https://cdn.earthdata.nasa.gov/conduit/upload/5182/KeywordsCommunityGuide_Baseline_v1_SIGNED_FINAL.pdf draft 2025-07-25 https://gcmd.earthdata.nasa.gov/KeywordViewer/scheme/instruments/510a527d-1dcb-4121-8a18-ba49253453c1 SAM II Date=2025-12-08 User Id=system System Note=Added broader relation from SAM II [510a527d-1dcb-4121-8a18-ba49253453c1] to Spectrometers [055a79c7-61db-4250-abad-f1e09909f14c] Date=2025-12-08 User Id=tstevens User Note=added new Instrument keyword The Stratospheric Aerosol Measurement II (SAM II) experiment flew aboard the Nimbus-7 spacecraft and provided vertical profiles of aerosol extinction in both the Arctic and Antarctic polar regions. The SAM II data coverage began on October 29, 1978 and extended through December 18, 1993 until SAM II was no longer able to acquire the Sun. The data coverage for the Arctic region extends through January 7, 1991, and contains data gaps beginning in 1988 that increase in size each year. The data coverage for the Antarctic region is continuous through December 18, 1993 except for a time period from mid-January 1993 through October 1993. The data gaps for both the Arctic and Antarctic regions are due to an orbit degradation associated with the Nimbus-7 spacecraft. 2025-12-08T14:33:49.438Z