Availability, maintainability, and Precision Dilution of Position (PDOP) are critical factors in satellite operations, particularly during scheduled and unscheduled maintenance cycles. In the challenging conditions of orbit, satellites are subject to a range of environmental stresses that can impact their performance and reliability over time. Effective strategies for maintainability and availability are essential to enhancing operational reliability, reducing failure rates, and extending mean time between failures. This paper presents a comparative analysis of the traditional NAVSTAR availability model, which does not account for aging, against a novel Stochastic Petri Net (SPN) model that incorporates aging effects. The proposed SPN model integrates both scheduled and unscheduled maintenance variables to assess their influence on PDOP, thereby improving signal accuracy and trilateration precision. By analyzing the interplay between satellite maintenance, aging, and PDOP, this study provides insights into optimizing satellite availability and signal integrity throughout its operational life.