I know you can use the mosaic to new raster tool to join two rasters together, and I want to do this for a multiple sets of rasters. I have MODIS snow cover data for 12 years and the area that the MODIS scene is covering is so big that it takes two rasters to incorporate the whole area. I need to mosaic the two rasters for each date that I have data, so I would like to write a program so I don't have to do this all manually. I have named the rasters as follows: apr001.hdf, and apr001-.hdf would be an example of two rasters from april 2000, week 1 that need to be mosaicked together. Another example would be may022.hdf and may022-.hdf for two rasters from the second week in may of 2002. I figure the program would specify if the first 6 characters of the raster name are the same then mosaic them together? Does anyone have any idea how I could go about writing a program to do this. Thanks in advance!