The eleven character visit_id, Attribute Value data type string enumerated Values not defined units example 80600004001 default value special processing VALUE_REQUIRED source Science Image Header software source calculation OBS_ID[2-12] DB destination ['ScienceCommon.visit_id', 'GuideStar.visit_id'] data type in DB nvarchar(11) instrument Multiple mode All product level 1a FITS hdu PRIMARY FITS header section Observation identifiers