LET Ahead Level 1 public masks.
The masks files define which species/energy combinations are not reliable.
For each row:
	The timestamp in column 1 is the END of the period
	for which the masks file in column 2 applies.
BEGIN
2007-03-29T19:58:29.125	LET_Level1_masks_ahead_000.txt
2011-03-09T07:19:00.000	LET_Level1_masks_ahead_001.txt
2011-03-10T03:30:00.000	LET_Level1_masks_ahead_d12.txt
2011-03-21T03:43:00.000	LET_Level1_masks_ahead_001.txt
2011-03-22T08:49:00.000	LET_Level1_masks_ahead_d12.txt
2011-03-22T16:17:00.000	LET_Level1_masks_ahead_d03.txt
2011-03-22T18:18:00.000	LET_Level1_masks_ahead_d12.txt
2011-03-22T19:41:00.000	LET_Level1_masks_ahead_d03.txt
2011-03-23T08:12:00.000	LET_Level1_masks_ahead_d12.txt
2011-06-04T16:45:00.000	LET_Level1_masks_ahead_001.txt
2011-06-08T12:27:00.000	LET_Level1_masks_ahead_bad.txt
2011-06-27T13:48:00.000	LET_Level1_masks_ahead_001.txt
2011-06-27T20:41:00.000	LET_Level1_masks_ahead_bad.txt
2011-09-19T15:39:00.000	LET_Level1_masks_ahead_001.txt
2011-09-21T16:12:00.000	LET_Level1_masks_ahead_bad.txt
2011-09-24T05:08:00.000	LET_Level1_masks_ahead_001.txt
2011-09-24T08:56:00.000	LET_Level1_masks_ahead_d12.txt
2011-10-13T15:15:00.000	LET_Level1_masks_ahead_001.txt
2011-10-14T19:53:00.000	LET_Level1_masks_ahead_bad.txt
2012-04-16T15:02:02.500	LET_Level1_masks_ahead_001.txt
2037-01-01T00:00:00.000	LET_Level1_masks_ahead_001.txt
ENDENDENDENDENDENDENDEN	ENDENDENDENDENDENDENDENDENDENDEN