This letter investigates the synergy between the Scanning Imaging Absorption Spectrometer for Atmospheric Chartog-raphy (SCIAMACHY) and the Advanced Along Track Scanning Radiometer (AATSR) onboard the ENVISAT platform for re-flectance calibration purposes. This calibration study was mainly performed over a portion of a hurricane corresponding to fully cloudy SCIAMACHY and AATSR pixels. Results show that SCIAMACHY underestimates the top-of-atmosphere (TOA) re-flectance by up to 23% (at 870 nm) as compared to AATSR for a nadir viewing geometry. Specifically, considering AATSR calibration as accurate, which is confirmed by comparison with the Medium Resolution Imaging Spectrometer, the SCIAMACHY TOA reflectances should be multiplied by 1.21, 1.19, 1.23, and 1.10 for wavelengths at 550, 670, 870, and 1600 nm, respectively, ahead of satellite retrieval schemes based on the measurements of TOA reflectance.