An association (astronomy) is a combined or co-added group of astronomical exposures from which cosmic rays have been removed. WFPC2 associations constitute one type of association and are tools in the Hubble Space Telescope (HST) archive for using data from the Wide Field and Planetary Camera 2 (WFPC2).
An assembly, in astronomy, is a combination or summation of astronomical images from which cosmic rays have been eliminated. WFPC2 assemblies are one form of such an assembly and function as resources within the Hubble Space Telescope's archive for managing Wide Field and Planetary Camera 2 (WFPC2) data.