To read a BSC file, use:
IDL> rd_bsc,'bsc_file_name',ss,bsc_index,bsc_data
This procedure will return the BSC index and data structures. SS is a
vector with indices of a particular subset of data within the BSC file. For
example, using SS=INDGEN(10) will extract the first 10 data sets from the
BSC file. To extract ALL the data sets, use 
.