Slat collimators defined a FOV of 3° × 30° (FWHM) for each detector; the long axes of the FOVs were perpendicular to each other. The long axes were inclined 45° to the scan direction, allowing localization of transient events to about 1°. The centers of the FOVs coincided, and were pointed 40° below the scan equator of the wheel in order to avoid scanning across the Sun.