Operators in the 2nd Space Operations Squadron (2SOPS) of the USAF 50th Space Wing migrated control of the GPS satellite constellation and ground monitoring facilities from a 1970s-era mainframe computer to a distributed IT infrastructure with advanced automated features. The 50th Space Wing, through the 2nd SOPS, performs the satellite command and control mission for the Global Positioning System.

On September 14, Air Force crews at Schriever AFB, Colorado, completed the initial phase of an $800 million upgrade to the GPS operational control segment.

Operators in the 2nd Space Operations Squadron (2SOPS) of the USAF 50th Space Wing migrated control of the GPS satellite constellation and ground monitoring facilities from a 1970s-era mainframe computer to a distributed IT infrastructure with advanced automated features. The 50th Space Wing, through the 2nd SOPS, performs the satellite command and control mission for the Global Positioning System.

The upgrade, called the Architecture Evolution Plan (AEP), will add new digital communications and a new message format for telemetry, tracking, and control (TT&C) —uploading information and operational commands to the GPS satellites. A new capability to command satellites through Air Force Satellite Control Network (AFSCN), will increase the number of available antennas for contacting satellites.

The Air Force team, along with contractors from Boeing, Lockheed Martin, and The Aerospace Corporation, have been preparing for the transition to the new control segment since March 2006.

“This is like changing the engine on a car while it is traveling 50 miles an hour down the road,” says Lt. Gen. Michael Hamel, commander of the Space and Missile Systems Center at Los Angeles AFB, California, where the GPS Wing is located.

The upgrade also involved installing and activating the alternate Master Control Station at Vandenberg AFB, California, and upgrading the current GPS ground antennas.

The addition of eight National Geospatial-Intelligence Agency facilities to the six GPS-dedicated monitoring stations around the globe will reportedly provide triple-redundancy tracking of satellites — that is, every satellite will be visible to at least three ground stations 99 percent of the time to quickly identify signal anomalies or outages.

Groundwork for the Future
AEP will lay the foundation for future improvements to the Operational Control Segment (OCS) to support new capabilities, such as those that will become available with the GPS Block IIF satellites. A further AEP upgrade next summer will enable support the new Master Control Station at Schriever to operate the IIFs, the first launch of which has been delayed until late in 2008.

On August 27, under GPS Wing review, the first GPS Block IIF satellite successfully passed its Initial Integrated System Test (IIST) at the Boeing Spacecraft Development Center in El Segundo, California. Completion of the IIST signifies the spacecraft is ready to enter acoustic, separation, and thermal vacuum testing.

A next-generation GPS control segment (OCX) is scheduled to be in place in the 2011–12 time frame to support the GPS III generation of satellites scheduled to launch beginning in 2013. Three industry teams led by Lockheed Martin, Raytheon, and Boeing are competing for the OCX contract, which is expected to be announced soon. A request for proposals to build the GPS IIIA satellites was issued earlier this year, with a decision now not expected before early 2008.

Hope for Invisible Transition
Rehearsed several times several times in advance, the Air Force used a phased approach with satellites transitioning to the new OCS one at a time.

The new AEP message structure has been analyzed down to the bit, according to Air Force officials, and is functionally equivalent to the legacy message. It incorporates a new Kalman filter that will enable the system controllers to monitor and control more satellites and signals, including uploading navigation messages more frequently. The legacy TT&C architecture can only support about 31 satellites but will be able to handle up to 60 after OCX is complete in 2013, according to Col. David Madden, commander of the GPS Wing.

According to the Air Force, in the event of an unforeseen anomaly during transition, the process is fully reversible at any time.

The transition to AEP was originally scheduled to occur more than five years ago. But the task turned out to be more complicated than expected. The AEP makes use of a unique complex software system that is a wholesale replacement for the old one. Moreover, additional requirements were added and others changed over the course of development as the system and software matured, according to statements from the GPS Wing.

Help for civilian GPS users
Air Force officials expected that the transition would be transparent to GPS users. However, should problems appear that might be connected with AEP, civil users may contact the U.S. Coast Guard Navigation Center, telephone 703-313-5900, website <http://www.navcen.uscg.gov/>.

Help for military GPS users
Military users should contact the GPS Operations Center, telephone DSN 560-2541 OR commercial 719-567-2451, website <http://gps.afspc.af.mil/GPSOC/>.

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Operators of the world’s four GNSS systems and regional augmentation systems have laid the foundation for a multilateral environment in which to discuss issues of compatibility and interoperability.

Operators of the world’s four GNSS systems and regional augmentation systems have laid the foundation for a multilateral environment in which to discuss issues of compatibility and interoperability.

Meeting September 4 in Bangalore, India, in advance of a session of the International Committee on GNSS (ICG), six nations established a Providers Forum that will operate in parallel with the United Nations–backed group. Ken Hodgkins, deputy director of the State Department’s Office of Space & Advanced Technology, characterized the ICG gathering as “a huge success.”

“The PF [Providers Forum] was particularly notable in that we reached a common understanding on the general concept of compatibility and interoperability in a multilateral setting,” Hodgkins told Inside GNSS.

Initial members of the forum and their current and future systems include: China, Compass/Beidou Navigation Satellite System (CNSS); the European Union, Galileo and the European Geostationary Navigation Overlay Service (EGNOS); India, the GPS Aided Geo Augmented Navigation (GAGAN) system and Indian Regional Navigation Satellite System (IRNSS); Japan, the Quasi-Zenith Satellite System (QZSS) and the MTSAT Satellite-based Augmentation System (MSAS); Russian Federation, GLONASS and Wide-area SDCM (System of Differential Corrections and Monitoring); United States, GPS and the Wide Area Augmentation System (WAAS).

As noted in a report from the session, “The forum is not a policy-making body, but provides a means to promote discussion among system providers on key technical issues and operational concepts.” Nonetheless, it represents a comprehensive membership and focus on GNSS affairs that has not previously existed.

Baseline Principles
In the course of their discussions, the Providers Forum participants agreed on the following points:

• Transparency in the provision of open services is desirable, and requires the open publication and dissemination of signal and system characteristics, in due time, to allow manufacturers to design and develop GNSS receivers on a non-discriminatory basis.
• Discussions should emphasize cooperation regarding GNSS infrastructure (space and ground control/monitoring segments).
• System providers should strive to monitor the performance of their open signals and provide timely updates to users regarding critical performance characteristics such as timing accuracy, positioning accuracy and service availability.
• The protection of RNSS [radionavigation satellite service] spectrum is vital to GNSS service provision. Therefore, adequate spectrum protection through domestic and international regulation should be pursued.
• Physical separation of operational satellite constellations and end-of-life disposal orbits should also be examined.

Compatible, Interoperable
On the key issues of GNSS system compatibility and interoperability, the forum established the following definitions and principles:

Compatibility refers to the ability of space-based positioning, navigation, and timing services to be used separately or together without interfering with each individual service or signal.

• Radiofrequency compatibility should involve thorough consideration of detailed technical factors, including effects on receiver noise floor and cross-correlation between interfering and desired signals.

• Compatibility should also involve spectral separation between each system’s authorized service signals and other systems’ signals.
• Any additional solutions to improve compatibility are encouraged

Interoperability refers to the ability of open global and regional satellite navigation and timing services to be used together to provide better capabilities at the user level than would be achieved by relying solely on one service or signal.
• Ideal interoperability allows navigation with signals from at least four different systems with no additional receiver cost or complexity.
• Common center frequencies are essential to interoperability, and commonality of other signal characteristics is desirable.
• Geodetic reference frames and system time standards should also be considered.

The Indian Space Research Organization hosted the full ICG meeting September 4-7 and cochaired the Providers Forum with the United States.

Forum participants agreed to meet again, no later than the next meeting of the ICG, in Pasadena, California, Dec 8-12, 2008. They may also meet on the margins of the next session of the Scientific & Technical Subcommittee of the United Nations Committee on the Peaceful Uses of Outer Space in February 2008.

The UN Office for Outer Space Affairs, as the Secretariat for the ICG, will continue to act as the focal point for Providers Forum meeting preparations. The chair of the Providers Forum will rotate among the members each year.

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These signals will be implemented on the Galileo Open Service and the GPS IIIA new L1 civil signal known as L1C.

The United States and the European Union (EU) have agreed to use the multiplexed binary offset carrier (MBOC) for a common GPS-Galileo signal for civilian use. In the future, this will enable combined GNSS receivers to track the GPS and Galileo signals with higher accuracy, even in challenging environments that include multipath, noise, and interference.

These signals will be implemented on the Galileo Open Service and the GPS IIIA new L1 civil signal known as L1C.

MBOC will appear first on the Galileo L1F signal transmitted by Galileo In-Orbit Validation Element (GIOVE) spacecraft, the first of which — GIOVE-A — has been in orbit since its December 27, 2005, launch. A GPS IIIA launch is not currently expected before 2013. The larger GIOVE-B satellite, which more closely matches the fully operational Galileo spacecraft design, is scheduled for launch in the final days of this year.

On September 3 the spacecraft — built by a production team led by prime contractor Thales Alenia Space and including Telespazio, EADS Astrium, and ESA — began its journey from the Thales Alenia plant in Rome to the ESA-ESTEC facility in Noordwijk, The Netherlands.

GIOVE-B has successfully passed all preliminary tests, including the thermal-vacuum test that duplicates the satellite’s in-orbit environment, and will undergo further tests in The Netherlands before being sent to the Baikonur cosmodrome to start launch preparations.

Building on 2004 Pact
Building on the historic cooperative agreement on GPS and Galileo signed between the two parties in June 2004, a joint working group overcame technical challenges to design interoperable optimized civil signals that will also protect common security interests. Incorporating MBOC into both GPS and Galileo is expected to enhance commercial opportunities for the development of new GNSS products and services.

Matthias Ruete, director general of the European Commission’s energy and transport agency responsible for Galileo, said the announcement “underscores Europe’s commitment to interoperability between Galileo and GPS and to managing the Galileo program in an innovative partnership with the United States. The international GNSS community, including the U.S., will have full and transparent access to information on how to access Galileo and GPS services.”

U.S. State Department Principal Deputy Assistant Secretary Reno Harnish said, “The U.S.-EU collaboration that produced this innovation and led to its joint adoption reflects the strong working relationships that we have developed on GPS and Galileo. This technical milestone represents the next step in our ongoing commitment to open standards and market-driven innovation that will benefit all users world wide.”

The cooperative agreement reflects a marked turnaround in U.S. attitudes toward Galileo. In the early years of the George W. Bush administration, numerous attempts were made to forestall implementation of what was then seen as a rival to GPS.

Related article:

Inside GNSS Sept-Oct 2007, page 43: "The MBOC Modulation," by members of the Galileo Signal Task Force

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Russia’s Baikonur cosmodrome automatically suspended all Proton rocket flights, pending an investigation, after the failure of the rocket, which crashed in the steppes of Kazakhstan just over two minutes after lift-off. Russia rents the space facility from Kazakhstan, a former republic in the USSR.

The September 6 crash of a Russian Proton-M rocket carrying a Japanese telecommunications satellite (JCSAT 11) has injected an element of uncertainty into plans for completing the GLONASS constellation.

Russia’s Baikonur cosmodrome automatically suspended all Proton rocket flights, pending an investigation, after the failure of the rocket, which crashed in the steppes of Kazakhstan just over two minutes after lift-off. Russia rents the space facility from Kazakhstan, a former republic in the USSR.

Just two weeks earlier, the Russian Federal Space Agency (Roskosmos) had announced that the next triple GLONASS satellite launches would occur on October 25 and December 25, 2007. The Proton-M, the latest in a line of successful heavy Russian rockets, is used for the GLONASS-M launches. Europe’s Galileo program will use the Russian Soyuz launcher for its early missions, which also take flight from the Baikonur site.

Interfax news agency quoted officials at the Russian space technology manufacturer Khrunichev as saying that the failed launch may delay “commercial launches of foreign satellites” planned in November and December. Satellite operator SES Global, for instance, announced that the company will delay two planned satellite launches — SIRIUS 4 in October and AMERICOM 14 in December — pending the results of the official inquiry into the Proton launch failure.

The crash and the harsh Kazakh governmental criticism that ensued may also reinforce Russia’s plans to move GLONASS satellites onto a new rocket, the Soyuz-2, and launch these from the Plesetsk space facility in Russia instead of the Baikonur space center.

In comments at a press conference in April, Lt. General Alexander Kvasnikov, deputy commander of the Russian Space Forces, said, “We are planning to gradually transfer all launches of GLONASS satellites from Baikonur to the Plesetsk space center to ensure Russia’s independence in launching its own spacecraft.”

A Temporary Setback
The events in Kazakhstan may prove a momentary distraction from a GLONASS program that has been gathering momentum since the Russian government’s August 2001 decision to rebuild and modernize its GNSS system.

The GLONASS constellation currently has 12 operational satellites (four temporarily switched off as of September 8) and an additional modernized spacecraft (GLONASS-M) denoted as being in the “commissioning phase.” The latter satellite is one of three launched last December 25 that the Russian Space Forces have had trouble bringing on line.

Successful launches of the six additional GLONASS-M satellites would bring the constellation to initial operational capability (IOC) of 18 orbiting spacecraft and meet a program goal set in 2005. The current schedule calls for a fully operational capability (FOC) by the end of 2009.

Earlier this year, a decree by President Vladimir Putin ensured continuation of the GLONASS program through 2020. A proposed requirements update for the next 15 years was expected to be submitted in September, as well as a signal modernization plan and future GLONASS mission definition through 2040.

On August 31, the Roskosmos Information Analytical Center of Positioning, Navigation, and Time (IAC PNT) announced that an improved version of the national geocentric coordinate system “Earth Parameters 1990” (PZ-90.02) would be applied to the GLONASS system beginning September 20 in accordance with a Russian Federation governmental degree issued in June this year.

“On switching to the International Terrestrial Reference Frame ITRF2000, PZ-90.02 transformation parameters will contain only origin shift [from ITRF2000] along X, Y, Z by -36 cm, +8 cm, +18 cm respectively,” according to the IAC, adding that update sheets to the GLONASS Interface Control Document (version 5.0) would be published by September 10.

The GLONASS geodetic reference system will be “permanently improved in the direction of ITRF,” according to Russian officials, with the goal of coming within a few centimeters of the ITRF. This coordination of reference frames is expected to help reduce the inter-system errors in receivers using satellite signals from multiple GNSS systems.

Last April, the IAC PNT, which had been designated in 2006 as the GLONASS Information Center for the civil community, became an independent center within Roskosmos’s Central Research Institute for Machine Building (TsNIIMASH). Its role is to provide scientific and intellectual support for Roscosmos in PNT strategy development with respect to GLONASS.

Meanwhile, earlier this year Yuri Urlichich, director general of the Russian Institute of Space Device Engineering, was named chief designer for GLONASS.

Resources:
Roscosmos
www.roscosmos.ru/index.asp?Lang=ENG
GLONASS Information Analytical Center http://www.glonass-ianc.rsa.ru/pls/htmldb/f?p=202:1:17421293520707003964::NO

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