GPS World

Tag: Don Jewell

  • In memoriam Don Jewell, 1949–2016

    don_jewell_4cFriends and colleagues of Don Jewell have sent these messages on learning of his unexpected passing in October. Below is a collection of memories and appreciation from readers and friends of Don.

    To add your tribute, send to [email protected].

    His is truly a loss for the entire GPS community.

    He will be greatly missed. Like a Brother.

    With great sadness I just learned of the passing of my Mentor and Friend Don Jewell.

    He was the voice of the Warfighter and would always talk to the troops and get their input of the many devices he would review. Much to many manufacturers chagrin he published those against their glowing reviews.

    Don and I became friends during my time at Trimble Navigation.
    He became my mentor and my friend.
    For 1 interview and demonstration of products he had me up for lunch in his house in Colorado Springs. I ended up being there for hours.
    I especially enjoyed his company after I left Trimble and I became his escort at Trimble Dimensions in Las Vegas. It was there I introduced him to Tweeting.
    He thought that was the funniest thing!

    Don will be missed and I hope someone steps up to take his place as a technological voice of the Warfighter.

    unknown-1There are many men of talent and ability. There are many men of accomplishment. Many, too, of experience.  There are fewer men of integrity, and even fewer who combine all of these things with humor and friendship. This is what made Don Jewell a rare and unique friend and colleague.  While it is natural to mourn that his time among us is ended, there is also an undercurrent of joy that we shared time together.

    Don was a real pillar for the PNT community and consummate spokesman for the truth, always offering constructive criticism where needed. An exemplary personality who always ‘did the right thing.’

    Don was  quite active as a volunteer in the Military Division of the Institute of Navigation (ION). From 2010 through 2015, he and I worked together to assemble and co-chair the Warfighter Crosstalk Panel in the Military Division’s annual Joint Navigation Conference (JNC), which was then and remains today one of the most interesting and informative sessions of that conference. It focused on needs of military and first responder users for positioning, navigation, and timing (PNT). We would ask potential panelists to speak freely about their experiences with PNT to support them in operations – what has worked well, what has not worked so well, and what they would truly like to have … then we would tell them to focus on the latter two. The panel was always a big highlight of the conference. Don’s popularity within the community helped us attract some great panelists.

    We often traveled together, and it was during our off hours when the work was done that we would relax and chat over a meal. Don was passionate about family, particularly his wife Linda and daughter Dawn. When talking about good times with family, there was always a sparkle in his eyes, incredible joy and pride. Whenever we would have meetings in the Colorado Springs area, he and Linda would invite the team members to their home for an evening get-together, a great way to relax after intense work. Whenever he would come to IDA for work, he would swing by offices of the colleagues and friends he had made over the years, just to say hello.

    Rest in peace, Don, and know that you made a big difference for so many in this world — indeed you did for me.

    Don was one of those rare individuals that you just wanted to spend hours with listening to his take on life. My big regret is that I couldn’t have more of those hours.

    His use of PNT as a vehicle for constant improvement was driven by Don selflessly serving our National Security through helping our soldiers, sailors, marines, and airmen and others operating in harms way to serve our country well in his passionate and very candid role with his “Constructive Criticism” counsel to Air Force and DoD leadership to assure the troops mission success, returning home safely often after intense combat.
    A tragic loss to our Nation, as he did this for many, many years.

    As a vocal and outspoken  member of the AF Space Command GPS Independent Review Team, Don was a key player in all the tasks undertaken to respond to tasking by the Commander Space Command.

    One of many significant roles was to be the key IRT debriefer of warriors returning to the US through Ft Carson following operational deployments to get candid inputs on what shortfalls in PNT they had using GPS to execute their missions, so that Don could make sure DoD leadership didn’t get complacent in management and operation of GPS.

    unknownI’m glad I had the pleasure of meeting him. Really nice guy.

    Don was a very kind man and very supportive when I worked with him. This is very sad news.

    He held tremendous respect in the GPS Control Segment community.  Many of us were regular readers.

    We’ll all miss him.

    Sad news. I’m sorry to hear this. It was always a fun conversation with him and was one of the reasons I looked forward to attending ION. Our one hour lunch get-togethers would always turn into 2+ hours.

    He was such a nice guy, and fun to work with.

    We lost a wonderful friend.

    May I respectfully suggest advocacy for naming the GPS AMCS at Vandenberg as the Don Jewell GPS AMCS.

    I know that would bring a smile every time I heard or read of this honor to Don’s and his world-wide contributions to GPS/GNSS across all segments of navigation and for his service to our nation.

    I suspect Don would have been humbled by this well deserved honor.

    I will miss Don, and the opportunity for more occasional chats.  I suspect many others will as well and I hope will endorse this recognition.

  • In defense of PNT: Multi-GNSS to the rescue

    In defense of PNT: Multi-GNSS to the rescue

    An artist's concept of a GPS IIR-M satellite in orbit (courtesy of Lockheed Martin).
    An artist’s concept of a GPS IIR-M satellite in orbit (courtesy of Lockheed Martin).

    For more than 41 years, many of us who were there in the beginning have been discussing the attributes, capabilities, enabling features and shortcomings of GPS and other space-based PNT (position, navigation and timing) systems. You have likely heard most of them; historically they go something like this:

    • The signal is weak.
    • The signal is easily jammed.
    • The signal can be spoofed.
    • The signal is subject to atmospheric perturbations.
    • The signal doesn’t penetrate buildings.
    • The signal doesn’t penetrate dense canopies (urban or natural).

    I am sure you have heard most of these. Now, allow me to update the situation with some of the developments enabled by modern signals, new techniques, and multi-frequency, multi-GNSS (Global Navigation Satellite System) “all-in-view” receivers. All of the above bulleted statements are still true, but to a lesser extent, virtually each day. As some well-known pop musicians once sang, “It’s getting better all the time.”

    • Today,  multi-GNSS signals in a fully modern multi-GNSS receiver can to some degree resist interference — intentional (jamming) or unintentional — and  spoofing. It is extremely difficult for a jammer or spoofer to disrupt GPS, GLONASS, Galileo and BeiDou all at the same time. And more help is on the way.
    • Today, multi-GNSS signal corrections remove a large amount of error due to atmospheric perturbations and can sometimes deliver centimeter and millimeter accuracy in real time (in the case of short-baseline real-time kinematic (RTK) using only L1 carrier-phase as data, and/or in some other special situations.)
    • Today, multi-GNSS signals and augmentation signals show some improvement in penetrating dense canopies and canyons by virtue of their multiplied numbers and dispersed geometry.
    • Today, new ground-based technologies show promise at penetrating buildings to provide indoor location. When combined with GPS/GNSS, this is starting to get us closer to the Holy Grail, the ubiquitous PNT solution.

    Debate

    The future looks bright for PNT solutions, ground and space-based. I know it all sounds like a debating society, and you may have heard some of these arguments before. My point, my premise if you will, or bottom-line-upfront in military parlance, being: the GPS (space-based) limitations of the past are gradually giving way to the improved multi-GNSS capabilities of today and the combined ground-based and space-based PNT technologies of the present and rapidly arriving future.

    Unfortunately, there are many uninformed so-called PNT pundits who love to posture for the press — and who are living in the past. The future is right in front of them, or in many cases in their hands, and they cannot or will not acknowledge its existence.

    It’s all in the numbers

    Current estimates are that more than 4 billion users depend on PNT daily for position, navigation and timing, or the multitude of services each of these resources enables. More than half of that number is attributable to smartphone users, which means, at a minimum, more than 2 million PNT users have a two-way communications device incorporated into their PNT receiver/sensor.

    Let’s look at current high-end smartphones as examples of commercial multi-frequency, multi-GNSS “all signals available” devices. The user has a true multi-GNSS device incorporating:

    • GPS — Global Positioning System, United States government
    • GLONASS — Globalnaya Navigazionnaya Sputnikovaya Sistema, the Russian space-based PNT system
    • BeiDou — the Chinese BeiDou Navigation Satellite System, a regional system now, soon to be global (2020 the advertised date).

    with augmentations such as

    • WAAS — U.S. Wide Area Augmentation System
    • EGNOS — European Geostationary Navigation Overlay Service
    • Other SBAS — additional Satellite-Based Augmentation System signals by region
    • Wi-Fi — Signals compatible with a set of broadband wireless networking standards.

    The latest high-end smartphones incorporate an inertial system, a digital compass, a rate gyro, and a pressure sensor integrated with pedometer software that keep track of position, heading and velocity when  external signals are lost. Add cellular tower and network-enabled positioning and timing technology, and you have a two-way communications and PNT-based multi-GNSS sensor that, as long as it has power, is never lost.

    Atomic numbers

    The rubidium-based (atomic-reference system) timing signals from GPS satellite vehicles (SV) are among the most stable timing frequencies ever broadcast from space. The true accuracy of the signal in space is classified, but approaches an accuracy 10 times better than what was once thought to be adequate for our warfighters.

    The best clocks in any current GNSS system are the passive hydrogen masers of Galileo. Thus a PNT set-up that adds Galileo to GPS improves in more ways than one.

    Ephemeris numbers

    Twenty-five years ago, the U.S. military kept track of GPS satellite orbit locations (known as the ephemeris of the satellite) using actual GPS measurements at the control segment tracking stations. The GPS satellite ephemeris was known to a much lesser degree of accuracy than now. At the time, that accuracy was  considered good enough.

    Today, the ephemeris is known much more precisely, and this can be on the order of some centimeters. This has to do with not only the location of the satellite’s center of mass (c.o.m.), but the actual location from which the signal is broadcast. The position of the satellite’s broadcast antenna is known reasonably well most of the time, by very high-end users, after correcting for the arm lever between the c.o.m. and the antenna phase center. The c.o.m. itself can vary by some centimeters over time because of depletion of onboard expendables, but here we are getting into very high-order minutiae.

    Suffice it to say that certain multi-GNSS scientific high-precision receivers today are used to measure tectonic movements on the order of centimeters over the course of a full year.

    Number of signals

    Just recently, with the addition of certain QZSS signals (the Japanese Quasi-Zenith Satellite System) along with the Indian (GAGAN) and Russian (SDCM) equivalents of WAAS and EGNOS, the number of multi-GNSS PNT signals available to a truly international multi-GNSS receiver exceeds 200. For example, one set of global commercial receivers routinely receive and process more than 190 PNT signals in a six-hour period. The receivers are both static and dynamic, and they are networked. The static receivers know their actual location to within millimeters, and use this location as a truth set from which all other signal data is compared.

    Accuracy numbers

    For our example (and all parameters are software-defined and user-programmable), the location parameter may be set at 10 centimeters, meaning that any position derived from PNT signals or augmentations that differ by more than 10 centimeters from the “truth set” are immediately rejected, and that data is broadcast on the systems network, which keeps the dynamic receivers in sync as well.

    The individual receivers each contribute to their own and a networked website with metadata usable by Kalman filters to which other users may choose to subscribe. This makes the multi-GNSS receivers not only receivers, but system and PNT monitors and sensors that can detect  jamming, interference and spoofing attempts, which are reported.

    This monitoring and tracking system is constantly evolving and incorporating new technologies while becoming more secure everyday. This is not a totally new concept, as the core system is a mature enterprise system that has been in operation and commercially viable for more than seven years.

    This should be comforting information for those of you who stay up at night worrying about the safety of autonomous vehicles on land, sea and in the air.

    Don’t let me give you the impression that GPS is just waiting around for other GNSS to come to its aid. GPS is aggressively modernizing itself. In Air Force parlance, “GPS III space vehicles will introduce new capabilities to meet higher demands of both military and civilian users.” As stated by GPS III contractor Lockheed Martin, the modernized system will:

    • Deliver signals three times more accurate than current GPS spacecraft.
    • Provide military users up to eight times improved anti-jamming capabilities.

    Augmentations and improvements

    The bottom line is that a greatly increased number of space-based PNT platforms — along with quantum improvements in computing power, cheap non-volatile memory and software-defined capabilities — have produced a multi-GNSS PNT capability that increases availability via sheer numbers, with more security and reliability on the way.

    A pair of LocataLite transmit antennas overlook a section of the White Sands Missile Range blanketed by the Locata high-precision ground-based positioning system.
    A pair of LocataLite transmit antennas overlook a section of the White Sands Missile Range blanketed by the Locata high-precision ground-based positioning system.

    We are rapidly developing a PNT system that goes far in countering the naysayers. It takes advantage of augmentations and complimentary systems such as newer versions of Loran, (Long-Range Navigation System) and local PNT implementations such as Locata, just to name a couple of examples.

    These ground-based systems are critical to the future of PNT, and have very strong signals. For instance, eLoran is extremely difficult to jam, if not actually unjammable. If a monstrous sunspot were to temporarily knock out the majority of space-based systems, the ground-based systems would more than likely still be available, if — big if here — they are fully developed. At the moment, this is not a sure thing. It is a work in progress.

    Ground-based augmentations and complimentary/backup systems can in the future add a level of security for GPS and other space-based PNT systems: Why bother trying to knock out these space-based systems when there is a suitable and readily available ground-based system as a backup?

    The U.S. government maintains a number of monitor stations around the globe. However, it has not historically taken advantage of the incredible capabilities of multi-GNSS receivers and sensor technology. Although NASA and other U.S. non-military agencies have been involved with multi-GNSS — specifically the Russian GLONASS — for the past 20 years or so, the use has not been widespread. Fortunately, recent changes now permit multi-GNSS receivers for government users, including the military, in certain non-targeting activities, and the government would do well to take advantage of the changes. The good news is that the majority of the capability is in the receiver design, a capability on which the current director of the GPS Directorate at the Space and Missile Systems Center (SMC) “made his bones.”

    To all those critics who take every opportunity to denigrate space-based PNT, both inside and outside the government, I say: Pay attention to multi-GNSS. Stop your diatribes, because the future is arriving. Secure space-based PNT systems are here to stay.

    They continue to improve and become more secure as they incorporate space- and ground-based augmentations, new PNT technologies, software-defined capabilities, multi-GNSS signals, and enhanced computing.  “It’s getting better all the time.”

    Allow me to repeat myself all over again. Space-based PNT is here to stay.

    Until next time, happy navigating, and remember: GPS is brought to you free of charge by the United States Air Force.

  • The Internet of Everything: It’s All in the Timing

    40th Annual NIST Time and Frequency Metrology Seminar

    There were four of us, mature males who all remember having a crush on Annette Funicello, were seated around a table avidly discussing deviant behavior with a sometimes rapt mixed-gender audience. The four of us, loudly discussing deviant, and only occasionally aberrant behavior, were doctors: David Allan the world renowned creator of Allan Deviation or variance fame, Judah Levine, world renowned nuclear physicist and Father Time of NIST (National Institute of Standards and Technology), Neil Ashby, former chair and currently Professor Emeritus of Physics at UC Boulder, also from NIST, along with yours truly representing GPS World magazine and the Institute for Defense Analyses. Our ever-changing audience was composed of the 40+ members from around the globe attending the 40th Annual NIST Time and Frequency (T&F) Metrology Seminar, held June 2-5 in stunningly beautiful Boulder, Colo.

    Of course, the numerous deviant behaviors under discussion had more to do with the sometimes-fickle performance of various atomic reference systems than they did anatomy. And we were speaking loudly because that is what most men of our age do. Dr. David Allan frequently threw in quotes and anecdotes from his recently published book on time, It’s About Time, about which you will read more later.

    The NIST T&F Metrology Seminar is truly one of a kind, easily the best in the world for time and frequency metrology. I have been fortunate enough to attend numerous times. I can truly say I have never found it repetitive or boring. There are so many exciting discoveries concerning time, which David Allan staunchly maintains is a purely human construct, and how time applies to our everyday lives, especially to GPS — all PNT systems actually — that it is impossible not to be constantly fascinated.

    NIST Mission

    NIST Boulder is all about research and development for timing standards, which is a benign way of saying NIST SMEs (subject matter experts) are the world’s foremost authorities on time and metrology. To wit, NIST has produced no less than four Nobel Prize winners in metrology, the last being awarded in 2012. The atmosphere at NIST and the University of Colorado Boulder campus is such that you can’t help but feel certain there are more Nobel Prizes for NIST on the horizon.

    David Howe (Ph.D.), my NIST host and group leader of the Time and Frequency Metrology Division, explained that his organization, which sponsors the seminar, is an operating unit of the Physical Measurement Laboratory of the National Institute of Standards and Technology (NIST), an agency of the U.S. Department of Commerce. The NIST T&F Division is located in Boulder at the NIST Boulder Laboratories, just across from the street from the University of Colorado. Many of the NIST researchers are also University of Colorado professors, adjuncts or graduate students.

    The NIST mission includes:

    • Maintaining the primary frequency standard for the United States
    • Developing and operating standards of time and frequency
    • Coordinating United States time and frequency standards with other world standards
    • Providing time and frequency services for United States clientele
    • Performing research in support of improved standards and services

    Precise time and frequency information is required by electric power companies, radio and television stations, telephone companies, air traffic control systems, participants in space exploration, computer networks, scientists monitoring data of all kinds, and navigators of many types. These users need to compare their own timing equipment to a reliable, internationally recognized standard. NIST provides this standard for the United States.

    Of course one of the largest distribution networks for timing data is through the Global Positioning System (GPS), which provides this data globally to more than 4+ billion users and millions of timing systems everyday, numerous times per day. The number of times GPS time is utilized per day is almost impossible to calculate, but most certainly resides in the trillions.

    The NIST Time and Frequency distribution system delivers NIST Internet time over the Internet at the rate of 8 billion requests per day from servers at 25 locations across the United States.

    The frequency stability provided by classic Cesium and Rubidium atomic reference systems onboard GPS payloads have historically been on the order of 1 x 10-14. While this is the stability provided by the GPS IIF rubidium clocks, currently the rubidium clocks being prepared for GPS III are achieving frequency stability on the order of 1 x 10-15 under laboratory conditions, an order of magnitude better than the current on-orbit clocks.

    This is actually an amazing feat. For those of you who don’t deal in scientific notation on a daily basis, this means — since it is on a logarithmic scale — that the frequency stability of GPS III’s atomic clocks have the potential to be 10 times as stable as the IIF clocks, which are currently the most stable and accurate GPS clocks on orbit to date.

    Where atomic reference systems are concerned, we routinely speak of frequency stability and not clock accuracy. It is the stability over measured epochs, short and long, that matters most. Indeed, it is the oft-misunderstood frequency stability uncertainty expressed as delta f/f = 1 x 10-16 that produces the clock accuracy to within one standard (SI) second in three hundred (yes, 300) million years — a statistic that is obviously not directly observable, but reasonably predictable. Hence, as Judah Levine often says, where stability is concerned you are an historian, but where accuracy is concerned you are a prophet. NIST defines an SI second as the duration of 9,192,631,770 cycles of the cesium hyperfine transition.

    Tom O’Brian, the current chief of the NIST Time and Frequency Division, explained that this level of precision is equivalent to measuring the distance from the Earth to the Sun, a distance of 150 million kilometers, to the uncertainty of 15 microns or 1/10 the thickness of a human hair. While that is impressive, the best is yet to come. NIST is currently working on research-grade optical clocks, which we could reasonably expect to see on orbit one day in future GPS payloads, with an optical frequency stability equivalent to delta f/f = 2 x 10-18 or accuracy equal to 1 second in 15 billion years. Again this is the equivalent of measuring the distance from the Earth to the Sun to an uncertainty of 0.3 micron or the size of a virus.

    So What?

    Many of you may be asking why, as a GPS user, or merely as a user of technology, you should care about accurate and stable time reference systems. Marc Weiss, a long-time acquaintance and noted researcher at NIST (now in semi-retirement), very eloquently put his thoughts about time in an introduction to a recent timing white paper*, which has been slightly edited for length, current trends and readability. [Ed. So as to not be accused of putting words or opinions in the authors’ mouths, we have provided a reference for the unedited paper at the end of the referenced section]. Marc and several other metrology luminaries express their feelings concerning the future of time and why we should all care:

    We stand at the advent of a revolutionary new economy fueled by the global Internet of Everything (IOE). The IOE is a combination of traditional telecom systems with a growing need for wireless technology, and the emerging Internet of Things (IOT) including Machine-to-Machine (M2M) technology. Several current technology providers predict there will be a trillion global endpoints connected to the Internet by 2022, with $14.4 trillion in value at stake.

    One fundamental enabler of this revolution is a marriage of timing signals and data that breaks through existing barriers. Currently, optimal use of data in computing and networking is anathema to optimal use of timing signals. Computer hardware, software and networking all isolate timing processes, allowing the data to be processed with maximum efficiency due in part to asynchrony. Yet, the coordination of processes, the time stamping of events, latency measurements and optimal use of precious spectrum are all enabled by ever more accurate and stable timing.

    Timing is critical for the future development of and improvements to several high-value applications. For example, in smart transportation systems the exchange of information between vehicles, highways, and civil authorities depends on a robust ubiquitous timing system to ensure the rapid, accurate synchronization and provenance of data. Similar requirements are found in the operation of power grids, especially now that wind farms, solar arrays and the like require different control strategies, which are a critical part of the system. Modern medical applications such as tele-surgery and real time integrative online medical conferences, as well as applications in financial systems are all important examples that require accurate and stable timing signals and may well affect us all.

    There are three different types of timing signals for dependable synchronization: frequency, phase, and time. Frequency can be supplied by an individual clock, such as a commercial (atomic) Cesium or Rubidium standard, though practicality drives the use of local oscillators that require calibration and active reference signals. [Ed. Many of these local reference systems and oscillators are routinely updated by GPS signals.] By contrast, phase and time synchronization always require the transport of timing signals plus data. Timing signals are physical, they occur on the physical layer of networks. Indeed the IoT has many devices and applications that require frequency, time and/or phase synchronization. Frequency, time and phase all need to cross layers, boundaries, and networks from their sources in accurate clocks. Requirements for these transfer systems include parameters that create different, perhaps orthogonal, demands on systems. Accuracy, stability, integrity and even non-repudiability requirements are realized with varying demands on different systems….

    To facilitate the massive growth of the IoE, data processing and networking require new designs at fundamental levels, allowing integration with precise and verifiable time, frequency and phase signals.

    Timing performance is fundamentally dependent upon an underlying oscillator, or ensemble of oscillators and the clocks constructed based on these oscillators.

    However, it is apparent to us that many of the researchers and developers of the various time aware systems operate independently of each other. They attend different conferences, read different literature, and in general do not interact sufficiently to achieve the breakthroughs needed. In our minds this calls for a dedicated and collaborative “across the stack” research collaboration focused on two or three comprehensive challenge problems.

    * Time-Aware Applications, Computers, and Communication Systems (TAACCS), A White Paper, Feb. 15, 2015. Available from http://nvlpubs.nist.gov/nistpubs/TechnicalNotes/NIST.TN.1867.pdf

    Fortunately, this is what researchers, scientists, analysts and metrology experts do at NIST and what we learned about during the T&F Metrology Seminar. The bottom line is many perturbations affect timing signals from atomic reference systems and even local quartz oscillators (clocks). The more these perturbations are understood, the easier they are mitigated and the more stable and accurate our timing signals will be and the faster technology — PNT (position, navigation and timing), clock and otherwise — advances.

    For many traditional timing applications and developing “post-timing” applications, stability is more important than accuracy; just as for most advanced technology applications, frequency is more important than time of day.

    NIST clearly states its Time and Frequency Metrology Group has the world’s most advanced measurement and calibration facilities for characterizing noise components in oscillators and frequency synthesizers. NIST engages in numerous research and development activities to determine the cause of various types of noise for the purpose of isolating and reducing it, leading to improved components, instruments, techniques and results that are often critical in modern applications. In other words, you have to thoroughly understand a clock issue before you can begin to mitigate issues affecting it. NIST, a synecdoche for understanding time, does that better than any other metrology laboratory in the world today when it comes to atomic reference systems.

    What Is Time and Why Does It Matter?

    Accurate timing and synchronization are a crucial part of the world’s critical national infrastructure and of modern technology in general, especially the timing signals from GPS satellites, which are used by billions of users continuously every day — although most users remain unaware of the importance and impact that accurate and stable timing has on their everyday lives.

    Tom O’Brian reminded us that even St. Augustine of Hippo wondered about time. In circa 400 he wrote:

    “What then is time? If no one asks me, I know.
    If someone asks me to explain, I know not.”

    Then, just 1500 years later in 1930, Albert Einstein had this to say about time:

    “Space and time are modes by which we think, not conditions under which we live.”

    Therefore, I agree with David Allan when he posits that time is a human invention with which only humans struggle. Be that as it may, it is still a condition we live under, and when you consider all the forces, minute to infinite, that affect atomic reference systems and clocks in general, it is amazing our clocks function as well as they do.

    Consider that atomic clocks, and even quartz clocks to some extent, are affected by the following elemental and environmental forces and more in the laboratory:

    • Motion
    • Acceleration
    • Gravity – Earth, Moon and planetary
    • Changes in elevation
    • ~23 different types of noise
    • Temperature
    • Magnetic fields
    • Earth’s Poles
    • Tides
    • Light (including lasers)
    • Electricity
    • General and Special Relativity
    • Radiation

    The United States Air Force then takes these delicate clocks, atomic (Rubidium and Cesium) as well as quartz VCXOs and OXOs, and launches them (with violent maneuvers) into space in a Medium Earth Orbit that regularly intersects the Van Allen radiation belt. Once on orbit, the clocks routinely experience every one of the listed forces and more on both a regular and changing basis. Of course, we expect the GPS clocks to operate at the same standards and with the same stability and accuracy they displayed in the laboratory. Not asking much are we?

    The amazing fact is that thanks to the dedicated scientists and physicists at NIST and other timing laboratories, the clocks work as advertised and continue to do so sometimes for more than 20 years. The current GPS III Rubidium clocks being tested and aged at NRL (Naval Research Laboratory) and other locations around the U.S .are posited to be the first 30-year Rubidium standards with nominal frequency stability of 1 x 10-15. This should provide GPS with another nanosecond of timing accuracy and another 12 inches of positioning accuracy. There will be three of these extremely stable Rubidium clocks on board each GPS III satellite — no Cesium clocks for this family of satellites. Horologists around the world are hoping it is truly a 30-year tube and that only one Rubidium will be required. Only time will tell.

    Little Known Factoid (LKF): The first family of GPS satellites on orbit made use of a General and Special Relativity switch that could be set in one of three positions: neutral, plus or minus, depending on whether the universe was relatively static, expanding or shrinking in size. Guess where the switch was set initially and (hint, hint) it could be changed via software from the ground. Drop me a line @ [email protected] and let me know what you think — posit or know, as the case may be.

    Thanks

    My thanks to David Howe, Judah Levine, Neil Ashby, David Allan (Ph.D.s all) and Danielle Lirette, who made my visit to NIST such a wonderful experience.

    It’s About Time

    Earlier I mentioned physicist David Allan’s wonderful book, published in 2014. It’s About Time: Science Harmonized with Religion. Allan is about science harmonized with religion and where we are in God’s time. I am halfway through the 402-page tour de force on time, and it is a fascinating read. It is a 50-year biography and history of atomic reference systems, since the first atomic clock only came about in 1949. You’ll be amazed how that happened. Based on what I have read so far, I highly recommend this scientific tome, which is very readable and understandable even for the lay reader. I promise a full review in a future column.

    Until then, Happy Navigating! I hope to see many of you at ION JNC (Institute of Navigation Joint Navigation Conference) in Orlando, Fla., June 21-26. There will be a classified day on Thursday, June 25,  and a Warfighters Panel as well. Hope you can join us. Remember, GPS is brought to you courtesy of the United States Air Force.

  • RNT Foundation Creates Advisory Council

    The Resilient Navigation and Timing (RNT) Foundation announced August 1 the creation of an advisory council that will help inform its board of directors on technology and policy issues.

    “The Advisory Council is comprised of foundation members selected because of their unique expertise, background and reputations within the international navigation and timing community,” said Dana Goward, president of the foundation.

    While the council will advise the foundation on an on-going basis, in-person meetings will be scheduled to coincide with those of the U.S. National PNT Advisory Board.

    The RNT Foundation Advisory Council membership includes Donald Jewel, GPS World Defense Editor and United States representative; Chuck Schue, also from the U.S.; Refaat Rashad from Egypt; David Last from the United Kingdom; and Krzysztof Czaplewski from Poland.

  • Out in Front: Complements of the Season

    Alan Cameron
    Alan Cameron

    In the wake of last month’s Expert Advice column on eLoran — “The Low Cost of Protecting America” by Dana Goward of the Resilient Navigation and Timing Foundation —  come several positive comments and encouraging developments. Rather than rehearse all the arguments why we should care about this, I’ll repeat the one word that I heard most often in GNSS circles in 2013: jamming. Followed closely by: spoofing.

    “I have been advocating strongly for reconsideration of the government’s domestic Loran decision for the last year or so,” writes one reader positioned on Washington’s Beltway, “and specifically working within the Department of Defense (DoD) to ensure it is aware of international developments for eLoran in the UK and South Korea, and the possibilities inherent in other former Loran chains.

    “The DoD is beginning to recognize the value of eLoran as a complement to GPS, not only for international missions, but in cooperation with the departments of Transportation and Homeland Security for domestic critical infrastructure.”

    Last fall, Don Jewell’s Defense PNT newsletter on the same subject drew this reply from another well-known expert:

    “One of the key short-term actions is to prevent the decommissioned [Loran] sites from being sold off for subdivisions. These sites are a national treasure with unique properties: soil conductivity, water content, metal content, and more that are hugely important in siting low-frequency positioning systems. Those long-gone engineers of the 1940s and ’50s knew this and chose accordingly.”

    Before last month’s issue appeared but after it had gone to press, President Obama signed the National Defense Authorization Act (NDAA) for 2014.  It contained several favorable New Year’s auguries for positioners, navigators, and timers.The act evinced an acute awareness of the vulnerability of space systems to disruption. The act is also a law governing the land. Through it Congress requires the administration to, among other things, explain biennially in its “Space Protection Strategy” report exactly how, in the event space systems are disrupted, DOD and the intelligence community “plan to provide necessary national security capabilities through alternative space, airborne, or ground systems.”

    Since said administration acted early in its first term to decommission Loran-C, the congressional directive is pointed.

    The next big thing coming up on the GNSS international horizon takes place in Rotterdam, the Netherlands, April 15–17: the European Navigation Conference, ENC-GNSS 2014. It includes a track session on “eLoran and other Low-Frequency Systems,” and I’ll be there with pencil sharpened.

    Brad Parkinson will give the ENC keynote, and he is on record as one of an august group of Institute for Defense Analyses experts who unanimously recommended that the existing Loran-C be greatly updated and modernized to eLoran. We should hear more from him on this subject amid the wharves, waterways, and docks of Europe’s largest port (world’s third busiest).

    There’s barely room left to report the successful tests of Enhanced Differential Loran (eDLoran) by Dutch specialists Reelektronika: absolute accuracy of 5 meters in the North Sea and in the Rotterdam Europort harbor area.

  • Live Coverage of ENC-GNSS 08

    Don Jewell
    Don Jewell

    NEWS FROM THE EUROPEAN NAVIGATION CONFERENCE

    By Don Jewell

    Day 3: Map Matching and Floating Cars

    Here are highlights of presentations I attended today.

    Improving GPS Accuracy for Urban Pedestrians, presented by Jean-Baptiste Prost of Pole Star

    A standing-room-only crowd packed the room to hear about map matching, a software program designed to help pedestrians use GPS-based positioning in urban areas. GPS-based positioning for pedestrians in dense urban areas suffers from a lack of accuracy and integrity. Pole Star’s solution combines GIS database containing geometrical descriptions of buildings with raw data from the receiver, then restricting the area of possible locations by matching GPS measurements with the environment and behavioral models. Tests in several cities shows dramatic improvements to the accuracy of GPS-based positioning for pedestrians, especially in areas with tiny streets. Jean-Baptiste said the product is ready under the name of NAO City.

    Real-Time Information on Road Traffic Based on Floating Car Data, by Laurent Brecheret

    The SINERGIT project has developed a cooperative information system for road and urban networks. The system aims to optimize traffic management means, and provide real-time info on driving conditions to all drivers who use personal navigation devices. The three data sources used are data from existing traffic monitoring systems, data from telecom operators tracking cell-phone use, and tracking of PNDs and GNSS-enabled smartphones. This final category is called floating car data, and is used to measure average speed of traffic and to estimate overall traffic conditions. A central system merges the three sets of data to create the best traffic information which can then be shared with drivers in real time.

    Navigation Applications Supporting the Mobility of Disabled People, by Francesca Neccia of Thales Alenia Space

    The Navigation for Disability Applications (NADIA) Project aims to improve safety and security for the disabled, while giving them increased autonomy. Using GPS, EGNOS, and eventually Galileo, a blind or wheelchair-bound individual will have supports unavailable now, with access to sports, leisure pursuits, and education. The project is now in the system engineering phase, and once system tests and validation are completed, a prototype will be demonstrated.

    Evening 2: Space Walk

    Being a fan of space exploration, the Gala Evening at the Cite de l’Espace was right up my alley. Guests toured the Mir space station, ate “space food” (served in test tubes), and enjoyed an eye-popping 3D Imax movie about the International Space Station.

    Day 2: eLoran for Europe

    eLoran for Europe: The European eLoran Forum makes a case for European support of eLoran in its new policy document. The document sets out the strategic importance of positioning, navigation, and timing (PNT) systems in Europe, and emphasizes the role of Enhanced Loran as a way of making European PNT foundations robust and resilient. “The development and operation of the European eLoran infrastructure is currently being undertaken on an ad-hoc basis,” according to the executive summary. “The importance of eLoran’s supporting role to GPS and Galileo needs to be assessed within the context of a European Radio Navigation Plan. Using these three PNT systems together will protect our critical infrastructure and allow our European service providers and users to retain the safety, security, and economic benefits of GPS that they currently enjoy even when their satellite services are interrupted.”

    Seeking the GRAIL: Hoping to hear the final results of the GRAIL project was met with slight disappointment—May is the new target date. GRAIL is a Galileo Joint Undertaking project to study how best to introduce GNSS to railways throughout Europe, in line with the European Rail Traffic Management System (ERTMS) project. ERTMS is an overall effort to make all European trail systems compatible, because each country has its own rail “language” for managing the movement of the trains on its network. Over the past decade, industrial giants and European governments have strived to attain rail interoperability, so that trains can cross borders without stopping. ERTMS has been set up to create unique signaling standards throughout Europe. Alvaro Urech from INECO described the four applications the GRAIL project is aiming for: enhanced odometry (measuring the speed and position of the trains, and possibly increasing speed); train awakening (trains knowing where each other are positioned); absolute positioning; and train integrity to ensure the trains are whole and not “broken.” So far in the project, specifications for these applications have been agreed on, along with performance requirements. A prototype for demonstrating these applications is being developed for tests in the lab or on a real high-speed line. Train awakening has been tested, but it’s too early to report results.

    Time for a New Partnership: In business news, two timing companies have announced a strategic partnership. Orolia, parent company for timing providers Spectracom and Pendulum Instruments, and Rapco Electronics (Basingstoke, Hampshire, UK), a high-precision timing provider, announced today that they’ve formed a partnership. In a multi-phased approach, Orolia Group companies Spectracom and SpectraTime will join the existing alliance between Pendulum Instruments (recently acquired by Orolia) and Rapco Electronics to cooperate on several fronts to leverage global distribution channels, operations, and new product development efforts.

    Rapco Electronics will represent and distribute Spectracom and Pendulum products in the UK and Ireland. Together with its own products, Rapco will provide a comprehensive range of high-precision time and frequency products for governmental, military, telecom, broadcasting and scientific customers. Outside of this region, both Pendulum and Spectracom will distribute key Rapco products under their own respective brands.

    Day 1: Comic Books and Space Tunes

    Toulouse is a beautiful city — pink-hued buildings with red roofs, narrow pedestrian-friendly streets, a sense of history and time. Quite a contrast to high-tech science, the subject of the Toulouse Space Show. Upon registering, I was given a bag heavier than the luggage I left back at the hotel. I’ve been to numerous conferences, both scientific and artistic, but I’ve never received such a sheer quantity of literature. I felt like a college student stocking up on the term’s textbooks.

    Inside, I discovered three inch-thick spiral-bound abstracts for all three conferences encompassed by the Toulouse Space Show: ENC-GNSS (my main focus), EFTF, and Space Applications Days, all in both English and French.

    I also discovered a beautifully designed program (or, I should say programme), and, the most quixotic item, a Galileo comic book — err, graphic novel? — published by Thales Alenia Space. Finally, a document written for me and the other non-scientists! (Edited to add: Having now read the book, some of the contentions put forth are questionable. such as the contention that the GPS signal might be turned off by the military, or that Galileo will naturally prove superior.)

    I just had time to get these goodies before settling in for the opening ceremony, a multi-media affair involving speeches, music, slideshows, and lighting effects. The speeches from local and regional officials communicated how passionate the people here are about all things space-related, in business, research, and education.

    Between the speeches, a duo dressed in flight jumpsuits sang space-themed songs such as “Fly Me to the Moon,” “Walking on the Moon,” and the Beatles’ “Across the Universe” — you get the idea. As an aside, in February NASA broadcast “Across the Universe” to Polaris, the North Star, in the first-ever beaming of a radio song by the space agency directly into deep space, to celebrate the 40th anniversary of the song, the 45th anniversary of NASA’s Deep Space Network, and the 50th anniversary of NASA. Europe’s space program isn’t as old, but it makes up for age in enthusiasm. Each tune sung by the musicians was accompanied by a huge screen showing clips of moonwalks and space-related images of planets, nebulae, and our favorite, satellites. As a long-time fan of the space program, it certainly got me in the mood for the conference.

    Tomorrow, technical sessions begin, followed by an evening gala to be held in the Cite de l’Espace, the premiere space museum. I can’t wait!