1、 Rec. ITU-R SA.1810 1 RECOMMENDATION ITU-R SA.1810 System design guidelines for Earth exploration-satellites operating in the band 8 025-8 400 MHz (Question ITU-R 139/7) (2007) Scope The use of the 8 025-8 400 MHz band by Earth exploration-satellite service (EESS) satellites operated by various enti
2、ties for data downlink operations is increasing and could result in harmful interference between these operators. Potential difficulties in sharing the heavily occupied 8 GHz spectrum may be avoided, if EESS satellite designers carefully select which of the mitigation methods are appropriate for the
3、 satellites intended operations. In addition to improving the sharing conditions for EESS satellites, many of the mitigation methods can also be beneficial in reducing or eliminating potential coordination with the extremely sensitive space research service (deep space) operating in the adjacent 8 4
4、00-8 450 MHz band. This Recommendation provides guidance in the form of a list of possible mitigation methods, shown in recommends, for consideration to reduce the potential for interference by and to EESS satellites given the growing interest in the use of the 8 025-8 400 MHz band by the EESS. The
5、ITU Radiocommunication Assembly, considering a) that Earth exploration-satellite service (EESS) satellites are an increasingly important tool for acquiring information about the Earth and its environment; b) that use of the band by EESS operated by commercial interests, governmental organizations an
6、d space agencies is increasing and could result in harmful interference among EESS systems; c) that proper selection of orbital parameters for sun-synchronous satellites can be a very effective interference mitigation technique which in general requires coordination at an early stage of system devel
7、opment; d) that homogeneity among a set of technical parameters, and in particular power flux-density (pfd) levels, will lead to a more efficient use of the orbit/spectrum resource by the EESS; e) that high-gain antennas on EESS satellites typically radiate power only towards a limited portion of th
8、e Earths surface; f) that isoflux or cardioid antennas have a more homogeneous pfd distribution across the surface of the Earth as compared to omnidirectional antennas; g) that broadcast modes generally cause higher levels of interference due to continuous transmissions and relatively high power spe
9、ctral densities but have typically lower bandwidth requirements; h) that more than 90% of all EESS satellites operate at pfd levels below 123 dB(W/m2 MHz) for high angles of arrival at the surface of the Earth; j) that proper selection of bandwidth/power efficient modulation and coding techniques co
10、uld result in smaller occupied bandwidths and lower adjacent channel interference; 2 Rec. ITU-R SA.1810 k) that higher order advanced modulation schemes, such as 16-phase PSK and above, need less bandwidth than currently used QPSK and 8-PSK but require higher pfds; l) that a number of other interfer
11、ence mitigation techniques such as polarization discrimination, earth station separation and earth station antenna discrimination may also result in lower interference levels; m) that Earth-based, receiving earth stations in the space research service (SRS) (deep-space), operated in the adjacent 8 4
12、00-8 450 MHz band, are extremely sensitive and potentially susceptible to interference from out-of-band emissions of EESS (space-to-Earth) satellite transmissions in the 8 025-8 400 MHz band; n) that time-critical events occur in both SRS (deep-space) and EESS operations; o) that most of the mitigat
13、ion techniques proposed to reduce interference between EESS data transmission links also reduce out-of-band emissions received by SRS (deep-space) stations in the adjacent 8 400-8 450 MHz band, recognizing a) that the increasing possibility of congestion in the 8 025-8 400 MHz band and requirements
14、for higher data rates will lead to increasing levels of interference; b) that guidelines for EESS (space-to-Earth) operations in the 8 025-8 400 MHz band are desirable to maximize the capacity of the band and to minimize harmful interference; c) that different mitigation methods may be required to r
15、esolve potential difficulties in the sharing of the band 8 025-8 400 MHz by different combinations of EESS systems, recommends 1 that EESS satellites operating in a non-broadcasting mode should radiate only when transmitting data to one or more earth stations; 2 that phasing of the orbital parameter
16、s for sun-synchronous satellites with existing and planned satellites should be considered; 3 that, whenever practicable, low side-lobe, high-gain satellite antennas should be used and if not practicable, isoflux antennas should be considered instead of omnidirectional antennas; 4 that broadcast mod
17、es should be avoided whenever practicable or, if unavoidable, the use of a portion of the lower half of the band 8 025-8 400 MHz be considered; 5 that bandwidth efficient modulation and coding techniques should be used to the extent practicable, to reduce the potential for adjacent channel interfere
18、nce by simultaneously limiting pfd, out-of-band emissions and occupied bandwidth; 6 that careful consideration should be given in the use of higher order advanced modulation techniques in view of potential incompatibility with a homogeneous pfd environment; 7 that, to reduce the possibility of inter
19、system interference, due consideration should also be given to other interference mitigation techniques such as polarization discrimination, geographical separation of earth stations and large earth station antennas with off-axis gains that do not exceed 32-25 log dBi for 1 48; 8 that EESS spacecraf
20、t using non-directional antennas should be designed to limit their spectral pfd on the Earths surface to less than 123 dB(W/(m2 MHz) at their sub-satellite points; Rec. ITU-R SA.1810 3 9 that, in order to minimize the need for operational coordination, EESS satellites should utilize appropriate tech
21、niques to prevent, to the extent possible, unwanted emissions exceeding the ITU-R space research service (deep-space) protection criterion1in the band 8 400-8 450 MHz, including one or more of the applicable techniques given in recommends 1 through 8, on-board filtering, large geographical separatio
22、n between EESS and space research service (deep-space) earth stations and/or low-sideband modulations; 10 that the use of the 25.5-27 GHz band by Earth exploration-satellites should be considered in particular if the techniques given in recommends 1 through 9 cannot adequately resolve potential spectrum-sharing and/or unwanted emission issues, once suitable ground infrastructures are available. 1See relevant SA-series of ITU-R Recommendations.
