(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.
(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 stations 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 station either prior to transmission or, based upon its location within the protection zone at the time of initial transmission of the mobile earth station. Once the Mobile-Satellite Service system determines that a mobile earth station is located within an RAS protection zone, the Mobile-Satellite Service system shall immediately initiate procedures to relocate the mobile earth station 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/m2/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 §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; 78 FR 8428, Feb. 6, 2013]
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