1、 Rec. ITU-R RS.1261 1 RECOMMENDATION ITU-R RS.1261*, *FEASIBILITY OF SHARING BETWEEN SPACEBORNE CLOUD RADARS AND OTHER SERVICES IN THE RANGE OF 92-95 GHz (Question ITU-R 140/7) (1997) Rec. ITU-R RS.1261 The ITU Radiocommunication Assembly, considering a) that spaceborne cloud radar can determine the
2、 vertical profile of clouds and their global distribution; b) that these parameters are very important for determination of the Earths radiation budget and thereby predictions of global warming; c) that measurement of reflectivity from clouds as low as 30 dBZ is necessary; d) that scattering from cl
3、ouds at millimeter wavelengths increases approximately as the frequency raised to the fourth power; e) that worldwide, repetitive measurements of clouds require the use of spaceborne active sensors; f) that the 92-95 GHz range of frequencies would be suitable to satisfy all requirements, including b
4、andwidth requirements, for spaceborne cloud radars; g) that Recommendation ITU-R RS.577 establishes requirements for spaceborne cloud radar measurements in this frequency range; h) that, using available technology, these requirements cannot be satisfied in any frequency band currently allocated for
5、active spaceborne sensors; j) that Resolution 712 (Rev.WRC-95) of the World Radiocommunication Conference (Geneva, 1995) seeks provision of up to 1 GHz of frequency spectrum around 95 GHz for use by space-based active sensors; k) that the 92-95 GHz band is allocated to the fixed, mobile, fixed-satel
6、lite (FSS) (Earth-to-space) and radio-location services on a co-primary basis; l) that the 86-92 GHz band is allocated on a co-primary basis to passive services including radioastronomy, Earth exploration-satellite (passive) and space research (passive); m) that sharing between a spaceborne cloud ra
7、dar and other services has been studied; n) that spaceborne cloud radars would produce power flux-densities at the Earths surface in excess of the power flux-density levels likely to be imposed in frequency bands near 95 GHz allocated to the fixed and mobile services in order to protect fixed and mo
8、bile operations; o) that sharing with the FSS (Earth-to-space) is not feasible due to excessive interference to the spaceborne cloud radar; p) that the spectrum between 90 and 100 GHz contains many molecular resonances of interest to radio-astronomers; q) that co-frequency operation by spaceborne cl
9、oud radars and radioastronomy observatories could result in disruption to radioastronomy observations with a remote possibility of irreversible damage to the radioastronomy receiver; r) that current technology limits the use of filters in radioastronomy receivers to reject emissions from spaceborne
10、cloud radars; _ *This Recommendation should be brought to the attention of Radiocommunication Working Parties 4A, 7D, 8A, 8B and 9D. *Radiocommunication Study Group 7 made editorial amendments to this Recommendation. 2 Rec. ITU-R RS.1261 s) that the band 78-79 GHz is suitable for active sensor appli
11、cations in this region of the spectrum other than for cloud radars; t) that a bandwidth of 100 MHz is sufficient for use by spaceborne cloud radars; u) that methods have been identified to mitigate the potential impact to radioastronomy observations, recommends 1 that spaceborne cloud radars and fix
12、ed and mobile services not share common frequency bands; 2 that spaceborne cloud radars and the FSS (Earth-to-space) not share common frequency bands; 3 that sufficient techniques be employed in the spaceborne radar to meet the harmful interference criterion of _222 dB(W/(m2/Hz) given in Recommendat
13、ion ITU-R RA.769 to protect radioastronomy observations in the band 86-92 GHz; 4 that sharing with the radiolocation service in the frequency range of 92-95 GHz is feasible; 5 that technical and operational measures be adopted by the radioastronomy service and active sensor operators to minimize effects on radioastronomy operations; 6 that use of frequencies in the range 92-95 GHz by spaceborne active sensors be limited to spaceborne cloud radars.
