NRAO-FCCLetter-DA-16

COMMENT submitted by National Radio Astronomy Observatory

Comment from National Radio Astronomy Observatory

2016-07-24

This document pretains to SAT-LOI-20160428-00041 for Letter of Intent on a Satellite Space Stations filing.

IBFS_SATLOI2016042800041_1144510

    24 July 2016 Ms. Marlene Dortch, Secretary Federal Communications Commission 445 12th Street, SW Washington, DC 20554 Re: DA16-804,  SATELLITE  POLICY  BRANCH  INFORMATION,  ONEWEB  PETITION  ACCEPTED  FOR  FILING   IBFS  FILE  NO.  SAT-­‐LOI-­‐20160428-­‐00041  and  CUT-­‐OFF  ESTABLISHED  FOR  ADDITIONAL  NGSO-­‐LIKE   SATELLITE  APPLICATIONS  ORPETITIONS  FOR  OPERATIONS  IN  THE  10.7-­‐12.7  GHz,  14.0-­‐14.5  GHz,  17.8-­‐ 18.6  GHz,  18.8-­‐19.3  GHz,  27.5-­‐28.35  GHz,  28.35-­‐29.1  GHz,  AND  29.5-­‐30.0  GHz  BANDS.     Dear Ms. Dortch: Footnote  US131  to  the  US  table  of  frequency  allocations  states  that  “In  the  band  10.7-­‐11.7  GHz  Non-­‐ geostationary  satellite  orbit  licensees  in  the  fixed-­‐satellite  service  (space-­‐to-­‐Earth),  prior  to  commencing   operations,  shall  coordinate  with  the  following  radio  astronomy  observatories  to  achieve  a  mutually   acceptable  agreement  regarding  the  protection  of  the  radio  telescope  facilities  operating  in  the  band   10.6-­‐10.7  GHz:”  The  list  of  observatories  that  follows  in  US131  includes  the  GBT,  VLA  and  VLBA  that  are   operated  by  the National Radio Astronomy Observatory (NRAO or “the Observatory”), and the Arecibo Observatory. Coordination is needed because the spectrum band at 10.68 GHz – 10.70 GHz is a passive service band, protected domestically by footnote US246 to the US Table of frequency allocations and by RR No. 5.340 worldwide. As such, the band is used by radio astronomy and other passive services to observe phenomena that are uniquely accessible in portions of the spectrum that are especially radio quiet. Radio telescopes are especially vulnerable to interference from airborne and satellite transmissions, and OneWeb and other systems should not operate in the band immediately above 10.70 GHz without a robust demonstration that they can, in the aggregate, fully protect radio astronomy from their unwanted emissions into the passive band. From the OneWeb filings one learns that the ground level power flux density will not exceed -146 dB W/m2/4 kHz, equivalent to -182 dB W/m2/Hz. However, from Table 1 of ITU-R Recommendation RA. 769, one finds that the threshold for detrimental interference to radio astronomy operating at 10.65 GHz is -240 dB W/m2/Hz, some 58 dB smaller. Preventing data loss to radio astronomy at 10.68 – 10.7 GHz means that unwanted emissions into the band should remain below the threshold for detrimental interference. The -58 dB margin between the radio astronomy threshold and OneWeb’s in-band signal level poses obvious questions of compatibility, which are compounded by the visibility above the horizon of hundreds of satellites (in one or more networks) which may simultaneously impact radio astronomy observing. Only a detailed epfd calculation can tell whether the proposed systems, acting separately and simultaneously, can protect radio astronomy operations. NRAO has individually had discussions with OneWeb and one of its competitors, hosted by the National Science Foundation, regarding their proposed systems. There are no generally-accepted international standards for allowing interference from unwanted emissions into passive service bands, The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.  

but during these discussions the Observatory explained the ITU-R criteria for protection of shared radio astronomy bands at a maximum level of 2% data loss from one network, or 5% from all networks in one system, as outlined in ITU-R Rec. RA. 1513 and other ITU-R Recommendations relating to epfd simulations of non-GSO systems. These criteria, which are generous from the point of view of radio astronomy in accepting data loss in passive bands where there should be none, have been used in compatibility studies at the ITU-R in regard to protection of passive service bands near 15 GHz. That said, allowing 5% data loss to radio astronomy from unwanted emissions into a passive service band would be a terrible precedent. The Observatory is awaiting the results of compatibility studies by OneWeb and its competitor. Under no conditions should these or any other satellite operators be licensed without it having been shown that they will protect radio astronomy operations in the passive service band in accordance with US131 and the relevant international requirements. Respectfully submitted Harvey S. Liszt, hliszt@nrao.edu To whom correspondence should be addressed The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.  


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