Capt. Adam Moody, 2 SOPS GPS Operations Support flight commander, and Staff Sgt. Carl Ellinger, 2 SOPS GPS mission chief, review a checklist of procedures for a transfer operation at Schriever Air Force Base. (Photo: U.S. Air Force photo/Dennis Rogers)
The 2nd Space Operations Squadron (2 SOPS), based at Schriever Air Force Base, will implement the GPS Issue of Data, Clock software modification this summer in accordance with established guidance, according to Rick Hamilton, CGSIC Executive Secretariat, U.S. Coast Guard Navigation Center.
The modification is in compliance with GPS Interface Specifications IS-GPS-200, which is published for manufacturers to ensure continued device compatibility.
As the largest Department of Defense spacecraft constellation, operators must modify processes, software and operations to meet the ever-growing demand for GPS signals. The squadron conducts software modifications regularly to support the constellation.
The modifications are primarily transparent to users, specifically those with IS-GPS-200 compliant devices. Users who experience issues with their devices or receivers should contact the manufacturer to troubleshoot the problem.
The U.S. Coast Guard Navigation Center provides information and services to civil GPS users. They can be contacted at 703-313-5900 or online.
U.S. Coast Guard issues testing notice on GPS Week Number Rollover.
The GPS Directorate has released a Federal Register Notice announcing plans to execute a test in February to investigate legacy receiver week roll-over behavior and analyze any off-nominal behavior exhibited, according to a U.S. Coast Guard notice.
Photo: andrey_l/Shutterstock.com
The GPS week number rollover occurs in the GPS legacy navigation (LNAV) message every 1024 weeks due to the GPS week number being represented by only 10 bits within the LNAV message.
The next GPS week number roll over will occur 18 seconds prior to the 0000Z boundary (Coordinated Universal Time) between April 6/7 2019.
In most cases, any negative response from a GPS receiver caused by a problem accounting for the 10-bit week number roll over would likely affect the calendar conversion from GPS time to UTC date/time and could result in the GPS receiver thinking it had jumped backward in time by 1024 weeks to 21/22 August 1999.
To participate in the test, submit the answers to the nine questions in the Federal Register Notice to the SMC/GPE mailbox by Feb. 4. After the submission of the questionnaire, the team will schedule individual meetings with interested civil vendors to further discuss their participation in the test in more detail.
GPS signals are so weak, they cannot be used reliably where they are obstructed such as indoors or in concrete canyons. But if the satellites were much closer, their signals would be much stronger. The low Earth orbit Iridium constellation is already orbiting and providing a PNT service. This month we learn about its current capability and future promise.
By David Lawrence, H. Stewart Cobb, Greg Gutt, Michael O’Connor, Tyler G.R. Reid, Todd Walter and David Whelan
(A shortened version of “Innovation Insights” appeared in the magazine.)
INNOVATION INSIGHTS with Richard Langley
WHOA CANADA! July 1st marks Canada’s sesquicentennial. In 1867, four Canadian provinces, Ontario and Quebec (up to then known as the single Province of Canada), Nova Scotia and New Brunswick, joined together to form The Dominion of Canada — the name suggested by New Brunswick’s Sir Leonard Tilley. Other provinces came on board later with the last, Newfoundland and Labrador, joining in 1949.
Apart from my interest in educating all and sundry about the origins of the “true north, strong and free,” what has this got to do with GNSS or allied technologies? Well, it turns out that Canada has played and continues to play an important role in the development of communications and navigation technologies.
It started on Christmas Eve, 1906, when Canadian inventor Reginald Fessenden carried out the first amplitude modulation radio broadcast of voice and music. And in 1925, Edward “Ted” Rogers, a Canadian pioneer in the radio industry, invented a radio tube using alternating current that became a worldwide standard in radio circuits.
Many other developments in terrestrial communications took place in Canada over the years including microwave repeater technology and shortwave radio broadcasting from the famed transmitter plant (now defunct, unfortunately) established near Sackville, New Brunswick, during World War II.
There have also been significant Canadian advances in satellite technology. The first Canadian satellite, Alouette (French for “skylark”), was launched in September 1962 to study the ionosphere. Launched by the United States, it was the first satellite to be constructed by a country other than the U.S. or the Soviet Union. Several other Canadian ionospheric research satellites have been orbited since including CAScade, Smallsat and IOnospheric Polar Explorer or CASSIOPE, launched in September 2013. CASSIOPE carries eight instruments for studying the ionosphere including the University of New Brunswick’s GPS Attitude, Positioning, and Profiling instrument.
Canada has also been a leader in satellite communications technology. The first Anik geostationary satellite was launched in November 1972. (Anik means “little brother” in Inuktitut.) Eight more Anik satellites were launched subsequently including Anik F1R, which is also used to broadcast Wide Area Augmentation System information to GPS receivers. And the first satellite to explore the 14/12-GHz band for direct broadcasting to homes and businesses was Canada’s Communications Technology Satellite, dubbed Hermes, launched in January 1976.
And, of course, we don’t need to mention the Remote Manipulator System on the International Space Station, commonly known as Canadarm, nor the work of celebrity Canadian astronaut Col. Chris Hadfield.
In the area of satellite navigation, Canada is known for its development of techniques to use the U.S. Navy Navigation Satellite System or Transit for one-meter positioning accuracy permitting establishment of geodetic control points such as in Canada’s far north. Canada was also an early adopter of GPS and with software and hardware developments by industry, government and academia has made its mark in the world of precision positioning, navigation and timing.
Another Canadian initiative is the Aerion satellite-based air traffic surveillance system that will use the enhanced low Earth orbit Iridium constellation.
And we shouldn’t forget that Canada is slated to provide the search and rescue package for the GPS III satellites.
Speaking of GPS, we all know what a great technology it is, providing the “gold standard” in global satellite navigation. But it does have one dominant problem: the weakness of the signals. The signals are so weak that they cannot be used reliably where they are obstructed such as indoors or in concrete canyons. The problem stems from the fact that these medium Earth orbit satellites are far away and their energy is significantly spread out during their passage to Earth. If the satellites were much closer to the Earth, their signals would be much stronger. Mind you, you would need more satellites to provide global coverage. Fantasy? No. There is already a constellation of satellites in orbit providing such a PNT service. It is Iridium–the same constellation that will provide the Canadian-initiated aircraft tracking system–and in this month’s column we will learn about is current capability and future promise. Pretty neat, eh?
With the advent of smartphones, there are now more than four billion devices that make use of GNSS. These satellite navigation systems provide not just the blue dot representing location on our phones, but also support the critical infrastructure we rely upon.
The U.S. Department of Homeland Security recognizes that all 16 sectors of U.S. critical infrastructure depend on GPS — 13 of which have critical dependence. A recent report by London Economics estimates the cost of a GNSS outage to the U.K. alone would be over £1B per day.With autonomous systems on the rise, our reliance on GNSS will only be increasing.
As we become more dependent on this technology, we become vulnerable to its limitations. One major shortcoming is signal strength. Designed to work in an open-sky environment, GNSS is severely limited in deep attenuation environments, with little or no service in dense cities or indoors. Furthermore, we are susceptible to jamming where a 20-watt GNSS jammer can deny service over a city block.
The proximity of low Earth orbit (LEO) has the potential to provide much stronger signals than the distant GNSS core-constellations like GPS in medium Earth orbit (MEO). Today, the only LEO system with global coverage is the Iridium constellation used primarily for communications.
FIGURE 1 shows the 31-satellite GPS constellation in contrast with the 66-satellite Iridium network. The scale of the difference in distance (several Earth radii) is extraordinary. The result is that Iridium signals are 300 to 2,400 times stronger than GNSS signals on the ground, making them attractive for use in position, navigation and timing (PNT) applications where GNSS signals are obstructed.
FIGURE 1. The 66-satellite Iridium constellation in low Earth orbit and 31-satellite GPS constellation in medium Earth orbit.
LEO-based PNT is now mainstream, in the form of real-time signals that have been delivered over the Iridium satellite network since May 2016. This service is made possible by Satelles in partnership with Iridium Communications Inc. in a service called Satellite Time and Location (STL), a non-GNSS solution for assured time and location that is highly resilient and physically secure. Consumers, businesses and governments are already using these LEO-based signals in environments with high GNSS interference or occlusion.
The security features of these signals are also used to reliably validate GNSS PNT solutions in real time to help mitigate potential spoofing. Furthermore, the fast LEO orbits of Iridium generate Doppler-frequency-shift signatures significantly stronger than GPS, increasing the utility of the STL signal for positioning applications.
STL field tests demonstrate a positioning accuracy of 20 meters and timekeeping to within 1 microsecond, all in deep attenuation environments indoors. This adds substantial robustness in augmenting the GNSS core constellations like GPS and also allows for a standalone backup in many applications.
LEO Constellations: Past, Present, Future
In 1964, Transit (or the U.S. Navy Navigation Satellite System) became the first operational satellite navigation system. This constellation typically consisted of five to 10 satellites placed in polar orbits with an altitude of about 1,100 kilometers. Unlike many terrestrial radio navigation systems, a position fix was not instantaneous. It required 10 to 16 minutes of observation as a satellite passed overhead to achieve the needed geometric diversity. There was also latency; users had to wait for a satellite to come into view, which could take from 30 to 100 minutes.
The trade-off was accuracy; early performance was a few hundred meters and was later improved to 20 meters (and even down to about 1 meter for multiple-pass fixed-site surveys), the best performance of its day. In 1967, Transit became open for civilian use and remained operational until 1996 when GPS was at full operational capability.
The Soviet Union developed a system similar to Transit known as Parus/Tsikada, with first satellites on orbit in 1967. Parus/Tsikada operated on the same passive Doppler observation principle as Transit, on similar frequencies and in similar polar orbits.
Today, the largest satellite constellation with constant global coverage is Iridium. With 66 LEO satellites delivering worldwide satellite connectivity, including the poles, this system has tenfold more satellites than Transit had. Along with its strong signals compared to the GNSS core-constellations in MEO, Iridium’s global coverage makes it ideal for use in PNT applications where GNSS is obstructed.
Figure 1 shows the scale of the difference in altitude with Iridium at 780 kilometers and GPS at 20,200 kilometers. This has substantial implications not only for signal strength, but also for coverage.
Though Iridium has twice as many satellites as GPS, at the Equator users can often only see one satellite at a time, whereas they can see 10 from GPS. This was one of the fundamental trades considered in the design of the GPS constellation. The higher the altitude, the more each launch cost; the lower, the more satellites had to be built to provide coverage. To put this in perspective, global coverage for one satellite in view at all times requires fewer than 10 satellites in MEO, but requires closer to 100 in LEO.
Future LEO Constellations
The hundreds of LEO satellites needed to match the coverage of GPS may be coming. In late 2014 and early 2015, the International Telecommunication Union reported a half-dozen filings for spectrum allocation for large constellations of LEO satellites.
In January 2015, OneWeb announced a partnership with Virgin and Qualcomm to produce a constellation of 648 LEO satellites to deliver broadband Internet globally. This represents the next order of magnitude, with tenfold more satellites than Iridium.
Within days of this announcement, SpaceX, with support from Google, announced a similar ambition for a constellation of more than 4,000 LEO satellites.
In August 2015, Samsung expressed interest with a proposal for a LEO constellation of 4,600. Boeing joined the race in June 2016, announcing plans for a LEO constellation of nearly 3,000 satellites.
These LEO constellations are being proposed to keep up with the rising demand for broadband, not to replace ground infrastructure, and will provide Internet access to the 54% of the global population that lack that access.
TABLE 1 compares the GNSS core constellations in MEO to the big (Iridium), broadband (OneWeb, SpaceX, Boeing) and early navigation (Transit, Parus/Tsikada) LEO constellations.
TABLE 1. Constellation comparison.
LEO versus MEO
Low and medium Earth orbit each have their individual strengths and weaknesses in the context of navigation as summarized by TABLE 2.
TABLE 2. Comparison of LEO and MEO systems for navigation.
Closer to Earth, LEO offers less spreading loss and improved signal strength on the ground. FIGURE 2 shows that the signal spreading (or space) loss for Iridium is between –140 and –130 dB compared to GPS at –160 dB.
This stems from Iridium being 25 times closer to Earth than GPS, resulting in a gain in the neighborhood of 252, which is approximately 30 dB (1,000 fold). This is confirmed by field tests where the carrier-to-noise-density ratio (C/N0) is typically 45 dB-Hz for GPS but closer to 80 dB-Hz for Iridium.
FIGURE 2. Slant range and spreading loss as a function of orbital altitude and user elevation angle (GSO = geostationary orbit).
Now, we face the drawback of LEO proximity: coverage. Being closer to Earth means that satellites have much smaller footprints as shown in FIGURE 3.
FIGURE 3. Comparison of medium and low Earth orbit satellite distance and footprints (drawn to scale).
FIGURE 4 shows the satellite-footprint radius as a function of orbital altitude and user elevation mask angle. This plot shows the GPS footprint to be threefold larger than Iridium’s, corresponding to nine times more area covered. Hence, to achieve the same coverage as GPS with Iridium’s altitude, a LEO constellation requires an order of magnitude more satellites.
FIGURE 4. Satellite footprint radius as a function of orbital altitude and elevation angle (GSO = geostationary orbit).
Another major difference between LEO and MEO is speed. A GPS satellite completes one Earth revolution every 12 hours, while Iridium does so in only 100 minutes. The shorter the orbital period, the faster the angular rate (also called mean motion) and the more quickly satellites pass overhead. The Earth-centered angular rate of Iridium is seven times faster than GPS.
As a result, users on Earth’s surface see LEO Iridium satellites traverse the local sky in just over 10 minutes compared to hours with satellites in MEO. This characteristic gives rapid changes in geometry and several benefits for navigation.
The swift motion whitens multipath (making it more random, like white noise) as reflections are no longer effectively static over short averaging times. Geometric diversity also leads to effective Doppler positioning as was once leveraged by Transit and now by STL using Iridium. Geometric diversity is also desirable for carrier-phase differential GNSS, allowing for much more rapid resolution of integer cycle ambiguities.
Iridium-Satelles STL Service
As previously mentioned, the STL service has been in operation since May 2016. Many from industry and government are already using this service to achieve a more robust PNT solution. This service will only continue to improve with the Iridium NEXT satellites under deployment — the first 10 were successfully launched in January.
STL is a non-GNSS solution for assured time and location that is highly resilient and physically secure. STL utilizes the Iridium constellation to transmit specially structured time and location broadcasts. Due to their high RF power and signal-coding gain, the STL broadcasts are able to penetrate into difficult attenuation environments, including deep indoors. Like GNSS signals, these broadcasts are specifically designed to allow an STL receiver to obtain precise time and frequency measurements to derive its PNT solutions.
STL is able to augment or serve as a back-up to existing GNSS PNT solutions by providing secure measurements in the presence of high attenuation (deep indoors), active jamming and malicious spoofing. Unlike the MEO GNSS satellites, Iridium uses 48 spot beams to focus its transmissions on a relatively small geographic area. The complex overlapping spot beams of Iridium combined with randomized broadcasts give a unique mechanism to provide location-based authentication that is extremely difficult to spoof.
Two main technical innovations are applied to the existing Iridium quadrature phase-shift keying (QPSK) transmission scheme to facilitate precision measurements. First, the QPSK data at the beginning of an STL burst is manipulated to form a continuous wave (cw) marker, which can be used for burst detection and coarse measurement. Second, the remaining QPSK data in the burst is organized into pseudorandom sequences, reducing the effective information data rate while providing a mechanism for precise measurement via correlation with locally generated sequences.
The processing gain of the sequence correlation operation also enhances the capability of the STL signal to penetrate buildings and other occlusions. STL is designed such that a receiver can reliably decode the bursts and perform precise Doppler and range measurements at attenuations of up to 39 dB relative to unobstructed reception. This is sufficient to penetrate buildings and other occlusions, providing coverage in most deep indoor and urban canyon environments.
In environments where both GNSS and STL time and location fixes are available, the GNSS fixes will generally be more accurate. The key advantage of STL is its ability to provide time and position fixes where GNSS is not available because of occlusions, spoofing or other reasons. In this respect, GNSS and STL can be seen as complementary technologies, and it is apparent that receivers supporting both are highly desirable when practical. An example of a combined GNSS + STL receiver board is shown in FIGURE 5 and is available from Satelles.
To test the signal penetration of STL, trials of the system were undertaken at multiple locations inside an urban high-rise building. For these tests, locations with little or no GPS reception were chosen to measure the impact of such an environment on STL signal reception.
Two GPS receivers were used, a smartphone with assisted GPS and a standalone consumer receiver using Bluetooth communications without assistance data. Similarly, STL was used with and without assistance. For these tests, STL assistance included real-time, out-of-band delivery of satellite clock and orbit data and message payload contents. These test locations ranged from the top (13th) to the bottom (2nd) floor as shown in FIGURE 6.
FIGURE 6. Iridium-based STL test locations. These are indoor and deep attenuation environments where GPS is unavailable.
The results show that only upper floors near windows were able to track at most one to two GPS satellites while lower floors could see none. STL, on the other hand, always experienced strong signals. Even on the lowest floor, with many layers of steel and concrete between the antenna and the sky, the C/N0 from Iridium was between 35 and 55 dB-Hz. GPS, by comparison, is typically between 35 and 50 dB-Hz in an open sky environment.
Indoor Time-Transfer Capability
To evaluate the timing performance of STL in a static, indoor environment, a custom STL receiver board was configured to generate a pulse-per-second (PPS) output. The difference in timing between the STL PPS was then compared to the timing output of a GNSS “truth” reference — in this case, a timing receiver that has nominal timing performance at least an order of magnitude better than the STL-based timing we were attempting to measure.
FIGURE 7 shows the timing difference between the PPS signals generated by the STL receiver and the GNSS receiver, showing the STL ability to provide sub-microsecond timekeeping even in a deep attenuation environment.
FIGURE 7. Iridium-based STL timekeeping results based on data from a 30-day indoor trial. This compares indoor STL timing with a GPS feed from outdoors. This shows STL’s timekeeping to be within 1 microsecond in a deep attenuation environment.
While sub-microsecond timing is sufficient for many applications, higher timing accuracy is desired by some. It has been further demonstrated that STL is capable of achieving sub-100-nanosecond timekeeping in a stand-alone configuration with a rubidium-based STL receiver with an unknown static location indoors.
Indoor Positioning Performance
Unlike the time-transfer capability of STL, positioning requires satellite motion over time to achieve a reasonable 4D time-and-location fix. Therefore, understanding the convergence properties of STL positioning accuracy over time is important to understanding the applicability of STL for various potential uses.
To study these convergence properties, STL data was collected over a 24-hour period in a one-story office environment. The data was then post-processed in a series of trials that each represented a different starting time in the data set — each trial offset to begin 5 seconds ahead of the previous trial’s start time. In this way, the 24-hour data set could be used to generate a statistically significant set of trial runs in which positioning convergence characteristics could be evaluated.
We found out from the results of the post-processed trials that after 10 minutes of convergence, the STL solution had converged to an accuracy of better than 35 meters for 67% of the trials. After sufficient time, typically an accuracy of 20 meters can be achieved in deep attenuation environments such as indoors. The vertical accuracy of STL, in the absence of other measurements or vertical constraints, is comparable to the horizontal accuracy.
Looking Forward
We see the benefit of LEO in navigation with the operational STL using Iridium, where stronger signals allow for operation deep indoors and in other GNSS-challenged environments. Though extremely valuable as a complement to GPS, Iridium lacks the numbers to fully replace GPS as a standalone navigation system in all capacities as only one satellite at a time is typically in view.
However, these numbers may be coming in LEO with the unprecedented scale of the recently announced Broadband constellations of OneWeb, SpaceX, Boeing and others summarized in Table 1. OneWeb’s constellation is nearly as large as the total number of operational satellites in LEO today and is an order of magnitude larger than Iridium. SpaceX’s and Boeing’s proposed constellations each have more than twice the total number of operational satellites in orbit in 2017.
The unparalleled number of satellites in these proposed broadband LEO constellations gives rise to better geometry than any of the GNSS core-constellations in MEO by at least threefold, as shown by FIGURE 8.
FIGURE 8. Comparison of geometric dilution of precision (98th percentile) as a function of constellation size and altitude (MEO = medium Earth orbit; GSO = geostationary orbit).
This plot represents the 98th percentile geometric dilution of precision a user would experience on Earth as a function of constellation size and altitude, assuming a 5-degree elevation mask angle. This stronger geometry allows for relaxation of the signal-in-space user range error, while still matching the user position accuracy of GPS. This enables the use of lower than traditional cost satellite clocks and more amenable orbit determination levels.
When combined with the more benign LEO radiation environment compared to MEO, satellite navigation payloads could be built using commercial off-the-shelf components in place of specialized space-hardened ones, greatly reducing cost. By partnering with these LEO constellation providers, much like Satelles has done with Iridium, a PNT service comparable to GPS could be achieved though with the added benefits of LEO including stronger signals and rapid changes in geometry.
Conclusion
Robust PNT services from LEO are here today, providing augmentation to GPS where GPS isn’t available. The addition of navigation signals from LEO provides a number of benefits. The faster LEO motion provides geometric diversity, giving rise to multipath whitening, faster initialization times for carrier-phase differential GNSS, and Doppler-based positioning.
Perhaps most importantly, LEO constellations have the advantage of being closer to the Earth than the GNSS core constellations in MEO, experiencing less path loss and delivering signals 1,000 times (30-dB) stronger. This makes them more resilient to jamming and more capable in deep attenuation environments such as in urban canyons and indoors.
This extra power allows the LEO-based Satelles STL using Iridium to achieve timekeeping within 1 microsecond and a positioning accuracy of 20 meters, all while deep indoors where GNSS is unavailable. This adds indispensable resilience and security to GNSS that we are increasingly reliant upon, creating a comprehensive satellite navigation system that truly works everywhere.
This PNT service using Iridium is perhaps a sign of things to come. We’ve seen a progression in LEO use since the dawn of the Space Age, namely, an order of magnitude increase in constellation size every 30 years. Transit first offered an occasional position update based on a constellation of six satellites in the 1960s.
Built in the 1990s, Iridium, with an order of magnitude more satellites at 66, now offers global coverage. On the horizon are constellations like OneWeb, which promise the next order of magnitude with 648+ satellites, slated for the 2020s. This most recent scale gives rise to better satellite geometry than GPS today with the added benefits of LEO.
The STL signal using Iridium sets a precedent that could lead to unparalleled navigation services that are robust due to the improved signal strength and precise due to the huge number of LEO satellites coming, each moving quickly and giving the geometric diversity needed to enable fast carrier-phase differential GNSS.
The need for such a service is already clear. It would enable a diversity of future technologies and applications, such as safety-critical autonomous vehicles under development that must operate in challenging urban environments.
Acknowledgments
This article is based on a book chapter to be released in a new generation of GPS “Blue Books” entitled 21st Century Navigation Technologies: Integrated GNSS, Sensor Systems, and Applications to be published by Wiley-IEEE.
The article was also based on the following Institute of Navigation conference publications by the authors:
“Differential and Rubidium Disciplined Test Results from an Iridium-Based Secure Timing Solution” by S. Cobb, D. Lawrence, G. Gutt and M. O’Connor in Proceedings of the 2017 International Technical Meeting of The Institute of Navigation, Monterey, California, 2017.
“Test Results from a LEO-Satellite-Based Assured Time and Location Solution” by D. Lawrence, H.S. Cobb, G. Gutt, F. Tremblay, P. Laplante and M. O’Connor in Proceedings of the 2016 International Technical Meeting of The Institute of Navigation, Monterey, California, 2016.
“Orbital Diversity for Satellite Navigation” by D. Lawrence, H.S. Cobb, G. Gutt, F. Tremblay, P. Laplante and M. O’Connor in Proceedings of ION GNSS 2012, the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation, Nashville, Tennessee, 2012.
“Leveraging Broadband LEO Constellations for Navigation” by T.G.R. Reid, A.M. Neish, T.F. Walter and P.K. Enge in Proceedings of ION GNSS+ 2016, the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, 2016.
Manufacturers
The unassisted Bluetooth receiver used was a Dual Electronics XGPS150A Universal Bluetooth GPS Receiver; the assisted-GPS smartphone used was a Samsung Galaxy S4. Timing output was evaluated with a Trimble Thunderbolt GNSS timing receiver.
DAVID LAWRENCE is the principal navigation architect for Satelles. In addition to authoring over 20 papers and over 30 patents, Lawrence has developed high-performance navigation software that has been deployed in aircraft landing, precision agriculture, mining, transportation, and machine automation.
H. STEWART COBB is the principal hardware architect for Satelles. Dr. Cobb has made a diverse range of contributions to the PNT community, including inventing and delivering the first commercial implementation of pseudolites as a principal hardware engineer at Novariant.
GREG GUTT is the president and chief technology officer of Satelles. As a graduate student, Gutt Developed ultra-low-noise superconducting sensors for NASA’s Gravity Probe B program. He later went on to become a Boeing technical fellow and is the original principal inventor of the Satelles time and location technology.
MICHAEL O’CONNOR is the chief executive officer of Satelles. As a graduate student, O’Connor developed the world’s first GPS-based precision steering system for farm vehicles. He went on to bring this technology to market with Novariant and helped launch the precision agriculture industry.
TYLER G.R. REID just completed his Ph.D. in the GPS Research Laboratory in the Department of Aeronautics and Astronautics at Stanford University. He is an alumnus of the International Space University and will soon be starting as a research scientist at Ford Motor Company on their autonomous driving team.
TODD WALTER is a senior research engineer in the Department of Aeronautics and Astronautics at Stanford University where he received his Ph.D. in applied physics. His research focuses on implementing high-integrity air navigation systems.
DAVID WHELAN was the vice president and chief technologist for Boeing Defense, Space & Security. Whelan earned his Ph.D. and MS in physics from the University of California Los Angeles and his B.A. from the University of California San Diego.
FURTHER READING
Authors’ Conference Publications
“Differential and Rubidium Disciplined Test Results from an Iridium-Based Secure Timing Solution” by S. Cobb, D. Lawrence, G. Gutt and M. O’Connor in Proceedings of the 2017 International Technical Meeting of The Institute of Navigation, Monterey, California, Jan. 30 – Feb. 1, 2017, pp. 1111–1116.
“Leveraging Commercial Broadband LEO Constellations for Navigation” by T.G.R. Reid, A.M. Neish, T.F. Walter and P.K. Enge in Proceedings of ION GNSS+ 2016, the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, Sept. 12–16, 2016, pp. 2300–2314 (best presentation award).
“Test Results from a LEO-Satellite-Based Assured Time and Location Solution” by D. Lawrence, H.S. Cobb, G. Gutt, F. Tremblay, P. Laplante and M. O’Connor in Proceedings of the 2016 International Technical Meeting of The Institute of Navigation, Monterey, California, Jan. 25–28, 2016, pp. 125–129.
“Orbital Diversity for Satellite Navigation” by P. Enge, B. Ferrell, J. Bennet, D. Whelan, G. Gutt and D. Lawrence in Proceedings of ION GNSS 2012, the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation, Nashville, Tennessee, 17–21 Sept., 2012, pp. 3834–3846 (best presentation award).
Global Navigation from Low Earth Orbiting Satellites
“Analysis of Iridium-Augmented GPS for Floating Carrier Phase Positioning” by M. Joerger, L. Gratton, B. Pervan and C. E. Cohen in Navigation, Vol. 57, No. 2, Summer 2010, pp. 137–160, doi: 10.1002/j.2161-4296.2010.tb01773.x.
“Overview of IRIDIUM Satellite Network” by K. Maine, C. Devieux and P. Swan in Proceedings of IEEE WESCON’95, the Microelectronics Communications Technology Producing Quality Products Mobile and Portable Power Emerging Technologies Conference (formerly Western Electronics Show and Convention), San Francisco, California, Nov. 7–9, 1995, pp. 483–490, doi: 10.1109/WESCON.1995.485428.
Transit, the U.S. Navy Navigation Satellite System
The Legacy of Transit, a special edition of the Johns Hopkins APL Technical Digest edited by V.L. Pisacane, Vol. 19, No. 1, Jan.–March 1998.
“A History of Satellite Navigation” by B.W. Parkinson, T. Stansell, R. Beard and K. Gromov in Navigation, Vol. 42, No. 1, Spring 1995, pp. 109–164, 10.1002/j.2161-4296.1995.tb02333.x.
“The Navy Navigation Satellite System: Description and Status” by T.A. Stansell, Jr. in Navigation, Vol. 15, No. 3, Fall 1968, pp. 229–243, 10.1002/j.2161-4296.1968.tb01612.x.
GPS and other Global Navigation Satellite Systems
Springer Handbook of Global Navigation Satellite Systems, edited by P.J.G. Teunissen and O. Montenbruck, published by Springer International Publishing AG, Cham, Switzerland, 2017.
I’m proud to be a part of the accomplishments of the men and women of the Space and Missile Systems Center’s Global Positioning System Directorate at Los Angeles Air Force Base in El Segundo, California. The year has been extremely challenging, but looking back on 2016, we have taken real steps forward to modernize the GPS Enterprise and the way we do business. I’d like to share some of our major accomplishments (see “2016 Accomplishments” below) and challenges, and provide some insights for 2017 and beyond.
Col. Steven Whitney. (Photo: USAF)
Civil Partnerships
While much of our focus is on military capabilities, GPS is a global utility with very strong ties to the civil community. The same principles of transparency and communication are cornerstones of our relationships with the various stakeholders.
One example of this is our work with the Federal Aviation Administration and the Department of Transportation, where the safety-of-life applications are a key element of our discussions. To ensure a transparent, communication-rich relationship, we hold quarterly program management reviews with these organizations and their stakeholders.
The GPS Directorate continues to actively participate on a number of committees, such as the Civil GPS Service Interface Committee, that are key to maintaining ties to our civil stakeholders and ensuring that we have an effective flow of information both to and from the Directorate.
We are currently engaged in the DOT-led Adjacent Band Compatibility study, initiated by the National Space-Based PNT Executive Committee. This year will see the culmination of the effort to determine power levels from potential future adjacent-band sources that are compatible with existing and evolving GPS receivers, and serve as a foundation to determine power levels compatible with evolving GPS/GNSS receivers.
This study exemplifies our strong ties with the greater GPS community, as well as my push for the Directorate’s efforts to be as transparent as possible, execute data-driven decisions, and be guided by widely accepted international standards.
Space Segment
A key milestone occurred Feb. 5, 2016, with the launch of our 12th and final GPS IIF satellite. This marked the end of an extremely successful GPS IIF launch campaign and our most aggressive launch schedule in the last 20+ years: eight successful launches in 24 months!
The addition of the GPS IIF satellites to the constellation enabled the system to reach its best performance day ever on May 11, 2016, achieving 36.5-centimeter accuracy in average user range error.
Col. Whitney with the Green Monster, mascot of the U.S. Air Force GPS Directorate. (Photo: USAF)
Moving over to our next generation GPS III satellites, SV-01 continues to make steady progress. In August, the team executed successful functional and physical configuration audits with Lockheed Martin, completing a key task on the road to achieving our available for launch (AFL) date. The AFL declaration signifies completion of production activities, and allows initiation of the Mission Readiness Campaign for launch upon Air Force direction.
As we march towards AFL, we are tackling several technical challenges, including a capacitor issue discovered during our investigation of SV-03 flight hardware tests. This capacitor is used in many places throughout the navigation payload. Our investigation uncovered inadequate qualification processes by a major subcontractor. Exercising due diligence, the Air Force is now verifying both the build quality of the entire capacitor manufacturing process and production lot via additional capacitor qualification life testing. This activity delayed our AFL until December 2016, approximately a four-month delay from our previous forecast.
The program is also working to solve several other technical challenges as we progress to completion. SV-01 testing uncovered electro-magnetic interference between a payload component and a hosted payload. Testing also uncovered electron impact issues on the L-band antenna elements. In partnership with Lockheed Martin, the program developed corrective action and design mitigations for both of these issues and is implementing these steps within our production flow for all the SVs. Of course, all these issues together have led to increased cost and contributed to delays in final delivery.
In the coming year, SV-02, the second GPS III satellite, will also be progressing towards completing production. Currently, all of the SV-02 sub-assemblies have been received by Lockheed Martin and are being integrated into the spacecraft. The next major step in the production flow for SV-02 will be to mate it with its propulsion core.
Recently, we completed negotiations with Lockheed Martin to extend the production line with purchases of SV-09 and SV-10. These satellites will be technically equivalent to SV-01 through SV-08. This $395 million purchase of two satellites marks a significant affordability milestone for the procurement of GPS III satellites.
Looking ahead, we are analyzing how to acquire satellites beyond SV-10. We are executing a phased strategy which starts first with determining the viability of a GPS III production design existing beyond the current contractor. We awarded an initial phase of contracts to the Boeing Company, Lockheed Martin Space Systems Company, and Northrop Grumman Aerospace Systems in May 2016 to provide a feasibility assessment of the readiness of their satellites designs. In this phase, the contractors will provide a GPS III production design, manufacturing plans and a navigation payload brassboard test report, along with manufacturing/production processes and facilities maturity.
We are also collaborating closely on an Air Force Research Laboratory Space Vehicles Directorate activity, the On-orbit Reprogrammable Digital Waveform Generator program, as an opportunity for the three contractors to develop advanced GPS L-band navigation signal processing capabilities in a smaller, more efficient package. This effort could potentially provide future satellites enhanced security in contested environments, more capable signal generation, and additional GPS waveforms to meet the growing needs of both military and civilian users.
Looking further ahead, the second phase is envisioned to be a full and open competition with contract awards starting in 2018. Contractors will be required to deliver the first satellite in time to support constellation sustainment commitments.
Control Segment
Our Control Segment consists of both OCX and our existing Operational Control Segment at Schriever Air Force Base, Colorado. The OCX program has struggled with many challenges through the years, producing a cost and schedule growth on OCX that exceeded the prescribed thresholds — in our case, a 25 percent cost growth against the approved Program Baseline.
I notified the Secretary of the Air Force on June 14 of this development, and on June 30 the Air Force declared a critical Nunn-McCurdy breach on the OCX program. The Nunn-McCurdy process is a mechanism for Congress to maintain oversight of DoD programs and requires the Office of the Secretary of Defense to conduct a review leading to a decision to either certify as critical to National Security or terminate the program.
The GPS Directorate and Raytheon, the OCX prime contractor, worked closely with teams conducting this in-depth, comprehensive review. The result was determined on Oct. 12 that OCX is essential to national security that no alternatives exist to meet requirements at less cost, remaining costs for the restructured program are reasonable and a higher priority than programs whose funding must be reduced to accommodate the growth, and management structure for the program is adequate.
With the review behind us, our challenge is to move forward with a stronger, healthier, more focused OCX program. To accomplish this, we are focused on several major areas: stronger systems engineering practices, establishing a single common hardware/environments baseline, greater software installation automation, and implementing industry standard software development processes.
One of our first milestones next year will be the delivery and deployment of OCX Block 0 in the summer of 2017. Block 0 is the GPS III Launch and Checkout System and provides a subset of the full OCX capabilities needed to launch the GPS III satellites and perform early on-orbit spacecraft bus checkout.
This delivery starts the drive for our inaugural launch of GPS III SV-01 in the spring of 2018. Raytheon completed two Block 0 key milestones since March 2016, and is now in formal qualification testing before it is deployed to operations early next year. The next year will see OCX development focused on Block 1. It provides the Initial Operating Capability to command and control all GPS satellites and enable the PNT mission, including the international L1C signal and advanced M-code features and capabilities.
Because OCX Block 0 is not designed to control the GPS III navigation payload, we are modifying the existing OCS to control GPS III satellites under Contingency Operations, or COps. COps will allow operation of the GPS III satellites launched prior to OCX Block 1 delivery in 2021, and provides the Air Force the ability to fly GPS III satellites at a capability level commensurate to a GPS IIF.
Our COps program has made good progress, completing its Preliminary Design Review last May and successfully passed Milestone B in September. COps is on track to hold its Critical Design Review in November, with delivery planned for the spring of 2019. We are exploring other potential OCS modifications to hedge against further delays in OCX.
Our OCS sustainment team in Colorado Springs recently completed the largest system update in program history. This update is part of our focus to refresh and bolster the cyber posture of the GPS architecture, and modernize the GPS control segment mission servers and hosted commercial software. These upgrades will protect against infiltration of cyber threats and enable improved data traffic logging for network situational awareness to protect this global utility.
User Equipment Segment
Like our other segments, our User Equipment segment had a very challenging but successful year. The MGUE program has worked steadily with our entire industry team, L-3 Communications, Raytheon, and Rockwell-Collins, to complete and test MGUE Increment 1 production prototypes. These Final Test Articles, or FTAs, started delivering this summer and are now capable of acquiring and actively tracking live-sky M-code. With the initial risk reduction testing phase complete, the Directorate will now use the FTAs to perform MGUE developmental testing and verification and hardware qualification testing.
The L-3 design was also the first on our program team to achieve security certification this October, which marks the very first security-certified M-code receiver card. This not only validates the L-3 design and production, it also validates the GPS security certification process, an enduring function for the Directorate in working with industry. This certification also leads the way for the product to be available to a wide variety of users across the DoD.
While progress in MGUE has been significant, creating the next-generation of secure, anti-jam, anti-spoof receivers has been more time-consuming and costly than expected. The drive to support warfighter needs for greater performance drives a diverse set of requirements across the DoD. The Air Force made a concerted effort to improve the resiliency of the MGUE receivers, adding complexity to the program. Combined, these challenges have led to extended delivery schedules for the program.
In the coming years, the MGUE team will lead efforts to integrate MGUE cards into four lead DoD platforms: the Air Force’s B-2 bomber, the Navy’s Arleigh Burke-class destroyer, the Army’s Distributed Defense Advanced GPS Receiver Device for the Stryker armored fighting vehicle, and the Marine Corps’ Joint Light Tactical Vehicle.
The four lead platforms provide pathfinder integrations and operational testing for the entire DoD community as we move into the modernized GPS era. The program office has already been working closely with the B-2 Program Office and the Joint Service System Management Office in fielding an M-code capable flight prototype Miniaturized Airborne GPS Receiver.
We have worked jointly on this first lead platform integration effort to field the first ever MGUE receiver integration into a higher order prototype unit. These efforts yielded tremendous integration insights. Prototype lab testing demonstrated live-sky tracking of C/A, Y and M-codes; testing of MGUE connected with a new B-2 flight antenna; and culminating in the first end-to-end demonstration of M-code capability.
In 2017, the GPS Directorate will set the acquisition strategy and plan forward for the MGUE Increment 2 program, addressing our long-term strategy for Application Specific Integrated Circuits, as well as meeting the needs of future platforms such as precision guided munitions, space receivers, and a modernized GPS handheld.
The Space Enterprise Vision
Earlier this year, General John Hyten, former commander of Air Force Space Command, announced the Space Enterprise Vision. The SEV is the result of an AFSPC study that looked at ensuring national security space capabilities in a contested environment, with an emphasis on improved resiliency. In the PNT mission area, there are many ways to provide greater resiliency in-line with General Hyten’s SEV. One that we are leaning forward and looking very hard at is multi-GNSS possibilities.
At the recent Institute of Navigation conference, many presenters noted that for the consumer market, the multi-GNSS era has already begun. Potential incorporation of non-GPS signals into military user equipment is still under review, but certainly offers the possibility of improving resilience to jamming, spoofing, and operations in obstructed terrain. The broader GPS community is developing approaches to assess multi-GNSS integrity, and we are working with those community members to evaluate the potential impacts to our GPS architecture, especially the ground.
Another resiliency initiative we are participating in is a DOT-led effort known as Advanced Receiver Autonomous Integrity Monitoring backed by PNT experts from the labs and academia. Once the technical aspects are well understood and the policy decisions are made, the GPS Directorate will be well positioned to take advantage of this opportunity.
Conclusion
2016 has been a very challenging and successful year. Looking forward into 2017 and beyond, we have numerous challenges across all segments of the Enterprise — OCX, GPS III, and MGUE — to deliver a modernized architecture. The men and women of the GPS Directorate and our Industry partners are truly some of the hardest working people I have ever had the opportunity to work with. It is their passion and dedication that has allowed us to continue to deliver the Gold Standard. It is my honor to serve with, and for, them.
2016 Accomplishments
Our GPS Next-Generation Operational Control System, or OCX program, received the majority of the press attention this year. OCX has struggled to overcome information assurance challenges, as well as poor systems engineering processes and planning from the outset of the program. The cost and schedule growth triggered a rigorous review by the Office of the Secretary of Defense.
The outcome, we believe, will be a restructured, more executable program that is implementing stronger systems engineering practices and industry-standard software development processes. We still have a ways to go to be successful, but realize we must deliver the capability to command our GPS satellites and will continue to explore programmatic off-ramps should the OCX program falter.
The past year also saw us bring to a close the GPS IIF production and deployment activities with the successful launch of our 12th and final GPS IIF satellite. Our GPS constellation remains healthy, stable and robust with 31 operational space vehicles: 12 GPS IIR, seven GPS IIR-M, and 12 GPS IIF.
We ushered in the GPS III era with the completion of Space Vehicle-01 thermal vacuum testing late in 2015 in an unprecedented 72 days. We have, however, uncovered several technical issues challenging our availability for launch. As we ready SV-01, a tremendous effort is ongoing to fully investigate and exonerate these issues to ensure our satellites deliver the capabilities you’ve come to expect from the Gold Standard.
This year our partners in the Launch Enterprise Directorate awarded a GPS III launch services contract to the Space Exploration Technology Corporation, or SpaceX — their first National Security Space System launch.
Finally, our Military GPS User Equipment (MGUE) program delivered its first set of Military Code compliant production prototypes for developmental testing and integration. Just as significant, the MGUE program granted the first-ever full security certification to contractor L-3 Communications. These major GPS modernization milestones are successful initial steps, but the progress in delivering the most secure, anti-jam, anti-spoof GPS receivers ever has taken longer than expected, and a great deal of work lies ahead.
This is by no means an exhaustive list of the year’s accomplishments and challenges, but it demonstrates that we are continuing to modernize the GPS system and maintain transparency on our commitments.
Lockheed Martin has completed a major upgrade to modernize the current ground control system of the U.S. Air Force’s GPS constellation.
The Commercial Off-the-Shelf (COTS) Upgrade #2 (CUP2) project is the latest step in the Air Force’s multi-year plan to refresh technology and transform the legacy Operational Control Segment — known as the Architecture Evolution Plan (AEP) — into a modern, high-performance command and control system.
On Oct. 15, CUP2 became fully operational and began managing the 31 GPS IIR, IIR-M and IIF satellites that make up today’s GPS constellation.
Capt. Adam Moody, 2SOPS GPS Operations Support flight commander, and Staff Sgt. Carl Ellinger, 2 SOPS GPS mission chief, review a checklist of procedures for a transfer operation at Schriever Air Force Base. (U.S. Air Force photo/Dennis Rogers)
The Air Force awarded Lockheed Martin the CUP2 project in November 2013 under its GPS Control Segment (GCS) contract, and the system is now fully deployed into the AEP’s GPS Master Control Station and the Alternate Master Control Station.
This is the third major technology refresh of the GPS command and control system since the GCS contract began in January 2013.
This upgrade to the existing ground control system provides the Air Force with flexibility. In May, as part of Contingency Operations (COps) under the GPS III contract, Lockheed Martin demonstrated a preliminary design to build off CUP2 and further upgrade the AEP to support next-generation GPS III satellites as they perform their positioning, navigation and timing mission. COps is a temporary gap filler prior to the entire GPS constellation’s transition onto the next-generation Operational Control System (OCX) Block 1, which is currently in development.
“Under CUP2, Lockheed Martin and the Air Force installed modern commercial hardware and a major software upgrade that enhances the system’s ability to protect data and infrastructure from cyber threats, as well as improves its overall sustainability and operability,” said Vinny Sica, vice president and general manager of Mission Solutions for Lockheed Martin. “Continued modernization and cyber-hardening of the GPS control system is vitally important to the sustainment of navigation services for our military and all global GPS users.”
The GPS Directorate at the U.S. Air Force Space and Missile Systems Center contracted the CUP2 upgrade. Air Force Space Command’s 2nd Space Operations Squadron (2SOPS), based at Schriever Air Force Base, Colorado, manages and operates the GPS constellation for both civil and military users.
The U.S. Air Force successfully launched the 12th Boeing-built GPS IIF satellite aboard a United Launch Alliance Atlas V Evolved Expendable Launch Vehicle from Space Launch Complex 41, Cape Canaveral Air Force Station, Fla., at 8:38 a.m. EST (5:38 a.m. PST) on Feb. 5.
“Today’s launch is a significant achievement in the history of GPS, as we launch the last of the GPS IIF satellites to be delivered on-orbit,” said Lt. Gen. Samuel Greaves, Space and Missile Systems Center commander and Air Force program executive officer for space. “The GPS IIF satellite performance has been exceptional and is expected to be operational for years to come.”
“This milestone is the result of the remarkable relationship between SMC, our operators within the 14th Air Force and our ULA/Boeing industry partners. Their continued tenacity and dedication to mission success ensures we continue to maintain a robust satellite constellation with modernized, more resilient GPS capabilities,” said Greaves. “A job ‘Well Done!’”
According to Greaves, this mission demonstrates the Air Force’s continued intent to deliver pre-eminent space-based positioning, navigation and timing service to users around the globe. GPS IIF is critical to U.S. national security and to sustainment of the GPS constellation for civil, commercial, and military users. GPS IIF satellites play an integral part in the modernization efforts vigorously being pursued across space, ground and user equipment to provide stronger signals and improved resiliency in the GPS constellation.
“Today’s launch marks a momentous milestone in the history of the Global Positioning System. It is the twelfth and last GPS IIF satellite and closes out nearly 27 years of launches for the GPS Block II family of satellites,” said Col. Shawn Fairhurst, 45th Space Wing vice commander, who served as the Launch Decision Authority. “As the nation’s premier gateway to space, we are proud to be part of the team providing GPS and its capabilities to the world and look forward to the future as we begin preparation for the next generation of GPS III satellites. Together with the Space and Missile Systems Center and our industry partners, we make up one team delivering assured space launch and combat capabilities for the nation.”
An Airmen-led processing team at CCAFS has processed every satellite of the series since GPS IIF-1 launched here in May 2010.
The Boeing-built GPS IIF satellites provides improved accuracy through advanced atomic clocks, a longer design life than previous GPS satellites, and a new operational third civil signal (L5) that benefits commercial aviation and safety-of-life applications. It also continues to deploy the modernized capabilities that began with the GPS IIR-M satellites, including a more robust military signal.
GPS is the United States Department of Defense’s largest satellite constellation with 31-operational satellites on orbit.
Operated by Air Force Space Command’s 50th Space Wing at Schriever Air Force Base, located east of Colorado Springs, Colo., the GPS constellation provides precise positioning, navigation and timing services worldwide as a free service provided by the Air Force, seven days a week, 24-hours a day.
Space and Missile Systems Center, located at Los Angeles Air Force Base in El Segundo, Calif., is the U.S. Air Force’s center for acquiring and developing military space systems. Its portfolio includes GPS, military satellite communications, defense meteorological satellites, space launch and range systems, satellite control networks, space-based infrared systems and space situational awareness capabilities.
First and foremost, let’s give a big hand to Adam and Anastasia, the two Galileo FOC satellites that were successfully launched on March 27. Following the not-so-successful Galileo launch in August, it was imperative that this go smoothly.
Although the Double-A launch occurred after the conclusion of this year’s Munich Satellite Navigation Summit, anticipation of the event set the context for the entire convocation. The summit is a fixture on the European and global GNSS calendar. It is always intense, often spectacular and sometimes leaves one with contradictory feelings. This year it took place March 24-26 and sought to determine the future of PNT, encouraging delegates to look into the crystal ball and predict developments.
If we go by the number of times these words were repeated during the three days of the summit, the future will hinge around compatibility and interoperability. The multi-constellation GNSS is already here. The elephant in the room remains, as always, interference, but here integration of alternative sensors and signals should hold the key to continuous and possibly resilient operations.
As usual the summit kicked off with a high-level plenary in the imposing Allerheiligen-Hofkirche (Court Church of All Saints) in the Residenz München, the Bavarian royal palace. The welcoming speeches and presentations were interspersed with some pleasant jazz, and the atmosphere was relaxed.
Into the Crystal Ball
Matthias Petschke, director of EU Satellite Navigation Programmes at the European Commission, admitted that 2014 had been difficult, but he was looking forward to 2015. Clearly the deployment of the Galileo infrastructure — especially the space segment — was critical, and the March 27 launch was very much on his mind. However, he expressed confidence that the launch would be fine and that satellite production was, and would remain, on schedule. In the long view, he stated: “We will make it for 2020,” signifying full operational capability (FOC).
He also talked about stimulating global markets to foster uptake of Galileo and EGNOS, and this was discussed by Carlo des Dorides, executive director of the European GNSS Agency (GSA). The ground infrastructure is very much in place and preparing for the Galileo exploitation phase. A significant milestone in that process would be finding the right partner to lead Galileo operations for the next ten years. A tender was now in process to find that organization or consortium. Des Dorides described the process as a competitive dialogue with the emphasis on finding a partner who can inspire new ideas and provide innovative solutions. The contract is big, worth around 1 billion euros.
Carlo des Dorides, Executive Director of the European GNSS Agency (GSA), discusses the 1 billion euro tender, now in process to find the organization or consortium to lead Galileo operations for the next ten years. Photo: GSA
He also emphasized the successes for EGNOS in the year. Almost 180 airports now benefit from EGNOS-enabled approaches and more than 70 percent of “GNSS-enabled” farmers in EU use the EU’s SBAS.
Johann-Dietrich Wörner, chairman of the German Aerospace Centre (DLR) — and the nominated next Director-General of ESA – highlighted the growing dependence of critical services on GNSS. In this context multiple systems were not a question of competition; it was all about redundancy and safety. Multi-GNSS improves availability, accuracy and reliability.
The view from the United States was given by Harold “Stormy” Martin, Director, National Coordination Office for Space-Based Positioning, Navigation, and Timing in Washington, D.C. The GPS fleet was now 30 strong in orbit including four successful launches in 2014 and he stated the 2014 averaged user range error to be 70 cms — the best ever — and improving year on year.
One major upcoming trend is a realization that there’s a need to establish a U.S.-wide backup coverage for GPS outage due to natural or man-made interference. The U.S. is currently assessing alternatives with a decision likely in summer 2015.
There was a particularly warm welcome from the audience for Michael Khailov, deputy head of Roscosmos and co-ordinator for GLONASS. Last year the Russians were conspicuous by their absence at the Munich Summit, but for 2015, despite the intervening local difficulty in Ukraine, they were back in force. Khailov claimed that the sustainable development of the world depends on GNSS. On more esoteric ground he stated that GLONASS had maintained stable operations in 2014 and three more satellites had bene launched. Further launches would depend on operational circumstances. The user domains for GLONASS were continuously expanding. Continuing the summit text he said that it was better [working] together than separately — in fact separately often doesn’t work at all and therefore we must continue to promote interoperability and the Munich Satellite Summit is a good forum for this.
Jianyun Chen of the China Satellite Navigation bureau also took up the theme of all GNSS together. Sixteen Beidou (pronounced — for the avoidance of doubt — as ‘bay-doe’) had been launched since 2007 and the Chinese had been in discussion with Russia to ensure full interoperability with GLONASS. This process will be repeated with GPS and Galileo.
GNSS Updates
One of the idiosyncrasies of the Munich Summit is its very discreet signage. If you don’t know where it is — and specifically the correct side door that brings you up two floors to the main Max Joseph Saal venue — it is highly likely you’ll miss it! But once you are in it is two full-on days of updates on systems and discussions on a vast range of topics that impinge on the development and implementation of GNSS around the world.
Discreet signage. Photo: GSA
The first two session of the summit proper gave updates on the GNSS systems in operation and under development as well as the regional and augmentation systems. Much of the material was slightly more detailed versions of presentations at the plenary but a few news snippet emerged.
“Stormy” Martin said that a modified battery charge control had been implemented that would extend operational life for some of the fleet by one or two years. He also reiterated the improving accuracy performance of GPS which was now much better that its published standards. He predicted that the first GPS III would be available for launch in 2016 and said that GPS was improving every day.
Eric Chatre from the European Commission reiterated that Galileo was still expecting to start early services in 2016 with full operational capability in 2020. He expected 18 satellites to be launched by 2018. The new Ariane 5 launcher will enable the launch of four satellites at one time and the first launch with this system would be in 2016. In terms of the ground segment only one station in the Pacific was yet to be established.
Sergey Karutin of Roscosmos talked about a four-fold accuracy improvement for GLONASS with the use of new clocks and the introduction of new CDMA signals that will improve accuracy and access. According to Dongfeng Yu of the China Satellite Navigation Office the BeiDou constellation is moving from “regional to global, active to passive” and is aiming for global coverage by 2020.
U.S. SBAS developments were covered by Deborah Lawrence of the Federal Aviation Administration (FAA). The Wide Area Augmentation System (WAAS) now has 100 percent coverage for LPV200 in CONUS. More than 41,000 runway ends are now included, and she predicted full completion in 2016.
Jean-Marc Pieplu of the GSA talked about EGNOS status. The next system release (2.4.1) should be published in Q3 2015 and will include a significant input on ionospheric corrections. Further service evolution includes a plan to declare LPV 200 in Q4 this year and EGNOS coverage will be extended to 72 deg North and ensure full coverage of the 28 EU member states.
The Russian Augmentation system SDCM performs at 0.8 metre accuracy according to Grigory Stupak of JSC / Russian Space Systems. He noted new validated SDCM ground stations had been established in Antarctica and Brazil and stated that global exploitation was a key objective for SDCM as its satellite coverage was very wide. GLONASS and GPS together could ensure complete coverage. He also indicated that work was in hand for SDCM SBAS service certification for LPV 200 and he called for providers of all WAAS to work closely together.
2020 Vision
After lunch we were offered the chance to hear some expert views on the future of GNSS and PNT with Prof Vidal Ashkenazi of Nottingham Scientific Limited asking for their vision of GNSS in 2020. By that year there should be 100-120 GNSS satellites in orbit, multi-constellation receivers would be the norm, but what would be the new applications and what were the challenges?
Jamming and spoofing would still be issues. Pierre Bouniol of Thales thought that in civil aircraft receivers would probably incorporate jamming indicators by 2020 to inform users when signals may be compromised. For Stuart Riley of Trimble the key was integration of other sensor signals to bridge any GNSS signal outage. Gang Mao of Unicore Communications Inc. in China considered multiple frequencies to be a big help in reducing the threat of jamming. Nigel Davies of QinetiQ agreed saying there were a host of technical solutions but key for success would be solutions that use low power, are low cost and feature high usability. He also noted that safety certification of receivers for use in driverless vehicles would be required and this challenging application would need the provision of robust continuous navigation — and sub-metre accuracy.
The future market for GNSS was also discussed in a session that unveiled the GSA’s 4th Issue of its comprehensive GNSS Market Report. With almost four billion GNSS devices used worldwide and all regions experiencing growth, GNSS represents an unprecedented business opportunity. Over the past 15 months the GSA’s team of market monitoring experts has taken a close look at all aspects of the GNSS marketplace with analysis of both hardware and software market opportunities, technology trends and future developments.
Gian-Gherardo Calini, Head of Market Development at GSA, gives highlights of the comprehensive GNSS Global Market report. He will deliver this information in an April 16 webinar hosted by GPS World. Photo: GSA
The top-line results were presented by Gian-Gherardo Calini, Head of Market Development at GSA. GNSS is one of the few growing markets in the world showing 12.7 percent CAGR. It is a very attractive market with volumes and revenues driven by mass market segments: the dominant two being Location-based services and transport applications. This latest edition includes information a new market segment: Timing and Synchronisation. One area that is not included is security and government applications. Mr Calini indicated that this information has been collected by the GSA team but as it is essentially for users of the Public Restricted Service (PRS) it was not included in the open report.
Although the report is very much “Galileo flavored,” its findings are of great importance and value to whole GNSS community and will be the subject of a GPS World webinar with Mr Calini and myself on 16 April. You can register — free — for this informative global perspective now.
A panel discussion followed and covered a range of topics and applications from aviation to agriculture. Again the consensus was that chips would become multi-constellation and quickly. Philippe Prats of STMicroelectronic outlined automotive applications from insurance applications to advanced driver assistance systems (ADAS).
The role of government mandates in establishing markets was seen as positive. The e911 mandate in the states had provided the seed for GPS integration into smartphones. Similarly authentication was also seem as a significant future market driver.
Multi frequency was also showing on industry’s radar and in a couple of years will be a reality thought Philippe Prats with the main motivation being better accuracy. Frank van Diggelen of Broadcom highlighted the recent GPS World feature demonstrating cm accuracy on a smartphone.
Legal Issues
A dedicated session on legal issues was not the best attended part of the conference, which is a shame as it had some serious points to raise and highlighted a gap that is opening up between our technical abilities in GNSS and the legal basis for its use. The Munich Summit is to be commended for its commitment to providing a platform for these issues every year; they are often ignored elsewhere.
Oliver Heinrichs, a partner at BHO Legal in Cologne, emphasised the need to establish a firm regulatory framework and to ensure that any decisions did not cross World Trade Organisation (WTO) provisions and the General Agreement on Tariffs and Trade (GATT). In particular the idea of mandating a specific GNSS for applications such as emergency response systems in cars may well be incompatible with WTO rules.
Amedeo Arena of Universitá degli Studi di Napoli Federico II in Naples noted that all GNSS players were members of the WTO and considered that GNSS services and their trade was definitely “caught by the GATTs” so no favouritism for ‘home’ systems should be allowed.
Another area of controversy is automated vehicles. In discussion after the session I learnt that current international conventions governing the use of motorised vehicles require a human supervisory role at all times. There will need to be some fundamental legal groundwork done before the first driverless vehicles will be allowed out on the road for real.
These are legally complex issues and certainty will only come from test cases. Talking of complexity Aleksey Bolkunov of the Russian Federal Space Agency revealed that the legal, regulatory and standardisation measures governing GLONASS and GNSS in Russia consisted of more than 900 documents originating at various different levels of the state. This clearly gave great scope for “regulatory collisions” and he is involved in work to develop a single regulatory framework that should eliminate the remaining barriers to GNSS use in Russia.
Emerging Applications
Peter Grognard of Galileo Services chaired a final session of the day on emerging applications. Bruno Bougard of Septentrio saw dependable accuracy as key to emerging markets. He thought high precision driven by surveying was becoming more and more mainstream. For autonomous driving the challenge was to provide cost-effective, dependable accuracy at 10-30cm that was safe, reliable, and always available. This would require multi GNSS, multiple signals, highly integrated sensors and transparent and open augmentation.
For Neil Gerein of Novatel the mantra is “Accuracy, availability, assurance.” Users needed availability to their PNT solutions at all times. He also saw future applications integrating GNSS with inertial sensors and correction systems for high accuracy without the need for a base station.
or Neil Gerein of Novatel the mantra is “Accuracy, availability, assurance.” Photo: GSA
Lionel Garin of Qualcomm Inc talked about ADAS. Safety was paramount and he foresaw the need for rigorous design and certification procedures similar to that required for the aviation market. Fortunately the industry has lots of expertise here. Philip Mattos of u-blox UK argued that a volume market is in femtocell and small cell synchronisation in mobile networks where GNSS is the lowest cost solution.
Tom Stansell praised geometry as the most important and unique ingredient supplied by multi constellation GNSS. And the second most important ingredient was interoperability. He doubted users would care where their signals originated and devices would still be generically described as ‘GPS’ into the future. Application growth will be stimulated by the better geometry supplied by multi-GNSS constellations. When the E6 signal became available he predicted that 10cm accuracy would enable reliable lane keeping for ADAS.
And Galileo will supply E6 for free said Ignacio Fernandez Hernandez from the European Commission. Ignacio works on the Galileo Commercial Service design and outlined some significant differentiators of the European system including its broad signal for high accuracy and better multipath resilience, more stable clocks and improved ionospheric modelling compared to GPS.
Lionel Garin sounded a note of caution at the end of the session when he noted that multi constellation ability was good, but he was not sure what was actually gained beyond two, or perhaps three, constellations.
GNSS for Weather
The final day of the conference saw a few fragile heads courtesy of the previous evening’s Summit Space Night 2015 sponsored by Airbus Defence & Space, which took place at the Filmcasino am Hofgarten close to the conference venue. And the first session, chaired by Oliver Montenbruck from the DLR, certainly required a clear focus as we were taken through the use of GNSS in space geodesy, space navigation and reflectometry.
Roland Pail from the Technical University, Munich described results from the satellite gravity missions GRACE and GOCE that looked at mass transport processes on our dynamic Earth. A particularly sobering animation showed the extent of ice mass loss from Greenland over the past decade. But what is role of gnss here? The ability to give precise positioning of the satellites and the fact that the satellite orbits carry information on the gravity field.
Atmosphere sounding using GNSS radio occultation allows precise atmospheric profiles with global coverage in all-weathers. Jens Wickert of the Helmholtz Centre Potsdam said that since 2006 these high vertical resolution profiles had been making a significant impact on the world’s weather forecasting including improved hurricane forecasts. It was also a bias free technique for observing global temperature change. With a multi-GNSS future new missions could be planned as more signals would reduce noise. Combining GNSS and reflectometry could enable accurate tsunami detection from space. Similarly Prof Antonio Rius from Barcelona was using reflected GNSS signals to determine data on the surface of the sea such as surface roughness, extent of sea ice and early warning of a tsunami.
Stefan Sassen of Airbus Defence & Space described the LION GNSS navigation receiver for MEO and LEO platforms. The unit was qualified since 2014 and now 50 were on order. LION is highly flexible with multi-frequency, multi-constellation and multi-antennae configurations possible. It was accurate enough for autonomous orbit raising (a few kms) and or station keeping (to within 100cm).
Finally Manfred Sust of RUAG Space GmbH said that space borne gnss receivers were true enabling technologies for Earth Observation missions as precise orbit determination was key to capturing sharper images.
Alternatives
The second session of the day returned to the practical issues around possible alternative or complementary PNT (APNT) systems. As GNSS becomes ubiquitous many terrestrial PNT systems are being decommissioned (LORAN, VOR), but the potential vulnerability of GNSS signals to interference is highlighting the need for backup. The challenge being to balance functionality and cost in the search for “plan ‘B’ for GNSS” as chairman Michael Meurer from DLR described it.
The FAA’s Deborah Lawrence reiterated her plans for scoping and implementing a backup system to cope with a GPS outage in the US. The FAA is currently engaging with stakeholders to define what the minimum operational target for a GPS outage should be to set the basis for procurement activity. The timeline for a final investment decision was now December 2018.
For Europe Gerhard Berz of Eurocontrol thought there were many potential APNT in place and the topic was in the SESAR 2020 research programme. He thought existing DME could potentially do the job in Europe as it had good coverage, but the challenge is to get good geometry and coverage at low altitudes, in remoter areas and over water.
Prof Per Enge of Stanford University “put the moose on the table” and pointed to the 978 and 1030 ranging frequencies as an existing system that could be used for positioning. But how accurate was it? Airborne experiments had shown good agreement with GPS positioning with an accuracy of around 100m and in turns 300m, which was good enough in an emergency. Further tests using a UAV at spider infested Camp Rogers had demonstrated APNT in flight with 50m error. The UAV itself was specifically developed to navigate using APNT while looking for GNSS jammers.
Wouter Pelgrum of Ohio University discussed the relative merits of eLORAN, which has high power – and therefore difficult to jam – and beyond line of site accuracy of less than 10m, and alternatives such as collocation of pseudolites with mobile phone cell towers. This could also enable high accuracy indoors positioning applications. He believed that APNT will need to be context specific and there was no single solution.
Belabbas Boubeker of the DLR discussed modular APNT concepts while Nick Ward of the UK’s General Lighthouse Authorities indicated there was no coordinated policy on resilient PNT in the European maritime sector at present but his authority and others were exploring the possibility of using eLORAN as a commercial enterprise. Nine transmitters were operational in Europe and the service had been declared in 2014.
Michael Hoppe of Fachstelle der WSV für Verkehrstechniken said resilient PNT was a core element of e-navigation for waterways. A combination of techniques such as medium frequency RF, AIS and eLoran could give good accuracy in areas of highest traffic. First results of trials were encouraging.
Processing Power
The final session of the Summit to grab my full attention was chaired by Frank van Diggelen of Broadcom. He led a wide ranging debate on GNSS receiver architecture trends and more generally the future of chip design and fabrication: are we approaching the end of Moore’s law and if so — what next?
Recently “The balance of power has moved back onto the GNSS chip” to enable lower device power use. To highlight current developments Frank described a couple of Broadcom products: the Broadcom 4773 “location hub” that is at the heart of the Samsung Galaxy 6 “super smart phone” and the 4774 that can access signals from all four GNSS constellations and will be shipping in early 2016 on new smartphones.
In fact earlier this year the 4774 was used to make a first fix using signals from four different GNSS constellations (with signals from one each of GPS, GLONASS, Galileo and BEIDOU satellites) and a significant event in terms of our multi-constellation future.
Greg Turetzky of Intel talked about the benefits and challenges for GNSS in advanced silicon processes. He noted that Intel is now shipping 14nm technology and plans were in hand for the next two generations (10nm and 7nm). Moore’s law has been a great enabler for modern society. If automobiles had taken a similar development in the same timeframe we would all be driving cars with a maximum speed of some 300 000 km/hour that cost us around 4 cents to buy!
The big challenge for GNSS architecture was to take advantage of the smaller geometries while greatly reducing standby power. The integration of multiple radio sources to provide a single location solution was key giving ubiquitous location capability that will improve the experience of every mobile product.
Looking into his crystal ball, Peter Anderson of Integrated Navigation Systems in the UK saw that integrating signals from complimentary technologies and sensors would be important but would lead to a greater demand for digital processing. He predicted that multiband receivers would become standard in consumer devices. He also pointed out that the worst potential source of GNSS jamming for a smartphone was the phone itself! The move to dual frequency would be helpful here.
An overview of the Chinese XIHE system for seamless outdoor and indoor location was given by Dongkai Yang of Beihang University. This Beidou Innovative application provides a LBS system based on gnss and mobile communication networks to give a “fusion of communication and positioning for indoor positioning”. The system is being demonstrated in four areas in China in shopping malls. The target for positioning accuracy in the system is for less than 3 metres indoors and less than 1 metre outdoors.
Franz Kreupl of Munich Technical University gave a sobering view of “life after silicon” – essentially it looks like there isn’t one. He outlined the limits to silicon technology such as tunnelling current and predicted some further progress could be made in reducing interconnect sizes and via circuit design. But new candidate materials for semiconductor electronics from carbon nanotubes to widely hailed 2-D materials graphene and MoS2 all suffer major issues that seem to make them non-starters.
But do we need to keep on miniaturizing? Norbert Schuhmann of Fraunhofer IIS in Nuremberg thought that technology downscaling would have an end in terms of the physics, but especially in terms of reasonable cost. He thought 7nm and 2020 was the end point for the physics but that in fact 28nm should be seen as the actual last node in Moore’s law as from then scaling has no longer also been the path for cost reduction. He saw silicon on insulator technology and monolithic 3-D integration as possible paths forward, but the technology sweet spot — and well suited for GNSS — was 55nm and a format that was already extensively used in automotive applications.
A patch for the upcoming GPS satellite launch shows a stylized GPS IIF-IX formed by the Delta 4 rocket and the constellation Cygnus (Latinized Greek word for swan). The satellite is nicknamed Deneb, the brightest star in the constellation and one of the 57 stars used in celestial navigation. The patch also indicates that the satellite is SV-10 and 71. The SV-10 identifier may indicate that it is the 10th satellite off the IIF assembly line. Photo: US Air Force
The U.S. Air Force’s ninth GPS Block IIF satellite (GPS IIF-9) is set to launch Wednesday at 2:36 p.m. EDT (1836 GMT) from Space Launch Complex 37 at Cape Canaveral Air Force Station, Fla.
The GPS IIF-9 will ride aboard a United Launch Alliance (ULA) Delta IV rocket, marking the 29th Delta IV launch and the 57th operational GPS satellite to launch on a ULA or heritage launch vehicle.
GPS IIF-9 is one of the next-generation GPS satellites, incorporating various improvements to provide greater accuracy, increased signals, and enhanced performance for users.
UPDATE (April 17, 2015): The USCG Navigation Center has confirmed that SV-10 was launched instead of SV-9. The Air Force discovered a problem with SV-9, so it was pulled from the launch and SV-10 was sent into orbit in its place. SV-9 will be used in a future launch.
Constellation Changes. The Air Force Second Space Operations Squadron (2 SOPS) indicates that IIF-9, SVN-71/PRN-26, will replace SVN-35 (currently being operated in Launch, Anomaly Resolution and Disposal Operations [LADO]) in the B plane slot 1F. SVN-38/PRN-08 will be taken out of the operational constellation prior to SVN-71 payload initialization and sent to LADO. PRN-08 will be assigned to SVN-49 in May and set to test, but is tentatively scheduled for assignment to IIF-10 to launch June 16. SVN-35, launched on August 30, 1993, has been in a residual status since March 2013 in an expanded node slot in the B plane and successfully served 21.5 years, 14.0 years beyond its designed service life, due to the diligent efforts of the men and women of the U.S. Air Force. SVN-51 is still in a re-phase journey from E1 (GLAN=146 °) to an auxiliary node at E7 (GLAN=60.7 °) scheduled to arrive sometime this summer.
A quarterly meeting of the U.S. GPS Program’s interagency Civil Navigation Signals (CNAV) Tiger Team on March 5 focused on the new L2C and L5 GPS civil signals. “CNAV Message Types 10, 11, 30 and 33 are currently transmitted on seven GPS IIR-M (L2C) and eight GPS IIF satellites (L2C and L5),” wrote Rick Hamilton, CGSIC Executive Secretariat, USCG Navigation Center, in a status email to the Civil Global Positioning System Service Interface Committee (CGSIC).
“A Modernized Navigation (MODNAV) Tool integrated with the GPS ground control software (Architecture Evolution Plan or AEP) is generating the CNAV data messages,” Hamilton wrote. “Daily CNAV uploads began December 31, 2014, and the U.S. Air Force reports that signal performance of CNAV matches or slightly outperforms Legacy performance: average user range error (RMS URE) from 25 February – 3 March 2015 was 0.50 m for Legacy and 0.57 m for Modernized; best week for Modernized signals since the broadcast initiated April 2014 was 0.42 m for 6 – 13 January 2015.
The graph above, from the Coast Guard Navigation Center website, illustrates the CNAV performance.
“Users are reminded that these CNAV signals are ‘pre-operational’ and should be used with discretion until they become fully operational; the L5 message is currently set unhealthy,” Hamilton concluded.
The U.S. Air Force’s ninth GPS Block IIF satellite (GPS IIF-9) has been encapsulated in the Delta IV rocket’s four-meter-diameter nose cone at a processing facility, and moved to the launch pad at Space Launch Complex 37 for mating to its booster inside the mobile service tower.
Launch is scheduled for March 25 at 2:36 p.m. EDT (1836 GMT) from Space Launch Complex 37 at Cape Canaveral Air Force Station, Fla. GPS IIF-9 marks the 29th Delta IV launch and the 57th operational GPS satellite to launch on a ULA or heritage launch vehicle.
To follow the launch countdown, dial the ULA launch hotline at 1-877-852-4321 or join the conversation on Facebook, Twitter or Instagram.
The planned GPS IIF-9 launch trajectory, event times, and ground trace. (courtesy of ULA)
Below are photos from the United Launch Alliance, which supplies the Delta IV rocket and serves as the launch provider for the GPS Directorate.
The U.S. Air Force launched the eighth GPS IIF satellite from Cape Canaveral Air Force Station in Florida today at 1:21 Eastern Time, as scheduled. An Atlas V 401 carried the GPS satellite aloft.
GPS IIF-8 is one of the next-generation GPS satellites, incorporating various improvements to provide greater accuracy, increased signals, and enhanced performance for users. With this eighth satellite now launched, only four more Block IIF satellites remain to be placed into orbit. Three are in storage awaiting launch, and one is in production.
“I’m delighted with the outcome of today’s launch. Thanks to the men and women of SMC, the 45th, 50th and 310th Space Wings; Boeing; ULA; the Aerospace Corporation; and the GPS IIF and Atlas V launch teams ceaseless efforts, commitment, dedication, and focus on mission success, we successfully launched the fourth GPS IIF space vehicle this year,” said Col. Bill Cooley, director of Space and Missile Systems Center’s Global Positioning Systems Directorate. “Today’s launch demonstrates our commitment to users around the globe that GPS is the gold standard for position navigation and timing and will continue to deliver capabilities for the foreseeable future,” he said.
After launch, the mission entered a coast phase that lasts about three hours. Following a short second burn of the RL10 engine, the Centaur second stage will deliver the Boeing-built GPS IIF-8 satellite to semi-synchronous orbit over the southern ocean north of Antarctica. Separation takes place about 3 hours, 24 minutes after liftoff.
GPS IIF-8 is the United Launch Alliance‘s fourth GPS launch this year. The mission marks ULA’s 89th mission launched since the company was founded in 2006.
GPS IIF-8 (SVN-69/PRN-03) will replace SVN-51 in the E plane slot 1. SVN-51 will be re-phased from E1 to an auxiliary node at E7 somewhere around SVN-54 currently on station at E4, according to the Air Force Second Space Operations Squadron (2 SOPS). SVN-38/PRN-08 will be taken out of the operational constellation prior to SVN-69 payload initialization and sent to Launch, Anomaly Resolution and Disposal Operations (LADO). PRN-08 will be assigned initially to SVN-49 and set to test.
SVN-38 was launched on November 5, 1997, successfully serving nearly 17 years, 9.5 years beyond its designed service life, due to the diligent efforts of the men and women of the U.S. Air Force. SVN-51 will remain in an auxiliary node once it completes its re-phase journey. The SVN-51 re-phase will take about six months after the initial burn occurs.
The Air Force is set to launch the eighth GPS IIF satellite from Cape Canaveral Air Force Station in Florida on October 29. The 18-minute launch window opens at 1:21 p.m. EDT.
An Atlas V 401 will launch the GPS IIF-8 mission for the U.S. Air Force.
As described by the Air Force, GPS IIF-8 is one of the next-generation GPS satellites, incorporating various improvements to provide greater accuracy, increased signals, and enhanced performance for users.
GPS IIF-8 will be United Launch Alliance’s fourth GPS launch of 2014 and the 12th of the year. The mission will mark ULA’s 89th mission launched since the company was founded in 2006.
To keep up to speed with updates to the launch countdown, dial the ULA launch hotline at 1-877-852-4321 or join the conversation at www.facebook.com/ulalaunch and twitter.com/ulalaunch; look for the #GPSIIF8 hashtag.
The Air Force Second Space Operations Squadron (2 SOPS) indicates that IIF-8, SVN-69/PRN-03, will replace SVN-51 in the E plane slot 1. SVN-51 will be re-phased from E1 to an auxiliary node at E7 somewhere around SVN-54 currently on station at E4. SVN-38/PRN-08 will be taken out of the operational constellation prior to SVN-69 payload initialization and sent to Launch, Anomaly Resolution and Disposal Operations (LADO). PRN-08 will be assigned initially to SVN-49 and set to test.
SVN-38 was launched on November 5, 1997, successfully serving nearly 17 years, 9.5 years beyond its designed service life, due to the diligent efforts of the men and women of the U.S. Air Force. SVN-51 will remain in an auxiliary node once it completes its re-phase journey. The SVN-51 re-phase will take about six months after the initial burn occurs.
