The Almanac

Orbit Data and Resources on Active GNSS Satellites

Click to download the GPS World Almanac (PDF, January 2015 issue).

GPS Constellation


General Notes:

1. “SV Number” refers to space vehicle number. “PRN Number” refers to the satellite’s unique pseudorandom noise code.

2. Clock: Rb = rubidium; Cs = cesium.

3. “Launched” and “Usable” dates are based on Universal Time.

4. The current active GPS constellation consists of 4 Block IIA satellites, 12 Block IIRs, 7 Block IIR-Ms, and 8 Block IIFs for a total of 31 satellites and is under FOC (Full Operational Capability). The constellation is in the 24+3 (or “Expandable 24”) configuration with satellites occupying the fore and aft bifuracted slots in the B, D, and F planes. There are currently 7 reserve satellites, SVNs 27, 32, 33, 35, 36, 37, and 38, and one test satellite, 49, near slots A1, F2-F, C4, B1-F, C2, C1, A3, and B1-F, respectively. SVN35 transmitted signals as PRN03 between September 5 and October 20, 2014. The satellite was set unhealthy and not included in broadcast almanacs.

5. The Block IIF-1 through IIF-8 satellites have nicknames Polaris, Sirius, Arcturus, Vega, Canopus, Rigel, Capella, and Spica, respectively.

6. SVN35 and 36 carry onboard corner-cube reflectors for satellite laser ranging (SLR). SLR tracking of the satellites permitted analysts to differentiate between onboard clock errors and satellite ephemeris errors in GPS tracking.

7. Selective availability (SA) was set to zero on all satellites by presidential order on May 2, 2000 at approximately 4:00 UT. Previous Almanacs provide a history of SA status.

8. Antispoofing (AS) was activated on January 31, 1994, on all Block IIs. AS is occasionally off for testing and other purposes. Previous Almanacs provide a history of AS status.

9. The design life and mean-mission duration goals of the Block IIA, IIR, and IIF satellites are 7.5 and 6 years, 10 and 7.5 years, and 12 and 9.9 years, respectively.

10. GPS World believes this information to be correct as of press time. However, because of the satellite constellation’s evolving nature, readers should contact GPS information services listed on these pages for more current data.

11. Dr. Richard Langley of the University of New Brunswick provided the GPS satellite status information and compiled the notes.

Performance Notes:

A. SVN39/PRN09 was set unusable and removed from the GPS constellation on May 19, 2014. It continued to transmit L-band signals until May 27, 2014. It was then reactivated, but still set unusable, on June 13, 2014, for a rubidium clock checkout. It transmitted L-band signals until July 21, 2014.

B. SVN33/PRN03 was set unusable and removed from the GPS constellation on August 2, 2014. It is now a reserve satellite, currently located near slot C4.

C. SVN38/PRN08 was set unusable and removed from the GPS constellation on October 30, 2014. It continues to transmit signals for test purposes. Subsequently, it will become a reserve satellite, initially located near slot A3.

D. The usable date for SVN47/PRN22 has been corrected to 1-12-04.

GPS Satellite & System Information

National Executive Committee for Space-Based Positioning, Navigation & Timing

DoD GPS Operations Center and 2SOPS Constellation Status

U.S. Coast Guard Navigation Center Navigation Information Service (NIS)

GLONASS Constellation



General Notes:

1. The first GLONASS satellite was launched October 12, 1982.

2. The GLONASS numbering scheme used in this table includes the eight “dummy” satellites orbited as ballast along with “real” satellites on the first seven GLONASS launches. The second number (in parentheses) in the “GLONASS Number” column is that assigned by the Russian Space Forces.

3. The Russian Federation designated the “Kosmos Number.”

4. GLONASS numbers 1–94 have been withdrawn from service.

5. All operational satellites are GLONASS-M satellites, except GLONASS 125 and 134, which are GLONASS-K1 satellites. GLONASS 132 includes  an L3 transmitter.

6. All launch and usable dates are based on Moscow Time (Universal Time + 3 hours).

7. Almanac/slot numbers in parentheses indicate the physical orbital slot of reserve/test satellites or those in maintenance and not in the almanac.

8. Channel number “k” indicates L1 and L2
carrier frequencies: L1 = 1,602 + 0.5625 k (MHz); L2 = 1,246 + 0.4375 k (MHz).

9. All GLONASS satellites use cesium atomic clocks.

10. Twenty-four GLONASS satellites are currently set healthy.

11. The latest GLONASS launch was for GLONASS 134, which was launched from the Plesetsk Cosmodrome on November 30, 2014. It is currently drifting to its assigned orbital slot and is still undergoing checkout and is not yet operational. A GLONASS-M single-satellite launch from Plesetsk is expected in the first quarter of 2015. A GLONASS-M triple-satellite launch from Baikonur is expected in the April/May 2015 timeframe.

12. New GLONASS channel allocations were introduced September 1993 to reduce interference to radio astronomy. Note the use of the same channel on pairs of antipodal satellites.

13. GPS World believes this information to be correct as of press time. However, because of the satellite constellation’s evolving nature, we encourage readers to contact the GLONASS sources listed on these pages for more current information.

14. Information compiled by Richard Langley.

Performance Notes:

A. GLONASS 95 is a reserve satellite.

B. GLONASS 100 was operational and set healthy between February 24 and April 11, 2014, using frequency channel -6. It subsequently resumed its status as a reserve satellite.

C. Maintenance tests of GLONASS 110 were concluded on July 23, 2014, and the satellite has been removed from the constellation.

D. GLONASS 125 is currently in flight test mode and is near physical orbital slot 20. When not in the active constellation, the satellite typically identifies itself as satellite 26 in its broadcast ephemeris.

E. GLONASS 132 has a Kosmos number of 2491 assigned by the Russian Federation but NORAD is using a designation of 2492.

F. GLONASS 134 is undergoing commissioning and is not yet operational.

GLONASS System Information

The Information–Analytical Center (IAC) publishes official information about GLONASS status and plans as well as consultation, information, and scientific-method services to increase GLONASS applications efficiency. It provides current constellations, Earth maps of the current and daily navigation availabilities, results of GNSS navigation field monitoring in the Moscow area in a real-time mode, and other data. For more information: IAC, Mission Control Center, email:

Galileo Constellation



A. Navigation signals from GIOVE-A were switched off on June 30, 2012, and the satellite decommissioned for ESA use.

B. Navigation signals from GIOVE-B were switched off on July 23, 2012, and the satellite decommissioned for ESA use.

C. Nicknamed Thijs.

D. Nicknamed Natalia.

E. Nicknamed David.

F. Nicknamed Sif. Payload power problem beginning May 27, 2014. Now only transmits an E1 signal.

G. Nicknamed Doresa. Orbit perigree raised by about 3500 kilometers in November 2014. Began transmitting L-band navigation signals on November 29, 2014.

H. Nicknamed Milena.

I. System is undergoing in-orbit validation campaign. Occasional planned outages of satellite signals. Satellites are currently transmitting valid navigation messages.

J. Satellites launched into wrong orbits.

Galileo System Information

Galileo is a joint initiative of the European Commission (EC) and the European Space Agency (ESA). Initially, they formed the Galileo Joint Undertaking (GJU) to manage Galileo’s development phase. The European GNSS Supervisory Authority (GSA), initially headquartered in Brussels, Belgium, took over Galileo responsibility from GJU on January 1, 2007. The headquarters were moved to Prague in the Czech Republic on September 1, 2012.

The GSA’s tasks include management of the first series of satellites to ensure the large-scale demonstration of the capabilities and reliability of the Galileo system. The first two Galileo satellites secured the system’s frequency allocation and validate key technologies for the full Galileo constellation. Surrey Satellite Technology Ltd. (SSTL) in Guildford, United Kingdom, constructed the first test satellite. Formerly known as the Galileo System Test Bed (GSTB) V2/A satellite, it has been christened Galileo In-Orbit Validation Element-A (GIOVE-A) and was launched on December 28, 2005. The second test satellite, GSTB V2/B or GIOVE-B, constructed by a team led by Astrium GmbH (now Airbus Defence and Space) in Ottobrunn near Munich, Germany, was launched on April 26, 2008.

The first two in-orbit validation (IOV) satellites were launched on October 21, 2011, and the third and fourth IOV satellites were launched on October 12, 2012 — all provided by Astrium. The IOV satellites are currently transmitting test signals. The satellites were provided by Astrium. Transmission of valid navigation messages began on January 17, 2013. The first two full-operational-capability satellites, manufactured by OHB Systems GmbH (Bremen, Germany) and SSTL, were launched on August 22, 2014, into wrong orbits due to an upper rocket stage anomaly.

Beidou/Compass Constellation



IGSO node longitudes are nominal values. Nodes are allowed to drift ±3 degrees or so.

A. Inactive.

B. Initially achieved geostationary orbit at a longitude of about 84.5° E, but appears to have become uncontrollable shortly thereafter. Librating about the 75° E libration point.

C. GEO, formerly at 144.5° E, shifted to 140° E between about June 30 and July 9, 2011.

D. GEO, formerly at 84° E, shifted to 110.5° E between about November 7 and November 23, 2012.

E. The MEO satellites are in a 24-satellite three-orbit-plane Walker constellation with orbit planes spaced by 120°. The first four MEO satellites occupy slots 7and 8 in plane 1 and slots 3 and 4 in plane 2.

F. Satellite is not currently transmitting standard signals.

Beidou/Compass System Information

China fielded a demonstration regional satellite-based navigation system known as BeiDou (Chinese for the “Big Dipper” asterism and pronounced “bay- dough”) following a program of research and development that began in 1980. The initial constellation of three geostationary Earth orbit (GEO) satellites was completed in 2003. A fourth GEO satellite was launched in 2007. The initial regional BeiDou system (BeiDou-1) has been replaced by a global system known as BeiDou-2 (or simply BeiDou and, formerly, Compass). It will eventually include five GEO satellites, 27 medium Earth orbit (MEO) satellites, and five inclined geosynchronous orbit (IGSO) satellites. BeiDou-2 was declared operational for use in China and surrounding areas on December 27, 2011. FOC for this area was declared on December 27, 2012. The system will provide global coverage by 2020, or even as early as 2017, according to some reports.

For more information:  Official BeiDou website (English-language version).

Satellite-Based Augmentation Systems



A. Inmarsat 3-F2 began Safety-of-Life Service on March 2, 2011, and is transmitting message type 2.

B. Astra 5B was launched on March 22, 2014, and started transmitting L1 test signals on December 11, 2014.

C. Decomissioned for EGNOS use. Satellite sold to Britain’s Avanti Communications.

D. Inmarsat-4-F2 began Safety-of-Life Service on March 22, 2012, and is transmitting message type 2.

E. SES-5 (also known as Sirius 5 and Astra 4B) was launched on July 9, 2012. Satellite occasionally transmits test signals.

F. GSAT-8 was launched on May 20, 2011. Not currently transmitting signals.

G. GSAT-10 was launched on September 28, 2012.

H. GAGAN was certified for enroute navigation and non-precision approaches on December 30, 2013.

I. MSAS commissioned for aviation use on September 27, 2007. Either satellite can transmit both PRN signals if necessary.

J. QZS-1 (nicknamed Michibiki) transmits an L1 augmentation signal using PRN code 183. That signal is in test mode. Central longitude can vary by ± 5° or more from nomimal value.

K. Luch-5A was launched on December 11, 2011. Initially positioned at 58.5° E, it was shifted to 95° E between about May 30 and June 28, 2012, then shifted to 167° E between about November 30 and December 22, 2012. Transmissions as PRN 140 began on July 12, 2012. Transmitted occasional, non-coherent code/carrier test signals.

L. Luch-5B was launched on November 2, 2012, and started transmitting test signals on January 17, 2013.

M. Luch-5V was launched on April 28, 2014. Testing may have started using PRN 140, not 141.

N. Galaxy 15 ranging supports enroute through precision approach modes. Switched to backup satellite oscillator on January 6, 2012.

O. Anik F1R ranging supports enroute through precision approach modes.

P. The Galaxy 15 and and Anik F1R payloads, operated by Lockhhed Martin for the FAA, are known as LMPRS-1 and LMPRS-2, respectively.

Q. Inmarsat-4-F3 supports non-precision approach ranging service.

IRNSS Constellation

According to the Indian Space Research Organisation, the Indian Regional Navigation Satellite System (IRNSS) will consist of three GEO satellites located at 34°E, 83°E, and 131.5°E as well as two pairs of IGSO satellites with their nodes at longitudes of 55°E and 111.5°E with an orbital inclination of 29°. The satellites will transmit signals at 1176.45 and 2492.028 MHz.

The first satellite in the planned constellation, IRNSS-1A, was launched from the Satish Dhawan Space Centre on July 1, 2013, at 18:11 UTC. The satellite, with international designation 2013-034A and NORAD/JSpOC identification number 39199, achieved its assigned IGSO on July 18, 2013, with a nominal nodal longitude of 55°E and an orbital inclination of 27°. Test transmissions started shortly thereafter. The second IGSO satellite, IRNSS-1B, was launched on April 4, 2014, at 11:44 UTC. Designated as 2014-017A and 39635, it was placed in an orbit with a nominal nodal longitude of 55° E and an inclination of 31°. The first GEO satellite, IRNSS-1C, was launched on October 15, 2014, at 20:02 UTC. Designated as 2014–061A and 40269, it is in a nominally geostationary orbit with a longitude of 83° E.

For more information: 

ISRO website:

GNSS Internet Resources

United States and Canada

Canadian Space Geodesy Forum
This University of New Brunswick service presents daily GPS constellation status reports, ionospheric disturbance warnings, and news and discussion about GPS and other space-based positioning systems by way of electronic mail. Downloadable files are also available. To subscribe, e-mail the one-line message [sub CANSPACE your_name] to listserv@UNB.CA.
For more information: Terry Arsenault or Richard Langley, phone (506) 453-4698, fax (506) 453-4943, e-mail

The U.S. government provides the website to educate the public about the Global Positioning System and related topics. Information includes sections for the general public, for Congress, for international citizens, for professionals, and for students. The site is maintained by the National Coordination Office for Space-Based Positioning, Navigation, and Timing in coordination with multiple federal agencies.

DoD GPS Operations Center and 2SOPS Constellation Status
The U.S. Department of Defense (DoD) GPS Operations Center and the 2nd Space Operations Squadron (2SOPS), U.S. Air Force, maintain Internet sites for military and DoD users only; civilians are referred to the U.S. Coast Guard’s Navigation Information Service (see above). The GPS Operations Center provides DOP predictions, GPS performance assessments, anomaly impact analysis, GPS FAQs, and other services to meet the needs of GPS users in the field. 2SOPS operates a GPS Constellation Status site with scheduled outages, user advisories, almanac data, electronic mail, and downloadable files.
For more information: Military: Contact GPS Operations Center at DSN 560-2541 or Commercial (719) 567-2541, Civilians: Contact USCG Navigation Center at (703) 313-5900, Website POC, email:

National Executive Committee (EXCOM) for Space-Based Positioning, Navigation & Timing (PNT)
The EXCOM advises senior national government leadership and coordinates with federal agencies about policy matters concerning GPS, its augmentations, and related systems. The deputy secretaries of Defense and Transportation jointly chair the EXCOM. Executive Committee membership includes equivalent-level officials from NASA, the departments of State, Commerce, Homeland Security, Agriculture, Interior, and the Joint Chiefs of Staff. Components of the Executive Office of the President and other selected agencies participate as observers. The National Coordination Office, an interagency staff directed by a member of the Senior Executive Service in Washington, provides day-to-day administrative and operational support to the EXCOM. The National Space-Based PNT Advisory Board operates in an independent advisory capacity for the EXCOM as directed by the National PNT Policy and in accordance with the Federal Advisory Committee Act.
For information contact: National Coordination Office for Space-Based PNT, Herbert C. Hoover Building, Rm. 2518, 1401 Constitution Ave. NW, Washington, D.C. 20230, phone: 202-482-5809, fax: 202-482-4429, e-mail:

National Geospatial-Intelligence Agency (NGA)
Precise GPS Orbit Information and Earth Orientation Parameter Predictions (EOPP)
The NGA Global Positioning System Division/Ephemeris Support and Analysis Team maintains a World Wide Web page for Department of Defense and civilian users with precise GPS orbit and clock information based on tracking data collected from NGA, U.S. Air Force, and IGS stations. Daily and weekly precise ephemeris and clock estimate data, both center-of-mass (pedata) and antenna phase center (apcpe) are calculated on a 15-minute interval. Approximately two years of data are kept at this site with previous data available on request. NGA also offers a nine-day orbit prediction ephemeris along with a daily orbit and clock “rapid” ephemeris, also calculated on a 15-minute interval. Earth Orientation Parameter Predictions, based on data provided by the U.S. Naval Observatory, are provided. EOP coefficients and predictions, used by the Air Force GPS Operational Control Segment, are calculated each Thursday to go into effect the following Sunday through Saturday (each new GPS week). Daily EOPs are computed for testing and evaluation to be used in GPS III.
For more information: Duty hours (6 a.m.–6 p.m., Mon–Fri): 314-676-9142 or DSN 846-9142, e-mail:
24-hour contact:
314-676-9140 or DSN 846-9140.

Natural Resources Canada, Canadian Spatial Reference System
Natural Resources Canada, Canadian Geodetic Survey, operates the Canadian Active Control System (CACS), a national network of continuously operating GNSS tracking stations. Products derived from CACS include GNSS observation data, precise GNSS orbits, and precise GNSS clock corrections. The system supports the positioning requirements of a broad range of users, including the most demanding post-mission scientific applications, providing coordinates in either the Canadian Spatial Reference System (CSRS) or the International Terrestrial Reference Frame (ITRF). An online Precise Point Positioning (CSRS-PPP) service allows GPS users from around the world to recover accurate positions from a single GNSS receiver by submitting their RINEX observation data via the Internet. Information about access to CACS, data availability, and other geodetic products is available 24 hours a day from a free online subscription service (CSRS Online Database).
For more information: Contact our Geodetic Integrated Services unit, 615 Booth Street, Ottawa, Ontario, Canada K1A 0E9; phone (613) 995-4410; fax (613) 995-3215; e-mail

Scripps Orbit and Permanent Array Center (SOPAC)
GPS Orbits, Coordinate Information, and Data Archive
California Spatial Reference Center
CRTN: California Real Time Network

The Scripps Institution of Oceanography, University of California, San Diego, maintains SOPAC, which provides precise, rapid, ultra-rapid, and hourly orbits for the International GNSS Service (IGS) and NOAA’s Global Systems Division (GSD). Many GPS-related services and tools are available from SOPAC’s website such as SCOUT (a global ITRF Coordi-nates Generator), Site Information Manager (SIM), On-line Map Interface (SOMI) and GPS Explorer. SOPAC archives 24-hour RINEX data from about 3,000 continuous GPS sites from more than 20 scientific networks around the world, with a concentration in western North America. SOPAC also maintains the operational center for the California Spatial Reference Center, or CSRC. The CSRC provides California’s geodetic framework for scientific, engineering, and geographical information systems in partnership with the National Geodetic Survey. SOPAC also collects and archives high-rate (1 Hz), low latency (1 second) GPS data from stations in California. For information about access to real-time data streams, visit
For more information: Contact SOPAC, Scripps Institution of Oceanography, UCSD, IGPP 0225, 9500 Gilman Drive, La Jolla, CA 92093-0225, USA; call (858) 822-2156, fax (858) 534-9873, or e-mail or Director Yehuda Bock,

U.S. Coast Guard Navigation Center
This site offers GPS constellation status, scheduled outage updates, user advisories, and almanac data as well as Differential GPS and Coast Guard Local Notice to Mariners information.
Voice recording for GPS constellation status: (703) 313-5907.
For more information: Contact the NIS Watchstander, 24 hours a day, at phone (703) 313-5900, fax (703) 313-5920, or e-mail

U.S. National Geodetic Survey (NGS) GPS Orbit Information
NOAA’s National Geodetic Survey (NGS) manages a network of Continuously Operating Reference Stations (CORS) that provide GPS data to support three-dimensional positioning, meteorology, space weather, and geophysical applications throughout the United States, its territories, and a few foreign countries. The CORS network is a multi-purpose cooperative endeavor involving more than 200 government, academic. and private organizations. NGS partners contribute more than 1,900 independently owned and operated stations to the CORS network. The primary objective of the CORS Program is to define and maintain the National Spatial Reference System (NSRS). The CORS Program also:

  • Provides free access to GPS data from the CORS network sites.
  • Establishes coordinates and velocities of CORS stations with respect to the NSRS.
  • Enables users to determine centimeter-level positions with respect to the NSRS by simultaneously processing their own GNSS data with data from the CORS network.
  • Computes GPS satellite orbits to support post-processing applications.
  • Provides web services for post-processing GPS data via its Online Positioning User Service (OPUS).
  • Calibrates GPS antenna phase center values.
  • Establishes guidelines for operating and using active geodetic control networks.

NGS continually updates its website with new information on the CORS program.
For more information: e-mail:

U.S. Naval Observatory
The U.S. Naval Observatory (USNO) provides GPS timing data and status information.
For more information: Contact Stephen Mitchell, phone: (202) 762-1455 or DSN 762-1455, e-mail:


International GNSS Service (IGS)
IGS Data Centers

The foundation of IGS is a global network of more than 350 permanent, continuously operating, geodetic-quality GPS and GPS/GLONASS sites. The station data are archived at four global data centers and six regional data centers. Ten analysis centers regularly process the data and contribute products to the analysis center coordinator, who produces the official IGS combined orbit and clock products. Timescale, ionospheric, and tropospheric products are analogously formed by specialized coordinators for each. The IGS reference-frame coordinator determines tracking site coordinates and velocities from analysis centers’ solutions, and organizes the IGS contribution to the International Terrestrial Reference Frame (ITRF). The IGS Central Bureau is responsible for day-to-day management of the IGS, following policies set by the IGS International Governing Board as well as for communication and outreach. More than 200 institutions and organizations in more than 90 countries contribute to the IGS, a service established within the International Association of Geodesy since 1994. The IGS intends to integrate future GNSS signals, such as Galileo, into its activities, as demonstrated by the successful incorporation of GLONASS.
For more information: Contact International GNSS Service Central Bureau, Jet Propulsion Lab MS 238-540, Pasadena, CA 91109 USA; phone (818) 354-2077, fax (818) 393-6686, email:

Geoscience Australia is Australia’s national agency for geoscience research and geospatial information. It maintains a comprehensive Web site with information about many GPS-related topics. Users can download data from the Australian Regional GPS Network and view graphs of data quality and time-series of positions. An online GPS processing service (AUSPOS) allows users to upload dual-frequency Rinex data and receive computed ITRF positions rapidly by e-mail. Within Australia, these ITRF positions are also transformed to the Geocentric Datum of Australia. The site provides information about Australian coordinates, datums, and transformations. Geoid-ellipsoid separations for the region can be downloaded or computed on line.
For more information: Contact Geoscience Australia, phone +61 (2) 6249 9111, fax +61 (2) 6249 9929, e-mail:

Czech Republic
The Czech Technical University, Faculty of Electrical Engineering, Department of Radio Engineering in Prague, Czech Republic, offers historical constellation status and almanac data for both GPS and GLONASS systems.
For more information: E-mail service administrator at or contact Frantisek Vejrazka, Czech Technical University, Technicka 2, 166 27 Prague 6, Czech Republic; phone: (+420) 2 2435 2246, fax: (+420) 2 3333 9801, e-mail:

Danish Geodata Agency provides GNSS raw carrier-phase data by request. This services are based on the permanent reference station network, operated by the Danish Geodata Agency (GST).
For more information: Contact Casper Jepsen, Danish Geodata Agency, Rentemestervej 8, DK-2400 Copenhagen NV, Denmark; phone +45 72 54 50 00, e-mail:

The Information–Analytical Center (IAC) of the Russian Space Agency publishes official information about GLONASS status and plans as well as consultation, information, and scientific-method services to increase GLONASS applications efficiency. It provides current constellations, Earth maps of the current and daily navigation availabilities, results of GNSS navigation field monitoring in the Moscow area in a real-time mode, and other data.
For more information: IAC, Mission Control Center, e-mail: