The White House, National Space Policy of the United States of America (PPD-4) (June 28, 2010) (full-text).
This Presidential directive included the following guidance concerning GPS.
- Maintain and Enhance Space-based Positioning, Navigation, and Timing Systems. The United States must maintain its leadership in the service, provision, and use of global navigation satellite systems (GNSS). To this end, the United States shall:
- Provide continuous worldwide access, for peaceful civil uses, to the Global Positioning System (GPS) and its government-provided GPS augmentations, free of direct user charges;
- Engage with foreign GNSS providers to encourage compatibility and interoperability, promote transparency in civil service provision, and enable market access for U.S. industry;
- Operate and maintain the GPS constellation to satisfy civil and national security needs, consistent with published performance standards and interface specifications. Foreign positioning, navigation, and timing (PNT) services may be used to augment and strengthen the resiliency of GPS; and
- Invest in domestic capabilities and support international activities to detect, mitigate, and increase resiliency to harmful interference to GPS, and identify and implement, as necessary and appropriate, redundant and back-up systems or approaches for critical infrastructure, key resources, and mission-essential functions.