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Space traffic is considered a complex contemporary issue originated from the difficulty inherited in the nature of space missions. Satellites and space objects are actively tracked using Earth-based surveillance networks or in-situ sensors like the GPS. The data collected from these Earth-based surveillance networks albeit their public availability, they remain only valuable for trajectory and state verification due to their limited positional accuracy. This is exhibited in the poor accuracy (within 2–5 km) of public two-line elements (TLEs), which worsen when propagated in the future to more than tens of kilometers. Consequently, precision orbit data obtained from onboard GPS systems, are commonly used to alleviate, to a degree, the uncertainty regarding space conjunctions. However, the lack of GPS data standardization and sharing regarding critical satellite conjunctions together with the limited deployment of the GPS system onboard nano-satellites and its susceptibility to Doppler shifts in low Earth orbits, inhibits the full exploitation of the GPS system in space traffic. Targeting instant inter-satellite ranging for improving space situational awareness (SSA), this research explores the benefits of the proposed custom signature sequence to optimize a signal acquisition and detection for coherent and asynchronous synchronisation. This comes with the advantage of accurate propagation delay estimation and bias errors correction. Data sharing also becomes possible using the proposed custom direct sequence code division multiple access (DS-CDMA) and Reed-Solomon forward error correction for a future-proof inter-satellite ranging and data sharing solution. Coherent detection, acquisition and synchronisation are proposed based on data-assisted correlation which reduces the false- and miss-alarms respectively by 27% and 97%. This CDMA frame is based on orthogonal dual-channel separation which offers considerable noise and interference resilience for data recovery, in addition to precise frequency and timing errors correction during synchronisation. Results show that the ranging accuracy approaches meter-level at no expense of increased bandwidth beyond 2 MHz. Occupying the same bandwidth, the ranging resolution scales linearly with the spreading factor contributed by the Kronecker filter length. Additionally, the delay measurement solution is proven unsusceptible to the Doppler frequency errors caused by the high relative velocity between the satellites and Doppler errors within 16 kHz were corrected. Further, the coding gain increases by 16 dB compared to narrow-band communications, using CCSDS Reed-Solomon encoder coupled with data sequence spreading, offering considerable data transfer resilience in low signal-to-noise conditions. • Reduction in detection false- and miss-alarms by 27% and 97% respectively. • An up-sampling filter with orthogonal coefficients is used for spreading. • Metre-level ranging accuracy is achieved by sub-sample cross-correlation. • The cumulative propagation delay errors are calibrated by a proposed algorithm. • The use of CCSDS 131.0. B-2 increases the coding gain by 16 dB. [ABSTRACT FROM AUTHOR]

Multicellular system architectures are proposed as a solution to the problem of low reliability currently seen amongst small, low cost satellites. In a multicellular architecture, a set of independent k-out-of-n systems mimic the cells of a biological organism. In order to be beneficial, a multicellular architecture must provide more reliability per unit of overhead than traditional forms of redundancy. The overheads include power consumption, volume and mass. This paper describes the derivation of an analytical model for predicting a multicellular system's lifetime. The performance of such architectures is compared against that of several common forms of redundancy and proven to be beneficial under certain circumstances. In addition, the problem of peripheral interfaces and cross-strapping is investigated using a purpose-developed, multicellular simulation environment. Finally, two case studies are presented based on a prototype cell implementation, which demonstrate the feasibility of the proposed architecture. [ABSTRACT FROM AUTHOR]