ECSS-E-40 PART 2B, SPACE ENGINEERING SOFTWARE - PART 2: DOCUMENT REQUIREMENTS DEFINITIONS (DRDS) (31 MAR 2005). Part 2 of ECSS-E-40 “Space engineering-Software” defines the content of the document requirements definitions (DRDs) for space software product, in order to organize into documents all the expected outputs of the requirements contained in of ECSS--E--40 Part 1 “Space engineering -- Software” and in ECSS--Q--80 “Space product assurance -- Software product assurance”.