Geometry of the 6 October 2022 stellar occultation by Triton. Upper panel: Dark blue lines (continued in red outside the Earth) delimit the predicted path of the Triton shadow on Earth on 6 October 2022. The shadow moves from right to left. The shadow centers (black dots) are spaced by one minute, and the larger black dot marks the geocentric closest approach near 14:39:46 UT (Table 1). Colors indicate stations at which the occultation was successfully detected. The blue arc shows the motion of the CHEOPS spacecraft during the event, while the red and green dots show Mt. Saraswati and Yanqi Lake, respectively. The white dots show the stations that were clouded out (see Table A.1). Lower panel: Reconstructed geometry of the occultation as seen in the sky plane. The J2000 celestial north (N) and east (E) directions and the scale are displayed in the upper right corner. The gray arrow near the equator shows the direction of rotation of the satellite. The (Neptune-facing) prime meridian is drawn as a thicker line than the other meridians, and the label S marks the south pole. The dotted circle indicates the layer in the Triton atmosphere that causes the half-light level (∼90 km altitude). The colored lines are the trajectories of the star relative to Triton (also known as occultation chords) as observed from various stations (see labels), and the black arrow indicates the direction of motion. The open circle is the predicted center of Triton, and the cross marks the actual center derived from the atmospheric fit. The offset between the two mainly stems from a correction of the Triton ephemeris.