(Translated by https://www.hiragana.jp/)

FY-1C did not maneuver

This shows the orbital period versus time for FY-1C. At the highest magnification we see a periodic change in the orbital period which is probably due to the definition of "mean elements" in the NORAD orbital model; it does not reflect meaningful changes in the spacecraft's orbit. At the more global level we see a significant change in orbital period in 2002, followed by a steady slow decline. There is no evidence for active orbital maintenance since 2002. The 2002 change could be a maneuver (perhaps to clear the original orbit to avoid collisions with FY-1D) or some kind of orbital resonance. The spike at the end of the data in 2007 is due to two post-intercept elsets which presumably refer to debris objects and should not have been assigned to FY-1C.