Total solar irradiance observed by VIRGO between March and May 1999 (upper black curve) and reconstructed using MDI data (lower black curve). Also plotted (in gray) is the combination of magnetic reconstruction with granulation model. The sampling rate of the VIRGO data is 1 min, while the magnetic reconstruction alone is sampled each 30 min. The magnetic reconstruction and the combined reconstruction plus granulation model are shifted down by 500 ppm to facilitate the visual comparison.