Attachment Rad Haz Study

This document pretains to SES-MOD-20130228-00229 for Modification on a Satellite Earth Station filing.

IBFS_SESMOD2013022800229_987740

RADIATION HAZARD STUDY DIGITALGLOBE, PRUDHOE BAY EARTH STATION When applying for a license to construct and operate, modify, or renew an earth station, it is understood that licensees must certify whether grant of the application will have significant environmental impact as defined in the Federal Communications Commission‘s (FCC) rules, 47 C.F.R., Section 1.1307. In this report DigitalGlobe, Inc. analyzes the maximum radiofrequency (RF) levels emitted from the satellite communications antenna described below. The reference documentfor this study is OET Bulletin No. 65, Edition 97—01, Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields, August 1997. ANTENNA NEAR—FIELD PoOWER DENSITY CALCULATION The extent of the near—field is defined by the following equation: Rnear= (Dant)2 / (4 2 ) where: Rnear= extent of the near—field (in meters) Dant= diameter of the antenna main reflector (in meters) A¥ =wavelength of the RF transmit frequency (in meters) The maximum on—axis power density within near—field is defined by the following equation: Snear = {(16 n Pfeed) / [TC (Dant)z]}/ 10 where: Snear= maximum on—axis power density within the near—field (in milliwatts per square centimeter) 1 =antenna aperature efficiency Preed = maximum power into antenna feed flange (in watts) Dant= diameter of the antenna main reflector (in meters) ANTENNA FAR—FIELD PoOWwER DENSITY CALCULATION The distance to the beginning of the far—field region is defined by the following equation: Rfar= [0.6(Dant)z] / A where: Rrar= distance to beginning of far—field (in meters) Dant= diameter of the antenna main reflector (in meters) A¥ =wavelength of the RF transmit frequency in (meters)

The maximum on—axis power density within the far—field is defined by the following equation: Sfar= [(Pfeed Gant) / 4 r (Rfar)z] / 10 where: Sfa= maximum on—axis power density in the far—field (in milliwatts per square centimeter) Preed = maximum power into antenna feed flange (in watts) Gant= antenna main beam gain at RF transmit frequency (in watts) Rrar= distance to beginning of far—field (in meters) ANTENNA TRANsITION REcion PoOwER DENSITY CALCULATION By definition, the maximum on—axis power densitiy in the transition region will never be greater than the maximum on—axis power densities in the near—field: StrS Snear where: Sir= maximum on—axis power density in the transition region (in milliwatts per square centimeter) Snear= maximum on—axis power density in the near—field (in milliwatts per square centimeter) ANTENNA FEED—FLANGE (OR SUBREFLECTOR) POWER DENSITY CALCULATION The maximum power density at the antenna feed—flange (or subreflector surface) is defined by the following equation: Sfeed(sub) = 1000 {[2(Preed)] / {{ x (Dreed(sub)}2] / 4}} where: Sfeed(sub) = maximum power density at the antenna feed—flange or subreflector surface (in milliwatts per square centimeter) Preed = maximum power into antenna feed flange (in watts) Dfeed(sub) = diameter of the antenna feed—flange or subreflector (in centimeters) ANTENNA MAIN REFLECTOR POWER DENSITY CALCULATION The maximum power density in the main reflector region of the antenna is defined by the following equation: Sant= {[Z(Pfeed)] / {[ T [Dant)z] /4—}} / 10 where: Sant= maximum power density in the antenna main reflector region (in milliwatts per square centimeter) Preed = maximum power into antenna feed flange (in watts) Dant= diameter of the antenna main reflector (in meters)

PowER DENSITY CALCULATION BETWEEN THE ANTENNA MAIN REFLECTOR AND THE GROUND The maximum power density between the antenna main reflector and the ground is defined by the following equation: Sground = {Pfeed/ {[ T (Dant)z] /4}} / 10 where: Sground = maximum power density between the antenna main reflector and the ground (in milliwatts per square centimeter) Pfeed = maximum power into antenna feed flange (in watts) Dant= diameter of the antenna main reflector (in meters) SUMMARY OF CALCULATED RADIATION LEVELS DigitalGlobe, Inc. understands the licensee must ensure people are not exposed to harmful levels of radiation. Maximum permissible exposure (MPE) limits for general population/uncontrolled exposure were not considered in this analysis for several reasons. The main—beam height above ground, minimum 3 degree elevation above horizon transmit inhibit mask and tracking motion of this highly directional antenna significantly limit exposure to the general population. Furthermore, access to DigitalGlobe earth stations is limited to authorized personnel who have been appropriately briefed and advised. MPE limits for occupational/controlled exposure, however, were considered in this analysis. It is standard practice for our technical staff to cease transmissions whenever maintenance is performed in close proximity to antenna reflector regions with potentially hazardous power density levels. Based on the results (see attached page entitled "Radiation Hazard Calculations") and our standard practices within our controlled antenna environment, the earth station operators / technicians should not be exposed to radiation levels exceeding 5 mW/cm2 power density over a six minute averaging time. CERTIFICATION I hereby certify that I am the technically qualified person responsible for preparation of the engineering information contained in this radiation hazard assessment, that I have reviewed the engineering information submitted, and that it is complete and accurate to the best of my knowledge. _ T 1 q * Lo )M{/ ,\/«G\,,/\/Q ==——* David D. Greenidge Mgr. Remote Ground Systems DigitalGlobe, Inc.

Radiation Hazard Calculations DigitalGlobe Prudhoe Bay Earth Station Antenna Diameter 5.4 m Feed—Flange or subreflector diameter 8.25 cm Transmit Frequency 2025 Mhz Maximum power into antenna feed—flange (watts) 100 W Antenna Gain 36.6 dBi Antenna aperture efficiency 0.55 Maximum power into antenna feed (dBm) 50.00 dBm EIRP (dBm) 86.60 dBm EIRP (watts) 457088.19 W Wave length 0.15 m Near field extent 49.21 m Beginning of far field 118.10 m Maximum on—axis power density far field 0.26)mW/cm4*2 Satisfies MPE Limits Maximum on—axis power density near field 0.96|mW/em*2 Satisfies MPE Limits Maximum on—axis power density transition region 0.96)mW/cm*2 Satisfies MPE Limits Maximum power density feed—flange 3741.38|mW/cmA2 Potential Hazard Maximum power density main reflector region 0.87|mW/cm42 Satisfies MPE Limits Maximum power density between main reflector and ground 0.44)mW/omA2 Satisfies MPE Limits


Document Created: 2019-04-12 09:24:30
Document Modified: 2019-04-12 09:24:30
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