ED-243D supersedes ED-243C (2021). This document contains Minimum Operational Performance Standards (MOPS) for avionics that provide Aeronautical Mobile Satellite (R) Services (AMS(R)S) by means of satellite communications technologies scheduled to become operational in context of the global and regional ATM and CNS modernization. Each of these technologies is individually and collectively referred to as a “Next Generation Satellite System” (NGSS). In this revision the actual Inmarsat SBB & Iridium Certus MOPS material is updated with respect to SATCOM system improvements, and ATN-IPS technical material is added.