SpaceX Response to O

LETTER submitted by Space Exploration Holdings, LLC

SpaceX Response to OneWeb

2019-04-15

This document pretains to SAT-MOD-20181108-00083 for Modification on a Satellite Space Stations filing.


April 15, 2019


BY ELECTRONIC FILING
Marlene H. Dortch
Secretary
Federal Communications Commission
445 Twelfth Street, S.W.
Washington, DC 20554

         Re:      Space Exploration Holdings, LLC, IBFS File No. SAT-MOD-20181108-00083;
                  WorldVu Satellites Limited, IBFS File No. SAT-MOD-20180319-00022

Dear Ms. Dortch:

        In this proceeding, Space Exploration Holdings, LLC (“SpaceX”) seeks to modify its
existing authorization to deploy and operate a non-geostationary orbit (“NGSO”) satellite system
to relocate 1,584 satellites previously authorized to operate at 1,150 km to 550 km and allow a
limited number of first-generation satellites to use Ku-band spectrum for gateway operations. 1
SpaceX designed this modification to enhance the already considerable safety attributes of its
NGSO system and allow SpaceX to operate at even lower power levels. In reply comments and a
recent ex parte, 2 WorldVu Satellites Limited (“OneWeb”) has raised shifting arguments to
question SpaceX’s technical analysis that shows that the proposed modification will not result in
additional interference to other NGSO systems, including OneWeb. 3 As discussed below,
OneWeb consistently ignores facts on the record and demands new analyses that are neither
required under Commission rules nor, tellingly, consistent with the approach that it has used for
its own interference analyses. Nonetheless, to alleviate any remaining concerns, SpaceX provides
yet more analysis to demonstrate that even under OneWeb’s proposed approach, SpaceX’s bottom-
line conclusion does not change – its proposed modification simply does not increase interference.
        Several aspects of the proposed modification combine to further reduce the potential for
radiofrequency interference beyond the operations that the Commission already authorized
SpaceX to conduct. For example, SpaceX proposes to decrease slightly the number of satellites in
its constellation from 4,425 to 4,409. In addition, operating at a lower altitude will reduce
radiofrequency interference in two fundamental ways: fewer satellites will be visible above the

1
    See Application for Modification of Authorization for the SpaceX NGSO Satellite System, IBFS File No. SAT-
    MOD-20181108-00083 (Nov. 8, 2018) (“SpaceX Modification”). Unless otherwise noted, all submissions cited
    herein were filed in this same IBFS file.
2
    See Reply of WorldVu Satellites Limited (Mar. 5, 2019) (“OneWeb Reply”); Letter from Brian D. Weimer to
    Marlene H. Dortch (Apr. 3, 2019) (“OneWeb Ex Parte”).
3
    See Further Consolidated Opposition to Petitions and Response to Comments of Space Exploration Holdings,
    LLC (Feb. 21, 2019) (“SpaceX Response”).



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minimum elevation angle at any particular time at any point in the U.S., and the satellites will
transmit and receive at lower power levels. As SpaceX noted in its application, in granting a
previous NGSO modification application, the Commission recognized such factors as
demonstrating that a modification will not increase interference to other NGSO systems. 4
        OneWeb does not try to address (much less refute) this Commission precedent or the
common-sense factors on which it is based. Instead, it offers varying critiques of certain aspects
of SpaceX’s analysis, but does not – because it cannot – demonstrate that implementation of its
preferred approach would yield a different conclusion. To be clear, OneWeb has all the data
necessary to provide its own analysis to the Commission, but it repeatedly chooses not to do so.
OneWeb’s approach to criticize but not analyze seems explicitly designed to sow confusion rather
than bring clarity to the record. But despite these efforts, SpaceX’s analysis below will show once
again that the results are the same regardless of the process.
        In its critique, OneWeb takes no issue with the operation of up to one million SpaceX user
terminals in the Ku-band. 5 Instead, it has focused on SpaceX’s proposal to use as part of its initial
operations a few gateways in Ku-band spectrum, involving up to four satellites communicating
with a single site at one time. OneWeb consistently repeats its unsupported claim of widespread
interference while ignoring the established facts in the record that SpaceX will use only a limited
number of gateways communicating with a limited number of satellites in the Ku-band. For
example, OneWeb continues its baseless assertion that SpaceX will deploy “hundreds” of Ku-band
gateways across the U.S. 6 To the contrary, as SpaceX previewed in its Response, SpaceX has filed
applications for just six Ku-band gateways in the U.S. 7 – and has no current plans to request more.
        SpaceX made clear in its modification application that only a limited number of first-
generation satellites will use the Ku-band for gateway communications for a discrete period of
time, until it transitions to Ka-band for gateways communications. Specifically, SpaceX
anticipates that it will deploy fewer than 75 satellites that use Ku-band spectrum for gateway
operations. As a practical matter, four of these first-generation satellites will rarely, if ever,
converge and communicate simultaneously with a given Ku-band gateway. Accordingly, the
worst-case scenario envisioned by OneWeb is unlikely to ever occur and, even if it did, would
only be possible over six locations in the U.S. for a limited period. OneWeb’s asserted fear seems
even more specious given that it has not even applied for a single Ku-band earth station license in




4
    See Teledesic LLC, 14 FCC Rcd. 2261, ¶¶ 13, 17 (IB 1999) (“Teledesic”).
5
    See IBFS File No. SES-LIC-20190211-00151 (requesting blanket license for up to 1,000,000 Ku-band user
    terminals).
6
    See, e.g., Petition to Deny or Defer of WorldVu Satellites Limited at i (Feb. 8, 2019).
7
    See IBFS File Nos. SES-LIC-20190402-00425, -00426, -00427, -00450, -00451, and -00454.


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the U.S. that could be affected. Moreover, the possibility of an actual in-line event seems even
less likely now that OneWeb has announced it plans to use antennas with “full steerability.” 8
        Below we address several specific arguments raised by OneWeb to demonstrate that its
critique of the analysis submitted by SpaceX is not valid. As noted above, although the technical
details of SpaceX’s proposed operations are a matter of public record, OneWeb tellingly has not
seen fit to present the results of any alternative interference analysis to substantiate its critique.
This notable absence is likely explained by the fact that, as shown below, conducting the analysis
as OneWeb would prefer does not change the conclusion that the proposed modification will not
increase interference to other NGSO users.
         A. Selection of Methodology for Analysis
         OneWeb initially criticized SpaceX for framing its analysis based on a worst-case approach
(choosing links with the highest absolute I/N values), suggesting that SpaceX should instead use
a best-case approach (choosing the lowest I/N at each time step). 9 As SpaceX demonstrated,
OneWeb itself does not use this best-case approach when it submitted an interference analysis to
the International Telecommunication Union (“ITU”) in May 2017 to support its own proposed
NGSO system modifications. 10 In its most recent ex parte, OneWeb essentially concedes this
point, 11 but now contends that SpaceX should have used some other methodology (e.g., highest
elevation, longest hold, or random) to choose the links for assessment. 12

        By presenting the worst I/N for OneWeb from both SpaceX’s currently-authorized
constellation and under the proposed modification, SpaceX described an envelope that would
depict all possible I/N values of a deployed system. In effect, this demonstrates that even in such
a worst-case scenario, the I/N from SpaceX’s proposed modified constellation would be at least
equal to – and often better than – the I/N from the currently authorized system. Such a worst-case
analysis is a common approach when evaluating potential interference. 13

         Nonetheless, SpaceX recognizes different methodologies could be used to choose which
satellite links to evaluate for purposes of developing a cumulative distribution function (“CDF”)
8
     Tweet by OneWeb CEO Greg Wyler (March 29, 2019) (“Thin is in! Results of the Software Defined Antenna are
     super encouraging, achieving 19dBi of gain with full steerability and true time delay in a small tile. The AI control
     software is learning more every day, creating surprisingly good performance improvements.” (emphasis added)),
     available at https://twitter.com/greg_wyler/status/1111659447816982535.
9
     See OneWeb Reply at 3-5.
10
     SpaceX attached OneWeb’s submission (the “OneWeb ITU Analysis) as Exhibit 2 to Letter from William M.
     Wiltshire to Marlene H. Dortch (Mar. 18, 2019). Notably, OneWeb did not present such an interference analysis
     to the Commission in connection with its own requests for changes to its NGSO systems. See IBFS File Nos.
     SAT-AMD-20180104-00004 and SAT-MOD-20180319-00022.
11
     See OneWeb Ex Parte, Presentation at 6 (listing three potential approaches and indicating that the L5 filing does
     not fall under the “Best-Case I/N”).
12
     See OneWeb Ex Parte at 4-5 and Presentation at 6.
13
     For example, as the Commission has recognized, the software used to evaluate NGSO systems’ compliance with
     equivalent power flux-density limits in the Ku-band employs worst-case parameters, and “thereby simulates an


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of aggregate I/N levels. In an abundance of caution, SpaceX re-ran its interference analysis using
two of the alternatives recommended by OneWeb (highest elevation and random) to determine
whether doing so would yield a different conclusion. The results are presented in Attachment A
hereto. All these methodologies, even those endorsed by OneWeb, confirm that interference will
be no worse (and typically better) under the proposed SpaceX modification than under the current
authorization. Accordingly, the Commission should reject OneWeb’s theoretical critique that does
not prove out given SpaceX’s practical demonstration.

         B. Use of Unrealistic Assumptions

          OneWeb also criticizes SpaceX’s analysis as not accurately reflecting its own operations,
since SpaceX would not choose the worst-case link at each time step 14 – a fact that SpaceX noted
itself. 15 However, this is by no means unusual in an interference analysis, where proponents make
simplifying assumptions that cut against their case to show that the results are positive nonetheless.
Indeed, OneWeb followed this approach in the interference analysis it submitted to the ITU, using
what it admitted was an extremely unlikely worst-case scenario for elevation angles to show that
the more likely operating conditions would be even more favorable to other NGSO systems.

         Although it is extremely unlikely that, in practice, such low elevation L5 satellites
         would be transmitting towards this same victim earth station location, this is the
         approach for calculating the worst-case interference, based on the fact that the L5
         satellite antenna beams are steerable in the L5 ITU filing. In reality, the L5 system
         will operate at much higher elevation angles so the total interference into the victim
         system will be much less than predicted in this analysis. 16

Moreover, OneWeb’s analysis assumes that all of its satellites above a given elevation angle would
be “simultaneously radiating their peak EIRP density towards the victim earth station,” even
though the NGSO system OneWeb’s application states that it intends to deploy does not have
steerable Ku-band beams. 17 Thus, the use of counterfactual worst-case assumptions in an
interference analysis should be familiar to OneWeb. Moreover, by far the most significant
counterfactual assumption in SpaceX’s analysis is that there will be thousands of Ku-band-only
satellites communicating with gateway earth stations if the modification is granted, when in fact
there will be no more than 75 satellites communicating with just six gateways. Revising SpaceX’s


     ‘outer envelope’ of acceptable interference by any NGSO FSS system.” Virtual Geosatellite, LLC, 21 FCC Rcd.
     14687, ¶¶ 22-24 (IB 2006).
14
     See OneWeb Reply at 4.
15
     See SpaceX Response, Attachment A at A-5.
16
     See OneWeb ITU Analysis at 5 footnote 2.
17
     See id. at 5; Application, IBFS File No. SAT-LOI-20160428-00041, Attachment A at 7 (filed Apr. 28, 2016)
     (“Each OneWeb satellite will have 16 nominally identical user beams, operating in Ku-band, each consisting of
     a non-steerable highly-elliptical spot beam.”). As noted above, however, OneWeb has announced it is now
     developing antennas with full steerability.


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analysis to reflect those facts alone would have revealed significant improvements over the already
favorable interference environment for other NGSO systems post-modification.

         C. Interference Analysis for OneWeb’s User Terminals
        OneWeb also asserts that, in order to determine the “true worst-case differences in I/N,”
SpaceX should provide an analysis using OneWeb’s user terminals in addition to the analysis of
OneWeb’s gateway antennas that SpaceX has already provided. 18 Accordingly, SpaceX re-ran its
analysis using a range of antennas from OneWeb’s L5 ITU filing. As shown in Attachment A,
SpaceX’s analysis reveals that the gain of the OneWeb antenna used in the analysis does not alter
the bottom-line result. This analysis confirms that the proposed modification will not increase
potential interference into OneWeb’s earth station antennas of any size – neither user terminals
nor gateways – compared to SpaceX’s currently authorized constellation.
         D. Interference Analysis for SpaceX’s Maximum and Minimum Gain Antennas
       OneWeb argues that SpaceX’s analysis is incomplete because it does not include a range
of SpaceX earth station types, and specifically calls for the analysis to consider antennas with
maximum and minimum gain. 19 In response to this critique, SpaceX has re-run its analysis using
the minimum and maximum gain antennas submitted with its ITU filing. Here again, as shown in
Attachment A, the gain of the SpaceX antenna does not alter the conclusion that the proposed
modification will not increase interference compared to the currently authorized constellation.

         E. Choice of Single Latitude for Analysis
        OneWeb argues that SpaceX should have conducted its analysis using more than one
latitude for earth station location. 20 For purposes of the I/N analysis, SpaceX assumed that the
earth stations of both the SpaceX and OneWeb systems are collocated. To capture the worst-case
aggregate interference under the proposed modification, SpaceX selected the latitude for these
earth stations at which the greatest number of SpaceX satellites in the modified constellation would
be visible. As shown in the figure below, the probability of satellites visible above a 10 degree
elevation angle is greatest at 50 degrees North latitude. Accordingly, SpaceX used that parameter
for its analysis. SpaceX also conducted the analysis (but did not present results) using other
latitudes and found that the impact of this variable was very small – just as OneWeb has recognized
in its own analyses. 21




18
     See OneWeb Reply at 6.
19
     See id.
20
     See id.; OneWeb Ex Parte, Presentation at 3.
21
     See OneWeb ITU Analysis at 6 (results at varying latitudes “are very similar”).


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                      Number of Visible SpaceX Satellites at Various Latitudes

          Finally, OneWeb has taken yet a new turn in its most recent ex parte meetings, asking that
the Commission act on its own application for modification “contemporaneously” with SpaceX’s
application. 22 Yet despite OneWeb’s repeated demand for increasingly detailed and specific
analysis from SpaceX – which SpaceX has consistently provided – OneWeb has resisted providing
virtually any analyses of the interference or space safety profiles of its own system as modified to
nearly triple the number of active satellites (from 720 to 1,908) in its NGSO constellation. If
OneWeb truly seeks regulatory parity, it should provide the same analyses that it has demanded
from SpaceX for its own proposed system modification before asking the Commission to act on
its still bare-bones application.

                              *                  *                      *

      The technical analyses submitted by SpaceX confirm what Commission precedent and
common sense already recognize – a modification that proposes to operate fewer satellites at lower
power will not increase interference to other NGSO systems. The Commission should reject
OneWeb’s flawed arguments to the contrary.

                                              Sincerely,




                                              William M. Wiltshire
                                              Counsel to SpaceX



22
     See, e.g., OneWeb Ex Parte at 2.


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cc:     Rachael Bender
        William Davenport
        Umair Javed
        Jessica Martinez
        Erin McGrath
        Tom Sullivan
        Troy Tanner
        Jose Albuquerque
        Karl Kensinger
        Stephen Duall
        Kerry Murray
        Jay Whaley


                                       ATTACHMENT A

                 Revised Dynamic Interference Analysis for OneWeb System

        SpaceX has previously presented an analysis evaluating whether the proposed
modifications to its NGSO system would increase interference to OneWeb’s NGSO system. That
analysis considered the dynamic, time-varying interference expressed as a cumulative distribution
function (“CDF”) of the interference-to-noise ratio (“I/N”), for varying percentages of time. The
I/N CDF was derived from a time-domain simulation of the two NGSO systems over a long enough
time to produce meaningful statistics. To present a worst-case assessment of the interference
environment, the analysis made several assumptions. First, the SpaceX and OneWeb earth stations
were assumed to be collocated. Second, the collocated earth stations were assumed to be located
at 50° N latitude, where the largest number of SpaceX satellites from the proposed modified
constellation will be visible. Third, the analysis assumed that the SpaceX earth station was a
gateway rather than a user terminal, such that up to four SpaceX satellites could transmit co-
frequency, co-polar Ku-band beams at the same time. Lastly, the analysis selected the four
interfering SpaceX satellites with smallest off-axis sepration angle from a given OneWeb earth
station to communicate with the collocated gateway station at each time step.

         OneWeb asserts that this analysis should be conducted using a different approach to this
last assumption. Specifically, it suggests that choosing links for analysis based on the SpaceX
satellite with the highest elevation, or choosing SpaceX satellites at random, would be more
appropriate. In addition, OneWeb argues that SpaceX should consider more than one type of
OneWeb earth station antenna, and the lowest and highest gain antennas SpaceX plans to use. In
order to determine whether proceeding as OneWeb suggests would affect the analysis, SpaceX re-
ran its analysis employing each of those alternative methodologies.

        For purposes of this new analysis, SpaceX used the network filings made by SpaceX and
OneWeb to determine an appropriate range of earth station antennas to consider. Specifically, the
downlink interference analysis considered OneWeb earth station antennas with the lowest gain
(21.6 dBi), mid-range gain (31.1 dBi), and highest gain (41.6 dBi) from the L5 ITU network filing.
Similarly, the uplink interference analysis considered SpaceX’s lowest gain (27 dBi) and highest
gain (53.9 dBi) earth station antennas from the STEAM-1 ITU network filing and the lowest gain
(19.9 dBi) and highest gain (31.9 dBi) space station antennas from the L5 ITU network filing. For
each of these analyses, SpaceX assessed interference using a worst-case satellite approach, a
highest elevation satellite approach, and a random selection satellite approach. The results are set
forth below. In each case, the figure plots a CDF of aggregate I/N levels for the SpaceX
constellation as originally proposed and as modified, using the approach indicated.

        As these figures demonstrate, the new interference levels resulting with the modification
are no worse (and often better) than the interference levels that would have been experienced with
the original constellation for all percentages of time, even using the methodologies suggested by
OneWeb. Accordingly, the I/N CDF analysis confirms that the modification will not increase the
potential interference into other NGSO systems




                                                A-1


  Figure 1. Downlink Comparison for Various OneWeb Antennas – Worst-Case




Figure 2. Downlink Comparison for Various OneWeb Antennas – Highest Elevation




                                    A-2


  Figure 3. Downlink Comparison for Various OneWeb Antennas – Random




Figure 4. Uplink Comparison for Minimum Gain SpaceX Antenna – Worst-Case




                                  A-3


  Figure 5. Uplink Comparison for Maximum Gain SpaceX Antenna – Worst-Case




Figure 6. Uplink Comparison for Minimum Gain SpaceX Antenna – Highest Elevation




                                     A-4


Figure 7. Uplink Comparison for Maximum Gain SpaceX Antenna – Highest Elevation




    Figure 8. Uplink Comparison for Minimum Gain SpaceX Antenna – Random




                                     A-5


Figure 9. Uplink Comparison for Maximum Gain SpaceX Antenna – Random




                                A-6


                              ENGINEERING CERTIFICATION


         I hereby certify that I am the technically qualified person responsible for preparation of the
engineering information contained in this filing, that I am familiar with Part 25 of the
Commission’s rules, that I have either prepared or reviewed the engineering information submitted
in this filing, and that it is complete and accurate to the best of my knowledge and belief.


                                               /s/ Mihai Albulet
                                               Mihai Albulet, PhD
                                               Principal RF Engineer
                                               SPACE EXPLORATION TECHNOLOGIES CORP.

                                               April 15, 2019
                                               Date



Document Created: 2019-04-28 19:30:14
Document Modified: 2019-04-28 19:30:14

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