Attachment Radiation Hazard

This document pretains to SES-STA-20060911-01699 for Special Temporal Authority on a Satellite Earth Station filing.

IBFS_SESSTA2006091101699_528064

Exhibit A Radiation Hazard Report Page 1 of 4 Analysis of Non-Ionizing Radiation for a 3.7-Meter Earth Station System This report analyzes the non-ionizing radiation levels for a 3.7-meter earth station system. The analysis and calculations performed in this report comply with the methods described in the FCC Office of Engineering and Technology Bulletin, No. 65 first published in 1985 and revised in 1997 in Edition 97-01. The radiation safety limits used in the analysis are in conformance with the FCC R&O 96-326. Bulletin No. 65 and the FCC R&O specifies that there are two separate tiers of exposure limits that are dependant on the situation in which the exposure takes place and/or the status of the individuals who are subject to the exposure. The Maximum Permissible Exposure (MPE) limits for persons in a General Population/Uncontrolled environment are shown in Table 1. The General Population/Uncontrolled MPE is a function of transmit frequency and is for an exposure period of thirty minutes or less. The MPE limits for persons in an Occupational/Controlled environment are shown in Table 2. The Occupational MPE is a function of transmit frequency and is for an exposure period of six minutes or less. The purpose of the analysis described in this report is to determine the power flux density levels of the earth station in the far-field, near-field, transition region, between the subreflector or feed and main reflector surface, at the main reflector surface, and between the antenna edge and the ground and to compare these levels to the specified MPEs. Table 1. Limits for General Population/Uncontrolled Exposure (MPE) Frequency Range (MHz) Power Density (mW/cm2) 30-300 0.2 300-1500 Frequency (MHz)*(0.8/1200) 1500-100,000 1.0 Table 2. Limits for Occupational/Controlled Exposure (MPE) Frequency Range (MHz) Power Density (mW/cm2) 30-300 1.0 300-1500 Frequency (MHz)*(4.0/1200) 1500-100,000 5.0 Table 3. Formulas and Parameters Used for Determining Power Flux Densities Parameter Symbol Formula Value Units Antenna Diameter D Input 3.7 m Antenna Surface Area Asurface π D2 / 4 10.75 m2 Subreflector Diameter Dsr Input 48.3 cm Area of Subreflector Asr π Dsr 2/4 1832.25 cm2 Frequency F Input 29872 MHz Wavelength λ 300 / F 0.010043 m Transmit Power P Input 5.01 W Antenna Gain (dBi) Ges Input 60.0 dBi Antenna Gain (factor) G 10Ges/10 1000000.0 n/a Pi π Constant 3.1415927 n/a Antenna Efficiency η Gλ2/(π2D2) 0.75 n/a

Exhibit A Radiation Hazard Report Page 2 of 4 1. Far Field Distance Calculation The distance to the beginning of the far field can be determined from the following equation: Distance to the Far Field Region Rff = 0.60 D2 / λ (1) = 817.9 m The maximum main beam power density in the far field can be determined from the following equation: On-Axis Power Density in the Far Field Sff = G P / (4 π Rff 2) (2) = 0.596 W/m2 = 0.060 mW/cm2 2. Near Field Calculation Power flux density is considered to be at a maximum value throughout the entire length of the defined Near Field region. The region is contained within a cylindrical volume having the same diameter as the antenna. Past the boundary of the Near Field region, the power density from the antenna decreases linearly with respect to increasing distance. The distance to the end of the Near Field can be determined from the following equation: Extent of the Near Field Rnf = D2 / (4 λ) (3) = 340.8 m The maximum power density in the Near Field can be determined from the following equation: Near Field Power Density Snf = 16.0 η P / (π D2) (4) = 1.392 W/m2 = 0.139 mW/cm2 3. Transition Region Calculation The Transition region is located between the Near and Far Field regions. The power density begins to decrease linearly with increasing distance in the Transition region. While the power density decreases inversely with distance in the Transition region, the power density decreases inversely with the square of the distance in the Far Field region. The maximum power density in the Transition region will not exceed that calculated for the Near Field region. The power density calculated in Section 1 is the highest power density the antenna can produce in any of the regions away from the antenna. The power density at a distance Rt can be determined from the following equation: Transition Region Power Density St = Snf Rnf / Rt (5) = 0.139 mW/cm2

Exhibit A Radiation Hazard Report Page 3 of 4 4. Region between the Main Reflector and the Subreflector Transmissions from the feed assembly are directed toward the subreflector surface, and are reflected back toward the main reflector. The most common feed assemblies are waveguide flanges, horns or subreflectors. The energy between the subreflector and the reflector surfaces can be calculated by determining the power density at the subreflector surface. This can be determined from the following equation: Power Density at the Subreflector Ssr = 4000 P / Asr (6) = 10.942 mW/cm2 5. Main Reflector Region The power density in the main reflector is determined in the same manner as the power density at the subreflector. The area is now the area of the main reflector aperture and can be determined from the following equation: Power Density at the Main Reflector Surface Ssurface = 4 P / Asurface (7) = 1.865 W/m2 = 0.186 mW/cm2 6. Region between the Main Reflector and the Ground Assuming uniform illumination of the reflector surface, the power density between the antenna and the ground can be determined from the following equation: Power Density between Reflector and Ground Sg = P / Asurface (8) = 0.466 W/m2 = 0.047 mW/cm2

Exhibit A Radiation Hazard Report Page 4 of 4 7. Summary of Calculations Table 4. Summary of Expected Radiation levels for Uncontrolled Environment Calculated Maximum Radiation Power Density Level Region (mW/cm2) Hazard Assessment 1. Far Field (Rff = 817.9 m) Sff 0.060 Satisfies FCC MPE 2. Near Field (Rnf = 340.8 m) Snf 0.139 Satisfies FCC MPE 3. Transition Region (Rnf < Rt < Rff) St 0.139 Satisfies FCC MPE 4. Between Main Reflector and Ssr 10.942 Potential Hazard Subreflector 5. Main Reflector Ssurface 0.186 Satisfies FCC MPE 6. Between Main Reflector and Ground Sg 0.047 Satisfies FCC MPE Table 5. Summary of Expected Radiation levels for Controlled Environment Calculated Maximum Radiation Power Density Region Level (mW/cm2) Hazard Assessment 1. Far Field (Rff = 817.9 m) Sff 0.060 Satisfies FCC MPE 2. Near Field (Rnf = 340.8 m) Snf 0.139 Satisfies FCC MPE 3. Transition Region (Rnf < Rt < Rff) St 0.139 Satisfies FCC MPE 4. Between Main Reflector and Ssr 10.942 Potential Hazard Subreflector 5. Main Reflector Ssurface 0.186 Satisfies FCC MPE 6. Between Main Reflector and Ground Sg 0.047 Satisfies FCC MPE It is the applicant's responsibility to ensure that the public and operational personnel are not exposed to harmful levels of radiation. 8. Conclusions Based on the above analysis it is concluded that harmful levels of radiation will not exist in regions normally occupied by the public or the earth station's operating personnel. The transmitter will be turned off during antenna maintenance so that the FCC MPE of 5.0 mW/cm2 will be complied with for those regions with close proximity to the reflector that exceed acceptable levels.


Document Created: 2006-06-21 17:03:07
Document Modified: 2006-06-21 17:03:07
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