NSIDC is no longer distributing GLAS Release 31 data. GLAS Release 33 data continues to be distributed from our long term archive. Descriptions of Release 33 and Release 31 can be found on the NSIDC Data Releases and Past Data Releases Web pages. For more information about GLAS data products, see the ICESat/GLAS Data Web site. For questions and concerns, please contact NSIDC User Services.