Sec.  25.213   Inter-Service coordination requirements for the 1.6/2.4 GHz
mobile-satellite service.

   (a) Protection of the radio astronomy service in the 1610.6–1613.8 MHz band
   against interference from 1.6/2.4 GHz Mobile-Satellite Service systems.

   (1) Protection zones. All 1.6/2.4 GHz Mobile Satellite Service systems shall
   be capable of determining the position of the user transceivers accessing
   the space segment through either internal radiodetermination calculations or
   external sources such as LORAN-C or the Global Positioning System. During
   periods of radio astronomy observations, land mobile earth stations shall
   not operate when located within geographic protection zones defined by the
   radio observatory coordinates and separation distances as follows:

   (i) In the band 1610.6–1613.8 MHz, within a 160 km radius of the following
   radio astronomy sites:
         Observatory        Latitude (DMS) Longitude (DMS)
   Arecibo, PR                    18 20 46        66 45 11
   Green Bank Telescope, WV       38 25 59        79 50 24
                                  38 26 09        79 49 42
   Very Large Array, NM           34 04 43       107 37 04
   Owens Valley, CA               37 13 54       118 17 36
   Ohio State, OH                 40 15 06        83 02 54

   (ii) In the band 1610.6–1613.8 MHz, within a 50 km radius of the following
   sites:
     Observatory    Latitude (DMS) Longitude (DMS)
   Pile Town, NM          34 18 04       108 07 07
   Los Alamos, NM         35 46 30       106 14 42
   Kitt Peak, AZ          31 57 22       111 36 42
   Ft. Davis, TX          30 38 06       103 56 39
   N. Liberty, IA         41 46 17        91 34 26
   Brewster, WA           48 07 53       119 40 55
   Owens Valley, CA       37 13 54       118 16 34
   St. Croix, VI          17 45 31        64 35 03
   Mauna Kea, HI          19 48 16       155 27 29
   Hancock, NH            42 56 01        71 59 12

   (iii) Out-of-band emissions of a mobile earth station licensed to operate
   within the 1610.0–1626.5 MHz band shall be attenuated so that the power flux
   density it produces in the 1610.6–1613.8 MHz band at any radio astronomy
   site listed in paragraph (a)(1) (i) or (ii) of this section shall not exceed
   the emissions of a mobile earth station operating within the 1610.6–1613.8
   MHz band at the edge of the protection zone applicable for that site. As an
   alternative, a mobile earth station shall not operate during radio astronomy
   observations within the 1613.8–1615.8 MHz band within 100 km of the radio
   astronomy sites listed in paragraph (a)(1)(i) of this section, and within 30
   km of the sites listed in paragraph (a)(1)(ii) of this section, there being
   no restriction on a mobile earth station operating within the 1615.8–1626.5
   MHz band.

   (iv) For airborne mobile earth stations operating in the 1610.0–1626.5 MHz
   band, the separation distance shall be the larger of the distances specified
   in paragraph (a)(1) (i), (ii) or (iii) of this section, as applicable, or
   the distance, d, as given by the formula:

   d (km) = 4.1 square root of (h)

   where h is the altitude of the aircraft in meters above ground level.

   (v) Smaller geographic protection zones may be used in lieu of the areas
   specified in paragraphs (a)(1) (i), (ii), (iii), and (iv) of this section if
   agreed to by the Mobile-Satellite Service licensee and the Electromagnetic
   Spectrum Management Unit (ESMU), National Science Foundation, Washington,
   D.C.  upon a showing by the Mobile-Satellite Service licensee that the
   operation of a mobile earth station will not cause harmful interference to a
   radio astronomy observatory during periods of observation.

   (vi) The ESMU shall notify Mobile-Satellite Service space station licensees
   authorized to operate mobile earth terminals in the 1610.0–1626.5 MHz band
   of periods of radio astronomy observations. The mobile-satellite systems
   shall be capable of terminating operations within the frequency bands and
   protection zones specified in paragraphs (a)(1) (i) through (iv) of this
   section, as applicable, after the first position fix of the mobile earth
   terminal either prior to transmission or, based upon its location within the
   protection zone at the time of initial transmission of the mobile earth
   terminal. Once the mobile-satellite system determines that a mobile earth
   terminal is located within an RAS protection zone, the mobile-satellite
   system shall immediately initiate procedures to relocate the mobile earth
   terminal operations to a non-RAS frequency.

   (vii)  A  beacon-actuated protection zone may be used in lieu of fixed
   protection zones in the 1610.6–1613.8 MHz band if a coordination agreement
   is reached between a mobile-satellite system licensee and the ESMU on the
   specifics of beacon operations.

   (viii) Additional radio astronomy sites, not located within 100 miles of the
   100 most populous urbanized areas as defined by the United States Census
   Bureau at the time, may be afforded similar protection one year after notice
   to the mobile-satellite system licensees by issuance of a public notice by
   the Commission.

   (2)  Mobile-Satellite  Service  space  stations  transmitting  in  the
   1613.8–1626.5 MHz band shall take whatever steps necessary to avoid causing
   harmful interference to the radio astronomy facilities listed in paragraphs
   (a)(1)(i) and (ii) of this section during periods of observation.

   (3) Mobile-Satellite Service space stations operating in the 2483.5–2500 MHz
   frequency band shall limit spurious emission levels in the 4990–5000 MHz
   band so as not to exceed −241 dB (W/m^2 /Hz) at the surface of the Earth.

   (4)  The Radioastronomy Service shall avoid scheduling radio astronomy
   observations during peak MSS/RDSS traffic periods to the greatest extent
   practicable.

   (b) If a Mobile-Satellite Service space station operator in the 2496–2500
   MHz band intends to operate at powers levels that exceed the PFD limits in
    Sec. 25.208(v), or if actual operations routinely exceed these PFD limits, we
   require the Mobile-Satellite Service operator to receive approval from each
   operational BRS system in the affected geographical region.

   [ 59 FR 53329 , Oct. 21, 1994, as amended at  61 FR 9945 , Mar. 12, 1996;  67 FR 61816 , Oct. 2, 2002;  71 FR 35188 , June 19, 2006]