Engineering topics
Cheung, Kar-Ming
Publications and source records attributed to Cheung, Kar-Ming.
Single-satellite doppler localization with Law of Cosines (LOC)
Modern day localization requires multiple satellites in orbits, and relies on ranging capabilities which may not be available in most proximity flight radios that are used to explore other planetary bodies such as Mars or Moon.
Navigation tracking with multiple baselines Part 1: high-level theory and system concepts
We describe a system concept that detects and locates dead and non-cooperatively spacecraft in the Geostationary Orbit (GEO). This can be done by making use of an existing GEO satellite with accurately known location as a reference, and/or by placing a dedicated “reference” spacecraft into an eccentric geosynchronous orbit over a region of interest (e.g. above North America).
Statistical optical link budget analysis
In this paper, we describe work on extending statistical analysis methods to optical communications links, with a primary focus on intensity modulated, direct detected photon-counting channel utilizing pulse-position-modulation (PPM). We performed analysis on the relationship between bit error rate (BER) requirement, statistical characteristics of the received signal power and noise power, and the coded performance curves. We presented link analysis results with preliminary uncertainty quantifications of signal power and noise power. We used the Consultative Committee for Space Data Systems (CCSDS) Serially Concatenated convolutionally coded Pulse Position Modulation (SCPPM) prototype software [1] to obtain coded performance curves under different operating conditions with varying signal power, background noise power, code rates,and PPM modulation orders. Comparison with traditional, deterministic analysis shows that extra margin needs to be reserved to compensate for the performance losses caused by uncertainties of the link parameters.