RES157 – 252 – recognizing a) that enabling GSO networks and non-GSO systems to make the most efficient use of satellite orbits and frequency bands allocated to the FSS shall take into consideration the other services to which those frequency bands are also allocated on a primary basis; b) that the frequency bands 3 700-4 200 MHz, 4 500-4 800 MHz and 5 925-7 025 MHz are also allocated in one or more Regions to the fixed and mobile services on a primary basis; c) that in the frequency bands 3 700-4 200 MHz, 4 500-4 800 MHz and 5 925-7 025 MHz, non-GSO FSS systems are obligated by No. 22.2 not to cause unacceptable interference to or claim protection from GSO FSS networks; d) that under No. 5.458B the frequency band 6 700-7 025 MHz allocated to the FSS on a primary basis in the space-to-Earth direction is limited to feeder links for non-GSO systems of the mobile-satellite service (MSS); e) that Nos. 5.440A and 5.457C were adopted to address the operation of aeronautical mobile telemetry (AMT) for flight testing by aircraft stations (see No. 1.83) in the frequency bands 4 400-4 940 MHz and 5 925-6 700 MHz with respect to the FSS only using GSO networks; f) that there are specific protection criteria, and protection levels defined in those criteria, for the FSS, the mobile service and the fixed service; g) that new non-GSO systems with circular orbits shall ensure that existing non-GSO systems with highly-elliptical orbits should be protected, resolves to invite the ITU Radiocommunication Sector to study the following issues relating to non-GSO systems in the following frequency bands allocated to the FSS: a) in the frequency band 3 700-4 200 MHz (space-to-Earth), identification of possible revision of Article 21, Table 21-4 for non-GSO FSS satellites, with a view to enabling new non-GSO systems to operate in these FSS frequency bands, while ensuring that existing primary services, i.e. the mobile service and fixed service, are protected and maintaining the existing Article 21 pfd limits for GSO networks; b) in the frequency bands 3 700-4 200 MHz (space-to-Earth) and 5 925-6 425 MHz (Earth-to-space), the Article 22 epfd↓limits and epfd↑ limits applicable to non-GSO systems with a view to enabling additional non-GSO systems to operate in these frequency bands, while ensuring that GSO networks are protected from unacceptable interference pursuant to No. 22.2 and existing protection criteria; c) in the frequency bands 4 500-4 800 MHz (space-to-Earth) and 6 725-7 025 MHz (Earth-to-space), the possible development of Article 22 epfd↓and epfd↑ limits similar to those in other FSS frequency bands with a view to enabling non-GSO systems to operate in these frequency bands, while ensuring that GSO networks are protected from unacceptable interference pursuant to No. 22.2 and existing protection criteria taking into account recognizing f) above;