Bookmarks

Recent Publications, Papers, and Patents by the Aerospace Technical Staff

Publications and Papers

(Dec. 2006–July 2007)

R. L. Bishop and P. R. Straus, "Characterizing Ionospheric Variations in the Vicinity of Hurricanes and Typhoons Using GPS Occultation Measurements," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SA33B-0276.

B. B. Brady, "Transient Fluid Flow in Short-Pulse Operation of Bipropellant Thrusters," Journal of Propulsion and Power, Vol. 23, No. 2, pp. 398–403 (Mar./Apr. 2007).

J. C. Camparo, "Lamp Stabilization Using Ion Waves: Smart-Clock Technology to Eliminate Light-Shift Variations," Proceedings of the 2006 IEEE International Frequency Control Symposium and Exposition, p. 5 (Miami, FL, June 4–7, 2006).

J. C. Camparo and R. Mackay, "Spectral Mode Changes in an Alkali RF Discharge," Journal of Applied Physics, Vol. 101, No. 5, pp. 53303.1–53303.6 (Mar. 1, 2007).

M. W. Chen, C. Wang, M. Schulz, and L. R. Lyons, "Solar Wind Influence on MLT Dependence of Plasmasheet Conditions and Implications for Ring Current Modeling," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SM33D-05.

T. K. Cheung, B. A. Blake, and T. T. Lam, "Heating of Finite Slabs Subjected to Laser Pulse Irradiation and Convective Cooling," Journal of Thermophysics and Heat Transfer, Vol. 21, No. 2, pp. 323–329 (Apr.–June 2007).

J. H. Clemmons, D. R. Salem, R. L. Bishop, and A. B. Christensen, "Measurements in the Thermosphere: First Results from the Ionization Gauge on the Streak Mission," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SA11A-06.

J. A. Conway, S. Sahni, and T. Szkopek, "Plasmonic Interconnects versus Conventional Interconnects: A Comparison of Latency, Cross-Talk, and Energy Costs," Optics Express, Vol. 15, No. 8, pp. 4474–4484 (Apr. 16, 2007).

J. D. Desain, L. Valachovic, L. E. Jusinski, and C. A. Taatjes, "Reaction of Chlorine Atom with Trichlorosilane from 296 to 473 K," Journal of Chemical Physics, Vol. 125, No. 22, pp. 224308.1–224308.8 (Dec. 14, 2006).

K. D. Diamant, B. L. Zeigler, and R. B. Cohen, "Microwave Electrothermal Thruster Performance," Journal of Propulsion and Power, Vol. 23, No. 1, pp. 27–34 (Jan./Feb. 2007).

K. W. Dotson and B. H. Sako, "Interaction between Solid Rocket Motor Internal Flow and Structure During Flight," Journal of Propulsion and Power, Vol. 23, No. 1, pp. 140–145 (Jan./Feb. 2007).

J. F. Fennell, J. L. Roeder, and R. H. Friedel, "Stormtime Electron PSD Radial Profiles for Small and Large K Values: SCATHA Observations," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SM41C-05.

M. P. Ferringer, R. S. Clifton, and T. G. Thompson, "Efficient and Accurate Evolutionary Multi-Objective Optimization Paradigms for Satellite Constellation Design," Journal of Spacecraft and Rockets, Vol. 44, No. 3, pp. 682–691 (May/June 2007).

M. P. Ferringer and D. B. Spencer, "Satellite Constellation Design Tradeoffs Using Multiple-Objective Evolutionary Computation," Journal of Spacecraft and Rockets, Vol. 43, No. 6, pp. 1404–1411 (Nov./Dec. 2006).

L. J. Gelinas, J. H. Hecht, R. G. Roble, and R. L. Walterscheid, "A Seasonal Study of Mesospheric Temperatures and Emission Intensities at Adelaide and Alice Springs," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SA21A-0221.

J. George, R. Koga, G. Swift, G. Allen, C. Carmichael, and C. W. Tseng, "Single Event Upsets in Xilinx Virtex-4 FPGA," 2006 IEEE Radiation Effects Data Workshop, p. 6 (Ponte Vedra, FL, July 17–21, 2006).

M. M. Gorlick, G. S. Peng, S. D. Gasster, and M. D. McAtee, "Flow Webs: Mechanism and Architecture for the Implementation of Sensor Webs," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. IN23A-1216.

T. D. Hain and T. J. Curtiss, "Experimental Validation of Formaldehyde Rotational State Selection," Chemical Physics Letters, Vol. 441, No. 1–3, pp. 25–28 (June 13, 2007).

J. S. Halpine, S. H. Liu, E. J. Simburger, H. Yoo, D. Hinkley, and D. Rumsey, "Pico-Satellite Solar Cell Testbed Qualification Testing," Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, p. 4 (Waikoloa, HI, May 7–12, 2006).

P. Hantos, "Defense Acquisition Performance Assessment—The Life-Cycle Perspective of Selected Recommendations," CrossTalk, Vol. 20, No. 5, pp. 25–29 (May 2007).

J. H. Hecht, R. J. Rudy, R. L. Walterscheid, A. Z. Liu, S. J. Franke, P. Pautet, and M. J. Taylor, "Characteristics of Short-Period Wavelike Features near 90 km Altitude from Airglow and Lidar Observations over Maui," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SA21A-0233.

M. Hecht, K. Owens, and J. Tagami, "Reliability-Related Requirements in Software-Intensive Systems," 2007 Annual Reliability and Maintainability Symposium, p. 6 (Orlando, FL, Jan. 22–25, 2007).

J. K. Holmes, Spread Spectrum Systems for GNSS and Wireless Communications, GNSS Technology, and Applications Series (Artech House, Boston and London, 2007).

J. K. Holmes, N. Morgan, and P. Dafesh, "A Theoretical Approach to Determining the 95% Probability of TTFF for the P(Y) Code Utilizing Active Code Acquisition," 24th AIAA International Communications Satellite Systems Conference and 4th Annual International Satellite and Communications Conference and Expo (San Diego, June 11–14, 2006), AIAA Paper 2006-5321.

M. Huang, J. G. Coffer, and J. C. Camparo, "Rb87 Hyperfine-Transition Dephasing in Mixed Buffer-Gas Systems," Physical Review A: Atomic, Molecular, and Optical Physics, Vol. 75, No. 5, p. 052717 (May 24, 2007).

A. B. Jenkin and R. A. Gick, "Collision Risk Posed to the Global Positioning System by Disposed Upper Stages," Journal of Spacecraft and Rockets, Vol. 43, No. 6, pp. 1412–1418 (Nov./Dec. 2006).

J. A. Kechichian and M. E. Sorge, "The Efficient Analytic Computation of Fractional Reentering Debris from an Idealized Isotropic Explosion in General Elliptic Orbit," Spaceflight Mechanics 2006, Vol. 2, pp. 2161–2182 (Tampa, FL, Jan. 22–26, 2006).

S. Kenderian, R. E. Green Jr., and B. B. Djordjevic, "Ultrasonic Monitoring of Dislocations during Fatigue of Pearlitic Steel," Materials Evaluation, Vol. 65, No. 5, pp. 467–471 (May 2007).

H. I. Kim and J. R. Lince, "Direct Visualization of Sliding-Induced Tribofilm on Au/MoS₂ Nanocomposite Coatings by c-AFM," Tribology Letters, Vol. 26, No. 1, pp. 61–65 (Apr. 2007).

R. Koga, J. George, P. Yu, S. Grain, M. Zakrzewski, and K. Crawford, "Single Event Effects Sensitivity of the Q Series Advanced CMOS Technology," 2006 IEEE Radiation Effects Data Workshop, p. 6 (Ponte Vedra, FL, July 17–21, 2006).

C. Lemon, M. Chen, T. P. O'Brien, F. Toffoletto, S. Sazykin, R. Wolf, and V. Kumar, "The Evolution of the Storm-Time Ring Current in Response to Different Characteristics of the Plasma Source," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SM14B-02.

S. H. Liu, J. E. Granata, J. C. Nocerino, J. S. Halpine, and E. J. Simburger, "Thin-Film Photovoltaic Radiation Testing for Space Applications," Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, p. 3 (Waikoloa, HI, May 7–12, 2006).

S. H. Liu, J. S. Halpine, D. Hinkley, J. R. Srour, and D. Rumsey, "Pico Satellite Solar Cell Testbed (PSSC Testbed)," Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, p. 3 (Waikoloa, HI, May 7–12, 2006).

M. D. Looper, J. B. Blake, and T. L. Mulligan, "A Search for Energetic-Electron Precursors to SEP Ions in SAMPEX Observations," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SH42A-06.

D. C. Marvin, "Final Flight Data Report from ASCOT," Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, p. 4 (Waikoloa, HI, May 7–12, 2006).

J. E. Mazur, G. M. Mason, M. I. Desai, J. R. Dwyer, J. Giacalone, J. R. Jokipii, and E. C. Stone, "The Structure of the Interplanetary Magnetic Field as Revealed by Solar Flare Particles," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SH11B-07.

T. L. Mulligan, J. B. Blake, H. E. Spence, A. P. Jordan, J. J. Quenby, and D. Shaul, "Transient IP Structures Associated with Short-Period Variations in the Solar Energetic Particle and Galactic Cosmic Ray Flux," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SH54A-06.

T. L. Mulligan, B. V. Jackson, and M. Tokumaru, "3-D Magnetic Field Geometry of the October 28, 2003 ICME: Comparison with SMEI White-Light Observations," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SH33A-0397.

M. J. O'Brien, H. F. Von Bremen, M. Furukawa, Z. Horita, and T. G. Langdon, "A Finite Element Analysis of the Superplastic Forming of an Aluminum Alloy Processed by ECAP," Materials Science and Engineering A, Vol. 456, No. 1–2, pp. 236–242 (May 15, 2007).

T. P. O'Brien, "Capturing the Variable Outer-Zone Relativistic Electrons for Spacecraft Designers," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SM42A-05.

D. E. Pansatiankul and V. S. Lin, "End-to-End Communication Systems Modeling Using Hardware-Accelerated Simulation Tool," MILCOM 2006, p. 6 (Washington, DC, Oct. 23–25, 2006).

R. P. Patera, "Collision Probability for Larger Bodies Having Nonlinear Relative Motion," Journal of Guidance, Control, and Dynamics, Vol. 29, No. 6, pp. 1468–1472 (Nov./Dec. 2006).

R. P. Patera, "Space Vehicle Conflict-Avoidance Analysis," Journal of Guidance, Control, and Dynamics, Vol. 30, No. 2, pp. 492–498 (Mar./Apr. 2007).

L. A. Peterson, T. K. Cheung, T. T. Lam, and B. A. Blake, "Exponential Heating of Two-Dimensional Slabs," Collection of Technical Papers: 45th AIAA Aerospace Sciences Meeting, Vol. 4, pp. 2316–2332 (2007).

R. G. Pettit and H. Gomaa, "Analyzing Behavior of Concurrent Software Designs for Embedded Systems,"10th IEEE International Symposium on Object and Component-Oriented Real-Time Distributed Computing, p. 9 (Santorini, Greece, May 7–9, 2007)

G. Radhakrishnan, P. M. Adams, and L. S. Bernstein, "Probing the Chemical Role of Ambient O₂ in the Formation of Carbon Nanotubes via Excimer Laser Ablation," Proceedings of SPIE: Photon Processing in Microelectronics and Photonics VI Conference, Vol. 6458, p. 64581I (2007).

G. Radhakrishnan, P. M. Adams, and F. D. Ross, "Plume Diagnostics and Room-Temperature Deposition of Carbon Nanotubes and Nano-Onions at 248 nm," Journal of Physics, Vol. 59, No. 1, pp. 424–427 (2007).

J. L. Roeder, J. F. Fennell, T. L. Mulligan, and A. Korth, "Field-Aligned Energetic Electrons during the Storm of July 24, 2004: Cluster RAPID Observations," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SM53B-04.

P. R. Rousseau, P. H. Pathak, and H.-T. Chou, "A Time Domain Formulation of the Uniform Geometrical Theory of Diffraction for Scattering from a Smooth Convex Surface," IEEE Transactions on Antennas and Propagation, Vol. 55, No. 6 I, pp. 1522–1534 (June 2007).

R. S. Selesnick and S. G. Kanekal, "Variability of the Outer Radiation Belt Electron Content," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SM43B-1499.

Y. Sin, B. Foran, N. Presser, M. Mason, and S. C. Moss, "Reliability and Failure Mode Investigation of High-Power Multimode InGaAs Strained Quantum Well Single Emitters," Proceedings of SPIE: High-Power Diode Laser Technology and Applications V Conference, Vol. 6456, pp. 645605.1–645605.13 (2007).

D. Speckman, D. C. Marvin, J. Matossian, N. Ianno, and W. Stuckey, "Atomic Oxygen Testing of MgF₂ Coatings," Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, p. 4 (Waikoloa, HI, May 7–12, 2006).

J. R. Srour and J. W. Palko, "A Framework for Understanding Displacement Damage Mechanisms in Irradiated Silicon Devices," IEEE Transactions on Nuclear Science, Vol. 53, No. 6, pp. 3610–3620 (Dec. 2006).

J. Stillman, J. Judy, and H. Helvajian, "Processing Parameters for the Development of Glass/Ceramic MEMS," Proceedings of SPIE: Micromachining Technology for Micro-Optics and Nano-Optics V and Microfabrication Process Technology XII, Vol. 6462, p. 64620A (2007).

P. R. Straus, "Ionospheric Climatology Derived from GPS Occultation Observations Made by the Ionospheric Occultation Experiment," Advances in Space Research, Vol. 39, No. 5, pp. 793–802 (2007).

P. R. Straus, R. Bishop, and G. Crowley, "Measurements of the E- and F-Region Post-Sunset Ionosphere," AGU Fall Meeting (San Francisco, Dec. 11–15, 2006); EOS Transactions, American Geophysical Union, Vol. 87, No. 52, Suppl. (Dec. 26, 2006), Report No. SA33B-0275.

G. C. Valley, "Photonic Analog-to-Digital Converters," Optics Express, Vol. 15, No. 5, pp. 1955–1982 (Mar. 5, 2007).

G. C. Valley, G. A. Sefler, C. Chou, and B. Jalali, "Continuous Time Realization of Time-Stretch ADC," 2006 International Topical Meeting on Microwave Photonics, pp. 271–273 (Grenoble, France, Oct. 3–6, 2006).

F. J. Villegas, "Parallel Genetic-Algorithm Optimization of Shaped Beam Coverage Areas Using Planar 2-D Phased Arrays," IEEE Transactions on Antennas and Propagation, Vol. 55, No. 6 II, pp. 1745–1753 (June 2007).

J. W. Welch, "Comparison of Recent Satellite Flight Temperatures with Thermal Model Predictions," International Conference on Environmental Systems: Spacecraft Thermal Design and Technology (Norfolk,VA, July 2006), SAE Document 2006-01-2278.

R. P. Welle, C. Chrystal, and B. S. Hardy, "Standoff Pressures and Thermal Characterization of the Peltier-Actuated Microvalve," 25th International Conference on Thermoelectrics, p. 6 (Vienna, Austria, Aug. 6–10, 2006).

T. S. Yeoh, N. A. Ives, N. Presser, G. W. Stupian, M. S. Leung, J. L. McCollum, and F. W. Hawley, "Focused Ion Beam Tomography of a Microelectronic Device with Sub-2-nm Resolution," Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures, Vol. 25, No. 3, pp. 922–925 (2007).

M. A. Zurbuchen, W. Tian, X. Q. Pan, D. Fong, S. K. Streiffer, M. E. Hawley, J. Lettieri, Y. Jia, G. Asayama, S. J. Fulk, D. J. Comstock, S. Knapp, A. H. Carim, and D. G. Schlom, "Morphology, Structure, and Nucleation of Out-of-Phase Boundaries (OPBs) in Epitaxial Films of Layered Oxides," Journal of Materials Research, Vol. 22, No. 6, pp. 1439–1471 (June 2007).

Patents

(Nov. 2006–July 2007)

Charles C. Wang, "M-Ary Quadrature Amplitude Modulation (QAM) Bit-Boundary Turbo-Coded System," U.S. Patent No. 7,142,610, Nov. 2006; "M-Ary Phase-Shift Keying (PSK) Bit-Boundary Turbo-Coded System," U.S. Patent No. 7,142,611, Nov. 2006.

This M-ary phase-shift keying (PSK) bit-boundary turbo-coded system provides a soft metric generator using boundary lines within the symbol constellation space for gray-code encoded symbols in a turbo-code communication system using PSK modulation. It forms bit-boundary turbo-decoding metrics both for M-ary quadrature amplitude modulation and for M-ary PSK waveforms. The bit-boundary metrics and preferred gray-scale encoding provide improved bit-error ratio with efficient soft metrics computations and performance determinations and can be directly implemented without prior knowledge of channel condition. The system can be applied to various communication systems, including direct broadcasting, personal communications, and satellite communications.

R. B. Kaner, J. Huang, B. H. Weiller, and S. Virji, "Synthetic Method for Conducting Polymer Nanofibers," U.S. Patent No. 7,144,949, Dec. 2006; "Conducting Polymer Nanofiber Sensors," U.S. Patent No. 7,226,530, June 2007.

Conducting polymers can be used in chemical sensors based on changes in optical, electrochemical, or conductive properties. The small diameters of conducting polymer nanofibers result in high surface areas and faster diffusion rates of gas molecules into the nanofiber material as compared with standard thin-film coatings. No practical nanostructured conducting polymer sensors have been available because of the lack of reliable synthesis methods for high-quality materials in bulk quantities. This invention uses a simple aqueous and organic interfacial polymerization method for producing conducting polymer nanofibers based on chemical oxidative polymerization of organic monomers in a two-phase solvent system. This template-free process is a practical way to produce large quantities of purified nanofibers with narrow size distributions of diameters less than 500 nm. The diameter of the nanofibers can also be controlled by choice of synthesis conditions. Aqueous dispersions of the nanofibers can be used to drop cast nanofiber films on planar interdigitated electrodes to form chemical sensors. The resulting sensors have superior performance in both sensitivity and time response to a variety of gases.

R. Kumar and T. M. Nguyen, "Polyphase Channelization System," U.S. Patent No. 7,145,972, Dec. 2006.

The digital implementation of communication systems for broadband signals requires analog-to-digital converters (ADC) operating at high speed. This high-speed conversion imposes limitations, and for a wideband signal in conventional implementation, the ADC may not be available, may not have the required number of bits, may require excessive power, or may be too expensive. This invention uses parallel low-speed ADCs in combination with polyphase channelization to process wideband signals in communications systems. A polyphase channelizer downconverts the wideband input signal into baseband quadrature signals that are fed into the parallel ADCs. The converter-channelized outputs from the ADCs are then processed by a filter bank and a fast Fourier transform processor. This parallel architecture operates at significantly lower speed to effectively provide a high-speed analog-to-digital conversion. The method is well suited for satellite communication systems using digital signal processing of broadband or wideband signals.

B. S. H. Michel, "Cooperative Adaptive Web Caching Routing and Forwarding Web Content Data Requesting Method," U.S. Patent No. 7,146,429, Dec. 2006.

Traditional, noncooperative Web-caching systems reduce an organization's Internet traffic load by locally storing copies of requested content that can be quickly retrieved without sending requests via the Internet. A cooperative caching system, by contrast, uses multiple caches to store requested content and can further reduce overall Internet traffic load and scale to a larger user base. However, locating the requested content can be a problem. Typically, cooperative Web-caching systems maintain a logical central directory, so that one Web cache can easily locate the requested content stored on another cache. This invention is an adaptive and cooperative Web-caching method that uses an "Internet style" application-level routing and forwarding approach to locate stored Web content along a path within a network of caches. The caches construct and maintain routing and forwarding tables that store decomposed URLs in a compressed format. The cache's forwarding table efficiently translates a user request to the IP address of the next-hop cache server along a path in the Web cache network where the replicated Web content can be retrieved. Consequently, Web content can be replicated along the paths within the caching network, reducing Internet traffic load and perceived content fetching delay.

K. Siri, "Uniform Converter Output Voltage Distribution Power System," U.S. Patent No. 7,151,362, Dec. 2006.

A common practice in managing expandable power systems is to use identical dc-to-dc converters connected in a parallel-input parallel-output configuration with uniform power distribution among them. A less common practice is to connect the converters using a parallel-input and series-output configuration. However, such series-output–connected converters lack the ability to precisely control the proper distribution of power. Internal component variations or mismatches can result in undesirable nonuniform output voltage distribution, causing overthermal stresses to those converters with higher output voltages, despite the parallel connection of the converters to the same input voltage source. This invention offers a unified control approach to achieve uniform distribution of converter output voltages, leading to uniform power distribution and robust system reliability. It compares the converter output voltages with a distribution reference signal, and then generates separate control signals for regulation of individual converters. This provides improved power system stability and uniform output voltage distribution among the converters. Employing a common regulation control signal, the controller can also provide system output-voltage regulation, system input-current limiting, proportional-voltage control, relaxed-voltage uniformity, and fault-tolerant power control.

W. R. Crain Jr., D. J. Mabry, J. B. Blake, and N. Katz, "Radiation Dosimeter Device," U.S. Patent No. 7,157,715, Jan. 2007; "Radiation Dosimeter System," U.S. Patent No. 7,223,979, May 2007.

Microelectronics in spacecraft are vulnerable to degradation and even failure from the radiation dose caused by energetic electrons and ions. Radiation sensors, such as dosimeters, are therefore needed onboard the spacecraft to continuously monitor the radiation exposure. Some current dosimeters, however, do not measure the radiation directly, and thus are prone to error. Others do measure the radiation directly, but are heavy, consume lots of energy, need a clear field of view for each sensor, and must be fine-tuned for each host vehicle. This invention is a dosimeter that provides direct measurements of the energy deposited in test masses of silicon in packages, including charge contribution prior to radiation energy threshold detection. This dosimeter can be made small, is relatively easy to manufacture, and offers preintegration performance improvement, mounting flexibility, and conventional electrical interface. The dosimeter provides chained analog outputs that can be read by conventional satellite systems that accept analog input from sensors, such as temperature sensors. Many of the devices can be deployed aboard a single spacecraft. They can be daisy-chained, distributed, and used for generating a radiation exposure profile of the spacecraft.

H. G. Muller, "Method of Making Copper and Carbon Nanotube Thermal Conductor," U.S. Patent No. 7,197,804, Apr. 2007.

High-power systems tend to generate heat in localized areas, causing the devices used in such systems to overheat. The key to efficient cooling is to bring the thermal conductor as close as possible to the devices and create a good thermal contact. The best thermal conductors, however, tend to have a much higher coefficient of thermal expansion than the semiconductor devices. This invention is a thermal conductor made of copper and carbon nanotubes compressed and cold rolled together so that the carbon nanotubes are aligned. The conductor has increased thermal and electrical conductivity and a reduced coefficient of thermal expansion. Various pressures, temperatures, and mixture ratios can be used to form the thermal conductor and achieve different coefficients of thermal expansion, thermal conductivities, and electrical conductivities. The conductor can be used as a conducting heat sink, such as a laser submount, for heat dissipation and electrical grounding of high-power electrical components and circuits, such as a laser diode.

J. J. Poklemba, G. S. Mitchell, and R. F. Smith, "Quadrature Vestigial Sideband Digital Communications Method and System with Correlated Noise Removal," U.S. Patent No. 7,200,193, Apr. 2007.

One way to transmit digital data in a bandwidth-efficient manner is to use quadrature vestigial-sideband (QVSB) transmission. The QVSB technique enables simultaneous transmission of two independent data streams on quadrature carriers, providing twice the information-carrying capacity of vestigial-sideband transmission. The disadvantages of QVSB, however, are greater implementation complexity and typically reduced detection noise margins because of crosstalk between the quadrature channels. Previous methods aimed at unraveling the crosstalk have proved unsatisfactory because of the effects of correlated noise. This invention is a QVSB method with correlated noise removal embodied in a QVSB receiver. Correlated-noise components in each of the quadrature channels are estimated and subtracted from their respective incoming signals, plus noise, which degenerates the remainder of the signal processing to a quadrature-coupled, partial-response detection problem in white noise. The principles of this invention are applicable to a variety of applications, particularly those that require bandwidth-efficient digital data transmission.

P. A. Dafesh, "Direct-Sequence Spread-Spectrum Optical-Frequency-Shift-Keying Code-Division-Multiple-Access Communication System," U.S. Patent No. 7,200,342, Apr. 2007.

Fiber-optic communications have become increasingly popular as a means to extend the bandwidth of existing networks. A number of different spread-spectrum code division multiple-access (CDMA) schemes have been proposed to allow asynchronous user access to optical networks. Optical CDMA communications can increase the capacity and improve the performance of existing wavelength division multiplexing systems, without altering the basic infrastructure of existing fiber-optic networks. In current approaches, however, the data are susceptible to amplitude fluctuations, which result in degraded communications. This invention is an optical CDMA system that uses direct sequence spectrum spreading and frequency shift-keying modulation. It provides a secure means to transport multiple user data across a wideband network while maintaining the flexibility to reassign secure spreading sequences to different user channels. The system has applications to fiber-optic networks and secure communication along both free-air and fiber-optic links.

J. C. Camparo and C. M. Klimcak, "Discharge Lamp Stabilization System," U.S. Patent No. 7,221,231, May 2007.

Vapor-cell atomic clocks employ an RF-discharge lamp to generate the atomic clock signal. Therefore, the performance of the atomic clock depends on the spectral output of the RF-discharge lamp (through the light-shift mechanism), which in turn is determined by the detailed properties of the light-generating plasma within the lamp. The plasma temperature and power changes of the RF-discharge lamp are not characterized or stabilized in an atomic clock system, which can lead to atomic clock instability. This invention is a system that senses the acoustic ion oscillations in the 20 kHz range that come from the discharge lamp. The frequency of the acoustic ion oscillations can be used to measure the amount of power coupled into the plasma, and thus to determine the RF performance characteristics of the lamp. The RF power of the lamp can be stabilized by locking the acoustic oscillation frequency of the plasma ions to a specific value in the 20 kHz range. This stabilizes the electron temperature of the plasma and the spectral character of the RF-discharge lamp, resulting in improved vapor-cell clock performance.

Y. Sin and N. Presser, "Focused Ion Beam Heater Thermally Tunable Laser," U.S. Patent No. 7,224,708, May 2007.

Tunable lasers at the wavelength of 1550 nm are indispensable components for all optical networks. Both distributed Bragg reflector (DBR) lasers and distributed feedback (DFB) lasers could be used; however, DBR lasers require complicated fabrication steps in addition to sophisticated control electronics, and DFB lasers suffer from a narrow tuning range. This invention is a new method of thermal tuning that significantly improves the tuning range of DFB lasers. One method of thermally tuning the lasers is to form thin-film heaters near the laser active region. This technique, however, requires high heater current because of the low electrical resistance from the platinum thin films deposited by conventional techniques. In this invention, a focused ion beam technique deposits platinum thin-film heaters in thermally tunable lasers. Focused ion beam platinum is not normally suitable for use in microelectronic devices because a significant amount of carbon is incorporated into platinum during the deposition process. The impurity, however, provides high electrical resistance, allowing excellent thermal tuning efficiency of the laser. The integrated laser is tunable over a wide wavelength range of ~5 nm using a heater current of only 13 mA.

M. J. Lange, "Compensating Structures and Reflector Antenna Systems Employing the Same," U.S. Patent No. 7,227,501, June 2007.

Increasing the capacity of small Earth station antennas necessitates the implementation of multiple beams across multiple frequency bands. However, moving to higher frequencies requires the use of larger Earth station antennas to accommodate the smaller orbital separation of the satellites. Increasing the size of the Earth station antenna is unacceptable for many applications. Additionally, it is sometimes desirable to modify the phase and amplitude distribution of satellite antennas using dielectric lenses. However, the size and weight of spacecraft payloads are heavily constrained and make the massive dielectric lenses infeasible. This invention provides both a means of maintaining the small Earth station antenna while providing the ability to add multiple beams across multiple frequency bands, and the ability to implement low-loss, lightweight RF lenses. Compensating structures formed from multiple layers of nonuniform arrays of conductive patches are configured to modify the phase and amplitude distribution of an incident field in such a way as to provide additional degrees of freedom in placement of traditional scalar feed horns while increasing the efficiency of the antenna system. This allows the use of smaller reflectors and provides the desired element pattern modification in phased array systems.

R. B. Dybdal and D. D. Pidhayny, "Methods and Systems for Tracking Signals with Diverse Polarization Properties," U.S. Patent No. 7,239,275, July 2007.

Radio-frequency signals have polarization properties that characterize the orientation of the incident electric fields. Communication system antennas are generally designed to receive signals having a specified polarization, but incident fields matching this specified polarization are not always received. Narrow-beamwidth antennas must track the signal's direction to maintain the received signal level, but cannot do so when the incident and design polarizations are cross-polarized. This crossed polarized signal condition also reduces the signal level and hence the system sensitivity. This invention presents several methods for tracking signals with diverse polarization properties. One method applies complex weighting circuitry to match the incident signal's polarization. Another method determines the stronger signal level in the two orthogonally polarized tracking channels, and uses this to select a polarization of the data channel. A third method sequentially sums the received orthogonal signal levels for tracking and selects the stronger received signal polarization for the data channel. These methods make antenna tracking independent of the incident polarization while keeping a high received signal level.

G. Radhakrishnan, "Method for Producing Carbon Surface Films by Plasma Exposure of a Carbide Compound," U.S. Patent No. 7,241,475, July 2007.

A hard and low-friction coating is of great value to devices such as moving microelectromechanical systems (MEMS) that have moving mechanical parts and are susceptible to high wear and damage from frequent sliding contact. A multifunctional coating can be produced by depositing a thin layer of low-friction carbon on top of a hard, wear-resistant carbide coating. Chlorination of carbides at high temperatures on the order of 1000°C will remove the metal from the carbide, leaving behind a lubricious carbon film. MEMS devices are typically produced on silicon substrates, which are attacked by the chlorination process, and the high temperatures involved degrade the standard mask materials used for protecting the silicon. This invention is a method for producing low-friction carbon coatings at low temperatures on bulk or thin films of wear-resistant carbides. A reactive halogen plasma is generated from low-pressure halogen gases, such as chlorine or fluorine, using a radio-frequency source. The surface of a metal carbide is then exposed to the halogen plasma at or near room temperature. The halogen radicals react with the carbide and extract the metal constituent from the carbide, leaving a pure lubricious surface film of carbon. This method is easy to implement, can treat large areas, and can be applied to any bulk or thin-film metal carbide.

To Fall 2007 Table of Contents