"Presidential Policy Directive (PPD-4), 'National Space Policy of the United States of America', (Reference a) reiterates that United States national security is critically dependent upon space capabilities and this dependence will grow. Space activities are also closely linked to the operation of the United States Government's (USG) critical infrastructures and have increasingly been leveraged to satisfy national security requirements. Therefore, increased assurance and resilience are needed for the mission-essential functions of national security space systems, including their supporting infrastructure, to help protect against disruption, degradation, and destruction, whether from environmental, mechanical, electronic, or hostile means. […] The primary objective of this policy is to help ensure the success of national security missions that use space systems, by fully integrating information assurance into the planning, development, design, launch, sustained operation, and deactivation of those space systems used to collect, generate, process, store, display, or transmit national security information, as well as any supporting or related national security systems. Fully addressing information assurance is especially important for the space platform portion of space systems, since any vulnerability in them normally cannot be eliminated once launched."