Because of laser problems and in order to extend mission lifetime, GLAS is being operated in 4-5 week-long periods about 3 times per year. The table below shows the dates of the operating periods and gives an indication of data quality for the two GLAS channels. The local ascending orbit crossing time is for the equator is shown as two numbers. The first is valid at the start of the observation period and the second at the end. Since GLAS is not in a sun-synchronous orbit, it precesses eastward about 15 degrees per month. This causes the equatorial crossing times to decrease (become earlier) by about an hour per month. The data product version number represents the software release used to process that time period and is required by the GLAS Science Product Browser to locate the proper data files for display. A version number of 'NA' means no data is available for that period.
| Date | Ascending Orbit Crossing Time (Local) | 532 nm | 1064 nm | Laser | Data Product Version |
|---|---|---|---|---|---|
| 20Feb03 - 29Mar03 | 03:20 - 02:11 | None | Excellent | 1 | 28 |
| 25Sep03 - 18Nov03 | 20:17 - 18:58 | Excellent | Excellent | 2a | 29 |
| 17Feb04 - 21Mar04 | 15:49 - 14:48 | Excellent - Good | Excellent - Good | 2b | 29 |
| 18May04 - 21Jun04 | 12:56 - 11:51 | Fair - Poor | Good - Fair | 2c | NA |
| 04Oct04 - 09Nov04 | 08:33 - 07:29 | Fair - Poor | Excellent | 3a | 28 |
| 17Feb05 - 24Mar05 | 04:09 - 03:05 | Fair - Poor | Excellent | 3b | 28 |
| 20May05 - 24Jun05 | 01:16 - 00:12 | Fair - Poor | Excellent | 3c | 28 |
| 21Oct05 - 24Nov05 | 20:22 - 19:18 | Fair - Poor | Good | 3d | 28 |
| 22Feb06 - 28Mar06 | 16:21 - 15:20 | Fair - Poor | Good | 3e | 28 |
| 24May06 - 26Jun06 | TBD | Fair - Poor | Fair | 3f | 28 |
| 01Oct06 - 26Nov06 | 13:27 - 12:26 | Fair - Poor | Fair | 3g | 28 |
| 20Feb07 - 23Mar07 | TBD | Fair - Poor | Fair | 3h | 28 |
| 20Oct07 - 23Nov07 | TBD | Fair - Poor | Fair | 3i | 28 |
| 20Feb08 - 23Mar08 | TBD | Fair - Poor | Fair | 3j | 28 |
| 06Oct08 - 19Oct08 | TBD | Poor | Poor | 3k | 29 |
| 24Nov08 - 17Dec08 | TBD | Poor | Poor | 2d | 29 |
GLAS data can be obtained from the National Snow and Ice Data
Center (NSIDC) DAAC.