Radiation Hazard S band Fairbanks

0831-EX-PL-2014 Text Documents

BlackSky Global, LLC

2014-12-10ELS_156801

Radiation Hazard Report Exhibit Page 1 of 5 Analysis of Non-Ionizing Radiation for a 9.1-Meter Dish Antenna Earth Station System This report analyzes the non-ionizing radiation levels for a 9.1-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’s General RF Exposure Guidance, 447498 D01 v05r02. The radiation safety limits used in the analysis are in conformance with Title 47 Chapter I, Subchapter A, Part 1, Subpart I, Section 1.1310. Section 1.1310 specifies that there are two separate tiers of exposure limits that are dependent 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, 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) 0.3 - 1.34 100 1.34 - 30 180/Frequency(MHz)^2 30-300 0.2 300-1500 Frequency(MHz)/1500 1500-100,000 1 Table 2. Limits for Occupational/Controlled Exposure (MPE) Frequency Range (MHz) Power Density (mW/cm2) 0.3-3.0 100 3.0-30 900/Frequency(MHz)^2 30-300 1 300-1500 Frequency(MHz)/300 1500-100,000 5

Radiation Hazard Report Exhibit Page 2 of 5 Table 3. Formulas and Parameters Used for Determining Power Flux Densities Parameter Symbo Formula Value Units l Ant Largest Dimension D Input 9.1 m Ant Equiv Surface Area ASurface 𝜋𝜋D2 /4 65.0 m2 Subreflector Diameter d Input 1.38 m Subreflector Surface Area ASub 𝜋𝜋d2 /4 1.50 m2 Frequency F Input 2071.875 MHz Wavelength 𝜆𝜆 300/F 0.145 m Transmit Power P Input 15 W Antenna Gain (dBi) Ges Input 42.6 dBi Antenna Gain (factor) G 10Ges /10 18197 n/a Pi 𝜋𝜋 Constant 3.141592654 n/a Antenna Efficiency 𝜂𝜂 Gλ2 /(4𝜋𝜋)/Asurface 0.467 n/a

Radiation Hazard Report Exhibit Page 3 of 5 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 R ff = 0.60 D2 /𝜆𝜆 (1) = 343.1 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 = GP/(4𝜋𝜋R ff 2 ) (2) = 0.184 W/m2 = 0.0184 mW/cm2 2. Subreflector Calculation The power density Ssub in the subreflector is determined as follows: Subreflector Surface Power Density Ssub = 4P/Asub (3) = 40.1 W/m2 = 4.01 mW/cm2 3. Main Reflector Calculation The power density Ssurface in the main reflector is determined as follows: Main Reflector Surface Power Density Ssurface = 4P/Asurface (3) = 0.923 W/m2 = 0.0923 mW/cm2 4. 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 surface area 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 R nf = D2 /(4𝜆𝜆) (4) = 143.0 m The maximum power density in the Near Field can be determined from the following equation: Near Field Power Density Snf = 4ηP/Asurface (5) = 0.431 W/m2 = 0.0431mW/cm2

Radiation Hazard Report Exhibit Page 4 of 5 5. 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 2 is the highest power density the antenna can produce in any of the regions away from the antenna. The power density at a distance Rtz can be determined from the following equation: Transition Region Power Density Stz = Snf R nf /R tz (6) = 0.0431 mW/cm2 Rtz is calculated at a distance of 143.0 meters from the antenna, which is the worst case; it is the edge of the near-field boundary, Rnf. 6. Region between the Antenna and the Ground Assuming uniform illumination of the antenna surface, the power density between the antenna and the ground can be determined from the following equation: Power Density between Antenna and Ground Sg = P/Asurface (7 ) = 0.231W/m2 = 0.0231 mW/cm2 7. Summary of Calculations Table 4. Summary of Expected Radiation Levels for Uncontrolled Environment Calculated Maximum Radiation Power Region Density Level (mW/cm2 Hazard Assessment Far Field (Rff = 343.1 m) Sff 0.0184 Satisfies FCC MPE Subreflector Surface Ssub 4.01 Exceeds limitations Main Reflector Surface Ssurface 0.0923 Satisfies FCC MPE Near Field (Rnf = 143.0 m) Snf 0.0430 Satisfies FCC MPE Transition Region (Rnf < Rtz < Rff) Stz 0.0430 Satisfies FCC MPE Between Reflector and Ground Sg 0.0231 Satisfies FCC MPE

Radiation Hazard Report Exhibit Page 5 of 5 Table 5. Summary of Expected Radiation Levels for Controlled Environment Calculated Maximum Radiation Power Region Density Level (mW/cm2 Hazard Assessment Far Field (Rff = 343.1 m) Sff 0.0184 Satisfies FCC MPE Subreflector Surface Ssub 4.01 Satisfies FCC MPE Main Reflector Surface Ssurface 0.0923 Satisfies FCC MPE Near Field (Rnf = 143.0 m) Snf 0.0430 Satisfies FCC MPE Transition Region (Rnf < Rtz < Rff) Stz 0.0430 Satisfies FCC MPE Between Reflector and Ground Sg 0.0231 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 upon the above analysis, it is concluded that FCC RF Guidelines have been exceeded in one of the zones in the Uncontrolled (Table 4) and none of the zones in the Controlled (Table 5) environment. The applicant proposes to comply with the Maximum Permissible Exposure (MPE) limits of 1.0 mW/cm**2 for the Uncontrolled Areas, and the MPE limits of 5.0 mW/cm**2 for the Controlled Areas. The earth station dish antenna will be mounted on a platform; so the applicant agrees that the antenna will be in an area secured from the public and worker personnel not familiar with the earth station system. The only zone in Table 4 (Uncontrolled Environment) in which the FCC MPE limits are exceeded is between the main reflector and the subreflector, which will be well within the secured area. Non-assigned worker personnel and the general public must be accompanied by knowledgeable earth station personnel when they enter the earth station secured area. The applicant agrees to abide by the conditions specified in Condition 5208 provided below: Condition 5208 - The licensee shall take all necessary measures to ensure that the antenna does not create potential exposure of humans to radiofrequency radiation in excess of the FCC exposure limits defined in 47 CFR 1.1307(b) and 1.1310 wherever such exposures might occur. Measures must be taken to ensure compliance with limits for both occupational/controlled exposure and for general population/uncontrolled exposure, as defined in these rule sections. Compliance can be accomplished in most cases by appropriate restrictions such as fencing. Requirements for restrictions can be determined by predictions based on calculations, modeling or by field measurements. The FCC's OET Bulletin 65 (available on-line at www.fcc.gov/oet/rfsafety) provides information on predicting exposure levels and on methods for ensuring compliance, including the use of warning and alerting signs and protective equipment for worker.


Document Created: 2014-12-09 12:19:10
Document Modified: 2014-12-09 12:19:10
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