Trajectory segments of Helios (blue), Galileo (red), and Cassini (green) favourable for the identification of interstellar dust. The Sun is at the centre and the X–Y plane is the ecliptic plane. Vernal equinox is approximately towards the Y -direction, and the nominal interstellar dust flow direction is indicated by arrows. Different β avoidance cones are indicated by dashed lines. See text for details.