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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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The GLAST Burst Monitor (GBM) will detect and localize bursts for the GLAST mission, and provide the spectral and temporal context in the traditional 10 keV to 25 MeV band for the high energy observations by the Large Area Telescope (LAT). The GBM will use traditional rate triggers in up to three energy bands, and on a variety of timescales between 16 ms and 16 s.
We use spatially continuous satellite data as a correlate of precipitation within tropical Africa and show that the majority of documented Ebola hemorrhagic fever outbreaks were closely associated with sharply drier conditions at the end of the rainy season. We propose that these trigger events may enhance transmission of Ebola virus from its cryptic reservoir to humans. These findings suggest specific directions to help understand the sylvatic cycle of the virus and may provide early warning tools to detect possible future outbreaks of this enigmatic disease.
We use WIND solar wind data and POLAR UV imaging data to study magnetospheric responses and suibstorm triggering mechanisms during and after interplanetary (IP) shock events.
We use WIND solar wind data a POLAR UV imaging data to study magnetospheric responses and substorm triggering mechanisms during and after interplanetary (IP) shock events.
Traditional avionics computing systems are federated, with each system provided on a number of dedicated hardware units. Federated applications are physically separated from one another and analysis of the systems is undertaken individually. Integrated Modular Avionics (IMA) takes these federated functions and integrates them on a common computing platform in a tightly deterministic distributed real-time network of computing modules in which the different applications can run. IMA supports different levels of criticality in the same computing resource and provides a platform for implementation of fault tolerance through hardware and application redundancy. Modular implementation has distinct benefits in design, testing and system maintainability. This paper covers the requirements for fault tolerant bus systems used to provide reliable communication between IMA computing modules. An overview of the Time Triggered Protocol (TTP) specification and implementation as a reliable solution for IMA systems is presented. Application examples in aircraft avionics and a development system for future space application are covered. The commercially available TTP controller can be also be implemented in an FPGA and the results from implementation studies are covered. Finally future direction for the application of TTP and related development activities are presented.
This viewgraph presentation is a review of the Time Triggered Protocol, designed to work with NASA's Integrated Safety-Critical Advanced Avionics Communication and Control (ISAACC) system. ISAACC is the product of the Propulsion High-Impact Avionics Technologies (PHIAT) project at NASA Marshall Space Flight Center (MSFC) during FY03 to the end of FY05. The goal is an avionics architecture suitable for control and monitoring of safety critical systems of manned spacecraft. It must be scalable to allow its use in robotic vehicles or launch pad and propulsion test stand monitoring and control systems. The developed IMA should have: a common power supply and rugged chassis for a set of modules, many upgradeable software functions on one module (i.e. processing unit Reduced weight, straightforward update and system integration. It is also important that it have Partitioning and a Memory Management Unit (MMU)
I describe some inconsistencies in John Rushby s axiomatization of time-triggered algorithms that he presents in these transactions and that he formally specifies and verifies in a mechanical theorem-prover. I also present corrections for these inconsistencies.
Three dimensional PIC simulations are performed in order to analyse the dynamics of the magnetotail as the interplanetary magnetic field (IMF) rotates from northward to southward direction. This dynamics reveals to be quite different within meridian/equatorial planes over two successive phases of this rotation. First, as IMF rotates from North to Dawn-Dusk direction, the X-Point (magnetic reconnection) evidenced in the magnetotail (meridian plane) is moving earthward (from x=-35 Re to x=-17.5 ) distance at which it stabilizes. This motion is coupled with the formation of "Crosstail-S" patterns (within the plane perpendicular to the Sun-Earth mine) through the neutral sheet in the nearby magnetotail. Second, as IMF rotates from dawn-dusk to South, the minimum B field region is expanding within the equatorial plane and forms a ring. This two-steps dynamics is analyzed in strong association with the cross field magnetotail current Jy, in order to recover the signatures of substorms triggering.
LIGO is about to begin a new, higher sensitivity science run, where gravitational detection is plausible. A possible candidate for detection is a compact binary merger, which would also be likely to emit a high energy electromagnetic signal. Coincident observation of the gw signal from a compact merger with an x-ray or gamma-ray signal would add considerable weight to the claim for gw detection. In this talk I will consider the possibility of using LIGO triggers with time and sky position to perform a coincident analysis of EM signals from the RXTE, SWIFT, and FERMI missions.
Solar eruptions occur on many different scales. (Schrijver 2010: bipole eruptions more frequent as size decreases.) Trigger might be any of several different candidates, working independently or in tandem. How about larger scales than (solar) CMEs? (Stellar eruptions.) How about smaller scales than X-ray jets? (Spicules? Moore 1989)
A new comprehensive lightning instrumentation system has been designed for Launch Complex 39B (LC3913) at the Kennedy Space Center, Florida. This new instrumentation system includes the synchronized recording of six high-speed video cameras; currents through the nine downconductors of the new lightning protection system for LC3913; four dH/dt, 3-axis measurement stations; and five dE/dt stations composed of two antennas each. A 20:1 scaled down model of the new Lightning Protection System (LPS) of LC39B was built at the International Center for Lightning Research and Testing, Camp Blanding, FL. This scaled down lightning protection system was instrumented with the transient recorders, digitizers, and sensors to be used in the final instrumentation installation at LC3913. The instrumentation used at the ICLRT is also a scaled-down instrumentation of the LC39B instrumentation. The scaled-down LPS was subjected to seven direct lightning strikes and six (four triggered and two natural nearby flashes) in 2010. The following measurements were acquired at the ICLRT: currents through the nine downconductors; two dl-/dt, 3-axis stations, one at the center of the LPS (underneath the catenary wires), and another 40 meters south from the center of the LPS; ten dE/dt stations, nine of them on the perimeter of the LPS and one at the center of the LPS (underneath the catenary wire system); and the incident current. Data from representative events are presented and analyzed in this paper.
A method of measuring the fraction of bacterial spores in a sample that remain viable exploits DPA-triggered luminescence of Tb(3+) and is based partly on the same principles as those described earlier. Unlike prior methods for performing such live/dead assays of bacterial spores, this method does not involve counting colonies formed by cultivation (which can take days), or counting of spores under a microscope, and works whether or not bacterial spores are attached to other small particles (i.e., dust), and can be implemented on a time scale of about 20 minutes.
We present new results related to the verification of the Timed-Triggered Ethernet (TTE) clock synchronization protocol. This work extends previous verification of TTE based on model checking. We identify a suboptimal design choice in a compression function used in clock synchronization, and propose an improvement. We compare the original design and the improved definition using the SAL model checker.
The Orion Multi-Purpose Crew Vehicle (MPCV) will perform a flight test known as Exploration Flight Test-1 (EFT-1) currently scheduled for 2014. One of the primary functions of this test is to exercise all of the important Guidance, Navigation, Control (GN&C), and Propulsion systems, along with the flight software for future flights. The Descent and Landing segment of the flight is governed by the requirements levied on the GN&C system by the Landing and Recovery System (LRS). The LRS is a complex system of parachutes and flight control modes that ensure that the Orion MPCV safely lands at its designated target in the Pacific Ocean. The Descent and Landing segment begins with the jettisoning of the Forward Bay Cover and concludes with sensing touchdown. This paper discusses the requirements, design, testing, analysis and performance of the current EFT-1 Descent and Landing Triggers flight software.
A fiber optic current sensor based on the Faraday Effect is developed that is highly suitable for aircraft installation and can measure total current enclosed in a fiber loop down to DC. Other attributes include being small, light-weight, non-conducting, safe from electromagnetic interference, and free of hysteresis and saturation. The Faraday Effect causes light polarization to rotate when exposed to a magnetic field in the direction of light propagation. Measuring the induced light polarization rotation in fiber loops yields the total current enclosed. Two sensor systems were constructed and installed at Camp Blanding, Florida, measuring rocket-triggered lightning. The systems were similar in design but with different laser wavelengths, sensitivities and ranges. Results are compared to a shunt resistor as reference. The 850nm wavelength system tested in summer 2011 showed good result comparison early. However, later results showed gradual amplitude increase with time, attributed to corroded connections affecting the 50-ohm output termination. The 1550nm system also yielded good results in the summer 2012. The successful measurements demonstrate the fiber optic sensor's accuracies in capturing real lightning currents, and represent an important step toward future aircraft installation.
This paper describes a quantitative methodology for bounding the false positive (FP) and false negative (FN) probabilities associated with a human-rated launch vehicle abort trigger (AT) that includes sensor data qualification (SDQ). In this context, an AT is a hardware and software mechanism designed to detect the existence of a specific abort condition. Also, SDQ is an algorithmic approach used to identify sensor data suspected of being corrupt so that suspect data does not adversely affect an AT's detection capability. The FP and FN methodologies presented here were developed to support estimation of the probabilities of loss of crew and loss of mission for the Space Launch System (SLS) which is being developed by the National Aeronautics and Space Administration (NASA). The paper provides a brief overview of system health management as being an extension of control theory; and describes how ATs and the calculation of FP and FN probabilities relate to this theory. The discussion leads to a detailed presentation of the FP and FN methodology and an example showing how the FP and FN calculations are performed. This detailed presentation includes a methodology for calculating the change in FP and FN probabilities that result from including SDQ in the AT architecture. To avoid proprietary and sensitive data issues, the example incorporates a mixture of open literature and fictitious reliability data. Results presented in the paper demonstrate the effectiveness of the approach in providing quantitative estimates that bound the probability of a FP or FN abort determination.
To draw inferences about gamma-ray burst (GRB) source populations based on Swift observations, it is essential to understand the detection efficiency of the Swift burst alert telescope (BAT). This study considers the problem of modeling the Swift BAT triggering algorithm for long GRBs, a computationally expensive procedure, and models it using machine learning algorithms. A large sample of simulated GRBs from Lien et al. (2014) is used to train various models: random forests, boosted decision trees (with AdaBoost), support vector machines, and artificial neural networks. The best models have accuracies of approximately greater than 97% (approximately less than 3% error), which is a significant improvement on a cut in GRB flux which has an accuracy of 89:6% (10:4% error). These models are then used to measure the detection efficiency of Swift as a function of redshift z, which is used to perform Bayesian parameter estimation on the GRB rate distribution. We find a local GRB rate density of eta(sub 0) approximately 0.48(+0.41/-0.23) Gpc(exp -3) yr(exp -1) with power-law indices of eta(sub 1) approximately 1.7(+0.6/-0.5) and eta(sub 2) approximately -5.9(+5.7/-0.1) for GRBs above and below a break point of z(sub 1) approximately 6.8(+2.8/-3.2). This methodology is able to improve upon earlier studies by more accurately modeling Swift detection and using this for fully Bayesian model fitting. The code used in this is analysis is publicly available online.
We report here the discovery by the Intermediate Palomar Transient Factory (iPTF) of iPTF14yb, a luminous (Mr >> -27.8 mag), cosmological (redshift 1.9733), rapidly fading optical transient. We demonstrate, based on probabilistic arguments and a comparison with the broader population, that iPTF14yb is the optical afterglow of the long-duration gamma-ray burst GRB 140226A. This marks the first unambiguous discovery of a GRB afterglow prior to (and thus entirely independent of) an associated high-energy trigger. We estimate the rate of iPTF14yb-like sources (i.e., cosmologically distant relativistic explosions) based on iPTF observations, inferring an all-sky value of Rrel = 610/yr (68% confidence interval of 110-2000/yr). Our derived rate is consistent (within the large uncertainty) with the all-sky rate of on-axis GRBs derived by the Swift satellite. Finally, we briefly discuss the implications of the nondetection to date of bona fide "orphan" afterglows (i.e., those lacking detectable high-energy emission) on GRB beaming and the degree of baryon loading in these relativistic jets.