# Optimal Progressive Pitch for OneWeb Constellation with Seamless Coverage  
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23,4,* Correspondence: [EMAIL_ADDRESS] 12  
With advances in technology and lower launch costs [7], the cost of building a Mega LEO constellation will be lower. SpaceX, Oneweb, Kuiper and other companies are building their broadband LEO constellations at a rapid pace. Although the LEO satellite has the potential to play a significant role in the future network [8], there are challenges to be overcome, such as the limited orbital resources, co-frequency interference and the complexity of the resource allocation [9]. Co-frequency is an inevitable challenge as the different communication systems might share the same frequency with the LEO constellation, such as the terrestrial network and the GSO network. In addition to different communication systems and services, co-frequency interference between LEO constellations also needs to be addressed. The reasonable use of spectrum resources requires the efforts of all operators who have overlapping spectra. With the launch of a large number of spacecraft, orbital and frequency resources become very congested, making efficient use of non-renewable resources critical for the long-term exploitation of space [10]. The International Telecommunication Union (ITU) has limited the equivalent power flux density (EPFD) of non-geostationary earth orbit (NGSO) satellite systems in Article 22 of the Radio Regulations [11] to avoid unwanted interference from NGSO satellite systems to GSO satellite systems. The mitigation of large-scale LEO constellation interference to GSO satellite systems is one of the major technical concerns according to [12]. Spatial isolation [13], power control [14; 15; 16], system characteristics database, beamforming and cognitive radio [17; 18; 19; 20] are commonly used interference avoidance methods for satellite systems. The spatial isolation method includes the design of isolation zones, GSO avoidance arcs and changing satellite pointing methods [21]. The power control method can also be effective in suppressing interference with other systems. In Ref. [22], the authors introduce an adaptive power control technique for uplink and downlink scenarios to reduce inline interference between GSO and O3b satellite systems. In Ref. [23], the database approach is reviewed for the coexistence of NGSO satellite systems and other GSO satellite systems depending on the operational characteristics of the system (e.g., frequency assignment, orbital position and antenna pattern). [PERSON] et al. in Ref. [24; 25] also conducted a series of explorations of cognitive radio on the spectrum coexistence of the NGSO satellite system and GSO satellite system. A spectrum-sensing technique for the NGSO satellite system to access the GSO satellite systems' spectrum was developed in Ref. [25], which was adopted to detect whether the spectrum resource is occupied by the GSO satellite system and then to identify the specific power level used in the system. Large-scale LEO satellite constellations generally adopt the method of spatial isolation to avoid interference with GSO satellite systems. The O3b [26] satellite system adopts the equatorial circular orbit constellation in order to avoid interference with the GSO satellite system. The latitude of the O3b system earth station is not less than 10 degrees, so that the angle of the O3b and GSO satellites with respect to the earth station meets a certain threshold. The Leosat [27] satellite uses a GSO arc avoidance angle, with a minimum GSO arc avoidance angle of 7.5 degrees. The Starlink satellite uses advanced phased array technology to provide communication services to ground users in order to avoid the interference to the GSO system that mainly adopts interference avoidance techniques [28] based on isolation angle and beamforming to suppress the interference in the inline scenario.