The cross calibration of SeaWiFS and MODIS using on-orbit observations of the Moon

Abstract

Observations of the Moon provide one technique for the cross calibration of Earth remote sensing instruments. Monthly lunar observations are major components of the on-orbit calibration strategies of the SeaWiFS and MODIS instruments. SeaWiFS has collected more than 132 low phase angle and 59 high phase angle lunar observations over 12 years, while Terra MODIS has collected more than 82 scheduled and 297 unscheduled lunar observations over 9 years and Aqua MODIS has collected more than 61 scheduled and 171 unscheduled lunar observations over 7 years. The NASA Ocean Biology Processing Group's Calibration and Validation Team (OBPG CVT) and the NASA MODIS Characterization Support Team (MCST) use the U.S. Geological Survey's RObotic Lunar Observatory (ROLO) photometric model of the Moon to compare these time series of lunar observations. In addition, the Moon was observed simultaneously by SeaWiFS and Terra MODIS on 14 April 2003 as part of the Earth Observing System (EOS) Lunar Calibration Experiment, allowing a direct comparison of one set of lunar measurements. The OBPG CVT and MCST use residuals of the lunar observations from the ROLO model to cross calibrate SeaWiFS and the two MODIS instruments. The cross calibration results show that Terra MODIS and Aqua MODIS agree, band-to-band, at the 1-3% level, while SeaWiFS and either MODIS instrument agree at the 3-8% level. The main implication of these cross-calibration results is that the operations concepts for upcoming remote sensing instruments should be designed to maximize the number of lunar observations over the mission time frame, while minimizing the phase angle range of the observations.