Added a memo argument option

acronyms.tex

@@ -163,6 +163,8 @@ This document employs several abbreviations and acronyms to refer concisely to a
     \acro{OLDB}{Online Database}
     \acro{OoM}{Order of Magnitude}
     \acro{OpcUA}{OPC Unified Architecture}
+    \acro{OPD}{Optical Path Difference}
+    \acro{OPL}{Optical Path Length}
     \acro{OSE}{Optical Support Equipment}
     \acro{OSS}{Observer Support Software}
     \acro{PA}{Product Assurance}