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The Visible Infrared Imager Radiometer Suite (VIIRS) is one of five instruments on-board the Suomi National Polarorbiting
Partnership (NPP) satellite that launched from Vandenberg Air Force Base, Calif., on Oct. 28, 2011. VIIRS has
been scheduled to view the Moon approximately monthly with a spacecraft roll maneuver after its NADIR door open on
November 21, 2012. To reduce the uncertainty of the radiometric calibration due to the view geometry, the lunar phase
angles of the scheduled lunar observations were confined in the range from -56° to -55° in the first three scheduled lunar
observations and then changed to the range from -51.5° to -50.5°, where the negative sign for the phase angles indicates
that the VIIRS views a waxing moon. Unlike the MODIS lunar observations, most scheduled VIIRS lunar views occur
on the day side of the Earth. For the safety of the instrument, the roll angles of the scheduled VIIRS lunar observations
are required to be within [-14°, 0°] and the aforementioned change of the phase angle range was aimed to further
minimize the roll angle required for each lunar observation while keeping the number of months in which the moon can
be viewed by the VIIRS instrument each year unchanged. The lunar observations can be used to identify if there is
crosstalk in VIIRS bands and to track on-orbit changes in VIIRS Reflective Solar Bands (RSB) detector gains. In this
paper, we report our results using the lunar observations to examine the on-orbit crosstalk effects among NPP VIIRS
bands, to track the VIIRS RSB gain changes in first few months on-orbit, and to compare the gain changes derived from
lunar and SD/SDSM calibration.
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