Row 44 Comments (1-11-2013) COMMENT by Row 44 Inc. SES-LIC-20120427-00404 Row 44 Comments (1-1

Row 44 Comments (1-1

COMMENT submitted by Row 44 Inc.

Row 44 Comments (1-11-2013)

2013-01-11

This document pretains to SES-LIC-20120427-00404 for License on a Satellite Earth Station filing.

IBFS_SESLIC2012042700404_981217

BEFORE THE

Federal Communications Commission
WASHINGTON, D.C. 20554

In the Matter of )
)
ViaSat, Inc. ) File No. SES- LIC-20120427-00404
) Call Sign E120075
Application for Authority to Operate Up to )
4,000 Transmit/Receive Aeronautical-Mobile )
Earth Stations in the Ka-band )

To: Chief, Satellite Division
International Bureau

COMMENTS OF ROW 44, INC.

David S. Keir
Lerman Senter PLLC
2000 K Street, NW, Suite 600
Washington, DC 20006-1809
(202) 429-8970

January 11, 2013 Counsel to Row 44, Inc.

- ii -

Summary

Row 44 is generally supportive of introducing aeronautical-mobile service (“AMSS”) to

the Ka-band as an application of the fixed-satellite service (“FSS”). As the ViaSat Application is

the first request for authority to provide such service, however, it warrants careful scrutiny.

ViaSat’s reliance on specific provisions of FCC Rules applicable to Ka-band FSS is

misplaced. ViaSat is not proposing to operate FSS earth stations, but is instead proposing to

operate AMSS-type earth terminals, a use for which there is no current licensing framework.

ViaSat therefore has an affirmative obligation to demonstrate that it will not cause harmful

interference to other spectrum users.

Accordingly, it is troubling that ViaSat has not filed any documentation that corroborates

the completion of required interference coordination with operators potentially affected by

deployment of its earth station network. Given the recent adoption of a coordination requirement

governing Ku-band Earth Stations Aboard Aircraft, and more importantly for purposes of

nascent Ka-band AMSS, the coordination obligations previously applied on an ad hoc basis to

non-conforming AMSS providers in the Ku-band, this must reasonably considered a minimum

threshold requirement.

Moreover, introduction of mobile applications at Ka-band poses distinct regulatory and

policy questions because of the relatively early stage of development of Ka-band satellite

services. Currently, many potentially usable orbital locations in the band are not yet licensed to

any service provider. As a result, any rushed effort to implement non-conforming services in

these bands, based solely on coordination agreements with the few existing FSS operators, could

have unintended long-term consequences for the development of service in this band.

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Table of Contents

Page #

Summary …………………………………………………………………………………. ii

I. Statement of Interest ……………………………………………………………… 2

II. The ViaSat Application Does Not Comply with the Commission’s Rules ……… 3

A. The ViaSat Application Relies on a Faulty Premise …………………….. 3

B. The ViaSat Application is Incomplete Even under Standards
Established for Ku-band ESAA Applications …………………………… 5

C. Ka-Band AMSS Applications Present Distinct Regulatory and
Policy Issues That Ku-band ESAA Networks Do Not Implicate ……….. 7

III. ViaSat’s Proposed Antenna Appears Ill-Suited to Provide
Ubiquitously-Deployed Mobile-Satellite Service …..…………………………… 8

IV. Conclusion ………………………………………………………………………. 12

Technical Appendix and Certification

BEFORE THE

Federal Communications Commission
WASHINGTON, D.C. 20554

In the Matter of )
)
ViaSat, Inc. ) File No. SES- LIC-20120427-00404
) Call Sign E120075
Application for Authority to Operate Up to )
4,000 Transmit/Receive Aeronautical-Mobile )
Earth Stations in the Ka-band )

To: Chief, Satellite Division
International Bureau

COMMENTS OF ROW 44, INC.

Row 44, Inc. (“Row 44”), by counsel and pursuant to Section 25.154 of the

Commission’s Rules (47 C.F.R. § 25.154), hereby comments on the above-captioned application

filed by ViaSat, Inc. (“ViaSat”) on April 27, 2012. In the application, ViaSat seeks authority to

operate up to 4,000 technically-identical aeronautical mobile-satellite service (“AMSS”) earth

station terminals in the 28.25-29.1 and 29.5-30.0 GHz bands in the Earth-to-space direction and

the 18.3-19.3 GHz and 19.7-20.2 GHz bands in the space-to-Earth direction for the purpose of

providing in-flight broadband services. These AMSS earth terminals would communicate with

three previously authorized Ka-band geostationary (“GSO”) fixed-satellite service (“FSS”)

satellites at the 115.1 W.L. and 111.1 W.L. orbital locations.1 In these comments, Row 44

urges the Commission to adhere to procedures used in its consideration of past applications for

non-conforming mobile uses in FSS bands, bearing in mind the precedent created in the recent

1
See ViaSat Ka-band AMSS Application, SES-LIC-20120427-00404, Call Sign E120075,
Exhibit A at 1 (filed April 27, 2012) (“ViaSat Application”).

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adoption of rules for Earth Stations Aboard Aircraft (“ESAA”) in the Ku-band,2 the initial

processing approach adopted at Ku-band prior to the new rules, and the significant differences

between the state of current development of the Ku- and Ka-bands. The Commission should not

move forward with processing the ViaSat application until the applicant has addressed the

deficiencies in its showing under the FCC’s rules and policies, and until the FCC has considered

carefully the stage of development of Ka-band services and evaluated the specific potential

impact of the ViaSat technical proposal upon such development.

I. Statement of Interest

Row 44’s interest in matters relating to AMSS use of FSS frequency bands is well-

known. Row 44 is the holder of a Ku-band ESAA authorization permitting it to offer in-flight

broadband service to commercial airline passengers and crew.3 As demand for such services has

continued to grow, and the number of airlines seeking to offer such services has increased, there

has been greater interest in the potential for Ka-band satellite capacity to augment existing Ku-

band services. Row 44 is currently exploring options for possible implementation of Ka-band

service at some time in the future, and therefore is concerned that the initial mobile earth station

deployments in this spectrum not compromise future use of the band for long-term, high-quality

services. Introduction of a less than state-of-the-art aircraft-mounted antenna could have an

2
See Revisions to Parts 2 and 25 of the Commission’s Rules to Govern the Use of Earth Stations
Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit Space Stations
Operating in the 10.95-11.2 GHz, 11.45-11.7 GHz, 11.7-12.2 GHz and 14.0-14.5 GHz
Frequency Bands, Notice of Proposed Rulemaking and Report and Order in IB Docket Nos. 12-
276 and 05-20, FCC 12-161, slip op. (released December 28, 2012) (“ESAA R&O and NPRM”).
Generally, in these Comments, Row 44 uses AMSS to refer to aircraft-mounted mobile-satellite
services operating in FSS bands, and ESAA to refer exclusively to the newly adopted regulations
that will soon apply to Ku-band mobile earth station operations on aircraft.
3
Row 44, Inc. Application for Authority to Operate Up to 1,000 Technically Identical
Aeronautical Mobile Satellite Service Transmit/Receive Earth Stations Aboard Commercial and
Private Aircraft, 24 FCC Rcd 10223 (IB/OET 2009).

-3-

adverse impact on other service providers by placing undue constraints on the use of the band, by

establishing the potential for grandfathering of an antenna that actually limits use of the band for

other services, and/or by creating a negative impression in the marketplace of the Ka-band

AMSS generally.

With these concerns in mind, Row 44 is generally supportive of introducing AMSS to the

Ka-band as an application of the FSS. As the ViaSat Application is the first request for authority

to provide such service, however, it warrants careful scrutiny. While the Commission has very

recently adopted new technical and processing rules to govern Ku-band ESAA, no such service

rules have even been proposed for similar operations in the Ka-band. Moreover, the introduction

of this type of application into the Ka-band raises distinct regulatory and policy questions

because Ka-band satellite service generally, and non-FSS applications in particular, are at a

much earlier stage of development than at Ku-band, and the same regulatory approaches cannot

be assumed to apply automatically in the same way that they have been applied to the Ku-band.

II. The ViaSat Application Does Not Comply with the Commission’s Rules.

A. The ViaSat Application Relies on a Faulty Premise.

In the original ViaSat Application, ViaSat asserts that its proposal “is consistent with the

existing regulatory framework for the Ka band,” including “the PFD levels referenced in

25.138,” as well as the off-axis-EIRP levels “except with respect to a few exceedances that can

be coordinated with potentially affected satellite systems.”4 These assertions are misleading, and

ultimately amount to nothing more than an acknowledgment that ViaSat’s proposed operations

are superficially consistent with some elements of the Commission’s Rules but in very material

respects are not compliant with them. ViaSat’s specific reliance on Section 25.138 of the

4
ViaSat Application, Exhibit A at 1.

-4-

Commission’s Rules, for example, is unavailing. The extant Ka-band rules apply on their face

only to FSS applications, whether on an individually-licensed or blanket-licensed basis.5 ViaSat,

however, is not proposing to operate FSS earth stations in the Ka-band. It is instead proposing to

operate MSS earth terminals in this band, a use for which there is no current licensing

framework.

ViaSat is not simply seeking to use a non-conforming FSS antenna to provide otherwise

permissible service in the band, it is seeking to use a fundamentally non-compliant antenna for a

non-conforming purpose. There is no basis for ViaSat’s implicit assertion that the licensing

framework created for FSS implementations in the Ka-band is equally applicable to its sui

generis AMSS application. ViaSat is not an applicant seeking to offer an allocated primary

service, but one requesting authority to operate solely on a non-interference-protected, non-

harmful-interference basis outside the scope of the Commission’s Rules.6 There is therefore no

basis for it to be granted spectrum access on the very same terms as a bona fide primary service

applicant. Instead, ViaSat has an affirmative obligation to demonstrate that it will not cause

harmful interference to other spectrum users.

This obligation is amplified by the fact that the ViaSat Application is the very first such

request that seeks to use Ka-band spectrum for an MSS-type network. ViaSat therefore must be

5
See, e.g., 47 C.F.R. § 25.138 (“Blanket Licensing provisions of GSO FSS Earth Stations in the
18.3 to 18.8 GHz (space-to-Earth), 19.7-20.2 GHz (space-to-Earth), 28.35-28.6 GHz (Earth-to-
space), and 29.25-30.0 GHz (Earth-to-space) bands”). Throughout this rule, the services covered
are referred to as “GSO FSS.”
6
See Ex Parte Letter from John P. Janka and Elizabeth R. Park, Counsel to ViaSat, to Marlene
H. Dortch, Secretary, FCC, File Nos. SES-LIC-20120427-00404 and SES-STA-20120815-
00751, at 1 (filed December 10, 2012) (“ViaSat 12/10 Ex Parte Letter”) (“As there is currently
no designation for aeronautical mobile use of the Ka-band in the Commission’s rules, ViaSat has
sought a waiver of the Commission’s rules to allow the proposed operations. Thus, ViaSat
respectfully requests that the Commission grant authority for the proposed operations on a non-
conforming, non-interference basis”).

-5-

required to provide complete technical detail in order to allow all parties concerned about AMSS

development in the Ka-band to evaluate its proposal fully. ViaSat must establish a clear

foundation for grant of its proposal, and it has failed to make such a showing in the

documentation it has filed to date.

Just prior to the placement of the ViaSat Application on Public Notice, the applicant filed

a letter with the Bureau conceding that “there is currently no designation for aeronautical mobile

use of the Ka band in the Commission’s rules,” and that it is not seeking authority to operate under

the rules, but instead requires “a waiver” permitting it to operate “on a non-conforming, non-

interference basis.”7 Accordingly, ViaSat must amend its application to make it consistent with a

request for waiver to permit non-conforming use. It must provide a technical and coordination

showing sufficient to demonstrate that it can operate successfully without causing harmful

interference.

B. The ViaSat Application is Incomplete Even under Standards Established
for Ku-band ESAA Applications.

Leaving aside the absence of any service rules – particularly any technical rules – to

govern AMSS operations in the Ka-band, among the other potential issues is the fact that ViaSat

has not filed any actual evidence of completion of coordination with any of the affected GSO or

NGSO satellite networks. In the application as originally filed, ViaSat stated that its proposal

“can be coordinated with” all affected parties and that it expected “to complete the formal

coordination arrangements shortly.”8 In its subsequently-filed request for special temporary

authority, ViaSat asserted that it “has completed coordination with … all operating Ka-band

GSO satellite networks within six degrees” of each of the three satellites requested as points of

7
ViaSat 12/10 Ex Parte Letter at 1.
8
ViaSat Application, Exhibit A at 5.

-6-

communication, as well as “potentially affected Ka-band GSO satellite networks outside of the

six-degree range,” one potentially affected non-geostationary (“NGSO”) network, and the

recently launched EchoStar XVII satellite at 107.1 W.L.9 Despite these sweeping

representations, ViaSat has yet to submit any actual documentation to the FCC that memorializes

or otherwise corroborates the completion of these coordination discussions. Moreover, and as

further discussed in Section III, below, it is not clear that ViaSat has identified all “potentially

affected Ka-band GSO satellite networks outside of the six-degree range” with which it would

need to coordinate. This is so due to the fundamentally non-compliant nature of its proposed Ka-

band antenna, which has the clear potential to cause harmful interference at orbital locations well

beyond the standard twelve-degree coordination range (six degrees in each direction).

It bears noting that in the recently adopted rules governing Ku-band ESAA, the

Commission has required that applicants that do not conform fully with both the antenna

performance standards of Section 25.209 and the applicable values for off-axis EIRP must

include as part of their application statements from all target satellite operators certifying that

“the proposed operation of the ESAA has the potential to receive harmful from adjacent satellite

networks that may be unacceptable”; “that the power density levels that the ESAA applicant

provided to [each] target satellite operator are consistent with the existing coordination

agreements … [with] adjacent satellite systems within 6° of orbital separation”; and that each

“will include the power-density levels of the ESAA applicant in all future coordination

9
ViaSat Ka-band STA Request, File No. SES-STA-20120815-00751, at 1. See also Ex Parte
Letter from John P. Janka and Elizabeth R. Park, Counsel to ViaSat, to Marlene H. Dortch,
Secretary, FCC, File Nos. SES-LIC-20120427-00404 and SES-STA-20120815-00751, at 1 (filed
December 17, 2012).

-7-

agreements.”10 ViaSat has not provided such documentation, which must reasonably considered

a minimum threshold requirement given the Ku-band ESAA precedent and newly-adopted

regulations. Indeed, in the early stages of Ku-band licensing of mobile antennas, applicants were

required to submit counter-signed coordination letters evidencing the agreement of each of the

affected operators.11

C. Ka-Band AMSS Applications Present Distinct Regulatory and Policy
Issues That Ku-band ESAA Networks Do Not Implicate.

At a policy level, it is not clear, even if ViaSat is able to document coordination with

each of the current licensed operators within six degrees of its requested points of

communication in each direction, as well as those currently within the identified zone of concern

created by the outlying grating lobes (which are discussed in Section III and the attached

Technical Appendix), that ViaSat should be permitted to proceed based solely on these

coordination agreements with the relatively few current Ka-band satellite operators. The

presentation of completed coordination arrangements with all adjacent satellite operators within

six degrees of any AMSS point of communication has been for several years an accepted means

to secure licensing for this service in the Ku-band, and has been adopted as a specific provision

of the rules governing Ku-band ESAA.12 But it is not clear that this same approach is

10
See ESAA R&O and NPRM, FCC 12-161, slip op., Appendix C, Final Rules, at 81 (New Rule
47 C.F.R. § 25.227(b)(2)).
11
See, e.g., ViaSat, Inc., 22 FCC Rcd 19964, 19969 (¶ 15) & n.31 (IB/OET 2007) (discussing
Ku-band “coordination letter” signed by SES Americom, Inc. and “endorsed by” PanAmSat
Corporation), citing Letter dated April 19, 2006 from Krish Jonnalagadda, Manager of Satellite
Marketing and Development for SES Americom, and Darryl T. Hunter, Systems Engineer,
ViaSat, endorsed by Mohammed Marashi, VP of Customer Support Engineering for PanAmSat
Corporation.
12
See, e.g., Row 44, Inc., 24 FCC Rcd 3042 (Sat. Div. 2009) (“Row 44”); see also 47 C.F.R.
§ 25.227(b)(2) (Federal Register publication pending).

-9-

the reduction of grating side lobes. The optimal approach to avoid harmful impact from grating

side lobes is to employ a maximum horn pitch of one wavelength (). The ViaSat antenna

exceeds this benchmark spacing by a factor of two. For both right and left circular polarization

senses, the antenna pattern for operation at all of the measured frequencies ranging from 28.1 to

30 GHz exhibits side lobes and grating lobes that greatly exceed the co-polarization elevation

mask in Section 25.138.14 See Technical Appendix, Attached hereto, at 2-3.

ViaSat itself states that its antenna patterns show four grating lobes which are “present

for a limited range of skew angles centered around approximately 25° of skew” and notes that

the EIRP “is as much as 22 dB above the 25.138 off-axis EIRP density mask.”15 ViaSat then

provides plots of its EIRP exceedances applicable only to a limited range of skew values instead

of the full range of skew values over which the Section 25.138 limits are exceeded. The

rudimentary plot that ViaSat has supplied to indicate the scope of the grating lobe issue shows

that the EIRP exceeds the Section 25.138 benchmark for skew values well-beyond a region

centered at 25 degrees. However, no scale is provided on this plot to quantify the extent to

which the EIRP spectral density exceeds the Section 25.138 mask for all applicable skew

values.16 In the attached Technical Appendix, the limited information provided in the ViaSat

application is overlaid on a map of North America to demonstrate the potentially broad

geographic impact of these grating lobes across the middle of the continental U.S. See Technical

Appendix at 3-4. This graphic represents only the arc for one half of the skew region (the 2nd

and 4th quadrants); however, the same effect exists in the 1st and 3rd quadrants as well.

14
See ViaSat Application, Exhibit C.
15
ViaSat Application, Attachment 1, Technical Description at 7-8.
16
ViaSat Application, Attachment 1, Technical Description at 8, Figure 3.

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Accordingly, ViaSat’s claim that only the AMC-16 satellite at 85 W.L. would be

affected by these grating lobes17 is both undemonstrated and inherently questionable. Indeed, as

noted in the attached Technical Appendix, it can be inferred from the ViaSat Application itself

that the skew angle range for which grating lobes point to the geostationary arc ranges from at

least 22 degrees to 31 degrees, given the fact that ordinary skew angles are exacerbated by

typical aircraft pitch and roll.18 Within a large geographical area of the U.S., these grating lobes

point to the GSO arc, with an affected orbital range extending from 76 W.L. to 90 W.L., at a

minimum. If geometrical considerations are included, this range of impact is likely extended

from at least 70 W.L. to 95 W.L, and potentially over an even wider area, resulting in at least

the potential for harmful interference throughout the continental U.S. See Technical Appendix

at 4.

ViaSat also states that its positioner tracking accuracy has a one sigma (RMS) value of

0.09 degrees in azimuth and 0.45 degrees in elevation. See ViaSat Application, Attachment 1

at 6. A reasonable estimate of the accuracy along the geostationary arc can be computed in terms

of the skew angle alpha. For example, the accuracy along the geostationary arc for a skew angle

equal to 30 degrees is estimated to be 0.3 degrees, resulting in a three sigma error of 0.9 degrees.

If the skew angle is 50 degrees, the one sigma and three sigma errors are 0.4 and 1.2 degrees,

respectively. ViaSat, however, assumes away these variations, treating azimuth error alone as

defining the predicted extent of antenna mispointing. Accordingly, the Viasat tracking error

substantially exceeds 0.2 degrees for skew values of 20 degrees and above, and is unacceptable

17
See ViaSat Application, Exhibit A at 8.
18
See ViaSat Application, Attachment 1, Technical Description at 8 (Fig. 3).

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under current standards for MSS antennas operating in FSS bands.19 Similar results are seen

with respect to maximum pointing error. See Technical Appendix at 5-7 and 11.

Added to these concerns is the fact that ViaSat cannot reasonably represent that all of the

Mantarray M40 antennas it manufactures will be uniform, such that the actual grating lobes

produced will be repeatable. There is no large-scale production experience with a machined

horn array that causes grating lobes. For this reason, it is highly unlikely that the specific lobe

patterns envisioned by ViaSat will be produced consistently in the manufacturing process.

Instead, it is virtually certain that fabrication tolerances will lead to variations that produce

substantially different antenna patterns from different production units. This varying

performance among antennas would preempt any means of mitigating detrimental grating lobe

effects across a network of up to 4,000 antennas. In short, repeatability in the manufacturing

process cannot be assured where the existence of grating lobes is accepted as a characteristic of

the antenna. See Technical Appendix at 8-10. It may therefore be impossible for ViaSat to

ensure that its antennas will be truly technically identical, which is a critical requirement for

blanket licensing of widely-deployed antennas.

Finally, it is specifically stated in the ViaSat Application that the proposed network

would comply with Section 25.138(a)(6) of the Commission’s Rules, which provides that “power

flux-density at the earth’s surface produced by emissions from a space station for all conditions,

including clear sky, and for all methods of modulation shall not exceed a level of -118

dBW/m2/MHz.” However, ViaSat provides no supporting documentation to justify this

assertion. See ViaSat Application, Narrative at 4. See Technical Annex at 11.

19
See, e.g., 47 C.F.R. § 25.221(a)(1)(ii) & (iii); Panasonic Avionics Corporation, 26 FCC Rcd
12557, 12570 (¶ 26(k)) (IB/OET 2011).

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IV. Conclusion

For all of the foregoing reasons, Row 44 respectfully urges the Bureau to consider the

ViaSat Application carefully, including an evaluation of the current stage of development of Ka-

band services and the potential impact of the ViaSat technical proposal upon such development,

and to require ViaSat to supplement its initial showing with additional information addressing

the deficiencies outlined herein before taking any further action on the application.

Respectfully submitted,

ROW 44, INC.

By: s/ David S. Keir
David S. Keir

Lerman Senter PLLC
2000 K Street, NW, Suite 600
Washington, DC 20006-1809
(202) 429-8970

January 11, 2013 Its Attorney

‐2‐

Figure 2 on the next page, modified from ‘Figure ‘3 of ViaSat’s Technical Description,2 illustrates
the locations of the grating lobes that exceed the Section 25.138 criteria.

ViaSat’s plots from their application (e.g., Figure 1 above) provide the off‐axis EIRP values only
for (operational) skew values of 0, 25, 60, 85 and 90 degrees. As is evident in Figure 2, a single
plot in the 25 degree skew‐range is insufficient to depict the actual skew range over which
ViaSat’s EIRP exceeds the 25.138 mask. Figure 2 provides no quantitative indication as to the
amount of exceedance for any of the skew values in that range.

As an estimate of the skew‐ranges over which the grating lobes will exceed the Section 25.138
benchmarks, solid lines are drawn tangent to the regions indicating the highest values of EIRP
exceedance. In these narrow regions alone, it is evident that the Section 25.138 limits are
significantly exceeded between skew values of 220 and 310 for positive skew values, as well as a
similar region from ‐220 to‐310 for negative values of skew.

(Note also that the left‐half of the plot even suggests that Section 25.138 exceedance occurs
across the entire range of skew values between 00and 310.)

2
See ViaSat Application, Attachment 1 at 8.

‐5‐

ViaSat’s Pointing Error Projections are Improper

ViaSat refers to an "azimuth" and an "elevation" positioning error in their Application. Below is
a reproduction of Table 3 in their Attachment 1, where ViaSat lists the antenna’s azimuth and
elevation error values associated with values of standard deviation (sigma).3 In addition, ViaSat
indicates the limits at which operation will be disabled.

1‐sigma 3‐sigma Limit

Azimuth Error Elevation Error Azimuth Error Elevation Error Azimuth Error Elevation Error

+/‐ .09 deg. +/‐ .45 deg. +/‐ .27 deg. +/‐ 1.35 deg. +/‐ .5 deg. +/‐ 1.35 deg.

When establishing the 0.5 degree ‘limit’, ViaSat treats the azimuth error as if that alone
depicted the extent of antenna ‘mispointing’. Actually, when considering the extent an
antenna points towards an unauthorized satellite, the extent of ‘mispointing’ along the GSO arc
is the appropriate consideration. Contrary to ViaSat’s implications, azimuth pointing error
values alone do not correspond to the true pointing error along the GSO arc. If ViaSat assumed
them to be, the actual pointing error may substantially exceed the 0.5 degree limit.

ViaSat’s referenced values apply only under limited circumstances. For a perfectly‐flat aircraft
at a geographic location of the same longitude as the satellite, the pointing error projected
along the GSO arc does simply correspond to the azimuth pointing error. (Likewise, for the
same circumstance, the elevation error corresponds to the pointing error perpendicular to the
GSO arc.) However, if the aircraft is not oriented in a ‘flat’ manner, or is not located at the
same longitude as the satellite, these numbers inaccurately portray the GSO arc pointing error.

The actual pointing error along the GSO arc is comprised of components from both the azimuth
and elevation pointing errors, whose respective contributions vary with skew angle. The actual
pointing error projected across the GSO arc closely follows the following equation:

PointErrorAlongGSO = AzPointError*Cos(SkewAngle)+ElPointError*Sin(SkewAngle)

The following table provides calculated values of GSO arc pointing error for the three groups of
variations in error referenced by ViaSat:

3
See ViaSat Application, Attachment 1 at 6.

‐6‐

Error Scenario Skew Angle (deg) Azimuth Error (deg) Elevation Error (deg) Max Pointing Error Across GSO
(deg)
1‐sigma 10 +/‐ .09 +/‐ .45 .17
1‐sigma 20 +/‐ .09 +/‐ .45 .24
1‐sigma 30 +/‐ .09 +/‐ .45 .30
1‐sigma 40 +/‐ .09 +/‐ .45 .36
1‐sigma 50 +/‐ .09 +/‐ .45 .40
1‐sigma 60 +/‐ .09 +/‐ .45 .43
3‐sigma 10 +/‐ .27 +/‐ 1.35 .50
3‐sigma 20 +/‐ .27 +/‐ 1.35 .72
3‐sigma 30 +/‐ .27 +/‐ 1.35 .91
3‐sigma 40 +/‐ .27 +/‐ 1.35 1.1
3‐sigma 50 +/‐ .27 +/‐ 1.35 1.2
3‐sigma 60 +/‐ .27 +/‐ 1.35 1.3
limit 10 +/‐ .50 +/‐ 1.35 .73
limit 20 +/‐ .50 +/‐ 1.35 .93
limit 30 +/‐ .50 +/‐ 1.35 1.1
limit 40 +/‐ .50 +/‐ 1.35 1.3
limit 50 +/‐ .50 +/‐ 1.35 1.4
limit 60 +/‐ .50 +/‐ 1.35 1.4

The table clearly indicates that the GSO arc pointing error under the ‘1‐sigma’ category may
exceed the 0.2 degree threshold for skew values 20 degrees and above. For the 3‐sigma
category, the 0.5 degree limit may as well be exceeded for skew values of 20 degrees and
above. ViaSat’s assumptions would not recognize these deviations.

Per the table, if ViaSat (as stated in their Application) were to simply assume 0.5 degree
azimuth error as the ‘limit’ at which to disable transmissions, the actual pointing error across
the GSO arc may be as high as 1.4 degrees before such disabling would occur. This constitutes a
significant deficiency in ViaSat’s approach, and will result in excessive radiated interference
towards an adjacent satellite for a situation where ViaSat should have otherwise disabled its
transmitter.

Figure 4, on the next page, presents a visualization of the range of skew values where the
positioning error exceeds the threshold of 0.2 degrees and the limit of 0.5 degrees.

‐8‐

The Mantarray Antenna’s Deficiencies

The size of the Mantarray horns can be expected to produce an abundance of antenna pattern
grating lobes. For a horn‐array consisting of oversized horns (i.e., horns larger than λc, where λc
is the wavelength of the transmit frequency), grating lobes levels are known to be problematic.
This is indeed the case of the ViaSat antenna, where the horns, which measure approximately
1.95 centimeters, are nearly two times λc (at 30 GHz λc = 1cm).4 This ratio of ~2 λc implies that
(1) Grating lobes will occur at frequencies > 15 GHz, and (2) Parasitic ‘higher‐order’ modes will
exist as well.5

In general, uncontrolled grating lobes may be of substantial levels. Analysis has suggested that
grating lobes may even rival the level of the antenna’s main lobe itself.

In an attempt to suppress the grating lobes at 0 degree skew, the Mantarray antenna uses an
established technique of shifting the antenna horns in the second row of the array by the width
of one‐half‐horn. If manufactured perfectly, this design would result in the absence of grating
lobes in the 0 degree skew pattern. However, even the smallest of imperfections prohibits the
existence of this perfect array. These imperfections are evident in ViaSat’s 0 degree skew plot
below, where 1st order grating lobes are clearly present (at approximately each of +/‐ 17 deg.,
+/‐ 32 deg., and +/‐ 54 deg.). As is obvious, even though the Mantarray design attempts to
eliminate them, the lobes are indeed present, and even at ~+/‐ 32 degrees violate the FCC EIRP
mask significantly.

4
Cf. ViaSat Application, Attachment 1 at 5.
5
Grating lobes may be described in terms of ‘orders’. A given ‘order’ refers to a group of lobes
predicted to occur by mathematical analysis of a given antenna design.

‐ 10 ‐

transmit signal to be scattered back to the aperture, thereby further‐disturbing the radiation
pattern. In advanced antenna arrays which, unlike ViaSat, utilize horn spacings less than λc, the
lobe levels will change less than 0.1 dB.

In addition to the unit‐to‐unit repeatability, the effects of aging and varying environmental
conditions on such an array is unknown. For the same, aforementioned reasons relating to
structural tolerances, this is also a concern. (For example, low frequency vibration is suspected
to influence the amplitude of the grating lobes.)

Beyond this, the operation of an antenna such as the Mantarray (i.e., having been intentionally
constructed in a manner permitting high‐level grating lobes) is without precedent. The rules for
both FCC and ITU coordination were not established to facilitate the use of antennas with
mask‐exceeding lobes. The FCC has never licensed such antennas. As well, the ITU framework
was not established to permit them.7

The detriment of this ‘lack of precedence’ extends even beyond the FCC and ITU regulatory
framework. Existing satellite service providers will likely be unfamiliar with such designs and
the associated detriment, and may be unable to gauge the resulting interference to their
operations, thereby exposing their networks to interference risk.

ViaSat’s reference to Report ITU‐R S.2223 is also misleading (see ViaSat Application, Exhibit A,
Sec. III.A. at 6). ITU‐R S.2223 states that the off‐axis e.i.r.p. levels shall be in conformance with
Recommendation ITU‐R S.524‐9, “or with any other limits coordinated with neighboring
satellite networks.” Rep. ITU‐R S.2223, Sec.3.1 at 2. The use of the term “neighboring satellite
networks” indicates that this report assumes regular antenna patterns as defined, for example,
in Recommendation ITU‐R S.580‐6.

Required Information Omitted from ViaSat’s Application

There is additional information that remains missing from the ViaSat Application relating to:

1. Antenna Control Unit (ACU) tracking performance
2. Compliance with Power Flux Density at the Earth’s surface

7
In the ITU framework the EIRP spectral density has to be reduced such that the grating lobes are
below the mask. Cf. Rec. ITU‐R S.524‐9. In the case of Viasat this means that the max EIRP spectral
density had to be reduced by approximately 15 dB (i.e from about 30 dBW/40kHz to about 15
dBW/40kHz).

‐ 11 ‐

Antenna Control Unit tracking performance

ViaSat has neglected to demonstrate that its proposed system could operate with the
significant pitch, yaw and roll of flight without causing harmful interference into adjacent
satellite operations. It has also not offered any data that demonstrates the ability to comply
with peak antenna pointing accuracy of 0.2 degrees and to cease transmission within 100 msec
once its antenna is mispointed by more than 0.5 degrees.8 Compliance requires measured data
be obtained under a variety of conditions. For example with a stationary aircraft, the antenna
shall begin its pointing with 0 degrees elevation, 0 degrees azimuth and instructed to ‘point’ to
a satellite with a specified velocity and acceleration. Satellite tracking should be ascertained for
cases that include: 1) tracking a satellite of a constant elevation angle, and a varying azimuth
angle, 2) tracking a satellite of a constant azimuth angle, and a varying elevation angle, 3)
tracking a satellite of a varying elevation and a varying azimuth angle, 4) tracking a satellite
during routine aircraft flight, 5) tracking a satellite during aircraft banking and 6) tracking a
satellite during aircraft taxiing. Data obtained under these conditions would be important to
demonstrate ACU tracking performance with the Mantarray antenna.

Compliance with Power Flux Density at the Earth’s surface

FCC requirements in Section 25.138(a)(6), which are the only established parameters for
operation of Ka‐band GSO satellite networks, state that the power flux‐density at the earth’s
surface produced by emissions from a space station for all conditions, including clear sky, and
for all methods of modulation shall not exceed a level of ‐118 dBW/m2/MHz. Verification of this
requirement ordinarily requires measurements of the fuselage attenuation. When the ViaSat
antenna is pointed toward at its intended satellite, the combination of fuselage attenuation and
attenuation from the aircraft antenna sidelobes are introduced in the computation. ViaSat has
neglected to provide any supporting documentation that it complies with this requirement.9

8
Cf. ViaSat Application, Attachment 1 at 5‐6.
9
Cf. ViaSat Application, Exhibit A at 4.

CERTIFICATE OF SERVICE

I, Sharon A. Krantzman, do hereby certify that on this 11th day of January 2013, I sent
a copy of the foregoing “Comments of Row 44, Inc” via first-class mail to:

Daryl T. Hunter
ViaSat, Inc
6155 El Camino Real
Carlsbad, CA 92009

John P. Janka
Elizabeth R. Park
555 Eleventh Street, N.W.
Suite 1000
Washington, D.C. 20004

s/ Sharon A. Krantzman
Sharon A. Krantzman

Document Created: 2013-01-11 21:15:54
Document Modified: 2013-01-11 21:15:54

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