Deciphering Solar Cycle Influence on Long-Term Orbital Deterioration of Low-Earth Orbiting Space Debris

The rapid increase in the number of space debris represents a substantial threat to the sustained viability of space operations and underscores the importance of understanding long-term drivers of orbital decay. This first of its kind study examines the long-term impact of solar activity on the orbital decay of 17 LEO debris objects across Solar Cycles 22, 23, and 24 using Two-Line Element (TLE) data spanning these three cycles. Analysis of TLE-derived decay profiles, in conjunction with sunspot numbers (SSN) and F10.7 index, reveals a threshold: orbital decay rates increase sharply when SSN exceeds approximately 67-75% of its cycle peak. This threshold corresponds to enhanced thermospheric density driven by elevated solar input, resulting in increased atmospheric drag. The orbital decay rates at the peak of each solar cycle show a progressive decline from Cycle 22 to Cycle 24, mirroring the corresponding decrease in solar activity. Decay profiles for Solar Cycle 24, predicted using ballistic coefficients derived from TLE data during Cycles 22 and 23 and atmospheric densities from the MSIS 2.0 model, show strong agreement with observations after applying a scaling factor. However, two high-inclination objects exhibited significant deviations, highlighting limitations in the MSIS model's ability to represent atmospheric conditions at high latitudes. In contrast, lower-inclination objects showed excellent correspondence. Overall, the findings confirm solar-driven thermospheric variability as the dominant factor influencing long-term orbital decay and emphasize the need to refine atmospheric models-particularly for polar regions-to improve re-entry predictions and satellite mission planning.