GPS Declassified

by Richard D. Easton

  Whereas previous economic studies of GPS focused on market opportunities and sales forecasts, the Coalition to Save Our GPS commissioned the first analysis of what a GPS disruption might cost the economy. NDP Consulting Group, based in Washington DC, submitted its report The Economic Benefits of Commercial GPS Use in the U.S. and the Costs of Potential Disruption in June 2011. (Many figures cited in this book come from that study.) NDP focused on three commercial sectors with high GPS adoption rates and readily available data—precision agriculture, engineering/construction, and surface transportation—to project the impact on commercial users. The study found that full nationwide disruption of GPS would produce a direct economic impact of $96 billion per year—about 0.7 percent of the U.S. economy.285 Given that the commercial market is only a quarter of the total GPS market, that shows the significant return from the roughly $35 billion in public funds spent on the constellation to date and the nearly $1-billion-per-year cost of maintaining GPS.286

  With increasing competition for limited radio spectrum, the National PNT Advisory Board expects more interference threats and wants to be better prepared to defend GPS. At its August 2012 meeting, members discussed commissioning a more comprehensive study of the economic benefits that GPS produces for the United States and the rest of the world.287 That promises to be an enormous number-crunching task, given the scope of GPS use today, and one made harder by the prospect of accounting for the growing use of receivers that combine two, three, or four different GNSS signals. The European GNSS Agency in a spring 2012 report estimated that the global GNSS market would reach €244 billion, or about $277.4 billion, by 2020. Other reports may arrive at different figures, but they are all likely to be huge numbers.

  This chapter began with the question: Where are we? One answer might be, recalculating. In the United States and much of the world, both the culture and the economy are inextricably dependent on accurate, uninterrupted GPS service. Millions of people take it for granted with little or no understanding of its operation or potential problems. Recent events should be a wake-up call. Taken as a whole, the challenges associated with preserving privacy, adding new satellite signals, synchronizing space and ground segment upgrades, avoiding interference by other radio spectrum users, and cooperating with other nations in a GNSS world underscore how complicated maintaining GPS is and how vital a broader public understanding of it has become.

  10

  Going Forward The Future of GPS

  If you don’t know where you’re going, you’ll probably end up somewhere else.

  David P. Campbell, book title, 1976

  As bestselling author Henry Petroski, a professor of engineering and history at Duke University, notes in Pushing the Limits: New Adventures in Engineering, “Predicting the technological future has always been risky business, for the world of invention and engineering never ceases to push the limits of technology to come up with surprises that surprise even the experts. ”1 What follows is less an exercise in prediction than an exploration of what seems certain, what appears likely, and what could happen in the future.

  In the near term the variable is “when ” rather than “if. ” The third major block of satellites, GPS III, should begin launching in 2015. Whereas IIF satellites are replacing the older IIA satellites (eight active as of June 2013), the GPS III satellites are slated to replace the somewhat newer IIR versions. Even if the schedule slips, as has so often happened, they will certainly join the constellation within a few years. GPS III offers many technological advances, starting with the signals. Assuming the United States and Great Britain resolve the patent issues discussed in the preceding chapter, GPS III will introduce a fourth civilian signal (L1C) that is interoperable with Europe’s Galileo, Japan’s QZSS, and potentially with China’s Beidou.2 Navigational accuracy will be three times better than with the Block IIF satellites. The GPS III’S user range error over twenty-four hours will be within one meter, versus the current three meters.3 GPS III will broadcast military signals three times more powerfully, making jamming by an adversary more difficult.4 Lockheed Martin’s subcontractor on the navigation payload, ITT, has participated in building that component in every generation of GPS satellites for more than thirty years.5

  How soon the new satellites will deliver these capabilities depends not only on the launch schedule and completion of the new OCX ground control system but also on fielding new receivers designed to take advantage of the new features. GAO in March 2012 warned, “User equipment is not expected to be fully fielded to the warfighters until many years later, possibly as late as 2025. ”6

  Lockheed Martin, which built twenty-one Block IIR satellites and “modernized ” the last eight of them (IIR[M]), designed GPS III from the start to insert new capabilities as future space vehicles ((SVS)) are built.7 Although the Air Force to date has ordered eight GPS III satellites, the 2008 contract has an option for up to a dozen. Lockheed Martin publicity materials indicate the Air Force may build as many as thirty-two GPS III satellites.8 The ninth and later SVS will support the Distress Alerting Satellite System, a NASA-led international program using GPS and Galileo satellites to relay signals from emergency beacons to search-and-rescue teams.9 By replacing a current analog component with a digital waveform generator, GPS III satellites will be equipped to generate new types of signals after they are already in orbit.10 Each GPS III will carry three rubidium atomic frequency standards but will have an open slot for a fourth atomic clock. For the first time, ground controllers will be able to turn on and monitor this backup clock separately from the operational clocks, giving them the ability to study experimental designs, such as a hydrogen maser.11 These expandable features are important because the design life of each GPS III satellite is fifteen years. The record of technological change during any fifteen-year period since the satellite age arrived suggests how quickly high-tech equipment can become obsolete. If GPS III longevity matches that of earlier generations, some satellites launched in the 2015–16 period could still be orbiting and operational in 2038 or beyond.

  GPS III satellites may repeat the pattern of GPS IIA, IIR, IIR(M), and IIF, with enhancements coming in block buys of a dozen or so satellites, or they might pioneer an unprecedented change in the constellation architecture. As this book went to production Air Force officials were considering alternatives they hope could cut costs without stifling technological progress. One proposed scheme would maintain a thirty-plus satellite constellation by combining fifteen to eighteen full-featured satellites with a balance of smaller versions that provide only basic navigation signals. Limiting some satellites to only four signals and forgoing nuclear detonation detection capability would trim weight and power consumption and could save about $200 million per satellite.12 Although the concept has been floated in the past, the idea may find new support as a way to replenish a mature constellation in the era of budget sequestration.

  Fig. 10.1. GPS III satellite. (Courtesy National Coordination Office for Position, Navigation and Timing)

  A key feature of GPS III satellites and the new OCX control system will be the ability to operate more than thirty-two active satellites in the constellation. The existing thirty-two satellite limit stems from the number of unique digital identifiers, the PRN codes (described in chapter 5), that were programmed into the original system. There were thirty-seven PRN sequences, with PRNS 1 through 32 assigned as SV ID numbers and 33 through 37 reserved for other uses. Those latter five PRNS are being redesignated for use by SVS, and the new control system will add twenty-six additional codes, PRN numbers 38 through 63.13 While nobody expects sixty-three GPS satellites in orbit anytime soon, the new technical specifications make that number possible.

  Fig. 10.2. GPS constellation, circa 2015. (Courtesy Lockheed Martin)

  The More the Merrier?

  GPS started with a constellation of twenty-one satellites and three spares. Over time, users became accustomed to about thirty, and that threshold appears set to grow. The Europeans adopted thirty as the
size of the Galileo constellation before the first launch. Russia, having restored GLONASS to twenty-four, wants to expand to thirty. China is working toward a constellation of thirty to thirty-five Beidou satellites. Add to all of these India’s IRNSS, Japan’s QZSS, and numerous satellite-based augmentation systems (WAAS, EGNOS, et al.), and by 2020 there could be about 150 navigation satellites broadcasting signals in the GPS bandwidth. This redundancy should be an unqualified boon to users, reducing the vulnerability from any single system failure while eliminating brownouts and poor reception in urban canyons, should it not? Unfortunately, the answer is no. Each additional GNSS signal increases the overall background noise that receivers must sort through to lock onto a particular signal. It is like trying to follow a conversation in a crowded room where everyone is talking at once. Guenter Hein, head of ESA’S Galileo Operations and Evolution Department, has calculated that once the number of combined signals approaches seventy, the noise from satellites will exceed the natural cosmic noise floor, and GNSS systems will begin to interfere with themselves.14 While this portends an eventual international squabble over the total number and allocation of GNSS satellites and signals, the primary worry in the near term remains terrestrial interference. This can take the form of inadvertent disruptions by adjacent radio spectrum users like LightSquared or deliberate jamming by pranksters, people trying to evade tracking, and even terrorists.

  As noted previously, jamming GPS with inexpensive transmitters is relatively easy because the signals are so faint. Some have compared using a receiver on the ground to detect a GPS signal from space to standing in Los Angeles and trying to see a sixty-watt lightbulb in New York.15 An example of the serious ramifications of jamming surfaced in 2010, when the FAA investigated why a new ground-based augmentation system ((GBAS)) at Newark Airport randomly lost GPS signal reception and shut itself down multiple times per day over several months.16 GBAS systems improve GPS accuracy to allow Category I precision landings, but officials could not approve the Newark system until determining the cause of the outages. The GBAS antenna was within about a few hundred feet of the New Jersey Turnpike, and the cause turned out to be passing truck drivers using inexpensive GPS jammers to thwart their fleet managers’ efforts to track their every move.17 Experts estimated that one hundred thousand such devices, which plug into vehicle cigarette lighters and can cost as little as thirty dollars, were in use in the United States by 2009.18 Marketing, selling, or using devices that jam signals such as GPS, cell service, police radar, or Wi-Fi is a federal crime in the United States, and the FCC announced a crackdown in October 2011.19 However, overseas sellers continue to offer a wide array of jammers on the Internet.

  North Korea jammed South Korean GPS reception for three days in August 2010, using transmitters that military analysts believe the North Koreans imported from Russia, mounted on vehicles, and stationed near the border.20 The jamming resumed in May 2011, apparently aimed at disrupting a joint military exercise with the United States.21 After North Korea’s failed attempt to launch a rocket supposedly carrying a satellite in spring 2012, South Korea reported jamming over a two-week period that affected commercial shipping and more than six hundred domestic and international airline flights.22 The jamming stopped after South Korean president Lee Myung-bak enlisted the help of Chinese president Hu Jintao during a summit meeting.23 South Korea vowed to raise the issue with the International Telecommunications Union and International Civil Aviation Organization, but North Korea denied it was the source of the interference.24 The incident illustrates the potential for geopolitical rivals to harass their opponents by disrupting satellite signals.

  Spoofing potentially poses a bigger threat than jamming since counterfeit GPS signals could go undetected until a serious problem occurred, whereas jamming is apparent due to loss of the signal. The topic grabbed international attention after Iran claimed it used spoofing to bring down a U.S. drone (a stealthy RQ-170 Sentinel unmanned aerial vehicle, or UAV) in December 2011. Iran said its engineers hacked into the drone’s electronics and fed it false coordinates, making the UAV think it was landing at an airfield in Afghanistan.25 U.S. officials disputed the claims, saying a malfunction was more likely. They pointed out that GPS merely backs up the RQ-170’s inertial navigation system, correcting drift, and asked why it took the Iranians days to find the downed craft, if they sent it false coordinates.26 Mechanical and engine failures are common causes of drone crashes, along with lost data links—like a dropped call on a cell phone.27 Ohio-based air national guardsmen lost control of a $3.8 million Predator drone in September 2012, and Air Force superiors ordered them to crash it into in an Afghan mountain, marking the one hundredth drone lost since 2007.28 However, GPS specialist Todd Humphreys, an assistant professor of aerospace engineering at the University of Texas at Austin, announced soon after the Iranian incident that he had developed a powerful spoofing device for less than $1,000.29 He and his students later demonstrated it to Department of Homeland Security officials at White Sands Missile Range in New Mexico, where from about a half mile away, they commandeered a commercial quadrotor helicopter UAV using GPS as its sole navigation system.30 Humphreys called the Iranian claim “within the realm of possibility ” and warned that inexpensive spoofers would be attractive not only to terrorists but to anyone wanting to fool GPS systems—from fishing boats working off-limits waters to financial traders exploiting split-second time discrepancies in fast-moving markets.31 As GPS adoption increases, spoofing seems likely to prompt new regulations, require new law enforcement techniques, and spawn a black market in the devices.

  GPS and GNSS systems have vulnerabilities beyond malevolent jamming and spoofing. The Royal Academy of Engineering in London released a study, Global Navigation Space Systems: Reliance and Vulnerabilities, in March 2011 that echoed the U.S. National PNT Advisory Board’s call for a backup system for GPS. The report warned that widespread reliance on GNSS signals and the possibility that many seemingly unrelated services could fail simultaneously because of signal disruption have created “an accidental system with a single point of failure. ”32 Among potential causes of failure, it listed uploads of bad navigational data, clock anomalies, loss of satellites due to the orbital environment, atmospheric problems, attacks on the ground segment, faulty system upgrades, and receiver bugs. The report cited bad data uploads to GPS satellites in 1993, 2000, and 2002 and clock anomalies in 2001 and 2004. In the 2004 example, the clock error of SVN-23 (the oldest GPS satellite in orbit) went undetected for three hours, producing a user-range error of about 186 miles (300 kilometers) before ground controllers spotted the problem.33 Fortunately, these incidents caused no serious problems, but they suggest ways that larger failures might occur.

  One potential cause of catastrophic failure listed in the report is impossible to predict but has sufficient probability to prompt constant vigilance of the sun. A super solar flare, or Carrington Event, named for English astronomer Richard Carrington, would saturate the orbital environment with highly charged particles that could destroy the electronics aboard satellites. Carrington on September 1, 1859, observed and made sketches of unusually intense sunspots—known as solar flares or coronal mass ejections. The next day telegraph systems worldwide “went haywire ,” discharging sparks, shocking operators, and setting telegraph paper on fire.34 Such solar activity went unnoticed before humans created electronic networks. Subsequent solar flares not nearly as large have caused significant damage to telecommunications equipment and power systems. A solar storm disabled the U.S. WAAS network for thirty hours in 2003.35 X-rays disrupted GPS for about ten minutes in 2005.36 Researchers have studied chemical evidence of ancient solar storms recorded in arctic ice and the patterns since 1859 to try to predict the frequency of a Carrington-level solar flare, with estimates ranging from once in two hundred to five hundred years.37

  Sharp Elbows in Space

  International conflicts on the ground seem increasingly likely to escalate to space, given today’s strategic relia
nce on navigation, surveillance, and communication satellites. Even if governments avoid confrontations that threaten satellites, avoiding accidents will require better systems and improved cooperation. An unclassified January 2011 summary of the National Security Space Strategy prepared by the Department of Defense and the National Intelligence Agency described the situation this way: “Space is becoming increasingly congested, contested, and competitive. ”38 Since the Vanguard satellite launched in 1958 (it is still orbiting), the number of man-made objects in Earth orbit that the Defense Department tracks has increased to about 22,000, including around 1,100 active satellites and about half as many rocket bodies.39 The military actively monitors objects ten centimeters (about four inches) in diameter and larger because a direct hit could destroy a satellite.40 However, NASA estimates there are a half-million particles between one centimeter and ten centimeters in diameter in low Earth orbit—below 1,250 miles (2,000 kilometers)—that could damage satellites, the Hubble telescope, or the International Space Station in an impact.41 Fortunately, GPS satellites are in mid-Earth orbits ten times that distance, but they will be just as vulnerable if present trends creep to higher altitudes.

  Debris has increased dramatically over the past few years because of satellite breakups and collisions and an antisatellite (ASAT) test by China. In 2009 an inactive Russian government Cosmos satellite collided with an active U.S. commercial Iridium satellite about 497 miles above Siberia, destroying both and adding 1,500 to 2,000 pieces of space debris.42 It was the first reported collision between two satellites in orbit, although a rocket fragment struck and damaged a French satellite in 1996.43 After the 2009 incident the U.S. military established a warning system for close approaches of all satellites it tracks, and the European Union proposed an international code of conduct for outer space.44 U.S. opponents balked at any agreement that might limit military options, but the Defense and State Departments eventually endorsed the concept in January 2012, expressing confidence that they could create a code of conduct that did not constrain national security–related space activities.45 That announcement came days after a defunct Russian spacecraft crashed into the Pacific Ocean near Chile.46