sec16mctlg

Department of Defense

MILITARILY CRITICAL TECHNOLOGIES

LIST SECTION 16: POSITIONING NAVIGATION AND TIME TECHNOLOGY

August2009

Under Secretary of Defense, Acquisition, Technology and Logistics Pentagon, VA

PREFACE

A. THE MILITARILY CRITICAL TECHNOLOGIES PROGRAM (MCTP)

The MCTP supports the development and promulgation of the congressionally mandated Militarily Critical Technologies List (MCTL) and the Developing Science and Technologies List (DSTL).

Congress assigns the Secretary of Defense the responsibility of providing a list of militarily critical technolo-gies (the MCTL) and of updating this list on an ongoing basis. The MCTL identifies technologies crucial to weapons development and has been a key element in evaluating U.S. and worldwide technological capabilities. The MCTP has provided the support for a wide range of assessments and judgments, along with technical justifications for devising U.S. and multilateral controls on exports. The DSTL, another MCTP product, identifies technologies that may enhance future military capabilities and provides an assessment of worldwide science and technology (S&T) capabilities.

The MCTP process is a continuous analytical and information-gathering process that refines data and updates existing technology lists to provide thorough and complete technical information. It covers the worldwide technology spectrum and provides a systematic, ongoing assessment and analysis of technologies and determines values and parameters for these technologies.

Technology Working Groups (TWGs), which are part of this process, provide a reservoir of technical experts who can assist in time-sensitive and quick-response tasks. TWG chairpersons continuously screen technologies and nominate items to be added or removed from the MCTL and DSTL. TWG members are subject matter experts (SMEs) from the military Services, DoD and other federal agencies, industry, and academia. A balance is maintained between public officials and private-sector representatives. TWGs collect a core of intellectual knowledge and reference information on an array of technologies, and these data are used as a resource for projects and other assignments. Working within an informal structure, TWG members strive to produce precise and objective analyses across dissimilar and often disparate areas. Currently, the TWGs are organized to address 20 technology areas:

Aeronautics Information Systems Armament and Energetic Materials Lasers, Optics, and Imaging Biological Processing and Manufacturing Biomedical Marine Systems Chemical Materials and Processes Directed Energy Systems Nuclear Systems Electronics Positioning, Navigation, and Time Energy Systems Signature Control Ground Systems Space Systems Information Security Weapons Systems

B. THE MILITARILY CRITICAL TECHNOLOGIES LIST (MCTL)

DODI 3020.46, The Militarily Critical Technologies List (MCTL) establishes policy, assigns responsibilities, and prescribes procedures for developing and maintaining the MCTL. The MCTL provides a coordinated description of technologies that DoD assesses are essential to the design, development, production, operation, application, or maintenance of an article or service which makes or could make a significant contribution to the military potential of any country, including the United States. This includes, but is not limited to, design and manufacturing know-how, technical data, keystone equipment, and inspection and test equipment. It includes discrete parameters for systems; equipment; subassemblies; components; and critical materials; unique test, inspection, and production equipment; unique software, development, production, and use know-how; and worldwide technology capability assessments.

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C. LEGAL BASIS FOR THE LIST OF MILITARILY CRITICAL TECHNOLOGIES

The Export Administration Act (EAA) of 1979 assigned responsibilities for export controls to protect technologies and weapons systems. It established the requirement for DoD to compile a list of militarily critical technologies. Specifically the EAA stated: (5)(d)(2) The Secretary of Defense shall bear primary responsibility for developing a list of militarily critical technologies. In developing such list, primary emphasis shall be given to--

(A) arrays of design and manufacturing know-how, (B) keystone manufacturing, inspection, and test equipment, (C) goods accompanied by sophisticated operation, application, or maintenance know-how, and (D) keystone equipment which would reveal or give insight into the design and manufacture of a

United States military system, which are not possessed by, or available in fact from sources outside the United States to, controlled countries and which, if exported, would permit a significant advance in a military system of any such country.

(3) The list referred to in paragraph (2) shall be sufficiently specific to guide the determinations of any official exercising export licensing responsibilities under this Act.

The EAA and its provisions, as amended, were extended by Executive Orders and Presidential directives.

D. USES AND APPLICATIONS

The MCTL is not an export control list. It is DoDs recommendation for what should be controlled. When goods are identified as being militarily critical, the technology for the development or production is also recommended for control. The document is to be sufficiently specific for evaluating potential technology transfers and has been used for reviewing technical reports and scientific papers for public release. Technical judgment must be used when applying the information. It should be used to determine if the proposed transaction would result in a transfer that would give potential adversaries access to technologies whose specific performance levels are at or above the characteristics identified as militarily critical. It should be used with other information to determine whether a transfer should be approved.

The first list of militarily critical technologies that was published in the Federal Register on October 1, 1980 said that, Some of these technologies will be recommended for control on the USML. This has been the practice since. The linkage was confirmed by the Secretary of Defense/Secretary of State Defense Trade Security Trade Initiative (DTSI) of May 2000. One of its measures, DTSI #17 was to: Review/Revise the U.S. Munitions List: The process would involve a four-year review cycle, where one-quarter of the USML would be reviewed each year. The objective would be to comport what is controlled by the USML more directly with the Military Critical Technologies List. Thus, while the focus of the MCTL is on dual use technologies, defense article/technologies may also be included.

This document, MCTL Section 16: Positioning Navigation and Time Technology supersedes MCTL Section 16, Positioning Navigation and Time Technology, July 2007.

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INTRODUCTION

A. ORGANIZATION OF THE MILITARILY CRITICAL TECHNOLOGIES LIST (MCTL)

The MCTL is a documented snapshot in time of the ongoing MCTP militarily critical technology process. It includes text and graphic displays of technical data on individual technology data sheets.

Each section contains subsections devoted to specific technology areas. The section front matter contains the following:

Scope identifies the technology groups covered in the section. Each group is covered in a separate subsection.

Highlights identify the key facts in the section. Overview discusses the technology groups identified under Scope. Background provides additional information. Each technology group identified under Scope has a subsection that contains the following:

Highlights identify the key facts found in the subsection. Overview identifies and discusses technologies listed in data sheets that follow. Background provides additional information. Data Sheets, which are the heart of the MCTL, present data on individual militarily critical technologies.

The principal data element is the Critical Technology Parameter, which is the technology parameter that defines where the technology would permit significant advances in the development, production and use of military capabilities of potential adversaries.

B. TECHNOLOGY DATA SHEETS

The technology data sheets are of primary interest to all users. They contain the detailed parametric information that export control policy makers and licensing officials need to execute their responsibilities.

Critical Technology Parameter(s) includes the parameter, data argument, value, or level of the technology which would permit significant advances in the development, production and use of military capabilities of potential adversaries.

Critical Materials are those materials that are unique or enable the capability or function of the technology. Unique Test, Production and Inspection Equipment includes that type of equipment that is critical or

unique. Unique Software is software needed to produce, operate, or maintain this technology that is unique. Major Commercial Applications addresses commercial uses of this technology. Affordability Issues are those factors that affect the cost of the technology. Export Control References indicate international and U.S. control lists where this technology is controlled.

Note: Export control references are: WA ML 2 (Wassenaar Arrangement Munitions List Item) WA Cat 1C (Wassenaar Dual Use List Subcategory) MTCR 17 (Missile Technology Control Regime Item) NTL B3 (Nuclear Trigger List Subitem Nuclear Suppliers Group) NDUL 1 (Nuclear Dual Use List Item Nuclear Suppliers Group) AG List (Australia Group List) BWC (Biological Weapons Convention) CWC (Chemical Weapons Convention)

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USML XII (United States Munitions List Category ITAR) CCL Cat 2B (Commerce Control List Subcategory EAR) NRC A (Nuclear Regulatory Commission Item)

Background provides a description of the technology.

SECTION 16 - POSITIONING NAVIGATION AND TIME TECHNOLOGY

Scope

16.1 Inertial Navigation Systems and Related Components

16.2 Gravity Meters and Gravity Gradiometers

16.3 Radio, Acoustic and Data-Based Referenced Navigation (DBRN) Systems

16.4 Magnetic and Electromagnetic Sensor Systems

16.5 Precise Time and Frequency

Highlights

Inertial navigation system technologies provide an autonomous, covert, and nonjammable three-dimensional (3-D) position and velocity reference for military weapon systems. Advances in commercial hybrid inertial navigation systems embedded with Global Positioning System (GPS), Doppler or data-based referenced navigation (DBRN) systems provide a significant capability to potential adversaries against the U.S. forces and its allies.

GPS is the most accurate worldwide standard for positioning, navigation, and time (PNT) dissemination. These capabilities provide a very accurate positioning and time (POSITIME) system for combat situational awareness to the U.S. forces and its allies, as well as potential adversaries. Anti-jam capability in GPS receivers can provide a significant additional capability to an adversary that is a concern.

Precise time and frequency (PT&F) are required for autonomous operation of terrestrial and satellite geolocation systems and enhanced transmission security in spread-spectrum systems. The importance of PT&F has only recently been recognized because of the availability and accuracy of GPS time.

Low power clocks and oscillators that are now in advanced development will perform at or near the accuracy level of current atomic clocks and provide a significant capability to potential adversaries against the U.S. forces and its allies.

Improvements in gravity meter and gradiometer arrays and satellite sensor systems provide increased detection and location of submarines, mines, tunnels, and mobile missile launchers.

Magnetic and electromagnetic sensor and array technology for covert detection and classification is evolving because of better sensors, advances in processor speed and memory capacity, and integration with PT&F devices and geo databases.

Low probability of intercept/low probability of detection (LPI/LPD) radar altimeters integrated with greatly improved terrain databases provide a military alternative to GPS, particularly in a jamming environment.

OVERVIEW

This section covers technologies for both autonomous and cooperative PNT systems for the coordination and control of military force elements. All of these technologies have dual-use requirements, and all of them are essential for various military missions.

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Section 16.1 includes inertial systems and components that form the basis for autonomous, covert navigation and motion sensing. Included are inertial navigation systems, various types of integrated or hybrid inertial navigation systems, and many distinct types of gyroscopes and accelerometers that can be found in a navigation system. Also included are gyro astro trackers and azimuth determination systems that require gyroscopic systems for a stable level reference. Technologies below the gyroscope and accelerometer sensor level (i.e., fiber-optic cables) are included in Section 10, Information Technology. Hybrid systems bound the time-dependent errors of the inertial sensors. Accuracy of position and time provides a more robust navigation system. Further improvements in hybrid inertial navigation system performance are expected.

Section 16.2 includes both gravity meters and gravity gradiometers for ground use or mobile use. Continuing improvements in gravity sensors are enabling better positioning updates for inertial navigation system error compensation, strategic arms treaty verification, and detection of tunnels and terrain estimation.

Section 16.3 covers a limited category of militarily critical radio, acoustic and DBRN technology and systems having a wide range of dual-use applications. Under radio navigation, only Global Navigation Satellite System (e.g., GPS, GLONASS and GALILEO) receivers are included. The U.S. GPS consists of three segments: (1) space systems (including satellites), (2) satellite command and control systems, and (3) user receivers and associated equipment. Only the last is included in this section; refer to Section 19, Space Systems Technology for (1) and (2). Under acoustic navigation, both active and passive underwater acoustic Doppler/sonar navigation systems are included. Under DBRN, only underwater bathymetric, magnetic and gravity DBRN systems are included as well as LPI/LPD radar altimeters/fathometers.

Section 16.4 covers the technology relative to magnetometers of various types, including active electromagnetic sensors, underwater electric field sensors, magnetic gradiometers, and arrays composed of magnetic and electric field sensors. Magnetic sensor systems detect and display the presence of a magnetic field and measure its magnitude or direction. Magnetic sensor types of special interest include superconducting quantum interference device (SQUID), nuclear precession, optically pumped, induction coil, flux gate, and fiber optic. Magnetic sensor systems can be configured to detect the spatial variation of the magnetic field intensity from sources external to the instrument, that is, the gradient of the magnetic field intensity. In this mode they are called magnetic gradiometers.

Section 16.5 includes two PT&F technology areas: atomic clocks (used in ground stations and satellites) and low power clocks and oscillators (used in inertial navigation systems and receivers). Most types of positioning and navigation (POSNAV) systems are highly dependent on precise time, but other applications depend on frequency and not absolute time (refer to Section 16.3 for GPS as a timing distribution system).

BACKGROUND

Over the past 10 years, PNT technologies have been highly affected by advances in computer throughput, memory, and algorithms, as well as miniaturization and reliability of electronic components. These technologies, in turn, have been highly influenced by advances in material, manufacturing, and fabrication technologies. The applications of satellite PNT technologies, particularly the U.S. GPS, has had an enormous positive impact on military and commercial users, especially the telecommunications industry, which has had a need for accurate time.

The American Practical Navigator by Bowditch can be viewed at http://www.irbs.com/bowditch/ and provides general information on navigation and positioning, its history, and its instruments.

16.1 INERTIAL NAVIGATION SYSTEMS AND RELATED COMPONENTS

Highlights

Inertial navigation system (INS) technologies provide an autonomous, covert, and nonjammable 3-D position, attitude, heading, and velocity reference for potential adversaries for navigation, guidance for weapons of mass destruction and other military weapons.

The performance levels for commercial and military (aircraft and ground use) inertial navigation systems have stayed at their respective levels of 1.0 and 0.8 nmi/hour CEP over the last 20 years. The difference between commercial and military use is mainly in the environment that the performance must be achieved.

Emergence of fiber-optic gyroscope and microelectromechanical systems (MEMS) gyroscope and accelerometer technology provides the ability to survive in a high-g environment for applications in tactical missiles, gun-launched projectiles and smart weapons.

Commercial application for hybrid inertial navigation systems with embedded GPS, Doppler/SONAR, DBRN and/or low power clock technology have increased over the past several years and will continue to increase as their cost, weight, and size improve. These hybridized systems provide a very precise navigation and guidance capability.

Built-in redundancy through low-cost, small-size, lightweight, and highly reliable components allows an affordable, throwaway logistics concept. This will enable a rapid and affordable technology insertion of emerging inertial navigation system technology. The challenge will be to protect transfer of older technology to potential adversaries that can be used against the United States and its allies.

OVERVIEW

This section of PNT includes inertial systems and components that form the basis for autonomous, covert navigation and motion sensing. Included are inertial navigation systems, various types of integrated or hybrid inertial navigation systems, and each of many distinct types of gyroscopes and accelerometers that can be found in a navigation system. The inertial measurement unit provides delta-angle (sometimes referred to as delta theta) and delta velocity outputs for use by the vehicle or the system performing the navigation. Synonymous terms include, but are not limited to, inertial reference unit, inertial sensor assembly, and inertial sensor unit. These subassemblies have the militarily critical parametric levels of the inertial instruments (gyroscopes and accelerometers) used therein. An attitude and heading reference system (AHRS) provides attitude and heading, but does not necessarily provide a complete navigation solution. An AHRS may also provide velocity, angular rate, and acceleration data. An AHRS is protected at the level of the inertial instruments (gyroscopes and accelerometers) used therein. Both gyro astro trackers and azimuth-determination systems require gyro systems for reference (level). Not included in this section are technologies below the gyroscope and accelerometer sensor level (i.e., fiber-optic cables).

BACKGROUND

An inertial navigation system is a self-contained system that provides a capability to continuously estimate a weapons systems position, velocity, acceleration, attitude, angular rate, and often guidance or steering inputs. An inertial navigation system contains accelerometers and gyroscopes to sense linear and angular rate. The system can be mechanized as a gimbaled platform, as a strapdown inertial sensing unit employing a computer to provide the software equivalent of gimbals, or as a hybrid unit with both gimbal and strapdown features. Hybrid systems bound the time-dependent errors of the inertial sensors or systems, resulting in a more robust nonjammable navigation system. Further improvement in hybrid inertial navigation system performance is expected to continue. A hybrid INS/DBRN can also provide an accurate autonomous, nonjamming, and covert navigation capability, independent of any GNSS. A gyro astro tracker or astro compass is an automated optical or radiometric sextant that tracks selected stars and provides true heading and position data by triangulation using the referenced stars. The system can operate

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day or night very accurately. The system requires a stable reference to level and is composed of components of, or hybridized with, an inertial navigation system.

LIST OF MCTL TECHNOLOGY DATA SHEETS 16.1 INERTIAL NAVIGATION SYSTEMS AND RELATED COMPONENTS

16.1-1 Inertial Navigation Systems and Related Components (including IMU)

16.1-2 Hybrid Inertial Navigation Systems (including GNSS and DBRN)

16.1-3 Gyro Astro-Tracking Devices

16.1-4 Azimuth (North-Pointing) Determination Systems

Gyroscopes and Angular Rate Sensors

16.1-5 Mechanical or Spinning Mass Gyroscopes

16.1-6 Hemispherical Resonator Gyroscopes

16.1-7 Optical Gyroscopes or Angular Rate Sensors

16.1-8 Microelectromechanical Systems (MEMS) Gyroscopes

Accelerometers

16.1-9 Linear Accelerometers (Other than MEMS)

16.1-10 MEMS Linear Accelerometers

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MCTL DATA SHEET 16.1-1. INERTIAL NAVIGATION SYSTEMS AND RELATED COMPONENTS (INCLUDING IMU)

An inertial navigation system (INS) is a self-contained, covert navigation system that provides continuous estimates of some or all components of a vehicle state, such as position, velocity, acceleration, attitude, angular rate, and often guidance or steering inputs.

Critical Technology Parameter(s)

Any inertial navigation system (gimbaled or strapdown) and inertial equipment that meets any of the following:

o Position, velocity, attitude, guidance, or control, having a navigation error (free inertial) after normal alignment/calibration of 0.8 nmi/hour (CEP) or less (better);

o Having an azimuth accuracy of less (better) than 6 arc minutes rms at 45 degrees latitude;

o Contains accelerometers or gyroscopes that are militarily critical;

o Capable of functioning at continuous acceleration levels exceeding 10 g; or

o Designed to have a non-operating shock level of 900 g or greater at a duration of 1 millisecond, or greater.

Any inertial measurement equipment including Inertial Measurement Units (IMU) that: (1) contains accelerometers or gyroscopes that are militarily critical; and, (2) meets same shock level as INS. Excludes INS which is certified for use on civil aircraft by FAA.

Critical Materials None identified. Unique Test, Production, Inspection Equipment

Components requiring specially designed test, calibration, or alignment equipment for test, calibration, alignment, or production. Ship-motion simulator capable of motion with three or more simultaneous degrees of freedom.

Unique Software Software specially designed or modified to improve the operational performance or reduce navigational error to the levels specified above. Source code for inertial navigation system for autonomous use. Source code, algorithms, and verified data needed to meet militarily critical parameters. Software for optimizing inertial navigation system alignment time for moving platforms and transfer alignment techniques. Algorithms for gyro compensation.

Major Commercial Applications

Aviation, ships, space, and land vehicles.

Affordability Issues Accuracy is a cost driver. Reduced costs are attendant with strapdown systems and production base.

Export Control References

WA ML 11.a (Note: g); WA Cat 7.A.3.a; MTCR 9.A.6; USML VIII(e)(Component); CCL Cat 7A003.a.

BACKGROUND

The INS is made from a navigation computer and a set of gyroscopes and accelerometers, generally called inertial sensors that measure a Newtonian inertial reference frame. Gyroscopes measure rotation or angular rate, and accelerometers measure acceleration. Integrating the output from an accelerometer gives speed, and integrating speed gives distance traveled. The gyroscopes provide information on where the accelerations are directed, and therefore heading and distance, the essential ingredients for dead reckoning, are known.

The inertial sensors might be mounted in a set of gimbals so that they (1) stay level in a fixed direction no matter how the vehicle moves, i.e., space stable INS; or (2) remains parallel to the reference ellipsoid, i.e., a local level INS. Both of these are called a gimbaled system. As an alternative, the inertial sensors might be attached to the vehicle, in which case they measure its motion components in the vehicle axes by transforming the measurements from the vehicle axes to the reference axes. This is called a strapdown system.[1]

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Inertial measurement equipment includes the inertial navigation unit, inertial measurement unit, inertial reference unit, inertial sensor assembly, or inertial sensor unit which are subassemblies of an inertial navigation system; a self-contained, covert system that provides continuous estimates of some or all components of a vehicle state, such as position, velocity, acceleration, attitude, angular rate, and often guidance or steering inputs. It also includes an Attitude Heading Reference System (AHRS) or Gyrocompass that provides attitude and magnetic heading, but does not provide a complete navigation solution. An AHRS or Gyrocompass may provide velocity, angular rate, and acceleration data in addition to attitude and heading. This system may be combined into hybrid systems to complete the navigation function.

1. Anthony Lawrence, Modern Inertial Technology, 1998.

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MCTL DATA SHEET 16.1-2. HYBRID INERTIAL NAVIGATION SYSTEMS (INCLUDING GNSS AND DBRN)

Hybrid INS/GNSS/DBRN systems combine the best features of different navigation systems to provide a very accurate navigation capability that is autonomous, covert, and nonjammable.


Any hybrid (the terms hybrid and integrated are the same) inertial navigation system (gimbaled or strapdown) having any of the following:

1. Embedded with GNSS receiver or DBRN System(s) having a navigation position accuracy, after loss of GNSS;

2. DBRN for a period of up to 4 minutes, of less (better) than 10 meters CEP; 3. Embedded with any INS, IMU, GNSS receiver or a DBRN system that is

militarily critical; or 4. Embedded with any gyroscope or accelerometer that is militarily critical.

Critical Materials Tamper-resistant thermal-spray technology to protect components containing sensitive U.S. cryptographic logic.

Unique Test, Production, Inspection Equipment

Components that require specially designed test, calibration, or alignment equipment. GNSS receivers that require use of military-capable, signal-simulator testing systems. Systems that simulate/generate the specialized radio-frequency signal and data message structure and require the use of U.S. cryptography. Any antispoofing signal simulators.

Unique Software Software specially designed or modified to meet militarily critical parameters. Source code for inertial navigation systems for hybridized use. Source code, algorithms, and verified data needed to meet militarily critical parameters with any of following navigation data: Doppler radar or sonar, GNSS, or DBRN (acoustic, stellar, gravity, and magnetic databases, or 3-D digital terrain maps and other geomapping data). Source code for integrated INS equipment, sensors and processors that meet or exceed militarily critical parameters.


Aviation, ships, space, and land vehicles.

Affordability Issues Not an issue. Export Control References

WA ML 11.a (Note: g); WA Cat 7.A.3.b; MTCR 9.A.7, 11; USML VIII(e)(Component); CCL Cat 7A003.b.

BACKGROUND

Hybrid inertial navigation systems provide the means to accurately locate forces and infrastructures with minimal detectability.

The hybrid INS/navigation system include Doppler (sonar, laser, radar) that can provide a very accurate navigation system independent of GNSS.

In all cases, the INS provides a flywheel effect for continuous accurate navigation, even when the other navigation signals are lost (intentionally or not).

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MCTL DATA SHEET 16.1-3. GYRO ASTRO-TRACKING DEVICES

Gyro astro-tracking devices or star trackers are a type of telescope on a stable (gyroscopic) platform with an optical detector array at its focus, which can be precisely pointed at a star whose location is known.


1. Any gyro astro compasses, and other devices which derive position or orientation by means of automatically tracking celestial bodies or satellites, with an azimuth accuracy equal to or less (better) than 6 seconds of arc.

2. Any zenith camera used to determine vertical deflection to better than 0.1 seconds of arc and with the ability to rapidly measure at multiple sites.


Components require specially designed test, calibration, or alignment equipment including clock accuracy of a microsecond per 24 hours. Star simulators required.

Unique Software Algorithms and verified data needed to exceed militarily critical parameters. Source code for combining an inertial navigation system with a gyro astro tracker is unique. Gyro astro tracker stabilization requires accurate initialization and reference data from an inertial navigation system.


None identified.

Affordability Issues Very expensive because of low volume requirements and technical complexity. Export Control References

WA Cat 7.A.4; MTCR 9.A.2; USML VIII(e)(Component); CCL Cat 7A004.

BACKGROUND

The star tracker in a gyro astro-tracking device locks onto the preselected star and uses the stars known position to determine the vehicles position. These devices are immune from jamming, but are affected by atmospheric turbulence, such as smoke and haze. Star trackers are expensive and require a window in a vehicle.[1] Zenith cameras are used to determine the deflection of the vertical at a fixed site. If these instruments can be used to make very accurate measurements very quickly, they can provide data valuable for initializing the guidance systems of mobile ballistic missiles, or providing a reference grid of vertical deflections useful for compensating an inertial navigation system.

The following Web site describes applications of gyro astro-tracking devices:

Basics of Celestial Navigation: http://www.springerlink.com/content/n1624k7j11214312/.

Description of a zenith camera for determining deflection of the vertical: http://www.geodaesie-geodynamik.ethz.ch/research/wg18/.


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MCTL DATA SHEET 16.1-4. AZIMUTH (NORTH-POINTING) DETERMINATION SYSTEMS

Azimuth, or north-pointing systems use gyroscopes to precisely determine the orientation of the vehicle with respect to true geographic north.


Any inertial equipment having any of the following characteristics, and specially designed components therefore:

1. Having an azimuth, heading, or north pointing accuracy equal to or better than 6 arc minutes rms at 45 degrees latitude; or

2. Having a non-operating shock level of 900 g or greater at a duration of 1-msec, or greater.


Components require specially designed test, calibration, or alignment equipment.

Unique Software Algorithms and verified data needed for compensation. Major Commercial Applications

Satellite communications, bore sighting, geodesy, surveying, and construction.

Affordability Issues Not an issue. Export Control References

WA Cat 7.A.3.c and 7.A.4; MTCR 9.A.2; USML XIII(e); CCL Cat 7003.c and 7A004.

BACKGROUND

The rate gyroscope is used to measure Earths rotation rate (approximately 15 degrees/hour at the equator); this value is then used to compute the angle (of the vehicle) with respect to true north. The only external input required is the approximate latitude. This system offers a significant improvement over magnetic measurement techniques, which are susceptible to local anomalies in Earths magnetic field, distortion caused by ferrous metals, and currents in the equipment to which it is mounted.

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MCTL DATA SHEET 16.1-5. MECHANICAL OR SPINNING MASS GYROSCOPES

The mechanical or spinning mass gyroscope includes floated gyroscopes, dynamically tuned gyroscopes and electrostatically supported gyroscopes.


Any mechanical or spinning gyroscope having any of the following capability:

1. A drift-rate stability, when measured in a 1-g environment over a period of 1 month, and with respect to a fixed calibration value of less (better) than 0.5 degree/hour when specified to function at linear acceleration levels up to and including 100 g; or

2. Specified to function at linear accelerations levels exceeding 100 g.


Equipment specially designed for the production of this equipment, including:

1. Gyro tuning test stations; 2. Gyro dynamic balance stations; 3. Gyro run-in/motor test stations; 4. Gyro evacuation and fill stations; or 5. Centrifuge fixtures for gyro bearings.

Unique Software Algorithms and verified data needed to exceed militarily critical parameters. Error compensation for environmental effects and differing technology characteristics.


Aviation, ships, land and space vehicles, robotics, manufacturing, and stability reference (cameras, telescopes, etc.).

Affordability Issues Accuracy is a cost driver. Reduced costs are attendant with optical gyroscopes. Use of MEMS will further reduce cost of gyroscopes.


WA ML 11.a (Note: g); WA Cat 7.A.3.c and 7.A.4; MTCR 9.A.4; USML VIII(e) (Component); CCL Cat 7A003.c and 7A004.

BACKGROUND

Mechanical or spinning mass gyroscopes include floated gyroscopes, dynamically tuned gyroscopes and electrostatically supported gyroscopes.

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MCTL DATA SHEET 16.1-6. HEMISPHERICAL RESONATOR GYROSCOPES

The hemispherical resonator gyroscope is a fused-quartz hemispheric vibrating shell supported by a stem along a diameter, like a wineglass with its stem continued into the bowl.


Any gyroscope having any of the following capability:

1. A drift-rate stability, when measured in a 1-g environment over a period of 1 month, and with respect to a fixed calibration value of less (better) than 0.5 degree/hour when specified to function at linear acceleration levels up to and including 100 g; or



None identified.



None identified.

Affordability Issues Extremely costly because of low production quantities; cost decreases as production increases.


WA ML 11.a (Note: g); WA Cat 7.A.3.c and 7.A.4; MTCR 9.A.4; USML VIII(e)(Component); CCL Cat 7A003.c and 7A004.

BACKGROUND

The hemispherical resonator gyroscope shell is electrostatically excited at its natural frequency by an alternating current (AC) signal applied to fixed electrodes on the case. A servo system drives the shell to resonance and maintains the oscillation amplitude constant. Because the internal damping of quartz is so low and the enclosure is evacuated, little energy needs to be supplied to maintain resonance. The hemispherical resonator gyroscope continues to resonate when power is removed. Thus, it remembers rotations occurring while it is temporarily unexcited. This memory could be useful in guidance systems for missiles that have to operate near nuclear blasts. The hemispherical resonator gyroscope is expensive to manufacture because its performance comes from the precise manufacturing of the shell and housing and the high vacuum sealing.[1]


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MCTL DATA SHEET 16.1-7. OPTICAL GYROSCOPES OR ANGULAR RATE SENSORS

Optical Gyroscopes or Angular Rate Sensors include Ring Laser Gyroscopes (RLGs) and Fiber Optic Gyroscopes (FOGs).


Any ring laser or fiber optic gyroscope or angular rate sensor that meets any of the following:

1. Having a drift-rate stability, when measured in a 1-g environment over a period of 1 month, and with respect to a fixed calibration value of less (better) than 0.5 degree/hour when specified to function at linear acceleration levels up to and including 100 g;

2. Having an angle random walk of less (better) than or equal to 0.0035 deg/hour;

3. Having a drift rate stability, over a period of three minutes, of less (better) than 40 degrees/hour when specified to have any of the following characteristics: 1) An input rate range greater than or equal to 500 degrees/second; or 2) An ARW of less (better) than or equal to 0.2 degree per square root hour; or


Note: Drift rate stability is measured with respect to a fixed calibration value and at a constant temperature.


Fiber optic gyro coil winding machines; Scattermeters having a measurement accuracy of 10 ppm or less (better); Profilometers having measurement accuracy of 0.5 nm (5 angstrom) or less (better).



Aviation, ships, land and space vehicles, and robotics.

Affordability Issues High cost for initial national capability because clean rooms and ultra-clean, high-vacuum equipment are required. High production base will reduce cost.


WA ML 11.a (Note: g); WA Cat 7.A.3.a; MTCR 9.A.4; USML VIII(e)(Component); CCL Cat 7A003.a.

BACKGROUND

Invented in the 1960s, the ring-laser gyroscope is an active-resonator optical gyroscope. A laser, the optical oscillator, is used as the light source. When used in a Fabry-Perot resonator with three or more mirrors making the light circulate through an enclosed-glass, waveguide medium, a beam splitter is used to provide clockwise and counterclockwise light beams. Both clockwise and counterclockwise waves will be generated; these will resonate when the path perimeter is an integral number of wavelengths, and the two waves will form a standing-wave pattern. Such a laser is called a ring laser.

As the ring-laser gyroscope is rotated about an axis normal to the resonator plane, the difference in transit time (or frequency shift) of the light beam traveling in opposite directions is proportional to the rotation rate. This is called the Sagnac effect.[1] Ring-laser gyroscopes are replacing conventional spinning-mass gyroscopes in many inertial navigation system applications because of their stability, high accuracy, high reliability, and low costs.

Like the ring laser gyroscope, the fiber-optic gyroscope was also invented in the 1960s, but developed more slowly. Its development tracked the communications industry light source and optical fiber developments. A fiber-optic gyroscope uses the Sagnac effect to determine rotation rate. The Sagnac effect results from the counter-propagation of light beams in an optical waveguide consisting of a coil of optical fiber, where the number of turns and diameter affect the accuracy of rotation-rate measurement. The

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difference of frequency is the optical reciprocity between clockwise and counterclockwise paths of the light beams. Rotation normal to the waveguide upsets the symmetry, which is then photoelectronically detected and processed to provide an indication of rotation rate.


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MCTL DATA SHEET 16.1-8. MICROELECTROMECHANICAL SYSTEMS (MEMS) GYROSCOPES

Any gyroscope using an electro-mechanically driven resonator in accordance with the dynamic theory that when an angular rate is applied a Coriolis force is generated proportional to the applied angular rate.


Any MEMS gyroscopes:

1. Having a drift rate stability, over a period of three minutes, of less (better) than 40 degrees/hour when specified to have any of the following characteristics: 1) An input rate range greater than or equal to 500 degrees/second; or 2) An ARW of less (better) than or equal to 0.2 degree per square root hour; or


Note: Drift rate stability is measured with respect to a fixed calibration value and at a constant temperature.


Specially designed test, calibration, or alignment equipment. Gyroscope axis alignment fixture. The fabrication process relies on commonly available semiconductor process equipment, including high-precision lithography, ion milling, plasma arc, and electronic-sputtering production equipment.

Unique Software Algorithms and verified data needed to exceed militarily critical parameters. Error compensation for environmental effects and technology characteristics.


Vehicle control and robotics.

Affordability Issues None identified. Export Control References

WA ML 11.a (Note: g); WA Cat 7.A.1, 2 and 3; MTCR 9.A.4; USML VIII(e)(Component); CCL Cat 7A001, 7A002 and 7A003.

BACKGROUND

A MEMS gyroscope is usually designed as an electromechanically driven resonator, often fabricated out of a single piece of quartz or silicon. Most MEMS gyroscopes operate in accordance with the dynamic theory that when an angle rate is applied to a body, a Coriolis force is generated. When this angle rate is applied to the axis of a resonating tuning folk, its prongs receive a Coriolis force proportional to the applied angular rate. This force can be measured capacitively (silicon) or piezoelectrically (quartz).[1]

Many manufacturers are developing these MEMS gyroscopes to reduce the cost of inertial sensors in commercial applications, as well as opening new applications because of their reduced size and weight compared to existing traditional gyroscopes.


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MCTL DATA SHEET 16.1-9. LINEAR ACCELEROMETERS (OTHER THAN MEMS)

A linear accelerometer is a device that senses the acceleration in one direction.


Any linear accelerometer having the following:

Specified to function at linear acceleration levels less than or equal to 15 g and having any of the following:

o A bias stability of less (better) than 130 g with respect to a fixed calibration value over a period of 1 year; or

o A scale factor stability of less (better) than 130 ppm with respect to a fixed calibration value over a period of one year.

Specified to function at linear acceleration levels exceeding 15 g and having all of the following:

o A bias repeatability of less (better) than 5,000 micro g over a period of one year; and

o A scale factor repeatability of less (better) than 2,500 ppm over a period of one year.

Designed for use in inertial navigation or guidance systems and specified to function at linear acceleration levels exceeding 100 g.


Specially designed test, calibration, or alignment equipment. Accelerometer axis-alignment stations and programmable dividing head.



Aviation, ships, land and space vehicles, robotics, manufacturing reference, geodesy, and seismic detection.

Affordability Issues Not an issue, except for extremely accurate sensors with low quantity requirements. Export Control References

WA ML 11.a (Note: g); WA Cat 7.A.1; MTCR 9.A.3; USML VIII(e)(Component); CCL Cat 7A001.

BACKGROUND

A basic linear accelerometer is a single-degree-of-freedom accelerometer made up of at least the following elements: 1) a mass, often called the proof mass; 2) a suspension, which locates the mass; and 3) a pickoff, which puts out a signal related to the acceleration sensed.

There are two types of linear accelerometers, open loop and closed loop. The former will have a mass on a spring hinge as the sensing element. This is called an open-loop pendulous accelerometer. A pickoff will measure the angular deflection of the sensing element, which is the accelerometers output. Because of this deflection, the accelerometer can suffer from cross-coupling acceleration and vibrations. Open-loop accelerometers are satisfactory where dynamic range does not exceed 5,000 to 1 and where scale-factor error can be 0.1 percent or more.

Where higher performance is needed, it is better to use a closed-loop pendulous accelerometer. The closed-loop sensor relies on the feedback system to restrain the sensitive element under high acceleration and rotations. Closed-loop pendulous accelerometer designs vary with different kinds of materials and sensitivities of the core three elements.[1] Until the 1990s, most accelerometers were produced using other than micromachined techniques.


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MCTL DATA SHEET 16.1-10. MEMS LINEAR ACCELEROMETERS

A linear accelerometer is a device that senses the acceleration in one direction.


Any MEMS linear accelerometer having the following:

Specified to function at linear acceleration levels less than or equal to 15 g and having any of the following:

o A bias stability of less (better) than 130 g with respect to a fixed calibration value over a period of 1 year; or

o A scale factor stability of less (better) than 130 ppm with respect to a fixed calibration value over a period of one year.

Specified to function at linear acceleration levels exceeding 15 g and having all of the following:

o A bias repeatability of less (better) than 5,000 micro g over a period of one year; and

o A scale factor repeatability of less (better) than 2,500 ppm over a period of one year.

Designed for use in inertial navigation or guidance systems and specified to function at linear acceleration levels exceeding 100 g.


Specially designed test, calibration, or alignment equipment. Accelerometer axis-alignment stations. The fabrication process relies on commonly available semiconductor process equipment, including high-precision lithography, ion-milling, plasma-arc, and electronic-sputtering production equipment.



Safety air bags and dynamic vehicle control.


WA ML 11.a (Note: g); WA Cat 7.A.1; MTCR 9.A.3 and 5; USML VIII(e)(Component); CCL Cat 7A001.

BACKGROUND

The microelectronics field has made pure single-crystal silicon readily available, and silicon has excellent mechanical properties: 1) harder than most metals; 2) higher elastic limits in both tension and compression than steel; and, 3) negligibly small hysteresis and virtually infinite fatigue life. By using an anistropic-etching process, it can be made into microscopically small devices, including accelerometers.

There are many designs of silicon accelerometers, from a simple pendulum to a tuning fork. There are also numerous other types. This is a relatively new technology area. MEMS sensors are one-tenth the cost of the electromechanical sensors they replace. This reduced cost will dramatically change the inertial sensor business, just as integrated circuits changed electronics.[1]


16.2 GRAVITY METERS AND GRAVITY GRADIOMETERS

Highlights

Uncompensated gravity disturbances are a large error source for inertial navigation system initialization and subsequent field operation. Evolving gravity models are enabling better inertial navigation system error compensation.

Use of a worldwide gravity database based on better instrumentation and having greater computer capabilities, in conjunction with on-board gravity sensors, provides autonomous and continuous updates to inertial navigation systems, yielding accuracy or noise level comparable with projected inertial navigation system/GPS hybrid systems for short periods of time.

Gravity meter and gravity gradiometer arrays with accurate time sequencing, faster computer speeds, and memory advances can provide improved detection and location of submarines, mines, tunnels, and mobile missile launchers.

An evolving technology to compute real-time gravity data from a moving research platform using the difference in acceleration data from an uncompensated inertial navigation system and the GNSS has been demonstrated.

OVERVIEW

This section on gravity sensors includes both gravity meters and gravity gradiometers used in either ground (fixed) or mobile (moving base) applications. These sensors can be used for detecting variations in mass distributions, either on local or global scales. Practical applications include detection of ore bodies or faults and generating a worldwide gravity database that can then be used for navigation-system error compensation. Refer to Inertial Navigation Systems, Section 16.1, and to DBRN, Section 16.3, for mobile use measurements. For mobile gravity or gravity gradient measurements, compensation techniques must be used to remove the noise and errors caused by the motion (acceleration) of the system and the mass of the compensation instrumentation. This generally requires a stable reference that can be obtained using gyros. The accuracy or noise level of the system is a function of the system stability and the complexity of the mechanical, electronic, and software compensation systems. A gradiometer in principle is immune to the effects of linear acceleration of the platform and the velocity-dependent interactions with the rotation of Earth. However, in practice, vibration and rotational motion must be accounted for in order to improve accuracy.

BACKGROUND

There are many methods of measuring or computing quantities related to the Earths gravity field.[1] For instance, an absolute measurement of gravity acceleration can be made using accurate timing of a falling weight or a swinging pendulum in a controlled environment. A cold atom interferometric gravimeter can also make an absolute measurement by observing the acceleration of a cloud of cooled Rubidium atoms.[2] A relative gravity measurement can be accomplished by using a gravity meter (gravimeter) based on the deflection of a spring. The most commonly used unit for the acceleration of gravity is the milligal (the unit gal is named after Galileo, the unit symbol is Gal, and 1 Gal is defined as 1 cm/sec2). The earths gravity field ranges from about 983,000 mGal at the poles to about 978,000 mGal at the equator, so the generally desired accuracy of 1 mGal represents about 1 part per milliona challenging requirement for mechanical instruments. Precise gravimeters today are designed for microgal (mGal) accuracy.

Global observations of the gravitational potential field are made by tracking the orbits of individual satellites, or carefully measuring the relative separation of pairs of satellites flying in formation.[3] Once the global potential of gravity (the geopotential) is modeled or computed, any gravity field quantity, (e.g., gravity anomaly, gravity gradients, deflection of the vertical, or geoid height) can be computed and mapped (at accuracies and resolution subject to the original measurements). For example, the model EGM 2008[4]

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was developed as the latest improvement to the WGS 84 geopotential. Global gravity maps are important for ballistic missile and inertial navigation accuracy; however, this section focuses on the more local-scale measurements made by gravimeters and gradiometers.

In its simplest form, a gradiometer is a set of gravimeters separated by a fixed distance, where the gradient is the difference in field values sensed by the gravimeters. The derivative of g is the gradient of gravity. The partial spatial derivatives of the gravity vector yield the gravity gradient tensor, consisting of nine elements. The gravity vector has three spatial components (x, y, and z), and derivatives are taken with respect to each of the spatial directions (x, y, and z) to yield the nine components of the tensor. The gravity gradient tensor (T) is symmetric about its diagonal, so six of the nine terms (Txx, Tyy, Tzz, Txy, Txz, Tyz) contain all the useful information.

1. Chapin, D., 1998, Gravity instruments: Past, present, future, The Leading Edge, January 1998, pp. 100112.

2. Cheinet et al., http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=01567407 (AND/OR any reference from Stanford/Kasevich?) e.g., Stanford Cold Atom Interferometer Gravity Gradiometer, McGuirk et al., 2001: http://arxiv.org/PS_cache/physics/pdf/0105/0105088v1.pdf.

3. http://www.csr.utexas.edu/grace/ 4. http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm2008/index.html

LIST OF MCTL TECHNOLOGY DATA SHEETS 16.2 GRAVITY METERS AND GRAVITY GRADIOMETERS

Gravity Meters

16.2-1 Gravity Meters (Gravimeters) for Ground Use

16.2-2 Gravity Meters (Gravimeters) for Mobile Use

Gravity Gradiometers

16.2-3 Gravity Gradiometers for Ground Use

16.2-4 Gravity Gradiometers for Mobile Use

CHANGES FROM LAST MCTL

Additions: None

Deletions: None

Changes: None

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MCTL DATA SHEET 16.2-1. GRAVITY METERS (GRAVIMETERS) FOR GROUND USE

Gravity meters used in a static base to measure the magnitude of the acceleration of gravity.


Any gravity meter (gravimeter) designed or modified for ground use having any of the following:

1. Having a static accuracy of less (better) than 0.1 mGal; or 2. Having any accelerometer or gyroscope that is militarily critical.


Equipment to produce, align and calibrate land-based gravity meters with a static accuracy of better than 0.1 mGal.

Unique Software Software specially designed to correct motional influences of gravity meters or gravity gradiometers.


Geodetic mapping, resource exploration, and mass detection.

Affordability Issues Highly specialized sensor system with few, but critical applications. Export Control References

WA ML 11.a (Note: g); WA Cat 6.A.7.a; MTCR 12.a.3; CCL Cat 6A007.a.

BACKGROUND

An absolute measurement of gravity can be made using accurate timing of a falling weight or a swinging pendulum in a controlled environment. Relative gravity measurements may be made in various ways. Three types of relative gravity instrumentsthe torsion balance, the pendulum, and the gravity meter (or gravimeter)have been used. Today, the spring-based technologies are preferred.[1]

Gravity meters can be used in a static or dynamic (moving) base to measure the magnitude of the acceleration of gravity. In a static environment, a gravity meter is capable of measuring Earths gravity to a greater degree of accuracy (microgal rather than milligal precisiongood enough to observe tides). However, dynamic (moving) gravity meter applications suffer from acceleration noise due to motion, and accuracy attainable now is on the order of a few to ten milligals. For mobile measurements, more electronics, software, and gyro stabilization is required to compensate for the motion effects on measured gravity.

1. Chapin, D., 1998, Gravity instruments: Past, present, future, The Leading Edge, January 1998, pp. 100112.

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MCTL DATA SHEET 16.2-2. GRAVITY METERS (GRAVIMETERS) FOR MOBILE USE

Gravity meters used in a mobile platform to measure the magnitude of the acceleration of gravity.


Any gravity meter (gravimeter) designed for mobile platforms, having any of the following:

1. Having an accuracy of less (better) than 10 mGal; or 2. Having any accelerometer or gyroscope that is militarily critical.





Geologic mapping and resource exploration.

Affordability Issues Cost is proportional to usage. This is not a high-volume production technology, but rather a highly specialized sensor system with only a few, but critical, applications.


WA ML 11.a (Note: g); WA Cat 6.A.7.b; MTCR 12.a.3; CCL Cat 6A007.b.

BACKGROUND

Absolute measurements of gravity cannot be made quickly enough to be done on a moving platform (except perhaps ultimately by improvements to the cold atom interferometry technique). Spring-mass or vibrating-string relative gravity meters have been used on moving vehicles, including ships, submarines, and aircraft. Gravity measurements from ships became useful in the 1960s, but airborne gravity did not become accurate enough until the late 1980s and early 1990s when kinematic GPS allowed aircraft positions and accelerations to be rapidly and precisely determined.

Measurements of gravity on a moving and vibrating platform are of course much more difficult and less accurate than fixed ground-based measurements. For mobile-use measurements, compensation techniques must be used to remove the noise caused by the motion (acceleration) of the system and the noise of the mass of the compensation instrumentation. This generally requires a stable reference that can be obtained using gyros. The accuracy or noise level of the system is a function of the stability of the system and the complexity of the mechanical, electronic, and software-compensation systems. Along-track filtering or smoothing of the measurements removes some of the noise, but at the penalty of not resolving short wavelengths of the gravity field.

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MCTL DATA SHEET 16.2-3. GRAVITY GRADIOMETERS FOR GROUND USE

A gradiometer can be thought of as an assemblage of gravity meters with spatial separation. The difference between readings reflects the rate of change of gravity along the direction in which the meters are separated. Gravity gradiometers for ground (static) use are used for determining verticality for sensor stabilization.


Any gravity gradiometer for ground use that meets any of the following;

1. Capable of operation on a static platform with a noise level of less (better) than 1.0 Etvs squared per radian per second; or

2. Contains militarily critical accelerometers or gyroscopes.





Geologic mapping and resource exploration; cargo detection and weight in motion; oil production enhancement; and tunnel detection.

Affordability Issues Cost is proportional to usage. This is not a high-volume production technology, but a highly specialized sensor system with only a few, but critical, applications.


WA ML 11.a (Note: g); WA Cat 6.A.7.c; MTCR 12.a.3; CCL Cat 6A007.c.

BACKGROUND

A gradiometer can be thought of as an assemblage of gravity meters with some spatial separation. The difference between readings reflects the rate of change of gravity along the direction in which the meters are separated. A single gravity meter alternately placed at two positions on a tower would measure the vertical component of the vertical gravity field. Similar measurements can be achieved for the horizontal gradients of gravity. In 1886, Baron von Etvs announced an instrument in which two weights were suspended from a torsion fiber at unequal heights. Because the weights were separated both vertically and horizontally, they experienced different forces due to both spatial separations. Modern gravity gradiometers have been implemented in various ways, for example: pairs of accelerometers on spinning platters (Bell Aerospace, Lockheed), superconducting sensors (Univ. of MarylandH. J. Paik), and Cold Atom Interferometry (CAIStanford University and AOSense).

The gradients, the second partial derivatives of the gravity potential, W, constitute the elements of Etvs tensor (or gravity gradient tensor). The derivative of g is the gradient of gravity. In its simplest form, a gradiometer is a set of gravimeters separated by a fixed distance, where the gradient is the difference in field values sensed by the gravimeters. The partial spatial derivatives of the gravity vector yield the gravity gradient tensor, which consists of nine elements. The gravity vector has three spatial components (x, y, and z), and derivatives are taken with respect to each of the spatial directions (x, y, and z) to yield the nine components of the tensor. The gravity gradient tensor (T) is symmetric about its diagonal, so only six of the nine terms (Txx, Tyy, Tzz, Txy, Txz, Tyz) have to be specified. The more costly static gradiometer is used in lieu of a gravity meter because of its greater resolution, ability to measure multiple gravity vector components (Txx, Tyy, Tzz, Txy, Txz, Tyz), and better signal-to-noise ratio (at relatively short spatial wavelengths). Some gradiometer instruments measure the full gradient tensor, while others sense only an individual component or linear combinations of a few components.

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MCTL DATA SHEET 16.2-4. GRAVITY GRADIOMETERS FOR MOBILE USE

Mobile gradiometers are gradiometers that measure acceleration, velocity, and verticality compensation on a moving platform for sensor stabilization.


Any gravity gradiometer for mobile use that meets any of the following:

1. Capable of operation on a moving platform with a noise level of less (better) than 300 Etvs squared per radian per second; or

2. Contains militarily critical accelerometers or gyroscopes.





Geologic mapping and resource exploration. Mass detection, cargo detection, tunnel detection, and weigh in motion.

Affordability Issues This is a highly specialized sensor system, produced in low volume, and as a result, expensive. The size of the market does not justify modification of the technology to reduce cost. If low-cost accelerometer accuracy can be dramatically improved, the military utility of gravity gradiometer arrays will increase.


WA ML 11.a (Note: g); WA Cat 6.A.7.c; MTCR 12.a.3; CCL Cat 6A007.c.

BACKGROUND

A gradiometer can be thought of as an assemblage of gravity meters with some spatial separation. The difference between readings reflects the rate of change of gravity along the direction in which the meters are separated. In order to make mobile measurements of gravity gradients, specialized gradiometers had to be developed. The first mobile measurements using a gravity gradiometer were made by the U.S. Air Force GGSS system[1] in the 1980s.

The gradients, the second partial derivatives of the gravity potential W , constitute the elements of Etvs tensor (or gravity gradient tensor). The derivative of g is the gradient of gravity. The partial spatial derivatives of the gravity vector yield the gravity gradient tensor consisting of nine elements. The gravity vector has three spatial components (x, y, and z) and derivatives are taken with respect to each of the spatial directions (x, y, and z) to yield the nine components of the tensor. The gravity gradient tensor (T) is symmetric about its diagonal, so only six of the nine terms (Txx, Tyy, Tzz, Txy, Txz, Tyz) have to be specified. Some gradiometer instruments measure the full gradient tensor, while others sense only an individual component or linear combinations of a few components.

For moving-base measurements, compensation techniques must be used to remove the systematic errors caused by the motion (acceleration) of the system and the mass of the compensation instrumentation. This generally requires a stable reference that can be obtained using gyros. The accuracy or noise level of the system is a function of the stability of the system and the complexity of the mechanical, electronic, and software-compensation systems.

1. Jekeli, C., 1988, The Gravity Gradiometer Survey System (GGSS), EOS, 69, 105, pp. 116117.

16.3 RADIO, ACOUSTIC AND DATA-BASED REFERENCED NAVIGATION (DBRN) SYSTEMS

Highlights

GNSS commercial and military growth and dependence on GNSS for position and precise time will increase as GNSS receivers decrease in cost, weight, and power.

Improved GPS anti-jam techniques will provide capability to protect against local jamming. Underwater sonar navigation systems and passive acoustic positioning systems are a

significant military concern as they provide an alternative to GNSS. Underwater DBRN systems (bathymetric, magnetic and gravity) can provide a port-to-port

capability for manned and unmanned submersibles, particularly when integrated with an INS. LPI/LPD radar altimeters and fathometers provide near covert capability for DBRN

navigation systems for tactical use.

OVERVIEW

Data-Based Referenced Navigation (DBRN) Systems are systems which use various sources of previously measured geo-mapping data integrated to provide accurate navigation information under dynamic conditions. Data sources include bathymetric maps, stellar maps, gravity maps, magnetic maps or 3-D digital terrain maps. This section of PNT covers a limited category of militarily critical GNSS receivers, underwater acoustic positioning and navigation systems and DBRN technologies having a wide range of dual-use applications.

BACKGROUND

GPS is the current worldwide standard for Positioning, Navigation, and Time (PNT) dissemination. Included in this section are those limited technologies that would provide a significant capability for potential adversaries against the U.S. forces and its allies.

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LIST OF MCTL TECHNOLOGY DATA SHEETS 16.3 RADIO, ACOUSTIC AND DATA-BASED REFERENCED NAVIGATION

(DBRN) SYSTEMS

Radio Navigation Systems

16.3-1 Global Navigation Satellite System Receivers (Including GPS Receiver on a Chip)

Acoustic Navigation Systems

16.3-2 Underwater Doppler (Radar and Sonar) Navigation Systems

16.3-3 Underwater Passive Acoustic Positioning Systems

Data-Based Referenced Navigation

16.3-4 Underwater Data-Based Referenced Navigation (DBRN) Technology

16.3-5 LPI/LPD Radar Altimeters and Fathometers

CHANGES FROM LAST MCTL

Additions: None

Deletions: None

Changes: None

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MCTL DATA SHEET 16.3-1. GLOBAL NAVIGATION SATELLITE SYSTEM RECEIVERS (INCLUDING GPS RECEIVER ON A CHIP)

Satellite-based radio navigation receiving equipment.


Any GNSS receiver equipment that has the following characteristics:

Employing decryption; Designed to provide adaptive interference suppression prior to correlation

processing; Designed to provide navigation information at speeds in excess of 600 m/s

(1,165 miles/hour); or Electronic counter-countermeasures (ECCM) or interference resistance

receivers.

Note 1: The following definitions apply to (b) above:

1. Adaptive interference suppression is mitigation of the interference signal by use of signal filtering or signal processing adjustments, based on an interference signals power spectrum, spatial correlation, or amplitude characteristics.

2. Correlation processing is the receiver functions to perform dispreading or bandwidth collapsing of the satellite spread spectrum signal.

Note 2: The anti-jam parameter does not include automatic gain control (AGC) used as a basic receiver process in many commercial GPS receivers, if employing only this capability in the receiver.

Critical Materials Tamper-resistant thermal-spray technology to protect components containing sensitive U.S. cryptographic logic.

Unique Test, Production, Inspection Equipment

Systems that simulate or generate the specialized radio frequency signal and data message structure and require the use of U.S. cryptography. Equipment that generates an antispoofing signal with less (better) than 28 ns measurement capability.

Unique Software Algorithms that contain U.S. cryptographic logic and other signal-protection and signal-prevention techniques. Controls for input/output ports that transfer classified national-security information.


Ground-vehicle navigation, aircraft navigation, space-vehicle navigation, and surveying. DoD controls access to corrected U.S. GPS pseudorange, delta range, and ephemeris data.

Affordability Issues Accuracy and autonomy are the key drivers. Reduced processor costs and memory will significantly reduce costs.


WA ML 11.a (Note: g); WA Cat 7.A.3.b; MTCR 11.A.3; USML XV(c); CCL Cat 7A003.b and 7A105.

BACKGROUND

GNSS are satellite-based radio navigation systems that enable an unlimited number of users to do all-weather 3-D positioning, velocity measuring, and timing anywhere in the world or near-Earth space. Currently, the only two GNSS are the U.S. GPS and Russias GLONASS. For more information on GLONASS refer to http://www.spacetoday.org/Satellites/GLONASS.html.

A new U.S. space-based positioning, navigation, and timing policy was authorized by President Bush on 8 December 2004. http://pnt.gov/policy/

For more on information on GNSS refer to Section 19, Space Systems Technology.

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MCTL DATA SHEET 16.3-2. UNDERWATER DOPPLER (RADAR AND SONAR) NAVIGATION SYSTEMS

Underwater radar or sonar navigation system using Doppler velocity or correlation velocity logs integrated with a heading source.


Any Underwater sonar navigation system, using Doppler velocity or correlation velocity logs integrated with a heading source, having the following characteristic:

1. Having a positioning accuracy of equal to or less (better) than 3% of distance traveled CEP.

(See Data Sheet 16.3-5, for component to such systems.) Critical Materials None identified. Unique Test, Production, Inspection Equipment

None identified.

Unique Software Software or source code to improve performance to achieve the militarily critical parameter, or integrated with INS, GNSS or DBRN systems.


None identified for LPI/LPD technology, but basic Doppler navigation systems have wide applications in commercial aviation, space, land, and sea vehicles, including weather tracking.

Affordability Issues Military-unique LPI software requirement may drive up cost, unless hardware maximizes commercial technology.


WA ML 11.a (Note: g); WA Cat 7.A.8; USML XV(c); CCL Cat 8A002.b.

BACKGROUND

Doppler (radar or sonar) navigation is dead reckoning in that it tracks changes in position from a known starting point. The Doppler velocity sensor determines velocity and drift angle by measuring the Doppler frequency shift (Doppler effect) from narrow radar or sonar beams transmitted at oblique angles from the vehicle toward the ground.

A Sonar Navigation System can be either a Sonar Doppler Velocity Navigation System (DVNS) or a Sonar Correlation Velocity Navigation System (CVNS). Both systems consist of two components: a velocity source and a heading source.

1. A Sonar Doppler Velocity Navigation System (SDVNS) consists of a Doppler Velocity (DV) source and a heading source. Velocity is derived from a Doppler velocity sonar array capable of either locking onto a particular matter in the water column, as with an Acoustic Doppler Current Profiler (ADCP), or using Bottom Lock Doppler Sonar to track the ocean bottom. The former would give ships speed through water similar to the EM Log, while the latter would give speed over ground. Knowledge of the ships velocity is part of the navigation solution. Velocities are derived relative to the ship. To be translated to the geographic reference frame, the ships orientation in the geographic reference frame must be known, i.e., heading. Heading can be derived from a magnetic fluxgate compass or an inertial source such as a gyrocompass, an inertial measurement unit (IMU) or a full INS. Knowing velocity, direction and time traveled, the change in position can be computed.

2. A Sonar Correlation Velocity Navigation System (SCVNS) consists of a Correlation Velocity (CV) source (related to a Pitometer) and a heading source. The CV sensor offers accurate velocity relative to the seabed, at low speeds, making it attractive for use in AUVs. The CV is similar to the DV in that it uses sonar echoes from the seabed but it is different in operation. Two pulses are emitted in close succession and the echoes from the seabed are measured and compared by the

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receiver array. The movement of the pattern of sonar returns, with respect to the receiver, is used to calculate the velocity. Distance traveled (and direction relative to the axis of the ship) is computed by distance from the reference on the first pulse and the receiver with the highest correlation of the signal. Time between pulses is known. With time and distance, velocity is computed. The SCVNS then integrates the CV sensor and heading sensor, basically similar to the SDVNS.

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MCTL DATA SHEET 16.3-3. UNDERWATER PASSIVE ACOUSTIC POSITIONING SYSTEMS

Passive underwater acoustic positioning system that provides a surface ship or submarine (manned or unmanned) with a relative position that was achieved with transducers on the vessel (acoustic listening devices) and a network of acoustic transponders (transmitters) external to the vessel that provides coordinates of an acoustic grid.


Any non-active acoustic positioning system that determines the position of surface or underwater vehicles having an accuracy less than 10 m (CEP) at ranges greater than 1,000 m.


None identified.

Unique Software Software or source code to improve performance to achieve militarily critical parameter, or integrated with INS, GNSS or DBRN systems.


Ship docking and navigation.


WA ML 11.a (Note: g); WA Cat 7.A.8; USML XV(c); CCL Cat 8A002.b.

BACKGROUND

This technology can provide an underwater passive acoustic navigation system similar to GPS, by pre-surveying the geodetic location of each transponder and either being deployed (1) as an active GPS buoy on the surface of the water and pinging signals underwater, or (2) anchored to the seabed (see Figure 16.3-1.)

Figure 16.3-1. Underwater Navigation Using Acoustic Transponders Anchored to Seafloor

(Source: http://www.divediscover.whoi.edu/tools/sonar.html and http://www.divediscover.whoi.edu/tools/navigation.html)

The fundamental concept of passive acoustics navigation is basically the same as satellite navigation. Both are based in Cartesian navigation. In place of satellites, transducers or pingers transmit acoustic signals at different frequencies. These transponders are placed in a known array pattern and can either (1)

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be continuously active, or (2) remain passive until queried by a vessel. The latter requires the vessel to actively transmit. Most commercial surface vessels currently use this type. The receiver is a microphone interrogator that transmits an acoustic signal and measures the time to receive a reply. The time difference is a function of distance from the transponder. More than one transponder is required to establish a position fix. Better performance can be obtained by increasing the number of transponders. There are two common types of acoustic navigation: (1) short or ultra-short baseline; and (2) long-baseline.

For additional information go to: http://dspace.mit.edu/handle/1721.1/36835

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MCTL DATA SHEET 16.3-4. UNDERWATER DATA-BASED REFERENCED NAVIGATION (DBRN) TECHNOLOGY

Underwater navigation system using acoustic, magnetic or gravity sensors with an a priori data source or maps.


Any DBRN technology designed to navigate underwater using bathymetric, magnetic, or gravity databases that provide a positioning accuracy equal to or less (better) than 0.4 nmi.


None identified.

Unique Software Software or source code which improves the operational performance or reduces the navigational error of systems specified as militarily critical by continuously combining heading data with DBRN systems.


Ship navigation, underwater-vehicle navigation, mining, farming, and surveying.

Affordability Issues Mapping data source, worldwide coverage, and accuracy are the key cost drivers. Export Control References

WA ML 11.a (Note: g); WA Cat 7.A.3.b, 7.D.3.b.3 and 7.E.4.a.7; USML XV(c); CCL Cat 7A003.b and 7D003.b.

BACKGROUND

Underwater Data-Based Referenced Navigation (DBRN) Systems[1] when combined with a priori data sources or maps provide a means of obtaining position and direction when the platform is moving (refer to Figure 16.3-2). There are three types of underwater DBRN Systems.

1. A bathymetric-acoustic DBRN system uses an acoustic sensor (active or passive), laser or Fathometer and a pressure sensor for underwater vehicles to determine overall depth to the seabed. This system compares the along track position information (swath profile data) using low probability of intercept techniques with the pre-stored database.

2. A magnetic DBRN system uses a magnetometer, or preferably, a magnetic gradiometer (refer to Section 16.4) to sense the crustal magnetic signature. As the platform moves, the magnetic profile is correlated with the pre-stored database. Only after movement of the platform over magnetic profile differences (contours) and compiling the profile data can a correlation be made with the pre-stored database to determine the platforms position. Continuous determination of position over time will provide direction from which, with time, will provide navigation information, such as velocity and distance traveled. Areas where the crustal magnetic field has large spatial variability are where this type system operates best.

3. A gravity DBRN system uses a gravimeter sensor (refer to Section 16.2) to read the gravity value, or compute the gravity value from other sensors, i.e., subtracting acceleration data from inertial navigation systems from acceleration from GPS data. As the platform moves, the gravity profile [(milligals), latitude, and longitude] is correlated with the pre-stored database to determine the platforms position. Continuous determination of position over time will provide direction from which, with time, will provide other navigation information, such as velocity and distance traveled.

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Figure 16.3-2. Conceptual Description of a DBRN System (Source: ARL, Penn State)

In general, DBRN systems use pre-stored or calculated ground and undersea terrain-contour, acoustic, electromagnetic spectrum, magnetic, gravity, and stellar sensor data. DBRN technology is partially derived from sensor and Geospatial information and services (GI&S) data. Although GI&S data by itself is not necessarily militarily critical, the combination of GI&S data from multiple sources (bathymetric, magnetic, and gravity) leveraged by high-speed computers and retrieval databases provides an autonomous, covert, and nonjammable positioning and navigation capability that is militarily critical. With the availability of lower cost inertial reference systems, the Doppler SONAR (refer to Data Sheet 16.3-2), or laser altimeter or fathometer (refer to Data Sheet 16.3-5) sensor can provide very accurate INS/DBRN system (refer to Data Sheet 16.1-2) to operate with less detectable noise (low probability of detection) and have better positional accuracy.

1. The Wassenaar Regime defines Data-Based Referenced Navigation (DBRN) Systems as systems, which use various sources of previously measured geo-mapping data integrated to provide accurate navigation information under dynamic conditions. Data sources include bathymetric maps, star catalog or almanac, gravity maps, magnetic maps or 3-D digital terrain maps.

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MCTL DATA SHEET 16.3-5. LPI/LPD RADAR ALTIMETERS AND FATHOMETERS

LPI/LPD radar altimeters and fathometers use power management and phase-shift-key modulation to reduce the emitted power of the radar altimeter (or fathometer), resulting in a decreased detectability and covert operation, while providing critical-height-above-terrain information.


Any radar altimeter or fathometer (also called a depth finder) having the following characteristics:

1. Power management or use of phase-shift-key modulation techniques; or 2. Any technique that reduces signal detectability, including antenna steering or

beaming technology.


None identified.

Unique Software Algorithms and source codes that reduce signal detectability, including antenna cross-correlation algorithms and verified data.


None identified for LPI/LPD technology, but basic radar altimeter and fathometer systems have wide applications in commercial aviation, space, land, and marine vehicles.

Affordability Issues Military-unique LPI software requirement may drive up cost, unless hardware maximizes commercial technology.


WA Cat 7.A.6 and 8.A.2.b; MTCR 11.A.1; USML XV(c); CCL Cat 7A006 and 8A002.b.

BACKGROUND

Radar altimeters provide height-above-terrain, while fathometers provide distance above ocean bottom terrain.

The use of low probability of intercept (LPI) or low probability of detection (LPD) techniques reduces the emitting power of these devices.

16.4 MAGNETIC AND ELECTROMAGNETIC SENSOR SYSTEMS

Highlights

Magnetic and electromagnetic sensor technology varies greatly with type, application, and cost.

Magnetic and electromagnetic sensor systems and arrays provide a covert detection and classification technology.

More use of low-cost, thin-film magnetic resonance (MR) sensors is expected for a number of applications for which cost, size, and power are driving factors, such as mine detection and area security.

Newly developed potassium and helium-4 (He-4) optically pumped magnetometers are demonstrating performance comparable to SQUID magnetometers at lower cost and without the logistic complication of maintaining superconductive temperatures in a battlespace environment.

Biomedical research and diagnostics and nondestructive evaluations are major military funding sources for future usage of SQUID sensors.

Magnetic gradiometers, utilizing either the SQUID or potassium technologies, nearly eliminate the natural geomagnetic background noise.

High superconducting temperature (Tc) SQUID technology has matured since its inception in 1987 to the point where nitrogen-cooled superconducting sensors are rivaling their low-Tc counterparts.

Underwater electric field sensors are evolving with the advent of the potassium magnetometer, which detects changes in the electric dipole potential (EDP) magnetic field. This provides another method of detecting underwater objects.

OVERVIEW

This section of PNT covers the technologies relative to magnetic and electromagnetic sensors. Magnetic sensor systems detect and display the presence of a magnetic field and measure its magnitude, or direction, or both. Every object has a distinct magnetic signature that is reflected or emitted from the object. The common problem in magnetometry is how to detect and classify the signature or, in other words, how to get the signal out of the noise. This unique and enabling technology can be used to detect and locate an adversary, detect magnetic heading, or determine own position from a database reference. Magnetic sensor types of special interest include SQUIDs, nuclear precession, optically or laser pumped, flux gate, fiber optic, MR, and

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