VIIRS On-Orbit Spatial Characterization Using the Moon

The VIIRS instrument onboard the Suomi-NPP satellite was launched in October 2011. The design and operation of its on-orbit calibration system are strongly based on MODIS heritage. However, VIIRS has no onboard calibrator similar to the spectro-radiometric calibration assembly (SRCA) on MODIS to perform the sensor on-orbit spatial characterization of band-to-band registration (BBR) and modulation transfer function (MTF). The Moon has been known as a spectrally, radiometrically, and geometrically stable source that can be used for sensor on-orbit calibration and characterization. In this letter, the algorithms developed and validated for MODIS spatial characterization using the Moon are briefly summarized and extended to VIIRS. The BBR in both along-scan and along-track directions and the MTF in the along-track direction are calculated with the scheduled VIIRS lunar observations and presented. These early results confirm that the VIIRS spatial characterization parameters have been stable since launch and are within the performance specification. The along-scan MTF cannot be accurately determined using the same algorithm and is not included in this study because the movement of the Moon in this direction is too limited to construct an edge spread function for MTF derivation. As part of the VIIRS on-orbit calibration and validation effort, the BBR and MTF parameters will be continuously monitored and evaluated throughout its mission lifetime.