On February 1, 2002, Chinese astronomer Zhang Daqing from Kaifeng discovered a new comet in the constellation Cetus, and reported it to the IAU. He found that Japanese astronomer Kaoru Ikeya had discovered it earlier than him, as the time of sunset is earlier than China. According to tradition, since they discovered the new comet independently, the comet was named after both of them. The comet was initially designated as C/2002 C1 (Ikeya-Zhang).
The comet passed perihelion on March 18, 2002, and with apparent magnitude 3.5, it became the brightest comet since 1997. The orbital period was calculated as 366.51 years. A bright comet had been recorded by Chinese astronomers in 1661, 341 years earlier, and confirmed comet Ikeya-Zhang was the return of the 1661 comet recorded by Chinese. The permanent designation "153P" was given to the comet, and it is the periodic comet with the longest known orbital period.