Comparison of science image, difference image, and its FFT for various transient sources and contaminants in the ZTF alert stream. The full 63″ × 63″ science and difference stamps are shown, with the central 16″ × 16″ denoted in red. The FFT image stamp is cropped into the central 16 × 16 pixels. Panels (a)–(c) display astrophysical events: (a) variable star ZTF19abcqppk; (b) supernova ZTF20acogywb; and (c) asteroid ZTF18achatrx. Panel (d) shows a typical bogus event (ZTF18acgkbtq), characteristic of a bad subtraction. Panels (e)–(h) highlight different types of satellite signatures that reached the alert stream: (e) and (f), from alerts ZTF21abcjklk and ZTF21acaigul, show the typical regular glint signature with different separation among glints; (g) shows a satellite with irregular glints and an overall asymmetric signature; (h) shows a satellite with both a continuous signature and glints. This small portion of the Fourier space effectively captures the distinct extended signals of satellites.