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NPD 8900.4D
Effective Date: April 27, 1999
Expiration Date: April 27, 2027
Printable Format (PDF)

Subject: NASA Use of Global Positioning System Precise Positioning Service (Revalidated 2/08/22)

Responsible Office: Space Operations MD

Update to comply with 1400 Compliance, with administrative changes, and title changes.
Administrative edits made to incorporate requirements described in NPR 1400.1, NASA Directives and Charters Procedural Requirements.


a. It is NASA policy to engage with international Global Navigation Satellite System (GNSS) providers to ensure compatibility, encourage interoperability with likeminded nations, promote transparency in the provision of Positioning, Navigation, and Timing (PNT) services to support space operations and science, as described in the National Space Policy, 85 FR 81755.

b. It is NASA policy, in accordance with Space Policy Directive (SPD)-7, United States Space-Based Positioning, Navigation, and Timing Policy, to allow projects to augment Global Positioning System (GPS) signals with allied and trusted GNSS signals consistent with specific mission needs and disruption risk assessment.

c. It is NASA's policy for all new-start or newly solicited spacecraft PNT subsystems to recognize and survive potential interference to GPS signals in accordance with NASA-STD-1006, Space System Protection Standard.

d. It is NASA policy to ensure GPS equipment and its usage adheres to GPS Interface Control Documents (ICDs) and Department of Homeland Security (DHS) best practices regarding enhanced anti-jamming, anti-measurement spoofing, anti-data spoofing, and use of civil modernized GPS signals (L1C, L2C, and L5). Additional information on this subject is available in DHS Best Practices document (Attachment C).

e. It is NASA policy to request permission from the Department of Defense (DoD) to make use of the GPS Precise Positioning Service (PPS) when it has been determined that a project using GPS requires the following:

(1) PNT capabilities better than what is available with GPS civil signals and augmentations; or,

(2) PPS-capable GPS receivers with established flight heritage and high reliability; or,

(3) Protection against intentional or unintentional interference of the GPS signal.


a. This NPD is applicable to NASA Headquarters and NASA Centers, including Component Facilities and Technical and Service Support Centers, and the Jet Propulsion Laboratory (JPL), a Federally Funded Research and Development Center (FFRDC) as specified in the contract.

b. In this directive, all document citations are assumed to be the latest version unless otherwise noted.

c. In this directive, all mandatory actions (i.e., requirements) are denoted by statements containing the term "shall." The terms: "may" or "can" denote discretionary privilege or permission, "should" denotes a good practice and is recommended, but not required, "will" denotes expected outcome, and "are/is" denotes descriptive material.


a. The National Aeronautics and Space Act, as amended, 51 USC 20113(a).

b. Interagency Agreement (IA) between the DoD and NASA for Access to and Use of the GPS PPS, initial document established November 10, 1990, and last updated on May 4, 2017.


a. Presidential Directive. Space Policy Directive 7, United States Space-Based Positioning, Navigation, and Timing Policy, (Jan. 14, 2021).

b. NASA-STD-1006, Space System Protection Standard,).

c. Federal Communications Commission (FCC) Public Notice DA 11-498

d. Federal Communications Commission (FCC) Order 18-158


a. In accordance with Presidential Directive Space Policy Directive (SPD-7), the NASA Administrator will:

(1) In cooperation with the Secretary of Commerce, develop and provide to the Secretary of Transportation technical requirements for the use of GPS and its augmentations to support civil and commercial space systems.

(2) In cooperation with the Secretary of Defense, the Secretary of Commerce, and the Secretary of Transportation, develop requirements for GPS support of space operations and science in higher orbits within the Space Service Volume (SSV) and beyond to Cislunar space.

(3) In cooperation with the Secretary of State, the Secretary of Defense, the Secretary of Commerce, and the Secretary of Homeland Security, sustain and modernize search and rescue (SAR) and distress alert and location capabilities and programs that operate as secondary payloads on GPS satellites.

b. The Space Communications and Navigation (SCaN) Program within the Space Operations Mission Directorate (SOMD) will, in coordination with the Enterprise Protection Office, support the Office of the Administrator in the implementation of SPD-7.

c. Mission Directorate Associate Administrators or their designees are responsible for the following regarding the implementation of safeguards when using external PNT sources, such as GPS and other GNSS signals:

(1) Risk Management and mitigation of interference and/or data spoofing of GPS signals in all new-start or newly-solicited spacecraft PNT subsystems, in accordance with NASA-STD 1006 and the 85 FR 81755 of 2020.

(2) If using allied GNSS signals to augment GPS, ensure that multi-GNSS devices are designed in a manner that precludes potential degradation of essential user capabilities resulting from foreign GNSS signals in accordance with NASA-STD-1006, and that the use of those signals is authorized by U.S. law, in accordance with FCC Public Notice DA 11-498 and FCC Order 18-158 (Attachment B).

d. The Deputy Associate Administrator for the SCaN Program is responsible for the following regarding the use of GPS PPS:

(1) Acting in the capacity of the designated single focal point within NASA as specified in the IA.

(2) Advising NASA GPS PPS users on any changes in DoD operating procedures that may impact NASA projects using the GPS PPS.

(3) Maintaining a database of GPS PPS equipment across NASA Centers/facilities.

e. All NASA Centers, Component Facilities, and JPL (an FFRDC), are responsible for the following regarding the use of GPS PPS:

(1) Ensuring that requests for authorization to handle and/or transfer GPS PPS Host Application Equipment (HAE) for delivery to NASA are made to the U.S. Space Force (USSF) Space and Missile Systems Center (SMC):

Los Angeles AFB
483 N. Aviation Blvd.
El Segundo, CA 90245-2808
(inquiries: 310-524-4188)

NOTE: This organization used to be referred to as SMC/GPUM, as cited in the May 4, 2017 IA between the DoD and NASA for Access to and Use of the GPS PPS.

(2) Coordinating with the Center/facility Communication Security (COMSEC) Account Manager (CAM) in the handling of GPS PPS equipment and keying materials.

(3) Ensuring the COMSEC at Center/facilities keep a database of GPS PPS equipment and active PPS keys. This database will be provided to NASA/SCaN upon request.






NASA Use of Global Positioning System Precise Positioning Service, dated October 27, 2009.


/s/ Daniel S. Goldin,

ATTACHMENT A: Definitions

Global Navigation Satellite System (GNSS): Constellation of satellites transmitting one-way radio navigation signals to enable real-time global positioning, navigation, and timing. Typically, signals from at least four GNSS satellites are needed to determine the precise position in three dimensions plus the time. GPS is one of four GNSS currently in operation, along with GLONASS (Russia), Galileo (European Union) and BeiDou (China). Regional space-based PNT systems, such as QZSS (Japan) and NavIC (India), are considered to be a GNSS constellation even though they do not provide global coverage.

Global Positioning System (GPS): U.S. space-based PNT radio navigation system. It is owned by the U.S. Government and operated by the U.S. Space Force.

Precise Positioning Service (PPS): PPS is an encrypted service provided by way of authorized access to ranging signals broadcast at the GPS L1 and L2 frequencies. Authorized PPS users require valid cryptographic keys to access PPS.

Space Service Volume (SSV): The SSV is currently defined as the volume of space between the altitudes 3,000 and 36,000 km (GEO). Spacecraft navigation within the SSV is more challenging due to weaker signals and there not being at least four radio navigation signals available at all times.
(Note: The volume of space between the surface and 3,000 km altitude is referred to as the Terrestrial Service Volume, or TSV, where at least four radio navigation signals are available at all. Spacecraft operating below 3,000 km altitude, such as the Space Station, are in the TSV and not the SSV.)

GPS Vulnerabilities: There are a number of potential vulnerabilities in the use of GPS, and other GNSS, including interference and jamming, measurement spoofing, and data spoofing. Interference and jamming are the most common threats to a GPS receiver, and in many cases they appear as a raised noise floor and may prevent a receiver from acquiring and tracking GPS signals. Measurement spoofing is when someone secretly forces a receiver to track a deceptive signal with the objective of inducing a wrong position and/or time solution. Data spoofing is an event where there is erroneous data within the GPS navigation broadcast that ends up written in the GPS receiver’s memory.


COMSEC - Communication Security

CSV - Cislunar Service Volume

DoD - Department of Defense

DHS - Department of Homeland Security

FCC - Federal Communications Commission

GEO - Geosynchronous Orbit

GNSS - Global Navigation Satellite System

GPS - Global Positioning System

HAE - Host Application Equipment

IA - Interagency agreement

LEO - Low Earth Orbit

PNT - Positioning, Navigation, and Timing

PPS - Precise Positioning Service

SCaN - Space Communications and Navigation

SMC - Space and Missile Systems Center

SMCPC/UPD - USSF SMC Production Corps / User Products Division

SOMD - Space Operations Mission Directorate

SPD - Space Policy Directive

SSV - Space Service Volume

STD - Standard

TSV - Terrestrial Service Volume

USSF - United States Space Force

ATTACHMENT C: References

C.1 NPR 1058.1, NASA Enterprise Protection Program. June 2019.

C.2 Best Practices. Improving the Operation and Development of GPS Equipment Used by Critical Infrastructure. Department of Homeland Security. January 2017.

C.3 FCC Public Notice DA 11-498. March 15, 2011.

C.4 FCC Order 18-158. November 16, 2018.


ATTACHMENT D: Presidential Space Policy Directive (SPD)-7

D.1 NASA’s Role in U.S. Positioning, Navigation, and Timing (PNT) Policy: SPD-7 of February 14, 2021 (U.S. Space-Based PNT Policy), establishes implementation actions and guidance for U.S. space-based PNT programs and activities for U.S. national and homeland security, civil, commercial, and scientific purposes. It complements the guidance set forth in Executive Order 13905 of February 12, 2020 (Strengthening National Resilience through Responsible Use of PNT Services), and the inter-sector guidance on use of other Global Navigation Satellite Systems (GNSSs), included in the December 9, 2020, National Space Policy. This policy supersedes National Security Presidential Directive-39 (NSPD-39) of December 15, 2004 (U.S) Space-Based PNT).

D.2 SPD-7 acknowledges that applications for GPS now extend beyond Earth. The Terrestrial Service Volume (TSV) of GPS, defined as the volume of space between the ground up to an altitude of 3,000 kilometers, has become an integral component for space launch operations and spacecraft in Low Earth Orbit (LEO). Use of GPS is expanding into the SSV, which extends from 3,000 km altitude in LEO to Geosynchronous Orbit (GEO), despite reduced geometric diversity and lower received signal power. Satellites rely on GPS for navigation, attitude control, space situational awareness, and new space science applications such as radio occultation. Consistent with Space Policy Directive-1 (SPD-1) of December 11, 2017 (Reinvigorating American's Human Space Exploration Program) and Space Policy Directive-3 (SPD-3) of June 18, 2018 (National Space Traffic Management Policy), PNT services will also play an important role in space traffic management and future applications in the Cislunar Service Volume (CSV), which extends from GEO to the Moon. For requirements necessary to support these emerging applications, agencies should coordinate through standard GPS requirements processes.

D.3 The 85 FR 81755 of 2020 directs the U.S. to engage with international GNSS providers to ensure compatibility, encourage interoperability with likeminded nations, promote transparency in civil service provision, and enable market access for U.S. industry. The policy also states that the U.S. will allow for the continued use of allied and other trusted international PNT services in conjunction with GPS in a manner that ensures the resilience of PNT services and is consistent with applicable law. This is also reflected in SPD-7, which allows for allied foreign GNSS to complement civil GPS service. U.S. receiver manufacturers will continue to improve security, integrity, and resilience in the face of growing cyber threats. Thus, incorporation of foreign PNT in multi-constellation devices should be designed in a manner that precludes potential degradation of essential user capabilities resulting from foreign GNSS signals.


This document does not bind the public, except as authorized by law or as incorporated into a contract. This document is uncontrolled when printed. Check the NASA Online Directives Information System (NODIS) Library to verify that this is the correct version before use: https://nodis3.gsfc.nasa.gov.