Interspacecraft ranging in LISA data processing is important for reducing laser frequency noise. The researchers addressed the impact of on-board delays and ambiguities on LISA measurements. They identified four types of ranging observables and developed a three-stage fusion method to improve ranging accuracy. By calibrating on-board delays, reducing noise, and resolving ambiguities, they achieved more precise ranging estimates. Ground-based observations and TDI ranging were used to resolve PRN ranging ambiguities and estimate offsets.