Technological Principles and the Policy Challenges of the Global Positioning System

Marlee Chong

Spring 2013 Contents

1 Introduction 3

2 History 4 2.1 Location ...... 4 2.2 LORAN ...... 5 2.3 GPS Predecessors ...... 5 2.4 Developing GPS ...... 6

3 Technology 8 3.1 User Segment ...... 8 3.2 Control Segment ...... 8 3.3 Space Segment ...... 9 3.4 Signal ...... 10 3.5 Pseudoranging ...... 11 3.6 Errors and Accuracy ...... 12 3.6.1 Clock Errors ...... 12 3.6.2 Atmospheric Errors ...... 13 3.6.3 System Noise ...... 13 3.6.4 Multipath Errors ...... 13 3.6.5 Dilution of Precision ...... 14 3.6.6 Accuracy ...... 14 3.7 Vulnerabilities ...... 15

4 Applications 16 4.1 Military: Smart Bombs ...... 16 4.2 Positioning: Fault Monitoring ...... 16 4.3 Navigation: Mobile Phones ...... 17 4.4 Timing: Stock Exchanges ...... 17 4.5 Satellites: Nuclear Test Detection ...... 18 4.6 Signals: Weather Forecasting ...... 18

5 Policy 19 5.1 Domestic Governance ...... 19 5.1.1 Defense ...... 19

1 CONTENTS 2

5.1.2 Civil ...... 20 5.1.3 Privacy Issues ...... 21 5.2 Competing Systems ...... 21 5.2.1 USSR and Russia ...... 22 5.2.2 European Union ...... 22 5.2.3 China ...... 22 5.2.4 Japan ...... 23 5.2.5 India ...... 23 5.2.6 International Cooperation ...... 23 5.3 Modernization ...... 23 5.3.1 Space Segment ...... 24 5.3.2 Control Segment ...... 24 5.3.3 Replacement ...... 24 5.4 Future and Recommendations ...... 25

6 Conclusion 26

7 Acknowledgements 27 Chapter 1

Introduction

The Global Positioning System (GPS) has become a part of everyday life. In the palm of their hands, users can take advantage of a network of orbiting satellites to determine their coordinates on Earth. However, GPS offers much more than a locator system. Users take advantage of its capabilities for timing, weather forecasting, and even military applications. In fact, GPS was developed during the Cold War through a combination of efforts by the US Navy and US Air Force. Owned and maintained by the United States Government, GPS is available for civilian and commercial use worldwide, free of charge, as a public utility. Still, the US military still has access to encrypted and more accurate signals for defense purposes. GPS has three components: the user segment, control segment, and space segment. The space segment consists of a minimum of 24 satellites, whose orbits are monitored and corrected by the control segment. Receivers in the user segment determine the time it takes the signal to travel from satellites. Despite the seeming ease of pushing a button to use GPS, the details are more convoluted. The system design makes it impossible to actually determine a receiver’s position by measuring the time it takes for a satellite’s signal to reach the receiver. Instead, a pseudorange is calculated with all of the errors that are implied. Although the system was designed for positioning, navigation, and timing purposes, GPS is also used for other applications. A sample of six applications demonstrate the incredible diversity of uses, some of which are expected while others of which appear to be unrelated. The first four are based on the military, positioning, navigation, and timing applications originally envisioned. The final two appropriate system components for their own purposes. As a dual-use system, GPS is governed by military and civilian agencies and is used for both defense and civil purposes. However, there are issues at the border with regards to privacy. Additional policy concerns come from competing systems, particularly those in development, and the need for international cooperation to coordinate and allow for interoperability. This will remain a concern well into the future with the continued modernization of GPS.

3 Chapter 2

History

The development of GPS is part of a long tradition of technologies and methods for navigation. Throughout time, knowing one’s location relative to other locations has been important for migration, trade, and the creation of regional boundaries.

2.1 Location

Some of the earliest methods of navigation relied on landmarks as reference points. Even today, vestiges of this method remain in the way that we give directions, such as the “Left Bank” and “Right Bank” of the Seine River in Paris, and in the determination of borders based on geographic features, such as the Colorado River dividing California and Arizona or the Rio Grande River dividing Texas and Mexico. One method used was dead reckoning, which estimates a position based on a known location called a fix, estimated velocity, and elapsed time. However, this method is extremely vulnerable to the accumulation and propagation of errors. If there is a small error in the estimated starting position, velocity, or time, that error will remain in all later assumptions made to determine location using dead reckoning. To minimize the reliance on a small set of reference points to orient locations with each other, a standard frame of reference that system- atically orientated locations was necessary. A geographic coordinate system provided a solution, expanding the possibilities for navigation[22]. Our familiar geographic coordinate system can be traced back to Ancient Greece, where astrologers used latitude and longitude, in addition to time and location of celestial objects, at a person’s birth to create natal horoscopes. Al- though latitude could easily be measured on land using the angle above the horizon to Polaris or sun declination and altitude tables, longitude was more difficult to calculate, and navigation in the West using latitude and longitude languished until the mid-fifteenth century. Because the 360 ◦ revolution of the Earth equates to only a 15 ◦ revolution per hour, longitude measurements re-

4 CHAPTER 2. HISTORY 5 quired accurate measurements of time. In fact, two measurements were needed: a ﬁxed reference time, such as Greenwich Mean Time, and a local time[22] . Measuring time accurately required the development of a timepiece that did not need to be stationary. Other challenges included measuring the size of the earth and describing celestial and planetary motion as reference points.These challenges persisted through the 19th century. However, using latitude and longitude to solve the problem of navigation was only one of many methods. Some modern attempts used radio waves, although the need to accurately measure time remained.

2.2 LORAN

World War II witnessed the development of several well-known technologies by militaries, from atomic bomb to radar. A lesser-known terrestrial radionavi- gation systems, the Long Range Aid to Navigation (LORAN), was also developed. A master station broadcasted synchronized radio pulses to two or more secondary stations, which then also transmitted the radio waves to the user, who could calculate the time diﬀerence between signals based on the known location of the transmitting stations and known emission delays. The time dif- ferences corresponded to hyperbolic lines of position, and the intersection of these deﬁned the user’s two-dimensional position. While the 1960s saw global coverage with the launch of the Omega system, improvements continued to be made to LORAN[18, p. 123-127]. Its successor, Loran-C, remained in operation until 2010 and could be integrated with GPS or used as a backup system, especially in areas where incoming satellite signals where blocked[14, Termination of LORAN-C].

2.3 GPS Predecessors

The 1957 launch of Sputnik by the USSR not only transformed the space race into a race to put a man on the moon but also opened up possibilities for the applications of satellites. At John Hopkins University’s Applied Physics Laboratory (APL), physicists noticed a measurable Doppler shift in the satellite signal. Dr. Frank T. McClure realized that these measurements could be used to provide the location of a stationary observer. In 1960, physicist and president of the Aerospace Corporation Ivan Getting proposed that satellites could not only provide information about position but also improve navigation by land forces. That same year, APL developed a prototype satellite positioning system for the US Navy. By 1972, this functioned as the Navy’s space-based navigation system called the Navigation Satellite System (NAVSAT, also known as Transit), which operated until 1996. The USSR developed Cicada, a system based on the same principles, but these systems were limited by the need to have an unobstructed line of sight due to the short wavelengths. Furthermore, the processing time and accuracy, while suitable for the needs of slow-moving naval vessels, were CHAPTER 2. HISTORY 6 insufficient for aircraft[23, p. 2]. Thus, the US Air Force had been investigating a competing idea, and together, their efforts led to the development of GPS. Transit was only the first of three important predecessors to GPS. The second was Timed Navigation (Timation), a program by Roger Easton at the Naval Re- search laboratory that improved the precision of clocks and ultimately brought atomic clocks to space. These stable space-based clocks improved the accuracy of timing information because like earlier terrestrial positioning methods, satellite positioning requires highly accurate timepieces to determine location. To determine the user’s location, Timation used Side Tone Ranging, where a satellite broadcast a clear and obvious signal that could easily be jammed. However, each satellite would need to broadcast on a fundamentally different frequency [24]. The US Air Force’s 621B program was the third competing design. A satellite positioning system designed to offer three-dimensional coverage and global service, 621B used digital signals. This meant that all of the satellites could share a spread spectrum signal, differing only due to Doppler shifts and avoiding inter-channel bias shifts. 621b also explored variations on number and configu- ration of satellites for a network providing global coverage[20].

2.4 Developing GPS

The Department of Defense’s Defense System Acquisition Review Council (DSARC) wanted to solve the problem of location by design a positioning and navigation system using space satellites. With three competing proposals, either one idea or a combination of the three needed to be selected and funded. Air Force Colonel Bradford Parkinson, the 621B program manager, had initially brought that program to the DSARC for approval in August of 1973, but it was re- jected. Parkinson’s hero, the nuclear physicist Dr. Malcolm Currie, the Deputy Director of Research and Engineering for the Department of Defense, advised Parkinson to propose a joint program synthesizing the various elements. The aims of Parkinson’s Defense Navigation Satellite System (NAVSTAR) Global Positioning System were simple. The mission was to have a system that worked well for dual use with signals available both for the military and civilians[27]. The aim was to be precise enough “to drop five bombs in the same hole” for less than $ 10,000 [20]. They would combine the orbit determination of Transit to know the location of satellites in the constellation, the stable timing of atomic clocks aboard satellites from Timation, and the operation concept and digital signal structure of 621b. Parkinson also created a program to develop user equipment as Pentagon offi- cials needed proof-of-concept for the users in order to approve satellite launches. A system of ground-based satellite mock-ups called pseudolites broadcasted signals that aircraft with receivers could use to navigate. Parkinson chose to test this prototype at the US Army’s Yuma Proving Ground to bring the Army into a joint program that he thought the Navy and Air Force were already interested in. However, the joint program remained under the control of the Department CHAPTER 2. HISTORY 7 of Defense and Parkinson, who did not want to relinquish control of the design decisions to contractors[20]. The first satellites were contracted in 1974 and launched four years later. At this time, the Department of Defense decided to introduce timing errors for civilian signals, a forerunner to Selective Availability, in order for the US military to have superior technology in event of conflict. By 1980, the concept of GPS had been tested with 10 meter accuracy for military use, but even in 1978, the first differential GPS systems demonstrated accuracy of 2.5 meters horizontally after calibrating to the known location of receivers on the ground. In fact, the Federal Aeronautics Administration funded research on differential GPS systems for civilian aviation purposes in contrast to the Department of Defense’s policy in the matter[20]. While GPS did not reach its full operational capability until 1995, Colonel Parkinson retired in 1978 after the system had launched and met its initial goals. In 2003, he and Ivan Getting were awarded the Charles Stark Draper Prize by the National Academy of Engineering “for their technological achievements in the development of the Global Positioning System (GPS)[1].” Chapter 3

Technology

GPS is comprised of three segments: the space, control, and user segments. The space segment includes an orbiting constellation of 24-32 satellites broadcast- ing microwave signals. The control segment includes Master Control Stations, monitor stations, and ground antennas to control and monitor the satellite constellation. The user segment includes receivers on the ground that calculate the user’s position based on the satellite’s signals.

3.1 User Segment

With the wide array of applications taking advantage of GPS, the user segment extends beyond units that determine position using radio signals broadcast by satellites. These devices take signals called pseudorandom noise (PRN) codes as input and provide information about the location and status of the transmitting satellite as well as the time to arrive as outputs. The user segment also includes all receiver equipment that uses the position and time information for a wide variety of applications not limited to navigation. The United States Government identiﬁes several industries as part of the user segment: agriculture, aviation, environment, marine, public safety and disaster relief, rail, recreation, roads and highways, space, surveying and mapping, and timing[14, Applications]. For more information see Chapter 4.

3.2 Control Segment

The Master Control Station is run by the 2nd Space Operations Squadron of the United States Air Force, which tracks satellites, monitors transmissions and sends commands and information to the satellites. It also monitors systems health and integrity, repositioning satellites in case of failure. Monitor stations track satellites passing overhead and collect atmospheric data, range and carrier measurements, and navigation signals. There are six

8 CHAPTER 3. TECHNOLOGY 9 stations run by the USAF in addition to 10 National Geospatial-Intellignece Agency sites that were added in 2008. Ground antennas and tracking stations transmit navigation data and com- mand transmissions to and from the satellites. There are eight tracking stations in Air Force Satellite Control Network in addition to four ground antennas lo- cated with monitor stations[14, Control Segment].

Figure 3.1: A map of the control segment [14, Control Segment]

3.3 Space Segment

The core of the space segment is a constellation of 24 satellites that orbit Earth twice a day. While this is the bare minimum to provide global coverage, the system today needs to robust in case of failure or other anomalies, which is why there are additional satellites. The initial proposal had eight satellites orbiting in three rings, which would have required less spare satellites than the current design. The basic constellation consists of six rings of four satellites and aims to have two extras satellites in each ring. Even if a satellite does not fail but needs to be repositioned, the orbit is also designed to allow for inexpensive repositioning with minimal maneuvering[23, p. 49-50]. Although the constellation requires that these satellites be distributed in such a way that they provide good geometric coverage, they are not evenly distributed across space in a geostationary or geosynchronous orbit. Those configurations would require ground stations on the other side of the globe, which is neither practical nor feasible. Instead, the orbits were designed so that the satellites would always pass over the United States, where ground stations could communicate with the satellite[20]. The orbits also needed to be high CHAPTER 3. TECHNOLOGY 10 enough to avoid atmospheric drag and have better visibility and coverage of the earth, which resulted in satellites in low earth orbit. Satellites are consistently modernized, with new designs planned as satellites degrade or exceed their intended design life. The first generation of operational satellites was designed to have a seven-and-a-half year lifespan, while the third generation of satellites currently under development will have a 15-year design lifespan. However, some currently operating satellites have been operating for over 20 years[14, GPS Modernization]. Despite the use of solar panels and backup batteries for power consumption needs, rocket fuel limits satellite lifes- pans. This fuel is needed for corrections to the flight path in order to remain in the correct orbit[21, p.139]. Satellites that are no longer needed are sent to a higher orbit to drift farther out into space because too much energy would be needed to bring them down in the atmosphere to burn[20].

3.4 Signal

Satellites broadcast microwave signals in the forms of sine waves at two frequencies, L1 and L2, which are multiples of the same clock carrier frequency of 10.23Hz. These carrier frequencies are then modulated by PRN codes unique to the satellite that make it possible to identify the source. Civilians have access to Coarse Acquisition Code, which modulates L1, but military users have access to Precision Code, which modulates both L1 and L2 and is more precise because there are two signals. Anti-spooﬁng encrypts P code as Y code, making L2 unavailable to other users. Selective Availability also segregated military and civilian users March 25, 1990-May 1, 2000, although the US government claims that it will not be turned on again[14, Selective Availability]. Civilians were only able to use the Standard Positioning Service, compared to military standard Precise Positioning Service, decreasing performance by a factor of seven[18, p. 9]. It did so by deliberately introducing two errors. One seemed to add random noise to all satellite clocks, while the other introduced slowly varying orbital errors that seemed almost identical for users who were close together[23, p. 124]. This allowed for the commercial market to develop workarounds that increased precision for civilian users, ultimately contributing to the decision by the US government to abandon this policy. Each satellite is identiﬁed by a unique space vehicle number and pseudoran- domnoise (PRN) code that are included in a navigation message. The broadcast ephemeris provides coordinates of the GPS satellites as a function of time, while additional correction parameters are included in the navigation message. In addition, a handover word can identify which type of P or Y code is transmitted[18, p. 15-16]. CHAPTER 3. TECHNOLOGY 11

3.5 Pseudoranging

To calculate a receiver’s location, the receiver uses a mathematical technique called trilateration. Trilateration uses the geometry of shapes to determine the locations of points by their distances. In this case, the distance between a satellite and a receiver means that the receiver knows where the satellite should be on an imaginary sphere. Using the information from multiple spheres and ﬁnding where they intersect, the receiver can determine its location.

Figure 3.2: Using trilateration to calculate location. Knowing the distance from the satellite in the upper left, trilateration dictates that the user can be anywhere on the surface of the sphere. Adding information from a second satellite in the upper right, the range of possibilities is narrowed to the points on the plane where the spheres surfaces intersect, shown in blue. With information from a third satellite in the lower left, the location is narrowed to either of the two starred points that intersect all three spheres. However, when information from the fourth satellite in the lower right is added, only one point intersects all four spheres. Thus, the upper starred point is ruled out, leaving the remaining star as the location.

Ranging determines the distance between a satellite and a receiver based on two variables: the speed at which the signal is travelling and the time it takes for the signal to travel. Multiplying the speed and the time results in the distance. As an electromagnetic signal, the speed is the same as that of CHAPTER 3. TECHNOLOGY 12 the speed of light, c = 3 ∗ 108m/s. Included in the signal is a timestamp of the signal leaving the satellite, while the time that the signal reaches the receiver can also be measured. This is why the development of highly precise atomic clocks was critical to GPS. Without accurate timekeeping, errors would propagate in determining the distance to and thus location of the receiver. However, there are inherent biases in the system and user time measurements when calculating the distances between satellites and receivers that renders ranging impossible. There is a diﬀerence between the geometric range time, calculated from production of the signal to the reception of the signal, and the pseudorange time, which is the diﬀerence between the satellite and receiver clocks ignoring the time it takes the signal to reach the satellite and receiver clocks after being generated or received, respectively. Because satellite ranging is inherently indeterminable, the term pseudoranging is used instead[23, p. 302- 304].

3.6 Errors and Accuracy

Figure 3.3: Geometric range and pseudorange time [23, p. 303]

0 The diﬀerence between the receiver and satellite clocks reading time is (Tu + 0 δtD + tu) − (Ts + δt). Since the geometric time ∆t = Tu − Ts, this simpliﬁes to ∆t + δtD + tu − δt. Thus, the pseudorange p = c ∗ ∆t + c ∗ (δtD + tu − δt).

3.6.1 Clock Errors δt descries the satellite clock error. It is common to all users of a satellite and includes both the hardware delay between signal generation and transmission as well as errors for the clock itself. This includes the clock bias, clock drift, frequency drift, drift rate, and relativistic corrections. However, the navigation message includes details of the bias, drift, and drift rate, making it possible for the receiver to correct for these. In addition, the relativistic corrections due to CHAPTER 3. TECHNOLOGY 13 special and general relativity are on the scale of 10−10 seconds, and the satellite clock frequency can be adjusted by being preset to 10.22999999543 MHz to appear at 10.23 MHz[23, p. 304-308]. tu describes the receiver clock error. It includes both the time it takes clock to read the time after the signal reaches the receiver and the errors of the receiver clock in keeping time. Due to the prohibitive costs of highly accurate atomic clocks, receivers generally rely upon inexpensive but less accurate quartz clocks. Thus, this error is larger than that of the satellite clock error[18, p. 48]. Pseudorange errors extend beyond the errors in measuring the time the signal takes to reach the clocks. The time δtD accounts for errors en route to the receiver due to the atmosphere, noise and interference, multipath errors, and the hardware.

3.6.2 Atmospheric Errors Atmospheric errors occur in both the ionosphere, due to delays in the signal information and carrier phase, and in the troposphere, due to the refraction of water vapor. In the ionosphere, the ionized gas layer bends the signal paths due to dispersion. These changes are frequency dependent; the signal information is delayed, while the carrier phrase is early[23, p. 308-314]. The errors can also vary in time due to the effect of the sun’s radiation and Earth’s magnetic field on the altitude and thickness of the ionosphere. Modeling is able to remove the majority of the ionospheric delay errors[18, p. 51-55]. There are not always good models to describe errors introduced in the troposphere. This neutral region is non-dispersive for the signals used, resulting in only frequency-independent delays based on water vapor. The water vapor concentration depends on temperature, pressure, and humidity. In dry conditions, models can predict most of the delay. However, in wet conditions, the delays depend on the concentration of water vapor, which is not measured and difficult to predict because of an absence of correlation with data on the surface of the Earth[18, p. 51-56].

3.6.3 System Noise System noise is based on the quality of the receiver and includes biases between channels and hardware delays between the reception and processing of signals. In addition, cycle slips are discontinuities and signal losses due to the weak and noisy nature of radio signals, coming from sources such as radio interference, ionosphere disturbance, and receiver malfunctions[18, p. 50-51].

3.6.4 Multipath Errors Multipath errors occur when the GPS signals reach a receiver through different paths. The interference of reflected signals distorts the original signals, creating residuals from carrier signals that are out of phase. Although no general model CHAPTER 3. TECHNOLOGY 14 can account for the unique geometry of a situation, signal processing technology can reduce errors, while users can also choose locations without reflecting objects[18, p. 48-49].

3.6.5 Dilution of Precision In addition to these errors, the satellite geometry is responsible for propagating pseudorange errors. This effect, called the geometric dilution of precision, is due to the pseudorange error from each satellite. As we have seen previously, there are errors in the pseudorange calculated from one satellite. Trilateration effectively finds the intersection of spherical shells rather than of the surface area of the sphere. Thus, based on the geometry of the satellites in relation to the receiver, the calculation can be more or less accurate. A good satellite geometry, where the satellites are far apart, has a low dilution of precision, whereas with a poor satellite geometry, where the satellites are close together, the dilution of precision is high[18, p. 57-61].

Figure 3.4: Dilution of precision [25]

3.6.6 Accuracy Accuracy can be improved by adjusting for the orbit parameters included in the navigation message, mathematical modeling eﬀects, diﬀerencing, and aug- mentation systems. Although the 2001 performance standard was 6.0 meters in the root mean square overall signal-in space-user range error, at the time, the accuracy was already at 1.6 meters. The current performance standard, set in 2008, is 4.0 meters, but since that time, this range error was at 1.0 meters. Thus, while remaining below the published standard, the observed range error has decreased over time as accuracy has increased [14, GPS Accuracy]. CHAPTER 3. TECHNOLOGY 15

3.7 Vulnerabilities

GPS is vulnerable in three areas. Signal reception is the most prominent of these, affecting receivers using devices that interfere with the signal. Jamming and spoofing are two common techniques to do so. The GPS infrastructure, including the space segment and control segment, is also vulnerable to attack. Finally, there are additional incidental vulnerabilities for which it is difficult to control. Commercially available parts and publicly available directions can make it easy to interfere with the signal near a receiver. Jamming is intentional interference that disrupts the signal. A brute force solution, it is easily detectable due to the obvious lack of signal in an area. Although some consumers obtain these devices to retain privacy and disable tracking, the devices are illegal because they jam radio communications indiscriminately and can interfere with emergency and other communications[14, Information About GPS Jamming]. Spoofing is a more sophisticated technique that deceives a receiver into determining a different position. A signal is transmitted that seems to replicate the slightly weaker signal transmitted by the GPS satellite. However, the spoofed signal gradually deviates from the actual signal by introducing time delays, which changes the calculated position. However, since the receiver believes that it is receiving a normal signal, there are no easy detection methods or solutions as of yet[17]. The infrastructure is vulnerable to damage in all segments, from damage to the control center, to the satellite network, to cyber attacks interfering with applications. In case of an attack on the Master Control Station at Schriever Air Force Base in Colorado or other disruption, there is an Alternate Master Control Station at Vandenberg Air Force Base in California. The satellite network has redundant satellites in each of the six orbits in case individual satellites fail. Additionally, if it seems that a satellite is on a collision course with any of the many pieces of space debris in Low Earth Orbit, the Master Control Station can also adjust the satellite’s trajectory. Furthermore, applications can have individual infrastructure needs that are vulnerable to GPS, such as cybersecurity threats to clocks that reset according to GPS timing data. Unfortunately, GPS has become such a ubiquitous and well-known utility that it is a viable target for terrorism or other attacks[17]. While deliberate signal interference has already been mentioned, even unintentional interference from neighboring parts of the spectrum can lead to a disruption in service. Even nature is not immune from disrupting service as solar flares that thicken the ionosphere add atmospheric errors, sometimes to the extent that a receiver will no longer receive signal until the flare is over[28]. The best way to detect such vulnerabilities is through awareness by receivers and users to detect anomalies. However, alternate technologies and redundancy systems are also critical for the most vulnerable and important portions[17]. Chapter 4

Applications

The original intention of GPS was to provide positioning, navigation, and timing services for US military that would also be available for civilian use. The following are merely samples illustrating applications that arose from the original aims in addition to some innovative ways to use the components of the system.

4.1 Military: Smart Bombs

The US military has smart bombs that can find and navigate towards their targets. One example is the Joint Direct Attack Munition, which has a receiver to find the bomb’s position. A receiver on the aircraft then finds the target’s position, while a guidance kit monitors the position of the bomb as a control computer adjusts the tail fins. This allows for the bombs to be self-guided to their targets up to 15 miles away[4]. Without GPS, there is an inertial guidance system that can work as an alternative. However, the loss of accuracy and precision leads to collateral damage from bombs missing targets in addition to a potential scaling up in missiles to increase the probability of hitting a target.

4.2 Positioning: Fault Monitoring

Earthquakes are a rather poorly understood physical phenomena. Scientists have diﬃculty predicting the time and strength of quakes. In order to advance their knowledge of faults and the forces at work, the US Geological Survey uses GPS to measure the relative position of stations near active faults. Collecting this data over long periods of time allows them to calculate strain, slip, and ground deformation and advance knowledge about these processes[6]. The US Geological Survey could easily substitute other methods to conduct surveys to catalog these positions. The timescale resolution is very large, with succeeding measurements taken after a period of months or even years, so the time it takes for a technique to determine position is trivial. This is in contrast

16 CHAPTER 4. APPLICATIONS 17 to the smart bombs mentioned previously, which are moving at high velocities and need a robust method to quickly calculate position.

4.3 Navigation: Mobile Phones

While assisted GPS uses the carrier network and cell towers to improve location ﬁnding services, navigation is nonetheless an important feature of mobile phones with built-in receivers and mobile apps that can access GPS data. Triangulation from cell towers could still provide position information for navigation software in the absence of GPS, although the towers would have an issue with synchronizing their clocks in the future. There is also a vibrant community to code patches or other apps. One danger is that this community has created spooﬁng apps to change the coordinates read by other apps.

4.4 Timing: Stock Exchanges

GPS provides timing information to the NYSE and Nasdaq data centers. A local receiver registers the time from the atomic clocks on the satellite and uses that information to synchronize the in-house servers every second. The stock exchanges execute and timestamp trades according to these times. In this age of high frequency trading, the financial sector needs nanosecond resolution. While Network Time Protocol is used to synchronize the servers, there often are a few seconds of delays when time is obtained through the internet, while accuracy derived from American atomic clocks is on the order of milliseconds. Using a local source such as a GPS receiver to synchronize the clocks provides the accuracy needed. In addition, some trading houses obtain time from civil GPS through cellular networks. A time delay would offset the financial sector and stock markets due to the small changes that would occur. Each individual delay would propagate into a whole series of delayed transactions that would disrupt the schedule of high frequency trading and which could trigger automatically programmed transactions to take place. This could then cause serious havoc to the stock market and the interconnected global economies. On a smaller scale spoofers could introduce a time offset that would allow them to make money. If a stock’s price rises quickly over a short period of time, spoofing would make it possible to bid on a stock based on its earlier, lower price while selling it at the current, higher asking price. In either of these scenarios, it is plausible that the stock exchange would be held responsible for the damages that occur. In any case, to prevent such occurrences, cybersecurity is vital to protect the networks against hacking. The stock exchanges should also have multiple clocks, even a local atomic clock, to check the integrity of their system. Additionally, users could protect against spoofing by checking the provided location of the GPS signal[17]. CHAPTER 4. APPLICATIONS 18

4.5 Satellites: Nuclear Test Detection

The US Atomic Energy Detection System is a global network of sensors to detect nuclear explosions operated by US Air Force[10]. It uses sensors aboard the GPS satellites to monitor space and the atmosphere for possible nuclear events and then follows up to determine the causes[31]. The data is processed at the Air Force Technical Applications Center in Colorado’s Buckley Air National Guard Base by a detachment supporting the safeguards of the Limited Test Ban Treaty[30]. A disruption to GPS could have a wide variety of eﬀects. If the satellites and sensors remained fully functioning and in orbit because the GPS signal transmission failed, this application would still function normally. In the event that the GPS satellite constellation was destroyed, data would still be collected from other satellite-based sensors in the US Atomic Energy Detection System in addition to sensors based on land and in the ocean. Other satellites could also host future sensors. Thus, a disruption to this application through a failure in the GPS infrastructure would likely be either minimal or a symptom of a greater threat to all space-based operations.

4.6 Signals: Weather Forecasting

Radio Occultation measures atmospheric density from the refraction of signal passing through atmosphere to a low-Earth orbit satellite. Computer models can also use information from radio occultation to calculate atmospheric tem- peratures to calibrate readings from satellites[29]. This can compensate for the lack of meteorological observation stations for oceans and the poles, something that has been especially useful in Australia[11]. In the absence of GPS, there would be less complete models, though there are accuracy issues regardless. Instruments would also have less precise calibration, although there are alternatives such as satellite imaging. Chapter 5

Policy

Even since the National Defense Authorization Act for Fiscal Year 1998, GPS has been mandated as part of the US law. Title 10 of the US Code, Section 2281, mandates GPS as a responsibility of the Secretary of Defense, although the Secretary of Transportation is supposed to provide resources for civil capabilities beyond the second and third civilian signals. President Obama’s 2010 National Space Policy also supports GPS as a matter of presidential policy: “The United States must maintain its leadership in the service, provision, and use of global navigation satellite systems[14, United States Policy].”

5.1 Domestic Governance

The National Executive Committee for Space-based Positioning, Navigation, and Timing serves as the overarching organization. However, the National Co- ordination Oﬃce runs policy with working groups, and NASA provides an Ad- visory board. Government departments involved include Defense, Transporta- tion, State, Interior, Agriculture, Commerce, Homeland Security, Joint Chiefs of Staﬀ, and NASA[14, National Executive Committee for Space-Based Posi- tioning, Navigation, and Timing]. Although the departments of Defense and Transportation fund the system, there are other parties and stakeholders.

5.1.1 Defense The Department of Defense is responsible for the continued operations, development and sustainability of GPS, providing nearly all funding for the system’s maintenance and modernization. Their aim to is provide tactical and military support, denying hostiles access to the system with local jamming. As the developers of GPS, the US military has and remains vested in their product. Although military users have beneﬁtted from access to an additional signal and thus more accurate positioning information, they are already looking ahead to future navigation systems and providing research funding[14, Department of

19 CHAPTER 5. POLICY 20

Defense]. The Department of Homeland Security runs domestic and civil interference to civil use of GPS and notifies other agencies when this occurs. Their mandates for homeland security covers everything from preventing terrorism to disaster preparation and cyberspace to managing immigration and border control. In addition to using the Coast Guard Navigation Center to support civilian users of GPS, they also operate master control stations and the maritime affairs of the national differential GPS network[14, Department of Homeland Security]. Defense contractors such as Boeing and Lockheed Martin have a vested interest in developing and building the satellites, receivers and monitoring systems. Their interest in making money as led to difficulties from delays in production and budgets that cannot be kept, leading to vulnerabilities in the system.

5.1.2 Civil User receivers in the civilian market provide opportunities for business and commerce. Some models use multiple channels to take advantage of the military signals or competing systems to improve accuracy for users. In addition, GPS has created a space in which businesses can innovate and incorporate GPS into their own field. Many applications use or rely upon GPS to function. The Department of Commerce and the Federal Communications Commission (FCC) support the interests of commercial users, manufacturers, and providers. They manage the radio spectrum. In the case of a startup called Lightsquared, the company was barred from using neighboring spectrum. Although there were allegations that this was a political move, the official reason was that it would interfere with GPS. Additionally, the Department of Commerce and the FCC promote fair trade and export licensing and also regulate imports. As mentioned previously, jammers are illegal devices due to FCC regulations, which makes the importing, marketing, selling, and operating jammers is illegal. As a criminal offence, sanctions can include imprisonment and fines of up to $100,000[14, Department of Commerce, GPS Spectrum and Interference]. However, the Department of Transportation is primary civilian agency involved with GPS issues. It is responsible for civilian signals, as well as the funding for those signals. In President Obama’s 2014 budget request related to GPS, less than $150 million comes from Department of Transportation appropriations. This is just over ten percent of the $1.2756 billion that come from Department of Defense appropriations[14, Fiscal Year 2014 Program Funding]. The Department of Transportation is expected to inform the Department of Defense about new, unique civilian GPS capabilities. Capabilities falling under the domain of the Department of Transportation run the gamut from aviation to highways, to the marine and rail applications[14, Department of Transporta- tion]. CHAPTER 5. POLICY 21

5.1.3 Privacy Issues In this digital age, privacy has taken new and unforeseen turns. Technology has often developed faster than policy can, or even chooses to, react. This is an especially interesting case for GPS. While jammers initially provided consumers a layer of privacy against the use of trackers, policy has made these devices illegal due to their indiscriminate and widespread disruption of communications in order to protect public safety. In the absence of technological solutions, there have been no clear policies regulating the use of GPS trackers for private or public use. However, there are some court cases and legislation dealing with the government’s use of such devices. In January 2012, the Supreme Court in United States vs Jones established that a warrant was necessary to secretly install a tracker under the laws against illegal searches and seizures[14, Supreme Court Ruling on Warrantless GPS Vehicle Tracking]. However, United States vs Katzin challenges the use of GPS trackers because the court never ruled on whether tracking in and of itself is considered a search that thus needs a warrant. The Obama administration argues that these warrantless trackers are necessary and legal[16]. The Geolocation Privacy and Surveillance Act by Sen. Wyden D-Ore, Rep. Chaﬀetz (R-Utah), and Sen. Kirk (R-Ill) was introduced to propose a standard for government access. It was introduced in committees to the Senate in 2011 and the House in May 2012, but no progress has been made since[14, Geolocation Privacy Legislation]. Although eﬀorts to clarify the use of GPS tracking devices have begun, neither the judicial nor the legislative system have made great strides. There is a clear need to safeguard the public’s privacy and establish boundaries and protocols for using GPS tracking devices.

5.2 Competing Systems

The State Department conducts international diplomacy, cooperation, and negotiations while promoting US foreign policy objectives. These include working with the International Committee on GNSS and international spectrum allocations. This department also regulates export licenses for controlled technologies[14, Department of State]. Many countries seek local or regional independence against fears of potential signal failure or interruption, whether deliberate or accidental. Some also are concerned about the reliance on the US to provide this utility because of projected delays in modernization that could lead to a gap in service. Certain nations also seek improved coverage in their regions, which might not have ex- cellent coverage due to the satellite constellation or the architecture of urban environments that deflect signals. Unfortunately, only a select few countries are represented in all of these negotiations and efforts. There are three generations of competing designs, reflecting their ages and intended purposes. There is a competing system that works completely, de- CHAPTER 5. POLICY 22 veloped by the Soviet Union as part of the technological arms race during the Cold War. Expected to be fully functional by 2020, two systems by the EU and China represent attempts both to improve local coverage and provide control and security to the developers. Regional navigation systems include those developed by Japan and India for improved local coverage.

5.2.1 USSR and Russia A previously existing system, GLONASS was developed by the USSR to com- pete with GPS. Taken over by Russia following the fall of the USSR, it be- came fully operational with global coverage in 1995, the same year that GPS also achieved global coverage. However, GLONASS fell into disrepair until a restoration project began in 2002[23, p. 595-597]. Full global coverage resumed in 2011[7]. Although GLONASS is a competing system based on its use and applications, it was designed on diﬀerent principles based on frequency-division multiple access. This limits expansion to the 15 channels (all based on the same reference frequency, 10.23MHz, as GPS) and takes a larger portion of spectrum. It also lacks a global ground tracking system to calibrate the satellite clocks[23, p. 602-607]. However, for users, GLONASS had a tradition of being better than GPS because it lacked the errors of selective availability. That is why the private sector developed receivers that would pinpoint a user’s location based on information from both GLONASS and GPS.

5.2.2 European Union Galileo has been developed under the auspices of the EU and the European Space Agency for civil usage in a public-private partnership. The goal was to have both a civil system under European control as a protective security measure because of the reliance of many industries on GPS and a system that would have better coverage in the Nordic countries[3]. However, the EU was not immune from the same issues with contractors that the US has faced. Just like with GPS, Galileo is behind schedule and over budget. It was originally expected to be functional in 2010[18, p. 169], but that has been pushed back to 2020[15]. The designers of Galileo have been collaborating with the US to build an integrated system where the signal is fully compatible with both systems and so that users can receive both signals at once. The third generation of GPS satellites was designed collaboratively with this in mind[14, New Civil Signals].

5.2.3 China Beidou began as a regional system covering Asia and the Pacific, improving coverage. It has different orbits to reflect this design difference. Calculating distance will be done using 2-way ranging so that user receivers on the ground are also transmitting signals to the network. The newer version with a global CHAPTER 5. POLICY 23 network is called Compass[18, p. 170-171]. It is expected to be functional by 2020[13].

5.2.4 Japan A local system for Japan, the Quasi-Zenith Satellite System has three satellites for a dual use system for navigation and telecommunications. The system will augment GPS by providing extra signals in Japan as well as in Micronesia, Melanesia, and Australia[18, p. 172-173].

5.2.5 India The Indian Regional Navigation Satellite system will launch its ﬁrst satellite in June 2013 to begin a program to expand satellite navigation system coverage over the Indian subcontinent[26]. The space segment will have sever satellites. Three will be in geostationary equatorial orbit, while two will be in geosynchronous orbit. An additional two satellites are designed to be spares. There will be two services available: one for civilians and one limited to authorized users[12].

5.2.6 International Cooperation The State Department promotes US foreign policy within the GPS community, leading negotiations with other countries and international organizations in addition to maintaining a Sensitive Technology List and regulating exports for controlled devices. Thus, the United States has individual agreements and working groups with other nations. In addition, the International Telecommuni- cation Union conducts discussions about radio frequency compatibility between operating systems and spectrum allocations aﬀecting GPS. Other multilateral bodies that serve as forums for resolving international GPS issues include the International Civil Aviation Organization, the International Maritime Organi- zation, the U.N. Committee on the Peaceful Uses of Outer Space, Asia-Paciﬁc Economic Cooperation, the North Atlantic Treaty Organization, and the World Trade Organization. At the instigation of the United States, the United Nations formed an International Committee on Global Navigation Satellite Systems (ICG) that aims to promote compatibility an interoperability across the systems mentioned above. Cooperation is encouraged to coordinate and share information, saving costs. The UN is involved because position, navigation and timing information, the fundamental outputs of GPS, helps society’s security as well as the environment[14, Department of State].

5.3 Modernization

The system is currently undergoing updates in terms of the satellites, signals, and control elements. Of course, the private sector is also driving innovation in CHAPTER 5. POLICY 24 the user segment.

5.3.1 Space Segment Current modernization efforts center on Block IIR(M), which is expected to finish in 2015. Contracted by Lockheed Martin, there will be L2C, a new civilian signal for commercial applications, in addition to two new military signals to resist jamming and all power levels to change. Block IIF, contracted by Boeing, is expected to finish by 2015 and will provide L5, a civilian signal for aviation safety services. Future modernization efforts are in the development of Block III, contracted by Lockheed Martin for preliminary construction of the first 6 satellites. These will have L1C, a civilian signal that is compatible with international systems including those in Japan, China, and the EU[14, Space Segment]. The delay of replacements due to relaxed and insufficient oversight has led to fears of brownouts and gaps in service. In this case, the US hopes to use retired satellites, speed up production, or extend the lifetime of a satellite by reducing or shutting power to secondary missions[8].

5.3.2 Control Segment In addition to modernizing satellites, the control system is being updated. The IT at the Master Control Station has been replaced through a contract with Boe- ing that was subcontracted to Lockheed Martin in the Architecture Evolution Plan. Launch and early orbit, Anomaly resolution, and Disposal Operations is designed to deal with satellites beyond the 32 currently in orbit, including the future Block IIF satellites. It expands the control segment’s capabilities only using tracking stations, independent of the Master Control Station. Future modernization eﬀorts are in the Next Generation Operational Control System (OCX), contracted by Raytheon. Block I will manage L2C in 2016, while Block 2 will be compatible with L1C and L5. Eventually, Block 3 will be ready for GPS III. In addition, Lockheed Martin is contracted to produce the Launch Checkout Capability, which will integrated with OCX beginning with Block 1 to support GPS III[14, Control Segment].

5.3.3 Replacement DARPA’s All Source Positioning and Navigation solicits research projects for “low cost, robust, and seamless navigation solutions for military users...with or without GPS.” As of June 2012, a Phase 2 call has gone out to design algorithms to help. However, these grants are all in the rather basic research side and, even in the applied sciences, will need considerable time to be used outside academia[9]. CHAPTER 5. POLICY 25

5.4 Future and Recommendations

Sequestration and budget cuts is the core policy challenge, especially because this is not a cause that the public knows much about the rally behind and protect. However, its entrenched use in so many spheres across so many parts of the government and world give it some protection. As long as there is proper management and oversight, we should be able to maintain the system, but considerable work remains to move beyond GPS to some future system. The modernization projects are incremental innovations to the platform, although applications have innovated far beyond what could have been envisioned. Still, something like GPS could not be developed today because of the changed national priorities and expectations of science and technology. In addition, the political and economic climate are conducive to such a task. Chapter 6

Conclusion

GPS has grown beyond its original mandate to provide position, navigation, and timing services for the US military and civilians. Despite the limitations of Selective Availability, users have taken advantage of GPS and its potential to be used in a wide variety of applications. GPS is used to do everything from saving and taking lives to predicting the weather. What if something goes wrong? In such a large system, the potential for local failures is enormous. A power outage can disrupt the control segment. A satellite can collide with space debris. A solar flare can disrupt signals. GPS was designed with redundancies to protect its infrastructure, but users can also help by noticing inconsistencies. Obstructed signals might be due to densely packed skyscrapers or a jammer. Jamming is a double-edged sword used by the military to deny service to hostiles with the potential to protect user privacy. However, due to its indiscriminate nature, the effect on other communications in the area is problematic. This deliberate and potentially harmful interference led to regulation making jammers illegal. Still, the issue of privacy with regards to the practically ubiquitous GPS devices must be addressed. The US lacks a policy regarding GPS tracking by the authorities despite ongoing court cases and legislation. As GPS continues to evolve, its future development depends on funding and political goodwill. GLONASS was not fully functioning for a time due to a lack of maintenance and upgrading, while Galileo has suffered significant delays in production. GPS has similarly run into issues with contractors exceeding both time and budget. If these problems worsen, the threat of suffering a brownout due to insufficient coverage or poorly maintained infrastructure will materialize. The same applies if the current budgetary issues delay the upgrade schedule. After all, the satellites and signals currently being built are based off of older designs. The next generation of satellites that have already been designed is not expected to be produced for several more years. GPS is a public utility serving the United States and the world. Untapped potential remains, as do potential pitfalls and problems. When will we find a new solution to solving the age-old problem of how to determine location? Look to the future, and we will find out.

26 Chapter 7

Acknowledgements

I would like to express my deepest appreciation to my advisor, Professor Venkatesh Narayanamurti, who has had the patience to guide a young physics student into the realm of science policy. He has shaped my curiosity and interest with his own excitement about new ideas and subjects. Without his assistance and patience during a sabbatical year, this paper and exploration would not have been possible. Furthermore, I would like to thank Dr. Tolu Odumosu, whose support has been invaluable in the ﬁner details of this project. From understanding the elec- trical engineering concepts to communicating as a social scientist, his expertise enabled me to complete this study.

27 Bibliography

[1] 2003 Winners: Bradford W. Parkinson and Ivan A. Getting. http: //www.ieeeghn.org/wiki/index.php/Oral-History:Brad_Parkinson. [2] Before GPS. http://airandspace.si.edu/gps/before.html. [3] Galileo is the European Global Satellite-Based Navigation System. http://www.gsa.europa.eu/galileo-0. [4] JOINT DIRECT ATTACK MUNITION GBU- 31/32/38. http://www.af.mil/information/factsheets/factsheet.asp?id=108, 2007. [5] Physics for an advanced world. http://www.iop.org/publications/iop/2009/file_38209.pdf, 2009. [6] About GPS. http://earthquake.usgs.gov/monitoring/gps/about.php, 2010. [7] Global Navigation Satellite System (GLONASS) Overview. http://www.positim.com/glonass_overview.html, 2010. [8] GPS wing Q&A related to recent GAO report on GPS. http://www.afspc.af.mil/news/story.asp?id=123223689, 2010. [9] All Source Positioning and Navigation (ASPN). https://www.fbo.gov/index?s=opportunity&mode=form&id= cef82a45ab7d64a5445eadf277f13dbe&tab=core&_cview=1, 2011. [10] Air Force Technical Applications Center. http: //www.afisr.af.mil/library/factsheets/factsheet.asp?id=10309, 2012. [11] GPS Technology Improves Weather Forecasting. http://www.sciencedaily.com/releases/2012/06/120613073100.htm, 2012. [12] Indian Regional Navigation Satellite System (IRNSS). http://www.isro.gov.in/newsletters/contents/spaceindia/ jan2012-jun2012/article5.htm, 2012.

28 BIBLIOGRAPHY 29

[13] China navigation system to target global coverage by 2020. http://english.sina.com/business/2013/0303/567468.html, 2013. [14] GPS.gov. http://www.gps.gov/, 2013. [15] Satellite navigation. http://ec.europa.eu/enterprise/policies/ satnav/galileo/index_en.htm, 2013. [16] White House to argue for GPS tracking without a warrant. http://rt.com/usa/white-house-favors-warrantless-gps-692/, 2013.

[17] Malcolm J. Airst. GPS Network Timing Integrity. http: //www.gps.gov/governance/advisory/meetings/2012-08/airst.pdf, 2010. [18] Ahmed El-Rabbany. Introduction to GPS: The Global Positioning System. Artech House Publishers, Boston, MA, second edition, 2006.

[19] Gregory T. French. Understanding the GPS: An Introduction to the Global Positioning System: What It Is and How It Works. GeoResearch, Inc., Bethesda, MD, 1996. [20] Michael Geselowitz. Brad Parkinson, an oral history conducted in 1999. http://www.ieeeghn.org/wiki/index.php/Oral-History: Brad_Parkinson, 1999. [21] Albert Helfrick. Principles of Avionics. Avioinics Communications Inc., Leesburg, VA, seventh edition, 2012. [22] John Huth. The Lost Art of Finding Our Way. The Belknap Press of the Harvard University Press, Cambridge, MA, 2013.

[23] Elliott D. Kaplan and Christopher J. Hegarty, editors. Understanding GPS: Principles and Applications. Artech House Publishers, Boston, MA, second edition, 2006.

[24] Herbert J. Kramer. TIMATION. https://directory.eoportal.org/ web/eoportal/satellite-missions/t/timation. [25] Bharat Kumar, editor. An Illustrated Dictionary of Aviation. McGraw-Hill Companies, Inc., New York, 2005. [26] Rhik Kundu. Indian Regional Navigation Satellite System to be launched in June 2013. http: //articles.timesofindia.indiatimes.com/2013-04-21/science/ 38709145_1_irnss-beidou-regional-navigation-satellite-system, 2013. BIBLIOGRAPHY 30

[27] Andrew Myers. Bradford Parkinson: Hero of GPS. https://engineering.stanford.edu/news/ video-bradford-parkinson-gps-humanity, 2012. [28] Thomas Oberst. Solar ﬂares cause GPS failures, possibly devastating for jets and distress calls, Cornell researchers warn. http://www.news.cornell.edu/stories/2006/09/ solar-flares-could-seriously-disrupt-gps-receivers, 2006. [29] Daniel Parry. NRL Fully Integrates GPS Radio Occultation into Global Weather Prediction. http://www.nrl.navy.mil/media/news-releases/2011/ nrl-fully-integrates-gps-radio-occultation-into-global-weather-prediction-, 2011. [30] Cheryl Pellerin. Sensor Network Detects Nuclear Blasts Worldwide. http://www.defense.gov/news/newsarticle.aspx?id=64640, 2011. [31] John Pike. AFTAC Introduction. http://www.fas.org/irp/agency/aftac/intro.htm, 1997.