GLA08 and GLA09 were originally designed to use only the 532 nm profiles from GLA07; however, these two products use the 1064 nm channel data in addition to 532 nm. Where do the 1064 nm layers come from, and do the 532 nm and 1064 nm algorithms differ?
The GLAS science team added the 1064 nm-based layer detection just a few months before ICESat launched, because they discovered potentially serious problems in the 532 nm channel. The initial design of the software only used the 532 nm channel because of its superior data quality; however, when it became apparent that data would not be available from the 532 nm channel, the science team designed algorithms to use the 1064 nm channel for layer detection, while adhering to the original data structure for GLA08 and GLA09. This explains why these products have both 532 nm and 1064 nm layers in the same array. The 1064 nm layer heights are determined from a separate but similar algorithm to that of the 532 nm channel layer heights.