NSF Coordination Agreement

0048-EX-PL-2007 Text Documents

ViaSat, Inc.

2007-07-18ELS_82609

      wo                                                                  555 Eleventh Street, N.W., Suit&es‘beA MP
                                                                          Washington, D.C. 20004—12094 A/\I{Q
                                                                          Tel: (202) 837—2200 Faxzfi.fi?fli]
                                                                          waw.lw.com                        HN

                                                                          FIRM / AFFILIATE OFFICES
L AT H A M &WAT K l N S LLP                                               Brussels      New York
                                                                          Chicago       Northern Virginia
                                                                          Frankfurt     Orange County
                                                                          Hamburg       Paris
                                                                          Hong Kong     San Diego
      Apl‘ll 12’ 2006                                                     London        San Francisco
                                                                          Los Angeles   Shanghai
                                                                          Milan         Siticon Valley
      DELIVERY                                                            Moscow        Singapore
                                                                          Munich        Tokyo
                                                                          New Jersey    Washington, D.C.

      Marlene H. Dortch
      Secretary
      Federal Communications Commission                                   %E@Eivg@
      445 12th Street, N.W.                                                     ane
      Washington, D.C. 20554                                                APR 1 3 2006




                                                                                        mo
                                                                                      socns
                                                                                  e iatio
                                                                              "inunic
                                                                    FZederal Comm         ele r ission
                                                                                            Comm
      Attn:    Scott Kotler, Internatii onal Bureau
           *
               Trang Nguyen, International Bureau

               Re:      ViaSat, Inc. Supplemental Filing; Call Sign E050318;
                        File Nos. SES—LIC—20051028—01494; SES—AMD—20060314—00440

      Dear Ms. Dortch:

             ViaSat, Inc. hereby submits the enclosed coordination agreement with National Science
      Foundation to supplement the above—referenced pending application.

               If you have any questions regarding this submission, please contact the undersigned at
      (202) 637—1056.



                                                      Respectfully submitted,



                                                      Elizgbeth R. Park


      Enclosure




      DC\$59456.1


*‘ #4/t2/2006    13153     703—292—9034              ASTRONOMY DIVISION   PAGE   A1




           04 5e                   Diviston OF AsTRONOMICAL SciENCES
          £      s                 NationaL SciEnice FounbDaAtIion
          ~HfXe                    4201 Wirson BoULEvARD
                °*                 ArLiNcTon, ViRoiNia 22230 USA

                                   FAX Cover Sheet
                                   Telefax Number: (703) 292—9034




        Date:            April 12, 2006
        Number of pages (including cover sheet):     15

        To:      Elizabeth Park, 202—637—2201

        From:            Dr. Tomas Gergely, NSF
        Phone:           703—292—4896
        FAX:             703—292—9034
        E—mail:          tgergely@nsf.gov


‘984/1?/?885    13:53      703—292—9934                     ASTRONDMY DIVISION                          PAGE   82
    #
a
    &

                                                                                   EXECUTION COPY


                 -                   A Coordination Agreement
                     Between the National Science Foundation(hereinafter "NSF")
                        and ViaSat, Inc. (hereinafter "ViaSat") for Operation of
                                        the ViaSat Arclight AMSS
                                      and Radio Astronomy Sites
                               Jointly Sharing the 14.0 — 14.5 GHz—Band


         ViaSat seeks to license and operate aeronautical mobile—satellite stations (AMSS) over the
         Continental United States (CONUS) on a secondary basis in the 14.0 to 14.5 GHz FSS band.
         The AMSS terminals are part of the Arclight® satellite.communications system aboard general
         aviation and commercial aircraft using transponders in the Geostationary Satellite Orbit (GSO)
         arc, This Coordination Agreement has been prepared in compliance with the rules of the Federal
         Communications Commission (FCC) and the recommendations of the International
         Telecommunication Union (ITU) in effect following the World Radiocommunication
         Conference WRC—03.

            1. Overview

            1.1 The 14.0 — 14.5 GHz—band bas been allocated to mobile—satellite service, now including
                aeronautical mobile—satelliteservice, on a secondary basis, provided that airborne earth
                stations (AES) include specific protection to the radio astronomy service within the 14.47
                —14.50 GHz—band

            1.2 The 14.47 —14.50 GHz—band is allocated to radiovastrono,my service on a secondary
                basis.                                     .

            1.3 ViaSat filed an application for license authorization with the FCC on October 28, 2005,
               File Number SES—LIC—20051028—01492, to operate up to 1000 technically identical AES
               units in the 11.7—12.2and 14.0 —14.5 GHz—bands.

            1.4 These AESs receive from, and transmit tb, the same transponder under control of a
               Ground Earth Station (GES) and Network Operations Center (NOC). They, and the
               terrestrial network to which they are connected, comprise the ViaSat Arclight system.

            1.5 This Coordination Agreement has been prepared to ensure that operation of the Arclight
                AESs conform to the requirements of the FCC and the recommendations of the ITU for
               radicoastronomy protection.

            1.6 ViaSat has the authority to negotiate and sign this Coordination Agreement for the
                Arclight system and the Electromagnetic Spectrum Unit of the NSF has the authority to
               negotiate and sign this agreement for the Radio Astronomy sites listed in Section 2.1.




        NSF Coordination Agreement                      1


, ©a/12/2006      13153        703—292—9034                        ASTRONOMY DIVISION                  PAGE   03
 ru   s



                                                                                        EXECUTION COPY

              2, National Science Foundation Radio Astronomy Observatories

              2.1 Site Table

                 Following is a list ofNSF supported Radio Astronomy sites within the United States and
                 its territories which may make observations in the14.47 ——14.50 GHz—band. Two
                 different levels ofprotection are provided for these sites during periods when they are
                 performing observations, as detailed in Section 3.

                  Observatory                                  ‘                Latitude Longitude
                          '                                                      (D,M.S) (D.M,S)
                « ‘National Radio Astronomy Observato       O) sites:
                      GreenBank, WV ( National Radio Quiet Zone)                38 25 59    79 50 24
                      Socorro, NM                                               34 04 43   10737 04

                  National Astronomy and Tonosphere Center (NAIC) site:             >
                      Arecibo, PR (tentative addition to site list).            18 2046     6645 11

                  Very Long Base Array sites, CONUS:
                     Kitt Peak, AZ                                              315722     1113642
                      Owens Valley, CA                                          3713 54    11816 34
                      N. Liberty, IA                                            41 46 17    91 34 26
                      Hancock, NH                                               42 5601     71 59 12
                     . Los Alamos, NM                                           35 46 30 106 14 42
                     Pie Town, NM                                               34 18 04   108 07 07
                     Ft. Davis, TX                                              30 38 06   103 56 39
                     Brewster, WA .             '                               48 07 53   119 40 55
                  Very Long Base Array sites, off shore                                     1
                      Mauna Kea, HI                                             1948 16    155 27 29
                      St. Croix, VI    _                                        174531     6435 03


             2.2 Additional Radio Astronomy Sites |

                 Additional Radio Astronomy sites may be added to the list in 2.1 above. NSF shall give
             ViaSat at least two months notice of additional sites which may be using the 14.47 — 1450
             GHz—band for observations or of changes   instatus to the existing sites.




          NSF Coordination Agreement                       2


~B4/12/2006    13153       703—292—9934                       ASTRONOMY DIVISION                         PAGE   4
+



                                                                                      EXECUTION COPY

         3. Operational Coordination Agreement

              NSF and VIASAT agree to the following:

         3.1 The purpose of this Coordination Agreement is to provide protection to the Radio
             Astronomy sites listed in the site Table of 2.1 during periods ofobservations in the 14.47
             —14.50 GHz—band to the following aggregate power flux density (pfd) levels within that
             band:

                    ~a. ~221 dBW/m"/Hz, for the Green Bank, Socorro and Arecibo sites
                      b. —189 dBW/mZ/Hz for the VLBA sites >

         3.2 This Coordination Agreement should be reviewed periodically by all signatoriesto the
             agreement beginning within a year following commencement of service by ViaSat under
              an operational license from the FCC. The purpose ofthereview is to assess the
              effectiveness of this agreement as well as to update this, or successor operational
              agreements, as applicable.

         3.3 Each party shall inform the other party in a timely manner of changes in the points of
             contact as defined in Section 5.

              ViaSat agrees to: _

         3.4 Cease transmissions from AESs in the 14.47 — 14.50 GHz—band, within line—of—sight of
             Radio Astronomysites listed in the site Table of 2.1, during periods of notified radio
             astronomy observations.                      .

        :3.5 Control the AES transmitters so that the pfd levels in the 14.47 — 14,50 GHz—band,
             produced by individual AES, measured at the radio astronomy sites during periods of
             notified observation, do not exceed the following levels:

                       pfd (dBW/m‘/MHz)=—182 +0.5 * 0 for0 <10°
                       pfd (dBW/Aan/MHz) =—177        for 10° «0 <90°
                       where 0 is the angle of arrival at the receiving site

              This will be accomplished by operating on transponders that—are sufficlently removed
              from the RA frequencies and by reducing or ceasing AES transmissions in the vicinity of
              Radio Astronomy sites during penods ofnotified radio astronomy observations.

        3.6 Respond expeditiously to an NSF request for protection in accordance with Sections 3.4
              and 3.5 of any site listed in site Table 2.1, for observationsof special transient celestial
              objects (comets, supernovae and other celestial objects of heretofore unknown type) that
              are not anticipated by the observation schedule in Section 3.7, and that may need to be
              accommodatedon shorter notice. Requests for such observations are not expected to
              exceed 40 hours per calendar year.



     NSF Coordination Agreement                          3


« ©4/12/2006   13153      703—292—9034                     ASTRONOMY DIVISION                         PAGE   05   _




               NSF agrees to: _

          3.7 Maintain an observation schedule in the 14.47 — 14.50 GHz—band for the sites listed in the
               site Table 2.1 and provide this schedule via both e—mail and fax to the designated points
               ofcontact listed in Section 5.2 below at least 7 days prior to the »scheduled observations.

          3.8 Provide through NAIC and NRAQO full access to ViaSat representatives to data relating to
               interference in the 14.47 —— 14.50 GHz—band that may be collected during observations
               that fall within the scope of this Coordination Agreement.


          4; Assignment and Termination

          4.1 This Coordination Agreement shall be binding upon the parties hereto and their
              respective successors and assigns. .

          4.2 This Coordination Agreement may be terminated by either party upon 6 months of
           , written notice.


          5. Points of Contact

         ~ 5.1 Points of contact concerning this Coordination Agreement:

               Contact: Dr. Tomas E. Gergely                         Namé: Keven Lippert
               Title: Electromagnetic Spectrum Manager               Title: Associate General Counsel
               Organization: National Science Foundstion             Organization: ViaSat, Inc.
               Address: 4201 Wilson Boulevard, Room 1030           > Address: 6155 El Camino Real
                        Arlington VA 22230 USA                                Carlsbad, CA 92009—1699
               Telephone: (703) 292—4896                            Telephone: (760) 476—2214
               Facsimile: (703) 292—9034        '                   Facsimile: (760) 929—3926
               e—mail: tgergely@nef.gov                             e—mail: keven.lippert@viasat.com



          5.2 Points of contact for Radio Astronomy observation schedules:

               Contact: Dr. Harvey Liszt                            Name: Daryl T. Hunter, P.E.
               Title: Director, Spectrum Management                 Title: $r. Systems Engineer
               Organization: NRAO                                  ~ Organization: ViaSat, Inc.
               Address: 520 Edgemont Rd.                            Address: 6155 El Camino Real
                        Charlottesville, Va. 22903                   .        Carlsbad, CA 92009
               Telephone: (434) 296—0344                            Telephone: (760) 476—2583
               Facsimile: (434) 296—0278                            Facsimile: (760) 929—3941
               e—mail: bliszt@nrao.edu                              e—mail: daryl.hunter@viasat.com




      NSF Coordination Agreement                     = 44 ~


‘       54/‘12/2@86    13:53     703—292—9034                     ASTRONOMY DIVISION                    PAGE   D6
    4



                                                                                       EXECUTION COPY


                 6. Signatures


                     This Coordination Agreementis being made in good faith by both parties and is effective
             on the date on which the later party signs it. It may be executed in one or more counterparts,
             each of which will be deemed an original, and all of which together will constitute one and the
             same instrument.

                       For the National Science Foundation:              For ViaSat, Inc.      .


                       By:_({n_ E. Qé% C                              ; By: %_
                                                                             _{%
                                                                               47L
                      _ Name: Dr. Tomas erg;Iy                           Name: Keven Lippert
                        Title: Electromagnetic Spectrum Manager          Title: Associate General Counsel

                       Date: L//o 1106          C                        Date: ~2/7 ?/oé >




            NSF Coordination Agreement                        5


"ga/i2/ross             i3:53         703—292—9034                           ASTRONOMY DIVISION                          PAGE      07
«
    s



                                                                                                  EXECUTION COPY


                                                                   Attachment
                                                           The ViaSat, Inc. AMSS Plan
                                                           To Protect Radio Astronomy


                 Overview

                There are three methods that will be employed to provide protection to the NSF sites
        1       from interference by ARES terminals. These methods are: frequency selection; AES
                 tmnsnnssmn power control; and geographical avoidance of the coordinated sites.

                There are two different protection criteria identified by the NSF. Interference thresholds
                for the Arecibo, PR, Green Bank, WV, and the Socorro, NM sites are -221 dB(W/(m
                Hz)), and the Very Long Baseline Array (VLBA) sites are —189 dB(W/(m +Hz))—
                aggregate power flux density.

                _Method One —— Frequency Sclection k

                Figure 1 depicts the trahsponder frequency arrangement for SES Americom‘s AMC—6, a
                typical Ku—band Fixed Satellite Service (FSS) satellite operating in a geostationary orbit
               _ providing service to the continental United States (CONUS).

                                                                        Uplink
                        13875         13055                     44100 4140 44180 14220 44280 14800 d4a4o 14880 dea20 sadeo. .) |
            . H Pol |           J 1       :                     L_J L     LE          L_G L       L     L     L iss
                         25            ar                         5    7    »     11    13    15    i7    19    2t
                                                                                                           t
                        1s7s          1ao5s                  44080 14120 q4t60 14200 14240 14280 14920 14300 14400 148
             Y Pol |            I L               |          L_J L__ L_J L                PL_J L__ L__ L_J
                         26            28                    . 4     6     a    10    12     14   18    18    20

                          Extended                                   Frequency MHz



                                                                       Bownlink
                  mers 0              t1sss     11720 > 11760 11800 t1840 diaso 41920 itoso 42000 12040 12080 42120 12180
            VP°‘]_     J 1                    JJL__J L__ L         L     L L EO L                L     U L         J L__
                   25                  ar         10    2s      5     7     9    11    13    18    i7    19    2      23
                     11575            11855           C 41740 rn7eo a1e20 meso +1800. r1940 ddeeo 12020 12060 12100 q2i40 dzi8e
            H Pol |__      1 |                J         L_J L_J L        L    L            JL__ L__} EJ L__MOL           L
                      28               28                 2     4     8    8     10     12   14    16    18    2o    22    24
                                                                    Frequency MHz


* ‘@4/12/2006    13153       703—292—9034                          ASTRONDMY DIVISION                    PAGE   9B



                                                                                       EXECUTION COPY


           There are twofrequency ranges that require protection, 14.0 — 14.05 GHz (NASA) and
           14.47 — 14.5 GHz (NSF). By inspection of Figure 1 it is clear that frequencies supported
           by transponders 1, 2, 23, 24 fall within the protected ranges. The next step is to
           determine how much attenuation can be achieved by frequency separation. Figure 2
           shows the spectral mask imposed by Section 25.202(f) of the FCC rules.

           The actual performance of the ViaSat AES is considerably better than this mask. Figure
           3 shows a measured spectrum plot of the ViaSat AMSS terminal‘s GMSK modulation
           measured at the output of the power amplifier and the Section 25.202(f) spectral mask,
           Inspection of the spectrum in figure 3 shows that 36 MHz away from the center
           frequency, the power spectral density is down 55 dB and beyond 40 MHz is generally 65
           dB below the specified PSD.

           By inspection of the transponder plot in Figure 1 and the spectral output of the modem in
           Figure 3, we can determine to what degree frequencies in addition to the above need to be
           considered in the protection strategy. In addition to transponders 1, 2, 23, and 24,      _
           transponder 22 is precluded from use during periods of radio astronomy observations ~
           and transponder 3, portions of which fall within the 14.0—14.05 GHz band used by NASA
           at the other end ofthe spectrum, must be—avoided as well.                                        .

           The key finding is that only transponders 21 and those at lower frequencies are practical
           for AMSS service with some additional attenuation necessary during periods of radio
           astronomy observations.

           B1b   .<—ooececeemensencecemenenees                      f
                                                             sow }
                                                                  ~ 1
                                                                    tC
           MUB Conecccecencennsemccee~s                             :
                                                        1oo% 1
                                                     K—————1
                                          >                         I
           s8uB <_——4~—_~~—                                         I

                                      ‘       2so%
                                                       [M          I
                                                                   1               ,
                               f6——_————_~_.__                                 1
                                                 .               ‘4            +
           sos _ _       .                                          I                        nnnnnnoenans
           eR    C                                          Canter Froquency

                                  Figure 2 FCC 25.202(f) Transponder Spectral Mask


+* #4/12/2006   13:53             703—292—98034                                    ASTRONOMY DIVISION                                            PAGE   03



                                                                                                                 EXECUTION COPY


                                                         AES Transmit PSD and Specification




                 £0.00

                ~100.00

                110.00
                     14.220       14.240     14.260     14280      14.300        14.300        14.340   14.350    14.380       14400     16420
                                                                            Frequency in GHz                               >


                          =—AIST Trangmit Spectrum meesured wih 1MHz RBW and recomputed for 4KHz RBW      ——36 MHz Transponder Spectral Mask



                                                  Figure 3 AES GMSK Spectral Ontput Plot



           Method Two —— AES Transmission Power Control

           The ViaSat AMSS system has been designed to be compliant with ITU—R
           Recommendation M.1643, Annex 1, Part C, which has been accepted and implemented
           by the Federal Communications Commission subsequent to the World
            Radiocommunication Conference WRC—03. Figure 4 shows the limitations imposed on a
            single AES by that Recommendation for radio astronomy and by the coordination
          © agreement for the National Radio Astronomy Observatory (NRAO) (includes the
            National Radio Quiet Zone (NRQZ) site at Grcen Bank, WV), and National Astronomy
            and Ionosphere Center (NAIC) sites.


g0   tC #4/12/2006                                             13153   703—292—9934                             ASTRONOMY DIVISION                           PAGE   10



                                                                                                                                                EXECUTION COPY



                 Power Flux Denalty {dB@Wi(m*2 * 180 ktizy]

                                                              &
                                                              &
                                                              8




                                                              +120


                                                              «140
                                                              &




                                                              «180



                                                                               8         &             &             8          < B         0   £
                                                                                      Angle of Arrival (Thets) [degress above horlzontal}


                                                                       Figure 4 Maximum Permitted PFD from a Single AES Terminal

               © Annex 2 to ITU—R M.1643 provides a method for defining a lower hemisphere EIRP
                mask from a power flux density (pfd) mask. Given the altitude ofthe aircraft and the
                angle below the horizontal of the radio signal departing from the AES, the angle of
                arrival ofthe radio signal at the Earth is determined along with the spreading loss from
                the AES to the considered point on the Earth‘s surface.

                The resultant mask gives the maximum allowed EIRP density for the specified pfd mask.
                Figure 5 shows the resultant radio astronomy masks for several AES altltudes and the
                NRQZ and VLBA masks for 5,000 ft.


‘€4/1272006                              13:53   703—292—9034                             ASTRONOMY DIVISION                              PAGE   11



                                                                                                                     EXECUTION COPY




                                                                                                           ——RA EIRP limit at 50,000 ft
                                                                                                           + ~NROZ EIRP Limit at 5,000
          RA EIRP Mask faB(WFHSO KHz]]
                                         &
                                         &
                                         &




                                         —100




                                                  ros     &     &#   6                    #0
                                                                     Angle Downfrom Horizontal [Dogrees]


                                                  Figure 5 EIRP Démity Mask per 150 kHz for Varions Altitudes

         With the emission limits established, the next steps are to derive and plot the AES EIRP
         density as a function of angle below the horizontal and compare the results to the mask
         and to the NSF site protectnon requirements. ‘The first step in that process is to compute
         the EIRP density in the main lobe of the AES at bores1ght Usingdata from the link
         budget for a typical AES terminal operating at 128 kbit/s in CONUS, the EIRP is 31.3
         dBW. The occupied bandwidth is 30.346 MHz, so the EIRP density is —43.52 dB(W/Hz),
         or $.24 dB(W/150 kHz) — the reference bandwidth used in ITU—R M.1643 Annex 1 Part
         c.                                                                           |                       j
         Having determined that the boresight EIRP density for the AES terminal is 8.24
         dB(W/150 kHz), the next step is to apply the antenna gain as a function of elevation
         angle relative to the main lobe to determine a lower hemisphere EIRP density.

         ‘When operating on the AMC—6 spacecraft, the lowest operating elevation angle for
         CONUS is 15.4°, when operating in the Seattle, WA area. The pointing angle with
         respect to the satellite remains constant, regardless of changes in aircraft attitude.

         The mechanical lower limit for antenna pointingis 6 degrees and if, due to aircraft
         maneuvers, the antenna can not remain pointed at the satellite, the transmitter will be
         inhibited. The only effect of aircraft maneuvers therefore is to the change the effective
         masking of the signal by the airframe.

         For the purposes of this plan, airframe masking is estimated to be 10 dB.


+ * #4/12/2006    13:53    703—292—9034         .                   ASTRONOMY DIVISION                  PAGE   12



                                                                                    EXECUTION COPY



            Figure 6 depicts the relative E—Plane (elevation) off—axis gain of the ViaSat AMSS
            antenna compared to the boresight gain. Also shown in figure 6 is a relative antenna gain
            mask used for calculation purposes in this plan. It shows a —30 dB floor for relative gain
            for off—axis angles greater than 26.5°.                                      ‘

            Next this relative antenna gain mask is combined with the 8.24 dB(W/150 kHz) AES
            EIRP density and the 65 dB of out ofband attenuation and then overlaidon the Radio
            Astronomy mask in Figure 7. We see that with this antenna pattern the NRQZ and
     I      VLBA sites are protected for all angles of arrival as long as the AES is above 5,000 ft.;




                 «1




                                 TE IIIIEaCTEITIIIEE EFFTIEE:
                                                     "a C 2R CC
                                                      Gif—Ades Angls [Dspress]

                                           Figure 6 Relative Off—Axis Gain—


+C cgarre/ress                             is:ss   703—292—9034                           ASTRONDMY DIVISIDN                                     PAGE   13



                                                                                                                          EXECUTION COPY

                                                                  EIRP Desntly and Masks In dB(W/150 kHz)


                                                                                                                =RA EIRP Mask at 5,000 ft
                                                                                                            ———RA EIRP Mask at 30,000 f .
                                           his B                                                            w== = NROZ EIRP Mask at 5,000 it
                                                                                                            — =—VLBA EIRP Mesk at 5,000 f
                                                                                                            ==——~AES EIRP with 65 dB OOB Loes
             RA EIRP Maak (dH(WHSO khtey
                                           &




                                                    T      &      &    m     %     &0     %      i0    80      io     &            2        o5
                                                                        Angle Down from Hortzontal [Degraes]                            ‘

                                                            Figure 7 AES EIRP Density and RA Masks

            Assuming a 65 dB out of band attenuation value, a lower hemisphere elevation antenna
            pattern mask as good as, or better than the one used in figure 6 would be required to
            support unrestricted operation on transponders—4 — 21 down to 30,!000 feet at angles of
            arrival of 65° or higher. >                       —

            This is consistent with ITU—R Recommendation M.1643,which states that AMSS earth
            stations should not                          transmit in the 14.47—14.5 GHz band within line—of—sight of radio
            astronomy stations operating within this band. L                                                     ;

            The data presented thus far has been limited to a—single AES terminal operating at a
            nominalEIRP for a 128 kbit/s data transmission. The ViaSat AMSS network will be
            comprised ofmany aircraft each equipped with a technically identical ViaSat AMSS
           ~terminal. All ABS terminals operate under control of the Network Management System
            (NMS) located at the Network Operations Center (NOC), The NMS software manages
            the multiple user aspects of the system.

            Each AES terminal operates in a continuous receive, burst transmit mode. The terminal
            only transmits when the user has data to send, i.e., mouse clicks, URL address requests,
            emails, and so on. Additionally, the terminal will respond to periodic polis for status
            from the NMS. Network statistics indicate that the majority of the time the AES terminal
            is quiet and not transmitting.


* ‘ga/r2/2g06                      13:53     703—292—9034                           ASTRONOMY DIVISION                  PAGE   14



                                                                                                        EXECUTION COPY


           The link budget data shows that the number of simultaneous transmitters for this network
           is 34. The network itself is designed to accommodate a large number of logged in usets,
           most of which are not transmitting at any given time. The NMS manages Network
           capacity by monitoring the number of simultaneous transmissions and applying
           "throttling" commands to the terminals in the network if the average number of
           simultaneous transmissions reaches a configured limit.

           Given the spatial separation ofthe AES terminals in the network and the fact that the
    .      terminal does not transmit unless there is user data to send, the likelihood of a significant
    i      numbeér of AES terminals transmitting at the same time while in the vicinity of a RA site .
           is low.

                                                                Maximum PFD from a ViaSat AES
            PFD (dBWilm®2* Hayl}




                                                     s    oR         #     &        B       &   B   &   #   &       &
                                                                         Angle of Arrival

                                           Figure 8 Maximum AES PFD ate Selected Altitudes vs. Angle of Arrival '

          Figure 8 shows the PFD from a single AES operating at various altitudes. This figure
          includes the 65 dB of out of band attenuation and 10 dB of airframe shielding. When
          operating at a flight level of 30,000 ft there is 17.7 dB ofmargin above the NRQZ
          aggregate PFD limit. Even if all 34 aircraft were above a NRQZ site and transmitted
          simultancously (fromabove, 34 is the maximum number ofaircraft in the network
          allowed to transmit smmltaneous!y by the NMS) there would still be 17.7 — 10 * log(34}
          =2.38 dB ofmargin in meeting the aggregate PFD limit..

          This is a pathological case as Internet usage statistics suggest a ratio in the 30:1 range for
          a less than 1% chance that users would request data at the same time, i.e., out of 300
          users, less than 10 would likely request data at the same time.


° ‘@q/i2/regs   13153     703—292—9034                      ASTRONOMY DIVISION                       PAGE   15



                                                                              EXECUTION COPY



           The ViaSat AMSS ABS terminals are programmed with the locations of the protected
           sites and equipped with algorithms that determine when an AES must cease transmission
           while operating in the vicinity of a protected site. ViaSat will monitor network
           operations and update the AES operating parameters periodically as required to ensure
           that AES terminals inhibit their transmissions as required to adequately protect NSF sites
           during periods of scheduled observations.

           Method Three — Geographical Avoidance

           The final protection method is geographical avoidance. As previously noted, ITU—R
           M.1643 and subsequently the FCC, requires that the SFD masks for both types of
           radicastronomy sites are met. As determinéd above, the AES must inhibit transmission
           within line—of—site of any RA site during periods of radio astronomy observations. To
           ensure that this requirement is met the AMSS system operator must be notified of which
           sites will be active and at what—times. The AMSS operator must then load this
           information into the Network Management System so that it can be broadcast to all active
           aireraft. The aircraft will then be required to inhibit transmissions by transponders 21—24
           while within line of sight of the affected observatory .                           ,
           ViaSat will make the locations and schedulesvof radio aéfionomy sites available to its
           customers so they may modify flight paths if they choose, to avoid the coordination zone
           and thereby avoid loss of Internet communications during the flight.

          Finally, the location ofeach aircraft equipped with the AMSS system is logged
          throughout their flight. This data is maintained.at ViaSat and can be used to help
          determine if an aircraft was near a site when interference by ViaSat was suspected. This
          data will be reviewed periodically to produce such statistics as the closest aircraft
          approach to a protected site, aircraft heading, minimum altitude over the site, and
          maximum number of aircraft simultaneously within the protection zone for the site.
                                                                         (
                                                                         1



Document Created: 2007-07-18 15:49:33
Document Modified: 2007-07-18 15:49:33

© 2026 FCC.report
This site is not affiliated with or endorsed by the FCC