Quantifying the Impact of TLE Ageing on LEO IoT Link Reliability

Two-Line Element (TLE) sets are the ubiquitous ephemerides for propagating Low Earth Orbit (LEO) satellite trajectories. However, their predictive accuracy degrades rapidly over time, a phenomenon known as TLE ageing. For power-constrained Internet of Things (IoT) devices relying on precisely scheduled, brief communication links, this degradation leads to missed passes, severely compromising network reliability. This letter rigorously quantifies this critical effect on the Starlink constellation. By analyzing over 2.8 million pass events for 150 satellites observed from four geographically diverse ground stations, the study demonstrates that the missed-pass probability undergoes a critical transition, increasing from less than 1% to over 3% as TLE age increases from 6 to 12 hours. This establishes a critical operational requirement for TLE updates at intervals of 6 hours or less to maintain high-reliability services (e.g., >99%).