Trajectory of comet ISON across the SUMER FOV in the SOHO coordinate system (units of arcseconds). SOHO’s attitude is oriented toward ecliptic north. For each minute the predicted position of the central brightness is marked by a dot. The accessible FOV of SUMER – here indicated by a dashed line – refers to the central pixel of the slit. The instantaneously imaged area of 200′′× 240′′ is just inside the LASCO-C2 occulter (dash-dotted circle).