Field 𝑆𝑆𝑛𝑛𝑛𝑛 = 𝐷𝐷𝐷𝐷𝐷𝐷 = 0.56 𝐴𝐴 𝑐𝑐𝑐𝑐2 4π‘ƒπ‘ƒπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š π‘šπ‘šπ‘šπ‘š Power Density at Antenna Surface π‘†π‘†π‘Ÿπ‘Ÿπ‘Ÿπ‘Ÿπ‘Ÿπ‘Ÿ = 𝐷𝐷𝐷𝐷𝐷𝐷 = 0.99 𝐴𝐴 𝑐𝑐𝑐𝑐2 5


Document Created: 2019-02-01 15:05:50
Document Modified: 2019-02-01 15:05:50
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