Aircraft transmitters within sight of a deep-space earth station may cause serious interference. At maximum line-of-sight distance in any direction (391 km for an aircraft at 12 km altitude), an e.i.r.p. of — 26 dB(W/Hz) (for example, 10 dB(W/4 kHz) and 0 dBi antenna) will exceed the earth station interference limit by at least the amount shown in Table IX, assuming the reference earth station antenna pattern. Co-ordination with airborne stations is generally not practicable. TABLE IX - Interference from assumed aircraft transmitter 5.4 Potential interference to deep-space earth station receivers from near-Earth satellite transmitters An analysis of the case for satellites in highly eccentric orbits may be found in Report 688. It is concluded that sharing is not feasible. This conclusion is also valid for satellites in circular and moderately eccentric orbits. 6. Discussion Sharing with stations that are within line-of-sight (LOS) of deep-space earth stations is not feasible. Stations within LOS will create excessive interference to receivers of deep-space earth stations, or will be exposed to excessive interference from transmitters of these stations. Aeronautical mobile stations and near-Earth satellites frequently come within LOS of deep-space earth stations. Sharing of deep-space Earth-to-space bands with stations utilizing high average e.i.r.p. is not feasible because of potential interference to stations in deep-space. It is currently considered that stations with an e.i.r.p. that is more than 30 dB below the implemented or planned e.i.r.p. for space research earth stations do not pose a significant problem. From the data in [CCIR 1974-78b], this means an average e.i.r.p. no greater than 82 dBW at 2 GHz, and 92 dBW at 7 GHz. The deep-space earth station e.i.r.p. for other frequencies is not now known. 7. Conclusion Criteria and considerations presented in this Report lead to the following conclusions: 7.1 Sharing of Earth-to-space bands Deep-space research cannot share Earth-to-space bands with: — receiving aeronautical mobile stations, — receiving satellite stations, and — transmitting terrestrial stations and earth stations utilizing high average e.i.r.p., for example, transmitting transhorizon stations, and transmitting fixed-satellite earth stations. When co-ordination is practicable, sharing is feasible with other stations of all services. In some cases, co-ordination distances may be unacceptably great. 7.2 Sharing of space-to-Earth bands Deep-space research cannot share space-to-Earth bands with: — transmitting aeronautical mobile stations, and — transmitting satellite stations. When co-ordination is practicable, sharing is feasible with other stations of all services. In some cases, co-ordination distances may be unacceptably great. The matter of unacceptably long co-ordination distance requires further study. REFERENCES CCIR Documents [1974-78]: a. 2/168 (USA); b. 2/167 (USA).
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