Johns Hopkins University Applied Physics Laboratory Research Articles

Abstracts of the 2023 49th Annual NATAS Conference.

We are pleased to announce that the 49th annual meeting of NATAS cwill be held in Rockville, MD, a beautiful city that is part of the Washington D.C. National Capital Area, on the DC metro system (allowing easy access to Washington museums and sites), and close to the National Institute of Standards and Technology (NIST), National Institutes of Health (NIH), Naval Research Laboratory (NRL), Army Research Laboratory (ARL), Johns Hopkins University Applied Physics Laboratory (JHU-APL), Naval Surface Warfare Center (NSWC), Georgetown University, George Washington University, George Mason University, and the University of Maryland. The North American Thermal Analysis Society is a venerable organization that offers scientists and practitioners the opportunity to explore the frontiers of thermal analysis, rheology, and materials characterization. The NATAS meeting always features new developments in the science of thermal analysis as well as applications of these techniques in a wide variety of fields. The meeting includes exhibits from vendors allowing for personalized attention and connecting with providers of instrumentation and software related to thermal analysis. The Society appreciates the financial support of the following contributing sponsors this year: NIST, Mettler-Toledo, TA Instruments, SETARAM, Anton Paar USA, MDPI AG, TAFDV, and QΔT Lab. Exhibitors include AKTS SA, Anton Paar USA, Mettler-Toledo, McCrone Microscopes & Accessories, NETZSCH Instruments North America, TA Instruments, and Thermtest, Inc.

Building Electronic Disease Surveillance Capacity in the Peruvian Navy with SAGES

ObjectiveTo introduce SMS-based data collection into the Peruvian Navy’s public health surveillance system for increased reporting rates and timeliness, particularly from remote areas, as well as improve capabilities for analysis of surveillance data by decision makers.IntroductionIn the past 15 years, public health surveillance has undergone a revolution driven by advances in information technology (IT) with vast improvements in the collection, analysis, visualization, and reporting of health data. Mobile technologies and open source software have played a key role in advancing surveillance techniques, particularly in resource-limited settings. Johns Hopkins University Applied Physics Laboratory (JHU/APL) is an internationally recognized leader in the area of electronic disease surveillance. In addition to the Electronic Surveillance System for the Early Notification of Community-based Epidemics (ESSENCE) used by several state and local jurisdictions and the CDC in the U.S., JHU/APL has also developed the Suite for Automated Global Electronic bioSurveillance (SAGES). SAGES is a collection of modular, open-source software tools designed to meet the challenges of electronic disease surveillance in resource-limited settings.JHU/APL is working with the Peruvian Navy health system to improve their electronic disease surveillance capabilities. The Peruvian Navy currently uses a SAGES-based system called Alerta DISAMAR that was implemented several years ago in an effort supported by the Armed Forces Health Surveillance Branch, and in collaboration with the Naval Medical Research Unit No. 6 (NAMRU-6). The system uses both web-based and IVR-based (interactive voice response) data collection from several Navy health facilities in Peru. For the present effort, JHU/APL is implementing a new SMS-based data collection capability for the Peruvian Navy.MethodsJHU/APL is engaged with the Peruvian Navy Health System to upgrade the existing SAGES-based Alerta DISAMAR surveillance system which relies on remote data collection using IVR (interactive voice recording) technology, with a SAGES-based system that uses SMS (short message service) text messages for remote data collection. Based on Peruvian Navy requirements, JHU/APL created mobile data entry forms for Android smartphones using the SAGES mCollect application. SAGES mCollect is built using Open Data Kit open source tools along with added features such as 128-bit encryption and quality checks.The JHU/APL team engages closely with end users and other stakeholders to determine system requirements and to deploy the system, as well as to train end users and the system administrators who will need to maintain the system once it is deployed. The JHU/APL team, consisting of both information technology and public health expertise, conduct a country-level capabilities and needs assessment to address design considerations and operational end user requirements. This assessment takes into account the requirements and objectives of the Peruvian Navy, while keeping in mind infrastructure, cost, and personnel constraints. A pilot test of SMS-based data collection is currently underway with 10 health clinics within the Navy.ResultsMany challenges exist when implementing electronic disease surveillance tools in resource-limited settings, but using a tailored approach to implementation in which specific needs, constraints, and expectations are identified with stakeholders helps increase the overall adoption and sustainment of the system. JHU/APL believes SMS-based data collection will be more sustainable than IVR-based data collection for the Peruvian Navy.ConclusionsJHU/APL is deploying a SAGES-based electronic disease surveillance system for the Peruvian Navy that has great potential to increase reporting rates from its health facilities as well as improve data quality and timeliness, thus resulting in greater awareness and enhanced public health decision making. 

ESSENCE Features for 2019

ObjectiveThe objective of this presentation is to discuss the new features that are under development for ESSENCE in 2019. This is a chance to describe the features, the use cases for the features, and open a dialogue with the community on potential new enhancements that are available.IntroductionThe ESSENCE system is a community-driven disease surveillance system. Installed in over 25 jurisdictions across the US, the system is built on a single codebase that is shared across all instances. While each individual location can customize many of the settings, data sources, and configurations, the underlying code and functionality is shared. This means that when one jurisdiction works with the Johns Hopkins University Applied Physics Laboratory (JHU/APL) to create a new feature, it is available to all sites.MethodsThe roadmap for ESSENCE in 2019 is based upon ongoing and future projects between jurisdictions and JHU/APL. While specifics can change before features are deployed, the following list of new features have exceptional capabilities. These include:Social Elements to the User Experience: Ability for users to share what they are doing within ESSENCE with their peers. Ability for users to see what others are querying and find interesting. Support sharing both within a system and across jurisdictions.Text Analysis: Text analysis and visualizations to help support the user in building new free-text queries.Provide correlation, trend, and association analytics for words and phrases to help the user determine what should or should not be included in their queries.Site Monitoring: Back-end tools and checks to better monitor an ESSENCE system for issues and data irregularities. This administrative tool will help the system maintain its day-to-day availability and improve visibility of errors and issues that may develop over time.Longitudinal Surveillance: Visualizations and cohort clustering analytics to determine the types of patients who are using the healthcare systems that provide data to ESSENCE. These tools can show patient uses over time with trends to better inform utilization of healthcare resources in a community.Opioid Overdose Surveillance: Visualizations and analytics to better support the surveillance activities related to the opioid overdose crisis. Work with additional data sources (EMS, Poison Control, Death Records, etc.) to determine the benefit of fusing multiple pieces of information into a common picture for improved opioid surveillance.And other new features…ResultsThe presentation will describe the current roadmap, demonstrate features that are mature enough in the software development process, share mock-ups for features still in the early stages of development and provide use cases for each of the new features discussed.ConclusionsNo organization can build a successful system without the participation and buy-in from its stakeholder community. ESSENCE is an excellent example of a tool built on collective input whose ongoing enhancements benefit all its users. By seeing the roadmap and understanding the new features for 2019, the community can prepare for upcoming enhancements and begin discussions about other needs and use cases that will drive the development of the next round of ESSENCE features. 

What Can You Really Do with 35,000 Statistical Alerts a Week Anyways?

ObjectiveFind practical ways to sort through statistical noise in syndromic data and make use of alerts most likely to have public health importance.IntroductionThe National Syndromic Surveillance Program’s (NSSP) instance of ESSENCE* in the BioSense Platform generates about 35,000 statistical alerts each week. Local ESSENCE instances can generate as many as 5,000 statistical alerts each week. While some states have well-coordinated processes for delegating data and statistical alerts to local public health jurisdictions for review, many do not have adequate resources. By design, statistical alerts should indicate potential clusters that warrant a syndromic surveillance practitioner‘s time and focus. However, practitioners frequently ignore statistical alerts altogether because of the overwhelming volume of data and alerts. In 2008, staff in the Virginia Department of Health experimented with rules that could be used to rank the statistical output generated in ESSENCE alert lists. Results were shared with Johns Hopkins University Applied Physics Lab (JHU/APL), the developer of ESSENCE, and were early inputs into what is now known as “myAlerts,” an ESSENCE function that syndromic surveillance practitioners can use to customize alerting and sort through statistical noise. NSSP–ESSENCE produces a shared alert list by syndrome, county, and age-group strata, which generates an unwieldy but rich data set that can be studied to learn more about the importance of these statistical alerts. Ultimately, guidance can be developed to help syndromic surveillance practitioners set up meaningful ESSENCE myAlerts effective in identifying clusters with public health importance.MethodsThe region/syndrome alert list generated from NSSP’s instance of ESSENCE on the BioSense Platform was downloaded and ranked based on five criteria:1. Observed count causing the alert2. Expected count generated by ESSENCE3. Total number of alerts for that syndrome in that county and number of prior alerts during that week for the same syndrome, county, and age group4. Density of alerts during the prior week5. Recency of the latest alertAlerts were then ranked based on:1. Higher absolute counts (regardless of expected value)2. Higher partial chi-square, (Obs-Exp)2 / Exp3. Higher total alerts for a given county/syndrome4. Higher number of earlier alerts for same county/syndrome/age group5. Multiple alerts same day > alerts on consecutive days > alerts separated by days without alerts6. Alerts present on more recent daysThe top 20 alerts with the highest scores were then reviewed and if anything unusual was noticed (i.e. problems unrelated to recent data quality problems or onboardings, seasonal trends, etc.) then there was follow-up with the site. The alert list rankings were then evaluated for differences among factors available in the ESSENCE myAlert function. We compared the top 5% of ranked alerts to the remaining 95% to determine if there were significant differences in the following factors:1. Total number of alerts across six age groups (including all ages) within 8 days of each syndrome and county stratum;2. Average alert frequency across six age groups (including all ages) within 8 days for each stratum;3. Average count across the strata;4. Average expected value across the strata;5. Average of the difference between the count and expected values for each stratum; and6. Average Level across the strata.ResultsPreliminary interactions with sites revealed important clusters – some already known and some not. For example, a cluster of healthcare workers exposed to Neisseria meningitides, and kids exposed to a bat at summer camp and presenting for prophylaxis were among the clusters identified. Additionally there were differences seen in the adjustable myAlert parameters when comparing the top 5% to the lower 95% of ranked alerts.ConclusionsThe differences seen and preliminary feedback suggests that this ranking method may be effective in identifying alerts representing true clusters of public health importance. Testing designed to evaluate myAlert parameters based on the differences seen in the top 5% of ranked alerts is underway in sites where more detailed data access is available. More study is needed; however, there are indications that cutoff values for these parameters may be a valuable way for syndromic surveillance practitioners to reduce the review burden and focus on the most important statistical clusters identified by ESSENCE statistical algorithms.References*ESSENCE stands for the Electronic Surveillance System for the Early Notification of Community-based Epidemics and is designed by Johns Hopkins University Applied Physics Laboratory.

Advances in planetary defense in the United States

The National Aeronautics and Space Administration (NASA) recently established an office to manage the Agency's planetary defense-related projects and coordinate activities across multiple U.S. agencies as well as with international efforts to plan appropriate responses to the potential asteroid impact hazard. The creation of the Planetary Defense Coordination Office (PDCO) is a logical and formal step forward with NASA's NEO Observations program which began nearly two decades ago. Since the program's inception in 1998, NASA-funded efforts have discovered more than 98% of the more than 16,000 NEOs currently known.As important as it is to mitigate a potential impact event, the essential first step is to find these near-Earth objects as early as possible. To that end, NASA's PDCO leads national and international efforts to:•detect any potential for significant impact of the Earth by natural objects;•appraise the range of potential effects by any possible object; and•develop strategies to mitigate impact effects on human welfare.Since commencing the program in 1998, NASA has provided funding to upgrade and operate existing 1-m class telescopes to conduct the search for NEOs. Today, NASA funds three primary ground-based survey capabilities: the Lincoln Near-Earth Asteroid Research (LINEAR) project, the Catalina Sky Survey (CSS), and the Panoramic Survey Telescope and Rapid Reporting System (Pan-STARRS). Recent enhancements to NASA's Near-Earth Object (NEO) Observations Program have led to ∼83% increase in the discovery rate of near-Earth asteroids (NEAs) over the past three years.These survey efforts are increasingly detecting close encounter events (i.e., <0.001 AU; recent examples include 2012 DA14, 2017 EA, and 2017 GM) and have enabled the prediction of some small object impact events (e.g., 2008 TC3 and 2014 AA). Such encounters provide opportunities for NASA's Infrared Telescope Facility (IRTF) to make spectral measurements; or observation by planetary radars at Arecibo and Goldstone to refine the orbit of the object with great precision and even “image” the small primitive body.Of critical importance is the Minor Planet Center (MPC), where automated systems process observations made by the search teams to determine orbits and what are NEOs. The Center for NEO Studies at the Jet Propulsion Laboratory (JPL) determines more precise orbits for the objects. Both JPL and the MPC utilize processes and procedures for NEO orbit determination and prediction that are sanctioned and monitored by the International Astronomical Union (IAU) and produce data catalogues on small bodies in the Solar System that are utilized world-wide by the astronomical community.The Wide-field Infrared Survey Explorer (WISE) was reactivated for the purpose detecting NEOs and will continue to operate well into 2018. It is in Sun-synchronous, near-polar inclination (97.5°) orbit around the Earth. The NEOWISE project uses WISE in ‘warm mode’ (at 3.4 and 4.6 μm), and in conjunction with ground-based follow-up, this unique dataset has set limits on population statistics, orbital parameters, approximate sizes, and initial compositional knowledge of the asteroid population.Further follow-up observations with visible and infrared telescopes (e.g., NASA's Infrared Telescope Facility, Spitzer Space Telescope, other NASA-funded NEO observer teams) refine the astrometric positions of an NEO, photometric observations obtain detailed light curve information [thereby constraining NEO shapes and spin state], and collect albedo and spectral data on basic physical properties and mineralogy.Planetary defense demonstration missions also fall within the purview of the PDCO. The Double Asteroid Redirection Test (DART) mission is directed by NASA to the Johns Hopkins University Applied Physics Laboratory (JHU/APL). The target is the binary near-Earth asteroid (65803) Didymos, which consists of a primary body ∼800 m across, and a secondary body (or “moonlet”) whose 150-m size is more typical of the size of asteroids that could pose a more common hazard to Earth.However, the first step in planetary defense is the overarching goal to complete the NEO survey down to a 100 m-sized objects. The asteroid hunter mission – NEOCam – is a single scientific instrument: 0.5-m aperture infrared telescope that would survey the solar system for NEOs from Sun-Earth L1 Lagrange point (SEL1). NEOCam is also in an extended Phase A study under the auspices of NASA's PDCO.

Lidar measurements of solid rocket propellant fire particle plumes.

This paper presents the first, to our knowledge, direct measurement of aerosol produced by an aluminized solid rocket propellant (SRP) fire on the ground. Such fires produce aluminum oxide particles small enough to loft high into the atmosphere and disperse over a wide area. These results can be applied to spacecraft launchpad accidents that expose spacecraft to such fires; during these fires, there is concern that some of the plutonium from the spacecraft power system will be carried with the aerosols. Accident-related lofting of this material would be the net result of many contributing processes that are currently being evaluated. To resolve the complexity of fire processes, a self-consistent model of the ground-level and upper-level parts of the plume was determined by merging ground-level optical measurements of the fire with lidar measurements of the aerosol plume at height during a series of SRP fire tests that simulated propellant fire accident scenarios. On the basis of the measurements and model results, the Johns Hopkins University Applied Physics Laboratory (JHU/APL) team was able to estimate the amount of aluminum oxide (alumina) lofted into the atmosphere above the fire. The quantification of this ratio is critical for a complete understanding of accident scenarios, because contaminants are transported through the plume. This paper provides an estimate for the mass of alumina lofted into the air.

In-flight performance of the Van Allen Probes RF telecommunications system

The NASA Van Allen Probes mission (previously called the Radiation Belt Storm Probes) successfully launched on 30 August 2012. The twin spacecraft, designed, built, and operated by The Johns Hopkins University Applied Physics Laboratory (JHU/APL), has been successfully operating within Earth׳s radiation belts since then, returning critical science data revealing new insights into the physics of the radiation belts. Because of the extreme radiation environment, all spacecraft subsystems including the communications system had to make special accommodations to withstand the effects of the radiation.Each Van Allen Probes spacecraft׳s telecommunications system includes an S-band version of the Frontier Radio, a solid-state power amplifier, RF routing components, and dual low-gain antennas. This mission marks the first flight of the Frontier Radio, which is baselined for use in the upcoming Solar Probe Plus and Europa Clipper missions. This paper will present an overview of the as-built telecommunications system and its ground station interfaces discuss key communications flight hardware components, and then discuss in detail its activities and performance in-flight, including the launch and commissioning operations, performance enhancements since launch, and performance trending in flight. Pre-launch preparations at the APL 18-m ground station revealed occasional RF interference that could disrupt Van Allen Probe downlink. A monitoring system was installed to help mitigate some interference sources, and to characterize the residual environment and show that RF interference was not a mission risk. Post-launch commissioning activities were driven by the requirement to verify both spacecraft׳s communication systems over multiple ground networks, including JHU/APL׳s own 18-m ground station, the Universal Space Network, and TDRSS. Enhanced science data downlink volume was enabled by expanding the usable field of view of the spacecrafts׳ antennas once in-flight calibrations of the antenna patterns were completed, as well as reducing downlink link margins to a bare minimum when downlinking via APL׳s 18-m dish, where the CFDP (CCSDS File Delivery Protocol) is used to guarantee file delivery. Radiation drove some of the hardware design; the radios have experienced several predicted fault conditions at the predicted rates and have reacted autonomously as designed to minimize impact to the science downlink.

Underwater acoustics at the Johns Hopkins University Applied Physics Lab

The Johns Hopkins University Applied Physics Lab (JHU/APL) was founded in 1942. JHU/APL began research in underwater acoustics in 1970 and became known for full scale ocean testing. JHU/APL developed the first technique to accurately measure the shape of a towed array. Towed array testing culminated in 1991–1992 with the deployment of a 5 km aperture measuring signal coherence and beam noise statistics in the Pacific, Atlantic, and Mediterranean. In 1982, JHU/APL began investigations into low frequency (LF) active sonar. Initially, airguns and explosives were employed to measure bottom and surface scattering strengths. Then, tests with a stationary controlled source were conducted from 1986–1989, activating both stationary and towed receiver arrays. In 1989, JHU/APL outfitted the Cory Chouest, adding a two story back deck superstructure. The lower level housed a three aperture LF source array and long towed receiver array, while the upper story berthed 50 scientists and engineers. This ship conducted a series of measurements of scattering strengths of the ocean surface, bottom and volume from 200–1000 Hz. Today JHU/APL employs 5000 staff of which about 150 are scientists and engineers working in underwater acoustics. Studies have expanded from LF beginnings to the full spectrum of acoustic frequencies.

Simultaneous Neural Control of Simple Reaching and Grasping With the Modular Prosthetic Limb Using Intracranial EEG

Intracranial electroencephalographic (iEEG) signals from two human subjects were used to achieve simultaneous neural control of reaching and grasping movements with the Johns Hopkins University Applied Physics Lab (JHU/APL) Modular Prosthetic Limb (MPL), a dexterous robotic prosthetic arm. We performed functional mapping of high gamma activity while the subject made reaching and grasping movements to identify task-selective electrodes. Independent, online control of reaching and grasping was then achieved using high gamma activity from a small subset of electrodes with a model trained on short blocks of reaching and grasping with no further adaptation. Classification accuracy did not decline (p < 0.05, one-way ANOVA) over three blocks of testing in either subject. Mean classification accuracy during independently executed overt reach and grasp movements for (Subject 1, Subject 2) were (0.85, 0.81) and (0.80, 0.96), respectively, and during simultaneous execution they were (0.83, 0.88) and (0.58, 0.88), respectively. Our models leveraged knowledge of the subject's individual functional neuroanatomy for reaching and grasping movements, allowing rapid acquisition of control in a time-sensitive clinical setting. We demonstrate the potential feasibility of verifying functionally meaningful iEEG-based control of the MPL prior to chronic implantation, during which additional capabilities of the MPL might be exploited with further training.

Improved cost monitoring and control through the Earned Value Management System

As economic pressure and competition for budget among federal agencies has increased, there has been an increasing need for more granular data and robust management information systems. This is especially true for the execution of major civilian space programs. This need has resulted in new program management requirements being implemented in an attempt to limit cost and schedule growth. In particular, NASA Procedural Requirements (NPR) 7120.5D requires the implementation of an Earned Value Management System (EVMS) compliant with the requirements of American National Standards Institute (ANSI)/Electronic Industries Alliance Standard 748-B. The Radiation Belt Storm Probes (RBSP) program management team at The Johns Hopkins University Applied Physics Laboratory (JHU/APL) made a decision to implement an EVMS on RBSP during Phase B—a year earlier than specified in the contractual Phase C reporting requirement as defined in the NPR. This decision was made so that the project would have the benefit of 12 months of training and hands-on implementation during Phase B. Although there were a number of technical and process hurdles encountered during Phase B and into Phase C, the system was working well when the Integrated Baseline Review (IBR) was held in August 2009. The IBR was a success because it met the review requirements. It was also clear to all IBR participants that the EVMS was providing value to the project management team. Although the IBR pointed out some areas of concern regarding process and ANSI compliance, the system had markedly improved the project's ability to monitor cost and schedule. This, in turn, allowed the project team to foresee problems in advance, formulate corrective actions, and implement course corrections without causing significant adverse impact to the project. Opponents of EVMS systems often communicate the unfavorable opinion that EVMS systems create unnecessary cost and administration. Although it is undeniable that EVMS implementation does not occur without cost, the cost is minimal in comparison to the benefits of successful implementation. This paper will focus on the implementation of EVMS on the RBSP project, explain EV processes and the implementation's cost, and analyze the benefits of EVMS to provide insight into cost/benefit considerations for other projects considering EVMS implementation. This paper will do this by focusing on the following points: (1) RBSP is the first full-up implementation of earned value management (EVM) at JHU/APL; (2) RBSP EVM started in Phase B; (3) RBSP EVM implementation has been working well in Phase C/D; (4) RBSP EVM implementation has been recognized by Goddard Space Flight Center and NASA Headquarters as successful; and (5) an assessment of the benefits of EVMS to the project management team and sponsor shows that the system's benefits outweigh the cost of implementation.

Toward Electrocorticographic Control of a Dexterous Upper Limb Prosthesis: Building Brain-Machine Interfaces

One of the most exciting and compelling areas of research and development is building brain machine interfaces (BMIs) for controlling prosthetic limbs. Prosthetic limb technology is advancing rapidly, and the modular prosthetic limb (MPL) of the Johns Hopkins University/ Applied Physics Laboratory (JHU/APL) permits actuation with 17 degrees of freedom in 26 articulating joints. There are many signals from the brain that can be leveraged, including the spiking rates of neurons in the cortex, electrocorticographic (ECoG) signals from the surface of the cortex, and electroencephalographic (EEG) signals from the scalp. Unlike microelectrodes that record spikes, ECoG does not penetrate the cortex and has a higher spatial specificity, signal-to-noise ratio, and bandwidth than EEG signals. We have implemented an ECoG-based system for controlling the MPL in the Johns Hopkins Hospital Epilepsy Monitoring Unit, where patients are implanted with ECoG electrode grids for clinical seizure mapping and asked to perform various recorded finger or grasp movements. We have shown that low-frequency local motor potentials (LMPs) and ECoG power in the high gamma frequency (70,150 Hz) range correlate well with grasping parameters, and they stand out as good candidate features for closed-loop control of the MPL.

The challenges of designing a lightweight spacecraft structure for landing on the lunar surface

The Johns Hopkins University Applied Physics Laboratory (JHU/APL) has been working with NASA's Marshall Space Flight Center (MSFC) on a lunar lander design that would take scientific measurements on the surface of the moon. This effort is part of NASA's Robotic Lunar Lander (RLL) Development Project. The requirements imposed on the design of the lander are: (1) Provide a lightweight lander structure to minimize the launch costs and maximize the payload carrying capability, (2) Minimize the lander launch envelope to allow for launching multiple landers on a single launch vehicle, (3) Given specific approach velocities, design a lander with geometric properties (low center-of-gravity, etc.) that maximizes the chances for a controlled landing on the lunar surface, (4) Provide a stable platform for all of the various scientific instruments. The lightweight lander requirement originates from the desire to minimize the launch costs and possibly package multiple landers on a single launch vehicle. The use of lightweight composite materials and advanced manufacturing techniques are employed throughout the design and construction of the structure in order to minimize mass and maximize structural stiffness. Minimizing the launch envelope enables the potential packaging of several spacecraft into one launch vehicle shroud. By having multiple landers, the scientific return is enhanced. Multiple spacecraft on the lunar surface provides independent confirmation of science measurements taken and also highlights any variance in the science data taken at differing lunar latitudes. Naturally, the launch cost per lander is greatly reduced if more than one lander can be packaged on a single launch vehicle. The lunar lander vehicle must arrive at the lunar surface at an upright orientation. In order to accomplish this, the structure geometry must be designed to accommodate attitude errors in roll, pitch and yaw. In addition, the structure must be able to withstand various landing scenarios, which include a wide range of landing velocities, decelerations and attitude rates. The stability requirement is dictated by the nature of the instrument suite. Many of the measurements to be taken on the lunar surface are so sensitive that any mechanical disturbances could potentially corrupt the measured data. Mechanical disturbances such as operating mechanisms, thermal expansion/contraction, deployable booms or other devices must be minimized. It is imperative that all of the structural requirements are met for this mission. Failure to meet any of the numerous challenging requirements could cause the loss of all the scientific objectives.

Developing Young Space System Engineers

At a fundamental level, system engineering is the process by which engineering efforts are communicated, controlled, and organized on complex projects. The engineers who perform this work well are able to work across multiple engineering and managerial disciplines. They require outstanding technical, personal, management, and communications skills and an ability, based on experience, to work in areas where clean decisions are not possible. Furthermore, within the Space Department (SD) at the Johns Hopkins University - Applied Physics Laboratory (JHU/APL), lead system engineers are delegated responsibility for leading the development of the technical baselines and ensuring their performance robustly meets requirements. Success in these areas requires a level of capability and maturity that can only be developed through time and experience. With such a high bar being set, the question: “How does one develop high-caliber system engineers?” becomes difficult to answer. Within the JHU/APL SD, prior to 2006, the primary means of attaining system engineers were through hiring experienced staff from external organizations or moving interested and capable staff from other areas of the department. This situation creates two problems within a growing organization. First, potential staff with the credentials stated above is extremely difficult to find, making it difficult for a system engineering organization to grow in the face of attrition. Second, the demographics of a system engineering organization become skewed toward older staff, limiting the organization's access to new methodologies, alternative means of collaboration, linkages to the university system and (frankly) youthful energy, to name a few. To address this need, management within the department developed a program for developing newly minted Masters Graduates. Key to this program is the recognition that system engineering is a process for communicating and organizing the work associated with the development and production of a specific product which is not an end to itself. As such, providing experience in both system engineering and the product-focused disciplines necessary for developing, integrating or operating space systems is critical. This describes the impetus for developing the Young Space Systems Engineers Program, key program features, problems encountered during development, and the program's successes. A strong case is made for the necessity for system engineers to understand the system engineering process and the product they produce, as well as the human element that goes into making it.

The Collaborative Experience of Creating the National Capital Region Disease Surveillance Network

The Johns Hopkins University Applied Physics Laboratory (JHU/APL) implemented state and district surveillance nodes in a central aggregated node in the National Capital Region (NCR). Within this network, de-identified health information is integrated with other indicator data and is made available to local and state health departments for enhanced disease surveillance. Aggregated data made available to the central node enable public health practitioners to observe abnormal behavior of health indicators spanning jurisdictions and view geographical spread of outbreaks across regions.Forming a steering committee, the NCR Enhanced Surveillance Operating Group (ESOG), was key to overcoming several data-sharing issues. The committee was composed of epidemiologists and key public health practitioners from the 3 jurisdictions. The ESOG facilitated early system development and signing of the cross-jurisdictional data-sharing agreement. This agreement was the first of its kind at the time and provided the legal foundation for sharing aggregated health information across state/district boundaries for electronic disease surveillance.Electronic surveillance system for the early notification of community-based epidemics provides NCR users with a comprehensive regional view to ascertain the spread of disease, estimate resource needs, and implement control measures. This article aims to describe the creation of the NCR Disease Surveillance Network as an exceptional example of cooperation and potential that exists for regional surveillance activities.

First Spacecraft Orbit of Mercury

After a 7.9‐billion‐kilometer flight since its launch on 3 August 2004—which included flybys of Earth, Venus, and Mercury—NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft entered a planned, highly elliptical orbit around the closest planet to our Sun on 17 March. Engineers in the mission operations center at the Johns Hopkins University Applied Physics Laboratory (JHU/APL) in Laurel, Md., which manages the mission for NASA, received radiometric signals indicating a successful orbit insertion at 9:10 P.M. local time. “Tonight we will have orbited the fifth planet in the solar system. This is a major accomplishment,” Ed Weiler, NASA assistant administrator for the Science Mission Directorate, said at a 17 March public forum at JHU/APL, noting that spacecraft have previously entered orbit around several other planets. “You only go into orbit for the first time around Mercury once in human history, and that is what was accomplished tonight.”

Analysis of flow distribution from high-speed flow actuator using particle image velocimetry and digital speckle tomography

A variety of active flow control (AFC) methods are typically used in low-speed applications; however, the AFC techniques that are available for high-speed, supersonic applications are very limited. Under AFOSR (Air Force Research Laboratory) sponsorship, The Johns Hopkins University Applied Physics Laboratory (JHU/APL) is investigating a device that is intended for high-speed flow control; it is called the SparkJet actuator, which manipulates high-speed flows without active mechanical components. To date, actuator characterization has included computational and experimental techniques including parametric studies and flow visualization techniques to investigate the operation of the SparkJet device under various conditions. This paper focuses on the experimental flow measurement techniques that have been implemented. The results will be used for validating prospective computational studies that investigate the detailed characteristics of the SparkJet’s discharge and cooling stages after an energy deposition pulse. Current efforts include the use of high- resolution particle image velocimetry (PIV) to quantify the quiescent air operation of a single SparkJet pulse. However, the proper seeding of the SparkJet cavity continues to be challenging and has led to the use of digital speckle tomography (DST) to measure the temperature distribution in the core of the SparkJet plume. In this study, improved PIV techniques were used to acquire a higher-resolution image of the SparkJet-entrained flow. These PIV results show that the peak velocity in the entrained flow is around 53 m/s and the plume is sustained for 75–100 μs. Additionally, the DST data show a peak temperature of 1616.3 K at 75 μs and provide supporting information for interpreting the PIV data. These results are intended to calibrate and build confidence in a computational model.

Connecting research and practice: an experience report on research infusion with software architecture visualization and evaluation

There are many technical challenges in ensuring high life-time quality of NASA's systems. Some of NASA's software-related challenges could potentially be addressed by the many powerful technologies that are being developed in software research laboratories. However, most such research technologies do not make the transition from the research lab to the software lab because research infusion and technology transfer is difficult. For example, there must be evidence that the technology works in the practitioner's particular domain, and there must be a potential for great improvements and enhanced competitive edge for the practitioner, for such infusion to take place. NASA IV&V's Research Infusion initiative strives to facilitate such infusion. In 2006, a research infusion project involving Johns Hopkins University Applied Physics Laboratory (JHU/APL) and the Fraunhofer Center for Experimental Software Engineering Maryland, was successfully completed infusing Fraunhofer's software architecture visualization and evaluation (SAVE) tool. The infusion project helped improve JHU/APL's software architecture and produced evidence that SAVE is applicable to software architecture problems in the aerospace domain, spawning a series of related research infusion projects. The project also led to the discovery of other needs that could not be addressed by current technologies and, therefore, spawned the research and development of a new technology that will be ready for infusion in the future. This paper describes the SAVE technology followed by a description of the infusion of SAVE at JHU/APL and the other projects that followed, as well as the newly started Dynamic SAVE research and development project. Lessons learned related to various aspects of research infusion conclude the paper.

VHF General Urban Path Loss Model for Short Range Ground-to-Ground Communications

From a radio frequency propagation perspective, the general focus of the commercial wireless communications community has been primarily on frequencies above 800 MHz. Therefore, there is a limited number of available empirical data and validated prediction methods indicating what type of path loss or signal degradation one should expect in various urban settings at a very high frequency (VHF) range, which is the range of operation for numerous military tactical communications systems. Furthermore, the extensive literature survey revealed that indoor propagation models are particularly lacking in either availability and/or proven fidelity. This paper presents a new general urban path loss model derived from a log-distance path loss model, floor attenuation factor model and path loss measurements taken on campus of The Johns Hopkins University Applied Physics Laboratory (JHU/APL), Laurel, MD, with a measurement hardware suite in 30-88 MHz frequency range. The authors felt that there is a void in the open literature on simple, empirically-verified large-scale path loss models that implicitly address the lower VHF range, more than one urban setting, short communications ranges (<1 km) and low transmitting and receiving antenna heights as well as offer reasonably high fidelity without requiring a lot of information about the site.

The STEREO Observatory

The Solar Terrestrial Relations Observatory (STEREO) is the third mission in NASA’s Solar Terrestrial Probes program. The mission is managed by the Goddard Space Flight Center (GSFC) and implemented by The Johns Hopkins University Applied Physics Laboratory (JHU/APL). This two-year mission provides a unique and revolutionary view of the Sun–Earth system. Consisting of two nearly identical observatories, one ahead of Earth in its orbit around the Sun and the other trailing behind the Earth, the spacecraft trace the flow of energy and matter from the Sun to Earth and reveal the three-dimensional structure of coronal mass ejections (CMEs) to help explain their genesis and propagation. From its unique side-viewing vantage point, STEREO also provides alerts for Earth-directed solar ejections. These alerts are broadcast at all times and received either by NASA’s Deep Space Network (DSN) or by various space-weather partners.

Launch and Early Operation of the MESSENGER Mission

On August 3, 2004, at 2:15 a.m. EST, the MESSENGER mission to Mercury began with liftoff of the Delta II 7925H launch vehicle and 1,107-kg spacecraft including seven instruments. MESSENGER is the seventh in the series of NASA Discovery missions, the third to be built and operated by The Johns Hopkins University Applied Physics Laboratory (JHU/APL) following the Near Earth Asteroid Rendezvous (NEAR) Shoemaker and Comet Nucleus Tour (CONTOUR) missions. The MESSENGER team at JHU/APL is using efficient operations approaches developed in support of the low-cost NEAR and CONTOUR operations while incorporating improved approaches for reducing total mission risk. This paper provides an overview of the designs and operational practices implemented to conduct the MESSENGER mission safely and effectively. These practices include proven approaches used on past JHU/APL operations and new improvements implemented to reduce risk, including adherence to time-proven standards of conduct in the planning and implementation of the mission. This paper also discusses the unique challenges of operating in orbit around Mercury, the closest planet to the Sun, and what specific measures are being taken to address those challenges.