Attachment TT&C Rad Haz

This document pretains to SES-LIC-INTR2019-00966 for License on a Satellite Earth Station filing.

IBFS_SESLICINTR201900966_1643353

Radiation Hazard Analysis TT&C Earth Station Introduction This analysis calculates the non-ionizing radiation levels for a SpaceX Services, Inc. (“SpaceX Services”) earth station that will perform telemetry, tracking, and command functions for SpaceX’s non-geostationary orbit satellite system (“TT&C 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 Services TT&C terminal is generally compliant and will not result in exposure levels exceeding the applicable radiation hazard limits, and any radiation hazard that may exist will be mitigated by limited access and various protocols to ensure safe exposure levels. 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 Services will deploy its TT&C terminal in an Occupational/Controlled Exposures Environment. Accordingly, this analysis discusses only the Maximum Permissible Exposure (“MPE”) limit for those types of exposures, which for the Ku-band frequencies used by this TT&C terminal is a power density equal to 5 mW/cm2 averaged over a six-minute period. 1 As described in the definitional section below, this report analyzes the maximum power density levels in the vicinity of a TT&C terminal antenna in four regions: (1) the far field, (2) the near field, (3) near the main reflector surface, and (4) between the main reflector and the feed mouth. These radiation regions were analyzed using the definitions and formulas in Bulletin 65 for aperture antennas. The results of this analysis are summarized in Table 1, which identifies the potential exposure under worst-case operating conditions. TT&C Terminal Description The TT&C terminal is a five-meter parabolic dish capable of steering its beams to track NGSO satellites passing within its field of view. At the antenna flange, the maximum transmit power is 38.9W. Although unlikely in practice, for purposes of this analysis we have conservatively assumed that the TT&C terminal can transmit at 100% duty cycle. 1 See 47 C.F.R. § 1.1310(e). 1

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. Results of Analysis This analysis demonstrates that the SpaceX Services TT&C terminal is not a radiation hazard because the terminal does not generally exceed the MPE limit of 5 mW/cm2 averaged over a six- minute period. This TT&C terminal will be located in an area clearly marked with Radiation Hazard signage with no access by the general public. Only around the feed mouth are the relevant radiation levels exceeded. This measurement is taken at a point between the feed and the sub- reflector. Power to the transmitters will be turned off remotely whenever work needs to be performed in this region. Signage will mark the area for Radiation Hazard and access by qualified personnel only, ensuring awareness and enhancing safety. Consequently, there is no risk of radiation exposure beyond the acceptable limits. Conclusion This radiation hazard analysis demonstrates that the SpaceX Services TT&C terminal will not result in unacceptable radiation exposure levels. . 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 (main reflector illumination is uniform). 5) Region between the Main Reflector and the Feed The power radiated from the feed toward the reflector is conical in shape with the vertex at the feed. The maximum power is at the feed mouth and can be estimated as four times the transmit power divided by the area of the feed mouth. 3

TABLE 1: RADIATION FROM SPACEX SERVICES FIXED TT&C EARTH STATION Input Parameters Antenna Diameter D=5m Frequency f = 14 GHz Diameter of Feed Mouth Dfeed = 12 cm Max Power into Antenna Pmax = 15.9dBW Aperture efficiency [%] η = 59% Maximum Transmit Duty Cycle DTx = 100 % Calculated Values 𝑐𝑐 Wavelength πœ†πœ† = = 0.0214 π‘šπ‘š 𝑓𝑓 πœ‹πœ‹π·π·2 Area of Reflector 𝐴𝐴 = = 19.63 π‘šπ‘š2 4 2 πœ‹πœ‹π·π·π‘“π‘“π‘“π‘“π‘“π‘“π‘“π‘“ Area of Feed Mouth 𝐴𝐴𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 = = 0.0113 π‘šπ‘š2 4 πœ‚πœ‚4πœ‹πœ‹πœ‹πœ‹ Antenna Gain πΊπΊπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š = = 316,496.3 πœ†πœ†2 10 log(πΊπΊπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š ) = 55.0 𝑑𝑑𝑑𝑑𝑑𝑑 𝐷𝐷2 Length of Near Field 𝑅𝑅𝑛𝑛𝑛𝑛 = = 291.67 π‘šπ‘š 4πœ†πœ† 𝐷𝐷2 Beginning of Far Field 𝑅𝑅𝑓𝑓𝑓𝑓 = 0.6 = 700.00 π‘šπ‘š πœ†πœ† Power Density Calculations Power Density in Far Field π‘ƒπ‘ƒπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š πΊπΊπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š π‘šπ‘šπ‘šπ‘š 𝑆𝑆𝑓𝑓𝑓𝑓 = 𝐷𝐷𝐷𝐷𝐷𝐷 2 = 0.20 4πœ‹πœ‹π‘…π‘…π‘“π‘“π‘“π‘“ 𝑐𝑐𝑐𝑐2 Power Density in Near Field 4πœ‚πœ‚πœ‚πœ‚π‘šπ‘šπ‘šπ‘šπ‘šπ‘š π‘šπ‘šπ‘šπ‘š 𝑆𝑆𝑛𝑛𝑛𝑛 = 𝐷𝐷𝐷𝐷𝐷𝐷 = 0.47 𝐴𝐴 𝑐𝑐𝑐𝑐2 4π‘ƒπ‘ƒπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š π‘šπ‘šπ‘šπ‘š Power Density at Antenna Surface (Main Reflector) π‘†π‘†π‘Ÿπ‘Ÿπ‘Ÿπ‘Ÿπ‘Ÿπ‘Ÿ = 𝐷𝐷𝐷𝐷𝐷𝐷 = 0.79 𝐴𝐴 𝑐𝑐𝑐𝑐2 4π‘ƒπ‘ƒπ‘šπ‘šπ‘šπ‘šπ‘šπ‘š π‘šπ‘šπ‘šπ‘š Power Density at Feed Mouth 𝑆𝑆𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 = 𝐷𝐷𝐷𝐷𝐷𝐷 = 1375.97 𝐴𝐴𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 𝑐𝑐𝑐𝑐2 4


Document Created: 2019-04-20 00:29:41
Document Modified: 2019-04-20 00:29:41
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