Hyperbolic Orbits and the Planetary Flylby Anomaly
NASA Technical Reports Server (NTRS)
Wilson, T.L.; Blome, H.J.
2009-01-01
Space probes in the Solar System have experienced unexpected changes in velocity known as the flyby anomaly [1], as well as shifts in acceleration referred to as the Pioneer anomaly [2-4]. In the case of Earth flybys, ESA s Rosetta spacecraft experienced the flyby effect and NASA s Galileo and NEAR satellites did the same, although MESSENGER did not possibly due to a latitudinal property of gravity assists. Measurements indicate that both anomalies exist, and explanations have varied from the unconventional to suggestions that new physics in the form of dark matter might be the cause of both [5]. Although dark matter has been studied for over 30 years, there is as yet no strong experimental evidence supporting it [6]. The existence of dark matter will certainly have a significant impact upon ideas regarding the origin of the Solar System. Hence, the subject is very relevant to planetary science. We will point out here that one of the fundamental problems in science, including planetary physics, is consistency. Using the well-known virial theorem in astrophysics, it will be shown that present-day concepts of orbital mechanics and cosmology are not consistent for reasons having to do with the flyby anomaly. Therefore, the basic solution regarding the anomalies should begin with addressing the inconsistencies first before introducing new physics.
NASA Astrophysics Data System (ADS)
Ko, H.; Scheeres, D.
2014-09-01
Representing spacecraft orbit anomalies between two separate states is a challenging but an important problem in achieving space situational awareness for an active spacecraft. Incorporation of such a capability could play an essential role in analyzing satellite behaviors as well as trajectory estimation of the space object. A general way to deal with the anomaly problem is to add an estimated perturbing acceleration such as dynamic model compensation (DMC) into an orbit determination process based on pre- and post-anomaly tracking data. It is a time-consuming numerical process to find valid coefficients to compensate for unknown dynamics for the anomaly. Even if the orbit determination filter with DMC can crudely estimate an unknown acceleration, this approach does not consider any fundamental element of the unknown dynamics for a given anomaly. In this paper, a new way of representing a spacecraft anomaly using an interpolation technique with the Thrust-Fourier-Coefficients (TFCs) is introduced and several anomaly cases are studied using this interpolation method. It provides a very efficient way of reconstructing the fundamental elements of the dynamics for a given spacecraft anomaly. Any maneuver performed by a satellite transitioning between two arbitrary orbital states can be represented as an equivalent maneuver using an interpolation technique with the TFCs. Given unconnected orbit states between two epochs due to a spacecraft anomaly, it is possible to obtain a unique control law using the TFCs that is able to generate the desired secular behavior for the given orbital changes. This interpolation technique can capture the fundamental elements of combined unmodeled anomaly events. The interpolated orbit trajectory, using the TFCs compensating for a given anomaly, can be used to improve the quality of orbit fits through the anomaly period and therefore help to obtain a good orbit determination solution after the anomaly. Orbit Determination Toolbox (ODTBX
Orbital Anomalies in Goddard Spacecraft for Calendar Year 1994
NASA Technical Reports Server (NTRS)
Thomas, Walter B.
1996-01-01
This report summarizes and updates the annual on-orbit performance between January I and December 31, 1994, for spacecraft built by or managed by the Goddard Space Flight Center (GSFC). During 1994, GSFC had 27 active orbiting satellites and I Shuttle-launched and retrieved 'free flyer.' There were 310 reported anomalies among 21 satellites and one GSFC instrument (TOMS). GOES-8 accounted for 66 anomalies, and SAMPES reported 155 'anomalies'. Of the 155 anomalies reported for all but SAMPEX, only 4 affected the spacecraft missions 'substantially' or greater, that is, presented a loss of more than 33% of the total missions. The most frequent subsystem anomalies were Instrument/Payload(44), Timing Command and Control(40), and Attitude Control Systems(33). Of the non-SAMPEX anomalies, 29% had no effect on the missions and 28% caused subsystem or instrument degradation and, for another 28%, no anomaly effect on the mission could be determined. Fifty-three percent of non-SAMPEX anomalies could not be classified according to 'type'; the other most common types were 'systemic'(35), 'random'(19), and 'normal or expected operation'(15). Forty percent of the anomalies were not classified according to failure category; the remaining most frequent occurrences were 'design problems'(50) and 'other known problems'(35).
Automated anomaly detection for Orbiter High Temperature Reusable Surface Insulation
NASA Astrophysics Data System (ADS)
Cooper, Eric G.; Jones, Sharon M.; Goode, Plesent W.; Vazquez, Sixto L.
1992-11-01
The description, analysis, and experimental results of a method for identifying possible defects on High Temperature Reusable Surface Insulation (HRSI) of the Orbiter Thermal Protection System (TPS) is presented. Currently, a visual postflight inspection of Orbiter TPS is conducted to detect and classify defects as part of the Orbiter maintenance flow. The objective of the method is to automate the detection of defects by identifying anomalies between preflight and postflight images of TPS components. The initial version is intended to detect and label gross (greater than 0.1 inches in the smallest dimension) anomalies on HRSI components for subsequent classification by a human inspector. The approach is a modified Golden Template technique where the preflight image of a tile serves as the template against which the postflight image of the tile is compared. Candidate anomalies are selected as a result of the comparison and processed to identify true anomalies. The processing methods are developed and discussed, and the results of testing on actual and simulated tile images are presented. Solutions to the problems of brightness and spatial normalization, timely execution, and minimization of false positives are also discussed.
Automated anomaly detection for Orbiter High Temperature Reusable Surface Insulation
NASA Technical Reports Server (NTRS)
Cooper, Eric G.; Jones, Sharon M.; Goode, Plesent W.; Vazquez, Sixto L.
1992-01-01
The description, analysis, and experimental results of a method for identifying possible defects on High Temperature Reusable Surface Insulation (HRSI) of the Orbiter Thermal Protection System (TPS) is presented. Currently, a visual postflight inspection of Orbiter TPS is conducted to detect and classify defects as part of the Orbiter maintenance flow. The objective of the method is to automate the detection of defects by identifying anomalies between preflight and postflight images of TPS components. The initial version is intended to detect and label gross (greater than 0.1 inches in the smallest dimension) anomalies on HRSI components for subsequent classification by a human inspector. The approach is a modified Golden Template technique where the preflight image of a tile serves as the template against which the postflight image of the tile is compared. Candidate anomalies are selected as a result of the comparison and processed to identify true anomalies. The processing methods are developed and discussed, and the results of testing on actual and simulated tile images are presented. Solutions to the problems of brightness and spatial normalization, timely execution, and minimization of false positives are also discussed.
Orbital debris hazard insights from spacecraft anomalies studies
NASA Astrophysics Data System (ADS)
McKnight, Darren S.
2016-09-01
Since the dawning of the space age space operators have been tallying spacecraft anomalies and failures then using these insights to improve the space systems and operations. As space systems improved and their lifetimes increased, the anomaly and failure modes have multiplied. Primary triggers for space anomalies and failures include design issues, space environmental effects, and satellite operations. Attempts to correlate anomalies to the orbital debris environment have started as early as the mid-1990's. Early attempts showed tens of anomalies correlated well to altitudes where the cataloged debris population was the highest. However, due to the complexity of tracing debris impacts to mission anomalies, these analyses were found to be insufficient to prove causation. After the fragmentation of the Chinese Feng-Yun satellite in 2007, it was hypothesized that the nontrackable fragments causing anomalies in LEO would have increased significantly from this event. As a result, debris-induced anomalies should have gone up measurably in the vicinity of this breakup. Again, the analysis provided some subtle evidence of debris-induced anomalies but it was not convincing. The continued difficulty in linking debris flux to satellite anomalies and failures prompted the creation of a series of spacecraft anomalies and failure workshops to investigate the identified shortfalls. These gatherings have produced insights into why this process is not straightforward. Summaries of these studies and workshops are presented and observations made about how to create solutions for anomaly attribution, especially as it relates to debris-induced spacecraft anomalies and failures.
Analysis of spacecraft on-orbit anomalies and lifetimes
NASA Technical Reports Server (NTRS)
Bloomquist, C.; Graham, W.
1983-01-01
Analyses of the on-orbit performance of forty-four unmanned NASA spacecraft are presented. Included are detailed descriptions and classifications of over 600 anomalies; each anomalous incident represents one reported deviation from expected spacecraft performance. Charts depicting satellite lifetimes and the performance of their major subsystems are included. Engineering analyses to further investigate the kinds and frequencies of various classes of anomalies have been conducted. An improved method for charting spacecraft capability as a function of time on orbit is explored.
The intermediate anomaly. [satellite orbit integration
NASA Technical Reports Server (NTRS)
Nacozy, P.
1977-01-01
Time transformations of the equation dt = cr to the n ds, where s is a variable called the intermediate anomaly, are known to reduce global error in the solution of gravitational systems obtained by numerical integration. Attention is given to the Sundman time transformation, and its relation to equations of Keplerian elliptical motion.
Variations and anomalies of the human orbital muscles.
von Lüdinghausen, M; Miura, M; Würzler, N
1999-01-01
The purpose of the study is to describe some rare and hitherto unreported uni- and bilateral anomalies of the orbital rectus muscles (duplication, triplication, accessory bellies, interrectal muscular bridges, false insertion) which were found by chance during the dissections of three cadavers (one adult, two fetuses). The levator palpebrae superioris muscles in the same specimens exhibited some variations (medial and lateral muscular slips) and anomalies (bipartite and unipartite levator). Cross-sections of interrectal bridges in the orbit of an adult were investigated histologically. Numerous nerves were distributed in the interstitium; groups of lipofuscin granules were found in all the myocytes. An attempt is made to explain these anomalies and variations through consideration of developmental and comparative anatomy. The relevance of these anomalies in coronal sections such as those acquired from CT and MRI is discussed.
Frozen-anomaly transformation for the elliptic rendezvous problem
NASA Astrophysics Data System (ADS)
Roa, Javier; Peláez, Jesús
2015-01-01
A new solution to relative motion on elliptical orbits is presented, based on a novel transformation from the reference state vector to the relative state vector. The relative orbit is constructed assuming that the anomaly, and not the time, is the invariant element throughout the transformation. This concept arises naturally from the variational form of anomaly-explicit formulations. In particular, this paper explores the capabilities of a formulation developed by Peláez et al. (Celest Mech Dyn Astron. 97, 131-150, 2007), called Dromo. This formulation exploits the advantages of the ideal reference frames and quaternionic descriptions of the orbital plane. The linear variational form of the equations of motion in Dromo is developed herein, and the resulting transformation matrix is presented. When applied to the reference state vector, this linear transformation provides the relative state vector at any step. The invariance in the anomaly implies a certain time delay in the results. Physical times for leader and follower do not coincide after the transformation. To recover the sense of the solution an additional correction is applied a posteriori to cancel this intrinsic time delay. The performance of the new transformation is compared against previous solutions to the problem through a set of numerical examples. Important error reductions in determining the relative orbit are observed in these tests.
BRASILSAT A2: Ground and in-orbit anomalies
NASA Technical Reports Server (NTRS)
Azevedoferreira, Sergio Ricardo
1987-01-01
A description of the anomalies encountered during ground preparation for launch and in-orbit operation of Brasilsat A2 batteries is given. Processes used during recovery of these batteries and the improvement on main parameters are discussed, covering many cycles of reconditionings and behavior during September/86 eclipse charge/discharge cycles.
Risk Mitigation for Managing On-Orbit Anomalies
NASA Technical Reports Server (NTRS)
La, Jim
2010-01-01
This slide presentation reviews strategies for managing risk mitigation that occur with anomalies in on-orbit spacecraft. It reviews the risks associated with mission operations, a diagram of the method used to manage undesirable events that occur which is a closed loop fault analysis and until corrective action is successful. It also reviews the fish bone diagram which is used if greater detail is required and aids in eliminating possible failure factors.
Experimental and Computational Analysis of Shuttle Orbiter Hypersonic Trim Anomaly
NASA Technical Reports Server (NTRS)
Brauckmann, Gregory J.; Paulson, John W., Jr.; Weilmuenster, K. James
1995-01-01
During the high-Mach-number, high-altitude portion of the first entry of the Shuttle Orbiter, the vehicle exhibited a nose-up pitching moment relative to preflight prediction of approximately Delta Cm = 0.03. This trim anomaly has been postulated to be due to compressibility, viscous, and/or real-gas (lowered specific heat ratio gamma) effects on basic body pitching moment, body-flap effectiveness, or both. In order to assess the relative contribution of each of these effects, an experimental study was undertaken to examine the effects of Mach number, Reynolds number, and ratio of specific heats. Complementary computational solutions were obtained for wind-tunnel and flight conditions. The primary cause of the anomaly was determined to be lower pressures on the aft windward surface of the Orbiter than deduced from hypersonic wind-tunnel tests with ideal- or near-ideal-gas test flow. The lower pressure levels are a result of the lowering of the flowfield gamma due to high-temperature effects. This phenomenon was accurately simulated in a hypersonic wind tunnel using a heavy gas, which provided a lower, gamma, and was correctly predicted by Navier-Stokes computations using nonequilibrium chemistry.
NASA Technical Reports Server (NTRS)
Iona, Glenn; Butler, James; Guenther, Bruce; Graziani, Larissa; Johnson, Eric; Kennedy, Brian; Kent, Criag; Lambeck, Robert; Waluschka, Eugne; Xiong, Xiaoxiong
2012-01-01
A gradual, but persistent, decrease in the optical throughput was detected during the early commissioning phase for the Suomi National Polar-Orbiting Partnership (SNPP) Visible Infrared Imager Radiometer Suite (VIIRS) Near Infrared (NIR) bands. Its initial rate and unknown cause were coincidently coupled with a decrease in sensitivity in the same spectral wavelength of the Solar Diffuser Stability Monitor (SDSM) raising concerns about contamination or the possibility of a system-level satellite problem. An anomaly team was formed to investigate and provide recommendations before commissioning could resume. With few hard facts in hand, there was much speculation about possible causes and consequences of the degradation. Two different causes were determined as will be explained in this paper. This paper will describe the build and test history of VIIRS, why there were no indicators, even with hindsight, of an on-orbit problem, the appearance of the on-orbit anomaly, the initial work attempting to understand and determine the cause, the discovery of the root cause and what Test-As-You-Fly (TAYF) activities, can be done in the future to greatly reduce the likelihood of similar optical anomalies. These TAYF activities are captured in the lessons learned section of this paper.
NASA Astrophysics Data System (ADS)
Saleh, Joseph Homer; Geng, Fan; Ku, Michelle; Walker, Mitchell L. R.
2017-10-01
With a few hundred spacecraft launched to date with electric propulsion (EP), it is possible to conduct an epidemiological study of EP's on orbit reliability. The first objective of the present work was to undertake such a study and analyze EP's track record of on orbit anomalies and failures by different covariates. The second objective was to provide a comparative analysis of EP's failure rates with those of chemical propulsion. Satellite operators, manufacturers, and insurers will make reliability- and risk-informed decisions regarding the adoption and promotion of EP on board spacecraft. This work provides evidence-based support for such decisions. After a thorough data collection, 162 EP-equipped satellites launched between January 1997 and December 2015 were included in our dataset for analysis. Several statistical analyses were conducted, at the aggregate level and then with the data stratified by severity of the anomaly, by orbit type, and by EP technology. Mean Time To Anomaly (MTTA) and the distribution of the time to (minor/major) anomaly were investigated, as well as anomaly rates. The important findings in this work include the following: (1) Post-2005, EP's reliability has outperformed that of chemical propulsion; (2) Hall thrusters have robustly outperformed chemical propulsion, and they maintain a small but shrinking reliability advantage over gridded ion engines. Other results were also provided, for example the differentials in MTTA of minor and major anomalies for gridded ion engines and Hall thrusters. It was shown that: (3) Hall thrusters exhibit minor anomalies very early on orbit, which might be indicative of infant anomalies, and thus would benefit from better ground testing and acceptance procedures; (4) Strong evidence exists that EP anomalies (onset and likelihood) and orbit type are dependent, a dependence likely mediated by either the space environment or differences in thrusters duty cycles; (5) Gridded ion thrusters exhibit both
Orbital problems in GPS interferometry
NASA Astrophysics Data System (ADS)
Zielinski, Janusz B.
The GPS orbits and the influence of the orbital errors on the geodetic determination were investigated during the last few years. In the paper, the summary of some analyses is presented concerning the nature of the interferometric observations, the propagation of the orbital errors, and the correlations and covariances in geodetic GPS solutions. One of the results was a proof that, in relative determinations by GPS, the error propagation factor is close to b/10 h, that is almost one order smaller than previously supposed.
Vigilance problems in orbiter processing
NASA Technical Reports Server (NTRS)
Swart, William W.; Safford, Robert R.; Kennedy, David B.; Yadi, Bert A.; Barth, Timothy S.
1993-01-01
A pilot experiment was done to determine what factors influence potential performance errors related to vigilance in Orbiter processing activities. The selected activities include post flight inspection for burned gap filler material and pre-rollout inspection for tile processing shim material. It was determined that the primary factors related to performance decrement were the color of the target and the difficulty of the target presentation.
Practical method to identify orbital anomaly as spacecraft breakup in the geostationary region
NASA Astrophysics Data System (ADS)
Uetsuhara, Masahiko; Hanada, Toshiya
2013-09-01
Identifying spacecraft breakup events is an essential issue for better understanding of the current orbital debris environment. This paper proposes an observation planning approach to identify an orbital anomaly, which appears as a significant discontinuity in archived orbital history, as a spacecraft breakup. The proposed approach is applicable to orbital anomalies in the geostationary region. The proposed approach selects a spacecraft that experienced an orbital anomaly, and then predicts trajectories of possible fragments of the spacecraft at an observation epoch. This paper theoretically demonstrates that observation planning for the possible fragments can be conducted. To do this, long-term behaviors of the possible fragments are evaluated. It is concluded that intersections of their trajectories will converge into several corresponding regions in the celestial sphere even if the breakup epoch is not specified and it has uncertainty of the order of several weeks.
NASA Technical Reports Server (NTRS)
Sutter, James K.; Leidecker, Henning W.; Panda, Binayak; Piascik, Robert S.; Muirhead, Brian K.; Peeler, Debra
2009-01-01
The NESC eras requested by the NASA Jet Propulsion Laboratory (JPL) to conduct an independent review of the Mars Reconnaissance Orbiter (MRO) Thermal/Vacuum (T/V) Anomaly Assessment. Because the anomaly resulted in the surface contamination of the MRO, selected members of the Materials Super Problem Resolution Team (SPRT) and the NASA technical community having technical expertise relative to contamination issues were chosen for the independent review. The consultation consisted of a review of the MRO Project's reported response to the assessment findings, a detailed review of JPL technical assessment final report, and detailed discussions with the JPL assessment team relative to their findings.
Ye, Fei; Yuan, Yunbin; Tan, Bingfeng; Ou, Jikun
2017-01-01
The failure to detect anomalies and maneuvering of the orbits of navigation satellite sensors will deteriorate the performance of positioning and orbit determination. Motivated by the influence of the frequent maneuvering of BDS GEO and IGSO satellites, this paper analyzes the limitations of existing methods, where BDS orbit maneuvering and anomalies can be detected, and develops a method to solve this problem based on the RMS model of orbit mutual differences proposed in this paper. The performance of this method was assessed by comparison with the health flag of broadcast ephemeris, precise orbit products of GFZ, the O-C values of a GNSS station and a conventional method. The results show that the performance of the method developed in this paper is better than that of the conventional method when the periodicity and trend items are obvious. Meanwhile, three additional verification results show that the method developed in this paper can find error information in the merged broadcast ephemeris provided by iGMAS. Furthermore, from the testing results, it can be seen that the detection of anomaly and maneuvering items do not affect each other based on the robust thresholds constructed in this paper. In addition, the precise orbit of the maneuvering satellites can be determined under the circumstances that the maneuver information detected in this paper is used, and the root mean square (RMS) of orbit overlap comparison for GEO-03/IGSO-03 in Radial, Along, Cross, 1D-RMS are 0.7614/0.4460 m, 1.8901/0.3687 m, 0.3392/0.2069 m, 2.0657/0.6145 m, respectively. PMID:28509847
Ye, Fei; Yuan, Yunbin; Tan, Bingfeng; Ou, Jikun
2017-05-16
The failure to detect anomalies and maneuvering of the orbits of navigation satellite sensors will deteriorate the performance of positioning and orbit determination. Motivated by the influence of the frequent maneuvering of BDS GEO and IGSO satellites, this paper analyzes the limitations of existing methods, where BDS orbit maneuvering and anomalies can be detected, and develops a method to solve this problem based on the RMS model of orbit mutual differences proposed in this paper. The performance of this method was assessed by comparison with the health flag of broadcast ephemeris, precise orbit products of GFZ, the O-C values of a GNSS station and a conventional method. The results show that the performance of the method developed in this paper is better than that of the conventional method when the periodicity and trend items are obvious. Meanwhile, three additional verification results show that the method developed in this paper can find error information in the merged broadcast ephemeris provided by iGMAS. Furthermore, from the testing results, it can be seen that the detection of anomaly and maneuvering items do not affect each other based on the robust thresholds constructed in this paper. In addition, the precise orbit of the maneuvering satellites can be determined under the circumstances that the maneuver information detected in this paper is used, and the root mean square (RMS) of orbit overlap comparison for GEO-03/IGSO-03 in Radial, Along, Cross, 1D-RMS are 0.7614/0.4460 m, 1.8901/0.3687 m, 0.3392/0.2069 m, 2.0657/0.6145 m, respectively.
The association of spacecraft anomalies with electron/proton particle fluxes at different orbits
NASA Astrophysics Data System (ADS)
Yi, K.; Moon, Y. J.
2016-12-01
In this study, we investigate 195 satellite anomaly data from 1998 to 2010 from Satellite News Digest (SND) to understand the association between spacecraft anomaly and space weather condition. The spacecraft anomalies are classified into Attitude & Propulsion, Power, Control, Telemetry, Instrument and unknown. For the investigation we divide these data according to the spacecraft orbit and launched year. Spacecraft's orbits are classified into the following two groups : (1) high altitude and low inclination, and (2) low altitude and high inclination. Launched year of spacecraft are divided into two groups: 1991 1998 and 1999 2007. We examine the association between these anomaly data and daily peak particle (electron and proton) flux data from GOES as well as their occurrence rates. To determine the association, we use two criteria that electron criterion is >10,000 pfu and proton criterion is >100 pfu. Main results from this study are as follows. First, the number of days satisfying the criteria for electron flux has a peak near a week before the anomaly day and decreases from the peak day to the anomaly day, while that for proton flux has a peak near the anomaly day. Second, we found a similar pattern for the mean daily peak particle (electron and proton) flux as a function of day before the anomaly day. Third, an examination of multiple spacecraft anomaly events, which are likely to occur by severe space weather effects, shows that anomalies mostly occur either when electron fluxes are in the declining stage, or when daily proton peak fluxes are strongly enhanced. Fourth, the time delay between the anomaly day and the day having the highest daily peak electron flux for the recent launching period (1999-2007) is noticeably larger than those for the older periods, implying that the anomaly characteristics associated with electron flux change with time.
Efficient Trajectory Propagation for Orbit Determination Problems
NASA Technical Reports Server (NTRS)
Roa, Javier; Pelaez, Jesus
2015-01-01
Regularized formulations of orbital motion apply a series of techniques to improve the numerical integration of the orbit. Despite their advantages and potential applications little attention has been paid to the propagation of the partial derivatives of the corresponding set of elements or coordinates, required in many orbit-determination scenarios and optimization problems. This paper fills this gap by presenting the general procedure for integrating the state-transition matrix of the system together with the nominal trajectory using regularized formulations and different sets of elements. The main difficulty comes from introducing an independent variable different from time, because the solution needs to be synchronized. The correction of the time delay is treated from a generic perspective not focused on any particular formulation. The synchronization using time-elements is also discussed. Numerical examples include strongly-perturbed orbits in the Pluto system, motivated by the recent flyby of the New Horizons spacecraft, together with a geocentric flyby of the NEAR spacecraft.
Lageos orbit and the albedo problem
NASA Technical Reports Server (NTRS)
Rubincam, D. P.
1984-01-01
The objective was to obtain an analytic expression for the radiation pressure force on a satellite due to sunlight reflected from the Earth. The Lageos satellite undergoes unexplained along-track accelerations. These accelerations are believed to be due mainly to terrestrial radiation pressure. The effect of sunlight reflected off the surface of the Earth must thus be modeled to insure an accurate orbit for Lageos. An accurate orbit is necessary for carrying out Lageos' mission of measuring tectonic plate motion, polar motion, and Earth rotation. The present investigation focuses on a spherical harmonic approach to the problem. An equation for the force was obtained by assuming the Earth's surface reflects sunlight according to Lambert's law. The equation is an integral over the whole Earth's surface. Expressions occurring inside the integral are expressed in terms of spherical harmonics. The problem is thus reduced to integrating products of spherical harmonics.
Ground verification of in-orbit anomalies in the double probe electric field experiment on Freja
Johlander, B.; Harboe-Soerensen, R.
1996-12-01
Unit level proton irradiation as a tool to debug low cost space experiment design and component selection has been shown to give excellent agreement with in-orbit anomalies. The procedures used and experimental results obtained are reported together with an indication of resources spent for this approach.
Fuzzy Kernel k-Medoids algorithm for anomaly detection problems
NASA Astrophysics Data System (ADS)
Rustam, Z.; Talita, A. S.
2017-07-01
Intrusion Detection System (IDS) is an essential part of security systems to strengthen the security of information systems. IDS can be used to detect the abuse by intruders who try to get into the network system in order to access and utilize the available data sources in the system. There are two approaches of IDS, Misuse Detection and Anomaly Detection (behavior-based intrusion detection). Fuzzy clustering-based methods have been widely used to solve Anomaly Detection problems. Other than using fuzzy membership concept to determine the object to a cluster, other approaches as in combining fuzzy and possibilistic membership or feature-weighted based methods are also used. We propose Fuzzy Kernel k-Medoids that combining fuzzy and possibilistic membership as a powerful method to solve anomaly detection problem since on numerical experiment it is able to classify IDS benchmark data into five different classes simultaneously. We classify IDS benchmark data KDDCup'99 data set into five different classes simultaneously with the best performance was achieved by using 30 % of training data with clustering accuracy reached 90.28 percent.
NASA Astrophysics Data System (ADS)
Moore, Guy S. M.; Moore, Richard E. M.
2013-10-01
All proposed gravitational explanations of the Pioneer anomaly must crucially face the Equivalence Principle. Thus, if Pioneers 10 and 11 were influenced by anomalous gravitational effects in regions containing other Solar System bodies, then those bodies should likewise be influenced, irrespective of their shape, composition or mass. Although the lack of any observed influence upon planetary orbits severely constrains such explanations, here we aim to construct by computer modeling, hypothetical gravitating annuli having no gravitational impact on planetary orbits from Mercury to Neptune. One model has a central zone, free of radial gravitation in the annular plane, and an ‘onset’ beyond Saturn’s orbit, where sunward annular gravitation increases to match the Pioneer anomaly data. Sharp nulls are included so that Uranus and Neptune escape this influence. Such models can be proportionately reduced in mass: a 1 % contribution to the anomaly requires an annulus of approximately 1 Earth mass. It is thus possible to comply with the JPL assessment of newly recovered data attributing 80 %, or more, of the anomaly to spacecraft heat, which appears to allow small contributions from other causes. Following the possibility of an increasing Kuiper belt density at great ranges, another model makes an outward small anomalous gravitation in the TNO region, tallying with an observed slight indication of such an effect, suggesting that New Horizons may slightly accelerate in this region.
Bardeen, W.A.
1985-08-01
Anomalies have a diverse impact on many aspects of physical phenomena. The role of anomalies in determining physical structure from the amplitude for decay to the foundations of superstring theory will be reviewed. 36 refs.
ERIC Educational Resources Information Center
Online-Offline, 1999
1999-01-01
This theme issue on anomalies includes Web sites, CD-ROMs and software, videos, books, and additional resources for elementary and junior high school students. Pertinent activities are suggested, and sidebars discuss UFOs, animal anomalies, and anomalies from nature; and resources covering unexplained phenonmenas like crop circles, Easter Island,…
ERIC Educational Resources Information Center
Online-Offline, 1999
1999-01-01
This theme issue on anomalies includes Web sites, CD-ROMs and software, videos, books, and additional resources for elementary and junior high school students. Pertinent activities are suggested, and sidebars discuss UFOs, animal anomalies, and anomalies from nature; and resources covering unexplained phenonmenas like crop circles, Easter Island,…
Optimal solutions of unobservable orbit determination problems
NASA Astrophysics Data System (ADS)
Cicci, David A.; Tapley, Byron D.
1988-12-01
The method of data augmentation, in the form ofa priori covariance information on the reference solution, as a means to overcome the effects of ill-conditioning in orbit determination problems has been investigated. Specifically, for the case when ill-conditioning results from parameter non-observability and an appropriatea priori covariance is unknown, methods by which thea priori covariance is optimally chosen are presented. In problems where an inaccuratea priori covariance is provided, the optimal weighting of this data set is obtained. The feasibility of these ‘ridge-type’ solution methods is demonstrated by their application to a non-observable gravity field recovery simulation. In the simulation, both ‘ridge-type’ and conventional solutions are compared. Substantial improvement in the accuracy of the conventional solution is realized by the use of these ridge-type solution methods. The solution techniques presented in this study are applicable to observable, but ill-conditioned problems as well as the unobservable problems directly addressed. For the case of observable problems, the ridge-type solutions provide an improvement in the accuracy of the ordinary least squares solutions.
NASA Technical Reports Server (NTRS)
Rapp, R. H.
1974-01-01
Results have been obtained for the solution of 184 15-deg equal-area blocks directly from the analysis of satellite orbits, and from a combination of the satellite results with terrestrial gravity material. This test computation, made to verify the method, used 17,632 optical observations from ten satellites in 29 arcs averaging in length seven days. Analysis of the satellite results were made by comparing the solved for anomalies with the terrestrial anomaly set, and by developing the solved for anomalies into potential coefficients which were compared to the GEM 3 set of potential coefficients to degree 12. These comparisons indicated improvement in each solution as more arcs were added. The programs used in this solution can easily be used to solve for smaller size blocks and handle additional data types. The only limitation will be computer core availability and computer time.
NASA Technical Reports Server (NTRS)
Rapp, R. H.
1974-01-01
Results have been obtained for the solution of 184 15-deg equal-area blocks directly from the analysis of satellite orbits, and from a combination of the satellite results with terrestrial gravity material. This test computation, made to verify the method, used 17,632 optical observations from ten satellites in 29 arcs averaging in length seven days. Analysis of the satellite results were made by comparing the solved for anomalies with the terrestrial anomaly set, and by developing the solved for anomalies into potential coefficients which were compared to the GEM 3 set of potential coefficients to degree 12. These comparisons indicated improvement in each solution as more arcs were added. The programs used in this solution can easily be used to solve for smaller size blocks and handle additional data types. The only limitation will be computer core availability and computer time.
Antonov, Nina K; Spence-Shishido, Allyson; Marathe, Kalyani S; Tlougan, Brook; Kazim, Michael; Sultan, Sally; Hess, Christopher P; Morel, Kimberly D; Frieden, Ilona J; Garzon, Maria C
2015-01-01
We present two cases of infants with a similar constellation of clinical findings: retro-orbital infantile hemangioma (IH), internal carotid artery (ICA) arteriopathy, and intracranial IH. In both cases, intracranial vascular anomalies and hemangiomas were found incidentally during evaluation of unilateral proptosis. Neither infant had evidence of cutaneous segmental IH of the face or neck, which might have provided a clue to the diagnosis of PHACE syndrome or of intracranial hemangiomas. In one case, intracranial involvement was particularly extensive and function threatening, with mass effect on the brain parenchyma. These cases serve to highlight the fact that clinical findings of proptosis, globe deviation, and strabismus should prompt immediate imaging to confirm the presence of orbital IHs and to exclude other diagnoses. Moreover, based on our cases and the embryologic origin of the orbit as a unique developmental unit, patients with confirmed retro-orbital IHs should undergo evaluation for anomalies associated with PHACE syndrome. Patients with orbital IHs and an additional major criterion for PHACE syndrome should be considered to have definite, and not just possible, PHACE syndrome.
Closed orbit related problems: Correction, feedback, and analysis
Bozoki, E.S.
1995-02-01
Orbit correction - moving the orbit to a desired orbit, orbit stability - keeping the orbit on the desired orbit using feedback to filter out unwanted noise, and orbit analysis - to learn more about the model of the machine, are strongly interrelated. They are the three facets of the same problem. The better one knows the model of the machine, the better the predictions that can be made on the behavior of the machine (inverse modeling) and the more accurately one can control the machine. On the other hand, one of the tools to learn more about the machine (modeling) is to study and analyze the orbit response to {open_quotes}kicks.{close_quotes}
Variety of elastic anomalies in an orbital-active nearly itinerant cobalt vanadate spinel
NASA Astrophysics Data System (ADS)
Watanabe, Tadataka; Yamada, Shogo; Koborinai, Rui; Katsufuji, Takuro
2017-07-01
We perform ultrasound velocity measurements on a single crystal of nearly metallic spinel Co1.21V1.79O4 which exhibits a ferrimagnetic phase transition at TC˜165 K. The experiments reveal a variety of elastic anomalies in not only the paramagnetic phase above TC but also the ferrimagnetic phase below TC, which should be driven by the nearly itinerant character of the orbitally degenerate V 3 d electrons. In the paramagnetic phase above TC, the elastic moduli exhibit elastic-mode-dependent unusual temperature variations, suggesting the existence of a dynamic spin-cluster state. Furthermore, above TC, the sensitive magnetic-field response of the elastic moduli suggests that, with the negative magnetoresistance, the magnetic-field-enhanced nearly itinerant character of the V 3 d electrons emerges from the spin-cluster state. This should be triggered by the inter-V-site interactions acting on the orbitally degenerate 3 d electrons. In the ferrimagnetic phase below TC, the elastic moduli exhibit distinct anomalies at T1˜95 K and T2˜50 K, with a sign change of the magnetoresistance at T1 (positive below T1) and an enhancement of the positive magnetoresistance below T2, respectively. These observations below TC suggest the successive occurrence of an orbital glassy order at T1 and a structural phase transition at T2, where the rather localized character of the V 3 d electrons evolves below T1 and is further enhanced below T2.
NASA Astrophysics Data System (ADS)
Pimnoo, Ammarin
2016-07-01
Geo-Informatics and Space Technology Development Agency (GISTDA) has initiative THEOS-2 project after the THEOS-1 has been operated for more than 7 years which is over the lifetime already. THEOS-2 project requires not only the development of earth observation satellite(s), but also the development of the area-based decision making solution platform comprising of data, application systems, data processing and production system, IT infrastructure improvement and capacity building through development of satellites, engineering model, and infrastructures capable of supporting research in related fields. The developing satellites in THEOS-2 project are THAICHOTE-2 and THAICHOTE-3. This paper focuses the orbit design of THAICHOTE-2 & 3. It discusses the satellite orbit design for the second and third EOS of Thailand. In this paper, both THAICHOTE will be simulated in an equatorial orbit as a formation flying which will be compared the productive to THAICHOTE-1 (THEOS-1). We also consider a serious issue in equatorial orbit design, namely the issue of the geomagnetic field in the area of the eastern coast of South America, called the South Atlantic Magnetic Anomaly (SAMA). The high-energy particles of SAMA comprise a radiation environment which can travel through THAICHOTE-2 & 3 material and deposit kinetic energy. This process causes atomic displacement or leaves a stream of charged atoms in the incident particles' wake. It can cause damage to the satellite including reduction of power generated by solar arrays, failure of sensitive electronics, increased background noise in sensors, and exposure of the satellite devices to radiation. This paper demonstrates the loss of ionizing radiation damage and presents a technique to prevent damage from high-energy particles in the SAMA.
Resolving the Problem of Stellar Orbital Anisotropy
NASA Astrophysics Data System (ADS)
Humphrey, Philip
2006-09-01
Mass profiles of elliptical galaxies provide an insight into dark matter (DM) halo formation, while orbital structure is tied to evolutionary history. Unfortunately the mass-anisotropy degeneracy prevents either from being uniquely determined by stellar kinematics measurements alone. A recent controversy suggesting no DM in elliptical galaxies may be explained by this effect, illustrating the urgent need for better constraints. We propose a 75ks Chandra exposure of NGC4649 to break this degeneracy in a carefully-chosen galaxy. Combined with our deep optical spectra and PN and GC kinematics, this will provide definitive constraints on the mass and orbital anisotropy profiles. By combining all techniques for one galaxy, this will provide a textbook example of how to overcome the degeneracy.
Frozen orbits in the J2 + J3 problem. [orbital mechanics
NASA Technical Reports Server (NTRS)
Kiedron, Krystyna; Cook, Richard
1992-01-01
An analytical derivation of frozen orbit eccentricities and their location over the range of possible orbital inclinations in the J2 + J3 problem is presented. A gravitational field with only J2 and J3 terms is considered, because the equation defining frozen orbits in this field is an algebraic equation of the third order and an analytical formula for roots of this equation exists. An equation for the frozen orbit eccentricity is derived in a convenient form using only two independent parameters: the inclination and a parameter which is the product of the ratio of the radius of the central body to the orbital semimajor axis and the ratio of the J2 and J3 coefficients. The equation is solved, and, on the basis of its roots, frozen orbits in the J2 + J3 problem are classified.
Stability of orbits in the restricted three-body problem
NASA Astrophysics Data System (ADS)
El-Sabaa, F. M. F.; Moosa, M. H. M.
1987-07-01
The equation of motion for three bodies restricted in circular orbits is written in the case of a satellite of infinitesimal mass. The domain of zero velocities of the system is obtained, and its curves are traced. The periodic orbits of the problem are found and their stability is discussed.
NASA Astrophysics Data System (ADS)
Schaefer, R. K.; Paxton, L. J.; Selby, C.; Ogorzalek, B.; Romeo, G.; Wolven, B.; Hsieh, S.-Y.
2016-05-01
We present a new model of the South Atlantic Anomaly (SAA) particle flux intensity for low Earth orbit, based a new data set, i.e., particle noise pulses in an ultraviolet photomultiplier. The data set is unique in that it provides daily monitoring of the strength of the particle radiation at a fixed altitude and local time and provides a consistent set of observations across the deep solar minimum. The observations show the following: (1) a development over the decline of solar cycle 23 into a deep solar minimum and the subsequent rise of cycle 24, (2) the slow motion drift of the SAA centroid with time at the rate—longitude drift =0.36 ± 0.06°W/yr, and latitude drift =0.16 ± 0.09°N/yr, (3) a higher particle flux at solar minimum than at solar maximum, and (4) a yearly cyclical variation. These particle rates are deduced from electric noise pulses generated in the photometers when an energetic charged particle hits the detector and causes an electron to be liberated from the detector material. The model described here can be used to monitor and even spatially predict the changes in particle fluxes seen by instruments in contemporaneous low Earth orbits through the SAA.
The antilock braking system anomaly: a drinking driver problem?
Harless, David W; Hoffer, George E
2002-05-01
Antilock braking systems (ABS) have held promise for reducing the incidence of accidents because they reduce stopping times on slippery surfaces and allow drivers to maintain steering control during emergency braking. Farmer et al. (Accident Anal. Prevent. 29 (1997) 745) provide evidence that antilock brakes are beneficial to nonoccupants: a set of 1992 model General Motors vehicles equipped with antilock brakes were involved in significantly fewer fatal crashes in which occupants of other vehicles, pedestrians, or bicyclists were killed. But, perversely, the risk of death for occupants of vehicles equipped with antilock brakes increased significantly after adoption. Farmer (Accident Anal. Prevent. 33 (2001) 361) updates the analysis for 1996- 1998 and finds a significant attenuation in the ABS anomaly. Researchers have put forward two hypotheses to explain this antilock brake anomaly: risk compensation and improper operation of antilock brake-equipped vehicles. We provide strong evidence for the improper operation hypothesis by showing that the antilock brake anomaly is confined largely to drinking drivers. Further, we show that the attenuation phenomenon occurs consistently after the first three to four years of vehicle service.
Asymptotic orbits in the ( N+1)-body ring problem
NASA Astrophysics Data System (ADS)
Papadakis, K. E.
2009-10-01
In this paper we study the asymptotic solutions of the ( N+1)-body ring planar problem, N of which are finite and ν= N-1 are moving in circular orbits around their center of masses, while the Nth+1 body is infinitesimal. ν of the primaries have equal masses m and the Nth most-massive primary, with m 0= β m, is located at the origin of the system. We found the invariant unstable and stable manifolds around hyperbolic Lyapunov periodic orbits, which emanate from the collinear equilibrium points L 1 and L 2. We construct numerically, from the intersection points of the appropriate Poincaré cuts, homoclinic symmetric asymptotic orbits around these Lyapunov periodic orbits. There are families of symmetric simple-periodic orbits which contain as terminal points asymptotic orbits which intersect the x-axis perpendicularly and tend asymptotically to equilibrium points of the problem spiraling into (and out of) these points. All these families, for a fixed value of the mass parameter β=2, are found and presented. The eighteen (more geometrically simple) families and the corresponding eighteen terminating homo- and heteroclinic symmetric asymptotic orbits are illustrated. The stability of these families is computed and also presented.
Mars Reconnaissance Orbiter In-flight Anomalies and Lessons Learned: An Update
NASA Technical Reports Server (NTRS)
Bayer, Todd J.
2008-01-01
The Mars Reconnaissance Orbiter mission has as its primary objectives: advance our understanding of the current Mars climate, the processes that have formed and modified the surface of the planet and the extent to which water has played a role in surface processes; identify sites of possible aqueous activity indicating environments that may have been or are conducive to biological activity; and thus identify and characterize sites for future landed missions; and provide forward and return relay services for current and future Mars landed assets. MRO's crucial role in the long term strategy for Mars exploration requires a high level of reliability during its 5.4 year mission. This requires an architecture which incorporates extensive redundancy and cross-strapping. Because of the distances and hence light-times involved, the spacecraft itself must be able to utilize this redundancy in responding to time-critical failures. For cases where fault protection is unable to recognize a potentially threatening condition, either due to known limitations or software flaws, intervention by ground operations is required. These aspects of MRO's design were discussed in a previous paper [Ref. 1]. This paper provides an update to the original paper, describing MRO's significant in-flight anomalies over the past year, with lessons learned for redundancy and fault protection architectures and for ground operations.
New Periodic Orbits for the n-Body Problem
NASA Astrophysics Data System (ADS)
Moore, Cristopher; Nauenberg, Michael
2006-10-01
Since the discovery of the figure-eight orbit for the three-body problem [Moore, C., 1993, Phys. Rev. Lett., 70, pp. 3675-3679] a large number of periodic orbits of the n-body problem with equal masses and beautiful symmetries have been discovered. However, most of those that have appeared in the literature are either planar or are obtained from perturbations of planar orbits. Here we exhibit a number of new three-dimensional periodic n-body orbits with equal masses and cubic symmetry, including some whose moment of inertia tensor is a scalar. We found these orbits numerically, by minimizing the action as a function of the trajectories' Fourier coefficients. We also give numerical evidence that a planar three-body orbit first found in [Hénon, M., 1976, Celest. Mech., 13, pp. 267-285], rediscovered by [Moore, 1993], and found to exist for different masses by [Nauenberg, M., 2001, Phys. Lett., 292, pp. 93-99], is dynamically stable.
Asymptotic orbits in the restricted four-body problem
NASA Astrophysics Data System (ADS)
Papadakis, K. E.
2007-07-01
This paper studies the asymptotic solutions of the restricted planar problem of four bodies, three of which are finite, moving in circular orbits around their center of masses, while the fourth is infinitesimal. Two of the primaries have equal mass and the most-massive primary is located at the origin of the system. We found the invariant unstable and stable manifolds around the hyperbolic Lyapunov periodic orbits which emanate from the collinear equilibrium points Li,i=1,…,4, as well as the invariant manifolds from the Lagrangian critical points L5 and L6. We construct numerically, applying forward and backward integration from the intersection points of the appropriate Poincaré cuts, homo- and hetero-clinic, symmetric and non-symmetric asymptotic orbits. We present the characteristic curves of the 24 families which consist of symmetric simple-periodic orbits of the problem for a fixed value of the mass parameter b. The stability of the families is computed and also presented. Sixteen families contain as terminal points asymptotic periodic orbits which intersect the x-axis perpendicularly and tend asymptotically to L5 for t→+∞ and to L6 for t→-∞, spiralling into (and out of) these points. The corresponding 16 terminating heteroclinic asymptotic orbits, for b=2, are illustrated.
A review of problems and progress in studies of satellite magnetic anomalies
NASA Technical Reports Server (NTRS)
Mayhew, M. A.; Johnson, B. D.; Wasilewski, P. J.
1985-01-01
A review is conducted of studies performed during the Magsat project. The obtained data are considered, taking into account questions of data availability, aspects of orbit attitude determination, ionospheric noise, a field model, and an anomaly field presentation. Models for interpretation are discussed, giving attention to forward modeling, and equivalent layer inverse modeling. In an evaluation of rock property constraints, the magnetic bottom is discussed along with Curie points, metamorphism and magnetization, and the direction of magnetization.
Orbits of the Kepler problem via polar reciprocals
NASA Astrophysics Data System (ADS)
Davis, E. D.
2011-12-01
Polar reciprocals of trajectories are an elegant alternative to hodographs for motion in a central force field. Their principal advantage is that the transformation from a trajectory to its polar reciprocal is its own inverse. The form of the polar reciprocals of Kepler orbits is established, and a geometrical construction is presented for the orbits of the Kepler problem starting from their polar reciprocals. No obscure knowledge of conics is required to demonstrate the validity of the method. Unlike a graphical procedure suggested by Feynman and extended by Derbes, the method based on polar reciprocals works without changes for elliptical, parabolic, and hyperbolic trajectories.
Exchange orbits in the planar 1 + 4 body problem
NASA Astrophysics Data System (ADS)
Bengochea, A.; Galán, J.; Pérez-Chavela, E.
2015-05-01
We study some doubly-symmetric orbits in the planar 1 + 2 n-body problem, that is the mass of the central body is significantly bigger than the other 2 n equal masses. The necessary and sufficient conditions for periodicity of the orbits are discussed. We also study numerically these kinds of orbits for the case n = 2. The system under study corresponds to one conformed by a planet and four satellites of equal mass. We determine a 1-parameter family of time-reversible invariant tori, related with the reversing symmetries of the equations of motion. The initial conditions of the orbits were determined by means of solving a boundary value problem with one free parameter. The numerical solution of the boundary value problem was obtained using the software AUTO. For the numerical analysis we have used the value of 3.5 × 10-4 as mass ratio of some satellite and the planet. In the computed solutions the satellites are in mean motion resonance 1:1 and they librate around a relative equilibria, that is a solution where the distances between the bodies remain constant for all time.
Tethered body problems and relative motion orbit determination
NASA Technical Reports Server (NTRS)
Eades, J. B., Jr.; Wolf, H.
1972-01-01
Selected problems dealing with orbiting tethered body systems have been studied. In addition, a relative motion orbit determination program was developed. Results from these tasks are described and discussed. The expected tethered body motions were examined, analytically, to ascertain what influence would be played by the physical parameters of the tether, the gravity gradient and orbit eccentricity. After separating the motion modes these influences were determined; and, subsequently, the effects of oscillations and/or rotations, on tether force, were described. A study was undertaken, by examining tether motions, to see what type of control actions would be needed to accurately place a mass particle at a prescribed position relative to a main vehicle. Other applications for tethers were studied. Principally these were concerned with the producing of low-level gee forces by means of stabilized tether configurations; and, the initiation of free transfer trajectories from tether supported vehicle relative positions.
NASA's Technical Handbook for Avoiding On-Orbit ESD Anomalies Due to Internal Charging Effects
NASA Technical Reports Server (NTRS)
Whittlesey, Albert; Garrett, Henry B.
1996-01-01
This paper describes NASA-HDBK-4002, "Avoiding Problems Caused by Spacecraft On-Orbit Internal Charging Effects". The handbook includes a description of internal charging and why it is of concern to spacecraft designers. It also suggests how to determine when a project needs to consider internal spacecraft charging, it contains an electron penetration depth chart, rationale for a critical electron flux criterion, a worst-case geosynchronous electron plasma spectrum, general design guidelines, quantitative design guidelines, and a typical materials characteristics list. Appendices include a listing of some environment codes, electron transport codes, a discussion of geostationary electron plasma environments, a brief description of electron beam and other materials tests, and transient susceptibility tests. The handbook will be in the web page, hftp://standards.nasa.gov. A prior document, NASA TP2361 "Design Guidelines for Assessing and controlling Spacecraft Charging Effects", 1984, is in use to describe mitigation techniques for the effects of surface charging of satellites in space plasma environments. HDBK-4002 is meant to complement 2361 and together, the pair of documents describe both cause and mitigation designs for problems caused by energetic space plasmas.
Baggie: A unique solution to an orbiter icing problem
NASA Technical Reports Server (NTRS)
Walkover, L. J.
1982-01-01
The orbiter icing problem, located in two lower surface mold line cavities, was solved. These two cavities are open during Shuttle ground operations and ascent, and are then closed after orbit insertion. If not protected, these cavities may be coated with ice, which may be detrimental to the adjacent thermal protection system (TPS) tiles if the ice breaks up during ascent, and may hinder the closing of the cavity doors if the ice does not break up. The problem of ice in these cavities was solved by the use of a passive mechanism called baggie, which is purge curtain used to enclose the cavity and is used in conjunction with gaseous nitrogen as the local purge gas. The baggie, the final solution, is unique in its simplicity, but its design and development were not. The final baggie design and its development testing are discussed. Also discussed are the baggie concepts and other solutions not used.
NASA Astrophysics Data System (ADS)
Sharaf, M. A.; Saad, A. S.
2017-10-01
In this paper, a novel analysis was established to prove how Hansen's inferior and superior partial anomalies k and k_1 can divide the elliptic orbit into two segments. The analysis depends on the departures of r (for k) and 1/r (for k1) from their minima. By these departures, we can find: (i) Transformations relating the eccentric anomaly to k and the true anomaly to k1. (ii) Expressions for k and k_1 in terms of the orbital elements. (iii) The interpretation and the intervals of definition of two moduli (X, S) related to k and k_1. (iv) The extreme values of r and the elliptic equations in terms of k and k1. (v) For r' and r'', the modulus X as a measure of the asymmetry of r' (or r'') from r'' (or r'), and the modulus S12 as a measure of the asymmetry of r' and r'' from the minimum value of r. (vi) A description of the segments represented by k and k1. (vii) The relative position of the radius vector at k0° and k1=180°.
Minimal seesaw as an ultraviolet insensitive cure for the problems of anomaly mediation
Mohapatra, R. N.; Setzer, N.; Spinner, S.
2008-03-01
We show that an intermediate scale supersymmetric left-right seesaw scenario with automatic R-parity conservation can cure the problem of tachyonic slepton masses that arise when supersymmetry is broken by anomaly mediation, while preserving ultraviolet insensitivity. The reason for this is the existence of light B-L=2 Higgses with Yukawa couplings to the charged leptons. We find these theories to have distinct predictions compared to the usual mSUGRA and gauge mediated models as well as the minimal anomaly mediated supersymmetry breaking models. Such predictions include a condensed gaugino mass spectrum and possibly a correspondingly condensed sfermion spectrum.
Quantum mechanics of hyperbolic orbits in the Kepler problem
Rauh, Alexander; Parisi, Juergen
2011-04-15
The problem of deriving macroscopic properties from the Hamiltonian of the hydrogen atom is resumed by extending previous results in the literature, which predicted elliptic orbits, into the region of hyperbolic orbits. As a main tool, coherent states of the harmonic oscillator are used which are continued to imaginary frequencies. The Kustaanheimo-Stiefel (KS) map is applied to transform the original configuration space into the product space of four harmonic oscillators with a constraint. The relation derived between real time and oscillator (pseudo) time includes quantum corrections. In the limit ({h_bar}/2{pi}){yields}0, the time-dependent mean values of position and velocity describe the classical motion on a hyperbola and a circular hodograph, respectively. Moreover, the connection between pseudotime and real time comes out in analogy to Kepler's equation for elliptic orbits. The mean-square-root deviations of position and velocity components behave similarly in time to the corresponding ones of a spreading Gaussian wave packet in free space. To check the approximate treatment of the constraint, its contribution to the mean energy is determined with the result that it is negligible except for energy values close to the parabolic orbit with eccentricity equal to 1. It is inevitable to introduce a suitable scalar product in R{sup 4} which makes both the transformed Hamiltonian and the velocity operators Hermitian. An elementary necessary criterion is given for the energy interval where the constraint can be approximated by averaging.
NASA Technical Reports Server (NTRS)
Srivastava, Ashok, N.; Akella, Ram; Diev, Vesselin; Kumaresan, Sakthi Preethi; McIntosh, Dawn M.; Pontikakis, Emmanuel D.; Xu, Zuobing; Zhang, Yi
2006-01-01
This paper describes the results of a significant research and development effort conducted at NASA Ames Research Center to develop new text mining techniques to discover anomalies in free-text reports regarding system health and safety of two aerospace systems. We discuss two problems of significant importance in the aviation industry. The first problem is that of automatic anomaly discovery about an aerospace system through the analysis of tens of thousands of free-text problem reports that are written about the system. The second problem that we address is that of automatic discovery of recurring anomalies, i.e., anomalies that may be described m different ways by different authors, at varying times and under varying conditions, but that are truly about the same part of the system. The intent of recurring anomaly identification is to determine project or system weakness or high-risk issues. The discovery of recurring anomalies is a key goal in building safe, reliable, and cost-effective aerospace systems. We address the anomaly discovery problem on thousands of free-text reports using two strategies: (1) as an unsupervised learning problem where an algorithm takes free-text reports as input and automatically groups them into different bins, where each bin corresponds to a different unknown anomaly category; and (2) as a supervised learning problem where the algorithm classifies the free-text reports into one of a number of known anomaly categories. We then discuss the application of these methods to the problem of discovering recurring anomalies. In fact the special nature of recurring anomalies (very small cluster sizes) requires incorporating new methods and measures to enhance the original approach for anomaly detection. ?& pant 0-
NASA Astrophysics Data System (ADS)
Wise, Marcie A.; Saleh, Joseph H.; Haga, Rachel A.
2011-01-01
Choosing the "right" satellite platform for a given market and mission requirements is a major investment decision for a satellite operator. With a variety of platforms available on the market from different manufacturers, and multiple offerings from the same manufacturer, the down-selection process can be quite involved. In addition, because data for on-obit failures and anomalies per platform is unavailable, incomplete, or fragmented, it is difficult to compare options and make an informed choice with respect to the critical attribute of field reliability of different platforms. In this work, we first survey a large number of geosynchronous satellite platforms by the major satellite manufacturers, and we provide a brief overview of their technical characteristics, timeline of introduction, and number of units launched. We then analyze an extensive database of satellite failures and anomalies, and develop for each platform a "health scorecard" that includes all the minor and major anomalies, and complete failures—that is failure events of different severities—observed on-orbit for each platform. We identify the subsystems that drive these failure events and how much each subsystem contributes to these events for each platform. In addition, we provide the percentage of units in each platform which have experienced failure events, and, after calculating the total number of years logged on-orbit by each platform, we compute its corresponding average failure and anomaly rate. We conclude this work with a preliminary comparative analysis of the health scorecards of different platforms. The concept of a "health scorecard" here introduced provides a useful snapshot of the failure and anomaly track record of a spacecraft platform on orbit. As such, it constitutes a useful and transparent benchmark that can be used by satellite operators to inform their acquisition choices ("inform" not "base" as other considerations are factored in when comparing different spacecraft
Practical Method to Identify Orbital Anomaly as Breakup Event in the Geostationary Region
2015-01-14
associated with the target or the other candidates. 15. SUBJECT TERMS Space Debris , Space Technology, orbit determination 16. SECURITY...fragmentation debris from a specific breakup event by using orbital debris modeling techniques. This paper explains the proposed strategy and reports...experienced abrupt orbital changes for unknown reasons. It also has been revealed in [6] that no debris clouds have been yet associated with these
Evolution of the orbit in the double-averaged planar restricted three-body problem
NASA Astrophysics Data System (ADS)
Sidlichovsky, M.
1984-03-01
The double-averaged planar three-body problem is brought to one degree of freedom. For the restricted case, the double-average Hamiltonian is independent of mean anomalies and, therefore, represents an integral of motion. This integral gives the complicated implicit relation between eccentricity e and the distance d of pericenters. The evolution of the orbit is best expressed in the x, y plane for which e, d are polar coordinates. The explicit calculations are carried out up to the fourth degree in eccentricities while the ratio sigma of the semi-major axes is taken into account in all degrees, asuming sigma less than one but not necessarily much less than one. The trajectories in the x, y plane are then ellipses. The center of each ellipse depends on energy. The ellipse degenerating into one point represents the libration point whose x coordinate may be interpreted as the forced eccentricity. The dependence of the parameters on sigma is investigated.
Wood's anomalies and surface waves in the problem of scattering by a periodic boundary. II
Kamotskii, I V; Nazarov, S A
1999-02-28
The solution of the problem of diffraction of an acoustic plane wave by a periodic boundary for frequencies close to threshold values is studied. It is shown that if the periodic structure has some special geometry, then the transformations of the diffraction pattern (Wood's anomalies) are accompanied by the occurrence of surface waves. Substantiation of asymptotic formulae is carried out on the basis of the techniques of equivalent weighted norms in Sobolev spaces.
Singular perturbation analysis of the atmospheric orbital plane change problem
NASA Technical Reports Server (NTRS)
Calise, A. J.
1988-01-01
A three-state model is presented for the aeroassisted orbital plane change problem. A further model order reduction to a single state model is examined using singular perturbation theory. The optimal solution for this single state model compares favorably with the exact numerical solution using a four-state model; however, a separate boundary layer solution is required to satisfy the terminal constraint on altitude. This, in general, involves the solution of a two-point boundary value problem, but for a two-state model. An approximation is introduced to obtain an analytical control solution for lift and bank angle. Included are numerical simulation results of a guidance law derived from this analysis, along with comparison to earlier work by other researchers.
NASA Technical Reports Server (NTRS)
Janin, G.; Bond, V. R.
1980-01-01
An independent variable different from the time for elliptic orbit integration is used. Such a time transformation provides an analytical step-size regulation along the orbit. An intermediate anomaly (an anomaly intermediate between the eccentric and the true anomaly) is suggested for optimum performances. A particular case of an intermediate anomaly (the elliptic anomaly) is defined, and its relation with the other anomalies is developed.
Modeling and Monitoring South Atlantic Anomaly in Low Earth Orbit Using SSUSI Photometric Data
NASA Astrophysics Data System (ADS)
Romeo, G.; Schaefer, R. K.; Paxton, L. J.; Wolven, B. C.; Romeo, O.
2016-12-01
High energy particles in space are a source of noise for photometric instruments. By careful treatment of this noise, we can extract a great deal of information about in situ particle fluxes (Casadio and Arino, 2011, Schaefer, et al., 2016). Here we consider the analysis of data from the Defense Meteorological Satellite Program's (DMSP) Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instrument to examine particle fluxes (Schaefer, et al., 2016). We demonstrate that the data from the SSUSI 427 nm nadir photometer can be used to effectively monitor particle fluxes from the South Atlantic Anomaly. An accurate extraction of particle information requires an understanding of both the signal (moonglow) and the noise (> 30 MeV protons). We show how this photometer can be used to monitor the shape and flux intensity of the SAA over a solar cycle. These data show the evolution of the SAA in time and space. We also describe how data from the SSUSI scanning imaging spectrograph can be used to isolate and remove particle noise in the images obtained from this spacecraft. Thus, in cases where Spacecraft Size Weight and Power (SWaP) are tightly constrained, photometric instruments can be enlisted for dual use, providing both optical imaging and particle detection. Noise counts in the SSUSI 427 nm nadir photometer binned into 2x2 square degree bins and averaged over the year 2004. Here we see the familiar intensity pattern of the South Atlantic Anomaly.
The rectilinear three-body problem using symbol sequence II: role of the periodic orbits
NASA Astrophysics Data System (ADS)
Saito, Masaya Masayoshi; Tanikawa, Kiyotaka
2009-03-01
We study the change of phase space structure of the rectilinear three-body problem when the mass combination is changed. Generally, periodic orbits bifurcate from the stable Schubart periodic orbit and move radially outward. Among these periodic orbits there are dominant periodic orbits having rotation number ( n - 2)/ n with n ≥ 3. We find that the number of dominant periodic orbits is two when n is odd and four when n is even. Dominant periodic orbits have large stable regions in and out of the stability region of the Schubart orbit (Schubart region), and so they determine the size of the Schubart region and influence the structure of the Poincaré section out of the Schubart region. Indeed, with the movement of the dominant periodic orbits, part of complicated structure of the Poincaré section follows these orbits. We find stable periodic orbits which do not bifurcate from the Schubart orbit.
Ambrosio-Gallardo, Félix; Cruz-Fuentes, Carlos; Heinze-Martin, Gerhard; Caraveo-Anduaga, Jorge; Cortés-Sotres, José
2015-01-01
Introduction Minor physical anomalies (MPA) are dysmorphic features that reflect deviations in early development, are morphological variants that appear during the first trimester of pregnancy and could be used as a marker of disease risk in susceptible people. The literature agrees that the number of MPA is higher in patients with schizophrenia compared with their relatives and healthy subjects. The purpose of this study is to compare the MPA, assessed using the Gourion Scale, in complete nuclear families (families with a member with schizophrenia and control families) by determining the MPA mean, concordance and heritability for the total score on the MPA Gourion Scale for each anomaly. Method The sample consisted of 60 families with at least one schizophrenic patient (284 members) and 61 control families (249 members). Results: The mean total score for the scale was 5.72 ± 2.3 MPA in the case of families with at least one schizophrenic patient and 1.8 ± 4.46 MPA for control families. The average for families of patients without considering the patient in the analysis was 5.59 ± 2.3 MPA; for patients, the mean was 6.14 ± 2.4 MPA. In the analysis by anomaly differences were found only in eleven anomalies found no evidence of heritability or concordance. Conclusions MPA occur more frequently in patients, but a pattern of low consistency between them persists. It is concluded that MPA could be a marker of neurodevelopmental problems, but it is not suitable to consider them a Gourion scale as endophenotype. PMID:25612094
Spin-orbit-induced resonances and threshold anomalies in a reduced-dimension Fermi gas
NASA Astrophysics Data System (ADS)
Wang, Su-Ju; Greene, Chris H.
2016-11-01
We calculate the reflection and transmission probabilities in a one-dimensional Fermi gas with an equal mixing of the Rashba and Dresselhaus spin-orbit coupling (RD-SOC) produced by an external Raman laser field. These probabilities are computed over multiple relevant energy ranges within the pseudopotential approximation. Strong scattering resonances are found whenever the incident energy approaches either a scattering threshold or a quasibound state attached to one of the energetically closed higher dispersion branches. A striking difference is demonstrated between two very different regimes set by the Raman laser intensity, namely, between scattering for the single-minimum dispersion versus the double-minimum dispersion at the lowest threshold. The presence of RD-SOC together with the Raman field fundamentally changes the scattering behavior and enables the realization of very different one-dimensional theoretical models in a single experimental setup when combined with a confinement-induced resonance.
NASA Technical Reports Server (NTRS)
Toft, Mark R.
1993-01-01
Two lots of NASA standard 50 A.H. Ni-Cd battery cells, manufactured by Gates Aerospace Batteries and built into batteries by McDonnell Douglas, have experienced significant performance problems. The two lots were used on the Compton Gamma Ray Observatory and the Upper Atmosphere Research Satellite. Both of these satellites are Low Earth Orbital (LEO) satellites containing batteries on a parallel bus charged to NASA standard V/T curves using a NASA standard power regulator. The following preliminary conclusions were reached: (1) several plate and cell parameters have migrated within their spec limits over the years (in some cases, from one extreme to the other); (2) several parametric relationships, not generally monitored and therefore not under specification control, have also migrated over the years; (3) many of these changes appear to have taken place as a natural consequence of changes in GE/GAB materials and processes; (4) several of these factors may be 'conspiring' to aggravate known cell failure mechanisms (factors such as heavier plate, less teflon and/or less-uniform teflon, and less electrolyte) but all are still in spec (where specs exist); (5) the weight of the evidence collected to characterize the anomalies and to characterize the negative electrode itself, strongly suggests that alterations to the structure, composition, uniformity, and efficiency of the negative electrode are at the heart of the battery performance problems currently being experienced; and (6) further investigation at all levels (plate, cell, battery, and system) continues to be warranted.
Investigating On-Orbit Attitude Determination Anomalies for the Solar Dynamics Observatory Mission
NASA Technical Reports Server (NTRS)
Vess, Melissa F.; Starin, Scott R.; Chia-Kuo, Alice Liu
2011-01-01
The Solar Dynamics Observatory (SDO) was launched on February 11, 2010 from Kennedy Space Center on an Atlas V launch vehicle into a geosynchronous transfer orbit. SDO carries a suite of three scientific instruments, whose observations are intended to promote a more complete understanding of the Sun and its effects on the Earth's environment. After a successful launch, separation, and initial Sun acquisition, the launch and flight operations teams dove into a commissioning campaign that included, among other things, checkout and calibration of the fine attitude sensors and checkout of the Kalman filter (KF) and the spacecraft s inertial pointing and science control modes. In addition, initial calibration of the science instruments was also accomplished. During that process of KF and controller checkout, several interesting observations were noticed and investigated. The SDO fine attitude sensors consist of one Adcole Digital Sun Sensor (DSS), two Galileo Avionica (GA) quaternion-output Star Trackers (STs), and three Kearfott Two-Axis Rate Assemblies (hereafter called inertial reference units, or IRUs). Initial checkout of the fine attitude sensors indicated that all sensors appeared to be functioning properly. Initial calibration maneuvers were planned and executed to update scale factors, drift rate biases, and alignments of the IRUs. After updating the IRU parameters, the KF was initialized and quickly reached convergence. Over the next few hours, it became apparent that there was an oscillation in the sensor residuals and the KF estimation of the IRU bias. A concentrated investigation ensued to determine the cause of the oscillations, their effect on mission requirements, and how to mitigate them. The ensuing analysis determined that the oscillations seen were, in fact, due to an oscillation in the IRU biases. The low frequencies of the oscillations passed through the KF, were well within the controller bandwidth, and therefore the spacecraft was actually
Subregions of Motion and Elliptic Halo Orbits in the Elliptic Restricted Three-Body Problem
NASA Technical Reports Server (NTRS)
Campagnola, Stefano; Lo, Martin; Newton, Paul
2008-01-01
In this paper we present regions of motion and periodic orbits in the spatial elliptic restricted three body problem (ER3BP). Periodic orbits and regions of motion are fundamental keys to understand any dynamical system; for this reason the Hill's surfaces or the families of halo orbits have been extensively studied in the frame of the circular restricted three body problem. It is our opinion that their natural extensions to the ER3BP have not been studied enough. We divide the position space into forbidden subregions, subregions of motion and low-velocity subregions.We use these notions to define necessary condition for a transfer trajectory in the ER3BP. Also we compute branches of elliptic halo orbits bifurcating from halo orbits in the circular restricted three body problem. The new periodic orbits have principal periods and stability properties different from those of the originating halo orbit.
Subregions of Motion and Elliptic Halo Orbits in the Elliptic Restricted Three-Body Problem
NASA Technical Reports Server (NTRS)
Campagnola, Stefano; Lo, Martin; Newton, Paul
2008-01-01
In this paper we present regions of motion and periodic orbits in the spatial elliptic restricted three body problem (ER3BP). Periodic orbits and regions of motion are fundamental keys to understand any dynamical system; for this reason the Hill's surfaces or the families of halo orbits have been extensively studied in the frame of the circular restricted three body problem. It is our opinion that their natural extensions to the ER3BP have not been studied enough. We divide the position space into forbidden subregions, subregions of motion and low-velocity subregions.We use these notions to define necessary condition for a transfer trajectory in the ER3BP. Also we compute branches of elliptic halo orbits bifurcating from halo orbits in the circular restricted three body problem. The new periodic orbits have principal periods and stability properties different from those of the originating halo orbit.
Radial orbit instability in systems of highly eccentric orbits: Antonov problem reviewed
NASA Astrophysics Data System (ADS)
Polyachenko, E. V.; Shukhman, I. G.
2017-09-01
Stationary stellar systems with radially elongated orbits are subject to radial orbit instability - an important phenomenon that structures galaxies. Antonov presented a formal proof of the instability for spherical systems in the limit of purely radial orbits. However, such spheres have highly inhomogeneous density distributions with singularity ∼1/r2, resulting in an inconsistency in the proof. The proof can be refined, if one considers an orbital distribution close to purely radial, but not entirely radial, which allows to avoid the central singularity. For this purpose we employ non-singular analogues of generalized polytropes elaborated recently in our work in order to derive and solve new integral equations adopted for calculation of unstable eigenmodes in systems with nearly radial orbits. In addition, we establish a link between our and Antonov's approaches and uncover the meaning of infinite entities in the purely radial case. Maximum growth rates tend to infinity as the system becomes more and more radially anisotropic. The instability takes place both for even and odd spherical harmonics, with all unstable modes developing rapidly, i.e. having eigenfrequencies comparable to or greater than typical orbital frequencies. This invalidates orbital approximation in the case of systems with all orbits very close to purely radial.
Orbits of Two-Body Problem From the Lenz Vector
ERIC Educational Resources Information Center
Caplan, S.; And Others
1978-01-01
Obtains the orbits with reference to the center of mass of two bodies under mutual universe square law interaction by use of the eccentricity vector which is equivalent to the Lenz vector within a numerical factor. (Author/SL)
Orbital stability of the restricted three-body problem in General Relativity
NASA Astrophysics Data System (ADS)
Abishev, M.; Quevedo, H.; Toktarbay, S.; Zhami, B.
We consider the problem of orbital stability of the motion of a test particle in the restricted three-body problem, by using the orbital moment and its time derivative. We show that it is possible to get some insight into the stability properties of the motion of test particles, without knowing the exact solutions of the motion equations.
Orbiting Debris: a Space Environmental Problem. Background Paper
NASA Technical Reports Server (NTRS)
1990-01-01
Artificial debris, deposited in a multitude of orbits about the Earth as the result of the exploration and use of the space environment, poses a growing hazard to future space operations. Unless nations sharply reduce the amount of orbital debris they produce, future space activites could suffer loss of capability, loss of income, and even loss of life as a result of collisions between spacecraft and debris. This background paper discusses the sources of debris and how they can be greatly reduced.
The Orbital Debris Problem and the Challenges for Environment Remediation
NASA Technical Reports Server (NTRS)
Liou, J.-C.
2013-01-01
Orbital debris scientists from major international space agencies, including JAXA and NASA, have worked together to predict the trend of the future environment. A summary presentation was given to the United Nations in February 2013. The orbital debris population in LEO will continue to increase. Catastrophic collisions will continue to occur every 5 to 9 years center dot To limit the growth of the future debris population and to better protect future spacecraft, active debris removal, should be considered.
Orbiting Debris: a Space Environmental Problem. Background Paper
NASA Technical Reports Server (NTRS)
1990-01-01
Artificial debris, deposited in a multitude of orbits about the Earth as the result of the exploration and use of the space environment, poses a growing hazard to future space operations. Unless nations sharply reduce the amount of orbital debris they produce, future space activites could suffer loss of capability, loss of income, and even loss of life as a result of collisions between spacecraft and debris. This background paper discusses the sources of debris and how they can be greatly reduced.
NASA Astrophysics Data System (ADS)
García Yárnoz, Daniel; Scheeres, Daniel J.; McInnes, Colin R.
2015-04-01
The focus of this paper is on the exploration of the and - families of planar symmetric periodic orbits around minor bodies under the effect of solar radiation pressure (SRP). An extended Hill problem with SRP allows the study of spacecraft trajectories in the vicinity of asteroids orbiting the Sun. The evolution of the and - families is presented with SRP increasing from the classical Hill problem to levels characteristic of current and future planned missions to minor bodies, as well as one extreme case with very large SRP for a small asteroid. In addition, the implications of considering a spherical body are analysed, in terms of trajectories colliding with the asteroid and eclipses, which limits the feasibility of various family branches. Finally, the influence of SRP on the linear stability of feasible orbits is calculated.
H→γγ as a Triangle Anomaly: Possible Implications for the Hierarchy Problem
de Gouvea, Andre; Kile, Jennifer; Vega-Morales, Roberto
2013-06-24
The Standard Model calculation of H→γγ has the curious feature of being finite but regulator-dependent. While dimensional regularization yields a result which respects the electromagnetic Ward identities, additional terms which violate gauge invariance arise if the calculation is done setting d = 4. This discrepancy between the d=4 – ϵ and d = 4 results is recognized as a true ambiguity which must be resolved using physics input; as dimensional regularization respects gauge invariance, the d = 4 – ϵ calculation is accepted as the correct SM result. However, here we point out another possibility; working in analogy with the gauge chiral anomaly, we note that it is possible that the individual diagrams do violate the electromagnetic Ward identities, but that the gauge-invariance-violating terms cancel when all contributions to H→γγ, both from the SM and from new physics, are included. We thus examine the consequences of the hypothesis that the d = 4 calculation is valid, but that such a cancellation occurs. We work in general renormalizable gauge, thus avoiding issues with momentum routing ambiguities. We point out that the gauge-invariance-violating terms in d = 4 arise not just for the diagram containing a SM $W^{\\pm}$ boson, but also for general fermion and scalar loops, and relate these terms to a lack of shift invariance in Higgs tadpole diagrams. We then derive the analogue of "anomaly cancellation conditions", and find consequences for solutions to the hierarchy problem. In particular, we find that supersymmetry obeys these conditions, even if it is softly broken at an arbitrarily high scale.
Al-Maghribi, Hussein
2007-09-01
A retrospective study was performed on all patients with congenital adrenal hyperplasia (CAH) who were followed up at the King Hussein Medical Center (KHMC), Amman, Jordan, during the period from January 1996 to June 2006. The aim was to evaluate the clinical features, special problems, and corrective interventions for these patients. The records of 73 children (39 were genetic females and 34 were genetic males) with CAH were reviewed in the study. The age of the patients at last follow-up was between five months and 18 years. Diagnostic criteria for CAH were typical clinical features of the illness (salt loss, dehydration, virilization, macrogenitosomia, ambiguous genitalia, and accelerated growth) and typical hormonal abnormalities (decreased serum cortisol and elevated serum 17-hydroxyprogesterone). There were 62 patients with classical presentation; among them, salt-wasting (SW) form was seen in 41 patients (66%). There were 5 patients with the nonclassic form, while 6 others had cryptic presentation. Seven patients (9%) had hypertension, mostly due to salt-retaining CAH. Among the 39 females with CAH, 27 had developed mental anomalies of the external genitalia; 20 of them underwent surgical interventions of their external genitalia. Fourteen genetically female patients were wrongly diagnosed as 'male sex' at birth due to severe virilization. Seven of them were reassigned 'female sex' socially, legally, and surgically; the parents of one of them (a four-year-old girl) wanted the surgical intervention postponed for two to three years. Hysterectomy and gonadectomy were carried out for 6 of the other 7 patients who chose to keep the male gender. Our study indicates that newborns with developmental anomalies of the external genitalia should be diagnosed as early as possible so that medical, psychological, and social complications are minimized. A neonatal screening program for such a disorder can identify infants at risk for the development of life
NASA Technical Reports Server (NTRS)
1993-01-01
This report explains the procedural anomaly that occurred during the launch sequence of an Orbital Sciences Corporation Pegasus expendable launch vehicle, which was subsequently deployed successfully from an NB-52B airplane, on 9 Feb. 1993. The safety issues discussed in the report include command, control and communications responsibility, launch crew fatigue, launch interphone procedures, efficiency of launch constraints, and the lack of common launch documents. Safety recommendations concerning these issues were made to the Department of Transportation, the National Aeronautics and Space Administration, and the Orbital Sciences Corporation.
NASA Technical Reports Server (NTRS)
1993-01-01
This report explains the procedural anomaly that occurred during the launch sequence of an Orbital Sciences Corporation Pegasus expendable launch vehicle, which was subsequently deployed successfully from an NB-52B airplane, on 9 Feb. 1993. The safety issues discussed in the report include command, control and communications responsibility, launch crew fatigue, launch interphone procedures, efficiency of launch constraints, and the lack of common launch documents. Safety recommendations concerning these issues were made to the Department of Transportation, the National Aeronautics and Space Administration, and the Orbital Sciences Corporation.
NASA Technical Reports Server (NTRS)
1993-01-01
This report explains the procedural anomaly that occurred during the launch sequence of an Orbital Sciences Corporation Pegasus expendable launch vehicle, which was subsequently deployed successfully from an NB-52B airplane, on 9 Feb. 1993. The safety issues discussed in the report include command, control and communications responsibility, launch crew fatigue, launch interphone procedures, efficiency of launch constraints, and the lack of common launch documents. Safety recommendations concerning these issues were made to the Department of Transportation, the National Aeronautics and Space Administration, and the Orbital Sciences Corporation.
A Search for Collision Orbits in the Free-Fall Three-Body Problem II
NASA Astrophysics Data System (ADS)
Tanikawa, Kiyotaka
2000-04-01
A numerical procedure to systematically find collision orbits in the planar three-body problem has been developed in the preceding paper (Tanikawa et al., 1995). Using this procedure, a search for binary and triple collision orbits has been carried out in the free-fall three-body problem. Some detailed structures of a part of the initial value space are discussed. Various interesting orbits have been found. Examples are oscillatory orbits in which ejected particles change from ejection to ejection, and orbits which are not isosceles initially but nearly isosceles after escape. Some results of isosceles problems (Simó and Martínez, 1988) are extended to non-isosceles problems.
Study of lunar gravity assist orbits in the restricted four-body problem
NASA Astrophysics Data System (ADS)
Qi, Yi; Xu, Shijie
2016-07-01
In this paper, the lunar gravity assist (LGA) orbits starting from the Earth are investigated in the Sun-Earth-Moon-spacecraft restricted four-body problem (RFBP). First of all, the sphere of influence of the Earth-Moon system (SOIEM) is derived. Numerical calculation displays that inside the SOIEM, the effect of the Sun on the LGA orbits is quite small, but outside the SOIEM, the Sun perturbation can remarkably influence the trend of the LGA orbit. To analyze the effect of the Sun, the RFBP outside the SOIEM is approximately replaced by a planar circular restricted three-body problem, where, in the latter case, the Sun and the Earth-Moon barycenter act as primaries. The stable manifolds associated with the libration point orbit and their Poincaré sections on the SOIEM are applied to investigating the LGA orbit. According to our research, the patched LGA orbits on the Poincaré sections can efficiently distinguish the transit LGA orbits from the non-transit LGA orbits under the RFBP. The former orbits can pass through the region around libration point away from the SOIEM, but the latter orbits will bounce back to the SOIEM. Besides, the stable transit probability is defined and analyzed. According to the variant requirement of the space mission, the results obtained can help us select the LGA orbit and the launch window.
NASA Astrophysics Data System (ADS)
Hood, L. L.; Spudis, P. D.
2016-11-01
Approximate maps of the lunar crustal magnetic field at low altitudes in the vicinities of the three Imbrian-aged impact basins, Orientale, Schrödinger, and Imbrium, have been constructed using Lunar Prospector and Kaguya orbital magnetometer data. Detectable anomalies are confirmed to be present well within the rims of Imbrium and Schrödinger. Anomalies in Schrödinger are asymmetrically distributed about the basin center, while a single isolated anomaly is most clearly detected within Imbrium northwest of Timocharis crater. The subsurface within these basins was heated to high temperatures at the time of impact and required long time periods (up to 1 Myr) to cool below the Curie temperature for metallic iron remanence carriers (1043 K). Therefore, consistent with laboratory analyses of returned samples, a steady, long-lived magnetizing field, i.e., a former core dynamo, is inferred to have existed when these basins formed. The asymmetrical distribution within Schrödinger suggests partial demagnetization by later volcanic activity when the dynamo field was much weaker or nonexistent. However, it remains true that anomalies within Imbrian-aged basins are much weaker than those within most Nectarian-aged basins. The virtual absence of anomalies within Orientale where impact melt rocks (the Maunder Formation) are exposed at the surface is difficult to explain unless the dynamo field was much weaker during the Imbrian period.
NASA Technical Reports Server (NTRS)
Taylor, Patrick T.
2004-01-01
Bangui anomaly is the name given to one of the Earth s largest crustal magnetic anomalies and the largest over the African continent. It covers two-thirds of the Central African Republic and therefore the name derives from the capitol city-Bangui that is also near the center of this feature. From surface magnetic survey data Godivier and Le Donche (1962) were the first to describe this anomaly. Subsequently high-altitude world magnetic surveying by the U.S. Naval Oceanographic Office (Project Magnet) recorded a greater than 1000 nT dipolar, peak-to-trough anomaly with the major portion being negative (figure 1). Satellite observations (Cosmos 49) were first reported in 1964, these revealed a 40nT anomaly at 350 km altitude. Subsequently the higher altitude (417-499km) POGO (Polar Orbiting Geomagnetic Observatory) satellite data recorded peak-to-trough anomalies of 20 nT these data were added to Cosmos 49 measurements by Regan et al. (1975) for a regional satellite altitude map. In October 1979, with the launch of Magsat, a satellite designed to measure crustal magnetic anomalies, a more uniform satellite altitude magnetic map was obtained. These data, computed at 375 km altitude recorded a -22 nT anomaly (figure 2). This elliptically shaped anomaly is approximately 760 by 1000 km and is centered at 6%, 18%. The Bangui anomaly is composed of three segments; there are two positive anomalies lobes north and south of a large central negative field. This displays the classic pattern of a magnetic anomalous body being magnetized by induction in a zero inclination field. This is not surprising since the magnetic equator passes near the center of this body.
Geostationary Orbital Crowding: An Analysis of Problems and Solutions
1990-05-16
his famous Wireless World article of 1945, entitled ’Extraterrestrial Relays,’ Arthur C. Clarke suggested that a true broadcast service giving...following paragraph as Article 33, and titled "Rational Use of the Radio Frequency Spectrum and of the Geostationary Satellite Orbit," to the ITU Convention...Books, 1988), p. 5. Figure 3.4. Regions of the International Telecomunications Union 96 Space WARC-1979 Convening in Geneva, Switzerland on the 24th of
The iterative solution of the problem of orbit determination using Chebyshev series
NASA Technical Reports Server (NTRS)
Feagin, T.
1975-01-01
A method of orbit determination is investigated which employs Picard iteration and Chebyshev series. The method is applied to the problem of determining the orbit of an earth satellite from range and range-rate observations contaminated by noise. It is shown to be readily applicable and to possess linear convergence.
Mirage in the sky: Nonthermal dark matter, gravitino problem, and cosmic ray anomalies
Dutta, Bhaskar; Sinha, Kuver; Leblond, Louis
2009-08-01
Recent anomalies in cosmic rays could be due to dark matter annihilation in our galaxy. In order to get the required large cross section to explain the data while still obtaining the right relic density, we rely on a nonstandard thermal history between dark matter freeze out and big-bang nucleosynthesis. We show that through a reheating phase from the decay of a heavy moduli or even the gravitino, we can produce the right relic density of dark matter if its self-annihilation cross section is large enough. In addition to fitting the recent data, this scenario solves the cosmological moduli and gravitino problems. We illustrate this mechanism with a specific example in the context of U(1){sub B-L} extended minimal supersymmetric standard model where supersymmetry is broken via mirage mediation. These string motivated models naturally contain heavy moduli decaying to the gravitino, whose subsequent decay to the LSP can reheat the Universe at a low temperature. The right-handed sneutrino and the B-L gaugino can both be viable dark matter candidates with a large cross section. They are leptophilic because of B-L charges. We also show that it is possible to distinguish the nonthermal from the thermal scenario (using Sommerfeld enhancement) in direct detection experiments for certain regions of parameter space.
Control and stability problems of remote orbital capture
NASA Technical Reports Server (NTRS)
Kaplan, M. H.; Nadkarni, A. A.
1975-01-01
The dynamics and control aspects of orbital capture of space objects were studied. Differential angular rates and orientation between the object and the grappler were used to investigate the effects of misalignment as well as stability and control. The control responses after capture are discussed. The feasibility of nulling combined spin and nutation of a typical satellite is demonstrated by a Lagrangian formulation to establish a baseline situation. A free-flying teleoperator (FFTO) with a dynamically unbalanced grappler is shown to be desirable because extremely adverse cyclic torques may be generated. A combined teleoperator-satellite system assuming misalignments during capture was dynamically analyzed. Related responses and stability evaluations are included.
Broad Search for Unstable Resonant Orbits in the Planar Circular Restricted Three-Body Problem
NASA Technical Reports Server (NTRS)
Anderson, Rodney L.; Campagnola, Stefano; Lantoine, Gregory
2013-01-01
Unstable resonant orbits in the circular restricted three-body problem have increasingly been used for trajectory design using optimization and invariant manifold techniques.In this study, several methods for computing these unstable resonant orbits are explored including flyby maps, continuation from two-body models, and grid searches. Families of orbits are computed focusing on the Jupiter-Europa system, and their characteristics are explored. Different parameters such as period and stability are examined for each set of resonantor bits, and the continuation of several specific orbits is explored in more detail.
Broad Search for Unstable Resonant Orbits in the Planar Circular Restricted Three-Body Problem
NASA Technical Reports Server (NTRS)
Anderson, Rodney L.; Campagnola, Stefano; Lantoine, Gregory
2013-01-01
Unstable resonant orbits in the circular restricted three-body problem have increasingly been used for trajectory design using optimization and invariant manifold techniques.In this study, several methods for computing these unstable resonant orbits are explored including flyby maps, continuation from two-body models, and grid searches. Families of orbits are computed focusing on the Jupiter-Europa system, and their characteristics are explored. Different parameters such as period and stability are examined for each set of resonantor bits, and the continuation of several specific orbits is explored in more detail.
NASA Technical Reports Server (NTRS)
Chesler, L.; Pierce, S.
1971-01-01
Generalized, cyclic, and modified multistep numerical integration methods are developed and evaluated for application to problems of satellite orbit computation. Generalized methods are compared with the presently utilized Cowell methods; new cyclic methods are developed for special second-order differential equations; and several modified methods are developed and applied to orbit computation problems. Special computer programs were written to generate coefficients for these methods, and subroutines were written which allow use of these methods with NASA's GEOSTAR computer program.
Engineering calculations for solving the orbital allotment problem
NASA Technical Reports Server (NTRS)
Reilly, C.; Walton, E. K.; Mount-Campbell, C.; Caldecott, R.; Aebker, E.; Mata, F.
1988-01-01
Four approaches for calculating downlink interferences for shaped-beam antennas are described. An investigation of alternative mixed-integer programming models for satellite synthesis is summarized. Plans for coordinating the various programs developed under this grant are outlined. Two procedures for ordering satellites to initialize the k-permutation algorithm are proposed. Results are presented for the k-permutation algorithms. Feasible solutions are found for 5 of the 6 problems considered. Finally, it is demonstrated that the k-permutation algorithm can be used to solve arc allotment problems.
A two parameter survey of periodic orbits in the restricted problem of three bodies
NASA Technical Reports Server (NTRS)
Shelus, P. J.
1975-01-01
Within the context of the restricted problem of three bodies the effects caused by varying the mass ratio of the primaries and the eccentricity of their orbits, upon periodic orbits of the infinitesimal mass which are numerical continuations of circular orbits in the ordinary problem of two bodies are shown. A recursive power series technique is used to numerically integrate the equations of motion as well as the first variational equations in order to generate a two parameter family of perodic orbits and identify the linear stability characteristics. Seven such families are investigated with equally spaced mass ratios from 0.0 to 1.0 and eccentricities of the orbits of the primaries in a range 0.0 to 0.6. Stable orbits are associated with large distances of the infinitesimal mass from the perturbing primary, nearly circular motion of the primaries, and small mass ratios of the primaries. Unstable orbits for the infinitesimal mass are associated with small distances from the perturbing primary, highly elliptic orbits of the primaries and large mass ratios.
The Orbital Debris Problem and the Challenges for Environment Remediation
NASA Technical Reports Server (NTRS)
Liou, J.-C.
2014-01-01
LEO debris population will continue to increase even with a good implementation of the commonly-adopted mitigation measures. The root-cause of the increase is catastrophic collisions involving large/massive intact objects (rocket bodies or spacecraft). The major mission-ending risks for most operational spacecraft, however, come from impacts with debris just above the threshold of the protection shields (5-mm to 1-cm). A solution-driven approach is to seek: Concepts for removal of massive intacts with high P(collision); Concepts capable of preventing collisions involving intacts; Concepts for removal of 5-mm to 1-cm debris; Enhanced impact protection shields for valuable space assets. Key questions for remediation consideration of orbital debris: What is the acceptable threat level? What are the mission objectives? What is the appropriate roadmap/timeframe for remediation? Support advanced technology development when an economically viable approach is identified. Address non-technical issues, such as policy, coordination, ownership, legal, and liability at the national and international levels.
Constructive-analytical solution of the problem of the secular evolution of polar satellite orbits
NASA Astrophysics Data System (ADS)
Vashkov'yak, M. A.
2017-07-01
The well-known twice-averaged Hill problem is considered by taking into account the oblateness of the central body. This problem has several integrable cases that have been studied qualitatively by many scientists, beginning with M.L. Lidov and Y. Kozai. However, no rigorous analytical solution can be obtained in these cases due to the complexity of the integrals. This paper is devoted to studying the case where the equatorial plane of the central body coincides with the plane of its orbital motion relative to the perturbing body, while the satellite itself moves in a polar orbit. A more detailed qualitative study is performed, and an approximate constructive-analytical solution of the evolution system in the form of explicit time dependences of the eccentricity and pericenter argument of the satellite orbit is proposed. The methodical accuracy for the polar orbits of lunar satellites has been estimated by comparison with the numerical solution of the system.
A New Guidance Method for a Delta V and Re-entry Constrained Orbit Transfer Problem
2005-06-01
velocity, and time for these paths was first determined by Johannes Kepler in the year 1619. Rendezvous is a similar class of problem. Instead of a...orbit defined by these values would satisfy the boundary conditions if two-body ( Kepler ) propagation of the state (r1,v1) for ∆t results in a final 34...It was first characterized by Johannes Lambert in 1761. Lambert discovered a relationship between the geometry of the orbit transfer and the transfer
The existence of transversal homoclinic orbits in a planar circular restricted four-body problem
NASA Astrophysics Data System (ADS)
She, Zhikun; Cheng, Xuhua; Li, Cuiping
2013-03-01
In this paper, we study the existence of transversal homoclinic orbits in a planar circular restricted four-body problem, based on the perturbation theory of integrable Hamiltonian systems. We start from a planar circular restricted four-body model and regard it as a perturbation of the two-body model. Then, in order to conveniently study unbounded orbits, we transform the infinite points to finite points by a non-canonical transformation, arriving at a non-Hamiltonian system with degenerate fixed points. According to the extended Melnikov method, we finally prove that there exist transversal homoclinic orbits in this four-body model.
A multi-satellite orbit determination problem in a parallel processing environment
NASA Technical Reports Server (NTRS)
Deakyne, M. S.; Anderle, R. J.
1988-01-01
The Engineering Orbit Analysis Unit at GE Valley Forge used an Intel Hypercube Parallel Processor to investigate the performance and gain experience of parallel processors with a multi-satellite orbit determination problem. A general study was selected in which major blocks of computation for the multi-satellite orbit computations were used as units to be assigned to the various processors on the Hypercube. Problems encountered or successes achieved in addressing the orbit determination problem would be more likely to be transferable to other parallel processors. The prime objective was to study the algorithm to allow processing of observations later in time than those employed in the state update. Expertise in ephemeris determination was exploited in addressing these problems and the facility used to bring a realism to the study which would highlight the problems which may not otherwise be anticipated. Secondary objectives were to gain experience of a non-trivial problem in a parallel processor environment, to explore the necessary interplay of serial and parallel sections of the algorithm in terms of timing studies, to explore the granularity (coarse vs. fine grain) to discover the granularity limit above which there would be a risk of starvation where the majority of nodes would be idle or under the limit where the overhead associated with splitting the problem may require more work and communication time than is useful.
Repeat Ground Track Lunar Orbits in the Full-Potential Plus Third-Body Problem
NASA Technical Reports Server (NTRS)
Russell, Ryan P.; Lara, Martin
2006-01-01
A high degree and order Lunar gravitational field is superimposed on the Earth-Moon Restricted Three Body model to capture the dominating forces on a spacecraft in the vicinity of the Moon. For the synchronously rotating Moon, periodic orbits in this model map repeat ground tracks and represent higher order solutions to the frozen orbit problem. The near-circular, stable or near-stable solutions are found over a wide range of defining characteristics making them suitable for long-lifetime parking applications such as science orbits, crew exploration vehicle parking orbits, and global coverage constellation orbits. A full ephemeris is considered for selected orbits to evaluate the validity of the time-invariant, simplified model. Of the most promising results are the low-altitude families of near-circular, inclined orbits that maintain long-term stability despite the highly non-spherical Lunar gravity. The method is systematic and enables rapid design and analysis of long-life orbits around any tidally-locked celestial body with an arbitrarily high degree and order spherical harmonic gravity field. .
Minesaki, Yukitaka
2015-01-01
We propose the discrete-time restricted four-body problem (d-R4BP), which approximates the orbits of the restricted four-body problem (R4BP). The d-R4BP is given as a special case of the discrete-time chain regularization of the general N-body problem published in Minesaki. Moreover, we analytically prove that the d-R4BP yields the correct orbits corresponding to the elliptic relative equilibrium solutions of the R4BP when the three primaries form an equilateral triangle at any time. Such orbits include the orbit of a relative equilibrium solution already discovered by Baltagiannis and Papadakis. Until the proof in this work, there has been no discrete analog that preserves the orbits of elliptic relative equilibrium solutions in the R4BP. For a long time interval, the d-R4BP can precisely compute some stable periodic orbits in the Sun–Jupiter–Trojan asteroid–spacecraft system that cannot necessarily be reproduced by other generic integrators.
NASA Astrophysics Data System (ADS)
Minesaki, Yukitaka
2015-01-01
We propose the discrete-time restricted four-body problem (d-R4BP), which approximates the orbits of the restricted four-body problem (R4BP). The d-R4BP is given as a special case of the discrete-time chain regularization of the general N-body problem published in Minesaki. Moreover, we analytically prove that the d-R4BP yields the correct orbits corresponding to the elliptic relative equilibrium solutions of the R4BP when the three primaries form an equilateral triangle at any time. Such orbits include the orbit of a relative equilibrium solution already discovered by Baltagiannis and Papadakis. Until the proof in this work, there has been no discrete analog that preserves the orbits of elliptic relative equilibrium solutions in the R4BP. For a long time interval, the d-R4BP can precisely compute some stable periodic orbits in the Sun-Jupiter-Trojan asteroid-spacecraft system that cannot necessarily be reproduced by other generic integrators.
A Search for Collision Orbits in the Free-Fall Three-Body Problem. I. Numerical Procedure
NASA Astrophysics Data System (ADS)
Tanikawa, Kiyotaka; Umehara, Hiroaki; Abe, Hiroshi
1995-12-01
A numerical procedure is devised to find binary collision orbits in the free-fall three-body problem. Applying this procedure, families of binary collision orbits are found and a sequence of triple collision orbits are positioned. A property of sets of binary collision orbits which is convenient to search triple collision orbits is found. Important numerical results are formulated and summarized in the final section.
NASA Technical Reports Server (NTRS)
Vaughan, William W.; Friedman, Mark J.; Monteiro, Anand C.
1993-01-01
In earlier papers, Doedel and the authors have developed a numerical method and derived error estimates for the computation of branches of heteroclinic orbits for a system of autonomous ordinary differential equations in R(exp n). The idea of the method is to reduce a boundary value problem on the real line to a boundary value problem on a finite interval by using a local (linear or higher order) approximation of the stable and unstable manifolds. A practical limitation for the computation of homoclinic and heteroclinic orbits has been the difficulty in obtaining starting orbits. Typically these were obtained from a closed form solution or via a homotopy from a known solution. Here we consider extensions of our algorithm which allow us to obtain starting orbits on the continuation branch in a more systematic way as well as make the continuation algorithm more flexible. In applications, we use the continuation software package AUTO in combination with some initial value software. The examples considered include computation of homoclinic orbits in a singular perturbation problem and in a turbulent fluid boundary layer in the wall region problem.
Regularization and computational methods for precise solution of perturbed orbit transfer problems
NASA Astrophysics Data System (ADS)
Woollands, Robyn Michele
The author has developed a suite of algorithms for solving the perturbed Lambert's problem in celestial mechanics. These algorithms have been implemented as a parallel computation tool that has broad applicability. This tool is composed of four component algorithms and each provides unique benefits for solving a particular type of orbit transfer problem. The first one utilizes a Keplerian solver (a-iteration) for solving the unperturbed Lambert's problem. This algorithm not only provides a "warm start" for solving the perturbed problem but is also used to identify which of several perturbed solvers is best suited for the job. The second algorithm solves the perturbed Lambert's problem using a variant of the modified Chebyshev-Picard iteration initial value solver that solves two-point boundary value problems. This method converges over about one third of an orbit and does not require a Newton-type shooting method and thus no state transition matrix needs to be computed. The third algorithm makes use of regularization of the differential equations through the Kustaanheimo-Stiefel transformation and extends the domain of convergence over which the modified Chebyshev-Picard iteration two-point boundary value solver will converge, from about one third of an orbit to almost a full orbit. This algorithm also does not require a Newton-type shooting method. The fourth algorithm uses the method of particular solutions and the modified Chebyshev-Picard iteration initial value solver to solve the perturbed two-impulse Lambert problem over multiple revolutions. The method of particular solutions is a shooting method but differs from the Newton-type shooting methods in that it does not require integration of the state transition matrix. The mathematical developments that underlie these four algorithms are derived in the chapters of this dissertation. For each of the algorithms, some orbit transfer test cases are included to provide insight on accuracy and efficiency of these
Two impulse trajectory optimization for the RAE-B orbit trim problem
NASA Technical Reports Server (NTRS)
Payne, M. H.; Pines, S.; Horsewood, J. L.
1972-01-01
The results are reported of work on an appropriate approach to the solution of the optimum two-impulse transfer problem between orbits of specified inclination. The task included a literature search to identify the current state of the art and a definition of the suggested approach for the specific application of a lunar orbit trim. The applications of the results to the problem are included. The formulation for a computer program developed under this task following a more conventional approach is also included.
Coorbital Restricted Problem and its Application in the Design of the Orbits of the LISA Spacecraft
NASA Astrophysics Data System (ADS)
Yi, Zhaohua; Li, Guangyu; Heinzel, Gerhard; Rüdiger, Albrecht; Jennrich, Oliver; Wang, Li; Xia, Yan; Zeng, Fei; Zhao, Haibin
On the basis of many coorbital phenomena in astronomy and spacecraft motion, a dynamics model is proposed in this paper — treating the coorbital restricted problem together with method for obtaining a general approximate solution. The design of the LISA spacecraft orbits is a special 2+3 coorbital restricted problem. The problem is analyzed in two steps. First, the motion of the barycenter of the three spacecraft is analyzed, which is a planar coorbital restricted three-body problem. And an approximate analytical solution of the radius and the argument of the center is obtained consequently. Secondly, the configuration of the three spacecraft with minimum arm-length variation is analyzed. The motion of a single spacecraft is a near-planar coorbital restricted three-body problem, allowing approximate analytical solutions for the orbit radius and the argument of a spacecraft. Thus approximative expressions for the arm-length are given.
Continuation of periodic orbits in the Sun-Mercury elliptic restricted three-body problem
NASA Astrophysics Data System (ADS)
Peng, Hao; Bai, Xiaoli; Xu, Shijie
2017-06-01
Starting from resonant Halo orbits in the Circular Restricted Three-Body Problem (CRTBP), Multi-revolution Elliptic Halo (ME-Halo) orbits around L1 and L2 points in the Sun-Mercury Elliptic Restricted Three-Body Problem (ERTBP) are generated systematically. Three pairs of resonant parameters M5N2, M7N3 and M9N4 are tested. The first pair shows special features and is investigated in detail. Three separated characteristic curves of periodic orbit around each libration point are obtained, showing the eccentricity varies non-monotonically along these curves. The eccentricity of the Sun-Mercury system can be achieved by continuation method in just a few cases. The stability analysis shows that these orbits are all unstable and the complex instability occurs with certain parameters. This paper shows new periodic orbits in both the CRTBP and the ERTBP. Totally four periodic orbits with parameters M5N2 around each libration points are extracted in the Sun-Mercury ERTBP.
Solution of the flyby problem for large space debris at sun-synchronous orbits
NASA Astrophysics Data System (ADS)
Baranov, A. A.; Grishko, D. A.; Medvedevskikh, V. V.; Lapshin, V. V.
2016-05-01
the paper considers the flyby problem related to large space debris (LSD) objects at low earth orbits. The data on the overall dimensions of known last and upper stages of launch vehicles makes it possible to single out five compact groups of such objects from the NORAD catalog in the 500-2000 km altitude interval. The orbits of objects of each group have approximately the same inclinations. The features of the mutual distribution of the orbital planes of LSD objects in the group are shown in a portrait of the evolution of deviations of the right ascension of ascending nodes (RAAN). In the case of the first three groups (inclinations of 71°, 74°, and 81°), the straight lines of relative RAAN deviations of object orbits barely intersect each other. The fourth (83°) and fifth (97°-100°) LSD groups include a considerable number of objects whose orbits are described by straight lines (diagonals), which intersect other lines many times. The use of diagonals makes it possible to significantly reduce the temporal and total characteristic velocity expenditures required for object flybys, but it complicates determination of the flyby sequence. Diagonal solutions can be obtained using elements of graph theory. A solution to the flyby problem is presented for the case of group 5, formed of LSD objects at sun-synchronous orbits.
Orbiter LH2 Feedline Flowliner Cracking Problem. Version 1.0
NASA Technical Reports Server (NTRS)
Harris, Charles E.; Cragg, Clinton H.; Raju, Ivatury S.; Elliot, Kenny B.; Madaras, Eric I.; Piascik, Robert S.; Halford, Gary R.; Bonacuse, Peter J.; Sutliff, Daniel L.; Bakhle, Milind A.
2005-01-01
In May of 2002, three cracks were found in the downstream flowliner at the gimbal joint in the LH2 feedline at the interface with the Low Pressure Fuel Turbopump (LPFP) of Space Shuttle Main Engine (SSME) #1 of Orbiter OV-104. Subsequent inspections of the feedline flowliners in the other orbiters revealed the existence of 8 additional cracks. No cracks were found in the LO2 feedline flowliners. A solution to the cracking problem was developed and implemented on all orbiters. The solution included weld repair of all detectable cracks and the polishing of all slot edges to remove manufacturing discrepancies that could initiate new cracks. Using the results of a fracture mechanics analysis with a scatter factor of 4 on the predicted fatigue life, the orbiters were cleared for return to flight with a one-flight rationale requiring inspections after each flight. OV-104 flew mission STS-112 and OV-105 flew mission STS-113. The post-flight inspections did not find any cracks in the repaired flowliners. At the request of the Orbiter Program, the NESC conducted an assessment of the Orbiter LH2 Feedline Flowliner cracking problem with a team of subject matter experts from throughout NASA.
Non-singular orbital elements for special perturbations in the two-body problem
NASA Astrophysics Data System (ADS)
Baù, Giulio; Bombardelli, Claudio; Peláez, Jesús; Lorenzini, Enrico
2015-12-01
Seven spatial elements and a time element are proposed as the state variables of a new special perturbation method for the two-body problem. The new elements hold for zero eccentricity and inclination and for negative values of the total energy. They are developed by combining a spatial transformation into projective coordinates (as in the Burdet-Ferrándiz regularization) with a time transformation in which the exponent of the orbital radius is equal to one instead of two (as commonly done in the literature). By following this approach, we discover a new linearization of the two-body problem, from which the orbital elements can be generated by the variation of parameters method. The geometrical significance of the spatial quantities is revealed by a new intermediate frame which differs from a local vertical local horizontal frame by one rotation in the instantaneous orbital plane. Four elements parametrize the attitude in space of this frame, which in turn defines the orientation of the orbital plane and fixes the departure direction for the longitude of the propagated body. The remaining three elements determine the motion along the radial unit vector and the orbital longitude. The performance of the method, tested using a series of benchmark orbit propagation scenarios, is extremely good when compared to several regularized formulations, some of which have been modified and improved here for the first time.
Computation of homoclinic solutions to periodic orbits in a reduced water-wave problem
NASA Astrophysics Data System (ADS)
Champneys, A. R.; Lord, G. J.
1997-02-01
This paper concerns homoclinic solutions to periodic orbits in a fourth-order Hamiltonian system arising from a reduction of the classical water-wave problem in the presence of surface tension. These solutions correspond to travelling solitary waves which converge to non-decaying ripples at infinity. An analytical result of Amick and Toland (1992), showing the existence of such homoclinic orbits to small-amplitude periodic orbits in a singular limit, is extended numerically. Also, a related result by Amick and McLeod (1991), showing the non-existence of homoclinic solutions to zero, is motivated geometrically. A general boundary-value method is constructed for continuation of homoclinic orbits to periodic orbits in Hamiltonian and reversible systems. Numerical results are presented using the path-following software AUTO, showing that the Amick-Toland solutions persist well away from the singular limit and for large-amplitude periodic orbits. Special account is taken of the phase shift between the two periodic solutions in the asymptotic limits. Furthermore, new multi-modal homoclinic solutions to periodic orbits are shown to exist under a transversality hypothesis, which is verified a posteriori by explicit computation. Continuation of these new solutions reveals limit points with respect to the singular parameter.
Symbol sequences and orbits of the free-fall three-body problem
NASA Astrophysics Data System (ADS)
Tanikawa, Kiyotaka; Mikkola, Seppo
2015-12-01
Using the symbols and symbol sequences along the orbits introduced in our preceding work, we numerically study the orbital structure of the free-fall three-body problem. We confirm and re-interpret the results obtained by us before. We describe the overall structure of the plane. It turns out that the structures of the initial condition plane can be systematically obtained with symbol sequences. Then, we obtain the structure of two interesting local regions: the isosceles and collinear boundaries of the plane. We present sequences of triple collision orbits and periodic orbits on these boundaries. We additionally argue that stable and/or unstable manifolds of the two-body collision manifolds connect different triple collision manifolds.
Resolving the timing problem of the globular clusters orbiting the Fornax dwarf galaxy
NASA Astrophysics Data System (ADS)
Angus, G. W.; Diaferio, A.
2009-06-01
We re-investigate the old problem of the survival of the five globular clusters (GCs) orbiting the Fornax dwarf galaxy in both standard and modified Newtonian dynamics (MOND). For the first time in the history of the topic, we use accurate mass models for the Fornax dwarf, obtained through Jeans modelling of the recently published line-of-sight (LOS) velocity dispersion data, and we are also not resigned to circular orbits for the GCs. Previously conceived problems stem from fixing the starting distances of the globulars to be less than half the tidal radius. We relax this constraint since there is absolutely no evidence for it and show that the dark matter (DM) paradigm, with either cusped or cored DM profiles, has no trouble sustaining the orbits of the two least massive GCs for a Hubble time almost regardless of their initial distance from Fornax. The three most massive globulars can remain in orbit as long as their starting distances are marginally outside the tidal radius. The outlook for MOND is also not nearly as bleak as previously reported. Although dynamical friction (DF) inside the tidal radius is far stronger in MOND, outside DF is negligible due to the absence of stars. This allows highly radial orbits to survive, but more importantly circular orbits at distances more than 85 per cent of Fornax's tidal radius to survive indefinitely. The probability of the GCs being on circular orbits at this distance compared with their current projected distances is discussed and shown to be plausible. Finally, if we ignore the presence of the most massive globular (giving it a large LOS distance), we demonstrate that the remaining four globulars can survive within the tidal radius for the Hubble time with perfectly sensible orbits.
Bifurcations of the Lagrangian orbits from the classical to the curved 3-body problem
NASA Astrophysics Data System (ADS)
Diacu, Florin
2016-11-01
We consider the 3-body problem of celestial mechanics in Euclidean, elliptic, and hyperbolic spaces and study how the Lagrangian (equilateral) relative equilibria bifurcate when the Gaussian curvature varies. We thus prove the existence of new classes of orbits. In particular, we find some families of isosceles triangles, which occur in elliptic space.
NASA Astrophysics Data System (ADS)
Hanson, Robert M.
2003-06-01
ORBITAL requires the following software, which is available for free download from the Internet: Netscape Navigator, version 4.75 or higher, or Microsoft Internet Explorer, version 5.0 or higher; Chime Plug-in, version compatible with your OS and browser (available from MDL).
DIRECT IMAGING IN THE HABITABLE ZONE AND THE PROBLEM OF ORBITAL MOTION
Males, Jared R.; Skemer, Andrew J.; Close, Laird M.
2013-07-01
High contrast imaging searches for exoplanets have been conducted on 2.4-10 m telescopes, typically at H band (1.6 {mu}m) and used exposure times of {approx}1 hr to search for planets with semi-major axes of {approx}> 10 AU. We are beginning to plan for surveys using extreme-AO systems on the next generation of 30 m class telescopes, where we hope to begin probing the habitable zones (HZs) of nearby stars. Here we highlight a heretofore ignorable problem in direct imaging: planets orbit their stars. Under the parameters of current surveys, orbital motion is negligible over the duration of a typical observation. However, this motion is not negligible when using large diameter telescopes to observe at relatively close stellar distances (1-10 pc), over the long exposure times (10-20 hr) necessary for direct detection of older planets in the HZ. We show that this motion will limit our achievable signal-to-noise ratio and degrade observational completeness. Even on current 8 m class telescopes, orbital motion will need to be accounted for in an attempt to detect HZ planets around the nearest Sun-like stars {alpha} Cen A and B, a binary system now known to harbor at least one planet. Here we derive some basic tools for analyzing this problem, and ultimately show that the prospects are good for de-orbiting a series of shorter exposures to correct for orbital motion.
Families of periodic orbits in the planar Hill's four-body problem
NASA Astrophysics Data System (ADS)
Burgos-García, Jaime
2016-11-01
In this work we perform numerical explorations of some families of planar periodic orbits in the Hill approximation of the restricted four-body problem. This approximation is obtained by performing a symplectic scaling which sends the two massive bodies to infinity, by the means of expanding the potential as a power series depending on the mass of the smallest primary, and taking the limit as this mass tends to zero. The limiting Hamiltonian depends only on the relative mass of the second smallest primary. The resulting dynamics shares similarities with both the restricted three-body problem and the restricted four-body problem. We focus on certain families of symmetric periodic orbits of the infinitesimal particle, for some values of the mass parameter. We explore the evolution of these families as the Jacobi constant, or, equivalently, the energy, is varied continuously, and provide details on the horizontal and vertical stability of each family.
Analysis of optimal and near-optimal continuous-thrust transfer problems in general circular orbit
NASA Astrophysics Data System (ADS)
Kéchichian, Jean A.
2009-09-01
A pair of practical problems in optimal continuous-thrust transfer in general circular orbit is analyzed within the context of analytic averaging for rapid computations leading to near-optimal solutions. The first problem addresses the minimum-time transfer between inclined circular orbits by proposing an analytic solution based on a split-sequence strategy in which the equatorial inclination and node controls are done separately by optimally selecting the intermediate orbit size at the sequence switch point that results in the minimum-time transfer. The consideration of the equatorial inclination and node state variables besides the orbital velocity variable is needed to further account for the important J2 perturbation that precesses the orbit plane during the transfer, unlike the thrust-only case in which it is sufficient to consider the relative inclination and velocity variables thus reducing the dimensionality of the system equations. Further extensions of the split-sequence strategy with analytic J2 effect are thus possible for equal computational ease. The second problem addresses the maximization of the equatorial inclination in fixed time by adopting a particular thrust-averaging scheme that controls only the inclination and velocity variables, leaving the node at the mercy of the J2 precession, providing robust fast-converging codes that lead to efficient near-optimal solutions. Example transfers for both sets of problems are solved showing near-optimal features as far as transfer time is concerned, by directly comparing the solutions to "exact" purely numerical counterparts that rely on precision integration of the raw unaveraged system dynamics with continuously varying thrust vector orientation in three-dimensional space.
Periodic orbits in the free-fall three-body problem
NASA Astrophysics Data System (ADS)
Orlov, V. V.; Titov, V. A.; Shombina, L. A.
2016-12-01
Periodic solutions of the general free-fall three-body problem are investigated for the case of equal masses. The initial conditions are chosen on a Hill surface in form space. The use of the form space reduces the dimension of the problem and makes it possible to represent the region of possible initial conditions on the Hill surface, together with a color scale. The regions obtained can be used to improve the precision of the initial conditions for the periodic orbits in the free-fall three-body problem.
On the period of the periodic orbits of the restricted three body problem
NASA Astrophysics Data System (ADS)
Perdomo, Oscar
2017-09-01
We will show that the period T of a closed orbit of the planar circular restricted three body problem (viewed on rotating coordinates) depends on the region it encloses. Roughly speaking, we show that, 2 T=kπ +\\int _Ω g where k is an integer, Ω is the region enclosed by the periodic orbit and g:R^2→ R is a function that only depends on the constant C known as the Jacobian constant; it does not depend on Ω . This theorem has a Keplerian flavor in the sense that it relates the period with the space "swept" by the orbit. As an application we prove that there is a neighborhood around L_4 such that every periodic solution contained in this neighborhood must move clockwise. The same result holds true for L_5.
Classification of periodic orbits in the four- and five-body problems.
Broucke, Roger A
2004-05-01
The research described in this paper was motivated by the new types of periodic solutions that were recently discovered by Moore, Chenciner, Montgomery, and Simo in the three-body and the N-body problem (with large N). We attempt to classify the various types of periodic orbits, in the inertial frame, on the basis of an extensive numerical exploration. We have started an exploration of the four-body problem, where the classification of types of periodic orbits is more involved. We immediately found those orbits with symmetry with respect to the x-axis, the y-axis, or both. Complete quadruple interplay, or a triple system around a single mass is possible. Finally, what seems to be the most frequent, two binary systems in orbit around the general center of mass. However, the last group can be separated into several subgroups. We have, for instance, the case of two masses on one orbit and the two other masses on another orbit. This is again a partial choreography. We then have the case of double binary choreographies: two binary systems in which all four masses travel on one single curve. To realize this situation, a certain commensurability is needed between the overall period and the period of each binary system. The binary system makes an odd integer number, q, of revolutions during a general period. We computed many cases from q = 5 to 97. This indicates that we have a discrete infinity of choreographies. The choreography q = 5 is an especially remarkable star-shaped curve. Actually, we have two such infinite families, one with corotational and the other with contrarotational motions. We show that they can be justified by simple Keplerian approximations. Finally, we mention that our work depends heavily on the existence of symmetries. They simplify the algorithms for finding periodic orbits and they play an important role in the classification. In the four-body problem with equal masses, we have five different types of symmetries. In addition to the well
Periodic orbits for space-based reflectors in the circular restricted three-body problem
NASA Astrophysics Data System (ADS)
Salazar, F. J. T.; McInnes, C. R.; Winter, O. C.
2017-05-01
The use of space-based orbital reflectors to increase the total insolation of the Earth has been considered with potential applications in night-side illumination, electric power generation and climate engineering. Previous studies have demonstrated that families of displaced Earth-centered and artificial halo orbits may be generated using continuous propulsion, e.g. solar sails. In this work, a three-body analysis is performed by using the circular restricted three body problem, such that, the space mirror attitude reflects sunlight in the direction of Earth's center, increasing the total insolation. Using the Lindstedt-Poincaré and differential corrector methods, a family of halo orbits at artificial Sun-Earth L_2 points are found. It is shown that the third order approximation does not yield real solutions after the reflector acceleration exceeds 0.245 mm s^{-2}, i.e. the analytical expressions for the in- and out-of-plane amplitudes yield imaginary values. Thus, a larger solar reflector acceleration is required to obtain periodic orbits closer to the Earth. Derived using a two-body approach and applying the differential corrector method, a family of displaced periodic orbits close to the Earth are therefore found, with a solar reflector acceleration of 2.686 mm s^{-2}.
Periodic orbits for space-based reflectors in the circular restricted three-body problem
NASA Astrophysics Data System (ADS)
Salazar, F. J. T.; McInnes, C. R.; Winter, O. C.
2016-11-01
The use of space-based orbital reflectors to increase the total insolation of the Earth has been considered with potential applications in night-side illumination, electric power generation and climate engineering. Previous studies have demonstrated that families of displaced Earth-centered and artificial halo orbits may be generated using continuous propulsion, e.g. solar sails. In this work, a three-body analysis is performed by using the circular restricted three body problem, such that, the space mirror attitude reflects sunlight in the direction of Earth's center, increasing the total insolation. Using the Lindstedt-Poincaré and differential corrector methods, a family of halo orbits at artificial Sun-Earth L_2 points are found. It is shown that the third order approximation does not yield real solutions after the reflector acceleration exceeds 0.245 mm s^{-2} , i.e. the analytical expressions for the in- and out-of-plane amplitudes yield imaginary values. Thus, a larger solar reflector acceleration is required to obtain periodic orbits closer to the Earth. Derived using a two-body approach and applying the differential corrector method, a family of displaced periodic orbits close to the Earth are therefore found, with a solar reflector acceleration of 2.686 mm s^{-2}.
Lissajous and Halo Orbits in the Restricted Three-Body Problem
NASA Astrophysics Data System (ADS)
Celletti, Alessandra; Pucacco, Giuseppe; Stella, Danilo
2015-04-01
We study the dynamics near the collinear Lagrangian points of the spatial, circular, restricted three-body problem. Following a standard procedure, we reduce the system to the center manifold and we analyze the Lissajous orbits as well as the halo orbits, the latter ones arising from bifurcations of the planar Lyapunov family of periodic orbits. To obtain the Lissajous orbits, we perform a classical perturbation theory and we provide a formal approximate solution under suitable non-degeneracy and non-resonance conditions. As for the halo orbits, we construct a normal form adapted to the synchronous resonance: introducing a detuning, measuring the displacement from the resonance, and expanding the energy in series of the detuning, we are able to evaluate the energy level at which the bifurcation takes place. Except for a particular case, the analytical values obtained after a second order resonant perturbation theory are in very good agreement (in some cases up to the fourth decimal digit) with the numerical values found in the literature.
Doubly-symmetric horseshoe orbits in the general planar three-body problem
NASA Astrophysics Data System (ADS)
Bengochea, Abimael; Galán, Jorge; Pérez-Chavela, Ernesto
2013-12-01
We present some results about the continuation of doubly-symmetric horseshoe orbits in the general planar three-body problem. This is done by means of solving a boundary value problem with one free parameter which is the quotient of the masses of two bodies μ 3= m 3/ m 1, keeping constant μ 2= m 2/ m 1 ( m 1 represents the mass of a big planet whereas m 2 and m 3 of minor bodies). For the numerical continuation of the horseshoe orbits we have considered m 2/ m 1=3.5×10-4, and the variation of μ 3 from 3.5×10-4 to 9.7×10-5 or vice versa, depending on the orbit selected as "seed". We discuss some issues related to the periodicity and symmetry of the orbits. We study the stability of some of them taking the limit μ 3→0. The numerical continuation was done using the software AUTO.
On the periodic orbits and the integrability of the regularized Hill lunar problem
NASA Astrophysics Data System (ADS)
Llibre, Jaume; Roberto, Luci Any
2011-08-01
The classical Hill's problem is a simplified version of the restricted three-body problem where the distance of the two massive bodies (say, primary for the largest one and secondary for the smallest one) is made infinity through the use of Hill's variables. The Levi-Civita regularization takes the Hamiltonian of the Hill lunar problem into the form of two uncoupled harmonic oscillators perturbed by the Coriolis force and the Sun action, polynomials of degree 4 and 6, respectively. In this paper, we study periodic orbits of the planar Hill problem using the averaging theory. Moreover, we provide information about the C1 integrability or non-integrability of the regularized Hill lunar problem.
An investigation into some problems in analytical processing of lunar orbiter photography
NASA Technical Reports Server (NTRS)
Ghosh, S. K.; Ekenobi, S.
1972-01-01
Problems in analytical processing of lunar orbiter photography are discussed. The effects of image motion and image motion compensation on the location of the principal point are analyzed. The effect of the focal plane shutter on the distortion and interior geometry is examined. Real data is used to confirm the workability of a mathematical model and the use of a computer to calibrate spaceborne photographic imagery.
Families of Asymmetric Periodic Orbits in the Restricted Three-body Problem
NASA Astrophysics Data System (ADS)
Papadakis, K. E.
2008-10-01
This paper studies the asymmetric solutions of the restricted planar problem of three bodies, two of which are finite, moving in circular orbits around their center of masses, while the third is infinitesimal. We explore, numerically, the families of asymmetric simple-periodic orbits which bifurcate from the basic families of symmetric periodic solutions f, g, h, i, l and m, as well as the asymmetric ones associated with the families c, a and b which emanate from the collinear equilibrium points L 1, L 2 and L 3 correspondingly. The evolution of these asymmetric families covering the entire range of the mass parameter of the problem is presented. We found that some symmetric families have only one bifurcating asymmetric family, others have infinity number of asymmetric families associated with them and others have not branching asymmetric families at all, as the mass parameter varies. The network of the symmetric families and the branching asymmetric families from them when the primaries are equal, when the left primary body is three times bigger than the right one and for the Earth Moon case, is presented. Minimum and maximum values of the mass parameter of the series of critical symmetric periodic orbits are given. In order to avoid the singularity due to binary collisions between the third body and one of the primaries, we regularize the equations of motion of the problem using the Levi-Civita transformations.
Minesaki, Yukitaka
2013-08-01
For the restricted three-body problem, we propose an accurate orbital integration scheme that retains all conserved quantities of the two-body problem with two primaries and approximately preserves the Jacobi integral. The scheme is obtained by taking the limit as mass approaches zero in the discrete-time general three-body problem. For a long time interval, the proposed scheme precisely reproduces various periodic orbits that cannot be accurately computed by other generic integrators.
NASA Technical Reports Server (NTRS)
Lara, Martin; Palacian, Jesus F.
2007-01-01
Frozen orbits of the Hill problem are determined in the double averaged problem, where short and long period terms are removed by means of Lie transforms. The computation of initial conditions of corresponding quasi periodic solutions in the non-averaged problem is straightforward for the perturbation method used provides the explicit equations of the transformation that connects the averaged and non-averaged models. A fourth order analytical theory reveals necessary for the accurate computation of quasi periodic, frozen orbits.
Parallel satellite orbital situational problems solver for space missions design and control
NASA Astrophysics Data System (ADS)
Atanassov, Atanas Marinov
2016-11-01
Solving different scientific problems for space applications demands implementation of observations, measurements or realization of active experiments during time intervals in which specific geometric and physical conditions are fulfilled. The solving of situational problems for determination of these time intervals when the satellite instruments work optimally is a very important part of all activities on every stage of preparation and realization of space missions. The elaboration of universal, flexible and robust approach for situation analysis, which is easily portable toward new satellite missions, is significant for reduction of missions' preparation times and costs. Every situation problem could be based on one or more situation conditions. Simultaneously solving different kinds of situation problems based on different number and types of situational conditions, each one of them satisfied on different segments of satellite orbit requires irregular calculations. Three formal approaches are presented. First one is related to situation problems description that allows achieving flexibility in situation problem assembling and presentation in computer memory. The second formal approach is connected with developing of situation problem solver organized as processor that executes specific code for every particular situational condition. The third formal approach is related to solver parallelization utilizing threads and dynamic scheduling based on "pool of threads" abstraction and ensures a good load balance. The developed situation problems solver is intended for incorporation in the frames of multi-physics multi-satellite space mission's design and simulation tools.
Wood's anomalies and surface waves in the problem of scattering by a periodic boundary. I
Kamotskii, I V; Nazarov, S A
1999-02-28
The solution of the problem of diffraction of an acoustic plane wave by a periodic boundary for frequencies close to threshold values is studied. Wood's well-known experiments show that deviations from the threshold frequency values by a small quantity bring about drastic changes in the diffraction pattern. The asymptotic formula with respect to the small parameter {epsilon} is obtained for the corresponding scattering matrix.
Short-periodic variations and second-order numerical averaging. [for orbit prediction problems
NASA Technical Reports Server (NTRS)
Lutzky, D.; Uphoff, C.
1975-01-01
The principal disadvantage of the method of numerical averaging is that it provides only the average time history of the orbital elements and yields no information about the high-frequency or short-periodic variations that occur inside the averaging interval. This paper contains a description of a technique for recovering the short-periodic variations by minor modifications to the averaging process so as to permit the construction of a Fourier series for the osculating elements. The availability of this series permits the extension of the averaging technique to higher order and allows us to account for short-periodic coupling of the perturbations. Comparisons of the results with numerically integrated solutions are presented for three distinct orbit prediction problems.
Trade space visualization applied to Lambert's Problem for elliptical insertion orbits
NASA Astrophysics Data System (ADS)
Spencer, David B.; Shank, Brian S.
2016-05-01
This paper investigates the solution of Lambert's Problem for targets in elliptical orbits. A mission design software framework to determine the optimal interplanetary trajectory and final capture orbit based on mission constraints and requirements between a departure and arrival body has been developed. Integration of a trade space visualization tool, such as the Applied Research Laboratory Trade Space Visualizer software permits a mission designer to visually inspect the multi-dimensional trade space and investigate regions of feasible trajectories. This analysis process can provide a mission designer with the capability to reduce the amount of time needed to design interplanetary trajectories by reducing the number of feasible solutions that would need to be investigated.
Short-periodic variations and second-order numerical averaging. [for orbit prediction problems
NASA Technical Reports Server (NTRS)
Lutzky, D.; Uphoff, C.
1975-01-01
The principal disadvantage of the method of numerical averaging is that it provides only the average time history of the orbital elements and yields no information about the high-frequency or short-periodic variations that occur inside the averaging interval. This paper contains a description of a technique for recovering the short-periodic variations by minor modifications to the averaging process so as to permit the construction of a Fourier series for the osculating elements. The availability of this series permits the extension of the averaging technique to higher order and allows us to account for short-periodic coupling of the perturbations. Comparisons of the results with numerically integrated solutions are presented for three distinct orbit prediction problems.
Coupled orbit-attitude mission design in the circular restricted three-body problem
NASA Astrophysics Data System (ADS)
Guzzetti, Davide
Trajectory design increasingly leverages multi-body dynamical structures that are based on an understanding of various types of orbits in the Circular Restricted Three-Body Problem (CR3BP). Given the more complex dynamical environment, mission applications may also benefit from deeper insight into the attitude motion. In this investigation, the attitude dynamics are coupled with the trajectories in the CR3BP. In a highly sensitive dynamical model, such as the orbit-attitude CR3BP, periodic solutions allow delineation of the fundamental dynamical structures. Periodic solutions are also a subset of motions that are bounded over an infinite time-span (assuming no perturbing factors), without the necessity to integrate over an infinite time interval. Euler equations of motion and quaternion kinematics describe the rotational behavior of the spacecraft, whereas the translation of the center of mass is modeled in the CR3BP equations. A multiple shooting and continuation procedure are employed to target orbit-attitude periodic solutions in this model. Application of Floquet theory, Poincare mapping, and grid search to identify initial guesses for the targeting algorithm is described. In the Earth-Moon system, representative scenarios are explored for axisymmetric vehicles with various inertia characteristics, assuming that the vehicles move along Lyapunov, halo as well as distant retrograde orbits. A rich structure of possible periodic behaviors appears to pervade the solution space in the coupled problem. The stability analysis of the attitude dynamics for the selected families is included. Among the computed solutions, marginally stable and slowly diverging rotational behaviors exist and may offer interesting mission applications. Additionally, the solar radiation pressure is included and a fully coupled orbit-attitude model is developed. With specific application to solar sails, various guidance algorithms are explored to direct the spacecraft along a desired path
On the Optimization of the Inverse Problem for Bouguer Gravity Anomalies
NASA Astrophysics Data System (ADS)
Zamora, A.; Velasco, A. A.; Gutierrez, A. E.
2013-12-01
Inverse modeling of gravity data presents a very ill-posed mathematical problem, given that solutions are non-unique and small changes in parameters (position and density contrast of an anomalous body) can highly impact the resulting Earth's model. Although implementing 2- and 3-Dimensional gravitational inverse problems can determine the structural composition of the Earth, traditional inverse modeling approaches can be very unstable. A model of the shallow substructure is based on the density contrasts of anomalous bodies -with different densities with respect to a uniform region- or the boundaries between layers in a layered environment. We implement an interior-point method constrained optimization technique to improve the 2-D model of the Earth's structure through the use of known density constraints for transitional areas obtained from previous geological observations (e.g. core samples, seismic surveys, etc.). The proposed technique is applied to both synthetic data and gravitational data previously obtained from the Rio Grande Rift and the Cooper Flat Mine region located in Sierra County, New Mexico. We find improvements on the models obtained from this optimization scheme given that getting rid of geologically unacceptable models that would otherwise meet the required geophysical properties reduces the solution space.
NASA Technical Reports Server (NTRS)
Dean, Timothy C.; Ventrice, Carl A.
1995-01-01
As a final report for phase 1 of the project, the researchers are submitting to the Tennessee Tech Office of Research the following two papers (reprinted in this report): 'Collision Line Broadening Effects on Spectrometric Data from the Optical Plume Anomaly System (OPAD),' presented at the 30th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, 27-29 June 1994, and 'Calculation of Collision Cross Sections for Atomic Line Broadening in the Plume of the Space Shuttle Main Engine (SSME),' presented at the IEEE Southeastcon '95, 26-29 March 1995. These papers fully state the problem and the progress made up to the end of NASA Fiscal Year 1994. The NASA OPAD system was devised to predict concentrations of anomalous species in the plume of the Space Shuttle Main Engine (SSME) through analysis of spectrometric data. The self absorption of the radiation of these plume anomalies is highly dependent on the line shape of the atomic transition of interest. The Collision Line Broadening paper discusses the methods used to predict line shapes of atomic transitions in the environment of a rocket plume. The Voigt profile is used as the line shape factor since both Doppler and collisional line broadening are significant. Methods used to determine the collisional cross sections are discussed and the results are given and compared with experimental data. These collisional cross sections are then incorporated into the current self absorbing radiative model and the predicted spectrum is compared to actual spectral data collected from the Stennis Space Center Diagnostic Test Facility rocket engine. The second paper included in this report investigates an analytical method for determining the cross sections for collision line broadening by molecular perturbers, using effective central force interaction potentials. These cross sections are determined for several atomic species with H2, one of the principal constituents of the SSME plume environment, and compared with experimental data.
NASA Astrophysics Data System (ADS)
Dean, Timothy C.; Ventrice, Carl A.
1995-05-01
As a final report for phase 1 of the project, the researchers are submitting to the Tennessee Tech Office of Research the following two papers (reprinted in this report): 'Collision Line Broadening Effects on Spectrometric Data from the Optical Plume Anomaly System (OPAD),' presented at the 30th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, 27-29 June 1994, and 'Calculation of Collision Cross Sections for Atomic Line Broadening in the Plume of the Space Shuttle Main Engine (SSME),' presented at the IEEE Southeastcon '95, 26-29 March 1995. These papers fully state the problem and the progress made up to the end of NASA Fiscal Year 1994. The NASA OPAD system was devised to predict concentrations of anomalous species in the plume of the Space Shuttle Main Engine (SSME) through analysis of spectrometric data. The self absorption of the radiation of these plume anomalies is highly dependent on the line shape of the atomic transition of interest. The Collision Line Broadening paper discusses the methods used to predict line shapes of atomic transitions in the environment of a rocket plume. The Voigt profile is used as the line shape factor since both Doppler and collisional line broadening are significant. Methods used to determine the collisional cross sections are discussed and the results are given and compared with experimental data. These collisional cross sections are then incorporated into the current self absorbing radiative model and the predicted spectrum is compared to actual spectral data collected from the Stennis Space Center Diagnostic Test Facility rocket engine. The second paper included in this report investigates an analytical method for determining the cross sections for collision line broadening by molecular perturbers, using effective central force interaction potentials. These cross sections are determined for several atomic species with H2, one of the principal constituents of the SSME plume environment, and compared with experimental data.
The Near-Earth Orbital Debris Problem and the Challenges for Environment Remediation
NASA Technical Reports Server (NTRS)
Liou, Jer-Chyi
2012-01-01
The near-Earth space environment has been gradually polluted with orbital debris (OD) since the beginning of space activities 55 years ago. Although this problem has been known to the research community for decades, the public was, in general, unaware of the issue until the anti-satellite test conducted by China in 2007 and the collision between Cosmos 2251 and the operational Iridium 33 in 2009. The latter also underlined the potential of an ongoing collision cascade effect (the "Kessler Syndrome") in the low Earth orbit (LEO, the region below 2000 km altitude). Recent modeling results have indicated that mitigation measures commonly adopted by the international space community will be insufficient to stabilize the LEO debris population. To better limit the OD population increase, more aggressive actions must be considered. There are three options for OD environment remediation-removal of large/massive intact objects to address the root cause of the OD population growth problem, removal of 5-mm-to-1 cm debris to mitigate the main mission-ending threats for the majority of operational spacecraft, and prevention of major debris-generating collisions as a temporary means to slow down the OD population increase. The technology, engineering, and cost challenges to carry out any of these three options are monumental. It will require innovative ideas, game-changing technologies, and major collaborations at the international level to address the OD problem and preserve the near-Earth environment for future generations.
Action minimizing orbits in the n-body problem with simple choreography constraint
NASA Astrophysics Data System (ADS)
Barutello, V.; Terracini, S.
2004-11-01
In 1999 Chenciner and Montgomery found a remarkably simple choreographic motion for the planar three-body problem (see [11]). In this solution, three equal masses travel on an figure-of-eight shaped planar curve; this orbit is obtained by minimizing the action integral on the set of simple planar choreographies with some special symmetry constraints. In this work our aim is to study the problem of n masses moving in {\\Bbb R}^d under an attractive force generated by a potential of the kind 1/ragr, agr > 0, with the only constraint to be a simple choreography: if q1(t),...,qn(t) are the n orbits then we impose the existence of x \\in H^1_{2 \\pi}({\\Bbb R},{\\Bbb R}^d) such that \\[ \\begin{equation*}q_i(t)=x(t+(i-1) \\tau ),\\tqs i=1,\\ldots,n,\\quad t \\in {\\Bbb R},\\end{equation*} \\] where tgr = 2pgr/n. In this setting, we first prove that for every d,n \\in {\\Bbb N} and agr > 0, the Lagrangian action attains its absolute minimum on the planar regular n-gon relative equilibrium. Next, we deal with the problem in a rotating frame and show a richer phenomenology: indeed, while for some values of the angular velocity, the minimizers are still relative equilibria, for others, the minima of the action are no longer rigid motions.
Bosonic quasideterminants and eigenvalue problems of generalized spin-orbit operators
Ben Geloun, Joseph; Hounkonnou, M. Norbert
2008-02-15
This paper deals with an extension of the applications of the paper by Gelfand and Retakh [Funct. Anal. Appl. 25, 91 (1991)] on quasideterminant (QsD) algebraic method to eigenvalue problems in quantum mechanics. Using relevant identities on the free 1-mode bosonic algebra, we build characteristic QsDs associated with generalized spin-orbit Hamiltonians with a well defined representation which allows us to explicitly and straightforwardly compute analytical expressions of eigenenergies. Specific instances are provided on f-deformed generalized Jaynes-Cummings models and other Hamiltonian classes widely used in condensed matter physics.
NASA Astrophysics Data System (ADS)
Giancotti, Marco; Campagnola, Stefano; Tsuda, Yuichi; Kawaguchi, Jun'ichiro
2014-11-01
This work studies periodic solutions applicable, as an extended phase, to the JAXA asteroid rendezvous mission Hayabusa 2 when it is close to target asteroid 1999 JU3. The motion of a spacecraft close to a small asteroid can be approximated with the equations of Hill's problem modified to account for the strong solar radiation pressure. The identification of families of periodic solutions in such systems is just starting and the field is largely unexplored. We find several periodic orbits using a grid search, then apply numerical continuation and bifurcation theory to a subset of these to explore the changes in the orbit families when the orbital energy is varied. This analysis gives information on their stability and bifurcations. We then compare the various families on the basis of the restrictions and requirements of the specific mission considered, such as the pointing of the solar panels and instruments. We also use information about their resilience against parameter errors and their ground tracks to identify one particularly promising type of solution.
Quantum Monte Carlo impurity solvers for multi-orbital problems and frequency-dependent interactions
NASA Astrophysics Data System (ADS)
Shinaoka, H.; Assaad, F.; Blümer, N.; Werner, P.
2017-07-01
The solution of an auxiliary quantum impurity system is the computationally expensive step in dynamical mean field theory simulations of lattice models and materials. In this review, we discuss Monte Carlo based impurity solvers, which are suitable for a wide range of applications. In particular, we present an efficient implementation of the hybridization expansion approach, which enables the simulation of multiorbital impurity problems with off-diagonal and complex hybridizations, and dynamically screened (retarded) density-density interactions. As a complementary approach, we discuss an impurity solver based on the determinant Monte Carlo method, which scales favorably with inverse temperature and hence provides access to the very low temperature regime. The usefulness of these state-of-the-art impurity solvers is demonstrated with applications to the downfolding problem, i.e., the systematic derivation of dynamically screened interactions for low-energy effective models, and to pyrochlore iridates, where the spin-orbit coupling leads to complex hybridization functions in a multi-orbital system. As a benchmark for cluster extensions of dynamical mean field theory, we also present results from lattice Monte Carlo simulations for the momentum dependence of the pseudo-gap in the half-filled two-dimensional Hubbard model.
NASA Technical Reports Server (NTRS)
Borderies, N.; Goldreich, P.
1984-01-01
Henrad's (1982) method, which is based on an extension of the theory of adiabatic invariants, is presently applied to a simplified analytic derivation of the capture probabilities for the j + 1 : j and j + 2 : j orbital resonances. The results originally obtained by Yoder (1979) are thereby recovered.
Construction of confidence regions in the problem of asteroid orbit determination
NASA Astrophysics Data System (ADS)
Chernitsov, A. M.; Tamarov, V. A.; Barannikov, Ye. A.
2017-09-01
The factors required for estimation of the accuracy of the confidence region construction in the problem of asteroid orbit determination are considered. Blunders and large systematic errors occurring in asteroid observations increase the sizes of confidence regions and cause their noticeable shift in the space of determined parameters. We present the factors that, in addition to analysis of discrepancies (O-C), provide an opportunity to estimate the efficiency of screening observations containing gross systematic errors. The developed factors have been tested for efficiency using simulated observations. The observations have been simulated by parameters set by us and assumed true. It is shown how the sizes of systematic errors and the number of observations with these errors influence the results of screening. All calculations have been performed within the Keplerian model of asteroid motion.
Accurate Orbital Integration of the General Three-body Problem Based on the d'Alembert-type Scheme
NASA Astrophysics Data System (ADS)
Minesaki, Yukitaka
2013-03-01
We propose an accurate orbital integration scheme for the general three-body problem that retains all conserved quantities except angular momentum. The scheme is provided by an extension of the d'Alembert-type scheme for constrained autonomous Hamiltonian systems. Although the proposed scheme is merely second-order accurate, it can precisely reproduce some periodic, quasiperiodic, and escape orbits. The Levi-Civita transformation plays a role in designing the scheme.
ACCURATE ORBITAL INTEGRATION OF THE GENERAL THREE-BODY PROBLEM BASED ON THE D'ALEMBERT-TYPE SCHEME
Minesaki, Yukitaka
2013-03-15
We propose an accurate orbital integration scheme for the general three-body problem that retains all conserved quantities except angular momentum. The scheme is provided by an extension of the d'Alembert-type scheme for constrained autonomous Hamiltonian systems. Although the proposed scheme is merely second-order accurate, it can precisely reproduce some periodic, quasiperiodic, and escape orbits. The Levi-Civita transformation plays a role in designing the scheme.
Siah, We Fong; Patel, Bhupendra Ck; Malhotra, Raman
2016-08-01
To report a case series of patients with persistent temple-related problems following lateral wall rim-sparing (LWRS) orbital decompression for thyroid-related orbitopathy and to discuss their management. Retrospective review of medical records of patients referred to two oculoplastic centres (Corneoplastic Unit, Queen Victoria Hospital, East Grinstead, UK and Moran Eye Center, University of Utah, Salt Lake City, USA) for intervention to improve/alleviate temple-related problems. All patients were seeking treatment for their persistent, temple-related problems of minimum 3 years' duration post decompression. The main outcome measure was the resolution or improvement of temple-related problems. Eleven orbits of six patients (five females) with a median age of 57 years (range 23-65) were included in this study. Temple-related problems consisted of cosmetically bothersome temple hollowness (n=11; 100%), masticatory oscillopsia (n=8; 73%), temple tenderness (n=4; 36%), 'clicking' sensation (n=4; 36%) and gaze-evoked ocular pain (n=4; 36%). Nine orbits were also complicated by proptosis and exposure keratopathy. Preoperative imaging studies showed the absence of lateral wall in all 11 orbits and evidence of prolapsed lacrimal gland into the wall defect in four orbits. Intervention included the repair of the lateral wall defect with a sheet implant, orbital decompression involving fat, the medial wall or orbital floor and autologous fat transfer or synthetic filler for temple hollowness. Postoperatively, there was full resolution of masticatory oscillation, temple tenderness, 'clicking' sensation and gaze-evoked ocular pain, and an improvement in temple hollowness. Pre-existing diplopia in one patient resolved after surgery while two patients developed new-onset diplopia necessitating strabismus surgery. This is the first paper to show that persistent, troublesome temple-related problems following LWRS orbital decompression can be surgically corrected. Patients
NASA Astrophysics Data System (ADS)
Umehara, Hiroaki; Tanikawa, Kiyotaka
The existence of escape and nonescape orbits arbitrarily close to the homothetic equilateral triple-collision orbit is considered analytically in the three-body problem with zero initial velocities and equal masses. It is proved that escape orbits in the initial condition space are distributed around three kinds of isosceles orbits. It is also proved that nonescape orbits are distributed in between the escape orbits where different particles escape. In order to show this, it is proved that the homothetic-equilateral orbit is isolated from other triple-collision orbits as far as the collision at the first triple encounter is concerned. Moreover, the escape criterion is formulated in the planar-isosceles problem and translated into the words of regularizing variables. The result obtained by us explains the orbital structure numerically.
NASA Astrophysics Data System (ADS)
Vashkov'yak, M. A.
1998-03-01
We study the families of periodically evolving orbits in Hill's averaged problem with allowance for a polar oblateness of the central planet. In the integrable case, where its equatorial plane coincides with the orbital plane of a distant attracting point, we construct the families of generating orbits. In addition to stationary solutions in the plane (g is the argument of the pericenter latitude, e is the eccentricity), we have also found periodic generating solutions. For small deviations from the stationary solutions, these periodic solutions are described by analytical formulas, whereas the large-amplitude solutions are obtained numerically. Continuing the generating solutions to the domain of arbitrary angles eps between the above planes, we trace the changes in the parameters of the periodically evolving orbits and find various branches of these solutions in the (eps, e) plane for various constants of the first integral of the problem - the averaged perturbing function. These branches originate from both periodic and nonresonant quasi-stationary generating solutions of the coplanar problem (eps = 0). For eps = 23.44 deg, which corresponds to the Earth-Moon-Sun model system, we note cases where one, three, and two (in a degenerate case) solutions, which correspond to periodically evolving orbits of the Earth's satellites with the semimajor axis a = 42 200 km, exist.
Rehabilitation of orbital defect with silicone orbital prosthesis retained by dental implants.
Guttal, Satyabodh Shesharaj; Desai, Jhanvi; Kudva, Adarsh; Patil, Basavaraj R
2016-01-01
Orbital defects can result from cancer, birth anomalies, or trauma leading to an onslaught of problems in the function and psyche of the patient. These defects are restored by surgical reconstruction and followed by placement of orbital prosthesis for cosmetic makeup. The use of dental implants in retaining orbital prosthesis improves patient acceptance of the prosthesis owing to better retention and stability than conventional adhesive retained prosthesis. This case report describes a custom-made magnetic retentive assembly anchored by a dental implant which offers the orbital prosthesis the simplicity of self-alignment and ease of use.
Orbital Divergence and Relaxation in the Gravitational N-Body Problem
NASA Astrophysics Data System (ADS)
Hut, P.; Heggie, D. C.
2002-12-01
One of the fundamental aspects of statistical behaviour in many-body systems is exponential divergence of neighbouring orbits, which is often discussed in terms of Liapounov exponents. Here we study this topic for the classical gravitational N-body problem. The application we have in mind is to old stellar systems such as globular star clusters, where N˜106, and so we concentrate on spherical, centrally concentrated systems with total energy E<0. Hitherto no connection has been made between the time scale for divergence (denoted here by t e ) and the time scale on which the energies of the particles evolve because of two-body encounters (i.e., the two-body relaxation time scale, t r ), even though both may be calculated by similar considerations. In this paper we give a simplified model showing that divergence in phase space is initially roughly exponential, on a timescale proportional to the crossing time (defined as a mean time for a star to cross from one side of the system to another). In this phase t e << t r , if N is not too small (i.e., N≫30). After several e-folding times, the model shows that the divergence slows down. Thereafter the divergence (measured by the energies of the bodies) varies with time as t 1/2, on a timescale nearly proportional to the familiar two-body relaxation timescale, i.e., t e ˜ t r in this phase. These conclusions are illustrated by numerical results.
The theory of secondary resonances in the spin-orbit problem
NASA Astrophysics Data System (ADS)
Gkolias, Ioannis; Celletti, Alessandra; Efthymiopoulos, Christos; Pucacco, Giuseppe
2016-06-01
We study the resonant dynamics in a simple one degree of freedom, time dependent Hamiltonian model describing spin-orbit interactions. The equations of motion admit periodic solutions associated with resonant motions, the most important being the synchronous one in which most evolved satellites of the Solar system, including the Moon, are observed. Such primary resonances can be surrounded by a chain of smaller islands which one refers to as secondary resonances. Here, we propose a novel canonical normalization procedure allowing to obtain a higher order normal form, by which we obtain analytical results on the stability of the primary resonances as well as on the bifurcation thresholds of the secondary resonances. The procedure makes use of the expansion in a parameter, called the detuning, measuring the shift from the exact secondary resonance. Also, we implement the so-called `book-keeping' method, i.e. the introduction of a suitable separation of the terms in orders of smallness in the normal form construction, which deals simultaneously with all the small parameters of the problem. Our analytical computation of the bifurcation curves is in excellent agreement with the results obtained by a numerical integration of the equations of motion, thus providing relevant information on the parameter regions where satellites can be found in a stable configuration.
NASA Astrophysics Data System (ADS)
Pousse, Alexandre; Robutel, Philippe; Vienne, Alain
2017-02-01
In the framework of the planar and circular restricted three-body problem, we consider an asteroid that orbits the Sun in quasi-satellite motion with a planet. A quasi-satellite trajectory is a heliocentric orbit in co-orbital resonance with the planet, characterized by a nonzero eccentricity and a resonant angle that librates around zero. Likewise, in the rotating frame with the planet, it describes the same trajectory as the one of a retrograde satellite even though the planet acts as a perturbator. In the last few years, the discoveries of asteroids in this type of motion made the term "quasi-satellite" more and more present in the literature. However, some authors rather use the term "retrograde satellite" when referring to this kind of motion in the studies of the restricted problem in the rotating frame. In this paper, we intend to clarify the terminology to use, in order to bridge the gap between the perturbative co-orbital point of view and the more general approach in the rotating frame. Through a numerical exploration of the co-orbital phase space, we describe the quasi-satellite domain and highlight that it is not reachable by low eccentricities by averaging process. We will show that the quasi-satellite domain is effectively included in the domain of the retrograde satellites and neatly defined in terms of frequencies. Eventually, we highlight a remarkable high eccentric quasi-satellite orbit corresponding to a frozen ellipse in the heliocentric frame. We extend this result to the eccentric case (planet on an eccentric motion) and show that two families of frozen ellipses originate from this remarkable orbit.
NASA Astrophysics Data System (ADS)
Pousse, Alexandre; Robutel, Philippe; Vienne, Alain
2017-08-01
In the framework of the planar and circular restricted three-body problem, we consider an asteroid that orbits the Sun in quasi-satellite motion with a planet. A quasi-satellite trajectory is a heliocentric orbit in co-orbital resonance with the planet, characterized by a nonzero eccentricity and a resonant angle that librates around zero. Likewise, in the rotating frame with the planet, it describes the same trajectory as the one of a retrograde satellite even though the planet acts as a perturbator. In the last few years, the discoveries of asteroids in this type of motion made the term "quasi-satellite" more and more present in the literature. However, some authors rather use the term "retrograde satellite" when referring to this kind of motion in the studies of the restricted problem in the rotating frame. In this paper, we intend to clarify the terminology to use, in order to bridge the gap between the perturbative co-orbital point of view and the more general approach in the rotating frame. Through a numerical exploration of the co-orbital phase space, we describe the quasi-satellite domain and highlight that it is not reachable by low eccentricities by averaging process. We will show that the quasi-satellite domain is effectively included in the domain of the retrograde satellites and neatly defined in terms of frequencies. Eventually, we highlight a remarkable high eccentric quasi-satellite orbit corresponding to a frozen ellipse in the heliocentric frame. We extend this result to the eccentric case (planet on an eccentric motion) and show that two families of frozen ellipses originate from this remarkable orbit.
NASA Astrophysics Data System (ADS)
Pinotsis, Antonis D.
2009-10-01
By using Birkhoff's regularizing transformation, we study the evolution of some of the infinite j-k type families of collision periodic orbits with respect to the mass ratio μ as well as their stability and dynamical structure, in the planar restricted three-body problem. The μ- C characteristic curves of these families extend to the left of the μ- C diagram, to smaller values of μ and most of them go downwards, although some of them end by spiralling around the constant point S* ( μ=0.47549, C=3) of the Bozis diagram (1970). Thus we know now the continuation of the families which go through collision periodic orbits of the Sun-Jupiter and Earth-Moon systems. We found new μ- C and x- C characteristic curves. Along each μ- C characteristic curve changes of stability to instability and vice versa and successive very small stable and very large unstable segments appear. Thus we found different types of bifurcations of families of collision periodic orbits. We found cases of infinite period doubling Feigenbaum bifurcations as well as bifurcations of new families of symmetric and non-symmetric collision periodic orbits of the same period. In general, all the families of collision periodic orbits are strongly unstable. Also, we found new x- C characteristic curves of j-type classes of symmetric periodic orbits generated from collision periodic orbits, for some given values of μ. As C varies along the μ- C or the x- C spiral characteristics, which approach their focal-terminating-point, infinite loops, one inside the other, surrounding the triangular points L4 and L5 are formed in their orbits. So, each terminating point corresponds to a collision asymptotic symmetric periodic orbit for the case of the μ- C curve or a non-collision asymptotic symmetric periodic orbit for the case of the x- C curve, that spiral into the points L4 and L5, with infinite period. All these are changes in the topology of the phase space and so in the dynamical properties of the
Astrometric solar system anomalies
Nieto, Michael Martin; Anderson, John D
2009-01-01
There are at least four unexplained anomalies connected with astrometric data. perhaps the most disturbing is the fact that when a spacecraft on a flyby trajectory approaches the Earth within 2000 km or less, it often experiences a change in total orbital energy per unit mass. next, a secular change in the astronomical unit AU is definitely a concern. It is increasing by about 15 cm yr{sup -1}. The other two anomalies are perhaps less disturbing because of known sources of nongravitational acceleration. The first is an apparent slowing of the two Pioneer spacecraft as they exit the solar system in opposite directions. Some astronomers and physicists are convinced this effect is of concern, but many others are convinced it is produced by a nearly identical thermal emission from both spacecraft, in a direction away from the Sun, thereby producing acceleration toward the Sun. The fourth anomaly is a measured increase in the eccentricity of the Moon's orbit. Here again, an increase is expected from tidal friction in both the Earth and Moon. However, there is a reported unexplained increase that is significant at the three-sigma level. It is produent to suspect that all four anomalies have mundane explanations, or that one or more anomalies are a result of systematic error. Yet they might eventually be explained by new physics. For example, a slightly modified theory of gravitation is not ruled out, perhaps analogous to Einstein's 1916 explanation for the excess precession of Mercury's perihelion.
Nymmik, R A
1999-10-01
A wide range of the galactic cosmic ray and SEP event flux simulation problems for the near-Earth satellite and manned spacecraft orbits and for the interplanetary mission trajectories are discussed. The models of the galactic cosmic ray and SEP events in the Earth orbit beyond the Earth's magnetosphere are used as a basis. The particle fluxes in the near-Earth orbits should be calculated using the transmission functions. To calculate the functions, the dependences of the cutoff rigidities on the magnetic disturbance level and on magnetic local time have to be known. In the case of space flights towards the Sun and to the boundary of the solar system, particular attention is paid to the changes in the SEP event occurrence frequency and size. The particle flux gradients are applied in this case to galactic cosmic ray fluxes.
Steady state obliquity of a rigid body in the spin-orbit resonant problem: application to Mercury
NASA Astrophysics Data System (ADS)
Lhotka, Christoph
2017-09-01
We investigate the stable Cassini state 1 in the p : q spin-orbit resonant problem. Our study includes the effect of the gravitational potential up to degree and order 4 and p : q spin-orbit resonances with p,q≤ 8 and p≥ q . We derive new formulae that link the gravitational field coefficients with its secular orbital elements and its rotational parameters. The formulae can be used to predict the orientation of the spin axis and necessary angular momentum at exact resonance. We also develop a simple pendulum model to approximate the dynamics close to resonance and make use of it to predict the libration periods and widths of the oscillatory regime of motions in phase space. Our analytical results are based on averaging theory that we also confirm by means of numerical simulations of the exact dynamical equations. Our results are applied to a possible rotational history of Mercury.
Nadiri, Ata Allah; Sadeghi Aghdam, Fariba; Khatibi, Rahman; Asghari Moghaddam, Asghar
2017-09-19
An investigation is undertaken to identify arsenic anomalies at the complex of Sahand dam, East Azerbaijan, northwest Iran. The complex acts as a system, in which the impounding reservoir catalyses system components related to Origin-Source-Pathways-Receptor-Consequence (OSPRC) viewed as a risk system. This 'conceptual framework' overlays a 'perceptual model' of the physical system, in which arsenic with geogenic origins diffused into the formations through extensive fractures swept through the region during the Miocene era. Impacts of arsenic anomalies were local until the provision of the impounding reservoir in the last 10years, which transformed it into active system-wide risk exposures. The paper uses existing technique of: statistical, graphical, multivariate analysis, geological survey and isotopic study, but these often seem ad hoc and without common knowledgebase. Risk analysis approaches are sought to treat existing fragmentation in practices of identifying and mitigating arsenic anomalies. The paper contributes towards next generation best practice through: (i) transferring and extending knowledge on the OSPRC framework; (ii) introducing 'OSPRC cells' to capture unique idiosyncrasies at each cell; and (iii) suggesting a 'soft modelling' procedure based on assembling knowledgebase of existing techniques with partially converging and partially diverging information levels, where knowledgebase invokes model equations with increasing resolutions. The data samples from the study area for the period of 2002-12 supports the study and indicates the following 'risk cells' for the study area: (i) local arsenic risk exposures at south of the reservoir, (ii) system-wide arsenic risks at its north; and (iii) system-wide arsenic risk exposures within the reservoir even after dilution. Copyright © 2017 Elsevier B.V. All rights reserved.
Bagger, J.; Nemeschansky, D.; Yankielowicz, S.
1985-05-01
A new type of anomaly is discussed that afflicts certain non-linear sigma models with fermions. This anomaly is similar to the ordinary gauge and gravitational anomalies since it reflects a topological obstruction to the reparametrization invariance of the quantum effective action. Nonlinear sigma models are constructed based on homogeneous spaces G/H. Anomalies arising when the fermions are chiral are shown to be cancelled sometimes by Chern-Simons terms. Nonlinear sigma models are considered based on general Riemannian manifolds. 9 refs. (LEW)
Evangelista, Francesco A; Gauss, Jürgen
2010-07-28
In this communication we report the results of our studies on the orbital invariance properties of the state-specific multireference coupled cluster approach suggested by Mukherjee and co-workers (Mk-MRCC). In particular, we have gathered numerical evidence to show that even when the linear excitation manifold is modified in order to span the same space for each reference, the resulting method is not orbital invariant. In order to test this conjecture we have proposed a new truncation scheme (Mk-MRCCSDtq) which, in addition to full single and double excitations, contains partial triple and quadruple excitations. For a reference space generated by all possible combinations of two electrons in two orbitals, the linear excitation manifold of Mk-MRCCSDtq spans the same set for each reference determinant. Mk-MRCCSDtq is found to lack energy invariance for rotations among active molecular orbitals but it is less sensitive to orbital rotations than the conventional scheme which includes only singles and doubles (Mk-MRCCSD). Nevertheless, Mk-MRCCSDtq is a very accurate method, superior with respect to multireference configuration interaction approaches, and competitive with the active-space coupled cluster method and the MRexpT ansatz.
NASA Astrophysics Data System (ADS)
Elshaboury, S. M.; Abouelmagd, Elbaz I.; Kalantonis, V. S.; Perdios, E. A.
2016-09-01
The restricted three-body problem when the primaries are triaxial rigid bodies is considered and its basic dynamical features are studied. In particular, the equilibrium points are identified as well as their stability is determined in the special case when the Euler angles of rotational motion are accordingly θi = ψi = π/2 and φi = π/2, i = 1, 2. It is found that three unstable collinear equilibrium points exist and two triangular such points which may be stable. Special attention has also been paid to the study of simple symmetric periodic orbits and 31 families consisting of such orbits have been determined. It has been found that only one of these families consists entirely of unstable members while the remaining families contain stable parts indicating that other families bifurcate from them. Finally, using the grid-search technique a global solution in the space of initial conditions is obtained which comprises simple and of higher multiplicities symmetric periodic orbits as well as escape and collision orbits.
NASA Astrophysics Data System (ADS)
Peng, Hao; Xu, Shijie
2015-11-01
The multi-revolution elliptic halo (ME-Halo) orbit is a kind of strictly periodic orbit existing in the elliptic restricted three-body problem (ERTBP) model. Its remarkable features include that it survives the eccentricity perturbation of the primaries, it has a long period commeasurable with the primary period and that its stability property varies greatly as the eccentricity. The authors utilized continuation methods together with the multi-segment optimization method to generate two groups of ME-Halo orbits, and then systematically investigated their stability evolution with respect to the eccentricity and the mass ratio of the primaries. These parameters show complicate impacts on the stability. Some ME-Halo orbits can possess more than one pairs of real eigenvalue, some have negative real eigenvalues or complex eigenvalues out of the unit circle. For certain parameters, continuation failures are observed to be accompanied by a series of eigenvalue collision and bifurcations. The results in this paper can help to understand the nonautonomous dynamic of the ERTBP and can further aid in understanding the dynamical environment for real-world applications and, thus, contribute to the trajectory development process.
NASA Technical Reports Server (NTRS)
Ryan, R.; Gross, L. A.
1995-01-01
The Space Shuttle main engine (SSME) alternate high-pressure liquid oxygen pump experienced synchronous vibration and ball bearing life problems that were program threatening. The success of the program hinged on the ability to solve these development problems. The design and solutions to these problems are engirded in the lessons learned and experiences from prior programs, technology programs, and the ability to properly conduct failure or anomaly investigations. The failure investigation determines the problem cause and is the basis for recommending design solutions. For a complex problem, a comprehensive solution requires that formal investigation procedures be used, including fault trees, resolution logic, and action items worked through a concurrent engineering-multidiscipline team. The normal tendency to use an intuitive, cut-and-try approach will usually prove to be costly, both in money and time and will reach a less than optimum, poorly understood answer. The SSME alternate high-pressure oxidizer turbopump development has had two complex problems critical to program success: (1) high synchronous vibrations and (2) excessive ball bearing wear. This paper will use these two problems as examples of this formal failure investigation approach. The results of the team's investigation provides insight into the complexity of the turbomachinery technical discipline interacting/sensitivities and the fine balance of competing investigations required to solve problems and guarantee program success. It is very important to the solution process that maximum use be made of the resources that both the contractor and Government can bring to the problem in a supporting and noncompeting way. There is no place for the not-invented-here attitude. The resources include, but are not limited to: (1) specially skilled professionals; (2) supporting technologies; (3) computational codes and capabilities; and (4) test and manufacturing facilities.
Violent societies: an application of orbital decomposition to the problem of human violence.
Spohn, M
2008-01-01
This study uses orbital decomposition to analyze the patterns of how governments lose their monopolies on violence, therefore allowing those societies to descend into violent states from which it is difficult to recover. The nonlinear progression by which the governing body loses its monopoly is based on the work of criminologist Lonnie Athens and applied from the individual to the societal scale. Four different kinds of societies are considered: Those where the governing body is both unwilling and unable to assert its monopoly on violence (former Yugoslavia); where it is unwilling (Peru); where it is unable (South Africa); and a smaller pocket of violent society within a larger, more stable one (Gujarat). In each instance, orbital decomposition turns up insights not apparent in the qualitative data or through linear statistical analysis, both about the nature of the descent into violence and about the progression itself.
Space Weather, Cosmic Rays, and Satellite Anomalies
NASA Astrophysics Data System (ADS)
Lev, Dorman
Results are presented of the Satellite Anomaly Project, which aims to improve the methods of safeguarding satellites in the Earth’s magnetosphere from the negative effects of the space environment. Anomaly data from the USSR and Russian “Kosmos” series satellites in the period 1971-1999 are combined into one database, together with similar information on other spacecraft. This database contains, beyond the anomaly information, various characteristics of space weather: geomagnetic activity indices (Ap, AE and Dst), fluxes and fluencies of electrons and protons at different energies, high energy cosmic ray variations and other solar, interplanetary and solar wind data. A comparative analysis of the distribution of each of these parameters relative to satellite anomalies was carried out for the total number of anomalies (about 6000 events), and separately for high altitude orbit satellites ( 5000 events) and low altitude (about 800 events). No relation was found between low and high altitude satellite anomalies. Daily numbers of satellite anomalies, averaged by a superposed epoch method around sudden storm commencements and proton event onsets for high (>1500 km) and low (<1500 km) altitude orbits revealed a big difference in behavior. Satellites were divided into several groups according to their orbital characteristics (altitude and inclination). The relation of satellite anomalies to the environmental parameters was found to be different for various orbits, and this should be taken into account when developing anomaly frequency models. The preliminary anomaly frequency models are presented.
Stabilization and real world satellite problem. [transformations for stabilizing orbital equations
NASA Technical Reports Server (NTRS)
Velez, C. E.
1975-01-01
The use of transformations of orbital equations has been considered in connection with requirements for more accurate data. The reported investigation is concerned with an evaluation of the relative merits of such transformations. The formulations tested include the classical Cowell formulation, the time regularized formulation, stabilization by the use of integrals, and stabilization by the use of elements. It is found that irrespective of efficiency considerations, stabilizing transformation makes it possible to obtain precisions which are unattainable with the Cowell formulations.
Satellite GN and C Anomaly Trends
NASA Technical Reports Server (NTRS)
Robertson, Brent; Stoneking, Eric
2003-01-01
On-orbit anomaly records for satellites launched from 1990 through 2001 are reviewed to determine recent trends of un-manned space mission critical failures. Anomalies categorized by subsystems show that Guidance, Navigation and Control (GN&C) subsystems have a high number of anomalies that result in a mission critical failure when compared to other subsystems. A mission critical failure is defined as a premature loss of a satellite or loss of its ability to perform its primary mission during its design life. The majority of anomalies are shown to occur early in the mission, usually within one year from launch. GN&C anomalies are categorized by cause and equipment type involved. A statistical analysis of the data is presented for all anomalies compared with the GN&C anomalies for various mission types, orbits and time periods. Conclusions and recommendations are presented for improving mission success and reliability.
Shuttle Orbiter Active Thermal Control Subsystem design and flight experience
NASA Technical Reports Server (NTRS)
Bond, Timothy A.; Metcalf, Jordan L.; Asuncion, Carmelo
1991-01-01
The paper examines the design of the Space Shuttle Orbiter Active Thermal Control Subsystem (ATCS) constructed for providing the vehicle and payload cooling during all phases of a mission and during ground turnaround operations. The operation of the Shuttle ATCS and some of the problems encountered during the first 39 flights of the Shuttle program are described, with special attention given to the major problems encountered with the degradation of the Freon flow rate on the Orbiter Columbia, the Flash Evaporator Subsystem mission anomalies which occurred on STS-26 and STS-34, and problems encountered with the Ammonia Boiler Subsystem. The causes and the resolutions of these problems are discussed.
Shuttle Orbiter Active Thermal Control Subsystem design and flight experience
NASA Technical Reports Server (NTRS)
Bond, Timothy A.; Metcalf, Jordan L.; Asuncion, Carmelo
1991-01-01
The paper examines the design of the Space Shuttle Orbiter Active Thermal Control Subsystem (ATCS) constructed for providing the vehicle and payload cooling during all phases of a mission and during ground turnaround operations. The operation of the Shuttle ATCS and some of the problems encountered during the first 39 flights of the Shuttle program are described, with special attention given to the major problems encountered with the degradation of the Freon flow rate on the Orbiter Columbia, the Flash Evaporator Subsystem mission anomalies which occurred on STS-26 and STS-34, and problems encountered with the Ammonia Boiler Subsystem. The causes and the resolutions of these problems are discussed.
NASA Astrophysics Data System (ADS)
Barutello, Vivina; Jadanza, Riccardo D.; Portaluri, Alessandro
2016-01-01
It is well known that the linear stability of the Lagrangian elliptic solutions in the classical planar three-body problem depends on a mass parameter β and on the eccentricity e of the orbit. We consider only the circular case ( e = 0) but under the action of a broader family of singular potentials: α-homogeneous potentials, for α in (0, 2), and the logarithmic one. It turns out indeed that the Lagrangian circular orbit persists also in this more general setting. We discover a region of linear stability expressed in terms of the homogeneity parameter α and the mass parameter β, then we compute the Morse index of this orbit and of its iterates and we find that the boundary of the stability region is the envelope of a family of curves on which the Morse indices of the iterates jump. In order to conduct our analysis we rely on a Maslov-type index theory devised and developed by Y. Long, X. Hu and S. Sun; a key role is played by an appropriate index theorem and by some precise computations of suitable Maslov-type indices.
Variational Proof of the Existence of the Super-Eight Orbit in the Four-Body Problem
NASA Astrophysics Data System (ADS)
Shibayama, Mitsuru
2014-10-01
Using the variational method, Chenciner and Montgomery (Ann Math 152:881-901, 2000) proved the existence of an eight-shaped periodic solution of the planar three-body problem with equal masses. Just after the discovery, Gerver numerically found a similar periodic solution called "super-eight" in the planar four-body problem with equal mass. In this paper we prove the existence of the super-eight orbit by using the variational method. The difficulty of the proof is to eliminate the possibility of collisions. In order to solve it, we apply the scaling technique established by Tanaka (Ann Inst H Poincaré Anal Non Linéaire 10:215-238, 1993), (Proc Am Math Soc 122:275-284, 1994) and investigate the asymptotic behavior of a binary collision.
NASA Astrophysics Data System (ADS)
Geisel, Christopher D.
Strategies for designing three-dimensional spacecraft trajectories in a multi-body dynamical environment are investigated using four-dimensional Poincare maps. Unlike the planar circular restricted three-body problem, where a two-dimensional map provides a simplified view of a portion of the vast and often chaotic design space, the spatial problem requires a four-dimensional map to achieve an equivalent perspective. Such higher-dimensional maps present a visualization challenge. Furthermore, a spacecraft in the spatial problem can exhibit fundamentally more diverse and complex behavior than in the planar problem. A novel approach to four-dimensional-map-based design in the spatial circular restricted three-body problem is developed and applied to practical examples with real-world spaceflight applications involving three-dimensional trajectories in the Earth-Moon, Sun-Earth, and Uranus-Titania systems. Included in the approach is a method for representing, interpreting, and manipulating four-dimensional Poincare maps in an interactive, three-dimensional visual environment in which the fourth dimension is displayed using color. This "space-plus-color" method expands on the "color and rotation" method of Patsis and Zachilas (used for the study of motion in a galaxy) by applying additional tools and techniques enabling design in the circular restricted three-body problem. Design is often based on maps generated by many trajectories. Image manipulation in both spatial and color dimensions is accomplished iteratively using MATLABRTM and AvizoRTM. Four-dimensional-map-based design in the spatial circular restricted three-body problem is practical, and success is enabled by interactive tools and techniques in a visual environment. The design strategy is methodical and not restricted to any particular map formulation. Human insight is leveraged to determine reference solutions in a problem without a closed-form analytical solution. Estimates obtained through visual
NASA Astrophysics Data System (ADS)
Geller, D.
2007-06-01
A key component of satellite inspection and orbital rendezvous missions is relative attitude estimation and control. This paper analyzes a specific angles-only relative attitude estimation concept where it is assumed that a chaser spacecraft is capable of processing onboard imagery of a resident space object (RSO) and identifying the pixel locations of preselected RSO features. The pixel measurements along with chaser gyro and star camera data are processed by an extended Kalman filter to provide continuous estimates of the relative position and attitude. A novel linear covariance program is used to evaluate the effects of feature-tracking camera errors, gyro errors, star camera errors, measurement rates, and translation and rotational disturbances on relative navigation performance. Linear covariance techniques are further employed to evaluate the closed-loop performance of a relative attitude and position control system.
Problems of rate chemistry in the flight regimes of aeroassisted orbital transfer vehicles
NASA Technical Reports Server (NTRS)
Park, C.
1984-01-01
The dissociating and ionizing nonequilibrium flows behind a normal shock wave are calculated for the density and vehicle regimes appropriate for aeroassisted orbital transfer vehicles; the departure of vibrational and electron temperatures from the gas temperature as well as viscous transport phenomena are accounted for. From the thermodynamic properties so determined, radiative power emission is calculated using an existing code. The resulting radiation characteristics are compared with the available experimental data. Chemical parameters are varied to investigate their effect on the radiation characteristics. It is concluded that the current knowledge of rate chemistry leads to a factor-of-4 uncertainty in nonequilibrium radiation intensities. The chemical parameters that must be studied to improve the accuracy are identified.
NASA Astrophysics Data System (ADS)
Song, Ming; He, Xingsuo; He, Dongsheng
2016-10-01
We investigate solar sail displaced orbits in the Hill's restricted three-body problem, where the larger primary is an oblate spheroid in the system. Firstly, the model of solar sail equipped with a new version of reflectance control device is introduced. Next, dynamical model of the system with the larger primary an oblate spheroid is established and the Hill's restricted three-body problem with oblateness is built through appropriate simplifications. The collinear equilibrium points of the Hill's system varying with the variations of areas of absorption and thermal radiation of reflectance control devices in the solar sail, or the dimensionless characteristic acceleration of solar sail, or the oblateness of the larger primary are also investigated. Then, Linearization near the collinear equilibria of the system is applied. A linear quadratic regulator is used to stabilize the nonlinear system. The simulation reveals that solar sail displaced orbits in this system are doable and asymptotically stable by means of adjusting the pitch angle of solar sail and the area of absorption in reflectance control devices.
2015-04-15
Analysis of radio tracking data have enabled maps of the gravity field of Mercury to be derived. In this image, overlain on a mosaic obtained by MESSENGER's Mercury Dual Imaging System and illuminated with a shape model determined from stereo-photoclinometry, Mercury's gravity anomalies are depicted in colors. Red tones indicate mass concentrations, centered on the Caloris basin (center) and the Sobkou region (right limb). Such large-scale gravitational anomalies are signatures of subsurface structure and evolution. The north pole is near the top of the sunlit area in this view. http://photojournal.jpl.nasa.gov/catalog/PIA19285
NASA Astrophysics Data System (ADS)
McNanna, Mitch A.; Caprio, Mark A.
2014-09-01
Natural orbitals have been applied in atomic and molecular electronic-structure theory to increase the accuracy of calculations of observables for a many-particle system. However, unlike the electron-structure problem, the nuclear problem is translationally invariant. We created a testbed code to test the usefulness of natural orbitals as they may apply to translationally invariant problems. The relative Hamiltonian matrix of a two-particle system in one dimension is first calculated in a basis of antisymmetrized products of the harmonic oscillator eigenfunctions. The natural orbitals are then calculated for the resulting ground state, and the Hamiltonian matrix is recalculated using a two-particle basis built from the natural orbitals. The effect of basis size on the accuracy of the ground state energy calculation is explored. Natural orbitals have been applied in atomic and molecular electronic-structure theory to increase the accuracy of calculations of observables for a many-particle system. However, unlike the electron-structure problem, the nuclear problem is translationally invariant. We created a testbed code to test the usefulness of natural orbitals as they may apply to translationally invariant problems. The relative Hamiltonian matrix of a two-particle system in one dimension is first calculated in a basis of antisymmetrized products of the harmonic oscillator eigenfunctions. The natural orbitals are then calculated for the resulting ground state, and the Hamiltonian matrix is recalculated using a two-particle basis built from the natural orbitals. The effect of basis size on the accuracy of the ground state energy calculation is explored. Supported by the US NSF under grant NSF-PHY05-52843, the US DOE under grant DE-FG02-95ER-4093 and the Research Corporation for Science Advancement under a Cottrell Scholar Award.
ERIC Educational Resources Information Center
PENROSE, L.S.; SMITH, G.F.
BOTH CLINICAL AND PATHOLOGICAL ASPECTS AND MATHEMATICAL ELABORATIONS OF DOWN'S ANOMALY, KNOWN ALSO AS MONGOLISM, ARE PRESENTED IN THIS REFERENCE MANUAL FOR PROFESSIONAL PERSONNEL. INFORMATION PROVIDED CONCERNS (1) HISTORICAL STUDIES, (2) PHYSICAL SIGNS, (3) BONES AND MUSCLES, (4) MENTAL DEVELOPMENT, (5) DERMATOGLYPHS, (6) HEMATOLOGY, (7)…
ERIC Educational Resources Information Center
PENROSE, L.S.; SMITH, G.F.
BOTH CLINICAL AND PATHOLOGICAL ASPECTS AND MATHEMATICAL ELABORATIONS OF DOWN'S ANOMALY, KNOWN ALSO AS MONGOLISM, ARE PRESENTED IN THIS REFERENCE MANUAL FOR PROFESSIONAL PERSONNEL. INFORMATION PROVIDED CONCERNS (1) HISTORICAL STUDIES, (2) PHYSICAL SIGNS, (3) BONES AND MUSCLES, (4) MENTAL DEVELOPMENT, (5) DERMATOGLYPHS, (6) HEMATOLOGY, (7)…
Collision orbits and chaos in the free-fall three-body problem.
NASA Astrophysics Data System (ADS)
Tanikawa, K.; Umehara, H.
In this short report, the authors want to stress the chaotic nature of the final motions of the problem with reference to the distribution of binary collision curves and triple collision points. The calculation extends to the escapes at the first three collapses of the triple system. The Aarseth code to obtain the final motions is used.
NASA Astrophysics Data System (ADS)
Guzzo, Massimiliano
2001-07-01
I have improved the precision of the leap-frog symplectic integrators for perturbed Kepler problems at small eccentricities, without significant loss of CPU time. The integration scheme proposed is competitive, in some situations, with the so-called mixed variable integrators.
Ethical problems of interaction between ground-based personnel and orbital station crewmembers
NASA Astrophysics Data System (ADS)
Grigoriev, A. I.; Kozerenko, O. P.; Myasnikov, V. I.; Egorov, A. D.
Manned missions onboard orbital stations Salyut-6 and Salyut-7 have led us to the conclusion that a long-term space mission can be viewed as a complex socio-man-machine system whose effectiveness largely depends on the quality of interaction between its subsystems. When analyzing and assessing the reliability of this system, it is important to consider ethical aspects, because they concern human relations, permeating its very component and in the long run determining its efficiency. Psychological and medical examinations before, during and after manned missions have helped us to identify the major points of interaction of the subsystems which require adequate monitoring and optimization using socio-psychological and organization-technical approaches: arrangement and evaluation of the quality of work, arrangement of proper leisure, psychological comfort in the interpersonality and intergroup relations during prolonged space missions. This paper also discusses adaptive changes in the mental and physical state due to prolonged exposure to space flight factors such as microgravity and confinement.
INTELSAT 4 in orbit liquid slosh tests and problems in the theoretical analysis of the data
NASA Technical Reports Server (NTRS)
Slabinski, V. J.
1979-01-01
The destabilizing effect of the liquid on attitude nutation stability was determined from an extensive series of inorbit tests. The liquid slosh driving frequency ratio (rotor nutation frequency/rotor spin rate) was varied over the range of 0.58 to 0.70 for the tests by rotating the spacecraft antenna platform at different rates in inertial space. A rotor mounted accelerometer sensed the spacecraft nutation. The observed time constant for the nutation angle increase or decrease was corrected for the stabilizing contribution of the platform mounted pendulum dampers to yield the net destabilizing dedamping contribution from the liquid slosh. The in orbit tests show two unexpected maxima in the dedamping contribution at driving frequency ratios that vary with the propellant loading. The rotor nutation frequency at the maxima was about one-third of the lowest mode liquid slosh frequency given by ground test data for unspun tanks, and thus did not correspond to a simple resonance of the liquid. Ground tests with spinning systems produced the same maxima, but the phenomenon is not yet understood.
NASA Technical Reports Server (NTRS)
Matney, Mark
2006-01-01
One of the goals for NASA s Orbital Debris Program Office has been to accurately characterize the population of debris in the geosynchronous Earth orbit (GEO) environment. Most objects larger than about 1 meter in size are regularly tracked and catalogued by the US Space Surveillance System in the GEO regime. The consequence has been that most large intact GEO objects are tracked, but the vast majority of GEO debris fragments are not. Only in recent years have observations been dedicated to characterize the GEO debris population. NASA s efforts have concentrated on using wide field-of-view telescopes to make complete surveys of the GEO regime to better our statistical understanding of the GEO debris population. These telescopes operate in a staring mode, and only make limited short-arc measurements of the orbits. This information, while limited, allows the possibility of debiasing the observations and constructing statistical distributions of orbits in inclination and ascending node. Recent work suggests that we may be able to use statistical methods to estimate better orbit parameters despite the limited data. Both of these types of studies estimating statistical orbit distributions, and estimating accurate orbits using limited short-arc data have direct analogues in ongoing studies of near-Earth objects (NEO) such as asteroids and comets. This talk will describe the GEO study methods in use and being developed at NASA, and will discuss how such methods may or may not be applicable for NEO studies as well.
Orbiter global positioning system design and Ku-band problems investigation, exhibit B, revision 1
NASA Technical Reports Server (NTRS)
Chie, C. M.; Braun, W. R.
1981-01-01
The LinCom effort in supporting the JSC study of the use of the Global Positioning System (GPS) on the space shuttle and in Ku-band problem investigation is documented. LinCom was tasked to evaluate system implementation, performance, and integration aspects of the shuttle GPS and to provide independent technical assessment of reports submitted to JSC regarding integration studies, system studies and navigation analyses.
NASA Astrophysics Data System (ADS)
Fahr, Hans-Jörg; Siewert, Mark
2007-04-01
The question concerning the extent of the local spacetime has often been raised. At what circumsolar distance the well known Robertson-Walker spacetime of our expanding universe may become a valid approximation? Inside of that distance a local Schwarzschild metric, which permits to explain the Keplerian motions of planets within the frame of general relativity, must be applicable.We briefly analyze the historical answer to that question given by Einstein, Straus and their followers and show that till now this answer is unsatisfactory in many respects. We revisit the problem of local spacetime geometries in the light of their effects on local photon propagation in view of the radiopropagation phenomena detected with the NASA spaceprobes PIONEER-10/11, waiting for a satisfying answer for several decades now. Comparing radiosignals outgoing from the earth to the probe and ingoing again from the probe to the receiver on earth do show anomalous frequency shifts which presently find no explanation by anomalous non-Newtonian decelerations of these probes. Therefore we study cosmological conditions for the transfer of radiosignals between the earth and these distant probes based on time dependent local spacetime geometries. First we study the cosmological redshift of radiophotons during their propagation to the spaceprobe and show that this shift in fact explains the registered PIONEER phenomenon under the assumption that the full cosmological expansion of the universe also takes place locally. Though yielding the right magnitude, one finds that this assumption leads to a redshift instead of the observed blueshift. We then, however, show that theoretically motivated forms of time dependent local spacetime metrices in fact lead to a blueshift of the needed magnitude. The appropriate local space vacuole is characterized by a Schwarzschild metric of a central mass increasing with cosmic time. Though it is clear that further studies of this effect have to be carried out to
NASA Technical Reports Server (NTRS)
Boltz, F. W.
1984-01-01
An algorithm is presented for efficient p-iterative solution of the Lambert/Gauss orbit-determination problem using second-order Newton iteration. The algorithm is based on a universal transformation of Kepler's time-of-flight equation and approximate inverse solutions of this equation for short-way and long-way flight paths. The approximate solutions provide both good starting values for iteration and simplified computation of the second-order term in the iteration formula. Numerical results are presented which indicate that in many cases of practical significance (except those having collinear position vectors) the algorithm produces at least eight significant digits of accuracy with just two or three steps of iteration.
NASA Technical Reports Server (NTRS)
Boltz, F. W.
1984-01-01
An algorithm is presented for efficient p-iterative solution of the Lambert/Gauss orbit-determination problem using second-order Newton iteration. The algorithm is based on a universal transformation of Kepler's time-of-flight equation and approximate inverse solutions of this equation for short-way and long-way flight paths. The approximate solutions provide both good starting values for iteration and simplified computation of the second-order term in the iteration formula. Numerical results are presented which indicate that in many cases of practical significance (except those having collinear position vectors) the algorithm produces at least eight significant digits of accuracy with just two or three steps of iteration.
A review of uncertainty propagation in orbital mechanics
NASA Astrophysics Data System (ADS)
Luo, Ya-zhong; Yang, Zhen
2017-02-01
Orbital uncertainty propagation plays an important role in space situational awareness related missions such as tracking and data association, conjunction assessment, sensor resource management and anomaly detection. Linear models and Monte Carlo simulation were primarily used to propagate uncertainties. However, due to the nonlinear nature of orbital dynamics, problems such as low precision and intensive computation have greatly hampered the application of these methods. Aiming at solving these problems, many nonlinear uncertainty propagators have been proposed in the past two decades. To motivate this research area and facilitate the development of orbital uncertainty propagation, this paper summarizes the existing linear and nonlinear uncertainty propagators and their associated applications in the field of orbital mechanics. Frameworks of methods for orbital uncertainty propagation, the advantages and drawbacks of different methods, as well as potential directions for future efforts are also discussed.
Asian Monsoon Variations on Orbital-Millennial Scales and the `100 Thousand Year Problems'
NASA Astrophysics Data System (ADS)
Cheng, H.; Edwards, R. L.; Sinha, A.; Spoetl, C.; Yi, L.; Li, X.; Kathayat, G.
2016-12-01
Speleothem oxygen isotope records from China characterize changes in the Asian monsoon and global climate. We have now extended our Chinese record to cover the full uranium/thorium dating range: the last 640,000 years. The record's length, temporal precision, and correlations with both ice core and marine records allow us to further probe the enduring `100 ka problem'—i.e., why do large-amplitude ice age cycles and changes in eccentricity share common spectral power although the latter generates negligible change in insolation? Based on our record's timing, the ice age terminations are separated by 4 or 5 precession cycles, supporting the idea that the 100 ka ice age cycle is an average of discrete numbers of precession cycles. Furthermore, the suborbital component of monsoon rainfall variability exhibits power in precession and obliquity bands, and is nearly anti-phased with June 21 boreal insolation. These observations indicate that insolation, in part, paces the occurrence of millennial-scale events, including those associated with ice age terminations and `unfinished terminations'. In the East Asian summer monsoon (EASM) domain, Loess magnetic susceptibility records from the Chinese Loess Plateau (CLP) show that the EASM is dominated by 100 ka cycles, which is in contrast to the conventional notion that insolation changes caused by the 20 ka precession cycle are the primary driver of summer monsoon. These observations present another paradox, which we dub here as the `Chinese 100 ka problem'. The existing and new speleothem records from both China and India reinforce the idea that precession, rather than glacial-interglacial, cycles, is the dominant driver of both EASM and Indian summer monsoon variations. The lack of precession signals in the loess records from the CLP might stem partially from its unique climatological settings and complex nature of loess magnetic susceptibility proxy.
NASA Technical Reports Server (NTRS)
Oeftering, Richard C.; Bradish, Martin A.; Juergens, Jeffrey R.; Lewis, Michael J.
2011-01-01
The NASA Constellation Program is investigating and developing technologies to support human exploration of the Moon and Mars. The Component-Level Electronic-Assembly Repair (CLEAR) task is part of the Supportability Project managed by the Exploration Technology Development Program. CLEAR is aimed at enabling a flight crew to diagnose and repair electronic circuits in space yet minimize logistics spares, equipment, and crew time and training. For insight into actual space repair needs, in early 2008 the project examined the operational experience of the International Space Station (ISS) program. CLEAR examined the ISS on-orbit Problem Reporting and Corrective Action database for electrical and electronic system problems. The ISS has higher than predicted reliability yet, as expected, it has persistent problems. A goal was to identify which on-orbit electrical problems could be resolved by a component-level replacement. A further goal was to identify problems that could benefit from the additional diagnostic and test capability that a component-level repair capability could provide. The study indicated that many problems stem from a small set of root causes that also represent distinct component problems. The study also determined that there are certain recurring problems where the current telemetry instrumentation and built-in tests are unable to completely resolve the problem. As a result, the root cause is listed as unknown. Overall, roughly 42 percent of on-orbit electrical problems on ISS could be addressed with a component-level repair. Furthermore, 63 percent of on-orbit electrical problems on ISS could benefit from additional external diagnostic and test capability. These results indicate that in situ component-level repair in combination with diagnostic and test capability can be expected to increase system availability and reduce logistics. The CLEAR approach can increase the flight crew s ability to act decisively to resolve problems while reducing
NASA Astrophysics Data System (ADS)
Lightman, Alan; Gingerich, Owen
1992-02-01
The present historical and methodological consideration of scientific anomalies notes that some of these are recognized as such, after long neglect, only after the emergence of compelling explanations for their presence in the given theory in view of an alternative conceptual framework. These cases of 'retrorecognition' are indicative not merely of a significant characteristic of the process of conceptual development and scientific discovery, but of the bases for such process in human psychology. Attention is given to the illustrative cases of the 'flatness problem' in big bang theory, the perigee-opposition problem in Ptolemaic astronomy, the continental-fit problem in geology, and the equality of inertial and gravitational mass.
NASA Astrophysics Data System (ADS)
Haapala, Amanda F.; Howell, Kathleen C.
The Earth-Moon libration points are of interest for future missions and have been proposed for both storage of propellant and supplies for lunar missions and as locations to establish space-based facilities for human missions. Thus, further development of an available transport network in the vicinity of the Moon is valuable. In this investigation, a methodology to search for transfers between periodic lunar libration point orbits is developed, and a catalog of these transfers is established, assuming the dynamics associated with the Earth-Moon circular restricted three-body problem. Maneuver-free transfers, i.e. heteroclinic and homoclinic connections, are considered, as well as transfers that require relatively small levels of Δv. Considering the evolution of Earth-Moon transfers as the mass parameter is reduced, a relationship emerges between the available transfers in the Earth-Moon system and maneuver-free transfers that exist within the Hill three-body problem. The correlation between transfers in these systems is examined and offers insight into the existence of solutions within the catalog. To demonstrate the persistence of the catalog transfers in a higher-fidelity model, several solutions are transitioned to a Sun-Earth-Moon ephemeris model with the inclusion of solar radiation pressure and lunar gravity harmonics. The defining characteristics are preserved in the high-fidelity model, validating both the techniques employed for this investigation and the solutions computed within the catalog.
Kunisaki, Shaun M.
2012-01-01
Over the past decade, amniotic fluid-derived stem cells have emerged as a novel, experimental approach for the treatment of a wide variety of congenital anomalies diagnosed either in utero or postnatally. There are a number of unique properties of amniotic fluid stem cells that have allowed it to become a major research focus. These include the relative ease of accessing amniotic fluid cells in a minimally invasive fashion by amniocentesis as well as the relatively rich population of progenitor cells obtained from a small aliquot of fluid. Mesenchymal stem cells, c-kit positive stem cells, as well as induced pluripotent stem cells have all been derived from human amniotic fluid in recent years. This article gives a pediatric surgeon’s perspective on amniotic fluid stem cell therapy for the management of congenital anomalies. The current status in the use of amniotic fluid-derived stem cells, particularly as they relate as substrates in tissue engineering-based applications, is described in various animal models. A roadmap for further study and eventual clinical application is also proposed. PMID:22986340
Anomalies of a topologically ordered surface
Biswas, Deepnarayan; Thakur, Sangeeta; Ali, Khadiza; Balakrishnan, Geetha; Maiti, Kalobaran
2015-01-01
Bulk insulators with strong spin orbit coupling exhibit metallic surface states possessing topological order protected by the time reversal symmetry. However, experiments show vulnerability of topological states to aging and impurities. Different studies show contrasting behavior of the Dirac states along with plethora of anomalies, which has become an outstanding problem in material science. Here, we probe the electronic structure of Bi2Se3 employing high resolution photoemission spectroscopy and discover the dependence of the behavior of Dirac particles on surface terminations. The Dirac cone apex appears at different binding energies and exhibits contrasting shift on Bi and Se terminated surfaces with complex time dependence emerging from subtle adsorbed oxygen-surface atom interactions. These results uncover the surface states behavior of real systems and the dichotomy of topological and normal surface states important for device fabrication as well as realization of novel physics such as Majorana Fermions, magnetic monopole, etc. PMID:26041405
Geometry of halo and Lissajous orbits in the circular restricted three-body problem with drag forces
NASA Astrophysics Data System (ADS)
Pal, Ashok Kumar; Kushvah, Badam Singh
2015-01-01
In this paper, we determine the effect of radiation pressure, Poynting-Robertson drag and solar wind drag on the Sun-(Earth-Moon) restricted three-body problem. Here, we take the larger body of the Sun as a larger primary, and the Earth+Moon as a smaller primary. With the help of the perturbation technique, we find the Lagrangian points, and see that the collinear points deviate from the axis joining the primaries, whereas the triangular points remain unchanged in their configuration. We also find that Lagrangian points move towards the Sun when radiation pressure increases. We have also analysed the stability of the triangular equilibrium points and have found that they are unstable because of the drag forces. Moreover, we have computed the halo orbits in the third-order approximation using the Lindstedt-Poincaré method and have found the effect of the drag forces. According to this prevalence, the Sun-(Earth-Moon) model is used to design the trajectory for spacecraft travelling under drag forces.
Submillimeter Wave Astronomy Satellite (SWAS) Launch and Early Orbit Support Experiences
NASA Technical Reports Server (NTRS)
Kirschner, S.; Sedlak, J.; Challa, M.; Nicholson, A.; Sande, C.; Rohrbaugh, D.
1999-01-01
The Submillimeter Wave Astronomy Satellite (SWAS) was successfully launched on December 6, 1998 at 00:58 UTC. The two year mission is the fourth in the series of Small Explorer (SMEX) missions. SWAS is dedicated to the study of star formation and interstellar chemistry. SWAS was injected into a 635 km by 650 km orbit with an inclination of nearly 70 deg by an Orbital Sciences Corporation Pegasus XL launch vehicle. The Flight Dynamics attitude and navigation teams supported all phases of the early mission. This support included orbit determination, attitude determination, real-time monitoring, and sensor calibration. This paper reports the main results and lessons learned concerning navigation, support software, star tracker performance, magnetometer and gyroscope calibrations, and anomaly resolution. This includes information on spacecraft tip-off rates, first-day navigation problems, target acquisition anomalies, star tracker anomalies, and significant sensor improvements due to calibration efforts.
Spacecraft environmental anomalies expert system
NASA Technical Reports Server (NTRS)
Koons, H. C.; Gorney, D. J.
1988-01-01
A microcomputer-based expert system is being developed at the Aerospace Corporation Space Sciences Laboratory to assist in the diagnosis of satellite anomalies caused by the space environment. The expert system is designed to address anomalies caused by surface charging, bulk charging, single event effects and total radiation dose. These effects depend on the orbit of the satellite, the local environment (which is highly variable), the satellite exposure time and the hardness of the circuits and components of the satellite. The expert system is a rule-based system that uses the Texas Instruments Personal Consultant Plus expert system shell. The completed expert system knowledge base will include 150 to 200 rules, as well as a spacecraft attributes database, an historical spacecraft anomalies database, and a space environment database which is updated in near real-time. Currently, the expert system is undergoing development and testing within the Aerospace Corporation Space Sciences Laboratory.
Constraining Mass Anomalies Using Trans-dimensional Gravity Inversions
NASA Astrophysics Data System (ADS)
Izquierdo, K.; Montesi, L.; Lekic, V.
2016-12-01
The density structure of planetary interiors constitutes a key constraint on their composition, temperature, and dynamics. This has motivated the development of non-invasive methods to infer 3D distribution of density anomalies within a planet's interior using gravity observations made from the surface or orbit. On Earth, this information can be supplemented by seismic and electromagnetic observations, but such data are generally not available on other planets and inferences must be made from gravity observations alone. Unfortunately, inferences of density anomalies from gravity are non-unique and even the dimensionality of the problem - i.e., the number of density anomalies detectable in the planetary interior - is unknown. In this project, we use the Reversible Jump Markov chain Monte Carlo (RJMCMC) algorithm to approach gravity inversions in a trans-dimensional way, that is, considering the magnitude of the mass, the latitude, longitude, depth and number of anomalies itself as unknowns to be constrained by the observed gravity field at the surface of a planet. Our approach builds upon previous work using trans-dimensional gravity inversions in which the density contrast between the anomaly and the surrounding material is known. We validate the algorithm by analyzing a synthetic gravity field produced by a known density structure and comparing the retrieved and input density structures. We find excellent agreement between the input and retrieved structure when working in 1D and 2D domains. However, in 3D domains, comprehensive exploration of the much larger space of possible models makes search efficiency a key ingredient in successful gravity inversion. We find that upon a sufficiently long RJMCMC run, it is possible to use statistical information to recover a predicted model that matches the real model. We argue that even more complex problems, such as those involving real gravity acceleration data of a planet as the constraint, our trans-dimensional gravity
Gauge anomalies, gravitational anomalies, and superstrings
Bardeen, W.A.
1985-08-01
The structure of gauge and gravitational anomalies will be reviewed. The impact of these anomalies on the construction, consistency, and application of the new superstring theories will be discussed. 25 refs.
MAGSAT correlations with geoid anomalies. [magnetic anomalies in the western Gulf of Mexico
NASA Technical Reports Server (NTRS)
Bowin, C. O. (Principal Investigator)
1984-01-01
A digital data library of MAGSAT data is described and its applications and capabilities are reviewed. Polynomial trends were removed from each half-orbit in order to estimate and remove ring current effects from the data. The MAGSAT data in the Gulf of Mexico region was analyzed to define better the possible relation of the negative MAGSAT anomaly there to the negative residual geoid anomaly in the western Gulf of Mexico. Since the shape and location of the negative magnetic anomaly are variable depending upon the particular polynomial surface and curve orders used, no definitive conclusion as to the degree of correspondance between the residual geoid and MAGSAT lithosphere anomalies is offered.
NASA Astrophysics Data System (ADS)
Zamaro, M.; Biggs, J. D.
2015-07-01
The Martian moon Phobos is becoming an appealing destination for future scientific missions. The orbital dynamics around this planetary satellite is particularly complex due to the unique combination of both small mass-ratio and length-scale of the Mars-Phobos couple: the resulting sphere of influence of the moon is very close to its surface, therefore both the classical two-body problem and circular restricted three-body problem (CR3BP) do not provide an accurate approximation to describe the spacecraft's dynamics in the vicinity of Phobos. The aim of this paper is to extend the model of the CR3BP to consider the orbital eccentricity and the highly-inhomogeneous gravity field of Phobos, by incorporating the gravity harmonics series expansion into an elliptic R3BP, named ER3BP-GH. Following this, the dynamical substitutes of the Libration Point Orbits (LPOs) are computed in this more realistic model of the relative dynamics around Phobos, combining methodologies from dynamical systems theory and numerical continuation techniques. Results obtained show that the structure of the periodic and quasi-periodic LPOs differs substantially from the classical case without harmonics. Several potential applications of these natural orbits are presented to enable unique low-cost operations in the proximity of Phobos, such as close-range observation, communication, and passive radiation shielding for human spaceflight. Furthermore, their invariant manifolds are demonstrated to provide high-performance natural landing and take-off pathways to and from Phobos' surface, and transfers from and to Martian orbits. These orbits could be exploited in upcoming and future space missions targeting the exploration of this Martian moon.
NASA Astrophysics Data System (ADS)
Marcuzzi, J. P.; Leiva, A. M.; Briozzo, C. B.
Using characteristic curves of low energy fast periodic transfer orbits in the Earth-Moon planar circular restricted three body problem we constructed cost curves that enable the study of maneuvers between them. In an appropiate surface of section the numerical diagrams show regions where transfer maneuvers involve lower costs and that would allow determine family members which make the propelent minimum for these maneuvers. FULL TEXT IN SPANISH.
1991-09-01
regarding the effects of eccentricity and mass ratio on the linear stability of the triangular points have been published by Danby 2 11 and then later by...221 Bennett . Both Danby and Bennett have numerically generated graphic depictions of the linear stability region in the p-e plane. For the...21. J.M.A. Danby , "Stability of the Triangular Points in Elliptic Restricted Problem of Three Bodies," The Astronomical Journal, Volume 69, Number 2
The Mars Rover Spirit FLASH anomaly
NASA Technical Reports Server (NTRS)
Reeves, Glenn E.; Neilson, Tracy C.
2005-01-01
The Mars Exploration Rover 'Spirit' suffered a debilitating anomaly that prevented communication with Earth for several anxious days. With the eyes of the world upon us, the anomaly team used each scrap of information, our knowledge of the system, and sheer determination to analyze and fix the problem, then return the vehicle to normal operation. This paper will discuss the Spirit FLASH anomaly, including the drama of the investigation, the root cause and the lessons learned from the experience.
NASA Technical Reports Server (NTRS)
Kessler, D. J. (Compiler); Su, S. Y. (Compiler)
1985-01-01
Earth orbital debris issues and recommended future activities are discussed. The workshop addressed the areas of environment definition, hazards to spacecraft, and space object management. It concluded that orbital debris is a potential problem for future space operations. However, before recommending any major efforts to control the environment, more data are required. The most significant required data are on the population of debris smaller than 4 cm in diameter. New damage criteria are also required. When these data are obtained, they can be combined with hypervelocity data to evaluate the hazards to future spacecraft. After these hazards are understood, then techniques to control the environment can be evaluated.
Chiral anomalies and differential geometry
Zumino, B.
1983-10-01
Some properties of chiral anomalies are described from a geometric point of view. Topics include chiral anomalies and differential forms, transformation properties of the anomalies, identification and use of the anomalies, and normalization of the anomalies. 22 references. (WHK)
Columbus Payloads Flow Rate Anomalies
NASA Technical Reports Server (NTRS)
Quaranta, Albino; Bufano, Gaetana; DePalo, Savino; Holt, James M.; Szigetvari, Zoltan; Palumberi, Sergio; Hinderer, S.
2011-01-01
The Columbus Active Thermal Control System (ATCS) is the main thermal bus for the pressurized racks working inside the European laboratory. One of the ATCS goals is to provide proper water flow rate to each payload (P/L) by controlling actively the pressure drop across the common plenum distribution piping. Overall flow measurement performed by the Water Pump Assembly (WPA) is the only flow rate monitor available at system level and is not part of the feedback control system. At rack activation the flow rate provided by the system is derived on ground by computing the WPA flow increase. With this approach, several anomalies were raised during these 3 years on-orbit, with the indication of low flow rate conditions on the European racks FSL, BioLab, EDR and EPM. This paper reviews the system and P/Ls calibration approach, the anomalies occurred, the engineering evaluation on the measurement approach and the accuracy improvements proposed, the on-orbit test under evaluation with NASA and finally discusses possible short and long term solutions in case of anomaly confirmation.
A solution of the variational equations for elliptic orbits in rotating coordinates
NASA Technical Reports Server (NTRS)
Jones, J. B.
1980-01-01
For elliptic reference orbits, formulas are given for the perturbation state transition matrix of the two-body problem. The formulas relate perturbations expressed in a local vertical rotating coordinate system and are valid for motion in the linear neighborhood of reference orbits with e in the range of 0 to 1. The elements of the state transition matrix are expressed in terms of natural parameters (horizontal and radial velocity, radius, eccentricity, true anomaly, etc.) at the initial and final points. In addition to the general form, a simplified version, valid for small eccentricity orbits, is given.
NASA Astrophysics Data System (ADS)
Czarnik, Piotr; Dziarmaga, Jacek; Oleś, Andrzej M.
2017-07-01
The variational tensor network renormalization approach to two-dimensional (2D) quantum systems at finite temperature is applied to a model suffering the notorious quantum Monte Carlo sign problem—the orbital eg model with spatially highly anisotropic orbital interactions. Coarse graining of the tensor network along the inverse temperature β yields a numerically tractable 2D tensor network representing the Gibbs state. Its bond dimension D —limiting the amount of entanglement—is a natural refinement parameter. Increasing D we obtain a converged order parameter and its linear susceptibility close to the critical point. They confirm the existence of finite order parameter below the critical temperature Tc, provide a numerically exact estimate of Tc, and give the critical exponents within 1 % of the 2D Ising universality class.
2013-12-01
Uranus -Titania CR3BP model parameters .................................................... 166 Table 4.2 S/C osculating orbital elements one month...276 Figure 5.40 STK® 3-D view of the five major moons of Uranus in higher-fidelity model at capture maneuver epoch... Uranus -Titania systems. Included in the approach is a method for representing, interpreting, and manipulating four-dimensional Poincaré maps in an
NASA Astrophysics Data System (ADS)
Shornikov, Andrey; Starinova, Olga
2017-01-01
There is a problem to control spacecraft's motion near objects with irregular gravitational fields as asteroids. In this paper we present a mathematical model of spacecraft motion with an electric propulsion engine in an irregular non-spherical gravitational field of the asteroid Eros 433. We propose to use the model of single gravity points for simulation of the motion of a spacecraft in the irregular gravitational field. The equations of spacecraft motion are corresponding equations of the n-body problem. A boundary task of the control spacecraft's transfer between circular orbits from 200 km to 100 km is considered. Authors propose a combination of the Pontryagin's maximum principle and the Newton's step by step approximation as solutions methods for the boundary problem.
ISHM Anomaly Lexicon for Rocket Test
NASA Technical Reports Server (NTRS)
Schmalzel, John L.; Buchanan, Aubri; Hensarling, Paula L.; Morris, Jonathan; Turowski, Mark; Figueroa, Jorge F.
2007-01-01
Integrated Systems Health Management (ISHM) is a comprehensive capability. An ISHM system must detect anomalies, identify causes of such anomalies, predict future anomalies, help identify consequences of anomalies for example, suggested mitigation steps. The system should also provide users with appropriate navigation tools to facilitate the flow of information into and out of the ISHM system. Central to the ability of the ISHM to detect anomalies is a clearly defined catalog of anomalies. Further, this lexicon of anomalies must be organized in ways that make it accessible to a suite of tools used to manage the data, information and knowledge (DIaK) associated with a system. In particular, it is critical to ensure that there is optimal mapping between target anomalies and the algorithms associated with their detection. During the early development of our ISHM architecture and approach, it became clear that a lexicon of anomalies would be important to the development of critical anomaly detection algorithms. In our work in the rocket engine test environment at John C. Stennis Space Center, we have access to a repository of discrepancy reports (DRs) that are generated in response to squawks identified during post-test data analysis. The DR is the tool used to document anomalies and the methods used to resolve the issue. These DRs have been generated for many different tests and for all test stands. The result is that they represent a comprehensive summary of the anomalies associated with rocket engine testing. Fig. 1 illustrates some of the data that can be extracted from a DR. Such information includes affected transducer channels, narrative description of the observed anomaly, and the steps used to correct the problem. The primary goal of the anomaly lexicon development efforts we have undertaken is to create a lexicon that could be used in support of an associated health assessment database system (HADS) co-development effort. There are a number of significant
... Center for Coronary Artery Anomalies Doctors at the Texas Heart Institute's Center for Coronary Artery Anomalies (CCAA) ... comments. Terms of Use and Privacy Policy © Copyright Texas Heart Institute All rights reserved.
2016-07-26
Lymphatic Malformation; Generalized Lymphatic Anomaly (GLA); Central Conducting Lymphatic Anomaly; CLOVES Syndrome; Gorham-Stout Disease ("Disappearing Bone Disease"); Blue Rubber Bleb Nevus Syndrome; Kaposiform Lymphangiomatosis; Kaposiform Hemangioendothelioma/Tufted Angioma; Klippel-Trenaunay Syndrome; Lymphangiomatosis
NASA Technical Reports Server (NTRS)
Murad, P. A.
1993-01-01
Tsien's method is extended to treat the orbital motion of a body undergoing accelerations and decelerations. A generalized solution is discussed for the generalized case where a body undergoes azimuthal and radial thrust and the problem is further simplified for azimuthal thrust alone. Judicious selection of thrust could generate either an elliptic or hyperbolic trajectory. This is unexpected especially when the body has only enough energy for a lower state trajectory. The methodology is extended treating the problem of vehicle thrust for orbiting a sphere and vehicle thrust within the classical restricted three-body problem. Results for the latter situation can produce hyperbolic trajectories through eigen value decomposition. Since eigen values for no-thrust can be imaginary, thrust can generate real eigen values to describe hyperbolic trajectories. Keplerian dynamics appears to represent but a small subset of a much larger non-Keplerian domain especially when thrust effects are considered. The need for high thrust long duration space-based propulsion systems for changing a trajectory's canonical form is clearly demonstrated.
Galea, Joseph; Ellul, Sarah; Schembri, Aaron; Schembri-Wismayer, Pierre; Calleja-Agius, Jean
2014-01-01
Cardiac congenital abnormalities are a leading cause in neonatal mortality occurring in up to 1 in 200 of live births. Ebstein anomaly, also known as Kassamali anomaly, accounts for 1 percent of all congenital cardiac anomalies. This congenital abnormality involves malformation of the tricuspid valve and of the right ventricle. In this review, the causes of the anomaly are outlined and the pathophysiology is discussed, with a focus on the symptoms, management, and treatments available to date.
Analysis of spacecraft anomalies
NASA Technical Reports Server (NTRS)
Bloomquist, C. E.; Graham, W. C.
1976-01-01
The anomalies from 316 spacecraft covering the entire U.S. space program were analyzed to determine if there were any experimental or technological programs which could be implemented to remove the anomalies from future space activity. Thirty specific categories of anomalies were found to cover nearly 85 percent of all observed anomalies. Thirteen experiments were defined to deal with 17 of these categories; nine additional experiments were identified to deal with other classes of observed and anticipated anomalies. Preliminary analyses indicate that all 22 experimental programs are both technically feasible and economically viable.
NASA Astrophysics Data System (ADS)
Vaverka, Jakub; Pellinen-Wannberg, Asta; Kero, Johan; Mann, Ingrid; De Spiegeleer, Alexandre; Hamrin, Maria; Norberg, Carol; Pitkänen, Timo
2017-04-01
Detection of hypervelocity dust impacts on a spacecraft body by electric field instruments have been reported by several missions such as Voyager, WIND, Cassini, STEREO. The mechanism of this detection is still not completely understood and is under intensive laboratory investigation. A commonly accepted theory is based on re-collection of plasma cloud particles generated by a hypervelocity dust impact by a spacecraft surface and an electric field antenna resulting in a fast change in the potential of the spacecraft body and antenna. These changes can be detected as a short pulse measured by the electric field instrument. We present the first detection of dust impacts on the Earth-orbiting MMS and Cluster satellites. Each of the four MMS spacecraft provide probe-to-spacecraft potential measurements for their respective the six electric field antennas. This gives a unique view on signals generated by dust impacts and allow their reliable identification which is not possible for example on the Cluster spacecraft. We discuss various instrumental effects and solitary waves, commonly present in the Earth's magnetosphere, which can be easily misinterpreted as dust impacts. We show the influence of local plasma environment on dust impact detection for satellites crossing various regions of the Earth's magnetosphere where the concentration and the temperature of plasma particles change significantly.
Numerical anomalies mimicking physical effects
Menikoff, R.
1995-09-01
Numerical simulations of flows with shock waves typically use finite-difference shock-capturing algorithms. These algorithms give a shock a numerical width in order to generate the entropy increase that must occur across a shock wave. For algorithms in conservation form, steady-state shock waves are insensitive to the numerical dissipation because of the Hugoniot jump conditions. However, localized numerical errors occur when shock waves interact. Examples are the ``excess wall heating`` in the Noh problem (shock reflected from rigid wall), errors when a shock impacts a material interface or an abrupt change in mesh spacing, and the start-up error from initializing a shock as a discontinuity. This class of anomalies can be explained by the entropy generation that occurs in the transient flow when a shock profile is formed or changed. The entropy error is localized spatially but under mesh refinement does not decrease in magnitude. Similar effects have been observed in shock tube experiments with partly dispersed shock waves. In this case, the shock has a physical width due to a relaxation process. An entropy anomaly from a transient shock interaction is inherent in the structure of the conservation equations for fluid flow. The anomaly can be expected to occur whenever heat conduction can be neglected and a shock wave has a non-zero width, whether the width is physical or numerical. Thus, the numerical anomaly from an artificial shock width mimics a real physical effect.
Distance Metric Learning for Conditional Anomaly Detection.
Valko, Michal; Hauskrecht, Milos
2008-01-01
Anomaly detection methods can be very useful in identifying unusual or interesting patterns in data. A recently proposed conditional anomaly detection framework extends anomaly detection to the problem of identifying anomalous patterns on a subset of attributes in the data. The anomaly always depends (is conditioned) on the value of remaining attributes. The work presented in this paper focuses on instance-based methods for detecting conditional anomalies. The methods depend heavily on the distance metric that lets us identify examples in the dataset that are most critical for detecting the anomaly. To optimize the performance of the anomaly detection methods we explore and study metric learning methods. We evaluate the quality of our methods on the Pneumonia PORT dataset by detecting unusual admission decisions for patients with the community-acquired pneumonia. The results of our metric learning methods show an improved detection performance over standard distance metrics, which is very promising for building automated anomaly detection systems for variety of intelligent monitoring applications.
Distance Metric Learning for Conditional Anomaly Detection
Valko, Michal; Hauskrecht, Milos
2010-01-01
Anomaly detection methods can be very useful in identifying unusual or interesting patterns in data. A recently proposed conditional anomaly detection framework extends anomaly detection to the problem of identifying anomalous patterns on a subset of attributes in the data. The anomaly always depends (is conditioned) on the value of remaining attributes. The work presented in this paper focuses on instance–based methods for detecting conditional anomalies. The methods depend heavily on the distance metric that lets us identify examples in the dataset that are most critical for detecting the anomaly. To optimize the performance of the anomaly detection methods we explore and study metric learning methods. We evaluate the quality of our methods on the Pneumonia PORT dataset by detecting unusual admission decisions for patients with the community–acquired pneumonia. The results of our metric learning methods show an improved detection performance over standard distance metrics, which is very promising for building automated anomaly detection systems for variety of intelligent monitoring applications. PMID:20485452
NASA Astrophysics Data System (ADS)
Llibre, Jaume; Roberto, Luci Any
2009-07-01
For any positive integer N ≥ 2 we prove the existence of a new family of periodic solutions for the spatial restricted ( N +1)-body problem. In these solutions the infinitesimal particle is very far from the primaries. They have large inclinations and some symmetries. In fact we extend results of Howison and Meyer (J. Diff. Equ. 163:174-197, 2000) from N = 2 to any positive integer N ≥ 2.
Konstantinov, Igor E.
2009-01-01
Taussig-Bing anomaly is a rare congenital heart malformation that was first described in 1949 by Helen B. Taussig (1898–1986) and Richard J. Bing (1909–). Although substantial improvement has since been achieved in surgical results of the repair of the anomaly, management of the Taussig-Bing anomaly remains challenging. A history of the original description of the anomaly, the life stories of the individuals who first described it, and the current outcomes of its surgical management are reviewed herein. PMID:20069085
Recent Advances in Ionospheric Anomalies detection
NASA Astrophysics Data System (ADS)
Titov, Anton; Vyacheslav, Khattatov
2016-07-01
The variability of the parameters of the ionosphere and ionospheric anomalies are the subject of intensive research. It is widely known and studied in the literature ionospheric disturbances caused by solar activity, the passage of the terminator, artificial heating of high-latitude ionosphere, as well as seismic events. Each of the above types of anomalies is the subject of study and analysis. Analysis of these anomalies will provide an opportunity to improve our understanding of the mechanisms of ionospheric disturbances. To solve this problem are encouraged to develop a method of modeling the ionosphere, based on the assimilation of large amounts of observational data.
NASA Astrophysics Data System (ADS)
Murad, Paul A.
Orbit prediction of a body undergoing accelerations/decelerations is examined by extending Tsien's method. A solution for the generalized case is discussed for a body undergoing both azimuthal and radial thrust and the simplified case of azimuthal thrust alone. Judicious selection of thrust can generate either an elliptic or hyperbolic trajectory regardless of initial conditions. This is unexpected especially when the body has only enough energy for a lower state trajectory. The methodology is extended to treat vehicle thrust for orbiting a sphere and vehicle thrust within the classical restricted three-body problem. Results for the latter situation produce hyperbolic trajectories through eigenvalue decomposition. Since eigenvalues for no-thrust can be imaginary, thrust can generate real eigenvalues and hyperbolic trajectories. Keplerian dynamics represents a small subset of a much larger non-Keplerian domain that includes thrust effects. Consequently, the need for high thrust long-duration space-based propulsion systems for changing a trajectory's canonical form is clearly demonstrated.
Continental and oceanic magnetic anomalies: Enhancement through GRM
NASA Technical Reports Server (NTRS)
Vonfrese, R. R. B.; Hinze, W. J.
1985-01-01
In contrast to the POGO and MAGSAT satellites, the Geopotential Research Mission (GRM) satellite system will orbit at a minimum elevation to provide significantly better resolved lithospheric magnetic anomalies for more detailed and improved geologic analysis. In addition, GRM will measure corresponding gravity anomalies to enhance our understanding of the gravity field for vast regions of the Earth which are largely inaccessible to more conventional surface mapping. Crustal studies will greatly benefit from the dual data sets as modeling has shown that lithospheric sources of long wavelength magnetic anomalies frequently involve density variations which may produce detectable gravity anomalies at satellite elevations. Furthermore, GRM will provide an important replication of lithospheric magnetic anomalies as an aid to identifying and extracting these anomalies from satellite magnetic measurements. The potential benefits to the study of the origin and characterization of the continents and oceans, that may result from the increased GRM resolution are examined.
Gauge anomalies in Lorentz-violating QED
NASA Astrophysics Data System (ADS)
Santos, Tiago R. S.; Sobreiro, Rodrigo F.
2016-12-01
In this work we study the issue of gauge anomalies in Lorentz-violating QED. To do so, we opt to use the Becchi-Rouet-Stora-Tyutin formalism within the algebraic renormalization approach, reducing our study to a cohomology problem. Since this approach is independent of the renormalization scheme, the results obtained here are expected to be general. We find that the Lorentz-violating QED is free of gauge anomalies to all orders in perturbation theory.
NASA Technical Reports Server (NTRS)
Senent, Juan
2011-01-01
The first part of the paper presents some closed-form solutions to the optimal two-impulse transfer between fixed position and velocity vectors on Keplerian orbits when some constraints are imposed on the magnitude of the initial and final impulses. Additionally, a numerically-stable gradient-free algorithm with guaranteed convergence is presented for the minimum delta-v two-impulse transfer. In the second part of the paper, cooperative bargaining theory is used to solve some two-impulse transfer problems when the initial and final impulses are carried by different vehicles or when the goal is to minimize the delta-v and the time-of-flight at the same time.
Statistical Traffic Anomaly Detection in Time-Varying Communication Networks
2015-02-01
based anomaly detection methods are considered to be more economic and promising since they can identify novel attacks. In this work we focus on change ...82. [4] W. Lu and A. A. Ghorbani, “Network anomaly detection based on wavelet analysis ,” EURASIP Journal on Advances in Signal Processing, vol. 2009... dynamically . We formulate the anomaly detection problem as a binary composite hypothesis testing problem and develop a model-free and a model- based
Statistical Traffic Anomaly Detection in Time Varying Communication Networks
2015-02-01
based anomaly detection methods are considered to be more economic and promising since they can identify novel attacks. In this work we focus on change ...82. [4] W. Lu and A. A. Ghorbani, “Network anomaly detection based on wavelet analysis ,” EURASIP Journal on Advances in Signal Processing, vol. 2009... dynamically . We formulate the anomaly detection problem as a binary composite hypothesis testing problem and develop a model-free and a model- based
Competing Orders and Anomalies.
Moon, Eun-Gook
2016-08-08
A conservation law is one of the most fundamental properties in nature, but a certain class of conservation "laws" could be spoiled by intrinsic quantum mechanical effects, so-called quantum anomalies. Profound properties of the anomalies have deepened our understanding in quantum many body systems. Here, we investigate quantum anomaly effects in quantum phase transitions between competing orders and striking consequences of their presence. We explicitly calculate topological nature of anomalies of non-linear sigma models (NLSMs) with the Wess-Zumino-Witten (WZW) terms. The non-perturbative nature is directly related with the 't Hooft anomaly matching condition: anomalies are conserved in renormalization group flow. By applying the matching condition, we show massless excitations are enforced by the anomalies in a whole phase diagram in sharp contrast to the case of the Landau-Ginzburg-Wilson theory which only has massive excitations in symmetric phases. Furthermore, we find non-perturbative criteria to characterize quantum phase transitions between competing orders. For example, in 4D, we show the two competing order parameter theories, CP(1) and the NLSM with WZW, describe different universality class. Physical realizations and experimental implication of the anomalies are also discussed.
Competing Orders and Anomalies
NASA Astrophysics Data System (ADS)
Moon, Eun-Gook
2016-08-01
A conservation law is one of the most fundamental properties in nature, but a certain class of conservation “laws” could be spoiled by intrinsic quantum mechanical effects, so-called quantum anomalies. Profound properties of the anomalies have deepened our understanding in quantum many body systems. Here, we investigate quantum anomaly effects in quantum phase transitions between competing orders and striking consequences of their presence. We explicitly calculate topological nature of anomalies of non-linear sigma models (NLSMs) with the Wess-Zumino-Witten (WZW) terms. The non-perturbative nature is directly related with the ’t Hooft anomaly matching condition: anomalies are conserved in renormalization group flow. By applying the matching condition, we show massless excitations are enforced by the anomalies in a whole phase diagram in sharp contrast to the case of the Landau-Ginzburg-Wilson theory which only has massive excitations in symmetric phases. Furthermore, we find non-perturbative criteria to characterize quantum phase transitions between competing orders. For example, in 4D, we show the two competing order parameter theories, CP(1) and the NLSM with WZW, describe different universality class. Physical realizations and experimental implication of the anomalies are also discussed.
Competing Orders and Anomalies
Moon, Eun-Gook
2016-01-01
A conservation law is one of the most fundamental properties in nature, but a certain class of conservation “laws” could be spoiled by intrinsic quantum mechanical effects, so-called quantum anomalies. Profound properties of the anomalies have deepened our understanding in quantum many body systems. Here, we investigate quantum anomaly effects in quantum phase transitions between competing orders and striking consequences of their presence. We explicitly calculate topological nature of anomalies of non-linear sigma models (NLSMs) with the Wess-Zumino-Witten (WZW) terms. The non-perturbative nature is directly related with the ’t Hooft anomaly matching condition: anomalies are conserved in renormalization group flow. By applying the matching condition, we show massless excitations are enforced by the anomalies in a whole phase diagram in sharp contrast to the case of the Landau-Ginzburg-Wilson theory which only has massive excitations in symmetric phases. Furthermore, we find non-perturbative criteria to characterize quantum phase transitions between competing orders. For example, in 4D, we show the two competing order parameter theories, CP(1) and the NLSM with WZW, describe different universality class. Physical realizations and experimental implication of the anomalies are also discussed. PMID:27499184
Investigations of medium wavelength magnetic anomalies in the eastern Pacific using MAGSAT data
NASA Technical Reports Server (NTRS)
Harrison, C. G. A. (Principal Investigator)
1981-01-01
The suitability of using magnetic field measurements obtained by MAGSAT is discussed with regard to resolving the medium wavelength anomaly problem. A procedure for removing the external field component from the measured field is outlined. Various methods of determining crustal magnetizations are examined in light of satellite orbital parameters resulting in the selection of the equivalent source technique for evaluating scalar measurements. A matrix inversion of the vector components is suggested as a method for arriving at a scalar potential representation of the field.
Survey of Anomaly Detection Methods
Ng, B
2006-10-12
This survey defines the problem of anomaly detection and provides an overview of existing methods. The methods are categorized into two general classes: generative and discriminative. A generative approach involves building a model that represents the joint distribution of the input features and the output labels of system behavior (e.g., normal or anomalous) then applies the model to formulate a decision rule for detecting anomalies. On the other hand, a discriminative approach aims directly to find the decision rule, with the smallest error rate, that distinguishes between normal and anomalous behavior. For each approach, we will give an overview of popular techniques and provide references to state-of-the-art applications.
Generating unaveraged equations of motion in common orbital elements
NASA Astrophysics Data System (ADS)
Veras, Dimitri
2014-05-01
Cartesian equations of motion must be converted or integrated in order to impart information about the evolution of orbital elements such as the semimajor axis, eccentricity, inclination, longitude of ascending node, argument of pericentre and true anomaly. Alternatively, equations of motion in terms of only these orbital elements can reveal aspects of the motion simply by inspection. I advertise a quick method to generate such equations for perturbed two-body problems, where the perturbation may be arbitrarily large, and where no averaging is involved. I use the method to generate complete unaveraged equations from perturbations due to Poynting-Robertson drag, general relativity, mass loss, Galactic tides, and additional massive bodies under the guise of the general restricted few-body problem.
Anomaly Detection for Discrete Sequences: A Survey
Chandola, Varun; Banerjee, Arindam; Kumar, Vipin
2012-01-01
This survey attempts to provide a comprehensive and structured overview of the existing research for the problem of detecting anomalies in discrete/symbolic sequences. The objective is to provide a global understanding of the sequence anomaly detection problem and how existing techniques relate to each other. The key contribution of this survey is the classification of the existing research into three distinct categories, based on the problem formulation that they are trying to solve. These problem formulations are: 1) identifying anomalous sequences with respect to a database of normal sequences; 2) identifying an anomalous subsequence within a long sequence; and 3) identifying a pattern in a sequence whose frequency of occurrence is anomalous. We show how each of these problem formulations is characteristically distinct from each other and discuss their relevance in various application domains. We review techniques from many disparate and disconnected application domains that address each of these formulations. Within each problem formulation, we group techniques into categories based on the nature of the underlying algorithm. For each category, we provide a basic anomaly detection technique, and show how the existing techniques are variants of the basic technique. This approach shows how different techniques within a category are related or different from each other. Our categorization reveals new variants and combinations that have not been investigated before for anomaly detection. We also provide a discussion of relative strengths and weaknesses of different techniques. We show how techniques developed for one problem formulation can be adapted to solve a different formulation, thereby providing several novel adaptations to solve the different problem formulations. We also highlight the applicability of the techniques that handle discrete sequences to other related areas such as online anomaly detection and time series anomaly detection.
The mineralogy of global magnetic anomalies
NASA Technical Reports Server (NTRS)
Haggerty, S. E. (Principal Investigator)
1982-01-01
The Curie Balance was brought to operational stage and is producing data of a preliminary nature. Substantial problems experienced in the assembly and initial operation of the instrument were, for the most part, rectified, but certain problems still exist. Relationships between the geology and the gravity and MAGSAT anomalies of West Africa are reexamined in the context of a partial reconstruction of Gondwanaland.
The dynamic Allan Variance IV: characterization of atomic clock anomalies.
Galleani, Lorenzo; Tavella, Patrizia
2015-05-01
The number of applications where precise clocks play a key role is steadily increasing, satellite navigation being the main example. Precise clock anomalies are hence critical events, and their characterization is a fundamental problem. When an anomaly occurs, the clock stability changes with time, and this variation can be characterized with the dynamic Allan variance (DAVAR). We obtain the DAVAR for a series of common clock anomalies, namely, a sinusoidal term, a phase jump, a frequency jump, and a sudden change in the clock noise variance. These anomalies are particularly common in space clocks. Our analytic results clarify how the clock stability changes during these anomalies.
Gravitational anomalies in the solar system?
NASA Astrophysics Data System (ADS)
Iorio, Lorenzo
2015-02-01
Mindful of the anomalous perihelion precession of Mercury discovered by Le Verrier in the second half of the nineteenth century and its successful explanation by Einstein with his General Theory of Relativity in the early years of the twentieth century, discrepancies among observed effects in our Solar system and their theoretical predictions on the basis of the currently accepted laws of gravitation applied to known matter-energy distributions have the potential of paving the way for remarkable advances in fundamental physics. This is particularly important now more than ever, given that most of the universe seems to be made of unknown substances dubbed Dark Matter and Dark Energy. Should this not be directly the case, Solar system's anomalies could anyhow lead to advancements in either cumulative science, as shown to us by the discovery of Neptune in the first half of the nineteenth century, and technology itself. Moreover, investigations in one of such directions can serendipitously enrich the other one as well. The current status of some alleged gravitational anomalies in the Solar system is critically reviewed. They are: (a) Possible anomalous advances of planetary perihelia. (b) Unexplained orbital residuals of a recently discovered moon of Uranus (Mab). (c) The lingering unexplained secular increase of the eccentricity of the orbit of the Moon. (d) The so-called Faint Young Sun Paradox. (e) The secular decrease of the mass parameter of the Sun. (f) The Flyby Anomaly. (g) The Pioneer Anomaly. (h) The anomalous secular increase of the astronomical unit.
Bozkaya, Uğur
2011-12-14
In this research, orbital-optimized third-order Møller-Plesset perturbation theory (OMP3) and its spin-component and spin-opposite scaled variants (SCS-OMP3 and SOS-OMP3) are introduced. Using a Lagrangian-based approach, an efficient, quadratically convergent algorithm for variational optimization of the molecular orbitals (MOs) for third-order Møller-Plesset perturbation theory (MP3) is presented. Explicit equations for response density matrices, the MO gradient, and Hessian are reported in spin-orbital form. The OMP3, SCS-OMP3, and SOS-OMP3 approaches are compared with the second-order Møller-Plesset perturbation theory (MP2), MP3, coupled-cluster doubles (CCD), optimized-doubles (OD), and coupled-cluster singles and doubles (CCSD) methods. All these methods are applied to the O(4)(+), O(3), and seven diatomic molecules. Results demonstrate that the OMP3 and its variants provide significantly better vibrational frequencies than MP3, CCSD, and OD for the molecules where the symmetry-breaking problems are observed. For O(4)(+), the OMP3 prediction, 1343 cm(-1), for ω(6) (b(3u)) mode, where symmetry-breaking appears, is even better than presumably more reliable methods such as Brueckner doubles (BD), 1194 cm(-1), and OD, 1193 cm(-1), methods (the experimental value is 1320 cm(-1)). For O(3), the predictions of SCS-OMP3 (1143 cm(-1)) and SOS-OMP3 (1165 cm(-1)) are remarkably better than the more robust OD method (1282 cm(-1)); the experimental value is 1089 cm(-1). For the seven diatomics, again the SCS-OMP3 and SOS-OMP3 methods provide the lowest average errors, ∣Δω(e)∣ = 44 and ∣Δω(e)∣ = 35 cm(-1), respectively, while for OD, ∣Δω(e)∣ = 161 cm(-1)and CCSD ∣Δω(e)∣ = 106 cm(-1). Hence, the OMP3 and especially its spin-scaled variants perform much better than the MP3, CCSD, and more robust OD approaches for considered test cases. Therefore, considering both the computational cost and the reliability, SCS-OMP3 and SOS-OMP3 appear to be the
NASA Astrophysics Data System (ADS)
Bozkaya, Uǧur
2011-12-01
In this research, orbital-optimized third-order Møller-Plesset perturbation theory (OMP3) and its spin-component and spin-opposite scaled variants (SCS-OMP3 and SOS-OMP3) are introduced. Using a Lagrangian-based approach, an efficient, quadratically convergent algorithm for variational optimization of the molecular orbitals (MOs) for third-order Møller-Plesset perturbation theory (MP3) is presented. Explicit equations for response density matrices, the MO gradient, and Hessian are reported in spin-orbital form. The OMP3, SCS-OMP3, and SOS-OMP3 approaches are compared with the second-order Møller-Plesset perturbation theory (MP2), MP3, coupled-cluster doubles (CCD), optimized-doubles (OD), and coupled-cluster singles and doubles (CCSD) methods. All these methods are applied to the O4 +, O3, and seven diatomic molecules. Results demonstrate that the OMP3 and its variants provide significantly better vibrational frequencies than MP3, CCSD, and OD for the molecules where the symmetry-breaking problems are observed. For O4 +, the OMP3 prediction, 1343 cm-1, for ω6 (b3u) mode, where symmetry-breaking appears, is even better than presumably more reliable methods such as Brueckner doubles (BD), 1194 cm-1, and OD, 1193 cm-1, methods (the experimental value is 1320 cm-1). For O3, the predictions of SCS-OMP3 (1143 cm-1) and SOS-OMP3 (1165 cm-1) are remarkably better than the more robust OD method (1282 cm-1); the experimental value is 1089 cm-1. For the seven diatomics, again the SCS-OMP3 and SOS-OMP3 methods provide the lowest average errors, |Δωe| = 44 and |Δωe| = 35 cm-1, respectively, while for OD, |Δωe| = 161 cm-1and CCSD |Δωe| = 106 cm-1. Hence, the OMP3 and especially its spin-scaled variants perform much better than the MP3, CCSD, and more robust OD approaches for considered test cases. Therefore, considering both the computational cost and the reliability, SCS-OMP3 and SOS-OMP3 appear to be the best methods for the symmetry-breaking cases, based on
Behavioral economics without anomalies.
Rachlin, H
1995-01-01
Behavioral economics is often conceived as the study of anomalies superimposed on a rational system. As research has progressed, anomalies have multiplied until little is left of rationality. Another conception of behavioral economics is based on the axiom that value is always maximized. It incorporates so-called anomalies either as conflicts between temporal patterns of behavior and the individual acts comprising those patterns or as outcomes of nonexponential time discounting. This second conception of behavioral economics is both empirically based and internally consistent. PMID:8551195
Vascular anomalies in children.
Weibel, L
2011-11-01
Vascular anomalies are divided in two major categories: tumours (such as infantile hemangiomas) and malformations. Hemangiomas are common benign neoplasms that undergo a proliferative phase followed by stabilization and eventual spontaneous involution, whereas vascular malformations are rare structural anomalies representing morphogenetic errors of developing blood vessels and lymphatics. It is important to properly diagnose vascular anomalies early in childhood because of their distinct differences in morbidity, prognosis and need for a multidisciplinary management. We discuss a number of characteristic clinical features as clues for early diagnosis and identification of associated syndromes.
Arkani-Hamed, Nima; Cohen, Andrew G.; Georgi, Howard
2001-03-16
We discuss the form of the chiral anomaly on an S1/Z2 orbifold with chiral boundary conditions. We find that the 4-divergence of the higher-dimensional current evaluated at a given point in the extra dimension is proportional to the probability of finding the chiral zero mode there. Nevertheless the anomaly, appropriately defined as the five dimensional divergence of the current, lives entirely on the orbifold fixed planes and is independent of the shape of the zero mode. Therefore long distance four dimensional anomaly cancellation ensures the consistency of the higher dimensional orbifold theory.
Lithium and Ebstein's anomaly.
Sípek, A
1989-01-01
The article deals with Ebstein's anomaly, lithium and their relationship. Some studies suggest that lithium might be involved as a teratogen increasing the incidence of Ebstein's anomaly in the offspring of female patients with manio-depressive psychosis and lithium-administered during pregnancy. The second part of the article contains data on the incidence of Ebstein's anomaly in the Czech Socialist Republic between 1960 and 1985. The results indicate a steady rise in the incidence of this congenital malformation over the above period of time.
Statistical initial orbit determination
Taff, L.G.; Belkin, B.; Schweiter, G.A.; Sommar, K. D.H. Wagner Associates, Inc., Paoli, PA )
1992-02-01
For the ballistic missile initial orbit determination problem in particular, the concept of 'launch folders' is extended. This allows to decouple the observational data from the initial orbit determination problem per se. The observational data is only used to select among the possible orbital element sets in the group of folders. Monte Carlo simulations using up to 7200 orbital element sets are described. The results are compared to the true orbital element set and the one a good radar would have been able to produce if collocated with the optical sensor. The simplest version of the new method routinely outperforms the radar initial orbital element set by a factor of two in future miss distance. In addition, not only can a differentially corrected orbital element set be produced via this approach - after only two measurements of direction - but also an updated, meaningful, six-dimensional covariance array for it can be calculated. This technique represents a significant advance in initial orbit determination for this problem, and the concept can easily be extended to minor planets and artificial satellites. 9 refs.
Design and Implementation of an Anomaly Detector
Bagherjeiran, A; Cantu-Paz, E; Kamath, C
2005-07-11
This paper describes the design and implementation of a general-purpose anomaly detector for streaming data. Based on a survey of similar work from the literature, a basic anomaly detector builds a model on normal data, compares this model to incoming data, and uses a threshold to determine when the incoming data represent an anomaly. Models compactly represent the data but still allow for effective comparison. Comparison methods determine the distance between two models of data or the distance between a model and a point. Threshold selection is a largely neglected problem in the literature, but the current implementation includes two methods to estimate thresholds from normal data. With these components, a user can construct a variety of anomaly detection schemes. The implementation contains several methods from the literature. Three separate experiments tested the performance of the components on two well-known and one completely artificial dataset. The results indicate that the implementation works and can reproduce results from previous experiments.
Isotopic anomalies from neutron reactions during explosive carbon burning
NASA Technical Reports Server (NTRS)
Lee, T.; Schramm, D. N.; Wefel, J. P.; Blake, J. B.
1979-01-01
The heavy isotopic anomalies observed recently in the fractionation and unknown nuclear inclusions from the Allende meteorite are explained by neutron reactions during the explosive carbon burning (ECB). This model produces heavy anomalies in the same zone where Al-26 and O-16 are produced, thus reducing the number of source zones required for the isotopic anomalies. Unlike the classical r-process, the ECB n-process avoids the problem with the Sr anomaly and may resolve the problem of conflicting time scales between Al-26 and the r-process isotopes I-129 and Pu-244. Experimental studies of Zr and Ce isotopic composition are proposed to test this model.
Isotopic anomalies from neutron reactions during explosive carbon burning
NASA Technical Reports Server (NTRS)
Lee, T.; Schramm, D. N.; Wefel, J. P.; Blake, J. B.
1979-01-01
The heavy isotopic anomalies observed recently in the fractionation and unknown nuclear inclusions from the Allende meteorite are explained by neutron reactions during the explosive carbon burning (ECB). This model produces heavy anomalies in the same zone where Al-26 and O-16 are produced, thus reducing the number of source zones required for the isotopic anomalies. Unlike the classical r-process, the ECB n-process avoids the problem with the Sr anomaly and may resolve the problem of conflicting time scales between Al-26 and the r-process isotopes I-129 and Pu-244. Experimental studies of Zr and Ce isotopic composition are proposed to test this model.
Detection of Low Temperature Volcanogenic Thermal Anomalies with ASTER
NASA Astrophysics Data System (ADS)
Pieri, D. C.; Baxter, S.
2009-12-01
Predicting volcanic eruptions is a thorny problem, as volcanoes typically exhibit idiosyncratic waxing and/or waning pre-eruption emission, geodetic, and seismic behavior. It is no surprise that increasing our accuracy and precision in eruption prediction depends on assessing the time-progressions of all relevant precursor geophysical, geochemical, and geological phenomena, and on more frequently observing volcanoes when they become restless. The ASTER instrument on the NASA Terra Earth Observing System satellite in low earth orbit provides important capabilities in the area of detection of volcanogenic anomalies such as thermal precursors and increased passive gas emissions. Its unique high spatial resolution multi-spectral thermal IR imaging data (90m/pixel; 5 bands in the 8-12um region), bore-sighted with visible and near-IR imaging data, and combined with off-nadir pointing and stereo-photogrammetric capabilities make ASTER a potentially important volcanic precursor detection tool. We are utilizing the JPL ASTER Volcano Archive (http://ava.jpl.nasa.gov) to systematically examine 80,000+ ASTER volcano images to analyze (a) thermal emission baseline behavior for over 1500 volcanoes worldwide, (b) the form and magnitude of time-dependent thermal emission variability for these volcanoes, and (c) the spatio-temporal limits of detection of pre-eruption temporal changes in thermal emission in the context of eruption precursor behavior. We are creating and analyzing a catalog of the magnitude, frequency, and distribution of volcano thermal signatures worldwide as observed from ASTER since 2000 at 90m/pixel. Of particular interest as eruption precursors are small low contrast thermal anomalies of low apparent absolute temperature (e.g., melt-water lakes, fumaroles, geysers, grossly sub-pixel hotspots), for which the signal-to-noise ratio may be marginal (e.g., scene confusion due to clouds, water and water vapor, fumarolic emissions, variegated ground emissivity, and
Padmanabhan, Arjun; Thomas, Abin Varghese
2016-01-01
Although diaphragmatic anomalies such as an eventration and hiatus hernia are commonly encountered in incidental chest X-ray imaging, the presence of concomitant multiple anomalies is extremely rare. This is all the more true in adults. Herein, we present the case of a 75-year-old female, while undergoing a routine chest X-ray imaging, was found to have eventration of right hemidiaphragm along with a hiatus hernia as well. PMID:27625457
Anomalies and entanglement entropy
NASA Astrophysics Data System (ADS)
Nishioka, Tatsuma; Yarom, Amos
2016-03-01
We initiate a systematic study of entanglement and Rényi entropies in the presence of gauge and gravitational anomalies in even-dimensional quantum field theories. We argue that the mixed and gravitational anomalies are sensitive to boosts and obtain a closed form expression for their behavior under such transformations. Explicit constructions exhibiting the dependence of entanglement entropy on boosts is provided for theories on spacetimes with non-trivial magnetic fluxes and (or) non-vanishing Pontryagin classes.
Superstrings, anomalies and unification
Martinis, M.
1986-01-01
This recently concluded Adriatic Meeting provides coverage on the theoretical and experimental aspects of particle physics. Contents: Differential Geometry and String Theory; Supergravity from Superstrings; Gravitational Collapse and Quantum Mechanics; Interacting String Field Theory; Superstrings from 26 Dimensions and Superstring Field Theory and the Covariant Fermion Emission Vertex; Unification of Families; Phenomenology and Cosmology with Superstring Models; Effective Lagrangian Anomalies and Spontaneous Symmetry; Anomalies and Schwinger Terms and others.
NASA Technical Reports Server (NTRS)
Haxby, W. F.; Turcotte, D. L.
1978-01-01
In regions of slowly varying lateral density changes, the gravity and geoid anomalies may be expressed as power series expansions in topography. Geoid anomalies in isostatically compensated regions can be directly related to the local dipole moment of the density-depth distribution. This relationship is used to obtain theoretical geoid anomalies for different models of isostatic compensation. The classical Pratt and Airy models give geoid height-elevation relationships differing in functional form but predicting geoid anomalies of comparable magnitude. The thermal cooling model explaining ocean floor subsidence away from mid-ocean ridges predicts a linear age-geoid height relationship of 0.16 m/m.y. Geos 3 altimetry profiles were examined to test these theoretical relationships. A profile over the mid-Atlantic ridge is closely matched by the geoid curve derived from the thermal cooling model. The observed geoid anomaly over the Atlantic margin of North America can be explained by Airy compensation. The relation between geoid anomaly and bathymetry across the Bermuda Swell is consistent with Pratt compensation with a 100-km depth of compensation.
GEOS 3 data processing for the recovery of geoid undulations and gravity anomalies
NASA Technical Reports Server (NTRS)
Rapp, R. H.
1979-01-01
The paper discusses the analysis of GEOS 3 altimeter data for the determination of geoid heights and point and mean gravity anomalies. Methods are presented for determining the mean anomalies and mean undulations from the GEOS 3 altimeter data available by the end of September 1977 without having a complete set of precise orbits. The editing of the data is extensive to remove questionable data, although no filtering of the data is carried out. An adjustment process is carried out to eliminate orbit error and altimeter bias. Representative point anomaly values are computed to investigate anomaly behavior across the Bonin Trench and over the Patton seamounts.
Earth Radiation Budget Experiment (ERBE) scanner instrument anomaly investigation
NASA Technical Reports Server (NTRS)
Watson, N. D.; Miller, J. B.; Taylor, L. V.; Lovell, J. B.; Cox, J. W.; Fedors, J. C.; Kopia, L. P.; Holloway, R. M.; Bradley, O. H.
1985-01-01
The results of an ad-hoc committee investigation of in-Earth orbit operational anomalies noted on two identical Earth Radiation Budget Experiment (ERBE) Scanner instruments on two different spacecraft busses is presented. The anomalies are attributed to the bearings and the lubrication scheme for the bearings. A detailed discussion of the pertinent instrument operations, the approach of the investigation team and the current status of the instruments now in Earth orbit is included. The team considered operational changes for these instruments, rework possibilities for the one instrument which is waiting to be launched, and preferable lubrication considerations for specific space operational requirements similar to those for the ERBE scanner bearings.
Kepler does not orbit the Earth, rather it orbits the Sun in concert with the Earth, slowly drifting away from Earth. Every 61 Earth years, Kepler and Earth will pass by each other. Throughout the ...
... page: //medlineplus.gov/ency/article/001012.htm Orbital cellulitis To use the sharing features on this page, please enable JavaScript. Orbital cellulitis is an infection of the fat and muscles ...
Vaginal agenesis, the hymen, and associated anomalies.
Kimberley, N; Hutson, J M; Southwell, B R; Grover, S R
2012-02-01
Review anomalies in patients with vaginal agenesis. In particular, to clarify the impact of an absent hymen on the presence of other anomalies; on the success of creating a vagina with dilators; and on sexual function outcomes. Retrospective medical record review; questionnaire on sexual function. Gynecology service at a children's hospital and the practice of 1 gynecologist. All patients with vaginal agenesis were identified from the databases, as well as the subgroup in which hymenal status was known. Data regarding hymen, renal, skeletal, cardiac, and other anomalies; for women who had a neovagina, the technique used to create a functional vagina. Of 69 females (age range 2-70 years), renal tract anomalies (43.3%), vertebral anomalies (29%), cardiac anomalies (14.5%), and syndromes including Klippel-Feil (7%) and MURCS association (7%) were identified. Where hymenal status was known (n = 47), 31 were normal, and 16 had an absent hymen. Where the hymen was absent, renal agenesis was increased (odds ratio = 13.5, P < .001). There was no association between other anomalies and an absent hymen, or between the various anomalies. For women without a hymen, the likelihood of failing dilation therapy was increased (odds ratio = 21.7; P < .01]. An absent hymen makes renal agenesis more likely and increases the likelihood that dilator techniques will fail. This condition appears to be associated with reports of long-term problems with poor lubrication that are potentially related to the absence of the peri-hymenal Bartholin's glands. Copyright © 2012 North American Society for Pediatric and Adolescent Gynecology. Published by Elsevier Inc. All rights reserved.
Space Environment Automated Alerts & Anomaly Analysis Assistant (SEA5)
NASA Astrophysics Data System (ADS)
Boblitt, J. M.; Maddox, M. M.; Schiewe, T.; Jiang, D.; Zheng, Y.; Wold, A. M.
2016-12-01
Space Environment Automated Alerts & Anomaly Analysis Assistant (SEA5) is a comprehensive analysis and dissemination system that will provide past, present, and predicted space environment information for specific missions, orbits, and user-specified locations throughout the heliosphere, geospace, and on the ground. Existing space weather resources provide global and large-scale environmental information, but presently there are no highly-tailored services that target specific missions, orbits, or locations in space for any given time period. The targeted outcome of this project is to build an extensible software system for NASA that provides an unprecedented capability for (1) viewing space environment conditions for specific missions/orbits, (2) providing automated space weather alerts for specific missions/orbits, (3) assimilating and displaying spacecraft anomaly information, and (4) managing and displaying spacecraft/mission data.
Magnetic anomalies. [Magsat studies
NASA Technical Reports Server (NTRS)
Harrison, C. G. A.
1983-01-01
The implications and accuracy of anomaly maps produced using Magsat data on the scalar and vector magnetic field of the earth are discussed. Comparisons have been made between the satellite maps and aeromagnetic survey maps, showing smoother data from the satellite maps and larger anomalies in the aircraft data. The maps are being applied to characterize the structure and tectonics of the underlying regions. Investigations are still needed regarding the directions of magnetization within the crust and to generate further correlations between anomaly features and large scale geological structures. Furthermore, an increased data base is recommended for the Pacific Ocean basin in order to develop a better starting model for Pacific tectonic movements. The Pacific basin was large farther backwards in time and subduction zones surround the basin, thereby causing difficulties for describing the complex break-up scenario for Gondwanaland.
NASA Technical Reports Server (NTRS)
Dursch, Harry; Spear, Steve
1991-01-01
Spacecraft mechanisms are required to operate in the space environment for extended periods of time. A significant concern to the spacecraft designer is the possibility of metal to metal coldwelding or significant increases in friction. Coldwelding can occur between atomically clean metal surfaces when carefully prepared in a vacuum chamber on earth. The question is whether coldwelding occurs in orbit service conditions. The results of the System Special Investigation Group's (SIG's) investigation into whether coldwelding had occurred on any Long Duration Exposure Facility (LDEF) hardware are presented. The results of a literature search into previous ground based anomalies is also presented. Results show that even though there have been no documented on-orbit coldwelding related failures, precautions should be taken to ensure that coldwelding does not occur in the space environment and that seizure does not occur in the prelaunch or launch environment.
Lowry, R. B.
1985-01-01
Congenital anomalies account for a substantial proportion of childhood morbidity and mortality. They have become proportionately larger because of the decline of such other categories as infections or birth trauma. Approximately 3% of newborns have a serious handicapping or potentially lethal condition; in longterm studies the frequency is much higher. There is no good evidence to suggest that the rates of congenital anomalies are increasing, although this is a common perception. This article discusses diagnosis and management (especially genetic implications) of heart defects, neural tube defects, orofacial clefting, dislocated hip, clubfoot, and hypospadias. PMID:21274150
Orbiter entry aerothermodynamics
NASA Technical Reports Server (NTRS)
Ried, R. C.
1985-01-01
The challenge in the definition of the entry aerothermodynamic environment arising from the challenge of a reliable and reusable Orbiter is reviewed in light of the existing technology. Select problems pertinent to the orbiter development are discussed with reference to comprehensive treatments. These problems include boundary layer transition, leeward-side heating, shock/shock interaction scaling, tile gap heating, and nonequilibrium effects such as surface catalysis. Sample measurements obtained from test flights of the Orbiter are presented with comparison to preflight expectations. Numerical and wind tunnel simulations gave efficient information for defining the entry environment and an adequate level of preflight confidence. The high quality flight data provide an opportunity to refine the operational capability of the orbiter and serve as a benchmark both for the development of aerothermodynamic technology and for use in meeting future entry heating challenges.
Gravity anomaly detection: Apollo/Soyuz
NASA Technical Reports Server (NTRS)
Vonbun, F. O.; Kahn, W. D.; Bryan, J. W.; Schmid, P. E.; Wells, W. T.; Conrad, D. T.
1976-01-01
The Goddard Apollo-Soyuz Geodynamics Experiment is described. It was performed to demonstrate the feasibility of tracking and recovering high frequency components of the earth's gravity field by utilizing a synchronous orbiting tracking station such as ATS-6. Gravity anomalies of 5 MGLS or larger having wavelengths of 300 to 1000 kilometers on the earth's surface are important for geologic studies of the upper layers of the earth's crust. Short wavelength Earth's gravity anomalies were detected from space. Two prime areas of data collection were selected for the experiment: (1) the center of the African continent and (2) the Indian Ocean Depression centered at 5% north latitude and 75% east longitude. Preliminary results show that the detectability objective of the experiment was met in both areas as well as at several additional anomalous areas around the globe. Gravity anomalies of the Karakoram and Himalayan mountain ranges, ocean trenches, as well as the Diamantina Depth, can be seen. Maps outlining the anomalies discovered are shown.
Automated Network Anomaly Detection with Learning, Control and Mitigation
ERIC Educational Resources Information Center
Ippoliti, Dennis
2014-01-01
Anomaly detection is a challenging problem that has been researched within a variety of application domains. In network intrusion detection, anomaly based techniques are particularly attractive because of their ability to identify previously unknown attacks without the need to be programmed with the specific signatures of every possible attack.…
Automated Network Anomaly Detection with Learning, Control and Mitigation
ERIC Educational Resources Information Center
Ippoliti, Dennis
2014-01-01
Anomaly detection is a challenging problem that has been researched within a variety of application domains. In network intrusion detection, anomaly based techniques are particularly attractive because of their ability to identify previously unknown attacks without the need to be programmed with the specific signatures of every possible attack.…
Lunar magnetic anomalies and the Cayley formation
NASA Technical Reports Server (NTRS)
Strangway, D. W.; Gose, W. A.; Pearce, G. W.; Mcconnell, R. K.
1973-01-01
It is proposed that magnetic anomalies such as found at the Apollo 16 site are associated with breccia flows which cooled in place from above 770 C. The required field at the time that this process took place is a few thousand gamma. It is suggested that the surface and orbital magnetic anomalies are caused by basins filled with Cayley-like breccia flows to a thickness of the order of a kilometer. These breccia blankets settled in place from temperatures above 770 C and a thickness on the order of 1 km was welded to a level of 2 to 4 on Warner's scale. A base surge caused by impact or by a volcanic event could be the mechanism by which these breccia blankets were deposited.
2012-12-05
A 300-mile-long linear gravity anomaly on the far side of the moon has been revealed by gravity gradients measured by NASA GRAIL mission. GRAIL data are shown on the left, with red and blue corresponding to stronger gravity gradients.
[Ebstein anomaly and pregnancy].
Riesgo, Carmen Armida Iñigo; Gómez, Luis Guillermo Torres; Higareda, Salvador Hernández; Vargas, Juan Rafael Gómez
2008-08-01
The Ebstein's anomaly is a congenital malformation of the tricuspid valve and of the right ventricle that usually is associated with interauricular communication, foramen oval, and arrhythmias of Wolff-Parkinson-White syndrome type. To analyze the association between Ebstein's anomaly and pregnancy. A prospective study was made in five pregnant women's with Ebstein's anomaly without surgery. We analyzed the clinical history, physical examination, electrocardiogram, x-ray of thorax, Doppler color heart ultrasound, and fetal valoration by means of pelvic ecosonogram and cardiotocographic registry, and routinely prenatal paraclinic tests. We observed severe expansion of the ventricle and 3rd degree index of atrialization in two patients. In two pregnancies there were interatrial communication (patients with cyanosis) and in three was detected severe tricuspid insufficiency. The average of gestacional age was of 36.4 +/- 1.8 weeks. Two of the five pregnancies has preterm birth. Only one childbirth was short weight to gestational age. The rest stayed within percentile 10. There were no obits or neonatal deaths, either congenital abnormality by Doppler heart ultrasound. The pregnancy is well tolerated in patients with Ebstein's anomaly; nevertheless, participation of multidisciplinary team is recommended to establish the treatment.
Global anomalies in Chiral Lattice Gauge Theory
NASA Astrophysics Data System (ADS)
Bär, Oliver; Campos, Isabel
As first realized by Witten an SU(2) gauge theory coupled to a single Weyl fermion suffers from a global anomaly. This problem is addressed here in the context of the recent developments on chiral gauge theories on the lattice. We find Witten's anomaly manifests in the impossibility of defining globally a fermion measure that reproduces the proper continuum limit. Moreover, following Witten's original argument, we check numerically the crossing of the lowest eigenvalues of Neuberger's operator along a path connecting two gauge fields that differ by a topologically non-trivial gauge transformation.
Turyshev, Slava G; Toth, Viktor T
2010-01-01
Radio-metric Doppler tracking data received from the Pioneer 10 and 11 spacecraft from heliocentric distances of 20-70 AU has consistently indicated the presence of a small, anomalous, blue-shifted frequency drift uniformly changing with a rate of ∼ 6 × 10(-9) Hz/s. Ultimately, the drift was interpreted as a constant sunward deceleration of each particular spacecraft at the level of aP = (8.74 ± 1.33) × 10(-10) m/s(2). This apparent violation of the Newton's gravitational inverse-square law has become known as the Pioneer anomaly; the nature of this anomaly remains unexplained. In this review, we summarize the current knowledge of the physical properties of the anomaly and the conditions that led to its detection and characterization. We review various mechanisms proposed to explain the anomaly and discuss the current state of efforts to determine its nature. A comprehensive new investigation of the anomalous behavior of the two Pioneers has begun recently. The new efforts rely on the much-extended set of radio-metric Doppler data for both spacecraft in conjunction with the newly available complete record of their telemetry files and a large archive of original project documentation. As the new study is yet to report its findings, this review provides the necessary background for the new results to appear in the near future. In particular, we provide a significant amount of information on the design, operations and behavior of the two Pioneers during their entire missions, including descriptions of various data formats and techniques used for their navigation and radio-science data analysis. As most of this information was recovered relatively recently, it was not used in the previous studies of the Pioneer anomaly, but it is critical for the new investigation.
Apollo 17, 30 day failure and anomaly listing report
NASA Technical Reports Server (NTRS)
1973-01-01
The significant anomalies that occurred during the Apollo 17 mission are investigated. The discussion is divided into five major sections: command and service modules, lunar module, government-furnished equipment, lunar surface experiments, and orbital experiments. All times are elapsed time from range zero, established as the integral second before lift-off.
Statistical Anomaly Detection for Monitoring of Human Dynamics
NASA Astrophysics Data System (ADS)
Kamiya, K.; Fuse, T.
2015-05-01
Understanding of human dynamics has drawn attention to various areas. Due to the wide spread of positioning technologies that use GPS or public Wi-Fi, location information can be obtained with high spatial-temporal resolution as well as at low cost. By collecting set of individual location information in real time, monitoring of human dynamics is recently considered possible and is expected to lead to dynamic traffic control in the future. Although this monitoring focuses on detecting anomalous states of human dynamics, anomaly detection methods are developed ad hoc and not fully systematized. This research aims to define an anomaly detection problem of the human dynamics monitoring with gridded population data and develop an anomaly detection method based on the definition. According to the result of a review we have comprehensively conducted, we discussed the characteristics of the anomaly detection of human dynamics monitoring and categorized our problem to a semi-supervised anomaly detection problem that detects contextual anomalies behind time-series data. We developed an anomaly detection method based on a sticky HDP-HMM, which is able to estimate the number of hidden states according to input data. Results of the experiment with synthetic data showed that our proposed method has good fundamental performance with respect to the detection rate. Through the experiment with real gridded population data, an anomaly was detected when and where an actual social event had occurred.
On-orbit coldwelding: Fact or friction?
NASA Technical Reports Server (NTRS)
Dursch, Harry; Spear, Steve
1992-01-01
A study into the potential of on-orbit coldwelding occurring was completed. No instances of cold welding were found during deintegration and subsequent testing and analysis of LDEF hardware. This finding generated wide interest and indicated the need to review previous on-orbit coldwelding experiments and on-orbit spacecraft anomalies to determine whether the absence of coldwelding on LDEF was to be expected. Results show that even though there have been no documented cases of significant on-orbit coldwelding events occurring, precautions should be taken to ensure that neither coldwelding nor galling occurs in the space or prelaunch environment.
Gravity Anomaly Intersects Moon Basin
2012-12-05
A linear gravity anomaly intersecting the Crisium basin on the nearside of the moon has been revealed by NASA GRAIL mission. The GRAIL gravity gradient data are shown at left, with the location of the anomaly indicated.
Hawking radiation and covariant anomalies
Banerjee, Rabin; Kulkarni, Shailesh
2008-01-15
Generalizing the method of Wilczek and collaborators we provide a derivation of Hawking radiation from charged black holes using only covariant gauge and gravitational anomalies. The reliability and universality of the anomaly cancellation approach to Hawking radiation is also discussed.
XYY chromosome anomaly and schizophrenia.
Rajagopalan, M; MacBeth, R; Varma, S L
1998-02-07
Sex chromosome anomalies have been associated with psychoses, and most of the evidence is linked to the presence of an additional X chromosome. We report a patient with XYY chromosome anomaly who developed schizophrenia.
NASA Technical Reports Server (NTRS)
Lee, Shihyan; McIntire, Jeff; Oudari, Hassan
2012-01-01
The Visible/Infrared Imager Radiometer Suite (VIIRS) contains six dual gain bands in the reflective solar spectrum. The dual gain bands are designed to switch gain mode at pre-defined thresholds to achieve high resolution at low radiances while maintaining the required dynamic range for science. During pre-launch testing, an anomaly in the electronic response before transitioning from high to low gain was discovered and characterized. On-orbit, the anomaly was confirmed using MODIS data collected during Simultaneous Nadir Overpasses (SNOs). The analysis of the Earth scene data shows that dual gain anomaly can be determined at the orbital basis. To characterize the dual gain anomaly, the anomaly region and electronic offsets were tracked per week during the first 8 month of VIIRS operation. The temporal analysis shows the anomaly region can drift 20 DN and is impacted by detectors DC Restore. The estimated anomaly flagging regions cover 2.5 % of the high gain dynamic range and are consistent with prelaunch and on-orbit LUT. The prelaunch results had a smaller anomaly range (30-50 DN) and are likely the results of more stable electronics from the shorter data collection time. Finally, this study suggests future calibration efforts to focus on the anomaly's impact on science products and possible correction method to reduce uncertainties.
Lessons Learned from the Space Shuttle Engine Cutoff System (ECO) Anomalies
NASA Technical Reports Server (NTRS)
Martinez, Hugo E.; Welzyn, Ken
2011-01-01
The Space Shuttle Orbiter's main engine cutoff (ECO) system first failed ground checkout in April, 2005 during a first tanking test prior to Return-to-Flight. Despite significant troubleshooting and investigative efforts that followed, the root cause could not be found and intermittent anomalies continued to plague the Program. By implementing hardware upgrades, enhancing monitoring capability, and relaxing the launch rules, the Shuttle fleet was allowed to continue flying in spite of these unexplained failures. Root cause was finally determined following the launch attempts of STS-122 in December, 2007 when the anomalies repeated, which allowed drag-on instrumentation to pinpoint the fault (the ET feedthrough connector). The suspect hardware was removed and provided additional evidence towards root cause determination. Corrective action was implemented and the system has performed successfully since then. This white paper presents the lessons learned from the entire experience, beginning with the anomalies since Return-to-Flight through discovery and correction of the problem. To put these lessons in better perspective for the reader, an overview of the ECO system is presented first. Next, a chronological account of the failures and associated investigation activities is discussed. Root cause and corrective action are summarized, followed by the lessons learned.
Orbitals and orbital energies in DFT and TDDFT
NASA Astrophysics Data System (ADS)
Baerends, Evert Jan
The status and meaning of orbitals and orbital energies in the Kohn-Sham one-electron model of DFT has been controversial, in contrast to Hartree-Fock orbitals and orbital energies. We will argue the opposite: the exact Kohn-Sham orbitals of DFT are ''better'' than HF orbitals and their orbital energies are much closer to ionization energies than HF orbital energies are. This follows from the relation between the KS potential and the wavefunction, which can be cast in the form vs =vc , kin +vH +vxchole +vresp, where each term depends on the KS orbitals and the wavefunction (the one- or two-particle density matrices). The response potential vresp (r) = ∑ j ∞|/dj(r) | 2 ρ (r) Ij - ∑ i H|/ψs , i(r) | 2 ρ (r) (-ɛi) (dj is the Dyson orbital corresponding to ion state ΨjN - 1 , ψs , i is a Kohn-Sham orbital) enables the connection between ionization energies Ii and orbital energies ɛi to be made. For virtual orbitals and orbital energies similar statements can be made: the shapes and energies of the (exact) KS orbitals are much more realistic than those of the Hartree-Fock model or hybrid functionals. The HOMO-LUMO gap in molecules is very close to the optical gap, and very different from the fundamental gap. In solids the situation is very different, which is the well-known ''KS gap problem''. Again the response potential vresp (a good approximation to it) helps to solve this problem, affording a straigtforward correction method of the KS gap to the fundamental gap.
Gogan, Peter J.P.; Jessup, David A.; Barrett, Reginald H.
1988-01-01
Antler anomalies were evident in tule elk (Cervus elaphus nannodes) within 1 yr of reintroduction to Point Reyes, California (USA). These anomalies are consistent with previously described mineral deficiency-induced anomalies in cervids. The elk were judged deficient in copper. Low levels of copper in soils and vegetation at the release site, exacerbated by possible protein deficiency due to poor range conditions, are postulated as likely causes of the antler anomalies.
Rusdi, Lusiani; Azizi, Syahrir; Suwita, Christopher; Karina, Astrid; Nasution, Sally A
2016-10-01
A 27-year-old primiparous woman with 28 weeks gestational age was admitted to our hospital with worsening shortness of breath. She was diagnosed with Ebstein's anomaly three years ago, but preferred to be left untreated. The patient was not cyanotic and her vital signs were stable. Her ECG showed incomplete RBBB and prolonged PR-interval. Blood tests revealed mild anemia. Observation of two-dimensional echo with color flow Doppler study showed Ebstein's anomaly with PFO as additional defects, EF of 57%, LV and LA dilatation, RV atrialization, severe TR, and moderate PH with RVSP of 44.3 mmHg. The patient then underwent elective sectio caesaria at 30 weeks of gestational age; both the mother and her baby were alive and were in good conditions.
NASA Astrophysics Data System (ADS)
Bradlyn, Barry; Cano, Jennifer; Wang, Zhijun; Hirschberger, Max; Ong, N. Phuan; Bernevig, B. Andrei
Materials with intrinsic Weyl points should present exotic magnetotransport phenomena due to spectral flow between Weyl nodes of opposite chirality - the so-called ``chiral anomaly''. However, to date, the most definitive transport data showing the presence of a chiral anomaly comes from Dirac (not Weyl) materials. These semimetals develop Weyl fermions only in the presence of an externally applied magnetic field, when the four-fold degeneracy is lifted. In this talk we examine Berry phase effects on transport due to the emergence of these field-induced Weyl point and (in some cases) line nodes. We pay particular attention to the differences between intrinsic and field-induced Weyl fermions, from the point of view of kinetic theory. Finally, we apply our analysis to a particular material relevant to current experiments performed at Princeton.
Ferret Workflow Anomaly Detection System
2005-02-28
The Ferret workflow anomaly detection system project 2003-2004 has provided validation and anomaly detection in accredited workflows in secure...completed to accomplish a goal. Anomaly detection is the determination that a condition departs from the expected. The baseline behavior from which the
Sharing AIS Related Anomalies (SARA)
2016-03-01
related anomalies they uncover. This document proposes a taxonomy and a representation of the metadata and information ele- ments of the AIS-related...13 2.4 Potential Collaborators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3 Taxonomy of AIS...related Anomaly Types 15 3.1 AIS Anomalies Levels 1 and 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.2 Taxonomy
Congenital anomalies surveillance in Canada.
Lowry, R Brian
2008-01-01
Congenital anomalies (CA) are present in approximately 3% of all newborn babies and account for about 12% of paediatric hospital admissions. They represent an important public health problem. Surveillance is especially important so that preventive measures such as folic acid fortification can be properly assessed without resorting to a series of ad hoc studies. Canada's surveillance of CAs is weak, with only Alberta and British Columbia having established sytems. Most provinces have perinatal systems but their CA data are incomplete and they do not capture terminations of pregnancy. The same is true of the Public Health Agency of Canada's system. A new system, the Fetal Alert Network, has been proposed for Ontario, which represents a start but will require additional sources of ascertainment if it is to be a truly population-based system for Ontario.
Implications of 4 texture zeros mass matrices for neutrino anomalies
NASA Astrophysics Data System (ADS)
Gill, P. S.; Gupta, Manmohan
1998-04-01
Phenomenological 4 texture zeros mass matrices, successful in accommodating the CKM phenomenology, are used to simultaneously explain the three neutrino anomalies: the solar neutrino problem (SNP), the atmospheric neutrino problem (ANP), and the LSND anomaly. When the SNP is resolved through vacuum oscillations, we obtain a solution implying large mixing. In case the SNP is resolved through the MSW mechanism, the neutrino masses follow a ``natural'' hierarchy.
Pathogenesis of Vascular Anomalies
Boon, Laurence M.; Ballieux, Fanny; Vikkula, Miikka
2010-01-01
Vascular anomalies are localized defects of vascular development. Most of them occur sporadically, i.e. there is no familial history of lesions, yet in a few cases clear inheritance is observed. These inherited forms are often characterized by multifocal lesions that are mainly small in size and increase in number with patient’s age. On the basis of these inherited forms, molecular genetic studies have unraveled a number of inherited mutations giving direct insight into the pathophysiological cause and the molecular pathways that are implicated. Genetic defects have been identified for hereditary haemorrhagic telangiectasia (HHT), inherited cutaneomucosal venous malformation (VMCM), glomuvenous malformation (GVM), capillary malformation - arteriovenous malformation (CM-AVM), cerebral cavernous malformation (CCM) and some isolated and syndromic forms of primary lymphedema. We focus on these disorders, the implicated mutated genes and the underlying pathogenic mechanisms. We also call attention to the concept of Knudson’s double-hit mechanism to explain incomplete penetrance and the large clinical variation in expressivity of inherited vascular anomalies. This variability renders the making of correct diagnosis of the rare inherited forms difficult. Yet, the identification of the pathophysiological causes and pathways involved in them has had an unprecedented impact on our thinking of their etiopathogenesis, and has opened the doors towards a more refined classification of vascular anomalies. It has also made it possible to develop animal models that can be tested for specific molecular therapies, aimed at alleviating the dysfunctions caused by the aberrant genes and proteins. PMID:21095468
NASA Technical Reports Server (NTRS)
Colombo, O. L.
1984-01-01
The nature of the orbit error and its effect on the sea surface heights calculated with satellite altimetry are explained. The elementary concepts of celestial mechanics required to follow a general discussion of the problem are included. Consideration of errors in the orbits of satellites with precisely repeating ground tracks (SEASAT, TOPEX, ERS-1, POSEIDON, amongst past and future altimeter satellites) are detailed. The theoretical conclusions are illustrated with the numerical results of computer simulations. The nature of the errors in this type of orbits is such that this error can be filtered out by using height differences along repeating (overlapping) passes. This makes them particularly valuable for the study and monitoring of changes in the sea surface, such as tides. Elements of tidal theory, showing how these principles can be combined with those pertinent to the orbit error to make direct maps of the tides using altimetry are presented.
An interpretation of the Magsat anomalies of central Europe
NASA Astrophysics Data System (ADS)
Taylor, P. T.; Ravat, D.
1995-12-01
Magsat studies of central Europe have revealed correspondence between tectonic elements /geological structures and long-wavelength satellite-altitude anomalies. The most striking correlation is the two Magsat anomalies (one positive and the other negative) associated with either side of the Tornquist-Teisseyre Zone (TTZ). The TTZ, which extends from the Black Sea to the Baltic Sea, represents the structural boundary (suture) between the younger, thinner, and hotter crust of the Hercynide or Paleozoic block (negative anomaly) and the older, thicker, and colder crust of the East European Precambrian Platform (positive anomaly). This produces a gradient of approximately 18 nT (peak-to-trough) and a half-wavelength of 720 km along a Magsat orbit at 325 km altitude. This anomaly pair is the result of the juxtaposition of these two significantly different crustal blocks. To model this field, two irregular three-dimensional bodies were used to represent the Precambrian and Paleozoic crust. The former was modeled with a normal magnetization vector while the latter was modeled with a reverse vector. Aeromagnetic anomalies in western Germany and rock magnetic measurements from Germany and Scandinavia support a model in which reversely magnetic geologic units, extending from upper-crustal metasediments to mid-crustal sources produce this negative anomaly.
Anomaly Recovery and the Mars Exploration Rovers
NASA Technical Reports Server (NTRS)
Matijevic, Jacob R.; Dewell, Elizabeth A.
2006-01-01
The premise of the design of operations for the Mars Exploration Rovers (MER) is that the vehicles will drive each day. As a result, they will encounter some aspect of the terrain environment that cannot be anticipated or otherwise accommodated by the sequences linked onboard that day. The operations team then must correct the problem by planning then commanding the execution of a different drive the next day. Often other aspects of the operation on the surface of Mars: environmental changes, component degradation, errors in sequence design or execution, etc., lead to anomalies which must be addressed before normal operations can resume. The operational design that makes it possible to recover from a driving error each day also reduces the time needed to recover from anomalies. As an example of the efficiency achieved, less than 5% (about 30 sols out of 700 sols of operations) of the time on the surface has been devoted to recovery from anomalies for each vehicle. In this paper the major anomalies experienced by the MER rovers will be recounted and the streamlined approaches to addressing these problems described. The operational flexibility developed for these missions is also a function of the system design that anticipated a number of likely faults and conditions arising from uncertainty in sequence execution and environmental change. This design will be described as well as the considerations in operation that motivated this design. These considerations will likely be present in any future surface mission.
Anomaly Recovery and the Mars Exploration Rovers
NASA Technical Reports Server (NTRS)
Matijevic, Jacob R.; Dewell, Elizabeth A.
2006-01-01
The premise of the design of operations for the Mars Exploration Rovers (MER) is that the vehicles will drive each day. As a result, they will encounter some aspect of the terrain environment that cannot be anticipated or otherwise accommodated by the sequences linked onboard that day. The operations team then must correct the problem by planning then commanding the execution of a different drive the next day. Often other aspects of the operation on the surface of Mars: environmental changes, component degradation, errors in sequence design or execution, etc., lead to anomalies which must be addressed before normal operations can resume. The operational design that makes it possible to recover from a driving error each day also reduces the time needed to recover from anomalies. As an example of the efficiency achieved, less than 5% (about 30 sols out of 700 sols of operations) of the time on the surface has been devoted to recovery from anomalies for each vehicle. In this paper the major anomalies experienced by the MER rovers will be recounted and the streamlined approaches to addressing these problems described. The operational flexibility developed for these missions is also a function of the system design that anticipated a number of likely faults and conditions arising from uncertainty in sequence execution and environmental change. This design will be described as well as the considerations in operation that motivated this design. These considerations will likely be present in any future surface mission.
Earthquake prediction: Criterion for a tilt anomaly
Buckley, C.P.; Kohlenberger, C.W.
1980-07-10
A current approach to the problem of defining and detecting anomalous tilt behavior is presented. To establish what is considered to be normal tilt behavior, we isolate systematic signals such as hydrologic, thermal, tidal, cultural, and equipment-related effects from the tilt data. The kinds of tilt signals which remain after rejection of the systematic signals are designated by ourselves as residual tilt. Residual tilt consists of asystematic random noise and anomalous tilts. To affirm or deny the contention that an anomalous tilt is present in the data requires the formulation of a statistically valid judgment criteria. Our approach adopts the hypothesis that the random walk model is not significantly different from the residual tilt and allows the application of standard statistical tests to the problem of detecting anomalous varia ions in random noise. In our study of the data analyzed so far, we find that the boundary for detectability is inverse frequency dependent, and this limits the way in which anomalies can be treated. The fact that the magnitude of the anomaly decreases as the tilt data span increases suggests that further criterion development is necessary and tends to imply that longer anomalies will not be detected unless there is a correspondingly larger amplitude. From our studies of three earthquake-association anomalies this does not appear to be the case.
Hyperspectral Anomaly Detection by Graph Pixel Selection.
Yuan, Yuan; Ma, Dandan; Wang, Qi
2016-12-01
Hyperspectral anomaly detection (AD) is an important problem in remote sensing field. It can make full use of the spectral differences to discover certain potential interesting regions without any target priors. Traditional Mahalanobis-distance-based anomaly detectors assume the background spectrum distribution conforms to a Gaussian distribution. However, this and other similar distributions may not be satisfied for the real hyperspectral images. Moreover, the background statistics are susceptible to contamination of anomaly targets which will lead to a high false-positive rate. To address these intrinsic problems, this paper proposes a novel AD method based on the graph theory. We first construct a vertex- and edge-weighted graph and then utilize a pixel selection process to locate the anomaly targets. Two contributions are claimed in this paper: 1) no background distributions are required which makes the method more adaptive and 2) both the vertex and edge weights are considered which enables a more accurate detection performance and better robustness to noise. Intensive experiments on the simulated and real hyperspectral images demonstrate that the proposed method outperforms other benchmark competitors. In addition, the robustness of the proposed method has been validated by using various window sizes. This experimental result also demonstrates the valuable characteristic of less computational complexity and less parameter tuning for real applications.
Congenital anomalies in Primorsky region.
Kiku, P; Voronin, S; Golokhvast, K
2015-01-01
According to WHO hereditary diseases and congenital malformations contribute significantly to the health of population. Thus, the problems of epidemiology, clinical presentation, diagnosis and treatment of congenital abnormalities are of interest for many researchers [2]. In addition, the dynamic accounting for the incidence of congenital malformations and hereditary diseases allows the researchers to assess the ecological situation in the region [1]. The occurrence of congenital anomalies in the world varies; it depends heavily on how carefully the data is collected [4]. Multifactorial or polygenic diseases develop under the influence of environmental factors in the presence of defective genes. They can constitute up to 90% of all chronic pathology [2-5]. To determine the incidence of congenital anomalies under the influence of environmental factors. The study used the methodology of system evaluation of congenital anomalies incidence in Primorsky region, depending on bio-climatic and environmental conditions. The authors used health statistics for the period from 2000 to 2014, F.12 class for congenital abnormalities in adolescents and children that were compared in geographical and temporal aspects with environmental factors of 33 settlements in Primorsky region. The environment is represented by nature and climate (6 factor modules) and sanitation (7 factor modules) blocks of factors. When formalizing the information database of the environment a specially developed 10-point assessment scale was used. Statistical processing of the information was carried out using Pearson's chi-squared test and multiple regression method from SSPS application program package. The study found that over the 15-year period the level of congenital abnormalities in children increased by 27.5% and in adolescents - by 35.1%, and in 2014 it amounted to 1687.6 and 839.3 per 100 000 people, respectively. The predictive model shows a steady further growth of this pathology. The incidence
Total electron content anomalies associated with global VEI4 + volcanic eruptions during 2002-2015
NASA Astrophysics Data System (ADS)
Li, Wang; Guo, Jinyun; Yue, Jianping; Shen, Yi; Yang, Yang
2016-10-01
In previous studies, little attention has been paid to the total electron content (TEC) anomalies preceding the volcanic eruption. We analyze the coupling relationship between volcanic eruption and TEC anomalies, and discuss the spatial distribution of TEC anomalies associated with volcanic geographical location. We utilize the global ionosphere map (GIM) data from the Center for Orbit Determination in Europe (CODE) to analyze TEC variations before the global volcanic eruptions indicated by VEI (Volcanic Explosivity Index) 4 + from 2002 to 2015 with the sliding interquartile range method. The results indicate the occurrence rate of TEC anomalies before great volcanic eruptions is related with the volcanic type and geographical position. The occurrence rate of TEC anomalies before stratovolcano and caldera eruptions is higher than that before shield and pyroclastic shield eruptions, and the occurrence rate of TEC anomalies has a descending trend from low latitudes to high latitudes. The TEC anomalies before the volcanic eruptions in low-mid latitudes are within the volcanic affected areas, but do not coincide with the volcanic foci. The corresponding TEC anomalies could be observed in the conjugated region, and all the TEC anomalies in the volcanic affected areas are usually close to bounds of equatorial anomaly zones. However, the TEC anomalies preceding these eruptions in high latitudes usually surround the volcano, and no TEC anomalies appear in the conjugated region. These conclusions have potential applications to the prediction of great volcanic eruptions in the future.
The Hot Orbit: Orbital Cellulitis
Chaudhry, Imtiaz A.; Al-Rashed, Waleed; Arat, Yonca O.
2012-01-01
Orbital cellulitis is an uncommon condition previously associated with severe complications. If untreated, orbital cellulitis can be potentially sight and life threatening. It can affect both adults and children but has a greater tendency to occur in the pediatric age group. The infection most commonly originates from sinuses, eyelids or face, retained foreign bodies, or distant soources by hematogenous spread. It is characterized by eyelid edema, erythema, chemosis, proptosis, blurred vision, fever, headache, and double vision. A history of upper respiratory tract infection prior to the onset is very common especially in children. In the era prior to antibiotics, vision loss from orbital cellulitis was a dreaded complication. Currently, imaging studies for detection of orbital abcess, the use of antibiotics and early drainage have mitigated visual morbidity significantly. The purpose of this review is to describe current investigative strategies and management options in the treatment of orbital cellulitis, establish their effectiveness and possible complications due to late intervention. PMID:22346113
NASA Technical Reports Server (NTRS)
Vijayaraghavan, A.
1984-01-01
Hill's variational equations are solved analytically for the orbital perturbations of a spacecraft nominally in an elliptic orbit around a non-spherical body. The rotation of the central planet about its spin-axis is not considered in the analysis. The perturbations are restricted to the planetary gravitational harmonics only. An extremely simple algorithm is derived to transform the spherical harmonic potentials to the orbital coordinate system, and the resulting accelerations are shown to be simply trigonometric functions of the true anomaly. With the principal matrix solution for the differential equations of the adjoint system given in closed form, the orthogonality of the trigonometric functions makes it possible to obtain an analytic solution for the non-homogeneous problem, at intervals of 2 pi in true anomaly. The solution for orbital perturbations can be extended over several revolutions by applying well-known results from Floquet's theory. The technique is demonstrated with results presented on the spacecraft periapsis altitude for the forthcoming Venus Radar Mapper Mission.
NASA Technical Reports Server (NTRS)
Vijayaraghavan, A.
1984-01-01
Hill's variational equations are solved analytically for the orbital perturbations of a spacecraft nominally in an elliptic orbit around a non-spherical body. The rotation of the central planet about its spin-axis is not considered in the analysis. The perturbations are restricted to the planetary gravitational harmonics only. An extremely simple algorithm is derived to transform the spherical harmonic potentials to the orbital coordinate system, and the resulting accelerations are shown to be simply trigonometric functions of the true anomaly. With the principal matrix solution for the differential equations of the adjoint system given in closed form, the orthogonality of the trigonometric functions makes it possible to obtain an analytic solution for the non-homogeneous problem, at intervals of 2 pi in true anomaly. The solution for orbital perturbations can be extended over several revolutions by applying well-known results from Floquet's theory. The technique is demonstrated with results presented on the spacecraft periapsis altitude for the forthcoming Venus Radar Mapper Mission.
... Cavernous Sinus Thrombosis Inflammation of the Orbit Orbital Cellulitis Preseptal Cellulitis Tumors of the Orbit Any or all of ... Cavernous Sinus Thrombosis Inflammation of the Orbit Orbital Cellulitis Preseptal Cellulitis Tumors of the Orbit NOTE: This ...
Long wavelength gravity and topography anomalies
NASA Technical Reports Server (NTRS)
Watts, A. B.; Daly, S. F.
1981-01-01
It is shown that gravity and topography anomalies on the earth's surface may provide new information about deep processes occurring in the earth, such as those associated with mantle convection. Two main reasons are cited for this. The first is the steady improvement that has occurred in the resolution of the long wavelength gravity field, particularly in the wavelength range of a few hundred to a few thousand km, mainly due to increased coverage of terrestrial gravity measurements and the development of radar altimeters in orbiting satellites. The second reason is the large number of numerical and laboratory experiments of convection in the earth, including some with deformable upper and lower boundaries and temperature-dependent viscosity. The oceans are thought to hold the most promise for determining long wavelength gravity and topography anomalies, since their evolution has been relatively simple in comparison with that of the continents. It is also shown that good correlation between long wavelength gravity and topography anomalies exists over some portions of the ocean floor
Visual analytics of anomaly detection in large data streams
NASA Astrophysics Data System (ADS)
Hao, Ming C.; Dayal, Umeshwar; Keim, Daniel A.; Sharma, Ratnesh K.; Mehta, Abhay
2009-01-01
Most data streams usually are multi-dimensional, high-speed, and contain massive volumes of continuous information. They are seen in daily applications, such as telephone calls, retail sales, data center performance, and oil production operations. Many analysts want insight into the behavior of this data. They want to catch the exceptions in flight to reveal the causes of the anomalies and to take immediate action. To guide the user in finding the anomalies in the large data stream quickly, we derive a new automated neighborhood threshold marking technique, called AnomalyMarker. This technique is built on cell-based data streams and user-defined thresholds. We extend the scope of the data points around the threshold to include the surrounding areas. The idea is to define a focus area (marked area) which enables users to (1) visually group the interesting data points related to the anomalies (i.e., problems that occur persistently or occasionally) for observing their behavior; (2) discover the factors related to the anomaly by visualizing the correlations between the problem attribute with the attributes of the nearby data items from the entire multi-dimensional data stream. Mining results are quickly presented in graphical representations (i.e., tooltip) for the user to zoom into the problem regions. Different algorithms are introduced which try to optimize the size and extent of the anomaly markers. We have successfully applied this technique to detect data stream anomalies in large real-world enterprise server performance and data center energy management.
... Goodlick TA, Kay MD, Glaser JS, Tse DT, Chang WJ. Orbital disease and neuro-ophthalmology. In: Tasman ... 423. Review Date 8/20/2016 Updated by: Franklin W. Lusby, MD, ophthalmologist, Lusby Vision Institute, La ...
Khataminia, Gholamreza; Aghajanzadeh, Roja; Vazirianzadeh, Babak; Rahdar, Mahmoud
2011-01-01
Purpose To present a case of massive orbital myiasis. Case Report An 87-year-old debilitated woman suffering from left ocular pain of four days’ duration presented with a severely necrotized left orbit and several attached live larvae. The upper and lower eyelids and the eyeball were completely destroyed. She had history of eyelid surgery in the same eye due to a skin lesion, apparently some type of skin cancer, 15 years before. The larvae were identified as Chrysomya bezziana (Diptera: Calliphoridae) or old world screwworm fly. Conclusion Infestation of ocular and orbital tissues by fly larvae (ophthalmomyiasis) progresses rapidly and can completely destroy orbital tissues within days, especially in patients with poor general health. Treatment consists of removal of the larvae and surgical debridement. PMID:22454736
Physicochemical isotope anomalies
Esat, T.M.
1988-06-01
Isotopic composition of refractory elements can be modified, by physical processes such as distillation and sputtering, in unexpected patterns. Distillation enriches the heavy isotopes in the residue and the light isotopes in the vapor. However, current models appear to be inadequate to describe the detailed mass dependence, in particular for large fractionations. Coarse- and fine-grained inclusions from the Allende meteorite exhibit correlated isotope effects in Mg both as mass-dependent fractionation and residual anomalies. This isotope pattern can be duplicated by high temperature distillation in the laboratory. A ubiquitous property of meteoritic inclusions for Mg as well as for most of the other elements, where measurements exist, is mass-dependent fractionation. In contrast, terrestrial materials such as microtektites, tektite buttons as well as lunar orange and green glass spheres have normal Mg isotopic composition. A subset of interplanetary dust particles labelled as chondritic aggregates exhibit excesses in {sup 26}Mg and deuterium anomalies. Sputtering is expected to be a dominant mechanism in the destruction of grains within interstellar dust clouds. An active proto-sun as well as the present solar-wind and solar-flare flux are of sufficient intensity to sputter significant amounts of material. Laboratory experiments in Mg show widespread isotope effects including residual {sup 26}Mg excesses and mass dependent fractionation. It is possible that the {sup 26}Mg excesses in interplanetary dust is related to sputtering by energetic solar-wind particles. The implication if the laboratory distillation and sputtering effects are discussed and contrasted with the anomalies in meteoritic inclusions the other extraterrestrial materials the authors have access to.
NASA Technical Reports Server (NTRS)
2005-01-01
The structure of NASA's Mars Reconnaissance Orbiter spacecraft is constructed from composite panels of carbon layers over aluminum honeycomb, lightweight yet strong. This forms a basic structure or skeleton on which the instruments, electronics, propulsion and power systems can be mounted. The propellant tank is contained in the center of the orbiter's structure. This photo was taken at Lockheed Martin Space Systems, Denver, during construction of the spacecraft.
Detecting Patterns of Anomalies
2009-03-01
ct)P (bt|ct) , where A,B and C are mutually exclusive subsets of attributes with at most k elements . This ratio is similar to the previous formula , but...AND SUBTITLE Detecting Patterns of Anomalies 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e...to be dependent if, µ(A,B) ≥ βµ (2.1) where, βµ is a threshold parameter, set to a low value of 0.1 ( empirically ) in our experi- ments. Thus, for a
Hypercharged Anomaly Mediation
Dermisek, Radovan; Verlinde, Herman; Wang, L.-T.
2008-04-04
We show that, in string models with the minimal supersymmetric standard model residing on D-branes, the bino mass can be generated in a geometrically separated hidden sector. Hypercharge mediation thus naturally teams up with anomaly mediation. The mixed scenario predicts a distinctive yet viable superpartner spectrum, provided that the ratio {alpha} between the bino and gravitino mass lies in the range 0.05 < or approx. |{alpha}| < or approx. 0.25 and m{sub 3/2} > or approx. 35 TeV. We summarize some of the experimental signatures of this scenario.
NASA Astrophysics Data System (ADS)
Nardecchia, M.
2017-07-01
In December 2015, the ATLAS and CMS Collaborations presented results from data taken at the LHC with pp collisions at the center-of-mass energy of √{s} = 13{ TeV} . In the search for resonances decaying into two photons, both experiments observed a tantalising excess of events at an invariant mass of the photon pair of 750GeV. In this contribution, I will summarise some of the main phenomenological and theoretical aspects of this anomaly in terms of New Physics.
Detecting Biosphere anomalies hotspots
NASA Astrophysics Data System (ADS)
Guanche-Garcia, Yanira; Mahecha, Miguel; Flach, Milan; Denzler, Joachim
2017-04-01
The current amount of satellite remote sensing measurements available allow for applying data-driven methods to investigate environmental processes. The detection of anomalies or abnormal events is crucial to monitor the Earth system and to analyze their impacts on ecosystems and society. By means of a combination of statistical methods, this study proposes an intuitive and efficient methodology to detect those areas that present hotspots of anomalies, i.e. higher levels of abnormal or extreme events or more severe phases during our historical records. Biosphere variables from a preliminary version of the Earth System Data Cube developed within the CAB-LAB project (http://earthsystemdatacube.net/) have been used in this study. This database comprises several atmosphere and biosphere variables expanding 11 years (2001-2011) with 8-day of temporal resolution and 0.25° of global spatial resolution. In this study, we have used 10 variables that measure the biosphere. The methodology applied to detect abnormal events follows the intuitive idea that anomalies are assumed to be time steps that are not well represented by a previously estimated statistical model [1].We combine the use of Autoregressive Moving Average (ARMA) models with a distance metric like Mahalanobis distance to detect abnormal events in multiple biosphere variables. In a first step we pre-treat the variables by removing the seasonality and normalizing them locally (μ=0,σ=1). Additionally we have regionalized the area of study into subregions of similar climate conditions, by using the Köppen climate classification. For each climate region and variable we have selected the best ARMA parameters by means of a Bayesian Criteria. Then we have obtained the residuals by comparing the fitted models with the original data. To detect the extreme residuals from the 10 variables, we have computed the Mahalanobis distance to the data's mean (Hotelling's T^2), which considers the covariance matrix of the joint
Satellite magnetic anomalies over subduction zones - The Aleutian Arc anomaly
NASA Technical Reports Server (NTRS)
Clark, S. C.; Frey, H.; Thomas, H. H.
1985-01-01
Positive magnetic anomalies seen in MAGSAT average scalar anomaly data overlying some subduction zones can be explained in terms of the magnetization contrast between the cold subducted oceanic slab and the surrounding hotter, nonmagnetic mantle. Three-dimensional modeling studies show that peak anomaly amplitude and location depend on slab length and dip. A model for the Aleutian Arc anomaly matches the general trend of the observed MAGSAT anomaly if a slab thickness of 7 km and a relatively high (induced plus viscous) magnetization contrast of 4 A/m are used. A second source body along the present day continental margin is required to match the observed anomaly in detail, and may be modeled as a relic slab from subduction prior to 60 m.y. ago.
Discovering Recurring Anomalies in Text Reports Regarding Complex Space Systems
NASA Technical Reports Server (NTRS)
Zane-Ulman, Brett; Srivastava, Ashok N.
2005-01-01
Many existing complex space systems have a significant amount of historical maintenance and problem data bases that are stored in unstructured text forms. For some platforms, these reports may be encoded as scanned images rather than even searchable text. The problem that we address in this paper is the discovery of recurring anomalies and relationships between different problem reports that may indicate larger systemic problems. We will illustrate our techniques on data from discrepancy reports regarding software anomalies in the Space Shuttle. These free text reports are written by a number of different penp!e, thus the emphasis and wording varies considerably.
Anomaly Trends for Missions to Mars: Mars Global Surveyor and Mars Odyssey
NASA Technical Reports Server (NTRS)
Green, Nelson W.; Hoffman, Alan R.
2008-01-01
Conducted as a part of NASA Ultra-Reliability effort: Goal is to design for increased reliability in all NASA missions. Desire is to increase reliability by a factor of 10. Study provides a baseline for current technology. Analyzed anomalies for spacecraft orbiting Mars. Long lived spacecraft. Comparison with current rover missions and past orbiters. Looked for trends to assist design of future missions.
Chiral anomaly, bosonization, and fractional charge
Mignaco, J.A.; Monteiro, M.A.R.
1985-06-15
We present a method to evaluate the Jacobian of chiral rotations, regulating determinants through the proper-time method and using Seeley's asymptotic expansion. With this method we compute easily the chiral anomaly for ..nu.. = 4,6 dimensions, discuss bosonization of some massless two-dimensional models, and handle the problem of charge fractionization. In addition, we comment on the general validity of Fujikawa's approach to regulate the Jacobian of chiral rotations with non-Hermitian operators.
New Heteroclinic Orbits Coined
NASA Astrophysics Data System (ADS)
Wang, Haijun; Li, Chang; Li, Xianyi
We devote to studying the problem for the existence of homoclinic and heteroclinic orbits of Unified Lorenz-Type System (ULTS). Other than the known results that the ULTS has two homoclinic orbits to E0 = (0, 0, 0) for b = -2a1, d = -a1, a12 + a 2c > 0, e < 0 and two heteroclinic orbits to E1,2 = (±-2(a1 2+a2 c) e ,∓a1 a2 -2(a1 2+a2 c) e ,-a12+a2c a2e ) for b = -2a1, d = -a1, a12 + a 2c < 0, e > 0 on its invariant algebraic surface Q(x,y,z) = z - x2 2a2 = 0, formulated in the literature by Yang and Chen [2014], we seize two new heteroclinic orbits of this Unified Lorenz-Type System. Namely, we rigorously prove that this system has another two heteroclinic orbits to E0 and E± = (±b(a2 c-a1 d) a1e ,∓a1 a2 b(a2 c-a1 d) a1e , a1d-a2c a2e ) while no homoclinic orbit when a1 < 0, e < 0, a1 + d < 0, a2≠0, a2c - a1d > 0, b + 2a1 ≥ 0.
Zaleski, Witold A.; Houston, C. Stuart; Pozsonyi, J.; Ying, K. L.
1966-01-01
The majority of abnormal sex chromosome complexes in the male have been considered to be variants of Klinefelter's syndrome but an exception should probably be made in the case of the XXXXY individual who has distinctive phenotypic features. Clinical, radiological and cytological data on three new cases of XXXXY syndrome are presented and 30 cases from the literature are reviewed. In many cases the published clinical and radiological data were supplemented and re-evaluated. Mental retardation, usually severe, was present in all cases. Typical facies was observed in many; clinodactyly of the fifth finger was seen in nearly all. Radiological examination revealed abnormalities in the elbows and wrists in all the 19 personally evaluated cases, and other skeletal anomalies were very frequent. Cryptorchism is very common and absence of Leydig's cells may differentiate the XXXXY chromosome anomaly from polysomic variants of Klinefelter's syndrome. The relationship of this syndrome to Klinefelter's syndrome and to Down's syndrome is discussed. ImagesFig. 1Fig. 2Fig. 3Fig. 4Fig. 5Fig. 6Fig. 7Fig. 8Fig. 9Fig. 10Fig. 11Fig. 12Fig. 13Fig. 14Fig. 15 PMID:4222822
Automated anomaly detection processor
NASA Astrophysics Data System (ADS)
Kraiman, James B.; Arouh, Scott L.; Webb, Michael L.
2002-07-01
Robust exploitation of tracking and surveillance data will provide an early warning and cueing capability for military and civilian Law Enforcement Agency operations. This will improve dynamic tasking of limited resources and hence operational efficiency. The challenge is to rapidly identify threat activity within a huge background of noncombatant traffic. We discuss development of an Automated Anomaly Detection Processor (AADP) that exploits multi-INT, multi-sensor tracking and surveillance data to rapidly identify and characterize events and/or objects of military interest, without requiring operators to specify threat behaviors or templates. The AADP has successfully detected an anomaly in traffic patterns in Los Angeles, analyzed ship track data collected during a Fleet Battle Experiment to detect simulated mine laying behavior amongst maritime noncombatants, and is currently under development for surface vessel tracking within the Coast Guard's Vessel Traffic Service to support port security, ship inspection, and harbor traffic control missions, and to monitor medical surveillance databases for early alert of a bioterrorist attack. The AADP can also be integrated into combat simulations to enhance model fidelity of multi-sensor fusion effects in military operations.
Einstein, Entropy and Anomalies
NASA Astrophysics Data System (ADS)
Sirtes, Daniel; Oberheim, Eric
2006-11-01
This paper strengthens and defends the pluralistic implications of Einstein's successful, quantitative predictions of Brownian motion for a philosophical dispute about the nature of scientific advance that began between two prominent philosophers of science in the second half of the twentieth century (Thomas Kuhn and Paul Feyerabend). Kuhn promoted a monistic phase-model of scientific advance, according to which a paradigm driven `normal science' gives rise to its own anomalies, which then lead to a crisis and eventually a scientific revolution. Feyerabend stressed the importance of pluralism for scientific progress. He rejected Kuhn's model arguing that it fails to recognize the role that alternative theories can play in identifying exactly which phenomena are anomalous in the first place. On Feyerabend's account, Einstein's predictions allow for a crucial experiment between two incommensurable theories, and are an example of an anomaly that could refute the reigning paradigm only after the development of a competitor. Using Kuhn's specification of a disciplinary matrix to illustrate the incommensurability between the two paradigms, we examine the different research strategies available in this peculiar case. On the basis of our reconstruction, we conclude by rebutting some critics of Feyerabend's argument.
NASA Technical Reports Server (NTRS)
Tang, Charles C. H.
1988-01-01
By using Von Zeipel's generating function procedure the perturbing earth gravitational potential is averaged with respect to the fast variable (mean anomaly) and a set of 'fictitous' mean orbital elements which can be used as a long-term satellite orbit predictor is obtained. The set of elements is shown to be a function of the nonlinear square of the second zonal harmonic coefficient. It is found that the long-term orbit prediction using the 'fictitous' mean elements is as accurate as that using the osculating elements, but has a computing speed about two orders of magnitude faster. For short-term orbit predictions, the osculating elements approach must be used.
DSCS II. Battery Anomaly Investigation Satellites 9437 and 9438.
1980-04-25
and is approved for publica- tion. Publication of this report does not constitute Air Force approval of the report’s findings or conclusions . It is...Contract F04701-77-C-0118 TRW Defense and Space Systems Group One Space Park Redondo Beach, California 90278 CONTENTS Page 1. SUMMARY AND CONCLUSIONS 1-1...1.1 Scope 1-1 1.2 Anomaly Description 1-I 1.3 Anomaly Investigations 1-1 1.4 Conclusions 1-1 2. BACKGROUND 2-1 2.1 Power Subsystem 2-1 2.2 Orbital
Prevalence and pathogenesis of congenital anomalies in cerebral palsy
Pharoah, Peter O D
2007-01-01
Background It has been hypothesised that cerebral palsy (CP) and other congenital anomalies are attributable to feto–fetal transfusion problems in a monochorionic multiple gestation. Thus more than one organ could be compromised leading to the coexistence of two or more anomalies in a fetus. Such anomalies in a singleton birth may be attributable to early demise of the co‐conceptus as a vanishing twin. Aim To determine whether the coexistence of congenital anomalies and CP is greater than a chance finding by comparing the prevalence of congenital anomalies in children with CP with that in the general population of children. Methods A population‐based register of children with CP born in 1966–1991 in the counties of Merseyside and Cheshire, UK, comprised the index population. Coexisting congenital anomalies were recorded. For comparison the population prevalence of congenital anomalies was obtained from eight congenital malformation registers in the UK. Results Children with CP were found to have highly significant increases in risk for microcephaly, isolated hydrocephaly, congenital anomalies of the eye, congenital cardiac anomalies, cleft lip and/or palate and congenital dislocation of the hips and talipes (p<0.001) and atresias of the oesophagus (p<0.001) and intestines (p<0.01). The relative risks ranged from 3.1 (95% CI 1.9 to 4.8; p<0.001) for congenital malformations of the cardiac septa to 116.09 (95% CI 84.0 to 162.3; p<0.001) for microcephaly. Conclusions Congenital anomalies in children with CP are found much more frequently than expected by chance. A common pathogenic mechanism may account for the coexistence of disparate congenital anomalies. A hypothesis is proposed for such a common pathogenic mechanism. PMID:17428819
Orbital science's 'Bermuda Triangle'
NASA Astrophysics Data System (ADS)
Sherrill, Thomas J.
1991-02-01
The effects of a part of the inner Van Allen belt lying closest to the earth, known as the South Atlantic Anomaly (SAA) upon spacecraft including the Hubble Space Telescope (HST), are discussed. The area consists of positively charged ions and electrons from the Van Allen Belt which become trapped in the earth's dipole field. Contor maps representing the number of protons per square centimeter per second having energies greater than 10 million electron volts are presented. It is noted that the HST orbit causes it to spend about 15 percent of its time in the SAA, but that, unlike the experience with earlier spacecraft, the satellite's skin, internal structure, and normal electronic's packaging provides sufficient protection against eletrons, although some higher energy protons still get through. Various charged particle effects which can arise within scientific instruments including fluorescence, Cerenkov radiation, and induced radioactivity are described.
Prevalence and distribution of selected dental anomalies among saudi children in Abha, Saudi Arabia
2016-01-01
Background Dental anomalies are not an unusual finding in routine dental examination. The effect of dental anomalies can lead to functional, esthetic and occlusal problems. The Purpose of the study was to determine the prevalence and distribution of selected developmental dental anomalies in Saudi children. Material and Methods The study was based on clinical examination and Panoramic radiographs of children who visited the Pediatric dentistry clinics at King Khalid University College of Dentistry, Saudi Arabia. These patients were examined for dental anomalies in size, shape, number, structure and position. Data collected were entered and analyzed using statistical package for social sciences version. Results Of the 1252 children (638 Boys, 614 girls) examined, 318 subjects (25.39%) presented with selected dental anomalies. The distribution by gender was 175 boys (27.42%) and 143 girls (23.28%). On intergroup comparison, number anomalies was the most common anomaly with Hypodontia (9.7%) being the most common anomaly in Saudi children, followed by hyperdontia (3.5%). The Prevalence of size anomalies were Microdontia (2.6%) and Macrodontia (1.8%). The prevalence of Shape anomalies were Talon cusp (1.4%), Taurodontism (1.4%), Fusion (0.8%).The prevalence of Positional anomalies were Ectopic eruption (2.3%) and Rotation (0.4%). The prevalence of structural anomalies were Amelogenesis imperfecta (0.3%) Dentinogenesis imperfecta (0.1%). Conclusions A significant number of children had dental anomaly with Hypodontia being the most common anomaly and Dentinogenesis imperfecta being the rare anomaly in the study. Early detection and management of these anomalies can avoid potential orthodontic and esthetic problems in a child. Key words:Dental anomalies, children, Saudi Arabia. PMID:27957258
Congenital anomalies of kidney and urinary tract.
Toka, Hakan R; Toka, Okan; Hariri, Ali; Nguyen, Hiep T
2010-07-01
Congenital anomalies of the kidney and urinary tract anatomy (CAKUT) are common in children and represent approximately 30% of all prenatally diagnosed malformations. CAKUT is phenotypically variable and can affect the kidney(s) alone and/or the lower urinary tract. The spectrum includes more common anomalies such as vesicoureteral reflux and, rarely, more severe malformations such as bilateral renal agenesis. In young children, congenital anomalies are the leading cause of kidney failure and for kidney transplantation or dialysis. CAKUT can also lead to significant renal problems in adulthood and may present itself with hypertension and/or proteinuria. Congenital renal anomalies can be sporadic or familial, syndromic (also affecting nonrenal or non-urinary tract tissues), or nonsyndromic. Genetic causes have been identified for the syndromic forms and have shed some light into the molecular mechanisms of kidney development in human beings. The genetic causes for the more common nonsyndromic forms of CAKUT are unknown. The role of prenatal interventions and postnatal therapies as well as the benefits of screening affected individuals and their family members are not clear.
Anomaly detection: eye movement patterns.
Ni, W; Fodor, J D; Crain, S; Shankweiler, D
1998-09-01
The symptom of a garden path in sentence processing is an important anomaly in the input string. This anomaly signals to the parser that an error has occurred, and provides cues for how to repair it. Anomaly detection is thus an important aspect of sentence processing. In the present study, we investigated how the parser responds to unambiguous sentences that contain syntactic anomalies and pragmatic anomalies, examining records of eye movement during reading. While sensitivity to the two kinds of anomaly was very rapid and essentially simultaneous, qualitative differences existed in the patterns of first-pass reading times and eye regressions. The results are compatible with the proposal that syntactic information and pragmatic information are used differently in garden-path recovery.
ERIC Educational Resources Information Center
Quimby, Donald J.
1984-01-01
Discusses the geometry, algebra, and logic involved in the solution of a "Mindbenders" problem in "Discover" magazine and applies it to calculations of satellite orbital velocity. Extends the solution of this probe to other applications of falling objects. (JM)
ERIC Educational Resources Information Center
Quimby, Donald J.
1984-01-01
Discusses the geometry, algebra, and logic involved in the solution of a "Mindbenders" problem in "Discover" magazine and applies it to calculations of satellite orbital velocity. Extends the solution of this probe to other applications of falling objects. (JM)
Anomaly Detection at Multiple Scales
2011-11-07
Arlington, VA November 7, 2011 Anomaly Detection at Multiple Scales Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden...AND SUBTITLE Anomaly Detection at Multiple Scales 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER...Personal temperament and mental health • Distress, instability, or other vulnerability Anomaly Detection at Multiple Scales (ADAMS) Detect
Multicriteria Similarity-Based Anomaly Detection Using Pareto Depth Analysis.
Hsiao, Ko-Jen; Xu, Kevin S; Calder, Jeff; Hero, Alfred O
2016-06-01
We consider the problem of identifying patterns in a data set that exhibits anomalous behavior, often referred to as anomaly detection. Similarity-based anomaly detection algorithms detect abnormally large amounts of similarity or dissimilarity, e.g., as measured by the nearest neighbor Euclidean distances between a test sample and the training samples. In many application domains, there may not exist a single dissimilarity measure that captures all possible anomalous patterns. In such cases, multiple dissimilarity measures can be defined, including nonmetric measures, and one can test for anomalies by scalarizing using a nonnegative linear combination of them. If the relative importance of the different dissimilarity measures are not known in advance, as in many anomaly detection applications, the anomaly detection algorithm may need to be executed multiple times with different choices of weights in the linear combination. In this paper, we propose a method for similarity-based anomaly detection using a novel multicriteria dissimilarity measure, the Pareto depth. The proposed Pareto depth analysis (PDA) anomaly detection algorithm uses the concept of Pareto optimality to detect anomalies under multiple criteria without having to run an algorithm multiple times with different choices of weights. The proposed PDA approach is provably better than using linear combinations of the criteria, and shows superior performance on experiments with synthetic and real data sets.
OSO-6 Orbiting Solar Observatory
NASA Technical Reports Server (NTRS)
1972-01-01
The description, development history, test history, and orbital performance analysis of the OSO-6 Orbiting Solar Observatory are presented. The OSO-6 Orbiting Solar Observatory was the sixth flight model of a series of scientific spacecraft designed to provide a stable platform for experiments engaged in the collection of solar and celestial radiation data. The design objective was 180 days of orbital operation. The OSO-6 has telemetered an enormous amount of very useful experiment and housekeeping data to GSFC ground stations. Observatory operation during the two-year reporting period was very successful except for some experiment instrument problems.
The development of the Poincare-similar elements with true anomaly as the independent variable
NASA Technical Reports Server (NTRS)
Mueller, A.
1976-01-01
In reference 1, the Hamiltonian of the unperturbed two-body problem in extended phase space is established. Depending on the type of time transformation, eight canonical elements were developed with the true anomaly or the eccentric anomaly as the independent variable. These two new sets, DS(phi) and DS(u), however contain singularities for small eccentricities and inclinations. In reference 2, these singularities are removed by a transformation from DS(u) to eight canonical PS(u) elements. In reference 3, the DS(phi) variables are transformed to the PS(phi) elements to remove the singularities. However, no direct relation was established between the eight canonical PS(phi) elements and the Cartesian coordinates. It is the purpose of this report to establish those relations and to develop the perturbed equations of motion in the PS(phi) space. This report also demonstrates the accuracy of this new set when it is applied to numerical orbit prediction problems.
Periodic orbits for three and four co-orbital bodies
NASA Astrophysics Data System (ADS)
Verrier, P. E.; McInnes, C. R.
2014-08-01
We investigate the natural families of periodic orbits associated with the equilibrium configurations of the planar-restricted 1 + n-body problem for the case 2 ≤ n ≤ 4 equal-mass satellites. Such periodic orbits can be used to model both trojan exoplanetary systems and parking orbits for captured asteroids within the Solar system. For n = 2, there are two families of periodic orbits associated with the equilibria of the system: the well-known horseshoe and tadpole orbits. For n = 3, there are three families that emanate from the equilibrium configurations of the satellites, while for n = 4, there are six such families as well as numerous additional connecting families. The families of periodic orbits are all of the horseshoe or tadpole type, and several have regions of neutral linear stability.
Discovering System Health Anomalies Using Data Mining Techniques
NASA Technical Reports Server (NTRS)
Sriastava, Ashok, N.
2005-01-01
We present a data mining framework for the analysis and discovery of anomalies in high-dimensional time series of sensor measurements that would be found in an Integrated System Health Monitoring system. We specifically treat the problem of discovering anomalous features in the time series that may be indicative of a system anomaly, or in the case of a manned system, an anomaly due to the human. Identification of these anomalies is crucial to building stable, reusable, and cost-efficient systems. The framework consists of an analysis platform and new algorithms that can scale to thousands of sensor streams to discovers temporal anomalies. We discuss the mathematical framework that underlies the system and also describe in detail how this framework is general enough to encompass both discrete and continuous sensor measurements. We also describe a new set of data mining algorithms based on kernel methods and hidden Markov models that allow for the rapid assimilation, analysis, and discovery of system anomalies. We then describe the performance of the system on a real-world problem in the aircraft domain where we analyze the cockpit data from aircraft as well as data from the aircraft propulsion, control, and guidance systems. These data are discrete and continuous sensor measurements and are dealt with seamlessly in order to discover anomalous flights. We conclude with recommendations that describe the tradeoffs in building an integrated scalable platform for robust anomaly detection in ISHM applications.
Conditional anomaly detection methods for patient–management alert systems
Valko, Michal; Cooper, Gregory; Seybert, Amy; Visweswaran, Shyam; Saul, Melissa; Hauskrecht, Milos
2010-01-01
Anomaly detection methods can be very useful in identifying unusual or interesting patterns in data. A recently proposed conditional anomaly detection framework extends anomaly detection to the problem of identifying anomalous patterns on a subset of attributes in the data. The anomaly always depends (is conditioned) on the value of remaining attributes. The work presented in this paper focuses on instance–based methods for detecting conditional anomalies. The methods rely on the distance metric to identify examples in the dataset that are most critical for detecting the anomaly. We investigate various metrics and metric learning methods to optimize the performance of the instance–based anomaly detection methods. We show the benefits of the instance–based methods on two real–world detection problems: detection of unusual admission decisions for patients with the community–acquired pneumonia and detection of unusual orders of an HPF4 test that is used to confirm Heparin induced thrombocytopenia — a life–threatening condition caused by the Heparin therapy. PMID:25392850
Conditional anomaly detection methods for patient-management alert systems.
Valko, Michal; Cooper, Gregory; Seybert, Amy; Visweswaran, Shyam; Saul, Melissa; Hauskrecht, Milos
2008-07-01
Anomaly detection methods can be very useful in identifying unusual or interesting patterns in data. A recently proposed conditional anomaly detection framework extends anomaly detection to the problem of identifying anomalous patterns on a subset of attributes in the data. The anomaly always depends (is conditioned) on the value of remaining attributes. The work presented in this paper focuses on instance-based methods for detecting conditional anomalies. The methods rely on the distance metric to identify examples in the dataset that are most critical for detecting the anomaly. We investigate various metrics and metric learning methods to optimize the performance of the instance-based anomaly detection methods. We show the benefits of the instance-based methods on two real-world detection problems: detection of unusual admission decisions for patients with the community-acquired pneumonia and detection of unusual orders of an HPF4 test that is used to confirm Heparin induced thrombocytopenia - a life-threatening condition caused by the Heparin therapy.
On-Orbit Performance and Calibration of the Soft X-Ray Telescope on Yohkoh.
Acton, Loren W
This paper documents details of the on-orbit performance, data problem solving, and calibration of the Soft X-ray Telescope (SXT) experiment on Yohkoh. This information is important to a full understanding of the strengths and weaknesses of the SXT data set. The paper begins with summaries of SXT calibration issues and how they have been addressed, operational anomalies experienced during the mission, and a brief discussion of the SXT optical train. The following section on the accuracy of Yohkoh pointing determination provides information important for alignment of SXT images with each other and with other solar data. The remainder of the paper gives details of work by the experiment team to understand and ameliorate the many instrument anomalies and changes which impacted the scientific data.
On-Orbit Performance and Calibration of the Soft X-Ray Telescope on Yohkoh
NASA Astrophysics Data System (ADS)
Acton, Loren W.
2016-02-01
This paper documents details of the on-orbit performance, data problem solving, and calibration of the Soft X-ray Telescope (SXT) experiment on Yohkoh. This information is important to a full understanding of the strengths and weaknesses of the SXT data set. The paper begins with summaries of SXT calibration issues and how they have been addressed, operational anomalies experienced during the mission, and a brief discussion of the SXT optical train. The following section on the accuracy of Yohkoh pointing determination provides information important for alignment of SXT images with each other and with other solar data. The remainder of the paper gives details of work by the experiment team to understand and ameliorate the many instrument anomalies and changes which impacted the scientific data.
Coordinated orbit transfer for satellite clusters.
Zhang, Fumin; Krishnaprasad, P S
2004-05-01
We propose a control law that allows a satellite formation to achieve orbit transfer. During the transfer, the formation can be either maintained or modified to a desired formation. Based on the orbit transfer control law proposed by Chang, Chichka, and Marsden for single satellite, we add coupling terms to the summation of Lyapunov functions for single satellites. These terms are functions of the difference between the mean anomalies (or perigee passage times) of formation members. The asymptotic stability of the desired formation in desired orbits is proved.
Anomalies and entanglement renormalization
NASA Astrophysics Data System (ADS)
Bridgeman, Jacob C.; Williamson, Dominic J.
2017-09-01
We study 't Hooft anomalies of discrete groups in the framework of (1+1)-dimensional multiscale entanglement renormalization ansatz states on the lattice. Using matrix product operators, general topological restrictions on conformal data are derived. An ansatz class allowing for optimization of MERA with an anomalous symmetry is introduced. We utilize this class to numerically study a family of Hamiltonians with a symmetric critical line. Conformal data is obtained for all irreducible projective representations of each anomalous symmetry twist, corresponding to definite topological sectors. It is numerically demonstrated that this line is a protected gapless phase. Finally, we implement a duality transformation between a pair of critical lines using our subclass of MERA.
Genetics of lymphatic anomalies
Brouillard, Pascal; Boon, Laurence; Vikkula, Miikka
2014-01-01
Lymphatic anomalies include a variety of developmental and/or functional defects affecting the lymphatic vessels: sporadic and familial forms of primary lymphedema, secondary lymphedema, chylothorax and chylous ascites, lymphatic malformations, and overgrowth syndromes with a lymphatic component. Germline mutations have been identified in at least 20 genes that encode proteins acting around VEGFR-3 signaling but also downstream of other tyrosine kinase receptors. These mutations exert their effects via the RAS/MAPK and the PI3K/AKT pathways and explain more than a quarter of the incidence of primary lymphedema, mostly of inherited forms. More common forms may also result from multigenic effects or post-zygotic mutations. Most of the corresponding murine knockouts are homozygous lethal, while heterozygotes are healthy, which suggests differences in human and murine physiology and the influence of other factors. PMID:24590274
[Developmental venous anomaly (DVA)].
Zimmer, A; Hagen, T; Ahlhelm, F; Viera, J; Reith, W; Schulte-Altedorneburg, G
2007-10-01
As congenital anatomic variants of venous drainage, developmental venous anomalies (DVA) represent up to 60% of all cerebral vascular malformations. The prior term "venous angioma" is a misnomer implicating an abnormal vascular structure with an increased bleeding risk. They are often found incidentally and are hardly ever symptomatic. Their morphologic characteristics are dilated vessels in the white matter, which converge on a greater collector vein, forming the typical caput medusae. They drain into the superficial or deep venous system. The frequent association with other, potentially bleeding-prone vascular malformations is clinically relevant, in particular cavernous angioma, which might require therapeutic action. Therefore, coincident vascular lesions need to be actively sought by appropriate additional imaging techniques.
Pieper, S.C.; Wiringa, R.B.
1995-08-01
The Argonne v{sub 18} potential contains a detailed treatment of the pp, pn and nn electromagnetic potential, including Coulomb, vacuum polarization, Darwin Foldy and magnetic moment terms, all with suitable form factors and was fit to pp and pn data using the appropriate nuclear masses. In addition, it contains a nuclear charge-symmetry breaking (CSB) term adjusted to reproduce the difference in the experimental pp and nn scattering lengths. We have used these potential terms to compute differences in the binding energies of mirror isospin-1/2 nuclei (Nolen-Schiffer [NS] anomaly). Variational Monte Carlo calculations for the {sup 3}He-{sup 3}H system and cluster variational Monte Carlo for the {sup 15}O-{sup 15}N and {sup 17}F-{sup 17}O systems were made. In the first case, the best variational wave function for the A = 3 nuclei was used. However, because our {sup 16}O wave function does not reproduce accurately the {sup 16}O rms radius, to which the NS anomaly is very sensitive, we adjusted the A = 15 and A = 17 wave functions to reproduce the experimental density profiles. Our computed energy differences for these three systems are 0.757 {plus_minus} .001, 3.544 {plus_minus} .018 and 3.458 {plus_minus} .040 MeV respectively, which are to be compared with the experimental differences of 0.764, 3.537, and 3.544 MeV. Most of the theoretical uncertainties are due to uncertainties in the experimental rms radii. The nuclear CSB potential contributes 0.066, 0.188, and 0.090 MeV to these totals. We also attempted calculations for A = 39 and A = 41. However, in these cases, the experimental uncertainties in the rms radius make it impossible to extract useful information about the contribution of the nuclear CSB potential.
Anomaly Detection in Dynamic Networks
Turcotte, Melissa
2014-10-14
Anomaly detection in dynamic communication networks has many important security applications. These networks can be extremely large and so detecting any changes in their structure can be computationally challenging; hence, computationally fast, parallelisable methods for monitoring the network are paramount. For this reason the methods presented here use independent node and edge based models to detect locally anomalous substructures within communication networks. As a first stage, the aim is to detect changes in the data streams arising from node or edge communications. Throughout the thesis simple, conjugate Bayesian models for counting processes are used to model these data streams. A second stage of analysis can then be performed on a much reduced subset of the network comprising nodes and edges which have been identified as potentially anomalous in the first stage. The first method assumes communications in a network arise from an inhomogeneous Poisson process with piecewise constant intensity. Anomaly detection is then treated as a changepoint problem on the intensities. The changepoint model is extended to incorporate seasonal behavior inherent in communication networks. This seasonal behavior is also viewed as a changepoint problem acting on a piecewise constant Poisson process. In a static time frame, inference is made on this extended model via a Gibbs sampling strategy. In a sequential time frame, where the data arrive as a stream, a novel, fast Sequential Monte Carlo (SMC) algorithm is introduced to sample from the sequence of posterior distributions of the change points over time. A second method is considered for monitoring communications in a large scale computer network. The usage patterns in these types of networks are very bursty in nature and don’t fit a Poisson process model. For tractable inference, discrete time models are considered, where the data are aggregated into discrete time periods and probability models are fitted to the
Panopoulos, G. A.; Simos, T. E.; Anastassi, Z. A.
2013-03-15
A new multistep predictor-corrector (PC) pair form is introduced for the numerical integration of second-order initial-value problems. Using this form, a new eight-step symmetric embedded predictor-corrector method is constructed. The new PC method is based on the multistep symmetric method of Quinlan and Tremaine, with eight steps and eighth algebraic order, and is constructed to solve numerically the N-body problem. The new integrator has algebraic order 10 and it can be used to solve problems, for which the frequency is not known. We investigate the behavior of the new algorithm by integrating the five outer-planet problem and the two-body problem with various eccentricities. Regarding the five outer-planet problem, we calculate the error of the integrator in the solution, the Hamiltonian, and the phase after forward and backward integration over various intervals that are multiples of the period of Jupiter.
Relic vector field and CMB large scale anomalies
Chen, Xingang; Wang, Yi E-mail: yw366@cam.ac.uk
2014-10-01
We study the most general effects of relic vector fields on the inflationary background and density perturbations. Such effects are observable if the number of inflationary e-folds is close to the minimum requirement to solve the horizon problem. We show that this can potentially explain two CMB large scale anomalies: the quadrupole-octopole alignment and the quadrupole power suppression. We discuss its effect on the parity anomaly. We also provide analytical template for more detailed data comparison.
Flavorful hybrid anomaly-gravity mediation
Gross, Christian; Hiller, Gudrun
2011-05-01
We consider supersymmetric models where anomaly and gravity mediation give comparable contributions to the soft terms and discuss how this can be realized in a five-dimensional brane world. The gaugino mass pattern of anomaly mediation is preserved in such a hybrid setup. The flavorful gravity-mediated contribution cures the tachyonic slepton problem of anomaly mediation. The supersymmetric flavor puzzle is solved by alignment. We explicitly show how a working flavor-tachyon link can be realized with Abelian flavor symmetries and give the characteristic signatures of the framework, including O(1) slepton mass splittings between different generations and between doublets and singlets. This provides opportunities for same flavor dilepton edge measurements with missing energy at the Large Hadron Collider (LHC). Rare lepton decay rates could be close to their current experimental limit. Compared to pure gravity mediation, the hybrid model is advantageous because it features a heavy gravitino which can avoid the cosmological gravitino problem of gravity-mediated models combined with leptogenesis.
Shapira, D.
1988-01-01
Nuclear orbiting following collisions between sd and p shell nuclei is discussed. The dependence of this process on the real and imaginary parts of the nucleus-nucleus potential is discussed, as well as the evolution of the dinucleus toward a fully equilibrated fused system. 26 refs., 15 figs.
Worldwide correlation between earthquakes and electromagnetic anomalies from satellites
NASA Astrophysics Data System (ADS)
Taroni, Matteo; De Santis, Angelo; Marchetti, Dedalo; Cianchini, Gianfranco; Parrot, Michel; Li, Mei
2017-04-01
A possible coupling between ionosphere and lithosphere has been intensely investigated in the last years. In particular, some studies attempt to use the information about electromagnetic anomalies measured from satellite to increase the performance of the earthquake forecasting models. Some of these studies are focused on the precursors of few big earthquakes, while other studies try to investigate the problem in a global prospective: in both cases it seems to be a lack of proper statistical testing of the hypothesis of correlation between earthquakes and electromagnetic anomalies. This study approaches the problem putting the hypothesis of correlation in a testable manner. We analyze the correlation between earthquakes and electromagnetic (i.e. magnetic and electron density) anomalies from DEMETER and SWARM satellites by counting the number of anomalies that fall inside the Dobrovolsky area (and its fractions) before and/or after the occurrence of M5.5+ earthquakes in the global CMT catalogue. We do not perform any preselection of earthquakes, and we carefully avoid the problem of double counting of anomalies (e.g. working with a declustered catalogue). Our final result is that there is a clear statistically significant correlation between earthquakes and electromagnetic anomalies detected from space.
Seismic data fusion anomaly detection
NASA Astrophysics Data System (ADS)
Harrity, Kyle; Blasch, Erik; Alford, Mark; Ezekiel, Soundararajan; Ferris, David
2014-06-01
Detecting anomalies in non-stationary signals has valuable applications in many fields including medicine and meteorology. These include uses such as identifying possible heart conditions from an Electrocardiography (ECG) signals or predicting earthquakes via seismographic data. Over the many choices of anomaly detection algorithms, it is important to compare possible methods. In this paper, we examine and compare two approaches to anomaly detection and see how data fusion methods may improve performance. The first approach involves using an artificial neural network (ANN) to detect anomalies in a wavelet de-noised signal. The other method uses a perspective neural network (PNN) to analyze an arbitrary number of "perspectives" or transformations of the observed signal for anomalies. Possible perspectives may include wavelet de-noising, Fourier transform, peak-filtering, etc.. In order to evaluate these techniques via signal fusion metrics, we must apply signal preprocessing techniques such as de-noising methods to the original signal and then use a neural network to find anomalies in the generated signal. From this secondary result it is possible to use data fusion techniques that can be evaluated via existing data fusion metrics for single and multiple perspectives. The result will show which anomaly detection method, according to the metrics, is better suited overall for anomaly detection applications. The method used in this study could be applied to compare other signal processing algorithms.
Equatorial thermosphere anomaly: Observations and simulations
NASA Astrophysics Data System (ADS)
Lei, J.; Thayer, J. P.; Wang, W.; Richmond, A. D.
2011-12-01
Several mechanisms including heat transport due to zonal winds, chemical heating and field-aligned ion drag have been proposed to explain the formation of the Equatorial Thermosphere Anomaly (ETA), but the real cause of the ETA formation in thermosphere temperature is still a mystery. Various observations of the ionosphere and thermosphere have been used to investigate the variations of equatorial anomalies in both the ETA and EIA, and their interactions. The similarities and differences between the ETA and the EIA can provide important insight to the physical connections of this ion-neutral coupling problem. Meanwhile, the combination of observations and theoretical models allows us to understand the fundamental physical and chemical ion-neutral processes in the equatorial F region. This talk will highlight the recent progress of the formation of the ETA associated with the ion-neutral coupling in the equatorial region.
Congenital anomalies of the optic nerve
Amador-Patarroyo, Manuel J.; Pérez-Rueda, Mario A.; Tellez, Carlos H.
2014-01-01
Congenital optic nerve head anomalies are a group of structural malformations of the optic nerve head and surrounding tissues, which may cause congenital visual impairment and blindness. Each entity in this group of optic nerve anomalies has individually become more prevalent as our ability to differentiate between them has improved due to better characterization of cases. Access to better medical technology (e.g., neuroimaging and genetic analysis advances in recent years) has helped to expand our knowledge of these abnormalities. However, visual impairment may not be the only problem in these patients, some of these entities will be related to ophthalmologic, neurologic and systemic features that will help the physician to identify and predict possible outcomes in these patients, which sometimes may be life-threatening. Herein we present helpful hints, associations and management (when plausible) for them. PMID:25859137
Conditional Anomaly Detection with Soft Harmonic Functions.
Valko, Michal; Kveton, Branislav; Valizadegan, Hamed; Cooper, Gregory F; Hauskrecht, Milos
2011-01-01
In this paper, we consider the problem of conditional anomaly detection that aims to identify data instances with an unusual response or a class label. We develop a new non-parametric approach for conditional anomaly detection based on the soft harmonic solution, with which we estimate the confidence of the label to detect anomalous mislabeling. We further regularize the solution to avoid the detection of isolated examples and examples on the boundary of the distribution support. We demonstrate the efficacy of the proposed method on several synthetic and UCI ML datasets in detecting unusual labels when compared to several baseline approaches. We also evaluate the performance of our method on a real-world electronic health record dataset where we seek to identify unusual patient-management decisions.
Spectral anomaly detection in deep shadows.
Kanaev, Andrey V; Murray-Krezan, Jeremy
2010-03-20
Although several hyperspectral anomaly detection algorithms have proven useful when illumination conditions provide for enough light, many of these same detection algorithms fail to perform well when shadows are also present. To date, no general approach to the problem has been demonstrated. In this paper, a novel hyperspectral anomaly detection algorithm that adapts the dimensionality of the spectral detection subspace to multiple illumination levels is described. The novel detection algorithm is applied to reflectance domain hyperspectral data that represents a variety of illumination conditions: well illuminated and poorly illuminated (i.e., shadowed). Detection results obtained for objects located in deep shadows and light-shadow transition areas suggest superiority of the novel algorithm over standard subspace RX detection.
Conditional Anomaly Detection with Soft Harmonic Functions
Valko, Michal; Kveton, Branislav; Valizadegan, Hamed; Cooper, Gregory F.; Hauskrecht, Milos
2012-01-01
In this paper, we consider the problem of conditional anomaly detection that aims to identify data instances with an unusual response or a class label. We develop a new non-parametric approach for conditional anomaly detection based on the soft harmonic solution, with which we estimate the confidence of the label to detect anomalous mislabeling. We further regularize the solution to avoid the detection of isolated examples and examples on the boundary of the distribution support. We demonstrate the efficacy of the proposed method on several synthetic and UCI ML datasets in detecting unusual labels when compared to several baseline approaches. We also evaluate the performance of our method on a real-world electronic health record dataset where we seek to identify unusual patient-management decisions. PMID:25309142
Anomaly detection in clinical processes.
Huang, Zhengxing; Lu, Xudong; Duan, Huilong
2012-01-01
Meaningful anomalies in clinical processes may be related to caring performance or even the patient survival. It is imperative that the anomalies be timely detected such that useful and actionable knowledge of interest could be extracted to clinicians. Many previous approaches assume prior knowledge about the structure of clinical processes, using which anomalies are detected in a supervised manner. For a majority of clinical settings, however, clinical processes are complex, ad hoc, and even unknown a prior. In this paper, we investigate how to facilitate detection of anomalies in an unsupervised manner. An anomaly detection model is presented by applying a density-based clustering method on patient careflow logs. Using the learned model, it is possible to detect whether a particular patient careflow trace is anomalous with respect to normal traces in the logs. The approach has been validated over real data sets collected from a Chinese hospital.
System for closure of a physical anomaly
Bearinger, Jane P; Maitland, Duncan J; Schumann, Daniel L; Wilson, Thomas S
2014-11-11
Systems for closure of a physical anomaly. Closure is accomplished by a closure body with an exterior surface. The exterior surface contacts the opening of the anomaly and closes the anomaly. The closure body has a primary shape for closing the anomaly and a secondary shape for being positioned in the physical anomaly. The closure body preferably comprises a shape memory polymer.
Seasat orbit refinement for altimetry application
NASA Astrophysics Data System (ADS)
Mohan, S. N.; Hamata, N. E.; Stavert, R. L.; Bierman, G. J.
1980-12-01
This paper describes the use of stochastic differential correction models in refining the Seasat orbit based on post-flight analysis of tracking data. The objective is to obtain orbital-height precision that is commensurate with the inherent Seasat altimetry data precision level of 10 cms. Local corrections to a mean ballistic arc, perturbed principally by atmospheric drag variations and local gravitational anomalies, are obtained by the introduction of stochastic dynamical models in conjunction with optimal estimation/smoothing techniques. Assessment of the resulting orbit with 'ground truth' provided by Seasat altimetry data shows that the orbital height precision is improved by 32% when compared to a conventional least-squares solution using the same data set. The orbital height precision realized by employing stochastic differential correction models is in the range of 73 cms to 208 cms rms.
Mars Geoscience Orbiter and Lunar Geoscience Orbiter
NASA Technical Reports Server (NTRS)
Fuldner, W. V.; Kaskiewicz, P. F.
1983-01-01
The feasibility of using the AE/DE Earth orbiting spacecraft design for the LGO and/or MGO missions was determined. Configurations were developed and subsystems analysis was carried out to optimize the suitability of the spacecraft to the missions. The primary conclusion is that the basic AE/DE spacecraft can readily be applied to the LGO mission with relatively minor, low risk modifications. The MGO mission poses a somewhat more complex problem, primarily due to the overall maneuvering hydrazine budget and power requirements of the sensors and their desired duty cycle. These considerations dictate a modification (scaling up) of the structure to support mission requirements.
Viable Supersymmetry and Leptogenesis with Anomaly Mediation
Ibe, Masahiro; Kitano, Ryuichiro; Murayama, Hitoshi; Yanagida, Tsutomu
2005-01-13
The seesaw mechanism that explains the small neutrino masses comes naturally with supersymmetric (SUSY) grand unification and leptogenesis. However, the framework suffers from the SUSY flavor and CP problems, and has a severe cosmological gravitino problem. We propose anomaly mediation as a simple solution to all these problems, which is viable once supplemented by the D-terms for U(1)_Y and U(1)_B-L. Even though the right-handed neutrino mass explicitly breaks U(1)_B-L and hence reintroduces the flavor problem, we show that it lacks the logarithmic enhancement and poses no threat to the framework. The thermal leptogenesis is then made easily consistent with the gravitino constraint.
Reliability of CHAMP Anomaly Continuations
NASA Technical Reports Server (NTRS)
vonFrese, Ralph R. B.; Kim, Hyung Rae; Taylor, Patrick T.; Asgharzadeh, Mohammad F.
2003-01-01
CHAMP is recording state-of-the-art magnetic and gravity field observations at altitudes ranging over roughly 300 - 550 km. However, anomaly continuation is severely limited by the non-uniqueness of the process and satellite anomaly errors. Indeed, our numerical anomaly simulations from satellite to airborne altitudes show that effective downward continuations of the CHAMP data are restricted to within approximately 50 km of the observation altitudes while upward continuations can be effective over a somewhat larger altitude range. The great unreliability of downward continuation requires that the satellite geopotential observations must be analyzed at satellite altitudes if the anomaly details are to be exploited most fully. Given current anomaly error levels, joint inversion of satellite and near- surface anomalies is the best approach for implementing satellite geopotential observations for subsurface studies. We demonstrate the power of this approach using a crustal model constrained by joint inversions of near-surface and satellite magnetic and gravity observations for Maude Rise, Antarctica, in the southwestern Indian Ocean. Our modeling suggests that the dominant satellite altitude magnetic anomalies are produced by crustal thickness variations and remanent magnetization of the normal polarity Cretaceous Quiet Zone.
Abundance anomalies in tidal disruption events
NASA Astrophysics Data System (ADS)
Kochanek, C. S.
2016-05-01
The ˜10 per cent of tidal disruption events (TDEs) due to stars more massive than M* ≳ M⊙ should show abundance anomalies due to stellar evolution in helium, carbon and nitrogen, but not oxygen. Helium is always enhanced, but only by up to ˜25 per cent on average because it becomes inaccessible once it is sequestered in the high-density core as the star leaves the main sequence. However, portions of the debris associated with the disrupted core of a main-sequence star can be enhanced in helium by factors of 2-3 for debris at a common orbital period. These helium abundance variations may be a contributor to the observed diversity of hydrogen and helium line strengths in TDEs. A still more striking anomaly is the rapid enhancement of nitrogen and the depletion of carbon due to the CNO cycle - stars with M* ≳ M⊙ quickly show an increase in their average N/C ratio by factors of 3-10. Because low-mass stars evolve slowly and high-mass stars are rare, TDEs showing high N/C will almost all be due to ˜1-2 M⊙ stars disrupted on the main sequence. Like helium, portions of the debris will show still larger changes in C and N, and the anomalies decline as the star leaves the main sequence. The enhanced [N/C] abundance ratio of these TDEs provides the first natural explanation for the rare, nitrogen-rich quasars and may also explain the strong nitrogen emission seen in ultraviolet spectra of ASASSN-14li.
Domain Anomaly Detection in Machine Perception: A System Architecture and Taxonomy.
Kittler, Josef; Christmas, William; de Campos, Teófilo; Windridge, David; Yan, Fei; Illingworth, John; Osman, Magda
2014-05-01
We address the problem of anomaly detection in machine perception. The concept of domain anomaly is introduced as distinct from the conventional notion of anomaly used in the literature. We propose a unified framework for anomaly detection which exposes the multifaceted nature of anomalies and suggest effective mechanisms for identifying and distinguishing each facet as instruments for domain anomaly detection. The framework draws on the Bayesian probabilistic reasoning apparatus which clearly defines concepts such as outlier, noise, distribution drift, novelty detection (object, object primitive), rare events, and unexpected events. Based on these concepts we provide a taxonomy of domain anomaly events. One of the mechanisms helping to pinpoint the nature of anomaly is based on detecting incongruence between contextual and noncontextual sensor(y) data interpretation. The proposed methodology has wide applicability. It underpins in a unified way the anomaly detection applications found in the literature. To illustrate some of its distinguishing features, in here the domain anomaly detection methodology is applied to the problem of anomaly detection for a video annotation system.
Gravitational anomaly and transport phenomena.
Landsteiner, Karl; Megías, Eugenio; Pena-Benitez, Francisco
2011-07-08
Quantum anomalies give rise to new transport phenomena. In particular, a magnetic field can induce an anomalous current via the chiral magnetic effect and a vortex in the relativistic fluid can also induce a current via the chiral vortical effect. The related transport coefficients can be calculated via Kubo formulas. We evaluate the Kubo formula for the anomalous vortical conductivity at weak coupling and show that it receives contributions proportional to the gravitational anomaly coefficient. The gravitational anomaly gives rise to an anomalous vortical effect even for an uncharged fluid.
Anomalies and graded coisotropic branes
NASA Astrophysics Data System (ADS)
Li, Yi
2006-03-01
We compute the anomaly of the axial U(1) current in the A-model on a Calabi-Yau manifold, in the presence of coisotropic branes discovered by Kapustin and Orlov. Our results relate the anomaly-free condition to a recently proposed definition of graded coisotropic branes in Calabi-Yau manifolds. More specifically, we find that a coisotropic brane is anomaly-free if and only if it is gradable. We also comment on a different grading for coisotropic submanifolds introduced recently by Oh.
Echography - eye orbit; Ultrasound - eye orbit; Ocular ultrasonography; Orbital ultrasonography ... ophthalmology department of a hospital or clinic. Your eye is numbed with medicine (anesthetic drops). The ultrasound ...
Online Learning and Sequential Anomaly Detection in Trajectories.
Laxhammar, Rikard; Falkman, Göran
2013-09-12
Detection of anomalous trajectories is an important problem in the surveillance domain. Various algorithms based on learning of normal trajectory patterns have been proposed for this problem. Yet, these algorithms typically suffer from one or more limitations: They are not designed for sequential analysis of incomplete trajectories or online learning based on an incrementally updated training set. Moreover, they typically involve tuning of many parameters, including ad-hoc anomaly thresholds, and may therefore suffer from overfitting and poorly-calibrated alarm rates. In this article, we propose and investigate the Sequential Hausdorff Nearest-Neighbour Conformal Anomaly Detector (SHNN-CAD) for online learning and sequential anomaly detection in trajectories. This is a parameter-light algorithm that offers a well-founded approach to the calibration of the anomaly threshold. The discords algorithm, originally proposed by Keogh et al, is another parameter-light anomaly detection algorithm that has previously been shown to have good classification performance on a wide range of time-series datasets, including trajectory data. We implement and investigate the performance of SHNN-CAD and the discords algorithm on four different labelled trajectory datasets. The results show that SHNN-CAD achieves competitive classification performance with minimum parameter tuning during unsupervised online learning and sequential anomaly detection in trajectories.
Online Learning and Sequential Anomaly Detection in Trajectories.
Laxhammar, Rikard; Falkman, Göran
2014-06-01
Detection of anomalous trajectories is an important problem in the surveillance domain. Various algorithms based on learning of normal trajectory patterns have been proposed for this problem. Yet, these algorithms typically suffer from one or more limitations: They are not designed for sequential analysis of incomplete trajectories or online learning based on an incrementally updated training set. Moreover, they typically involve tuning of many parameters, including ad-hoc anomaly thresholds, and may therefore suffer from overfitting and poorly-calibrated alarm rates. In this article, we propose and investigate the Sequential Hausdorff Nearest-Neighbor Conformal Anomaly Detector (SHNN-CAD) for online learning and sequential anomaly detection in trajectories. This is a parameter-light algorithm that offers a well-founded approach to the calibration of the anomaly threshold. The discords algorithm, originally proposed by Keogh et al. , is another parameter-light anomaly detection algorithm that has previously been shown to have good classification performance on a wide range of time-series datasets, including trajectory data. We implement and investigate the performance of SHNN-CAD and the discords algorithm on four different labeled trajectory datasets. The results show that SHNN-CAD achieves competitive classification performance with minimum parameter tuning during unsupervised online learning and sequential anomaly detection in trajectories.
NASA Astrophysics Data System (ADS)
Miao, H.; Yin, Z. P.; Wu, S. F.; Li, J. M.; Ma, J.; Lv, B.-Q.; Wang, X. P.; Qian, T.; Richard, P.; Xing, L.-Y.; Wang, X.-C.; Jin, C. Q.; Haule, K.; Kotliar, G.; Ding, H.
2016-11-01
In iron-based superconductors (FeSCs), orbital differentiation is an important phenomenon, whereby correlations stronger on the dx y orbital than on the dx z/dy z orbital yield quasiparticles with a dx y orbital character having larger mass renormalization and an abnormal temperature evolution. However, the physical origin of this orbital differentiation is debated between the Hund's coupling-induced unbinding of spin and orbital degrees of freedom and the Hubbard interaction instigated orbital-selective Mott transition. Here we use angle-resolved photoemission spectroscopy to identify an orbital-dependent correlation-induced quasiparticle (QP) anomaly in LiFeAs. The excellent agreement between our photoemission measurements and first-principles many-body theory calculations shows that the orbital-differentiated QP lifetime anomalies in LiFeAs are controlled by the Hund's coupling.
Miao, H.; Yin, Z. P.; Wu, S. F.; Li, J. M.; Ma, J.; Lv, B. -Q.; Wang, X. P.; Qian, T.; Richard, P.; Xing, L. -Y.; Wang, X. -C.; Jin, C. Q.; Haule, K.; Kotliar, G.; Ding, H.
2016-11-14
In the iron-based superconductors (FeSCs), orbital differentiation is an important phenomenon, whereby correlations stronger on the d_{xy} orbital than on the d_{xz}/d_{yz} orbital yield quasi-particles with d_{xy} orbital character having larger mass renormalization and abnormal temperature evolution. However, the physical origin of this orbital di erentiation is debated between the Hund's coupling induced unbinding of spin and orbital degrees of freedom and the Hubbard interaction instigated orbital selective Mott transition. Here we use angle-resolved photoemission spectroscopy to identify an orbital-dependent correlation-induced quasi-particle (QP) anomaly in LiFeAs. Lastly, the excellent agreement between our photoemission measurements and first-principles many-body theory calculations shows that the orbital-differentiated QP lifetime anomalies in LiFeAs are controlled by the Hund's coupling.
Miao, H.; Yin, Z. P.; Wu, S. F.; ...
2016-11-14
In the iron-based superconductors (FeSCs), orbital differentiation is an important phenomenon, whereby correlations stronger on the dxy orbital than on the dxz/dyz orbital yield quasi-particles with dxy orbital character having larger mass renormalization and abnormal temperature evolution. However, the physical origin of this orbital di erentiation is debated between the Hund's coupling induced unbinding of spin and orbital degrees of freedom and the Hubbard interaction instigated orbital selective Mott transition. Here we use angle-resolved photoemission spectroscopy to identify an orbital-dependent correlation-induced quasi-particle (QP) anomaly in LiFeAs. Lastly, the excellent agreement between our photoemission measurements and first-principles many-body theory calculations showsmore » that the orbital-differentiated QP lifetime anomalies in LiFeAs are controlled by the Hund's coupling.« less
Detailed gravity anomalies from GEOS-3 satellite altimetry data
NASA Technical Reports Server (NTRS)
Gopalapillai, G. S.; Mourad, A. G.
1978-01-01
A technique for deriving mean gravity anomalies from dense altimetry data was developed. A combination of both deterministic and statistical techniques was used. The basic mathematical model was based on the Stokes' equation which describes the analytical relationship between mean gravity anomalies and geoid undulations at a point; this undulation is a linear function of the altimetry data at that point. The overdetermined problem resulting from the excessive altimetry data available was solved using Least-Squares principles. These principles enable the simultaneous estimation of the associated standard deviations reflecting the internal consistency based on the accuracy estimates provided for the altimetry data as well as for the terrestrial anomaly data. Several test computations were made of the anomalies and their accuracy estimates using GOES-3 data.
Load characterization and anomaly detection for voice over IP traffic.
Mandjes, Michel; Saniee, Iraj; Stolyar, Alexander L
2005-09-01
We consider the problem of traffic anomaly detection in IP networks. Traffic anomalies typically arise when there is focused overload or when a network element fails and it is desired to infer these purely from the measured traffic. We derive new general formulae for the variance of the cumulative traffic over a fixed time interval and show how the derived analytical expression simplifies for the case of voice over IP traffic, the focus of this paper. To detect load anomalies, we show it is sufficient to consider cumulative traffic over relatively long intervals such as 5 min. We also propose simple anomaly detection tests including detection of over/underload. This approach substantially extends the current practice in IP network management where only the first-order statistics and fixed thresholds are used to identify abnormal behavior. We conclude with the application of the scheme to field data from an operational network.
NASA Technical Reports Server (NTRS)
Welsh, David; Denham, Samuel; Allen, Christopher
2011-01-01
In many cases, an initial symptom of hardware malfunction is unusual or unexpected acoustic noise. Many industries such as automotive, heating and air conditioning, and petro-chemical processing use noise and vibration data along with rotating machinery analysis techniques to identify noise sources and correct hardware defects. The NASA/Johnson Space Center Acoustics Office monitors the acoustic environment of the International Space Station (ISS) through periodic sound level measurement surveys. Trending of the sound level measurement survey results can identify in-flight hardware anomalies. The crew of the ISS also serves as a "detection tool" in identifying unusual hardware noises; in these cases the spectral analysis of audio recordings made on orbit can be used to identify hardware defects that are related to rotating components such as fans, pumps, and compressors. In this paper, three examples of the use of sound level measurements and audio recordings for the diagnosis of in-flight hardware anomalies are discussed: identification of blocked inter-module ventilation (IMV) ducts, diagnosis of abnormal ISS Crew Quarters rack exhaust fan noise, and the identification and replacement of a defective flywheel assembly in the Treadmill with Vibration Isolation (TVIS) hardware. In each of these examples, crew time was saved by identifying the off nominal component or condition that existed and in directing in-flight maintenance activities to address and correct each of these problems.
1991-09-07
triangular points have been published by Danby [20 and then later by [21] Bennett . Both Danby and Bennett have numerically generated graphic depictions of the...3, November-December 1964, pages 567-578. 20, J.M.A. Danby , "Stability of the Triangular Points in Elliptic Restricted Problem of Three Bodies," The
1991-10-10
and then later by [221 Bennett Both Danby and Bennett have numerically generated graphic depictions of the linear stability region in the p-e plane...J.M.A. Danby , "Stability of the Triangular Points in Elliptic Restricted Problem of Three Bodies," The Astronomical Journal, Volume 69, Number 2, March
Genetics Home Reference: Peters anomaly
... the anterior segment is abnormal, leading to incomplete separation of the cornea from the iris or the ... anomaly type I is characterized by an incomplete separation of the cornea and iris and mild to ...
NASA Technical Reports Server (NTRS)
Regan, R. D.; Davis, W. M.; Cain, J. C.
1975-01-01
A subset of Pogo satellite magnetometer data has been formed that is suitable for analysis of crustal magnetic anomalies. Through the use of a thirteenth-order field model fit to these data, magnetic residuals have been calculated over the world to latitude limits of plus or minus 50 deg. These residuals, averaged over 1-degree latitude-longitude blocks, represent a detailed global magnetic anomaly map derived solely from satellite data. The occurrence of these anomalies on all individual satellite passes independent of local time and their decay as altitude increases imply a definite internal origin. Their wavelength structure and their correlation with known tectonic features further suggest that these anomalies are primarily of geologic origin and have their sources in the lithosphere.
Classifying sex biased congenital anomalies
Lubinsky, M.S.
1997-03-31
The reasons for sex biases in congenital anomalies that arise before structural or hormonal dimorphisms are established has long been unclear. A review of such disorders shows that patterning and tissue anomalies are female biased, and structural findings are more common in males. This suggests different gender dependent susceptibilities to developmental disturbances, with female vulnerabilities focused on early blastogenesis/determination, while males are more likely to involve later organogenesis/morphogenesis. A dual origin for some anomalies explains paradoxical reductions of sex biases with greater severity (i.e., multiple rather than single malformations), presumably as more severe events increase the involvement of an otherwise minor process with opposite biases to those of the primary mechanism. The cause for these sex differences is unknown, but early dimorphisms, such as differences in growth or presence of H-Y antigen, may be responsible. This model provides a useful rationale for understanding and classifying sex-biased congenital anomalies. 42 refs., 7 tabs.
Separation method of anomaly source: The time-lapse microgravity data
NASA Astrophysics Data System (ADS)
Supriyadi, Santoso, D.; Gunawan, W.; Sarkowi, Gunawan, D.
2017-07-01
The time-lapse microgravity anomaly survey was performed in the purpose of searching the subsurface targets to discover an anomaly caused by the survey target. To isolate the source of the anomaly, an existing filter was generally used. For this certain purpose, the filter must be constructed in a way it can receive less than the maximum results. One problem is the source of the unwanted anomaly still attached to the preliminary data. As it is known, the source of time-lapse microgravity anomaly caused by the subsidence and fluid dynamics is idencated by the increases and decreases in groundwater levels. Therefore, the survey should minimize one of these anomalies sources by adjusting the filter field conditions. In this study, the constructed filter is referred as the MBF (Model Based Filter), this filter was constructed with attention-dimensional parameter source of the anomaly.
Gogoshev, M.M.; Gogosheva, TS.N.; Kostadinov, I.N.; Markova, T.I.; Kisovski, S.
1985-01-01
The region of South Atlantic Geomagnetic Anomaly was investigated by the Intercosmos-Bulgaria-1300 satellite, launched on August 7, 1981. On the basis of data obtained from 15 orbits during increased geomagnetic activity in August 1981, a map of the Anomaly was elaborated. Two centers of activity were identified. By means of the EMO-5 electrophotometer on board the Intercosmos-Bulgaria-1300 satellite, the atmosphere glow in lines 5577 A, 6300 A and 4278 A was studied. 11 references.
NASA Astrophysics Data System (ADS)
Gogoshev, M. M.; Gogosheva, Ts. N.; Kostadinov, I. N.; Markova, T. I.; Kisovski, S.
The region of South Atlantic Geomagnetic Anomaly was investigated by the Intercosmos-Bulgaria-1300 satellite, launched on August 7, 1981. On the basis of data obtained from 15 orbits during increased geomagnetic activity in August 1981, a map of the Anomaly was elaborated. Two centers of activity were identified. By means of the EMO-5 electrophotometer on board the Intercosmos-Bulgaria-1300 satellite, the atmosphere glow in lines 5577 A, 6300 A and 4278 A was studied.
Anomaly detection on cup anemometers
NASA Astrophysics Data System (ADS)
Vega, Enrique; Pindado, Santiago; Martínez, Alejandro; Meseguer, Encarnación; García, Luis
2014-12-01
The performances of two rotor-damaged commercial anemometers (Vector Instruments A100 LK) were studied. The calibration results (i.e. the transfer function) were very linear, the aerodynamic behavior being more efficient than the one shown by both anemometers equipped with undamaged rotors. No detection of the anomaly (the rotors’ damage) was possible based on the calibration results. However, the Fourier analysis clearly revealed this anomaly.
Spinal anomalies in Pfeiffer syndrome.
Moore, M H; Lodge, M L; Clark, B E
1995-05-01
Review of the spinal radiographs of a consecutive series of 11 patients with Pfeiffer syndrome presenting to the Australian Craniofacial Unit was performed. The prevalence of cervical spine fusions was high, and the pattern of fusion complex. Isolated anomalies were evident at lower levels, including two cases of sacrococcygeal eversion. Spinal anomalies occur more frequently in the more severely involved cases of Pfeiffer syndrome emphasizing the generalized dysostotic nature of this condition.
Spacecraft Environmental Anomalies Expert System
1994-02-23
An expert system has been developed by The Aerospace Corporation, Space and Environment Technology Center for use in the diagnosis of satellite...anomalies caused by the space environment. The expert system is designed to determine the probable cause of an anomaly from the following candidates...in the satellite. The expert system is a rule-based system that uses the Texas Instrument’s Personal Consultant Plus expert - system shell. The expert
Situs anomalies on prenatal MRI.
Nemec, Stefan F; Brugger, Peter C; Nemec, Ursula; Bettelheim, Dieter; Kasprian, Gregor; Amann, Gabriele; Rimoin, David L; Graham, John M; Prayer, Daniela
2012-04-01
Situs anomalies refer to an abnormal organ arrangement, which may be associated with severe errors of development. Due regard being given to prenatal magnetic resonance imaging (MRI) as an adjunct to ultrasonography (US), this study sought to demonstrate the in utero visualization of situs anomalies on MRI, compared to US. This retrospective study included 12 fetuses with situs anomalies depicted on fetal MRI using prenatal US as a comparison modality. With an MRI standard protocol, the whole fetus was assessed for anomalies, with regard to the position and morphology of the following structures: heart; venous drainage and aorta; stomach and intestines; liver and gallbladder; and the presence and number of spleens. Situs inversus totalis was found in 3/12 fetuses; situs inversus with levocardia in 1/12 fetuses; situs inversus abdominis in 2/12 fetuses; situs ambiguous with polysplenia in 3/12 fetuses, and with asplenia in 2/12 fetuses; and isolated dextrocardia in 1/12 fetuses. Congenital heart defects (CHDs), vascular anomalies, and intestinal malrotations were the most frequent associated malformations. In 5/12 cases, the US and MRI diagnoses were concordant. Compared to US, in 7/12 cases, additional MRI findings specified the situs anomaly, but CHDs were only partially visualized in six cases. Our initial MRI results demonstrate the visualization of situs anomalies and associated malformations in utero, which may provide important information for perinatal management. Using a standard protocol, MRI may identify additional findings, compared to US, which confirm and specify the situs anomaly, but, with limited MRI visualization of fetal CHDs. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.
Michelotti, L.
1995-01-01
The past fifteen years have witnessed a remarkable development of methods for analyzing single particle orbit dynamics in accelerators. Unlike their more classic counterparts, which act upon differential equations, these methods proceed by manipulating Poincare maps directly. This attribute makes them well matched for studying accelerators whose physics is most naturally modelled in terms of maps, an observation that has been championed most vigorously by Forest. In the following sections the author sketchs a little background, explains some of the physics underlying these techniques, and discusses the best computing strategy for implementing them in conjunction with modeling accelerators.
Video behavior profiling for anomaly detection.
Xiang, Tao; Gong, Shaogang
2008-05-01
This paper aims to address the problem of modelling video behaviour captured in surveillancevideos for the applications of online normal behaviour recognition and anomaly detection. A novelframework is developed for automatic behaviour profiling and online anomaly sampling/detectionwithout any manual labelling of the training dataset. The framework consists of the followingkey components: (1) A compact and effective behaviour representation method is developed basedon discrete scene event detection. The similarity between behaviour patterns are measured basedon modelling each pattern using a Dynamic Bayesian Network (DBN). (2) Natural grouping ofbehaviour patterns is discovered through a novel spectral clustering algorithm with unsupervisedmodel selection and feature selection on the eigenvectors of a normalised affinity matrix. (3) Acomposite generative behaviour model is constructed which is capable of generalising from asmall training set to accommodate variations in unseen normal behaviour patterns. (4) A run-timeaccumulative anomaly measure is introduced to detect abnormal behaviour while normal behaviourpatterns are recognised when sufficient visual evidence has become available based on an onlineLikelihood Ratio Test (LRT) method. This ensures robust and reliable anomaly detection and normalbehaviour recognition at the shortest possible time. The effectiveness and robustness of our approachis demonstrated through experiments using noisy and sparse datasets collected from both indoorand outdoor surveillance scenarios. In particular, it is shown that a behaviour model trained usingan unlabelled dataset is superior to those trained using the same but labelled dataset in detectinganomaly from an unseen video. The experiments also suggest that our online LRT based behaviourrecognition approach is advantageous over the commonly used Maximum Likelihood (ML) methodin differentiating ambiguities among different behaviour classes observed online.
NASA Astrophysics Data System (ADS)
Rodriguez, Isabel J.; Schmidt, Erin; Weislogel, Mark M.; Pettit, Donald
2016-11-01
We present what we think are the first intentional electrostatic orbits in the near-weightless environment of a drop tower. Classical physics problems involving Coulombic forces in orbital mechanics have traditionally been confined to thought experiments due to practical terrestrial experimental limitations, namely, the preponderance of gravity. However, the use of a drop tower as an experimental platform can overcome this challenge for brief periods. We demonstrate methanol-water droplets in orbit around a variety of charged objects- some of which can be used to validate special cases of N-body systems. Footage collected via a high-speed camera is analyzed and orbital trajectories are compared with existing theoretical predictions. Droplets of diameters 0.5 to 2mm in a variety of obits are observed. Due to the repeatability of drop tower initial conditions and effective low-g environment, such experiments may be used to construct empirical analogues and confirm analyses toward the benefit of other fields including space and planetary science. NASA Cooperative Agreement NNX12A047A, Portland State LSAMP, Robert E. McNair Scholars Program.
Torque anomaly in quantum field theory
NASA Astrophysics Data System (ADS)
Fulling, S. A.; Mera, F. D.; Trendafilova, C. S.
2013-02-01
The expectation values of energy density and pressure of a quantum field inside a wedge-shaped region appear to violate the expected relationship between torque and total energy as a function of angle. In particular, this is true of the well-known Deutsch-Candelas stress tensor for the electromagnetic field, whose definition requires no regularization except possibly at the vertex. Unlike a similar anomaly in the pressure exerted by a reflecting boundary against a perpendicular wall, this problem cannot be dismissed as an artifact of an ad hoc regularization.
The Apollo 15 deployable boom anomaly
NASA Technical Reports Server (NTRS)
White, R. D.
1972-01-01
During the Apollo 15 mission, a boom with an attached mass spectrometer was required to retract periodically so that the instrument would not be in the field of view of other experiments. The boom did not fully retract on five of 12 occasions. Data analysis indicated that the boom probably retracted to within approximately 2.54 centimeters (1 inch) of full retraction. The pertinent boom-design details, the events in the mission related to the anomaly, a discussion of the inflight and postflight investigation of the problem, a discussion of the design changes to the boom mechanism as a result of the investigation, and subsequent flight performance are presented.
Aeromagnetic anomalies over faulted strata
Grauch, V.J.S.; Hudson, Mark R.
2011-01-01
High-resolution aeromagnetic surveys are now an industry standard and they commonly detect anomalies that are attributed to faults within sedimentary basins. However, detailed studies identifying geologic sources of magnetic anomalies in sedimentary environments are rare in the literature. Opportunities to study these sources have come from well-exposed sedimentary basins of the Rio Grande rift in New Mexico and Colorado. High-resolution aeromagnetic data from these areas reveal numerous, curvilinear, low-amplitude (2–15 nT at 100-m terrain clearance) anomalies that consistently correspond to intrasedimentary normal faults (Figure 1). Detailed geophysical and rock-property studies provide evidence for the magnetic sources at several exposures of these faults in the central Rio Grande rift (summarized in Grauch and Hudson, 2007, and Hudson et al., 2008). A key result is that the aeromagnetic anomalies arise from the juxtaposition of magnetically differing strata at the faults as opposed to chemical processes acting at the fault zone. The studies also provide (1) guidelines for understanding and estimating the geophysical parameters controlling aeromagnetic anomalies at faulted strata (Grauch and Hudson), and (2) observations on key geologic factors that are favorable for developing similar sedimentary sources of aeromagnetic anomalies elsewhere (Hudson et al.).
2017-05-01
Mamers Valles is a long sinuous canyon beginning in Arabia Terra and ending in the Northern lowlands of Deuteronilus Mensae. This image from NASA Mars Reconnaissance Orbiter features the southern facing slope of the canyon wall. The northern half (top) has a rough, pitted texture with numerous impact craters, while the middle section shows the steep canyon wall. Streaks of slightly different colors show slope material eroding onto the canyon floor. Though the canyon itself was formed long ago, the material deposited on the canyon floor has been laid down over time, creating a much younger surface. The difference in age of the surfaces can also be indicated by the presence or absence of impact craters. The longer a surface has been exposed, the more impact craters it will accumulate. Counting craters to determine age estimates of planetary surfaces has been used throughout the solar system. This method is based on the assumption that the youngest, freshly formed surfaces will have no impact craters, and as time progresses crater impacts will accumulate at a predictable rate. This concept has been calibrated using crater counts on the Moon and the measured age of the rocks brought back by the Apollo missions. https://photojournal.jpl.nasa.gov/catalog/PIA21603
The Effect of C22 on Orbit Energy and Angular Momentum
NASA Astrophysics Data System (ADS)
Scheeres, D. J.
The recent interest in the problem of orbital mechanics about asteroids and comets presents new challenges for orbital mechanics. Interesting features of this problem include their relatively small mass (and hence large tidal perturbations from the sun), their irregular shape, their wide range of possible rotation states, and the seemingly infinite variety of sizes and shapes they come in. Interest in understanding dynamics about these bodies is driven by two main areas, understanding the natural dynamics about them for the advancement of asteroid and solar system science and understanding spacecraft dynamics about them to enable scientific missions to these bodies. The author has been interested in this problem for a number of years and produced several papers describing different aspects of this problem (Scheeres 1994, 1995, 1998c; Scheeres et al. 1996, 1998a, 1998b; Werner & Scheeres 1997). This presentation will give a brief summary of the interesting dynamics issues that arise due to the large elliptical shapes (i.e. large C22 gravity coefficient) when coupled with the uniform rotation of these bodies, and detail an approach that has been developed to deal with the large perturbations suffered by a particle as it orbits such a body. The large C22 problem, as found in the orbital mechanics about uniformly rotating asteroids and comets, has many interesting deviations from the ``planetary'' case where the magnitude of C22 is relatively small. To begin with, for a sufficiently large value of C22 and sufficiently short rotation period the two normally stable 1:1 resonance orbits may become complex unstable. This has a major impact for motion about these bodies, as the stable and unstable manifolds fill the 4-dimensional phase space (the phase space restricted to the ``equator''), influencing virtually all motion at nearby energy levels. Such bodies (termed ``Type II'', where ``Type I'' bodies have two stable 1:1 resonances) have certain additional characteristics
NASA Astrophysics Data System (ADS)
Zamaro, Mattia; Biggs, James D.
2014-12-01
The orbital dynamics around the Libration points of the classical circular restricted three-body problem (CR3BP) have been investigated in detail: in the last few decades, dynamical systems theory has provided invaluable analytical and numerical tools for understanding the dynamics of Libration Point Orbits (LPOs). The aim of this paper is to extend the model of the CR3BP to derive the LPOs in the vicinity of the Martian moon Phobos, which is becoming an appealing destination for scientific missions. The case of Phobos is particularly extreme, since the combination of both small mass-ratio and length-scale moves the collinear Libration manifold close to the moon's surface. Thus, a model of this system must consider additional dynamical perturbations, in particular the complete gravity field of Phobos, which is highly-inhomogeneous. This is accomplished using a spherical harmonics series expansion, deriving an enhanced elliptic three-body model. In this paper, we show how methodologies from dynamical systems theory are applied in differential correction continuation schemes to this proposed nonlinear model of the dynamics near Phobos, to derive the structure of the dynamical substitutes of the LPOs in this new system. Results obtained show that the structure of the LPOs differs substantially from the classical case without harmonics. The proposed methodology allows us to identify natural periodic and quasi-periodic orbits that would provide unique low-cost opportunities for close-range observations around Phobos and high-performance landing/take-off pathways to and from Phobos' surface, which could be exploited in upcoming missions targeting the exploration of this Martian moon.
Moore, Forrest O; Thornton, Brian P; Zabel, David D; Vasconez, Henry C
2004-11-01
Congenital anomalies of the orbital roof are rare occurrences. The case of a 2-year-old child with vertical orbital dystopia and abnormalities of the right bony orbit is presented. The patient underwent right orbital reconstruction to restore facial symmetry. A coronal approach with a frontal craniotomy was used for intracranial exposure. The abnormal angulation of the roof was corrected, and the defect was reconstructed with a split-calvarial bone graft harvested from the parietal region. The bone graft was secured with resorbable plate fixation. To preserve vision, reconstruction of this type must be done at an early age, preferably before the age of 4 years. In this patient, there is good facial symmetry and normal globe positioning 5 years after surgery.
CloudSat Anomaly Recovery and Operational Lessons Learned
NASA Technical Reports Server (NTRS)
Witkowski, Mona; Vane, Deborah; Livermore, Thomas; Rokey, Mark; Barthuli, Marda; Gravseth, Ian J.; Pieper, Brian; Rodzinak, Aaron; Silva, Steve; Woznick, Paul;
2012-01-01
In April 2011, NASA's pioneering cloud profiling radar satellite, CloudSat, experienced a battery anomaly that placed it into emergency mode and rendered it operations incapable. All initial attempts to recover the spacecraft failed as the resultant power limitations could not support even the lowest power mode. Originally part of a six-satellite constellation known as the "A-Train", CloudSat was unable to stay within its assigned control box, posing a threat to other A-Train satellites. CloudSat needed to exit the constellation, but with the tenuous power profile, conducting maneuvers was very risky. The team was able to execute a complex sequence of operations which recovered control, conducted an orbit lower maneuver, and returned the satellite to safe mode, within one 65 minute sunlit period. During the course of the anomaly recovery, the team developed several bold, innovative operational strategies. Details of the investigation into the root-cause and the multiple approaches to revive CloudSat are examined. Satellite communication and commanding during the anomaly are presented. A radical new system of "Daylight Only Operations" (DO-OP) was developed, which cycles the payload and subsystem components off in tune with earth eclipse entry and exit in order to maintain positive power and thermal profiles. The scientific methodology and operational results behind the graduated testing and ramp-up to DO-OP are analyzed. In November 2011, the CloudSat team successfully restored the vehicle to consistent operational collection of cloud radar data during sunlit portions of the orbit. Lessons learned throughout the six-month return-to-operations recovery effort are discussed and offered for application to other R&D satellites, in the context of on-orbit anomaly resolution efforts.
CloudSat Anomaly Recovery and Operational Lessons Learned
NASA Technical Reports Server (NTRS)
Witkowski, Mona; Vane, Deborah; Livermore, Thomas; Rokey, Mark; Barthuli, Marda; Gravseth, Ian J.; Pieper, Brian; Rodzinak, Aaron; Silva, Steve; Woznick, Paul; Nayak, Michael
2012-01-01
In April 2011, NASA's pioneering cloud profiling radar satellite, CloudSat, experienced a battery anomaly that placed it into emergency mode and rendered it operations incapable. All initial attempts to recover the spacecraft failed as the resultant power limitations could not support even the lowest power mode. Originally part of a six-satellite constellation known as the "A-Train", CloudSat was unable to stay within its assigned control box, posing a threat to other A-Train satellites. CloudSat needed to exit the constellation, but with the tenuous power profile, conducting maneuvers was very risky. The team was able to execute a complex sequence of operations which recovered control, conducted an orbit lower maneuver, and returned the satellite to safe mode, within one 65 minute sunlit period. During the course of the anomaly recovery, the team developed several bold, innovative operational strategies. Details of the investigation into the root-cause and the multiple approaches to revive CloudSat are examined. Satellite communication and commanding during the anomaly are presented. A radical new system of "Daylight Only Operations" (DO-OP) was developed, which cycles the payload and subsystem components off in tune with earth eclipse entry and exit in order to maintain positive power and thermal profiles. The scientific methodology and operational results behind the graduated testing and ramp-up to DO-OP are analyzed. In November 2011, the CloudSat team successfully restored the vehicle to consistent operational collection of cloud radar data during sunlit portions of the orbit. Lessons learned throughout the six-month return-to-operations recovery effort are discussed and offered for application to other R&D satellites, in the context of on-orbit anomaly resolution efforts.
2000-01-01
best to solve the inverse (global) IFS-Problem. Thus the Collage Theorem which can be used to generate whole objects of an image is given: A set {oi...is called an attractor of W. The Collage Theorem (CT) for attractors close to given compact sets: h(L, W(L)) 5 F => h(L, A) • 6/l _ s) where h is...p-bsinp v I I - - - - - X2 y artan~y-= arctan.Ž1 Rx x Lemma 4 A power n E G of an affine trainsformation maps V E Rek(P again to 3R. e Rek(P. V( ne
A Comparative Evaluation of Anomaly Detection Algorithms for Maritime Video Surveillance
2011-01-01
A variety of anomaly detection algorithms have been applied to surveillance tasks for detecting threats with some success. However, it is not clear...which anomaly detection algorithms should be used for domains such as ground-based maritime video surveillance. For example, recently introduced...Also, the reasons for the performance differences of anomaly detection algorithms on problems of varying difficulty are not well understood. We
A general time element for orbit integration in Cartesian coordinates
NASA Technical Reports Server (NTRS)
Janin, G.; Bond, V. R.
1981-01-01
Two techniques are discussed for increasing the accuracy of the numerical integration of eccentric orbits in Cartesian coordinates. One involves the use of an independent variable different from time; this increases the efficiency of the numerical integration. The other uses a time element, which reduces the in-track error. A general expression is given of a time element valid for an arbitrary independent variable. It is pointed out that this time element makes it possible to switch the independent variable merely by applying a scaling factor; there is no need to change the differential equations of the motion. Eccentric, true, and elliptic anomalies are used as independent variables in the case of a transfer orbit for a geosynchronous orbit. The elliptic anomaly is shown to perform much better than the other classical anomalies.
Propagation of atmospheric density errors to satellite orbits
NASA Astrophysics Data System (ADS)
Emmert, J. T.; Warren, H. P.; Segerman, A. M.; Byers, J. M.; Picone, J. M.
2017-01-01
We develop and test approximate analytic expressions relating time-dependent atmospheric density errors to errors in the mean motion and mean anomaly orbital elements. The mean motion and mean anomaly errors are proportional to the first and second integrals, respectively, of the density error. This means that the mean anomaly (and hence the in-track position) error variance grows with time as t3 for a white noise density error process and as t5 for a Brownian motion density error process. Our approximate expressions are accurate over a wide range of orbital configurations, provided the perigee altitude change is less than ∼0.2 atmospheric scale heights. For orbit prediction, density forecasts are driven in large part by forecasts of solar extreme ultraviolet (EUV) irradiance; we show that errors in EUV ten-day forecasts (and consequently in the density forecasts) approximately follow a Brownian motion process.
NASA Technical Reports Server (NTRS)
Rapp, R. H.
1974-01-01
The equations needed for the incorporation of gravity anomalies as unknown parameters in an orbit determination program are described. These equations were implemented in the Geodyn computer program which was used to process optical satellite observations. The arc dependent parameter unknowns, 184 unknown 15 deg and coordinates of 7 tracking stations were considered. Up to 39 arcs (5 to 7 days) involving 10 different satellites, were processed. An anomaly solution from the satellite data and a combination solution with 15 deg terrestrial anomalies were made. The limited data samples indicate that the method works. The 15 deg anomalies from various solutions and the potential coefficients implied by the different solutions are reported.
NASA Technical Reports Server (NTRS)
Hoyt, Robert (Inventor); Slostad, Jeffrey T. (Inventor); Frank, Scott (Inventor); Barnes, Ian M. (Inventor)
2016-01-01
Orbital winch having: lower and upper frames; spool having upper and lower flanges with lower flange attached to lower frame; axial tether guide mounted to upper frame; secondary slewing ring coaxial with spool and rotatably mounted to upper frame, wherein secondary slewing ring's outer surface has gearing; upper tether guide mounted to inner surface of secondary slewing ring; linear translation means having upper end mounted to upper frame and lower end mounted on lower frame; primary slewing ring rotatably mounted within linear translation means allowing translation axially between flanges, wherein primary slewing ring's outer surface has gearing; lower tether guide mounted on primary slewing ring's inner surface; pinion rod having upper end mounted to upper frame and lower end mounted to lower frame, wherein pinion rod's teeth engage primary and secondary slewing rings' outer surface teeth; and tether passing through axial, upper, and lower tether guides and winding around spool.
Borbolla-Pertierra, A M; Morales-Baños, D R; Martínez-Nava, L R; Garrido-Sánchez, G A; López-Hernández, C M; Velasco-Ramos, P
2017-02-01
The case is presented of a 46-year-old male with right eye proptosis and conjunctival hyperaemia, of 18 months onset. A well-defined intraconal mass was found in the computed tomography. In magnetic resonance this was hypo-intense on T1, enhanced with gadolinium and hyperintense on T2. Excisional biopsy was performed, which was reported as a well-differentiated liposarcoma in the histopathology study. Liposarcoma is a malignant adipose tissue tumour. It is very rare in the orbit, with 5 histological types, the most common being myxoid. The treatment of choice is wide surgical excision and may be accompanied with radiotherapy. As it is an infiltrative tumour, It has a high rate of recurrence. Copyright © 2016 Sociedad Española de Oftalmología. Publicado por Elsevier España, S.L.U. All rights reserved.
MAGSAT anomaly map and continental drift
NASA Technical Reports Server (NTRS)
Lemouel, J. L. (Principal Investigator); Galdeano, A.; Ducruix, J.
1981-01-01
Anomaly maps of high quality are needed to display unambiguously the so called long wave length anomalies. The anomalies were analyzed in terms of continental drift and the nature of their sources is discussed. The map presented confirms the thinness of the oceanic magnetized layer. Continental magnetic anomalies are characterized by elongated structures generally of east-west trend. Paleomagnetic reconstruction shows that the anomalies found in India, Australia, and Antarctic exhibit a fair consistency with the African anomalies. It is also shown that anomalies are locked under the continents and have a fixed geometry.
Interpretation of magnetic anomalies using a genetic algorithm
NASA Astrophysics Data System (ADS)
Kaftan, İlknur
2017-07-01
A genetic algorithm (GA) is an artificial intelligence method used for optimization. We applied a GA to the inversion of magnetic anomalies over a thick dike. Inversion of nonlinear geophysical problems using a GA has advantages because it does not require model gradients or well-defined initial model parameters. The evolution process consists of selection, crossover, and mutation genetic operators that look for the best fit to the observed data and a solution consisting of plausible compact sources. The efficiency of a GA on both synthetic and real magnetic anomalies of dikes by estimating model parameters, such as depth to the top of the dike (H), the half-width of the dike (B), the distance from the origin to the reference point (D), the dip of the thick dike (δ), and the susceptibility contrast (k), has been shown. For the synthetic anomaly case, it has been considered for both noise-free and noisy magnetic data. In the real case, the vertical magnetic anomaly from the Pima copper mine in Arizona, USA, and the vertical magnetic anomaly in the Bayburt-Sarıhan skarn zone in northeastern Turkey have been inverted and interpreted. We compared the estimated parameters with the results of conventional inversion methods used in previous studies. We can conclude that the GA method used in this study is a useful tool for evaluating magnetic anomalies for dike models.
Mixtures of Probabilistic Principal Component Analyzers for Anomaly Detection
Fang, Yi; Ganguly, Auroop R
2007-01-01
Anomaly detection tools have been increasingly used in recent years to generate predictive insights on rare events. The typical challenges encountered in such applications include a large number of data dimensions and absence of labeled data. An anomaly detection strategy for these scenarios is dimensionality reduction followed by clustering in the reduced space, with the degree of anomaly of an event or observation quantified by statistical distance from the clusters. However, most research efforts so far are focused on single abrupt anomalies, while the correlation between observations is completely ignored. In this paper, we address the problem of detection of both abrupt and sustained anomalies with high dimensions. The task becomes more challenging than only detecting abrupt outliers because of the gradual and indiscriminant changes in sustained anomalies. We utilize a mixture model of probabilistic principal component analyzers to quantify each observation by probabilistic measures. A statistical process control method is then used to monitor both abrupt and gradual changes. On the other hand, the mixture model can be regarded as a trade-off strategy between linear and nonlinear dimensionality reductions in terms of computational efficiency. This compromise is particularly important in real-time deployment. The proposed method is evaluated on simulated and benchmark data, as well as on data from wide-area sensors at a truck weigh station test-bed.
Detecting anomalies in CMB maps: a new method
Neelakanta, Jayanth T.
2015-10-01
Ever since WMAP announced its first results, different analyses have shown that there is weak evidence for several large-scale anomalies in the CMB data. While the evidence for each anomaly appears to be weak, the fact that there are multiple seemingly unrelated anomalies makes it difficult to account for them via a single statistical fluke. So, one is led to considering a combination of these anomalies. But, if we ''hand-pick'' the anomalies (test statistics) to consider, we are making an a posteriori choice. In this article, we propose two statistics that do not suffer from this problem. The statistics are linear and quadratic combinations of the a{sub ℓ m}'s with random co-efficients, and they test the null hypothesis that the a{sub ℓ m}'s are independent, normally-distributed, zero-mean random variables with an m-independent variance. The motivation for considering multiple modes is this: because most physical models that lead to large-scale anomalies result in coupling multiple ℓ and m modes, the ''coherence'' of this coupling should get enhanced if a combination of different modes is considered. In this sense, the statistics are thus much more generic than those that have been hitherto considered in literature. Using fiducial data, we demonstrate that the method works and discuss how it can be used with actual CMB data to make quite general statements about the incompatibility of the data with the null hypothesis.
Detecting anomalies in CMB maps: a new method
NASA Astrophysics Data System (ADS)
Neelakanta, Jayanth T.
2015-10-01
Ever since WMAP announced its first results, different analyses have shown that there is weak evidence for several large-scale anomalies in the CMB data. While the evidence for each anomaly appears to be weak, the fact that there are multiple seemingly unrelated anomalies makes it difficult to account for them via a single statistical fluke. So, one is led to considering a combination of these anomalies. But, if we ``hand-pick'' the anomalies (test statistics) to consider, we are making an a posteriori choice. In this article, we propose two statistics that do not suffer from this problem. The statistics are linear and quadratic combinations of the al m's with random co-efficients, and they test the null hypothesis that the al m's are independent, normally-distributed, zero-mean random variables with an m-independent variance. The motivation for considering multiple modes is this: because most physical models that lead to large-scale anomalies result in coupling multiple l and m modes, the ``coherence'' of this coupling should get enhanced if a combination of different modes is considered. In this sense, the statistics are thus much more generic than those that have been hitherto considered in literature. Using fiducial data, we demonstrate that the method works and discuss how it can be used with actual CMB data to make quite general statements about the incompatibility of the data with the null hypothesis.
Relationship Between Seismic Velocity Anomalies and Rheological Anomalies
NASA Astrophysics Data System (ADS)
Karato, S.
2001-05-01
One of the ultimate goals of high-resolution Earth models is to reveal anomalies (lateral variations) in thermal and rheological structures. Although such a relationship has been well known at a qualitative level, no quantitative relationship has been established to allow estimate of anomalies in viscosity from seismological data. In this presentation, I formulate such a relationship for Earth's upper mantle, based on the latest mineral physics observations. The key in doing this is the quantitative analysis of the effects of water on seismic wave velocities. Earlier analysis indicated the importance of water on seismic wave velocities through enhanced attenuation (Karato, 1995). I have quantified this notion by combining laboratory observations on attenuation at limited conditions (Jackson et al., 1992) with the recent quantitative data on the effects of water on rheology at wider conditions (Karato and Jung, 2001). I show that both seismic wave velocities and rheology (viscosity) of Earth materials are controlled by "rheologically effective temperature (Teff)" that depends on temperature as well as water content. Such an analysis allows us to define the relationships between velocity anomalies and anomalies in Teff and hence anomalies in viscosity. The present formulation has been applied to the upper mantle beneath northeastern Japan where the high-resolution tomographic images are available. The results show that anomalies in effective temperatures of ~+400 K occur in these regions indicating that viscosity there could be lower than the average values by a factor of ~10 to ~1000. References Jackson, I. et al. (1992), Geophys. J. Int., 108: 517-534. Karato, S. (1995), Proc. Japan Academy, B71: 61-66. Karato, S. and Jung, H. (2001), submitted to Philos. Mag.
Best Mitigation Paths To Effectively Reduce Earth's Orbital Debris
NASA Technical Reports Server (NTRS)
Wiegman, Bruce M.
2009-01-01
This slide presentation reviews some ways to reduce the problem posed by debris in orbit around the Earth. It reviews the orbital debris environment, the near-term needs to minimize the Kessler syndrome, also known as collisional cascading, a survey of active orbital debris mitigation strategies, the best paths to actively remove orbital debris, and technologies that are required for active debris mitigation.
On the effect of eccentricity of a planetary orbit on the stability of satellite orbits
NASA Astrophysics Data System (ADS)
Ichtiaroglou, S.; Voyatzis, G.
1990-03-01
The effect of the eccentricity of a planet's orbit on the stability of the orbits of its satellites is studied. The model used is the elliptic Hill case of the planar restricted three-body problem. The linear stability of all the known families of periodic orbits is computed. No stable orbits are found, the majority of them possessing one or two pairs of real eigenvalues of the monodromy matrix, while some with complex instability are found. Two families of periodic orbits, bifurcating from the Lagrangian points of the corresponding circular case are found analytically. These orbits are very unstable and the determination of their stability coefficients is not accurate.
NASA Astrophysics Data System (ADS)
Boccaletti, Dino; Pucacco, Giuseppe
This textbook treats Celestial Mechanics as well as Stellar Dynamics from the common point of view of orbit theory making use of the concepts and techniques from modern geometric mechanics. It starts with elementary Newtonian Mechanics and ends with the dynamics of chaotic motions. The book is meant for students in astronomy and physics alike. Prerequisite is a physicist's knowledge of calculus and differential geometry. Volume 1 begins with classical mechanics and a thorough treatment of the 2-body problem, including regularization, followed by an introduction to the N-body problem with particular attention given to the virial theorem. Then the authors discuss all important non-perturbative aspects of the 3-body problem. A final chapter deals with integrability of Hamilton-Jacobi-systems.
Astrometric Determination of VSOP-2 Orbital Parameters
NASA Astrophysics Data System (ADS)
Fomalont, E.; Moellenbrock, G.; Claussen, M.
2009-08-01
VSOP-2 phase referencing, needed to image faint sources and to determine accurate positions, will require an orbit accuracy of about 2 cm at 23 GHz. This accuracy, however, may not be obtainable by direct orbital measurements. We propose an observation scheme, similar to that used at the VLBA, to be included during a phase referencing observation of about one orbit in order to determine a more accurate orbit determination. We show the effects of orbit errors, explain the suggested observations and reduction methods, and discuss the potential problems that might impede the use of this technique.
Algorithm development for hyperspectral anomaly detection
NASA Astrophysics Data System (ADS)
Rosario, Dalton S.
2008-10-01
This dissertation proposes and evaluates a novel anomaly detection algorithm suite for ground-to-ground, or air-to-ground, applications requiring automatic target detection using hyperspectral (HS) data. Targets are manmade objects in natural background clutter under unknown illumination and atmospheric conditions. The use of statistical models herein is purely for motivation of particular formulas for calculating anomaly output surfaces. In particular, formulas from semiparametrics are utilized to obtain novel forms for output surfaces, and alternative scoring algorithms are proposed to calculate output surfaces that are comparable to those of semiparametrics. Evaluation uses both simulated data and real HS data from a joint data collection effort between the Army Research Laboratory and the Army Armament Research Development & Engineering Center. A data transformation method is presented for use by the two-sample data structure univariate semiparametric and nonparametric scoring algorithms, such that, the two-sample data are mapped from their original multivariate space to an univariate domain, where the statistical power of the univariate scoring algorithms is shown to be improved relative to existing multivariate scoring algorithms testing the same two-sample data. An exhaustive simulation experimental study is conducted to assess the performance of different HS anomaly detection techniques, where the null and alternative hypotheses are completely specified, including all parameters, using multivariate normal and mixtures of multivariate normal distributions. Finally, for ground-to-ground anomaly detection applications, where the unknown scales of targets add to the problem complexity, a novel global anomaly detection algorithm suite is introduced, featuring autonomous partial random sampling (PRS) of the data cube. The PRS method is proposed to automatically sample the unknown background clutter in the test HS imagery, and by repeating multiple times this
NASA Astrophysics Data System (ADS)
Ma, Hongliang; Xu, Shijie
2016-11-01
By defining two open-time impulse points, the optimization of a two-impulse, open-time terminal rendezvous and docking with target spacecraft on large-eccentricity elliptical orbit is proposed in this paper. The purpose of optimization is to minimize the velocity increment for a terminal elliptic-reference-orbit rendezvous and docking. Current methods for solving this type of optimization problem include for example genetic algorithms and gradient based optimization. Unlike these methods, interval methods can guarantee that the globally best solution is found for a given parameterization of the input. The non-linear Tschauner- Hempel(TH) equations of the state transitions for a terminal elliptic target orbit are transformed form time domain to target orbital true anomaly domain. Their homogenous solutions and approximate state transition matrix for the control with a short true anomaly interval can be used to avoid interval integration. The interval branch and bound optimization algorithm is introduced for solving the presented rendezvous and docking optimization problem and optimizing two open-time impulse points and thruster pulse amplitudes, which systematically eliminates parts of the control and open-time input spaces that do not satisfy the path and final time state constraints. Several numerical examples are undertaken to validate the interval optimization algorithm. The results indicate that the sufficiently narrow spaces containing the global optimization solution for the open-time two-impulse terminal rendezvous and docking with target spacecraft on large-eccentricity elliptical orbit can be obtained by the interval algorithm (IA). Combining the gradient-based method, the global optimization solution for the discontinuous nonconvex optimization problem in the specifically remained search space can be found. Interval analysis is shown to be a useful tool and preponderant in the discontinuous nonconvex optimization problem of the terminal rendezvous and
Halo orbit to science orbit captures at planetary moons
NASA Astrophysics Data System (ADS)
Bokelmann, Kevin A.; Russell, Ryan P.
2017-05-01
Ballisticly connecting halo orbits to science orbits in the circular-restricted three-body problem is investigated. Two classes of terminal science orbits are considered: low-altitude, tight orbits that are deep in the gravity well of the secondary body, and high-altitude, loose orbits that are strongly perturbed by the gravity of the primary body. General analytic expressions are developed to provide a minimum bound on impulse cost in both the circular restricted and the Hill's approximations. The equations are applied to a broad range of planetary moons, providing a mission design reference. Systematic grid search methods are developed to numerically find feasible transfers from halo orbits at Europa, confirming the analytical lower bound formulas. The two-impulse capture options in the case of Europa reveal a diverse set of potential solutions. Tight captures result in maneuver costs of 425-550 m/s while loose captures are found with costs as low as 30 m/s. The terminal orbits are verified to avoid escape or impact for at least 45 days.
Improving the geological interpretation of magnetic and gravity satellite anomalies
NASA Technical Reports Server (NTRS)
Hinze, William J.; Braile, Lawrence W.; Vonfrese, Ralph R. B.
1987-01-01
Quantitative analysis of the geologic component of observed satellite magnetic and gravity fields requires accurate isolation of the geologic component of the observations, theoretically sound and viable inversion techniques, and integration of collateral, constraining geologic and geophysical data. A number of significant contributions were made which make quantitative analysis more accurate. These include procedures for: screening and processing orbital data for lithospheric signals based on signal repeatability and wavelength analysis; producing accurate gridded anomaly values at constant elevations from the orbital data by three-dimensional least squares collocation; increasing the stability of equivalent point source inversion and criteria for the selection of the optimum damping parameter; enhancing inversion techniques through an iterative procedure based on the superposition theorem of potential fields; and modeling efficiently regional-scale lithospheric sources of satellite magnetic anomalies. In addition, these techniques were utilized to investigate regional anomaly sources of North and South America and India and to provide constraints to continental reconstruction. Since the inception of this research study, eleven papers were presented with associated published abstracts, three theses were completed, four papers were published or accepted for publication, and an additional manuscript was submitted for publication.
Prevalence of Ocular Anomalies among Schoolchildren in Ashaiman, Ghana.
Nartey, Emmanuel T; van Staden, Diane B; Amedo, Angel O
2016-06-01
Information on ocular anomalies can help in developing specific interventions to prevent visual impairment especially among children. The aim of this study was therefore to determine the prevalence, the causes of ocular anomalies, and their impact on vision of schoolchildren in Ghana. A cluster random sampling technique was used to select four government primary schools in Ashaiman Municipal for this study. Each pupil underwent ocular examination involving visual acuity, external examination, anterior and posterior segment examination, and objective and subjective refraction. They also answered questions relating to ocular problems affecting them. A total of 811 pupils were sampled, with ages ranging from 6 to 16 years. The mean age of the sampled population was 10.6 years (95% confidence interval, 10.4 to 10.8). Prevalence of ocular anomalies was 27.3% (95% confidence interval, 24.2 to 30.5). Allergic conjunctivitis (17.3%) and refractive errors (6.8%) were the main causes of ocular anomalies. Others include pinguecula (1.2%), pterygia (0.9%), infectious conjunctivitis (0.3%), corneal opacity (0.1%), lens opacity (0.1%), and retinal degeneration (0.1%). Ocular anomalies and refractive errors were significantly associated with sex (p = 0.04 and p = 0.01, respectively). Presenting visual acuity in the better eye 20/40 or worse was identified in 5.3% of schoolchildren, and 0.5% had moderate visual impairment. Only 11.8% of schoolchildren with ocular anomalies had been treated for their ocular problems before the study. The prevalence and causes of ocular anomalies found in this study suggest a need for more targeted eye health interventions such as school eye screening for early diagnosis and treatment of any presenting conditions among schoolchildren.
Graph anomalies in cyber communications
Vander Wiel, Scott A; Storlie, Curtis B; Sandine, Gary; Hagberg, Aric A; Fisk, Michael
2011-01-11
Enterprises monitor cyber traffic for viruses, intruders and stolen information. Detection methods look for known signatures of malicious traffic or search for anomalies with respect to a nominal reference model. Traditional anomaly detection focuses on aggregate traffic at central nodes or on user-level monitoring. More recently, however, traffic is being viewed more holistically as a dynamic communication graph. Attention to the graph nature of the traffic has expanded the types of anomalies that are being sought. We give an overview of several cyber data streams collected at Los Alamos National Laboratory and discuss current work in modeling the graph dynamics of traffic over the network. We consider global properties and local properties within the communication graph. A method for monitoring relative entropy on multiple correlated properties is discussed in detail.
Boundary terms of conformal anomaly
NASA Astrophysics Data System (ADS)
Solodukhin, Sergey N.
2016-01-01
We analyze the structure of the boundary terms in the conformal anomaly integrated over a manifold with boundaries. We suggest that the anomalies of type B, polynomial in the Weyl tensor, are accompanied with the respective boundary terms of the Gibbons-Hawking type. Their form is dictated by the requirement that they produce a variation which compensates the normal derivatives of the metric variation on the boundary in order to have a well-defined variational procedure. This suggestion agrees with recent findings in four dimensions for free fields of various spins. We generalize this consideration to six dimensions and derive explicitly the respective boundary terms. We point out that the integrated conformal anomaly in odd dimensions is non-vanishing due to the boundary terms. These terms are specified in three and five dimensions.
Shortening anomalies in supersymmetric theories
Gomis, Jaume; Komargodski, Zohar; Ooguri, Hirosi; ...
2017-01-17
We present new anomalies in two-dimensional N = (2, 2) superconformal theories. They obstruct the shortening conditions of chiral and twisted chiral multiplets at coincident points. This implies that marginal couplings cannot be promoted to background superfields in short representations. Therefore, standard results that follow from N = (2, 2) spurion analysis are invalidated. These anomalies appear only if supersymmetry is enhanced beyond N = (2; 2). These anomalies explain why the conformal manifolds of the K3 and T4 sigma models are not Kähler and do not factorize into chiral and twisted chiral moduli spaces and why there are nomore » N = (2, 2) gauged linear sigma models that cover these conformal manifolds. We also present these results from the point of view of the Riemann curvature of conformal manifolds.« less
Shortening anomalies in supersymmetric theories
NASA Astrophysics Data System (ADS)
Gomis, Jaume; Komargodski, Zohar; Ooguri, Hirosi; Seiberg, Nathan; Wang, Yifan
2017-01-01
We present new anomalies in two-dimensional N=(2,2) superconformal theories. They obstruct the shortening conditions of chiral and twisted chiral multiplets at coincident points. This implies that marginal couplings cannot be promoted to background superfields in short representations. Therefore, standard results that follow from N=(2,2) spurion analysis are invalidated. These anomalies appear only if supersymmetry is enhanced beyond N=(2,2) . These anomalies explain why the conformal manifolds of the K3 and T 4 sigma models are not Kähler and do not factorize into chiral and twisted chiral moduli spaces and why there are no N=(2,2) gauged linear sigma models that cover these conformal manifolds. We also present these results from the point of view of the Riemann curvature of conformal manifolds.
Electromagnetic duality and entanglement anomalies
NASA Astrophysics Data System (ADS)
Donnelly, William; Michel, Ben; Wall, Aron C.
2017-08-01
Duality is an indispensable tool for describing the strong-coupling dynamics of gauge theories. However, its actual realization is often quite subtle: quantities such as the partition function can transform covariantly, with degrees of freedom rearranged in a nonlocal fashion. We study this phenomenon in the context of the electromagnetic duality of Abelian p -forms. A careful calculation of the duality anomaly on an arbitrary D -dimensional manifold shows that the effective actions agree exactly in odd D , while in even D they differ by a term proportional to the Euler number. Despite this anomaly, the trace of the stress tensor agrees between the dual theories. We also compute the change in the vacuum entanglement entropy under duality, relating this entanglement anomaly to the duality of an "edge mode" theory in two fewer dimensions. Previous work on this subject has led to conflicting results; we explain and resolve these discrepancies.
The Nimbus 6 data catalog. Volume 7: 1 July - 31 August 1976. Data orbits 5156 - 5985
NASA Technical Reports Server (NTRS)
1977-01-01
Operations of various experiments during the reporting period are summarized. Orbital elements, data availability times, anomalies in the data, geographic location, and time of data are tabulated. Montages obtained by infrared and microwave radiometers are included.
Orbital State Uncertainty Realism
NASA Astrophysics Data System (ADS)
Horwood, J.; Poore, A. B.
2012-09-01
Fundamental to the success of the space situational awareness (SSA) mission is the rigorous inclusion of uncertainty in the space surveillance network. The *proper characterization of uncertainty* in the orbital state of a space object is a common requirement to many SSA functions including tracking and data association, resolution of uncorrelated tracks (UCTs), conjunction analysis and probability of collision, sensor resource management, and anomaly detection. While tracking environments, such as air and missile defense, make extensive use of Gaussian and local linearity assumptions within algorithms for uncertainty management, space surveillance is inherently different due to long time gaps between updates, high misdetection rates, nonlinear and non-conservative dynamics, and non-Gaussian phenomena. The latter implies that "covariance realism" is not always sufficient. SSA also requires "uncertainty realism"; the proper characterization of both the state and covariance and all non-zero higher-order cumulants. In other words, a proper characterization of a space object's full state *probability density function (PDF)* is required. In order to provide a more statistically rigorous treatment of uncertainty in the space surveillance tracking environment and to better support the aforementioned SSA functions, a new class of multivariate PDFs are formulated which more accurately characterize the uncertainty of a space object's state or orbit. The new distribution contains a parameter set controlling the higher-order cumulants which gives the level sets a distinctive "banana" or "boomerang" shape and degenerates to a Gaussian in a suitable limit. Using the new class of PDFs within the general Bayesian nonlinear filter, the resulting filter prediction step (i.e., uncertainty propagation) is shown to have the *same computational cost as the traditional unscented Kalman filter* with the former able to maintain a proper characterization of the uncertainty for up to *ten
Analysis of DSN software anomalies
NASA Technical Reports Server (NTRS)
Galorath, D. D.; Hecht, H.; Hecht, M.; Reifer, D. J.
1981-01-01
A categorized data base of software errors which were discovered during the various stages of development and operational use of the Deep Space Network DSN/Mark 3 System was developed. A study team identified several existing error classification schemes (taxonomies), prepared a detailed annotated bibliography of the error taxonomy literature, and produced a new classification scheme which was tuned to the DSN anomaly reporting system and encapsulated the work of others. Based upon the DSN/RCI error taxonomy, error data on approximately 1000 reported DSN/Mark 3 anomalies were analyzed, interpreted and classified. Next, error data are summarized and histograms were produced highlighting key tendencies.
Anomaly Monitoring Method for Key Components of Satellite
Fan, Linjun; Xiao, Weidong; Tang, Jun
2014-01-01
This paper presented a fault diagnosis method for key components of satellite, called Anomaly Monitoring Method (AMM), which is made up of state estimation based on Multivariate State Estimation Techniques (MSET) and anomaly detection based on Sequential Probability Ratio Test (SPRT). On the basis of analysis failure of lithium-ion batteries (LIBs), we divided the failure of LIBs into internal failure, external failure, and thermal runaway and selected electrolyte resistance (R e) and the charge transfer resistance (R ct) as the key parameters of state estimation. Then, through the actual in-orbit telemetry data of the key parameters of LIBs, we obtained the actual residual value (R X) and healthy residual value (R L) of LIBs based on the state estimation of MSET, and then, through the residual values (R X and R L) of LIBs, we detected the anomaly states based on the anomaly detection of SPRT. Lastly, we conducted an example of AMM for LIBs, and, according to the results of AMM, we validated the feasibility and effectiveness of AMM by comparing it with the results of threshold detective method (TDM). PMID:24587703
Anomaly monitoring method for key components of satellite.
Peng, Jian; Fan, Linjun; Xiao, Weidong; Tang, Jun
2014-01-01
This paper presented a fault diagnosis method for key components of satellite, called Anomaly Monitoring Method (AMM), which is made up of state estimation based on Multivariate State Estimation Techniques (MSET) and anomaly detection based on Sequential Probability Ratio Test (SPRT). On the basis of analysis failure of lithium-ion batteries (LIBs), we divided the failure of LIBs into internal failure, external failure, and thermal runaway and selected electrolyte resistance (R(e)) and the charge transfer resistance (R(ct)) as the key parameters of state estimation. Then, through the actual in-orbit telemetry data of the key parameters of LIBs, we obtained the actual residual value (R(X)) and healthy residual value (R(L)) of LIBs based on the state estimation of MSET, and then, through the residual values (R(X) and R(L)) of LIBs, we detected the anomaly states based on the anomaly detection of SPRT. Lastly, we conducted an example of AMM for LIBs, and, according to the results of AMM, we validated the feasibility and effectiveness of AMM by comparing it with the results of threshold detective method (TDM).
The initial flight anomalies of Skylab 1
NASA Technical Reports Server (NTRS)
1993-01-01
At approximately 63 seconds into the flight of Skylab 1 on May 14, 1973, an anomaly occurred which resulted in the complete loss of the meteoroid shield around the orbital workshop. This was followed by the loss of one of the two solar array systems on the workshop and a failure of the inter stage adapter to separate from the S-II stage of the Saturn V launch vehicle. The investigation reported herein identified the most probable cause of this flight anomaly to be the breakup and loss of the meteoroid shield due to aerodynamic loads that were not accounted for in its design. The breakup of the meteoroid shield, in turn, broke the tie downs that secured one of the solar array systems to the workshop. Complete loss of this solar array system occurred at 593 seconds when the exhaust plume of the S-II stage retro-rockets impacted the partially deployed solar array system. Falling debris from the meteoroid shield also damaged the S-II inter stage adapter ordnance system in such a manner as to preclude separation. Of several possible failure modes of the meteoroid shield that were identified, the most probable in this particular flight was internal pressurization of its auxiliary tunnel which acted to force the forward end of the meteoroid shield away from the shell of the workshop and into the supersonic air stream. The pressurization of the auxiliary tunnel was due to the existence of several openings in the aft region of the tunnel. Another possible failure mode was the separation of the leading edge of the meteoroid shield from the shell of the workshop (particularly in the region of the folded ordnance panel) of sufficient extent to admit ram air pressures under the shield.
NASA Astrophysics Data System (ADS)
Branham, R. L., Jr.
2003-11-01
Laplace's method is a standard for the calculation of a preliminary orbit. Certain modifications enhance its efficacy: reduce the observations, if necessary, by use of the L1 criterion; use a polynomial, whose order is determined by impersonal criteria, to calculate the first and second derivatives of observational quantities; combine the separate equations, one to determine the heliocentric distance of the object and the other its geocentric distance, into one polynomial equation for the heliocentric distance, whose roots are found by a standard algorithm; use recursion to calculate the f and g series. At least one differential correction is recommended to increase the accuracy of the computed orbital elements. Difficult problems, lack of convergence of the differential corrections, for example, can be handled by total least squares or ridge regression. The method is first applied to calculate a preliminary orbit of Comet P/ 1846 D1 (de Vico) from 59 observations made during five days in 1995 and then to a more difficult object, the Amor type minor planet 1982 DV (3288 Seleucus).
Characterization of Suomi-NPP VIIRS reflective solar bands dual gain anomaly
NASA Astrophysics Data System (ADS)
Lee, Shihyan; McIntire, Jeff; Oudrari, Hassan
2012-09-01
The Visible/Infrared Imager Radiometer Suite (VIIRS) contains six dual gain bands in the reflective solar spectrum. The dual gain bands are designed to switch gain mode at pre-defined thresholds to achieve high resolution at low radiances while maintaining the required dynamic range for science. During pre-launch testing, an anomaly in the electronic response before transitioning from high to low gain was discovered and was characterized. This anomaly has been confirmed using MODIS data collected during Simultaneous Nadir Overpasses (SNOs). The analysis of the Earth scene data shows that this dual gain anomaly can be characterized using sensor earth-view observations. To help understand this dual gain artifact, the anomaly region and electronic offsets were tracked during the first 8 months of VIIRS operation. The temporal analysis shows the anomaly region can drift ~20 DN and is impacted by a detector's DC Restore. The estimated anomaly flagging regions cover ~2.5 % of the high gain dynamic range and are consistent with prelaunch analysis and the on-orbit flagging LookUp Table. The prelaunch results had a smaller anomaly range, likely due to more stable electronics over a shorter data collection time. Finally, this study suggests future calibration efforts to focus on the anomaly's impact on science products and a possible correction method to reduce uncertainties.
NASA Technical Reports Server (NTRS)
Jackson, L. R.; Weidner, J. P.; Small, W. J.; Martin, J. A. (Inventor)
1981-01-01
The system includes reusable turbojet propelled booster vehicles releasably connected to a reusable rocket powered orbit vehicle. The coupled orbiter-booster combination takes off horizontally and ascends to staging altitude and speed under booster power with both orbiter and booster wings providing lift. After staging, the booster vehicles fly back to Earth for horizontal landing and the orbiter vehicle continues ascending to orbit.
NASA Technical Reports Server (NTRS)
1991-01-01
The debris problem has reached a stage at which the risk to satellites and spacecraft has become substantial in low Earth orbit (LEO). This research discovered that small particles posed little threat to spacecraft because shielding can effectively prevent these particles from damaging the spacecraft. The research also showed that, even though collision with a large piece of debris could destroy the spacecraft, the large pieces of debris pose little danger because they can be tracked and the spacecraft can be maneuvered away from these pieces. Additionally, there are many current designs to capture and remove large debris particles from the space environment. From this analysis, it was decided to concentrate on the removal of medium-sized orbital debris, that is, those pieces ranging from 1 cm to 50 cm in size. The current design incorporates a transfer vehicle and a netting vehicle to capture the medium-sized debris. The system is based near an operational space station located at 28.5 deg inclination and 400 km altitude. The system uses ground-based tracking to determine the location of a satellite breakup or debris cloud. These data are uploaded to the transfer vehicle, which proceeds to rendezvous with the debris at a lower altitude parking orbit. Next, the netting vehicle is deployed, tracks the targeted debris, and captures it. After expending the available nets, the netting vehicle returns to the transfer vehicle for a new netting module and continues to capture more debris in the target area. Once all the netting modules are expended, the transfer vehicle returns to the space station's orbit where it is resupplied with new netting modules from a space shuttle load. The new modules are launched by the shuttle from the ground and the expended modules are taken back to Earth for removal of the captured debris, refueling, and repacking of the nets. Once the netting modules are refurbished, they are taken back into orbit for reuse. In a typical mission, the
Magnetotransport of Weyl semimetals due to the chiral anomaly
NASA Astrophysics Data System (ADS)
Zyuzin, Vladimir A.
2017-06-01
We study the electric field and temperature gradient driven magnetoconductivity of a Weyl semimetal system. To analyze the responses, we utilize the kinetic equation with semiclassical equations of motion modified by the Berry curvature and orbital magnetization of the wave packet. Apart from the known positive quadratic magnetoconductivity, we show that due to the chiral anomaly, the magnetoconductivity can become a nonanalytic function of the magnetic field, proportional to the 3/2 power of the magnetic field at finite temperatures. We also show that time-reversal symmetry breaking tilt of the Dirac cones results in linear magnetoconductivity. This is due to the one-dimensional chiral anomaly for which the tilt is responsible.
Polar Wander on the Moon Inferred from its Shape and Magnetic Anomalies
NASA Astrophysics Data System (ADS)
Garrick-Bethell, I.
2015-12-01
The lunar shape can inform us about the Moon's early spin pole location, or history of true polar wander. This history is important for understanding the stability of polar ice deposits [1], and possible relationships between large-scale lunar features and the lunar orbit. Recently, Garrick-Bethell et al. [2] showed that when the effects of large basins are ignored, the Moon's early spin pole could be inferred from a tidal-rotational deformation that froze-in when the Moon was closer to the Earth. They also showed that the lunar shape is consistent with early tidal heating in the crust during the magma ocean epoch [3]. Here we will present some updates to this work, and discuss how the lunar spin pole may have evolved in time, as inferred from the progressive formation of large basins and components of the degree-2 gravity field that are not associated with basins. Separately, magnetic anomalies can address the problem of lunar polar wander, assuming the ancient dynamo that magnetized them was dominantly dipolar and aligned with the spin axis. However, recent surveys of magnetic anomalies reveal paleopole distributions that are quite complicated and inconsistent across different studies [4, 5]. Some reported paleopoles are consistent with the early spin pole inferred from the lunar shape [2], while others are not. These paleopoles imply either very large amounts of polar wander, or that the dynamo evolved with a complex field geometry. Some possible resolutions to these problems will be discussed, including secular variation of the magnetic field and difficulties with inversions for magnetic sources. References 1. Siegler, M. A. et al., 46th Lunar and Planetary Science Conference, LPI Contribution No. 1832, p. 2675 (2015). 2. Garrick-Bethell, I., et al., Nature 512, 181 (2014). 3. Garrick-Bethell, I., et al., Science 330, 949 (2010). 4. Arkani-Hamed, J. and Boutin, D., Icarus 237, 262 (2014). 5. Takahashi, F., et al., Nature Geoscience 7, 409 (2014).
Comparison of Methods of Height Anomaly Computation
NASA Astrophysics Data System (ADS)
Mazurova, E.; Lapshin, A.; Menshova, A.
2012-04-01
As of today, accurate determination of height anomaly is one of the most difficult problems of geodesy, even with sustainable perfection of mathematical methods, computer possibilities. The most effective methods of height anomaly computation are based on the methods of discrete linear transformations, such as the Fast Fourier Transform (FFT), Short-Time Fourier Transform (STFT), Fast Wavelet Transform (FWT). The main drawback of the classical FFT is weak localization in the time domain. If it is necessary to define the time interval of a frequency presence the STFT is used that allows one to detect the presence of any frequency signal and the interval of its presence. It expands the possibilities of the method in comparison with the classical Fourier Transform. However, subject to Heisenberg's uncertainty principle, it is impossible to tell precisely what frequency signal is present at a given moment of time (it is possible to speak only about the range of frequencies); and it is impossible to tell at what precisely moment of time the frequency signal is present (it is possible to speak only about a time span). A wavelet-transform gives the chance to reduce the influence of the Heisenberg's uncertainty principle on the obtained time-and-frequency representation of the signal. With its help low frequencies have more detailed representation relative to the time, and high frequencies - relative to the frequency. The paper summarizes the results of height anomaly calculations done by the FFT, STFT, FWT methods and represents 3-D models of calculation results. Key words: Fast Fourier Transform(FFT), Short-Time Fourier Transform (STFT), Fast Wavelet Transform(FWT), Heisenberg's uncertainty principle.
Coral can have growth anomalies
Coral growth anomalies (GAs) are changes in the coral cells that deposit the calcium carbonate skeleton. They usually appear as raised areas of the skeleton and tissue that are different from the surrounding normal areas on the same colony. The features include abnormal shape a...
Thermal anomalies in stressed Teflon.
NASA Technical Reports Server (NTRS)
Lee, S. H.; Wulff, C. A.
1972-01-01
In the course of testing polytetrafluoroethylene (Teflon) as a calorimetric gasketing material, serendipity revealed a thermal anomaly in stressed film that occurs concomitantly with the well-documented 25 C transition. The magnitude of the excess energy absorption - about 35 cal/g - is suggested to be related to the restricted thermal expansion of the film.
Global gravitational anomalies and transport
NASA Astrophysics Data System (ADS)
Chowdhury, Subham Dutta; David, Justin R.
2016-12-01
We investigate the constraints imposed by global gravitational anomalies on parity odd induced transport coefficients in even dimensions for theories with chiral fermions, gravitinos and self dual tensors. The η-invariant for the large diffeomorphism corresponding to the T transformation on a torus constraints the coefficients in the thermal effective action up to mod 2. We show that the result obtained for the parity odd transport for gravitinos using global anomaly matching is consistent with the direct perturbative calculation. In d = 6 we see that the second Pontryagin class in the anomaly polynomial does not contribute to the η-invariant which provides a topological explanation of this observation in the `replacement rule'. We then perform a direct perturbative calculation for the contribution of the self dual tensor in d = 6 to the parity odd transport coefficient using the Feynman rules proposed by Gaumé and Witten. The result for the transport coefficient agrees with that obtained using matching of global anomalies.
Connecting Stratospheric and Ionospheric Anomalies
NASA Astrophysics Data System (ADS)
Spraggs, M. E.; Goncharenko, L. P.; Zhang, S.; Coster, A. J.; Benkevitch, L. V.
2014-12-01
This study investigates any relationship between lunar phases and ionospheric anomalies that appear at low latitudes concurrently with sudden stratospheric warmings (SSWs). The study utilizes World-wide GPS Receiver Network Total Electron Content (TEC) data spanning 13 years (2001-2014) and focuses on the changes in the equatorial ionization anomaly the Western hemisphere. TEC is highly variable due to the influences of solar flux, geomagnetic activity, and seasonal variation and these influences are removed by the use of model. This empirical TEC model is a combination of linear dependencies of solar flux (F10.7) and geomagnetic activity (Ap3) with a third degree polynomial dependency for day-of-year (DOY). With such dependencies removed, the remaining TEC variation could be resolved and attributed to an appropriate mechanism. Lunar phase and apside was investigated in particular, especially the new and full moon phases during perigees when tidal forcing would be most powerful. Lunar tidal forcing on planetary waves is also examined as being physically responsible for setting up conditions that may give rise to SSWs and ionospheric anomalies. Preliminary results suggest that such anomalies may be enhanced in intensity during the full or new moon and even more so during perigee by different amounts depending on whether the SSW is a major (40-60%) or minor (20-45%) event.
Coral can have growth anomalies
Coral growth anomalies (GAs) are changes in the coral cells that deposit the calcium carbonate skeleton. They usually appear as raised areas of the skeleton and tissue that are different from the surrounding normal areas on the same colony. The features include abnormal shape a...
Conformal anomalies and gravitational waves
NASA Astrophysics Data System (ADS)
Meissner, Krzysztof A.; Nicolai, Hermann
2017-09-01
We argue that the presence of conformal anomalies in gravitational theories can lead to observable modifications to Einstein's equations via the induced anomalous effective actions, whose non-localities can overwhelm the smallness of the Planck scale. The fact that no such effects have been seen in recent cosmological or gravitational wave observations therefore imposes strong restrictions on the field content of possible extensions of Einstein's theory: all viable theories should have vanishing conformal anomalies. We then show that a complete cancellation of conformal anomalies in D = 4 for both the C2 invariant and the Euler (Gauss-Bonnet) invariant E4 can only be achieved for N-extended supergravity multiplets with N ⩾ 5, as well as for M theory compactified to four dimensions. Although there remain open questions, in particular concerning the true significance of conformal anomalies in non-conformal theories, as well as their possible gauge dependence for spin s ⩾3/2, these cancellations suggest a hidden conformal structure of unknown type in these theories.
Bony anomaly of Meckel's cave.
Tubbs, R Shane; Salter, E George; Oakes, W Jerry
2006-01-01
This study describes the seemingly rare occurrence of bone formation within the proximal superior aspect of Meckel's cave thus forming a bony foramen for the proximal trigeminal nerve to traverse. The anatomy of Meckel's cave is reviewed and the clinical potential for nerve compression from this bony anomaly discussed.
Familial polythelia associated with dental anomalies: a case report.
Fonseca, Gabriel M; Cantín, Mario
2014-01-01
Polythelia has been defined as the presence of supernumerary nipples without accessory glandular tissue. Usually, these growths follow imaginary mammary lines running from the armpits to the groin. Although the presence of dental anomalies may occasion only a simple cosmetic problem with specific clinical considerations, the association with familial polythelia has been scarcely reported. This paper reports on a case of polythelia that is associated with dental anomalies in an Argentine family and discusses suggestions for a thorough dental history and medical consultation to prevent possible pathological conditions or potential malignant transformation of mammary tissues.
Small Mercury Relativity Orbiter
NASA Technical Reports Server (NTRS)
Bender, Peter L.; Vincent, Mark A.
1989-01-01
The accuracy of solar system tests of gravitational theory could be very much improved by range and Doppler measurements to a Small Mercury Relativity Orbiter. A nearly circular orbit at roughly 2400 km altitude is assumed in order to minimize problems with orbit determination and thermal radiation from the surface. The spacecraft is spin-stabilized and has a 30 cm diameter de-spun antenna. With K-band and X-band ranging systems using a 50 MHz offset sidetone at K-band, a range accuracy of 3 cm appears to be realistically achievable. The estimated spacecraft mass is 50 kg. A consider-covariance analysis was performed to determine how well the Earth-Mercury distance as a function of time could be determined with such a Relativity Orbiter. The minimum data set is assumed to be 40 independent 8-hour arcs of tracking data at selected times during a two year period. The gravity field of Mercury up through degree and order 10 is solved for, along with the initial conditions for each arc and the Earth-Mercury distance at the center of each arc. The considered parameters include the gravity field parameters of degree 11 and 12 plus the tracking station coordinates, the tropospheric delay, and two parameters in a crude radiation pressure model. The conclusion is that the Earth-Mercury distance can be determined to 6 cm accuracy or better. From a modified worst-case analysis, this would lead to roughly 2 orders of magnitude improvement in the knowledge of the precession of perihelion, the relativistic time delay, and the possible change in the gravitational constant with time.
Small Mercury Relativity Orbiter
NASA Astrophysics Data System (ADS)
Bender, Peter L.; Vincent, Mark A.
1989-08-01
The accuracy of solar system tests of gravitational theory could be very much improved by range and Doppler measurements to a Small Mercury Relativity Orbiter. A nearly circular orbit at roughly 2400 km altitude is assumed in order to minimize problems with orbit determination and thermal radiation from the surface. The spacecraft is spin-stabilized and has a 30 cm diameter de-spun antenna. With K-band and X-band ranging systems using a 50 MHz offset sidetone at K-band, a range accuracy of 3 cm appears to be realistically achievable. The estimated spacecraft mass is 50 kg. A consider-covariance analysis was performed to determine how well the Earth-Mercury distance as a function of time could be determined with such a Relativity Orbiter. The minimum data set is assumed to be 40 independent 8-hour arcs of tracking data at selected times during a two year period. The gravity field of Mercury up through degree and order 10 is solved for, along with the initial conditions for each arc and the Earth-Mercury distance at the center of each arc. The considered parameters include the gravity field parameters of degree 11 and 12 plus the tracking station coordinates, the tropospheric delay, and two parameters in a crude radiation pressure model. The conclusion is that the Earth-Mercury distance can be determined to 6 cm accuracy or better. From a modified worst-case analysis, this would lead to roughly 2 orders of magnitude improvement in the knowledge of the precession of perihelion, the relativistic time delay, and the possible change in the gravitational constant with time.
Van den Berghe, H; Vermaelen, K; Mecucci, C; Barbieri, D; Tricot, G
1985-07-01
A deletion of the long arm of chromosome #5 (5q-) occurs nonrandomly in human malignancies. As a rule, the deletion is interstitial; the distal breakpoint by conventional techniques is usually in band q32, the proximal breakpoints in q12 or q14. Variant breakpoints occur in less than 10% of all cases. As the sole anomaly, 5q- is characteristically found in refractory anemia with or without excess of blasts. It can occur as the sole anomaly in de novo or secondary acute nonlymphocytic leukemia, but is usually accompanied in those disorders by other chromosome changes that are also nonrandomly distributed. In addition, it can be found in lymphoproliferative disorders, and occasionally, also in solid tumors. The 5q- myelodysplastic syndrome typically occurs in older age groups, particularly in females. Characteristic features are macrocytic anemia, normal or elevated platelets in the presence of megakaryocytic anomalies, and a mild clinical course. In cases with 5q- only, transformation into ANLL occurs rarely. Additional chromosome anomalies and male sex are prognostically unfavorable signs. Sex ratio is also at the disadvantage of females in de novo 5q- ANLL, and the latter disorder can occur without being preceded by a myelodysplastic phase. A myelodysplastic phase usually precedes 5q- secondary leukemia, in males as well as in females, and additional chromosome anomalies, especially of chromosome #7, are almost invariably present in those cases. We conclude that 5q- is the most frequently occurring single chromosome anomaly in secondary leukemia. Furthermore, the resemblance between de novo and secondary 5q- MDS and ANLL is striking; clinically, as well as cytogenetically, they are indistinguishable, suggesting that all de novo cases may be due to environmental (chemical) carcinogens. Response to treatment and prognosis are very poor with current therapeutic regimens in de novo as well as in secondary 5q- ANLL. Morphologically, these ANLLs fall into all FAB
Holonomy Attractor Connecting Spaces of Different Curvature Responsible for ``Anomalies''
NASA Astrophysics Data System (ADS)
Binder, Bernd
2009-03-01
In this lecture paper we derive Magic Angle Precession (MAP) from first geometric principles. MAP can arise in situations, where precession is multiply related to spin, linearly by time or distance (dynamic phase, rolling, Gauss law) and transcendentally by the holonomy loop path (geometric phase). With linear spin-precession coupling, gyroscopes can be spun up and down to very high frequencies via low frequency holonomy control induced by external accelerations, which provides for extreme coupling strengths or "anomalies" that can be tested by the powerball or gyrotwister device. Geometrically, a gyroscopic manifold with spherical metric is tangentially aligned to a precession wave channel with conic or hyperbolic metric (like the relativistic Thomas precession). Transporting triangular spin/precession vector relations across the tangential boundary of contact with SO(3) Lorentz symmetry, we get extreme vector currents near the attractor fixed points in precession phase space, where spin currents remain intact while crossing the contact boundaries between regions of different curvature signature (-1, 0, +1). The problem can be geometrically solved by considering a curvature invariant triangular condition, which holds on surfaces with different curvature that are in contact and locally parallel. In this case two out of three angles are identical, whereas the third angle is different due to holonomy. If we require that the side length ratio corresponding to these angles are invariant we get a geodesic chaotic attractor, which is a cosine map cos(x)˜Mx in parameter space providing for fixed points, limit cycle bifurcations, and singularities. The situation could be quite natural and common in the context of vector currents in curved spacetime and gauge theories. MAP could even be part of the electromagnetic interaction, where the electric charge is the geometric U(1) precession spin current and gauge potential with magnetic effects given by extra rotations under the
Analysis Methods of Environmental Induced Anomalies of Spacecraft
NASA Astrophysics Data System (ADS)
Catani, Jean-Pierre
2002-01-01
Thirty years after the first evidence of in-flight electrostatic discharges on synchronous spacecraft, they are still a threat. Analysis of anomalies will be always necessary for improving design guidelines and standards. A Ground Control Center dedicated to a Space System is monitoring for the nominal configuration of the spacecraft. An alarm or warning is triggered when the spacecraft gets out of its nominal working state. How to know what happens in flight? An electrostatic discharge is never observed itself but only its permanent consequences. Telemetry data is never designed for detecting unforeseen events, it is only defined for command purpose and good-health diagnosis. Probes are exceptionally implemented on commercial spacecraft to determine the state of environment at the location of the spacecraft at the time of the anomaly. The first step is the elimination of non-environmental causes: electromagnetic interference problem, equipment failure, corona discharge inside a high-voltage powered box, or man-made spurious command. Heavy ions or micrometeoroids are environmental causes with consequences that look like electrostatic discharges, so involving charging needs detailed and exhaustive analysis. The spacecraft-charging anomaly is at the end of a long chain of causes and consequences. Some regions of space have a radiation and particle content able to build up absolute and differential potentials at the surface or inside the spacecraft up to exceeding the breakdown voltage. Charges are released that induce electromagnetic fields in coupling current and voltage transients to cables. The pulses penetrate boxes and propagate along printed circuit board tracks, reaching active devices, upsetting logical devices, saturating amplifiers, or fusing lanes inside integrated circuits. Spacecraft event understanding is the conclusion of three convergent ways of analysis: environmental data, vacuum charging tests, electromagnetic immunity tests. When there is no borne
Utility of Satellite Magnetic Observations for Estimating Near-Surface Magnetic Anomalies
NASA Technical Reports Server (NTRS)
Kim, Hyung Rae; vonFrese, Ralph R. B.; Taylor, Patrick T.; Kim, Jeong Woo; Park, Chan Hong
2003-01-01
Regional to continental scale magnetic anomaly maps are becoming increasingly available from airborne, shipborne, and terrestrial surveys. Satellite data are commonly considered to fill the coverage gaps in regional compilations of these near-surface surveys. For the near-surface Antarctic magnetic anomaly map being produced by the Antarctic Digital Magnetic Anomaly Project (ADMAP), we show that near-surface magnetic anomaly estimation is greatly enhanced by the joint inversion of the near-surface data with the satellite observations relative to the conventional technique such as minimum curvature. Orsted observations are especially advantageous relative to the Magsat data that have order-of-magnitude greater measurement errors, albeit at much lower orbital altitudes. CHAMP is observing the geomagnetic field with the same measurement accuracy as the Orsted mission, but at the lower orbital altitudes covered by Magsat. Hence, additional significant improvement in predicting near-surface magnetic anomalies can result as these CHAMP data are available. Our analysis also suggests that considerable new insights on the magnetic properties of the lithosphere may be revealed by a further order-of-magnitude improvement in the accuracy of the magnetometer measurements at minimum orbital altitude.
Orbital Debris: Cost Impact on Setting Policy.
1996-06-01
As the exploration of space increases, the problems associated with orbital debris also increase. 0rbital debris continues to grow at a linear rate...and at worst, unusable. When mitigating orbital debris , cost and policy issues must be addressed. Currently no policy exists that makes the mitigation...of orbital debris mandatory but it only strongly recommends mitigation as long as it is cost effective. This thesis addresses the cost impact of
Electroweak Symmetry Breaking via UV Insensitive Anomaly Mediation
Kitano, Ryuichiro; Kribs, Graham D.; Murayama, Hitoshi
2004-02-19
Anomaly mediation solves the supersymmetric flavor and CP problems. This is because the superconformal anomaly dictates that supersymmetry breaking is transmitted through nearly flavor-blind infrared physics that is highly predictive and UV insensitive. Slepton mass squareds, however, are predicted to be negative. This can be solved by adding D-terms for U(1)_Y and U(1)_{B-L} while retaining the UV insensitivity. In this paper we consider electroweak symmetry breaking via UV insensitive anomaly mediation in several models. For the MSSM we find a stable vacuum when tanbeta< 1, but in this region the top Yukawa coupling blows up only slightly above the supersymmetry breaking scale. For the NMSSM, we find a stable electroweak breaking vacuum but with a chargino that is too light. Replacing the cubic singlet term in the NMSSM superpotential with a term linear in the singlet wefind a stable vacuum and viable spectrum. Most of the parameter region with correct vacua requires a large superpotential coupling, precisely what is expected in the"Fat Higgs'" model in which the superpotential is generated dynamically. We have therefore found the first viable UV complete, UV insensitive supersymmetry breaking model that solves the flavor and CP problems automatically: the Fat Higgs model with UV insensitive anomaly mediation. Moreover, the cosmological gravitino problem is naturally solved, opening up the possibility of realistic thermal leptogenesis.
Space Weather Conditions at the Time of the Galaxy 15 Spacecraft Anomaly (Invited)
NASA Astrophysics Data System (ADS)
Denig, W. F.; Green, J. C.; Wilkinson, D. C.; Rodriguez, J. V.; Singer, H. J.; Loto'Aniu, P. T.; Biesecker, D. A.; Murtagh, W.
2010-12-01
Space environmental conditions at the time of the Galaxy 15 satellite anomaly on 05 April 2010 are reviewed and discussed. Reports released by the system owner, Intelsat, indicate that at 09:48 UTC this geosynchronous communications satellite stopped responding to ground commands. The satellite manufacturer, Orbital Sciences, subsequently noted that the anomaly was the likely result of an “unusually violent solar activity that week that damaged the spacecraft’s ability to communicate with ground controllers". At the time of the anomaly, the geosynchronous satellite was located just past local midnight having recently come out of eclipse into a disturbed local space environment at GEO. Information sources contributing to an overall assessment of space weather conditions at this time include solar and interplanetary imagery and datasets, geosynchronous satellite particle and field measurements, observations from satellites in polar low-earth orbit, and ground-based magnetic observatory records. Initial analysis indicates that the Galaxy 15 anomaly occurred shortly after the start of a modest geomagnetic storm with a timely magnetic substorm that greatly perturbed the local space environment in the midnight sector. The intent of this presentation is to describe the space environmental conditions both globally and in close proximity to Galaxy 15 to facilitate ongoing spacecraft anomaly studies. Galaxy 15 (133 W) Anomaly 0948 UT on 05 April 2010
LHCb anomalies from a natural perspective
NASA Astrophysics Data System (ADS)
García, Isabel García
2017-03-01
Tension between the Standard Model (SM) and data concerning b → s processes has become apparent. Most notoriously, concerning the R K ratio, which probes lepton non-universality in b decays, and measurements involving the decays B → K ∗ μ + μ - and B s → ϕμ + μ -. Careful analysis of a wide range of b → s data shows that certain kinds of new physics can significantly ameliorate agreement with experiment. Here, we show that these b → s anomalies can be naturally accommodated in the context of Natural Scherk-Schwarz Theories of the Weak Scale — a class of models designed to address the hierarchy problem. No extra states beyond those naturally present in the theory need to be introduced in order to accommodate these anomalies, and the assumptions required regarding flavor violating couplings are very mild. Moreover, the structure of these models makes sharp predictions regarding B meson decays into final states including τ + τ - pairs, which will provide a future test of this type of theories.
An enhanced stream mining approach for network anomaly detection
NASA Astrophysics Data System (ADS)
Bellaachia, Abdelghani; Bhatt, Rajat
2005-03-01
Network anomaly detection is one of the hot topics in the market today. Currently, researchers are trying to find a way in which machines could automatically learn both normal and anomalous behavior and thus detect anomalies if and when they occur. Most important applications which could spring out of these systems is intrusion detection and spam mail detection. In this paper, the primary focus on the problem and solution of "real time" network intrusion detection although the underlying theory discussed may be used for other applications of anomaly detection (like spam detection or spy-ware detection) too. Since a machine needs a learning process on its own, data mining has been chosen as a preferred technique. The object of this paper is to present a real time clustering system; we call Enhanced Stream Mining (ESM) which could analyze packet information (headers, and data) to determine intrusions.
[Anomaly Detection of Multivariate Time Series Based on Riemannian Manifolds].
Xu, Yonghong; Hou, Xiaoying; Li Shuting; Cui, Jie
2015-06-01
Multivariate time series problems widely exist in production and life in the society. Anomaly detection has provided people with a lot of valuable information in financial, hydrological, meteorological fields, and the research areas of earthquake, video surveillance, medicine and others. In order to quickly and efficiently find exceptions in time sequence so that it can be presented in front of people in an intuitive way, we in this study combined the Riemannian manifold with statistical process control charts, based on sliding window, with a description of the covariance matrix as the time sequence, to achieve the multivariate time series of anomaly detection and its visualization. We made MA analog data flow and abnormal electrocardiogram data from MIT-BIH as experimental objects, and verified the anomaly detection method. The results showed that the method was reasonable and effective.
Developmental anomalies: Mutational consequence of mouse zygote exposure
Generoso, W.M. ); Rutledge, J.C. . Dept. of Labs.); Aronson, J. )
1989-01-01
One of the objectives of mutagenesis research in mice is to enrich our knowledge of basic mammalian biology. The practical goal is to apply this knowledge to the problems of human health. The research described here exemplifies this philosophy. The observation that certain mutagens induced high incidences of fetal anomalies and death following exposure during the zygote stage is a new phenomenon in mutagenesis and experimental embryopathy. The mechanism for the induction of zygote-derived anomalies appears to be genetic, but it is not of the conventional type. These zygote-derived anomalies resemble the large class of stillbirths and sporadic defects in humans that are of unknown etiology. The zygote research in mice presents an opportunity for studying the molecular and cellular pathogenesis of this class of defects. 12 refs., 1 fig., 3 tabs.
NASA Astrophysics Data System (ADS)
Liu, Wenjing; Xu, Liang
2016-12-01
Based on Center of Orbit Determination in Europe (CODE) global ionospheric map (GIM) data, a statistical analysis of local total electron content (TEC) anomalies before 121 low-depth (D ≤ 100 km) strong (M w ≥ 7.0) earthquakes has been made using the sliding median differential calculation method combining with a new approach of image processing technique. The results show that significant local TEC anomalies could be observed 0-6 days before 80 earthquakes, about 66.1% out of the total. The positive anomalies occur more often than negative ones. For 26 cases, both positive and negative anomalies are observed before the shock. The pre-earthquake TEC anomalies show local time recurrence for 38 earthquakes, which occur around the same local time on different days. The local time distribution of the pre-earthquake TEC anomalies mainly concentrates between 19 and 06 LT, roughly from the sunset to sunrise. Most of the pre-earthquake TEC anomalies do not locate above the epicenter but shift to the south. The pre-earthquake TEC anomalies could be extracted near the magnetic conjugate point of the epicenter for 40 events, which is 50% out of the total 80 cases with significant local TEC anomalies. In general, the signs of the anomalies around epicenter and its conjugate point are the same, but the abnormal magnitude and lasting time are not.
NASA Astrophysics Data System (ADS)
Liu, Wenjing; Xu, Liang
2017-07-01
Based on Center of Orbit Determination in Europe (CODE) global ionospheric map (GIM) data, a statistical analysis of local total electron content (TEC) anomalies before 121 low-depth ( D ≤ 100 km) strong ( M w ≥ 7.0) earthquakes has been made using the sliding median differential calculation method combining with a new approach of image processing technique. The results show that significant local TEC anomalies could be observed 0-6 days before 80 earthquakes, about 66.1% out of the total. The positive anomalies occur more often than negative ones. For 26 cases, both positive and negative anomalies are observed before the shock. The pre-earthquake TEC anomalies show local time recurrence for 38 earthquakes, which occur around the same local time on different days. The local time distribution of the pre-earthquake TEC anomalies mainly concentrates between 19 and 06 LT, roughly from the sunset to sunrise. Most of the pre-earthquake TEC anomalies do not locate above the epicenter but shift to the south. The pre-earthquake TEC anomalies could be extracted near the magnetic conjugate point of the epicenter for 40 events, which is 50% out of the total 80 cases with significant local TEC anomalies. In general, the signs of the anomalies around epicenter and its conjugate point are the same, but the abnormal magnitude and lasting time are not.
Anomaly Detection Based on Sensor Data in Petroleum Industry Applications
Martí, Luis; Sanchez-Pi, Nayat; Molina, José Manuel; Garcia, Ana Cristina Bicharra
2015-01-01
Anomaly detection is the problem of finding patterns in data that do not conform to an a priori expected behavior. This is related to the problem in which some samples are distant, in terms of a given metric, from the rest of the dataset, where these anomalous samples are indicated as outliers. Anomaly detection has recently attracted the attention of the research community, because of its relevance in real-world applications, like intrusion detection, fraud detection, fault detection and system health monitoring, among many others. Anomalies themselves can have a positive or negative nature, depending on their context and interpretation. However, in either case, it is important for decision makers to be able to detect them in order to take appropriate actions. The petroleum industry is one of the application contexts where these problems are present. The correct detection of such types of unusual information empowers the decision maker with the capacity to act on the system in order to correctly avoid, correct or react to the situations associated with them. In that application context, heavy extraction machines for pumping and generation operations, like turbomachines, are intensively monitored by hundreds of sensors each that send measurements with a high frequency for damage prevention. In this paper, we propose a combination of yet another segmentation algorithm (YASA), a novel fast and high quality segmentation algorithm, with a one-class support vector machine approach for efficient anomaly detection in turbomachines. The proposal is meant for dealing with the aforementioned task and to cope with the lack of labeled training data. As a result, we perform a series of empirical studies comparing our approach to other methods applied to benchmark problems and a real-life application related to oil platform turbomachinery anomaly detection. PMID:25633599
Anomaly detection based on sensor data in petroleum industry applications.
Martí, Luis; Sanchez-Pi, Nayat; Molina, José Manuel; Garcia, Ana Cristina Bicharra
2015-01-27
Anomaly detection is the problem of finding patterns in data that do not conform to an a priori expected behavior. This is related to the problem in which some samples are distant, in terms of a given metric, from the rest of the dataset, where these anomalous samples are indicated as outliers. Anomaly detection has recently attracted the attention of the research community, because of its relevance in real-world applications, like intrusion detection, fraud detection, fault detection and system health monitoring, among many others. Anomalies themselves can have a positive or negative nature, depending on their context and interpretation. However, in either case, it is important for decision makers to be able to detect them in order to take appropriate actions. The petroleum industry is one of the application contexts where these problems are present. The correct detection of such types of unusual information empowers the decision maker with the capacity to act on the system in order to correctly avoid, correct or react to the situations associated with them. In that application context, heavy extraction machines for pumping and generation operations, like turbomachines, are intensively monitored by hundreds of sensors each that send measurements with a high frequency for damage prevention. In this paper, we propose a combination of yet another segmentation algorithm (YASA), a novel fast and high quality segmentation algorithm, with a one-class support vector machine approach for efficient anomaly detection in turbomachines. The proposal is meant for dealing with the aforementioned task and to cope with the lack of labeled training data. As a result, we perform a series of empirical studies comparing our approach to other methods applied to benchmark problems and a real-life application related to oil platform turbomachinery anomaly detection.
Orbit determination singularities in the Doppler tracking of a planetary orbiter
NASA Technical Reports Server (NTRS)
Wood, L. J.
1985-01-01
On a number of occasions, spacecraft launched by the U.S. have been placed into orbit about the moon, Venus, or Mars. It is pointed out that, in particular, in planetary orbiter missions two-way coherent Doppler data have provided the principal data type for orbit determination applications. The present investigation is concerned with the problem of orbit determination on the basis of Doppler tracking data in the case of a spacecraft in orbit about a natural body other than the earth or the sun. Attention is given to Doppler shift associated with a planetary orbiter, orbit determination using a zeroth-order model for the Doppler shift, and orbit determination using a first-order model for the Doppler shift.
Thermal recoil force, telemetry, and the Pioneer anomaly
Toth, Viktor T.; Turyshev, Slava G.
2009-02-15
Precision navigation of spacecraft requires accurate knowledge of small forces, including the recoil force due to anisotropies of thermal radiation emitted by spacecraft systems. We develop a formalism to derive the thermal recoil force from the basic principles of radiative heat exchange and energy-momentum conservation. The thermal power emitted by the spacecraft can be computed from engineering data obtained from flight telemetry, which yields a practical approach to incorporate the thermal recoil force into precision spacecraft navigation. Alternatively, orbit determination can be used to estimate the contribution of the thermal recoil force. We apply this approach to the Pioneer anomaly using a simulated Pioneer 10 Doppler data set.
LOP- LONG-TERM ORBIT PREDICTOR
NASA Technical Reports Server (NTRS)
Kwok, J. H.
1994-01-01
The Long-Term Orbit Predictor (LOP) trajectory propagation program is a useful tool in lifetime analysis of orbiting spacecraft. LOP is suitable for studying planetary orbit missions with reconnaissance (flyby) and exploratory (mapping) trajectories. Sample data is included for a geosynchronous station drift cycle study, a Venus radar mapping strategy, a frozen orbit about Mars, and a repeat ground trace orbit. LOP uses the variation-of-parameters method in formulating the equations of motion. Terms involving the mean anomaly are removed from numerical integrations so that large step sizes, on the order of days, are possible. Consequently, LOP executes much faster than programs based on Cowell's method, such as the companion program ASAP (the Artificial Satellite Analysis Program, NPO-17522, also available through COSMIC). The program uses a force model with a gravity field of up to 21 by 21, lunisolar perturbation, drag, and solar radiation pressure. The input includes classical orbital elements (either mean or oscillating), orbital elements of the sun relative to the planet, reference time and dates, drag coefficients, gravitational constants, planet radius, rotation rate. The printed output contains the classical elements for each time step or event step, and additional orbital data such as true anomaly, eccentric anomaly, latitude, longitude, periapsis altitude, and the rate of change per day of certain elements. Selected output is additionally written to a plot file for postprocessing by the user. LOP is written in FORTRAN 77 for batch execution on IBM PC compatibles running MS-DOS with a minimum of 256K RAM. Recompiling the source requires the Lahey F77 v2.2 compiler. The LOP package includes examples that use LOTUS 1-2-3 for graphical displays, but any graphics software package should be able to handle the ASCII plot file. The program is available on two 5.25 inch 360K MS-DOS format diskettes. The program was written in 1986 and last updated in 1989. LOP is
LOP- LONG-TERM ORBIT PREDICTOR
NASA Technical Reports Server (NTRS)
Kwok, J. H.
1994-01-01
The Long-Term Orbit Predictor (LOP) trajectory propagation program is a useful tool in lifetime analysis of orbiting spacecraft. LOP is suitable for studying planetary orbit missions with reconnaissance (flyby) and exploratory (mapping) trajectories. Sample data is included for a geosynchronous station drift cycle study, a Venus radar mapping strategy, a frozen orbit about Mars, and a repeat ground trace orbit. LOP uses the variation-of-parameters method in formulating the equations of motion. Terms involving the mean anomaly are removed from numerical integrations so that large step sizes, on the order of days, are possible. Consequently, LOP executes much faster than programs based on Cowell's method, such as the companion program ASAP (the Artificial Satellite Analysis Program, NPO-17522, also available through COSMIC). The program uses a force model with a gravity field of up to 21 by 21, lunisolar perturbation, drag, and solar radiation pressure. The input includes classical orbital elements (either mean or oscillating), orbital elements of the sun relative to the planet, reference time and dates, drag coefficients, gravitational constants, planet radius, rotation rate. The printed output contains the classical elements for each time step or event step, and additional orbital data such as true anomaly, eccentric anomaly, latitude, longitude, periapsis altitude, and the rate of change per day of certain elements. Selected output is additionally written to a plot file for postprocessing by the user. LOP is written in FORTRAN 77 for batch execution on IBM PC compatibles running MS-DOS with a minimum of 256K RAM. Recompiling the source requires the Lahey F77 v2.2 compiler. The LOP package includes examples that use LOTUS 1-2-3 for graphical displays, but any graphics software package should be able to handle the ASCII plot file. The program is available on two 5.25 inch 360K MS-DOS format diskettes. The program was written in 1986 and last updated in 1989. LOP is
TERRA Battery Thermal Control Anomaly - Simulation and Corrective Actions
NASA Technical Reports Server (NTRS)
Grob, Eric W.
2010-01-01
The TERRA spacecraft was launched in December 1999 from Vandenberg Air Force Base, becoming the flagship of NASA's Earth Observing System program to gather data on how the planet's processes create climate. Originally planned as a 5 year mission, it still provides valuable science data after nearly 10 years on orbit. On October 13th, 2009 at 16:23z following a routine inclination maneuver, TERRA experienced a battery cell failure and a simultaneous failure of several battery heater control circuits used to maintain cell temperatures and gradients within the battery. With several cells nearing the minimum survival temperature, preventing the electrolyte from freezing was the first priority. After several reset attempts and power cycling of the control electronics failed to reestablish control authority on the primary side of the controller, it was switched to the redundant side, but anomalous performance again prevented full heater control of the battery cells. As the investigation into the cause of the anomaly and corrective action continued, a battery thermal model was developed to be used in determining the control ability remaining and to simulate and assess corrective actions. Although no thermal model or detailed reference data of the battery was available, sufficient information was found to allow a simplified model to be constructed, correlated against pre-anomaly telemetry, and used to simulate the thermal behavior at several points after the anomaly. It was then used to simulate subsequent corrective actions to assess their impact on cell temperatures. This paper describes the rapid development of this thermal model, including correlation to flight data before and after the anomaly., along with a comparative assessment of the analysis results used to interpret the telemetry to determine the extent of damage to the thermal control hardware, with near-term corrective actions and long-term operations plan to overcome the anomaly.
Could the Pioneer anomaly have a gravitational origin?
Tangen, Kjell
2007-08-15
If the Pioneer anomaly has a gravitational origin, it would, according to the equivalence principle, distort the motions of the planets in the Solar System. Since no anomalous motion of the planets has been detected, it is generally believed that the Pioneer anomaly can not originate from a gravitational source in the Solar System. However, this conclusion becomes less obvious when considering models that either imply modifications to gravity over long distances or gravitational sources localized to the outer Solar System, given the uncertainty in the orbital parameters of the outer planets. Following the general assumption that the Pioneer spacecraft move geodesically in a spherically symmetric space-time metric, we derive the metric disturbance that is needed in order to account for the Pioneer anomaly. We then analyze the residual effects on the astronomical observables of the three outer planets that would arise from this metric disturbance, given an arbitrary metric theory of gravity. Providing a method for comparing the computed residuals with actual residuals, our results imply that the presence of a perturbation to the gravitational field necessary to induce the Pioneer anomaly is in conflict with available data for the planets Uranus and Pluto, but not for Neptune. We therefore conclude that the motion of the Pioneer spacecraft must be nongeodesic. Since our results are model-independent within the class of metric theories of gravity, they can be applied to rule out any model of the Pioneer anomaly that implies that the Pioneer spacecraft move geodesically in a perturbed space-time metric, regardless of the origin of this metric disturbance.
Space Telescope Fine Guidance Sensor Bearing Anomaly
NASA Technical Reports Server (NTRS)
Loewenthal, S.; Esper, J.; Pan, J.; Decker, J.
1996-01-01
Early in 1993, a servo motor within one of three Fine Guidance Sensors (FGS) aboard the Hubble Space Telescope (HST) reached stall torque levels on several occasions. Little time was left to plan replacement during the first servicing mission, scheduled at the end of '93. Accelerated bearing life tests confirmed that a small angle rocking motion, known as Coarse Track (CT), accelerated bearing degradation. Saturation torque levels were reached after approximately 20 million test cycles, similar to the flight bearings. Reduction in CT operation, implemented in flight software, extended FGS life well beyond the first servicing mission. However in recent years, bearing torques have resumed upward trends and together with a second, recent bearing torque anomaly has necessitated a scheduled FGS replacement during the upcoming second servicing mission in '97. The results from two series of life tests to quantify FGS bearing remaining life, discussion of bearing on-orbit performance, and future plans to service the FGS servos are presented in this paper.
Impact structures seen by magnetic anomaly maps
NASA Astrophysics Data System (ADS)
Isac, Anca; Mandea, Mioara; Purucker, Michael
2010-05-01
The terrestrial planets are open systems and impacting was and it can be a very important process for the planetary evolution. Earth has an active dynamo, however neither Moon and Mars have an active one. The magnetized rocks in their crusts suggest that in their earlier history, dynamos may have been operating in the metallic core of these bodies. Because of its large iron core the possibility of an ancient operating Martian dynamo is more likely, but the small lunar core and the age of the magnetized lunar rocks, have brought in debate a possible dynamo origin of lunar magnetism. The magnetic fields have been observed at global scale only for the Earth, Mars and Moon, and very conspicuous magnetic anomalies have been estimated for these three bodies. For this study, we firstly have used the largest impact structures for the Earth, Mars and Moon. Thereafter, we have extended our work to smaller martian and lunar impact craters (30 km diameters), cataloging them in order to obtain information about the impact crater magnetic signatures, positions, shapes and diameters. We superposed ULCN 2005 or Kaguya 2008 gridded topography on Lunar Prospector magnetic map for Moon and Mars Orbiting Laser Altimeter (MOLA) gridded data on Mars Global Surveyor magnetic data for Mars, as a systematic search for Quasi-Circular Depressions. The results obtain for Mars and Moon, obtained for a larger number of craters allow us to have a statistical view on the indicated parameters.
Probing the flyby anomaly with the future STE-QUEST mission
NASA Astrophysics Data System (ADS)
Páramos, Jorge; Hechenblaikner, G.
2013-05-01
In this study, we demonstrate that the flyby anomaly, an unexpected acceleration detected in some of the gravitational assists of the Galileo, NEAR, Cassini and Rosetta spacecraft, could be probed by accurate orbital tracking available in the proposed Space-Time Explorer and Quantum Equivalence Principle Space Test (STE-QUEST); following a recent work, we focus on the similarity between a hyperbolic flyby and the perigee passage in a highly elliptic orbit of the latter, as well as its Global Navigation Satellite System precise orbital determination capabilities.
Timing of Increasing Electron Counts From Geosynchronous Orbit to Low Earth Orbit
2005-01-01
space mission operations. The Compact Environment Anomaly Sensors (CEASE) onboard the DSP-21 and TSX-5 satellites collected dosimeter data of electrons > 1.2 MeV and protons > 25 MeV. The orbits of the satellites and the particle detection of CEASE provided an opportunity to sample the high energy electron population fluxes at GEO and LEO during electron events. The high energy electron CEASE data was extracted from DSP-21 and TSX-5 when each satellite crossed an approximate geosynchronous L-Shell range (L=6.5-6.7). Onsets of electron events at each orbit were determined
Scalar magnetic anomaly maps of Earth derived from POGO and Magsat data
NASA Technical Reports Server (NTRS)
Arkani-Hamed, Jafar; Langel, Robert A.; Purucker, Mike
1994-01-01
A new Polar Orbit Geophysical Observatory (POGO) scalar magnetic anomaly map at 400 km altitude is presented which consists of spherical harmonics of degree 15-60. On the basis of the common features of this map with two new Magsat anomaly maps, dawn and dusk, two scalar magnetic anomaly maps of the Earth are presented using two selection criteria with different levels of stringency. These selection criteria suppress the noncrustal components of the original maps by different amounts. The more stringent selection criteria seek to eliminate as much contamination as possible, at the expense of suppressing some anomaly signal. This map is represented by spherical harmonics of degree 15-60. The less stringent selection criteria seek to retain as much crustal signal as possible, at the expense of also retaining some contaminating fields. This map is represented by spherical harmonics of degree 15-65. The resulting two maps are highly correlated with degree correlation coefficients greater than 0.8.
Echocardiographic assessment of Ebstein's anomaly.
Booker, Oscar J; Nanda, Navin C
2015-01-01
Ebstein's anomaly is a complex congenital lesion which primarily involves the tricuspid valve. The tricuspid leaflets are tethered to varying degrees to the right ventricular free wall and the ventricular septum often resulting in significant tricuspid regurgitation and a small functioning right ventricular chamber. Although the septal leaflet originates normally at the right atrioventricular junction, the proximal portion is often completely tethered to the ventricular septum resulting in a misconception and erroneous statements in many publications that its attachment is apically displaced. Although two-dimensional echocardiography represents the primary modality for the diagnosis of this anomaly, three-dimensional echocardiography provides incremental value in characterizing the extent and severity of tethering of individual tricuspid valve leaflets. This information is useful in surgical decision making whether to repair or replace the tricuspid valve.
Four Decades of Hyperfine Anomalies
NASA Astrophysics Data System (ADS)
Gustavsson, Martin G. H.; Mårtensson-Pendrill, Ann-Marie
Isotopic differences in the distribution of nuclear charge and magnetization give rise to "hyperfine structure anomalies" which were observed already in the 1950s. More recently, the distribution of nuclear magnetization has been found to complicate the interpretation of the measured hyperfine splittings in highly charged hydrogen-like ions. In this paper, results of numerical calculations for a few hydrogen-like systems (133Cs, 165Ho, 185,187Re and 209Bi) of current experimental interest are presented in terms of moments of the nuclear charge and magnetization distribution, thereby displaying directly the sensitivity and emphasizing the need for a better understanding of nuclear wavefunctions. In addition, we also present results of many-body perturbation theory calculations for Cs hyperfine anomalies, in connection with experiments planned at ISOLDE.
[Ectopia cordis and cardiac anomalies].
Cabrera, Alberto; Rodrigo, David; Luis, María Teresa; Pastor, Esteban; Galdeano, José Miguel; Esteban, Susana
2002-11-01
Ectopia cordis is a rare disease that occurs in 5.5 to 7.9 per million live births. Only 267 cases had been reported as of 2001, most (95%) associated with other cardiac anomalies. We studied the cardiac malformations associated in 6 patients with ectopia cordis. Depending on where the defect was located, the cases of ectopia were classified into four groups: cervical, thoracic, thoraco-abdominal, and abdominal. All 6 patients died before the third day of life, 4 during delivery. Three of the patients were included in the thoracic group, whereas the other 3 belonged to the thoraco-abdominal group. All the patients had associated ventricular septal defects, 3 double-outlet right ventricle (50%) and the rest (50%) tetralogy of Fallot-pulmonary atresia. Two patients with double-outlet right ventricle presented mitral-valve pathology, a parachute valve and an atresic mitral valve. None of these cardiac anomalies have been reported to date.
Congenital pancreatic anomalies, variants, and conditions.
Alexander, Lauren F
2012-05-01
Understanding pancreatic development and the congenital anomalies and variants that result from alterations in normal development allows for better recognition of these anomalies at diagnostic imaging. This article reviews normal pancreatic embryology and anatomy, and the appearance of the more common developmental anomalies and ductal variants, with emphasis on computed tomography and magnetic resonance imaging. Common mimics of masses are also covered.
Syndromes and anomalies associated with cleft
Venkatesh, R.
2009-01-01
Orofacial clefts are one of the commonest birth defects, and may be associated with other congenital anomalies. The majority of these orofacial clefts are nonsyndromic. A significant percentage of these clefts both syndromic and non-syndromic may have associated anomalies. Apart from reviewing other studies, this article also analyses a study of associated anomalies from a tertiary cleft centre in India. PMID:19884681
Five important power line component anomalies
NASA Astrophysics Data System (ADS)
Strmiska, Richard G.
2000-03-01
During routine infrared surveys of switchyard, substation, distribution components and underground cable installations, several important anomalies have been identified. Five are reported on in this paper: (1) Moisture intrusion into high voltage polymer insulators; (2) Improper installation of a three phase service transformer set; (3) Improper tightening of a bushing connection; (4) Current transformer polyurethane coating encasement failure; (5) Underground cable and fuse enclosure insulator failure. In the first case the extremes of Florida weather, heat, humidity and moisture, contributed to the failure. In all cases, either improved manufacturing design or installation procedures could have prevented these problems. In addition to using infrared thermography as a survey tool, it is highly recommended to be used as a design and installation, baseline-checking tool.
Phase anomalies in Bessel-Gauss beams.
Kim, Myun-Sik; Scharf, Toralf; Assafrao, Alberto da Costa; Rockstuhl, Carsten; Pereira, Silvania F; Urbach, H Paul; Herzig, Hans Peter
2012-12-17
Bessel-Gauss beams are known as non-diffracting beams. They can be obtained by focusing an annularly shaped collimated laser beam. Here, we report for the first time on the direct measurement of the phase evolution of such beams by relying on longitudinal-differential interferometry. We found that the characteristics of Bessel-Gauss beams cause a continuously increasing phase anomaly in the spatial domain where such beams do not diverge, i.e. there is a larger phase advance of the beam when compared to a referential plane wave. Simulations are in excellent agreement with measurements. We also provide an analytical treatment of the problem that matches both experimental and numerical results and provides an intuitive explanation.
A Statistical Detection of an Anomaly from a Few Noisy Tomographic Projections
NASA Astrophysics Data System (ADS)
Fillatre, Lionel; Nikiforov, Igor
2005-12-01
The problem of detecting an anomaly/target from a very limited number of noisy tomographic projections is addressed from the statistical point of view. The imaged object is composed of an environment, considered as a nuisance parameter, with a possibly hidden anomaly/target. The GLR test is used to solve the problem. When the projection linearly depends on the nuisance parameters, the GLR test coincides with an optimal statistical invariant test.
On estimating gravity anomalies from gradiometer data. [by numerical analysis
NASA Technical Reports Server (NTRS)
Argentiero, P.; Garza-Robles, R.
1976-01-01
The Gravsat-gradiometer mission involves flying a gradiometer on a gravity satellite (Gravsat) which is in a low, polar, and circular orbit. Results are presented of a numerical simulation of the mission which demonstrates that, if the satellite is in a 250-km orbit, 3- and 5-degree gravity anomalies may be estimated with accuracies of 0.03 and 0.01 mm/square second (3 and 1 mgal), respectively. At an altitude of 350 km, the results are 0.07 and 0.025 mm.square second (7 and 2.5 mgal), respectively. These results assume a rotating type gradiometer with a 0.1 -etvos unit accuracy. The results can readily be scaled to reflect another accuracy level.
Processing MAGSAT data for comparison with geoid anomalies
NASA Technical Reports Server (NTRS)
Bowin, C. O. (Principal Investigator)
1982-01-01
A digital data library of MAGSAT data consisting of 1,615,636 measurements from the quiet data set, is geographically sorted, and allows rapid analysis and processing of all the quiet magnetic data about any selected location. Because this library of MAGSAT data is compatible with existing gravity and geoid data library processing and display system software, correlations between MAGSAT, surface gravity, GEOS-3 radar altimeter geoid and bathymetric data sets can be conveniently detected and analyzed. Polynomial trends from each half-orbit were removed as an effective way of estimating and removing ring current effects following estimation of the core field contribution. It was found that a third order polynomial is the lowest polynomial order that appears to provide the best consistency of residual anomalies between coincident orbits.
Fast Anomaly Discovery Given Duplicates
2012-12-01
skipping the computations for duplicate points in SN(ui) that have ci larger than k, the runtime complexity is enhanced significantly. That is, in...Fast anomaly discovery given duplicates Jay-Yoon Lee, U Kang, Danai Koutra, Christos Faloutsos Dec 2012 CMU-CS-12-146 School of Computer Science...ES) Carnegie Mellon University,School of Computer Science,Pittsburgh,PA,15213 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING
Isotopic anomalies in extraterrestrial grains.
Ireland, T R
1996-03-01
Isotopic compositions are referred to as anomalous if the isotopic ratios measured cannot be related to the terrestrial (solar) composition of a given element. While small effects close to the resolution of mass spectrometric techniques can have ambiguous origins, the discovery of large isotopic anomalies in inclusions and grains from primitive meteorites suggests that material from distinct sites of stellar nucleosynthesis has been preserved. Refractory inclusions, which are predominantly composed of the refractory oxides of Al, Ca, Ti, and Mg, in chondritic meteorites commonly have excesses in the heaviest isotopes of Ca, Ti, and Cr which are inferred to have been produced in a supernova. Refractory inclusions also contain excess 26Mg from short lived 26Al decay. However, despite the isotopic anomalies indicating the preservation of distinct nucleosynthetic sites, refractory inclusions have been processed in the solar system and are not interstellar grains. Carbon (graphite and diamond) and silicon carbide grains from the same meteorites also have large isotopic anomalies but these phases are not stable in the oxidized solar nebula which suggests that they are presolar and formed in the circumstellar atmospheres of carbon-rich stars. Diamond has a characteristic signature enriched in the lightest and heaviest isotopes of Xe, and graphite shows a wide range in C isotopic compositions. SiC commonly has C and N isotopic signatures which are characteristic of H-burning in the C-N-O cycle in low-mass stars. Heavier elements such as Si, Ti, Xe, Ba, and Nd, carry an isotopic signature of the s-process. A minor population of SiC (known as Grains X, ca. 1%) are distinct in having decay products of short lived isotopes 26Al (now 26Mg), 44Ti (now 44Ca), and 49V (now 49Ti), as well as 28Si excesses which are characteristic of supernova nucleosynthesis. The preservation of these isotopic anomalies allows the examination of detailed nucleosynthetic pathways in stars.
Shadowing Lemma and chaotic orbit determination
NASA Astrophysics Data System (ADS)
Spoto, Federica; Milani, Andrea
2016-03-01
Orbit determination is possible for a chaotic orbit of a dynamical system, given a finite set of observations, provided the initial conditions are at the central time. The Shadowing Lemma (Anosov 1967; Bowen in J Differ Equ 18:333-356, 1975) can be seen as a way to connect the orbit obtained using the observations with a real trajectory. An orbit is a shadowing of the trajectory if it stays close to the real trajectory for some amount of time. In a simple discrete model, the standard map, we tackle the problem of chaotic orbit determination when observations extend beyond the predictability horizon. If the orbit is hyperbolic, a shadowing orbit is computed by the least squares orbit determination. We test both the convergence of the orbit determination iterative procedure and the behaviour of the uncertainties as a function of the maximum number of map iterations observed. When the initial conditions belong to a chaotic orbit, the orbit determination is made impossible by numerical instability beyond a computability horizon, which can be approximately predicted by a simple formula. Moreover, the uncertainty of the results is sharply increased if a dynamical parameter is added to the initial conditions as parameter to be estimated. The Shadowing Lemma does not dictate what the asymptotic behaviour of the uncertainties should be. These phenomena have significant implications, which remain to be studied, in practical problems of orbit determination involving chaos, such as the chaotic rotation state of a celestial body and a chaotic orbit of a planet-crossing asteroid undergoing many close approaches.
Entanglement entropy and anomaly inflow
NASA Astrophysics Data System (ADS)
Hughes, Taylor L.; Leigh, Robert G.; Parrikar, Onkar; Ramamurthy, Srinidhi T.
2016-03-01
We study entanglement entropy for parity-violating (time-reversal breaking) quantum field theories on R1 ,2 in the presence of a domain wall between two distinct parity-odd phases. The domain wall hosts a 1 +1 -dimensional conformal field theory (CFT) with nontrivial chiral central charge. Such a CFT possesses gravitational anomalies. It has been shown recently that, as a consequence, its intrinsic entanglement entropy is sensitive to Lorentz boosts around the entangling surface. Here, we show using various methods that the entanglement entropy of the three-dimensional bulk theory is also sensitive to such boosts owing to parity-violating effects, and that the bulk response to a Lorentz boost precisely cancels the contribution coming from the domain wall CFT. We argue that this can naturally be interpreted as entanglement inflow (i.e., inflow of entanglement entropy analogous to the familiar Callan-Harvey effect) between the bulk and the domain-wall, mediated by the low-lying states in the entanglement spectrum. These results can be generally applied to 2 +1 -d topological phases of matter that have edge theories with gravitational anomalies, and provide a precise connection between the gravitational anomaly of the physical edge theory and the low-lying spectrum of the entanglement Hamiltonian.
Surgical treatment of cloacal anomalies.
Krstic, Z D; Lukac, M; Lukac, R; Smoljanic, Z; Vukadinovic, V; Varinac, D
2001-05-01
From 1989-1998 14 patients were treated with cloacal anomalies: 5 typical cloacas (PC), 5 posterior cloacas, and 4 cloacal exstrophies (CE); 12 underwent surgery. Four typical cloacas were resolved with posterior sagittal anorectovagino-urethroplasty (PSARVUP), whereas in the 5th total urogenital mobilization (TUM) was used. Three PCs were managed with transanorectal TUM and 2 with anterior TUM without opening the anal canal and rectum (without a protective colostomy). Two CEs were treated with atypical procedures. Two patients with CE died without surgery and 2 died after surgery due to complex associated anomalies. During postoperative follow-up of 1-8 years, 5 children had voluntary bowel movements and no soiling while the others had soiling with or without enemas; 1 had stress incontinence; 3 were on clean intermittent catheterization due to neurogenic bladder and were dry. PSARVUP provides a satisfactory result if there is no sacral anomaly. TUM makes this operation easier to perform. In patients with a PC it is sometimes possible using TUM to separate the urinary from the genital tract and remove the accessory urethra without opening the anus and rectum.
Anomalies, conformal manifolds, and spheres
Gomis, Jaume; Hsin, Po-Shen; Komargodski, Zohar; Schwimmer, Adam; Seiberg, Nathan; Theisen, Stefan
2016-03-04
The two-point function of exactly marginal operators leads to a universal contribution to the trace anomaly in even dimensions. We study aspects of this trace anomaly, emphasizing its interpretation as a sigma model, whose target space $M$ is the space of conformal field theories (a.k.a. the conformal manifold). When the underlying quantum field theory is supersymmetric, this sigma model has to be appropriately supersymmetrized. As examples, we consider in some detail $N$ = (2; 2) and $N$ = (0; 2) supersymmetric theories in d = 2 and $N$ = 2 supersymmetric theories in d = 4. This reasoning leads to new information about the conformal manifolds of these theories, for example, we show that the manifold is K ahler-Hodge and we further argue that it has vanishing K ahler class. For $N$ = (2; 2) theories in d = 2 and N = 2 theories in d = 4 we also show that the relation between the sphere partition function and the K ahler potential of $M$ follows immediately from the appropriate sigma models that we construct. Ultimately, along the way we find several examples of potential trace anomalies that obey the Wess-Zumino consistency conditions, but can be ruled out by a more detailed analysis.
Anomalies, conformal manifolds, and spheres
Gomis, Jaume; Hsin, Po-Shen; Komargodski, Zohar; ...
2016-03-04
The two-point function of exactly marginal operators leads to a universal contribution to the trace anomaly in even dimensions. We study aspects of this trace anomaly, emphasizing its interpretation as a sigma model, whose target space $M$ is the space of conformal field theories (a.k.a. the conformal manifold). When the underlying quantum field theory is supersymmetric, this sigma model has to be appropriately supersymmetrized. As examples, we consider in some detail $N$ = (2; 2) and $N$ = (0; 2) supersymmetric theories in d = 2 and $N$ = 2 supersymmetric theories in d = 4. This reasoning leads tomore » new information about the conformal manifolds of these theories, for example, we show that the manifold is K ahler-Hodge and we further argue that it has vanishing K ahler class. For $N$ = (2; 2) theories in d = 2 and N = 2 theories in d = 4 we also show that the relation between the sphere partition function and the K ahler potential of $M$ follows immediately from the appropriate sigma models that we construct. Ultimately, along the way we find several examples of potential trace anomalies that obey the Wess-Zumino consistency conditions, but can be ruled out by a more detailed analysis.« less
PREDICT: Satellite tracking and orbital prediction
NASA Astrophysics Data System (ADS)
Magliacane, John A.
2011-12-01
PREDICT is an open-source, multi-user satellite tracking and orbital prediction program written under the Linux operating system. PREDICT provides real-time satellite tracking and orbital prediction information to users and client applications through: the system console the command line a network socket the generation of audio speechData such as a spacecraft's sub-satellite point, azimuth and elevation headings, Doppler shift, path loss, slant range, orbital altitude, orbital velocity, footprint diameter, orbital phase (mean anomaly), squint angle, eclipse depth, the time and date of the next AOS (or LOS of the current pass), orbit number, and sunlight and visibility information are provided on a real-time basis. PREDICT can also track (or predict the position of) the Sun and Moon. PREDICT has the ability to control AZ/EL antenna rotators to maintain accurate orientation in the direction of communication satellites. As an aid in locating and tracking satellites through optical means, PREDICT can articulate tracking coordinates and visibility information as plain speech.
[Introduction to orbital surgery (author's transl)].
Babel, J
1981-04-01
After a revision of orbital anatomy, the following problems are exposed: necessary examinations to localize a tumoral invasion, interest of biopsy and its limits, determination of the type of treatment and description of surgical approaches, if surgery is decided.