Fengyun-1C Debris Cloud Evolution Over One Decade

Over a decade ago, on 11 January 2007, the People's Republic of China (PRC) conducted an anti-satellite (ASAT) test destroying their aging weather satellite Fengyun-1C. The satellite had been launched on 10 May 1999 and was in a sun-synchronous orbit at an altitude of 850 kilometers and an inclination of 98.8 degrees. The ASAT kinetic-kill vehicle struck Fengyun-1C head-on (from the satellite's anti-velocity direction) at a closing velocity of 8 km/sec. The resulting collision produced a debris cloud of over four-thousand trackable (approximately ten centimeters or larger) objects with an estimated forty thousand smaller (down to one centimeter) untrackable object polluting the most valuable and highly populated low-altitude orbital regime for the foreseeable future. Some analyses have suggested that this debris has increased the object density in the sun-synchronous orbital regime above the criteria for the Kessler Syndrome, i.e., the density at which a cascade of continuing collisions and additional debris generation will ensue.

In the eleven plus years since the event, the United States Space Surveillance Network (SSN) has continued to regularly track the Fengyun-1C debris objects deleting some objects, mostly due to atmospheric re-entry, and adding others as they are detected and verified. As of early 2018, the number of cataloged objects associated with the event was 2,392. As disruptive as the PRC ASAT test was, it provides a unique opportunity to study the evolution of debris clouds. The shear number of objects with over a decade of frequent tracking provides the basis for data-rich, real-life case studies.

A brief analysis of the early Gabbard diagrams building on that performed shortly after the event (Johnson, et al., 2007) was done to re-examine the characterization of the initial collision. Additions and deletions of these debris objects to the catalog as a function of time are analyzed. Examination of the Gabbard diagrams over the years since the event show the continuing decrease in the apogee heights and eccentricities of the objects with lower perigees due to atmospheric drag while objects with perigees at or above the original Fengyun-1C altitude show much less orbital changes as would be expected. A more detailed analysis of selected individual objects that deviated from the general behavior is examined as a possible indication of unusually low or high area-to-mass ratios. Some objects added to catalog after the event are examined as potential collision products, although improved SSN tracking may be the most likely explanation. This study is based on analysis of the element sets published in the Space Track Catalog which provides a reasonable orbital state at the epoch time satisfying the stated SSN requirements and supporting long-term trend determinations.