Why are the 2009 images 1-band, while the other images are 3-band?
During the first campaign for this data set (2009 Antarctica), the camera was flown in a demonstration mode. Input from the science community requested that panchromatic data be collected - so as to maximize grey-level possibility. The panchromatic data are 1-band data. Most all of the 2009 imagery for Antarctica was acquired in that mode. During the other campaigns, the cameras were configured to collect data in color, which is 3-band.
There is a metadata field provided in each GeoTIFF which identifies the mode (pan or color) associated with the data.