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Almanac

The Almanac

August 1, 2010 By: GPS World Staff GPS World

Orbit Data and Resources on Active GNSS Satellites

GPS Constellation
GPS Satellite & System Information
GLONASS Constellation
GLONASS Satellite Information
Galileo System
Beidou/Compass System
Satellite-Based Augmentation Systems
GNSS Internet Information

General Notes:

“SV Number” refers to space vehicle number. “PRN Number” refers to the satellite’s unique pseudorandom noise code.
Clock: Rb = rubidium; Cs = cesium. Only clock changes made since this Almanac was last published in December are included in the performance notes.
“Launched” and “Usable” dates are based on Universal Time.
The current GPS constellation consists of 11 usable Block IIA satellites, 12 Block IIRs, and 7 Block IIR-Ms for a total of 30 satellites and is under FOC (Full Operational Capability).
SVN35 and 36 carry onboard corner-cube reflectors for satellite laser ranging (SLR). SLR tracking of the satellites permits analysts to differentiate between onboard clock errors and satellite ephemeris errors in GPS tracking. SVN35/PRN05 was decommissioned from active service on March 26, 2009.
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.
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.
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.
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.
Dr. Richard Langley of the University of New Brunswick provided the GPS satellite status information and compiled the notes.

Performance Notes:

A.    SVN24/PRN24 reintroduced into the almanac on December 21, 2009. Being moved to slot D2-F.
B.    Retired from active service on December 18, 2009; placed in disposal orbit.
C.    SVN26/PRN26 being moved to slot F2-F.
D.    SVN38/PRN08 active clock switched from Rb1 to Cs4 on November 16, 2009.
E.    SVN49/PRN01 remains set unusable until an L1/L2 satellite multipath issue is resolved. Being moved to slot B1-F.
F.    SVN62/PRN25 was launched on May 28, 2010. It remains unusable until commissioning tests are completed. SVN62/PRN25 active clock switched from Cs3 to Rb1 on July 12, 2010.

GPS Satellite & System Information

Jump to links:

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 se@unb.ca.

National Geospatial-Intelligence Agency (NGA)
Precise GPS Orbit Information and Earth Orientation Parameter Predictions (EOPP)

Anonymous FTP Access:
ftp://ftp.nga.mil/pub2/gps/pedata/
ftp://ftp.nga.mil/pub2/gps/apcpe/
ftp://ftp.nga.mil/pub2/gps/predictions/9DayGPSpreds/
ftp://ftp.nga.mil/pub2/gps/predictions/Rapids/

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: gps@nga.mil. 24-hour contact: 314-676-9140 or DSN 846-9140.

National Executive Committee (EXCOM) for Space-Based Positioning, Navigation & Timing (PNT)

The EXCOM advises senior national government leadership and coordinates federal agencies about policy matters concerning the 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. 6822, 1401 Constitution Ave. NW, Washington, D.C. 20230, phone: 202-482-5809, fax: 202-482-4429, e-mail: pnt.office@pnt.gov.

Natural Resources Canada, Geodetic Survey Division
GPS Data, GPS Orbits, GPS Clocks, and Online Positioning

Natural Resources Canada, Geodetic Survey Division operates the Canadian Active Control System (CACS), a national network of continuously operating GPS tracking stations. Products derived from CACS include GPS observation data, precise GPS orbits, and a precise GPS clock. The system supports the positioning requirements of a broad range of users, including the most demanding post-mission scientific applications to real-time users requiring meter level accuracies related to the Canadian Spatial Reference System (CSRS) and International Terrestrial Reference Frames (ITRF). An online Precise Point Positioning (CSRS-PPP) service allows GPS users from around the world to recover accurate positions from a single GPS receiver by submitting their RINEX observation data via the Internet. GPS-C, a GPS correction service supports national real-time GPS positioning, including the Canada-wide Differential GPS (CDGPS) Service. 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 Client Services, 615 Booth Street, Ottawa, Ontario, Canada K1A 0E9; phone (613) 995-4410, fax (613) 995-3215, e-mail information@geod.nrcan.gc.ca, or contact Paul Godin, information services manager, e-mail pgodin@nrcan.gc.ca.

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, LORAN-C, and Coast Guard Local Notice to Mariners information.
Voice recording for GPS constellation status: (703) 313-5907.
Radio broadcasts: WWV minutes 14 and 15, and WWVH minutes 43 and 44, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz (last one is WWV only).
For more information: Contact the NIS Watchstander, 24 hours a day, at phone (703) 313-5900, fax (703) 313-5920, or e-mail tis-pf-nisws@uscg.mil.

Scripps Orbit and Permanent Array Center (SOPAC)
GPS Orbits, Coordinate Information, and Data Archive

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 1,500 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 http://sopac.ucsd.edu/projects/realtime/. 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 archive@gpsmail.ucsd.edu or Director Yehuda Bock, ybock@ucsd.edu.

DoD GPS Operations Center & 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: Questions and anomaly reports from civilians and industry, contact Navigation Information Service (see previous listing). DOD-associated activities only, e-mail gps_support@schriever.af.mil.

GPS Test Center of Expertise

Jump to links:

The 746 Test Squadron, based at Holloman Air Force Base in New Mexico, provides archived almanac data in SEM3.6 and YUMA formats and a special almanac detailing the short GPS week, observed range errors as viewed from the GPS Satellite Reference Station at Holloman Air Force Base, constellation status, and user advisories. Information dates back to 1992 and is available 24 hours a day. The site also will soon offer links to the GPS Test Center of Expertise legacy databases.For more information: Michael P. Brown, phone (505) 679-2863, e-mail michael.brown@46tg.af.mil.

U.S. National Geodetic Survey (NGS)
GPS Orbit Information

The U.S. National Geodetic Survey (NGS) of the National Oceanic and Atmospheric Administration manages the National and Cooperative CORS (Continuously Operating Reference Station) network. This network currently contains more than 1,400 GPS data-collection sites in the United States and its territories, with a few in foreign countries. NGS provides free access to GPS data from these sites via the Internet. CORS sites are operated by a collection of more than 186 organizations, representing various federal, state, local, and foreign government agencies, as well as various academic and commercial institutions. The CORS network enables GPS users to determine centimeter-level positional coordinates for user-selected locations.

Additionally, CORS data serve to monitor crustal motion, the distribution of moisture in the atmosphere, and the distribution of free electrons in the ionosphere. NGS also provides the Online Positioning User Service (OPUS). This web-based utility enables users to submit static GPS data for automatic processing with relevant CORS data. Within minutes, after receiving a user’s data, OPUS returns computed positional coordinates for the location associated with the data. NGS recently released OPUS-RS (Rapid Static) that will return a solution for as little as 15 minutes of data, whereas OPUS requires at least two hours of data.

In addition, NGS provides “final” and “rapid” precise orbits for GPS satellites and calibrates GPS-receiving antennas to determine how the locations of an antenna’s L1 and L2 phase centers vary, with respect to the orientation of an incoming GPS signal. Moreover, various web-based utilities for performing standard geodetic operations, such as transforming coordinates between reference frames and converting GPS-derived heights to orthometric heights, are available in the NGS Geodetic Toolkit. The National Geodetic Survey will serve as the IGS Analysis Center Coordinator for a period of four years starting on January 1, 2008. NGS will coordinate the activities of several international geodetic organizations in producing high precision GNSS orbits. For more information: Contact NGS at ngs.cors@noaa.gov or call Rick Foote at (301) 713-3205, ext. 152.

U.S. Naval Observatory

The U.S. Naval Observatory (USNO) provides GPS timing data and status information. For more information: Contact Stephen Mitchell, phone: 202-762-0740 or DSN 762-0740, e-mail: stephen.mitchell@usno.navy.mil.

International

International GNSS Service (IGS)

ftp://igscb.jpl.nasa.gov

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, e-mail igscb@igscb.jpl.nasa.gov.

Australia

Geoscience Australia

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 geodesy@ga.gov.au.

Europe

Jump to links:

Czech Republic

ftp://polaris.feld.cvut.cz/pub/almanac/

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 puricep@feld.cvut.cz 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: vejrazka@feld.cvut.cz.

Denmark

Kort og Matrikelstyrelsen (National Survey and Cadastre-Denmark) provides GPS raw carrier-phase data by request and maintains the following services: NAV-DK and Code |corrections distributed by way of cellular telephony. These services are based on the permanent reference station network for GPS operated by the National Survey and Cadastre-Denmark. For more information: Contact Casper Jepsen or Bo Hansen, Kort and Matrikelstyrelsen, Rentemestervej 8, DK-2400 Copenhagen NV, Denmark; phone +45 72 54 50 00, fax +45 35 87 50 51, e-mail kms@kms.dk.

General Notes:

The first GLONASS satellite was launched October 12, 1982.
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.
The Russian Federation designated the “Kosmos Number.”
GLONASS numbers 1–94 have been withdrawn from service.
All operational satellites are GLONASS-M satellites.
All launch and usable dates are based on Moscow Time (Universal Time + 3 hours).
Channel number “k” indicates L1 and L2 carrier frequencies: L1 = 1,602 1 0.5625 k (MHz); L2 = 1,246 + 0.4375 k (MHz).
All GLONASS satellites use cesium atomic clocks.
Twenty-one GLONASS satellites are set healthy.
The latest triple GLONASS launch was on March 1, 2010. The next launch is scheduled for September 2, 2010.
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.
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.
Information compiled by Richard Langley.

Performance Notes:

    A.    GLONASS 92 had been set unhealthy since June 18, 2009. The satellite was decommissioned on February 27, 2010.
    B.    GLONASS 99 had been set unhealthy since November 2, 2009. The satellite was decommissioned on February 28, 2010.
    C.    GLONASS 100 was placed in reserve status on March 19, 2010.
    D.    L2 signals of GLONASS 108 are unusable.
    E.    GLONASS 112 had been set unhealthy since August 31, 2009. The satellite was placed in reserve status on March 19, 2010.

GLONASS Satellite Information

The Information–Analytical Center (IAC) of the Russian Space Agency (www.glonass-ianc.rsa.ru) 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.

United States and Canada

Jump to links:

Canadian Space Geodesy Forum: See listing for the Canadian Space Geodesy Forum in the “GPS Satellite Information” section.

Europe

Czech Republic: See listing for the Czech Technical University, Faculty of Electrical Engineering, Department of Radio Engineering in the “GPS Satellite Information” section.

Russia: 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 fields monitoring in the Moscow area in a real-time mode, and other data.
For more information: IAC, Mission Control Center, e-mail glonass-ianc@mcc.rsa.ru.

Notes:

A.    GIOVE-A and -B can only transmit two signals at a time; either E1+E5 or E1+E6.
B.    Operates on rubidium atomic clock. Orbit raised by 80 km during July and August 2009.
C.    Operates on hydrogen maser atomic clock.

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), headquartered in Brussels, Belgium, took over Galileo responsibility from GJU on January 1, 2007. 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 will secure 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. It continues to transmit test signals. The second test satellite, GSTB V2/B or GIOVE-B, constructed by a team led by Astrium GmbH in Ottobrunn near Munich, Germany, was launched on April 26, 2008. It continues to transmit test signals. The first two in-orbit validation (IOV) satellites are scheduled for launch in June 2011, followed by two more in October 2011.

For more information:

Astrium
EC Directorate-General for Energy and Transport
ESA
GSA
SSTL

Beidou/Compass System Information

China has developed a regional satellite-based navigation system known as Beidou (Chinese for the “Big Dipper” asterism). The initial constellation of three geostationary Earth orbit (GEO) satellites was completed in 2003. The first Beidou Navigation Test System 1 (BNTS-1) satellite, or Beidou 1A, was launched on October 30, 2000, into a geostationary orbit slot at 140° E. On December 20, 2000, Beidou 1B followed, going into a slot at 80.5° E. Beidou 1C, an in-orbit back-up satellite, was launched into an orbit at 110.5° E, on May 24, 2003. A fourth satellite, Beidou 1D, was launched on February 2, 2007 into the slot at 145° E. After some initial difficulties, the satellite was made operational. However, in 2009 it was abandoned and placed in a “graveyard” orbit. There are some reports that Beidou 1A is no longer operational. The initial regional Beidou system is being expanded into a global system to be known as Beidou-2 or Compass. It will likely include five GEO satellites and additionally 30 or so medium Earth orbit (MEO) satellites. The first MEO satellite, known as Beidou M1, was launched on April 13, 2007, into a circular orbit with a radius of about 27,900 kilometers. The first GEO satellite, known as Beidou G2, was launched on April 14, 2009, into a slot at 83.5° E but is uncontrolled and is librating around the 75° E libration point of the Earth’s gravity field. Two more GEOs have been launched: G1 on January 17, 2010, into a slot at 160° E and G3 on June 2, 2010, into a slot at 84.6° E. G1 was moved to 144.5°E in an operation that began around June 6, 2010.

For more information:

www.sinodefence.com/strategic/spacecraft/beidou1.asp
www.sinodefence.com/strategic/spacecraft/beidou2.asp

Satellite-Bassed Augmentation Systems

Notes:

A.    Inmarsat 3-F2 began EGNOS Initial Operations on July 6, 2006, and is transmitting message type 0/2.
B.    Artemis was being used for test transmissions using message type 0/0 until February 17, 2009 when it began Initial Operations service, transmitting message type 0/2.
C.    Official start of EGNOS Open Service on October 1, 2009.
D.    Inmarsat 3-F5 began EGNOS Initial Operations on June 3, 2006, transmitting message type 0/2. On February 19, 2009, PRN 126 switched to mode 0/0 in conjunction with a planned move to the Inmarsat 4-F2 satellite at the same orbit longitude.
E.    Test transmissions using the Inmarsat satellite ceased on April 8, 2008, and were to resume after the launch of India’s GSAT-4. The launch on April 15, 2010, failed. A replacement satellite is planned.
F.    MSAS commissioned for aviation use on September 27, 2007. Either satellite can transmit both PRN signals if necessary.
G.    Galaxy XV was switched from test mode to normal mode on November 9, 2006. Ranging supports enroute through non-precision and precision approach modes. Control of Galaxy XV, originally at 133° W, was lost on April 5, 2010, and the satellite is now drifting eastwards. As of July 12, 2010, it was still transmitting WAAS signals.
H.    Anik F1R was switched from test mode to normal mode on July 13, 2007. Ranging supports enroute through non-precision and precision approach modes.
I.    The Galaxy XV and Anik F1R WAAS payloads, operated by Lockheed Martin for the FAA, are known as LMRPS-1 and LMRPS-2, respectively.
J. Test transmissions. Operational service is expected by the autumn of 2010.