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.
             _
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 )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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