# A Framework for Assessing the Interference from NGSO Satellite Systems to a Radio Astronomy System
## 1 Introduction  
Low earth orbit (LEO) constellations will be an integral part of 6G technology [1; 2; 3; 4]. However, the increasing number of non-geostationary orbit (NGSO) satellite constellations has raised concerns about interference with other services such as geostationary orbit (GSO) fixed and mobile satellite services [5; 6; 7], ground-based services, and radio astronomy services. To avoid the negative impact of NGSO systems on radio astronomy services (RASs) [8; 9; 10], it is necessary to evaluate the interference of NGSO systems on radio astronomy telescopes, given that NGSO satellite systems often have frequency assignments that are adjacent to those of RASs. Interference analysis has become a crucial aspect of the design of satellite constellation systems. As communication technology has advanced, the speed and coverage of connections have greatly improved. However, there are still many parts of the world that do not have network coverage. To address this demand for communication, a number of operators and emerging technology companies are working to design and build large-scale NGSO communication constellations [11; 12; 13; 14] in the Ku, Ka, and Q/V frequency bands. These constellations aim to provide connectivity to areas that currently lack coverage. To protect RASs from the interference of NGSO satellite systems with adjacent frequency bands, the International Telecommunication Union (ITU) has advocated to achieve the coexistence between them in Radio Regulations [15] and established limits on the allowable interference. To comply with these constraints, it is necessary to implement interference avoidance techniques such as steeper filters to reduce out-of-band emissions, improve power amplifiers to reduce the impact of third-order intermodulation, increaseguard bands, and more effective beam scheduling strategies [16; 17; 18; 19; 20]. These measures can help reduce the interference caused by NGSO satellite systems to RASs. To determine whether NGSO systems cause harmful interference to RASs, the ITU has developed several recommendations that outline protection criteria and allowable levels of interference. These recommendations include ITU Rec. RA.769-2 [21], which outlines thresholds for tolerated interference in different frequency bands for both continuum and spectral line observations by RASs; ITU Rec. RA.1513-2 [22], which describes the percentage of data loss that is allowable for RASs, including data loss caused by a single NGSO satellite system and multiple NGSO satellite systems; and ITU Rec. S.1586-1 [23], which outlines methods for calculating interference to RASs from NGSO fixed operational systems. Additionally, ITU Rec. RA.1631 [24] provides models of receiving antennas for different RAS frequency bands for compatibility analysis. In Ref. [10], the interference of NGSO systems to RASs in the 1610 MHz band was analysed, and in Ref. [9], [PERSON] proposed a new paradigm for combining NGSO satellite systems with RASs in order to address the conflict between the large scale of NGSO satellite systems and the high performance requirements of RASs. In Ref. [8], the interference of OneWeb and GSO satellite systems with LEO-satellite-based RASs was analysed. The constantly changing positions of NGSO constellations relative to the Earth's surface, coupled with the constantly changing beam pointing of user beams within their coverage areas, make it difficult to characterize the radio frequency interference of NGSO satellite systems in RASs. Additionally, the presence of multiple NGSO satellite systems on a global scale further complicates the analysis of aggregate interference in RAS. These factors make it challenging to accurately assess the impact of NGSO satellite systems on RASs. This paper conducts a thorough study of the interference problem of NGSO constellations on RASs and develops a mathematical model and framework for analysing the interference between NGSO constellations and RASs.