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The medium Earth orbit (MEO) based global navigation satellite system (GNSS) is susceptible to radio-frequency-interference (RFI). Therefore, the innovative concept of incorporating low Earth orbit (LEO) satellites into position, navigation, and timing (PNT) is being introduced. LEO satellites have features such as high signal strength, geometric diversity due to fast movement, and spectrum diversity. These characteristics can offer alternatives and performance improvements to existing GNSS. Therefore, various methods for PNT using LEO satellites have been proposed. In line with this, the study specifically concentrates on a dedicated LEO-PNT signal broadcasting system with the highest accuracy, aiming to provide a cost-effective local navigation signal through the LEO navigation signal generator of a 2-Unit CubeSat. Although the signal generator broadcasts the signal only over a limited target area, designing for operation with the constraints of the limited power generation, volume, and weight of the 2-Unit specification presents a challenging task. The navigation signal is designed with reference to the GPS L1 coarse/acquisition (C/A) signal and consists of three layers: carrier, pseudorandom noise (PRN) code, navigation message. S-band carrier frequency is used to minimize interference with the existing GNSS. The hardware configuration is mainly divided into clock, digital, and analog modules. An engineering model of a LEO navigation signal generator for CubeSat payload has been developed. Subsequently, the generated S-band navigation signal is analyzed spectrally and confirmed the correlation peak for the PRN code and navigation message. Prior to satellite launch, functional verification will be performed with each module of CubeSat on electric test bed, and space environment tests will be carried out for engineering model and flight model. The final mission verification is planned to be achieved by broadcasting navigation signals over South Korea and processing them at ground stations.
Jeong et al. (Wed,) studied this question.