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At least 1,657 records · Page 92

Mars 2020 Entry, Descent, and Landing as Observed by Radio Science Techniques at UHF and X-band Frequencies

On February 18, 2021, NASA’s Mars 2020 Rover “Perseverance” conducted the Entry, Descent, and Landing (EDL) sequence to land safely on the surface of Mars at Jezero Crater. Due to the criticality of the EDL sequence, redundant telecommunications strategies were utilized to observe the event. The rover transmitted an X-band (8.4 GHz) signal encoded with Multiple Frequency Shift Keying tones direct-to-Earth and a UHF (401.5 MHz) signal with 8 kbps encoded telemetry to orbiters, which relayed the signal back to Earth at X-band. NASA’s Deep Space Network complexes at Goldstone, California and Madrid, Spain received the direct-to-Earth X-band signal. Two of the largest steerable radio telescopes in the world, the 100-meter Green Bank Telescope in West Virginia and the Effelsberg 100-meter Radio Telescope in Germany also received the UHF carrier signal on Earth. During the EDL event, full spectrum recordings of the UHF and X-band signals were captured at these observatories using open-loop receivers. Real-time and post-processing signal analysis to determine power level, received frequency, and Doppler shift allowed determination of the spacecraft’s health and safety state during critical sequences, including event detection such as atmospheric entry, plasma blackouts, and parachute deployment. Simultaneous observations of the UHF and X-band radio links allow for redundancy in the event of a fault and greatly improve confidence in Doppler event detection.

Gladden, Roy↗

New Retropropulsion Concept with NTAC Power for Mars Entry

Since the initial deployments of probes, orbiters, and rovers on Mars, there have been many ideas and concepts on how to perform an entry, descent, and landing (EDL) process efficiently and safely through the Martian atmosphere to place payloads onto the surface of Mars. Among the missions sent to perform EDL on Mars, only roughly sixty percent of the missions have been successful. The 5 minutes to 20 minutes of communication gap due to long-range telecommunications to Earth, described as seven minutes of terror, add to the complexity of EDL missions to Mars. As the payloads have become larger, the method of EDL has become more complex. To place an automobile-size science rover on the Martian surface requires the use of retrorockets mounted on a Sky Crane during the final subsonic stage of EDL. Larger payloads will require more propellant and more and/or larger retropropulsion engines during the earlier supersonic stage of EDL. The Sky Crane concept may not be scalable for these larger payloads and during supersonic flight; hence, new approaches are sought. A new power technology invented at NASA called Nuclear Thermionic Avalanche Cell (NTAC) may offer an additional solution. Powered by NTAC, the newly invented retropropulsion concept would ingest carbon dioxide gas, heat it up and blast it out as a new feature of the EDL process. NTAC would be reusable as a primary power source for payloads such as excavators, three-dimensional (3D) printers, or mobile equipment for mining, construction, and additive manufacturing tasks. Since NTAC would need to be landed with its host payload or as a standalone power package, assessing its ability to assist in its own EDL seems reasonable. The purpose of this Technical Memorandum (TM) is to examine the performance of NTAC in the context of EDL at Mars for motivating studies for integrating NTAC into future Mars mission architectures.

Mars entry↗

Gateway at the Crossroads of Sustainable Lunar Exploration

The Gateway Program has made substantial design and development progress toward delivering a small, human-tended lunar space station purposefully designed to enable sustainable human exploration. The Program integrates partners and providers organizationally and physically as part of the spacecraft. The Power and Propulsion Element (PPE) and the Habitation and Logistics Outpost (HALO) with the European System Providing Refueling, Infrastructure and Telecommunications (ESPRIT) HALO Lunar Communications System (HLCS) have begun manufacturing the long lead components and will be launched first as a Co-Manifested Vehicle (CMV). The International Habitat (I-Hab) and ESPRIT Refueling Module (ERM) are passing life cycle milestones and include capabilities key for human crewmembers, such as windows, private sleeping quarters, and galley functions. The Logistics Module (LM) may provide a variety of services to Gateway depending on each mission. Requirements for the airlock have been developed, including requests that it support the integrated spacecraft with functions like augmenting heat rejection capabilities, and interfaces with new spacesuits will soon be developed in more detail. As a critical element of the architecture for solar system exploration, Gateway implements key tenets and features of international interoperability standards necessary to operate with multiple visiting vehicles and lunar assets, especially avionics, communications, and docking. Specific choices such as software architecture and standards, power standards, and robotics standards make it possible to utilize heritage or proprietary technology, yet still operate as one spacecraft. Engineering teams are evaluating many possible future missions to be executed at or utilizing the Gateway. The system architecture protects for an evolvable, extensible, and flexible capability. Designing systems robust enough to serve as a cornerstone of exploration activities for decades while remaining adaptable is not without its challenges. The detailed integration activities have revealed challenges and the need to mature key technologies. Refueling is a key component of achieving long life for Gateway, with unique operations to plan, safety concerns to mitigate, and risk reduction activities to conduct to better understand the system. The constraints and impacts of the design of visiting vehicles is also an important concern, with orientation constraints, control of attitude and orbit of the Gateway with docked visiting vehicles. Tradeoffs between robust maintainable systems and lightweight, compact systems must be balanced. Opportunities still exist for adding additional advanced capabilities to increase and extend Gateway’s benefits, such as intravehicular robotics, autonomous Guidance Navigation and Control (GN&C), and augmented control propulsion, heat rejection, or other services.

Molly S Anderson↗

Development Testing of the Gateway Integrated Bipropellant Refueling Subsystem

The Lunar Gateway is a deep space orbiting outpost being developed by the National Aeronautics and Space Administration (NASA) in partnership with the European Space Agency (ESA) and other domestic and international partners. Because Gateway is a vital component of NASA’s Artemis program supporting long-term human exploration of the moon, it is designed for on-orbit refueling to allow for a longer life performance. The reaction control system (RCS) bipropellant refueling system onboard the station will have the capability to transfer propellants, monomethyl hydrazine (MMH) and mixed oxides of nitrogen-3 (MON-3), under controlled conditions and will span across three modules: the European System Providing Refueling Infrastructure and Telecommunication Refueling Module (ESPRIT-RM or ERM), the Habitation and Logistics Outpost (HALO), and the Propulsion and Power Element (PPE). These propellant transfers are complex operations with known hazards, and one of the risk areas is exceeding the flight system’s maximum design pressure (MDP) in priming and refueling pause/stop operations. In priming, liquid propellant is transferred from a pressurized source tank to evacuated transfer lines, which could result in excessive transient surge pressures and potentially damage hardware. In refueling pause/stop operations, fast-acting isolation valves (IV) are closed, which could lead to damaging water hammer. To mitigate these risks and develop the system, a collaborative NASA/ESA/Thales Alenia Space – United Kingdom (TAS-UK) test program was completed at TAS-UK on a simplified refueling breadboard representing ERM, HALO, and PPE bipropellant transfer systems. The objectives of the integrated breadboard testing were to (1) gather performance data to characterize and demonstrate critical refueling operations, (2) help inform flight designs, and (3) to validate numerical models that can be extended to predicting flight system performance. Integrated breadboard test data has shown the architected system performance is closing initial design assumptions. Further testing with propellant on a higher fidelity fluid simulator and analysis are planned.

Adela D Han↗

Development Testing of the Gateway Integrated Bipropellant Refueling Subsystem

The Lunar Gateway is a deep space orbiting outpost being developed by the National Aeronautics and Space Administration (NASA) in partnership with the European Space Agency (ESA) and other domestic and international partners. Because Gateway is a vital component of NASA’s Artemis program supporting long-term human exploration of the moon, it is designed for on-orbit refueling to allow for a longer life performance. The reaction control system (RCS) bipropellant refueling system onboard the station will have the capability to transfer propellants, monomethyl hydrazine (MMH) and mixed oxides of nitrogen-3 (MON-3), under controlled conditions and will span across three modules: the European System Providing Refueling Infrastructure and Telecommunication Refueling Module (ESPRIT-RM or ERM), the Habitation and Logistics Outpost (HALO), and the Propulsion and Power Element (PPE). These propellant transfers are complex operations with known hazards, and one of the risk areas is exceeding the flight system’s maximum design pressure (MDP) in priming and refueling pause/stop operations. In priming, liquid propellant is transferred from a pressurized source tank to evacuated transfer lines, which could result in excessive transient surge pressures and potentially damage hardware. In refueling pause/stop operations, fast-acting isolation valves (IV) are closed, which could lead to damaging water hammer. To mitigate these risks and develop the system, a collaborative NASA/ESA/Thales Alenia Space – United Kingdom (TAS-UK) test program was completed at TAS-UK on a simplified refueling breadboard representing ERM, HALO, and PPE bipropellant transfer systems. The objectives of the integrated breadboard testing were to (1) gather performance data to characterize and demonstrate critical refueling operations, (2) help inform flight designs, and (3) to validate numerical models that can be extended to predicting flight system performance. Integrated breadboard test data has shown the architected system performance is closing initial design assumptions. Further testing with propellant on a higher fidelity fluid simulator and analysis are planned.

Adela D Han↗

Stratospheric Operations Market

This presentation has been prepared for the 2024 Stratospheric Operations and Research Symposium (SOaRS2024) held at the University of North Dakota. The presentation includes contributions from NASA, the FAA and results of a market study carried out by LMI for NASA. It provides an overview for industry and other government agencies why this novel traffic management system, called upper Class E Traffic Management System - ETM, will lead to an increase in access to the Stratosphere. The slides emphasize that expected High-Altitude Balloons, solar-powered High-Altitude long Endurance Aircraft, Airships, Supersonic and Hypersonic aircraft will benefit from this concept by exemplifying how markets in telecommunication, public safety and transportation are expected to grow. By comparing expected demand and showing that current concepts, such as Altitude Reservation (ALTRV) will not be able to meet demand as such showing that the ETM concept aims to increase safety, efficiency and fairness in a collaborative environment. Further, past work and engagement with Industry participants is highlighted.

stratosphere↗

Analyzing Launch Operations using the Spaceport Throughput Analysis Resource (STAR)

NASA’s Kennedy Space Center (KSC) and Cape CanaveralSpace Force Station (CCSFS) are the world’s preeminent multi-user spaceport, providing facilities and launch capabilities to the agency, NASA’s commercial partners, and other government agencies. KSC works to ensure an environment in which NASA’s programs and other users can safely and effectively carry out their operations. Approximately 100 launches are expected to take place in 2024. KSC needs to meet the needs of customers who request launches based on their own schedules, but who may not be aware of KSC-wide resource limitations and external constraints on launch operations. KSC-wide resources include telecommunications, range tracking, commodities such as Helium and Nitrogen, and special equipment needed to support launches. External constraints include seasonal launch operations. Since space vehicles are complex and launch operations are uncertain, unexpected events can also cause delays in operations. The Spaceport Throughput AnalysisResource (STAR) assesses whether a specific set of pro-posed launches and associated activities can be performed given the resources KSC currently has available, and external constraints imposed on KSC operations. STAR integrates short-horizon scheduling and simulation of launches using a monte-carlo approach driven by configurable probabilities of different classes of event outcomes, including de-lays and worst-case use of resources. The resulting analyses inform stakeholders of key constraints preventing customers from being able to perform their missions as desired, and give insight into how to improve spaceport throughput. The rest of the paper is organized as follows. In 2 we de-scribe the problem STAR is intended to solve. In Section3 we formally describe the scheduling problem ingredients. In Section 4 we describe how manifests are simulated. InSection 5 we describe the constraints problem that is solved when rescheduling. In Section 6 we describe what information is recorded during manifest simulation in order to evaluate delays. In Section 7 we describe the specific problem solved for KSC. In Section 8 we describe the challenges of knowledge engineering for STAR.

Planning Scheduling Analysis↗

Thermal Analysis of Refueling Propellant Systems for PPE

To support the sustainability of Gateway, approach the challenge of sustainable presence beyond low earth orbit, and provide proving grounds for future missions beyond the surface of the moon, refueling capabilities must be incorporated into Gateway. The objective is to replenish propellants into the Power and Propulsion Element (PPE) from the European System Providing Refueling, Infrastructure and Telecommunications (ESPIRIT) through the Habitation and logistics outpost (HALO). PPE refueling will consist of a bipropellant transfer system, as well as a main propellant transfer system. Refueling the Power and Propulsion Element in near rectilinear halo orbit can present various issues, and to thermally maintain the refueling system during this event requires diligent planning and thermal design. Presently, a thermal model exists to analyze the components of the refueling system as the development of PPE continues. The analysis from the thermal model will verify the integrity of the all the components during a refueling event throughout the duration of the mission given various environmental differences. To confidently refuel PPE, thermal analysis, and various tests of the refueling components, must be completed to achieve the desired sustainability of Gateway.

Ethan Sparks↗

International Coordination and Cooperation on LunaNet Spectrum

LunaNet is planned to be the network of networks operated by a set of cooperating organizations to provide interoperable Communications, networking, Position, Navigation, and Timing (CPNT) services to users on and around the Moon based on a framework of mutually agreed-upon standards, protocols, frequency bands and interface requirements. LunaNet follows a service-oriented architecture that is agnostic about the types of organizations that provide services, e.g., government, industry, or academia. LunaNet is open, scalable, resilient, secure, and extensible. To achieve these goals, LunaNet Service Providers (LNSP) must coordinate with each other to define and develop the architecture, to plan initial and evolved capabilities, and to operate their networks. One of the central LunaNet tenets is the use of shared spectrum. For example, the Lunar Augmented Navigation Service (LANS) acts like a Global Navigation Satellite System (GNSS) such as the US Global Positioning System (GPS) or European Galileo but the LNSPs’ contributions to LunaNet must use the same frequency band (2483.5 MHz-2500.0 MHz) and transmit the same waveform synchronized by highly accurate clocks so that Users ‘see’ one virtual network and use the same multilateration algorithm to determine their positions. This necessitates a high degree of spectrum coordination. NASA’s Lunar and Human Spaceflight Spectrum Management Team has been actively supporting development of the LunaNet Interoperability Specification (LNIS), soliciting inputs from spectrum policy and planning experts across NASA, ESA and JAXA. Cislunar spectrum use considerations have been studied and adjudicated within the Space Frequency Coordination Group (SFCG) and inform the ongoing discussion of a lunar communication and navigation architecture within the existing radio regulatory framework of the International Telecommunication Union, leading to the 2027 World Radiocommunication Conference (WRC-27). The frequency plan contained in the publicly released draft of the LunaNet Interoperability Specification reflects the initial phase of exploration (roughly to 2030) defining an optimal set of radio frequencies in appropriately allocated services consistent with WRC-23 decisions for use by known or planned CPNT applications, while striving to maximize coexistence and compatibility amongst cislunar systems and other systems within the near-Earth regime (< 2 million km from Earth). Important considerations include: protection of extremely sensitive receive-only radio astronomy systems on the lunar far side, known as the Shielded Zone of the Moon (SZM); compatibility between Direct with Earth (DWE) communications links and links needed to support relay satellites in lunar orbit with their customer systems on orbit or on the lunar surface; compatibility between multiple lunar surface communications systems and capabilities over varied and challenging terrain and distances; as well as ensuring compatibility and interoperability between navigation systems which either leverage Earth-based or in-situ lunar systems. In addition, the lunar CPNT architecture is envisioned to be the basis – with adjustments – of the future Mars CPNT architecture as we expand into the solar system using Interplanetary Networking (IPN). The second phase of lunar spectrum definition will address planned international capabilities for the next decade that will require action at WRC-27 and beyond. This paper will discuss each of these considerations in more depth and how the current LunaNet frequency plan addresses them.

LunaNet↗

Gateway Program Development Progress

This paper provides an overview and status of Gateway, humanity’s first space station to orbit the Moon providing vital support for a sustained, long-term human return to the lunar surface and a steppingstone to Mars as part of the Artemis missions. As a lunar outpost, Gateway is a destination for deep space crew expeditions and science investigations, a port for deep space transportation, including landers transiting to the lunar surface or spacecraft embarking to deep space destinations beyond the Earth-Moon system. The National Aeronautics and Space Administration (NASA) leads the Program and is the integrator of the spaceflight capabilities and contributions of U.S. commercial partners and international partners to develop Gateway. This paper will provide an overview of Gateway’s major components in various stages of development. The entire Gateway spacecraft is at preliminary design level of maturity, with some components at or near critical design review. Gateway’s major components are the Power and Propulsion Element; the Habitation and Logistics Outpost; Deep Space Logistics; the International Habitation module; Gateway External Robotics System; European System Providing Refueling, Infrastructure and Telecommunications; and an Airlock. This paper will also provide an update on the status of the integration activities necessary to fly and operate this complex, next-generation integrated spacecraft for a minimum 15-year design life, including systems engineering integrated analysis cycles, the autonomous Vehicle System Manager software, verification and validation labs, and common vehicle equipment. Expanding on the successful partnership that has provided over 20 years of continuous crew operations in low-Earth orbit on the International Space Station, Gateway is an evolution of this extraordinary partnership leveraging the capabilities of each contributor to expand humankind’s sustained exploration deeper into the cosmos. Highlighting the international program with participation from multiple space agencies, this paper will also provide a status of Gateway multilateral governance structure and international agreements.

Gateway↗

The NASA Disasters Response Coordination System’s (DRCS) Response to the 2024 Hurricane Season

The National Aeronautics and Space Administration (NASA) Disasters Response Coordination System (DRCS) leverages the best available science and expertise to aid federal, state, local, and non-governmental organization (NGO) partners in addressing identified needs during a disaster response. During the 2024 hurricane season, the DRCS activated for seven hurricanes/tropical storms, providing openly available geospatial data through NASA’s Disasters Mapping Portal. Hurricanes Helene and Milton were major hurricanes that impacted the southeastern United States within weeks of one another. Impacts from Helene and Milton to the region included inland flooding, record coastal storm surge, over a thousand landslides, and regional power and telecommunications outages. In response to Helene and Milton, DRCS provided actionable information and products to stakeholders, including Synthetic Aperture Radar (SAR) analysis for landslide and flood detection, Black Marble nighttime lights products for assessing power outages, and Normalized Difference Vegetation Index (NDVI) analysis for post-event vegetation change detection. NASA deployed an Uninhibited Aerial Vehicle SAR (UAVSAR) instrument to collect data on flood extent, providing crucial information on affected communities. Additionally, astronauts aboard the International Space Station (ISS) collected hand-held photography along the paths of Hurricane Helene and Milton to aid in response efforts. Here, we summarize the DRCS responses to Helene and Milton, in particular highlighting the information and products that were provided by the DRCS and how they were utilized by partners to address immediate response needs.

Earth observations↗

Remote Science at Sea With Remotely Operated Vehicles

Conducting sea-going ocean science no longer needs to be limited to the number of berths on a ship given that telecommunications, computing, and networking technologies onboard ships have become familiar mechanisms for expanding scientists’ reach from onshore. The oceanographic community routinely works with remotely operated vehicles (ROVs) and pilots to access real-time video and data from the deep sea, while onboard a ship. The extension of using an ROV and its host vessel’s live-streaming capabilities has been popularized for almost 3 decades as a telepresence technology. Telepresence-enabled vessels with ROVs have been employed for science, education, and outreach, giving a greater number of communities viewing access to ocean science. However, the slower development of technologies and social processes enabling sustained real-time involvement between scientists on-ship and onshore undermines the potential for broader access, which limits the possibility of increasing inclusivity and discoveries through a diversity of knowledge and capabilities. This article reviews ocean scientists’ use of telepresence for ROV-based deep-sea research and funded studies of telepresence capabilities. The authors summarize these studies findings and conditions that lead to defining the use of telepresence-enabled vessels for “remote science at sea.” Authors define remote science at sea as a type of ocean expedition, an additional capability, not a replacement for all practices by which scientists conduct ocean research. Remote science for ocean research is an expedition at-sea directed by a distributed science team working together from at least two locations (on-ship and onshore) to complete their science objectives for which primary data is acquired by robotic technologies, with connectivity supported by a high-bandwidth satellite and the telepresence-enabled ship’s technologies to support the science team actively engaged before, during, and after dives across worksites. The growth of productive ocean expeditions with remote science is met with social, technical, and logistical challenges that impede the ability of remote scientists to succeed. In this article, authors review telepresence-enabled ocean science, define and situate the adjoined model of remote science at sea, and some infrastructural, technological and social considerations for conducting and further developing remote science at sea.

marine technology↗

AstroDOME: Standardized, Mass-Produceable, Small NASA Astrophysics Observatories for Big Missions

NASA’s Goddard Space Flight Center is investigating the use of small, commercial off the shelf (COTS) spacecraft to enable breakthrough astrophysics research at radically reduced cost over previous generations of missions. This paper will focus on the Mission Systems perspective of this investigation. It will cover the spacecraft to instrument interface, and lessons learned in early concept payload development. Low-cost COTS spacecraft have proliferated in the last ~5 years. They represent an order of magnitude reduction in the cost of spacecraft bus development and acquisition. They are enabled by the advent of low-cost smallsat launch options in the immediately preceding years, and are seeded by recent distributed and disaggregated missions in other sectors such as telecommunications megaconstellations (e.g. Starlink, OneWeb, Project Kuiper) and ongoing Space Development Agency (SDA) developments. Our study was tasked with developing a standardized, mass-produceable, astrophysics payload which is reconfigurable to different wavelength bands while maintaining a single optics bench design, and a standardized mechanical, electrical, data, and thermal interface to the spacecraft bus, and which may be reconfigured to multiple COTS spacecraft offerings. In this paper we will discuss lessons learned from our case study. We will also present identified keys to mission success for performing cutting edge astrophysics observations while taking advantage of economies of scale with a disaggregated, standardized architecture.

Matthew Marcus↗

Applications of Emerging Parallel Optical Link Technology to High Energy Physics Experiments

Modern particle detectors depend upon optical fiber links to deliver event data to upstream trigger and data processing systems. Future detector systems can benefit from the development of dense arrangements of high speed optical links emerging from the telecommunications and storage area network market segments. These links support data transfers in each direction at rates up to 120 Gbps in packages that minimize or even eliminate edge connector requirements. Emerging products include a class of devices known as optical engines which permit assembly of the optical transceivers in close proximity to the electrical interfaces of ASICs and FPGAs which handle the data in parallel electrical format. Such assemblies will reduce required printed circuit board area and minimize electromagnetic interference and susceptibility. We will present test results of some of these parallel components and report on the development of pluggable FPGA Mezzanine Cards equipped with optical engines to provide to collaborators on the Versatile Link Common Project for the HI-LHC at CERN.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Terahertz Light Source and User Area at FACET

FACET at SLAC provides high charge, high peak current, low emittance electron beam that is bunched at THz wavelength scale during its normal operation. A THz light source based coherent transition radiation (CTR) from this beam would potentially be the brightest short-pulse THz source ever constructed. Efforts have been put into building this photon source together with a user area, to provide a platform to utilize this unique THz radiation for novel nonlinear and ultrafast phenomena researches and experiments. Being a long-time underutilized portion of the electromagnetic spectrum, terahertz (100 GHz {approx} 10 THz) spectral range is experiencing a renaissance in recent years, with broad interests from chemical and biological imaging, material science, telecommunication, semiconductor and superconductor research, etc. Nevertheless, the paucity of THz sources especially strong THz radiation hinders both its commercial applications and nonlinear processes research. FACET - Facilities for Accelerator science and Experimental Test beams at SLAC - provides 23 GeV electron beam with peak currents of {approx} 20 kA that can be focused down to 100 {mu}m{sup 2} transversely. Such an intense electron beam, when compressed to sub-picosecond longitudinal bunch length, coherently radiates high intensity EM fields well within THz frequency range that are orders of magnitude stronger than those available from laboratory tabletop THz sources, which will enable a wide variety of THz related research opportunities. Together with a description of the FACET beamline and electron beam parameters, this paper will report FACET THz radiation generation via coherent transition radiation and calculated photon yield and power spectrum. A user table is being set up along the THz radiation extraction sites, and equipped with various signal diagnostics including THz power detector, Michelson interferometer, sample stages, and sets of motorized optical components. This setup will also be presented. Potential THz research areas including studies of magnetism, ferroelectric switching dynamics, semiconductor devices and chemical reaction controls have already been proposed for the FACET THz area.

43 PARTICLE ACCELERATORS↗

Bandgap Engineering of InP QDs Through Shell Thickness and Composition

Fields as diverse as biological imaging and telecommunications utilize the unique photophysical and electronic properties of nanocrystal quantum dots (NQDs). The development of new NQD compositions promises material properties optimized for specific applications, while addressing material toxicity. Indium phosphide (InP) offers a 'green' alternative to the traditional cadmium-based NQDs, but suffers from extreme susceptibility to oxidation. Coating InP cores with more stable shell materials significantly improves nanocrystal resistance to oxidation and photostability. We have investigated several new InP-based core-shell compositions, correlating our results with theoretical predictions of their optical and electronic properties. Specifically, we can tailor the InP core-shell QDs to a type-I, quasi-type-II, or type-II bandgap structure with emission wavelengths ranging from 500-1300 nm depending on the shell material used (ZnS, ZnSe, CdS, or CdSe) and the thickness of the shell. Single molecule microscopy assessments of photobleaching and blinking are used to correlate NQD properties with shell thickness.

36 MATERIALS SCIENCE↗

Liquid crystal device and method thereof

The invention provides a liquid crystal device and method thereof. Subsequent to applying a first electrical voltage on a liquid crystal to induce a reorientation of the liquid crystal, a second electrical voltage with proper polarity is applied on the liquid crystal to assist the relaxation of the reorientation that was induced by the first electrical voltage. The "switch-off" phase of the liquid crystal can therefore be accelerated or temporally shortened, and the device can exhibit better performance such as fast response to on/off signals. The invention can be widely used LCD, LC shutter, LC lens, spatial light modulator, telecommunication device, tunable filter, beam steering device, and electrically driven LC device, among others.

47 OTHER INSTRUMENTATION↗

Communication Simulations for Power System Applications

New smart grid technologies and concepts, such as dynamic pricing, demand response, dynamic state estimation, and wide area monitoring, protection, and control, are expected to require considerable communication resources. As the cost of retrofit can be high, future power grids will require the integration of high-speed, secure connections with legacy communication systems, while still providing adequate system control and security. While considerable work has been performed to create co-simulators for the power domain with load models and market operations, limited work has been performed in integrating communications directly into a power domain solver. The simulation of communication and power systems will become more important as the two systems become more inter-related. This paper will discuss ongoing work at Pacific Northwest National Laboratory to create a flexible, high-speed power and communication system co-simulator for smart grid applications. The framework for the software will be described, including architecture considerations for modular, high performance computing and large-scale scalability (serialization, load balancing, partitioning, cross-platform support, etc.). The current simulator supports the ns-3 (telecommunications) and GridLAB-D (distribution systems) simulators. Ongoing and future work will be described, including planned future expansions for a traditional transmission solver. A test case using the co-simulator, utilizing a transactive demand response system created for the Olympic Peninsula and AEP gridSMART demonstrations, requiring two-way communication between distributed and centralized market devices, will be used to demonstrate the value and intended purpose of the co-simulation environment.

co-simulation↗