Missile Defense Agency

In the course of 71 days in lunar orbit, from 19 February to 3 May 1994, the Clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths. These data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side. In addition, laser-ranging measurements provided the first view of the global topographic figure of the moon. The topography of many ancient impact basins has been measured, and a global map of the thickness of the lunar crust has been derived from the topography and gravity.

In this work, the stress-point approach, which was developed to address tension instability and improve accuracy in Smoothed Particle Hydrodynamics (SPH) methods, is further extended and applied for one-dimensional (1-D) problems. Details of the implementation of the stress-point method are also given. A stability analysis reveals a reduction in the critical time step by a factor of 1/√2 when the stress points are located at the extremes of the SPH particle. An elementary damage law is also introduced into the 1-D formulation. Application to a 1-D impact problem indicates far less oscillation in the pressure at the interface for coarse meshes than with the standard SPH formulation. Damage predictions and backface velocity histories for a bar appear to be quite reasonable as well. In general, applications to elastic and inelastic 1-D problems are very encouraging. The stress-point approach produces stable and accurate results. © 1997 by John Wiley & Sons, Ltd.

The Global Positioning System (GPS) carrier beat phase data collected by the TI4100 GPS receiver has been successfully utilized by the US Defense Mapping Agency in an algorithm which is designed to estimate individual absolute geodetic point positions from data collected over a few hours. The algorithm uses differenced data from one station and two to four GPS satellites at a series of epochs separated by 30 second intervals. The ‘precise’ GPS ephemerides and satellite clock states, held fixed in the estimation process, are those estimated by the Naval Surface Warfare Center (NSWC). Broadcast ephemerides and clock states are also utilized for comparative purposes. An outline of the data corrections applied, the mathematical model and the estimation algorithm are presented. Point positioning results and statistics are presented for a globally‐distributed set of stations which contributed to the CASA UNO experiment. Statistical assessment of 114 GPS point positions at 11 CASA UNO stations indicates that the overall standard deviation of a point position component, estimated from a few hours of data, is 73 centimeters. Solution of the long line geodetic inverse problem using repeated point positions such as these can potentially offer a new tool for those studying geodynamics on a global scale.

The popularity of using synoptic climatological approaches to evaluate environmental problems has undergone a recent resurgence, and several objective procedures have been developed. The purpose of this study is to propose an objective methodology to characterize air masses at a given locale and to show that a holistic synoptic approach may provide better results than traditional statistical approaches in evaluating the impact of climate on sulfur dioxide concentrations. The relationships between individual weather variables and sulfur dioxide were weak when they were examined via stepwise multiple regression. The synoptic methodology, using principal components analysis and a clustering procedure, proved more informative. We were able to identify air mass categories exhibiting particularly high sulfur dioxide concentrations and synoptic scenarios of long duration contributing to severe concentration levels. Additionally, those air mass categories most strongly associated with low-level, pollution-inducing inversions were noted. The synoptic procedure should prove helpful in determining if long-term trends in concentration can be attributed to weather conditions or to changes in emissions.

Densification of tantalum carbide (TaC) was studied by hot pressing at temperatures ranging from 1900° to 2400°C with and without sintering additives. Without sintering additives, the relative density increased from 75% at 1900°C to 96% at 2400°C. A microstructural examination showed no observable grain growth up to 2300°C. Densification was enhanced with carbon (C) and/or B 4 C additions. TaC with a 0.78 wt% C addition achieved a relative density of 97% at 2300°C. Additions of 0.36 wt% B 4 C or 0.43 wt% B 4 C and 0.13 wt% C increased the relative density to 98% at 2200°C, accompanied by rapid grain growth at 2100°C and higher temperatures.

This paper presents the results from a laboratory study in which hot-mix asphalt (HMA) mixtures with No. 4 sieve screened reclaimed asphalt pavement (RAP) were characterized for their cracking resistance through laboratory performance testing. A typical surface mixture commonly used in the state of Tennessee was evaluated at 0, 10, 20, and 30% RAP contents. Two types of aggregate (limestone and gravel) and three types of asphalt binders (PG 64-22, PG 70-22, and PG 76-22) were used in this study. Mixture cracking resistance was evaluated through Superpave indirect tension (IDT), beam fatigue, and semicircular bending (SCB) tests. The results from this study indicated that the inclusion of RAP generally increased stiffness and indirect tensile strength; however, it generally compromised cracking resistance for the mixtures studied. Mixture properties changed significantly at 30% RAP content as compared to those with 10 and 20% RAP. Field projects validated the findings from the laboratory study.

An improved world geodetic system has been developed to satisfy the mapping, charting, and geodetic needs of the Department of Defense. The system, designated WGS 72, represents the culmination of approximately five years of data collection within the Department of Defense and the scientific community. Principal agencies involved in the developmental cycle include the USAF, Defense Mapping Agency, US Naval Weapons Laboratory, and Naval Oceanographic Office. The method of solution for an adjustment of this magnitude is characterized by the formation of a large-scale matrix by combining normal matrices from each of the major data input sets. The scaling and weighting processes for the final matrix are discussed. The resultant ellipsoid parameters, datum shifts and their related accuracies are presented and compared against similar quantities in other recent geocentric systems.

Modern UAV’s reduce the threat to human operators, but do not decrease the manpower requirements. Each aircraft requires a flight crew of one to three, so deploying large numbers of UAV’s requires committing and coordinating many human warfighters. Insects perform impressive feats of coordination without direct inter-agent coordination, by sensing and depositing pheromones (chemical scent markers) in the environment [14]. We have developed a novel technology for coordinating the movements of multiple UAV’s based on a computational analog of pheromone dynamics. The control logic is simple enough that it can be executed autonomously by a UAV, enabling a single human to monitor an entire swarm of UAV’s. This paper describes the technology, its application to UAV coordination, and the results we have obtained.

We report high performance uncooled midwavelength infrared photodiodes based on interface-engineered InAs∕GaSb superlattice. Two distinct superlattices were designed with a cutoff wavelength around 5μm for room temperature and 77 K. The device quantum efficiency reached more than 25% with responsivity around 1A∕W. Detectivity was measured around 109cmHz1∕2∕W at room temperature and 1.5×1013cmHz1∕2∕W at 77 K under zero bias. The devices were without antireflective coating. The device quantum efficiency stays at nearly the same level within this temperature range. Additionally, Wannier–Stark oscillations in the Zener tunneling current were observed up to room temperature.

This paper contains a discussion of the Software Development System (SDS), a methodology addressing the problems involved in the development of software for ballistic missile defense systems. These are large real-time, automated systems with a requirement for high reliability. The SDS is a broad approach attacking problems arising in requirements generation, software design, coding, and testing. The approach is highly requirements oriented and has resulted in the formulation of structuring concepts, a requirements statement language, process design language, and support software to be used throughout the development cycle. This methodology represents a significant advance in software technology for the development of software for a class of systems such as BMD. The support software has been implemented and is undergoing evaluation.

Free-space laser communication (lasercom) systems are subject to performance degradation when heavy fog or smoke obscures the line of sight. The bit-error rate (BER) of a high-bandwidth (570 Mbits/s) lasercom system was correlated with the atmospheric transmission over a folded path of 2.4 km. BER's of 10(-7) were observed when the atmospheric transmission was as low as 0.25%, whereas BER's of less than 10(-10) were observed when the transmission was above 2.5%. System performance was approximately 10 dB less than calculated, with the discrepancy attributed to scintillation, multiple scattering, and absorption. Peak power of the 810-nm communications laser was 186 mW, and the beam divergence was purposely degraded to 830 murad. These results were achieved without the use of error correction schemes or active tracking. An optimized system with narrower beam divergence and active tracking could be expected to yield significantly better performance.

We report on the surface passivation of Type-II InAs/GaSb superlattice photodetectors using various ammonium sulfide solutions. Compared to unpassivated detectors, zero-bias resistance of treated 400 μm×400 μm devices with 8 μm cutoff wavelength was improved by over an order of magnitude to ∼20 kΩ at 80 K. Reverse-bias dark current density was reduced by approximately two orders of magnitude to less than 10 mA/cm2 at −2 V. Dark current modeling, which takes into account trap-assisted tunneling, indicates greater than 70 times reduction in bulk trap density for passivated detectors.

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024 × 1024 pixel quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NEΔ T ) of 17 mK at a 95 K operating temperature with f /2.5 optics at 300 K background and the LWIR detector array has demonstrated a NEΔ T of 13 mK at a 70 K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90 K and 70 K operating temperatures respectively, with similar optical and background conditions. In this paper, we will discuss the performance in terms of quantum efficiency, NEΔ T , uniformity, operability and modulation transfer functions.

Silicon-on-insulator (SOI) integrated circuits have been demonstrated for use at temperatures up to 300°C. However, to build functional electronics, multiple devices must be interconnected to provide the desired functionality. A system-in-package approach has been developed using thick-film technology on Si3N4ceramic substrates. Si3N4has a near coefficient-of-thermal-expansion match to Si and a higher flexural modulus than Al2O3, which is commonly used for thick-film applications. The conductor metallization is Au. For 300°C operation, eutectic Au-Ge die attach was used with a Ti/Ti:W/Au backside die metallization. After 3000 h at 325 °C, the mean die shear strength decreased from 3.96 to 3.33 kg/mm2, a decrease of only 16%. Formation of Au-Si-Ge ternary eutectic (melting point 326 °C) was observed and limits the use of Au-Ge die attach to 300 °C. SOI dies typically have Al wire bond pads that are not compatible with Au thermosonic wire bonding for high-temperature applications. Two plating processes have been examined: electroless Ni/immersion Au/electroless Au and electroless Ni/electroless Pd/immersion Au. The plating processes provide a barrier layer (Ni) and a wire-bondable finish (Au or Pd-Au) over the Al wire bond pads. After 10 000 h at 300 °C, the wire pull force for the Ni/Au samples decreased by ~30% due to annealing of the Au wire, while the ball shear force increased by ~35%. The daisy-chain electrical resistance remained relatively constant. For the Ni-Pd-Au samples, after 2000 h at 320 °C, the ball shear force remained constant or increased slightly, the wire pull force decreased by ~25% due to annealing of the Au wire, and the daisy-chain resistance remained relatively constant. After 3000 h, however, cratering of the Si wire bond pad was observed corresponding to some first bond pad lifts and increased daisy-chain resistance. Optimization of the wire-bonding parameters for bonding to the harder Ni/Pd/Au bond pad is required to eliminate cratering.

We have used average continental elevations for 1‐degree‐square areas to construct detailed continental hypsographic curves. The curves available up to the present have been those prepared by Kossinna, but they suffer from some drawbacks, the most important being that the elevation interval is for the most part 1 km, which does not allow for very detailed work. Consequently, we have given data for each 0.1 km interval of elevation. The availability of the data on tapes allowed us also to make calculations of the average elevation of each continent, an important normalizing parameter when comparing continental hypsographic curves, and to add on the effects of the continental shelves. It has also allowed us to recalculate the amount of continent antipodal to continent and to produce a map of the world showing these areas. We have also used the detailed curves and the amounts of continental flooding during the Neozoic to derive records of sea level variation necessary to explain the amount of flooding for each continent through time.

We report a high detectivity middle-wavelength infrared quantum dot infrared photodetector (QDIP). The InGaAs quantum dots were grown by self-assembly on an InGaP matrix via low pressure metalorganic chemical vapor deposition. Photoresponse was observed at temperatures above 200 K with a peak wavelength of 4.7 μm and cutoff wavelength of 5.2 μm. The background limited performance temperature was 140 K, and this was attributed to the super low dark current observed in this QDIP. A detectivity of 3.6×1010 cm Hz1/2/W, which is comparable to the state-of-the-art quantum well infrared photodetectors in a similar wavelength range, was obtained for this InGaAs/InGaP QDIP at both T=77 K and T=95 K at biases of −1.6 and −1.4 V, respectively.

We report a demonstration of an infrared focal plane array based on InGaAs/InGaP quantum dot infrared photodetectors. The middle-wavelength infrared quantum-dot infrared photodetector (QDIP) structure was grown via low-pressure metal organic chemical vapor deposition. A detectivity of 3.6×1010 cm Hz1/2/W was achieved at T=95 K and a bias of −1.4 V. The background limited temperature of our QDIP was 140 K with a 45° field of view. A 256×256 detector array was fabricated with dry etching, and hybridized to a Litton readout chip by indium bumps. Thermal imaging was achieved at temperatures up to 120 K. At T=77 K, the noise equivalent temperature difference was measured as 0.509 K with a 300 K background and f/2.3 optics.

The Defense Mapping Agency (DMA) has developed a digital data file at a nominal scale of 1:250,000, containing shorelines, international boundaries and country names and known as the World Vector Shoreline (WVS). The file was developed with these features in support of geographic information systems, command, control and communications systems. The WVS has been designed to fit varying applications and is convertible to other system specific formats.

The first flight of the HiSentinel80, an unmanned high altitude airship, completed a successful test Nov. 10, 2010; launching from Page, Arizona, and tracked northeast toward Utah and Colorado. The payload, part of a U.S. Army Space and Missile Defense Command/Army Forces Strategic Command program, was recovered north of Monticello, Utah, on Nov. 11. The purpose of the test flight was to obtain performance data on the high altitude airship, as well as test various payload capabilities. The objective of the test was to demonstrate engineering feasibility and potential military utility of high altitude systems for persistent payload operations. The HiSentinel80 was aloft for eight hours at an altitude of 66,300 feet collecting valuable command and control and payload connectivity data before flight termination. The Prime Contractor for the HiSentinel effort is Southwest Research Institute (SwRI) and the sub-contractor is Aerostar International, Inc. The team of SwRI and Aerostar launched and recovered the airship. SwRI designed the airship and provided the telemetry, flight control, power, and propulsion systems. Aerostar fabricated the hull and supported in the integration and test flight. The SwRI/Aerostar Team developed the launch system, provided facilities, and launched and recovered the airship. The HiSentinel system is capable of lifting small to medium payloads (20–200 pounds) to high altitudes (>60,000 feet) for a duration of 30 days or greater. HiSentinel80 is 207 feet long and 45 feet in diameter and is designed to cruise at an altitude of 65,000 feet, well above commercial airspace. The HiSentinel80 airship is designed to launch similar to a weather balloon, taking the familiar airship shape as the vehicle reaches its mission altitude. At mission completion, the payload is released from the hull and returns to the ground by parachute and can be refurbished. The hull, or vehicle body, is made of low-cost disposable material designed not to be recovered after a mission. For the purpose of this flight demonstration, the airship hull was recovered for inspection south of Grand Junction, Colorado. This paper will include a technical overview of the HiSentinel80 airship development. An overview of results from the HiSentinel80 flight will be presented.

The Defense Mapping Agency (DMA) has developed World Geodetic System (WGS) 1984, and starting from its earlier versions, viz., WGS 60, WGS 66, and WGS 72, the latest system is a state‐of‐the‐art, accurately defined, global reference frame. In its development, full advantage was derived from the advancement in theory, recent sophistication in computer technology, and the availability of new and more extensive data sets. The new system represents DMA's modeling of the earth from a geometric, geodetic, and gravitational standpoint, using data, techniques, and technology available through early 1984. This paper presents details about the WGS 84 defining parameters, reference frame definition, gravitational model, gravity formula, and its relationship with various local/regional geodetic datums. It also briefly outlines various advantages and applications to improve Mapping, Charting, and Geodetic (MC&G) products globally.