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1

On initial orbit determination  

NASA Technical Reports Server (NTRS)

The classical methods of initial orbit determination are brought together within a larger viewpoint. This new synthesis stresses that all such techniques follow one of three approaches. Either they seek to compute the orbital element set, or its equivalent, by attacking the differential equations of motion (Laplace), the first integrals of the equations of motion (Taff), or the solution itself (Gauss). The particular technique pursued within a given type of approach should depend upon the nature of the observational data, the amount of a priori information one is willing to presume, and the object of the exercise. This might be a binary star system, a moon, a minor planet, or an artificial satellite. The efficacy of some algorithms for each approach is discussed briefly. Unfortunately, none of them work very well. Extensions of these techniques to radars or laser radars are trivial and have provided no new insights into the overall problem.

Taff, L. G.

1984-01-01

2

Algorithms for Autonomous GPS Orbit Determination and Formation Flying: Investigation of Initialization Approaches and Orbit Determination for HEO  

NASA Technical Reports Server (NTRS)

This report summarizes the efforts to date in processing GPS measurements in High Earth Orbit (HEO) applications by the Colorado Center for Astrodynamics Research (CCAR). Two specific projects were conducted; initialization of the orbit propagation software, GEODE, using nominal orbital elements for the IMEX orbit, and processing of actual and simulated GPS data from the AMSAT satellite using a Doppler-only batch filter. CCAR has investigated a number of approaches for initialization of the GEODE orbit estimator with little a priori information. This document describes a batch solution approach that uses pseudorange or Doppler measurements collected over an orbital arc to compute an epoch state estimate. The algorithm is based on limited orbital element knowledge from which a coarse estimate of satellite position and velocity can be determined and used to initialize GEODE. This algorithm assumes knowledge of nominal orbital elements, (a, e, i, omega, omega) and uses a search on time of perigee passage (tau(sub p)) to estimate the host satellite position within the orbit and the approximate receiver clock bias. Results of the method are shown for a simulation including large orbital uncertainties and measurement errors. In addition, CCAR has attempted to process GPS data from the AMSAT satellite to obtain an initial estimation of the orbit. Limited GPS data have been received to date, with few satellites tracked and no computed point solutions. Unknown variables in the received data have made computations of a precise orbit using the recovered pseudorange difficult. This document describes the Doppler-only batch approach used to compute the AMSAT orbit. Both actual flight data from AMSAT, and simulated data generated using the Satellite Tool Kit and Goddard Space Flight Center's Flight Simulator, were processed. Results for each case and conclusion are presented.

Axelrad, Penina; Speed, Eden; Leitner, Jesse A. (Technical Monitor)

2002-01-01

3

The resurrection of Laplace's method of initial orbit determination  

NASA Astrophysics Data System (ADS)

This report deals with a number of interrelated topics. The common thread is Laplace's method of initial orbit determination based on passively acquired optical data. We discuss this method's principal competitor (that of Gauss), the difficulties of Gauss's technique, and the traditional reasons the Gaussian method is preferred to the Laplacian. We reject this hegemony for a variety of reasons and concentrate on Laplace's method in an era of a surfeit of high quality data. This leads us into a discussion of data smoothing. Once one leaves the raw observatorial data the possibility of combining observations from multiple observers comes to mind and hence the determination of parallax by trigonometrical means. All of this may be applied to two different classes of objects-astroids and artificial satellites. Our immediate interests are in fast moving asteroids (greater than 0.5/day or an abnormally fast ecliptic latitude rate) and high altitude artificial satellites (P greater than 6h). In both instances it is the high inclination and high eccentricity subset which is of special concern.

Taff, L. G.

1983-01-01

4

Short-Arc Correlation and Initial Orbit Determination For Space-Based Observations  

NASA Astrophysics Data System (ADS)

Initial orbit determination (IOD) of space debris is an important segment of space situational awareness and is often coupled with the problem of track correlation, since in order to determine the orbit of an observed object, multiple observations must be combined. It is generally uncertain, however, whether two arbitrary tracks are of the same object. Recently, Fujimoto and Scheeres have proposed a novel and rigorous track correlation and IOD technique where each observation is assigned an “admissible region” in state space based on some physical constraints. The relationship of two observations is then determined by finding whether these regions intersect via Bayes’ rule. In this paper, we propose a new application of this method to space-based observations. Preliminary results show robustness to classically singular geometries, such as GEO-on-GEO observations. Admissible regions were first proposed by Milani et al. for heliocentric orbits, and Tommei et al. expanded this concept to Earth orbiting objects. Maruskin et al. was first to introduce the concept of intersecting multiple admissible regions to correlate tracks and obtain an initial orbit estimate, albeit the correlation was conducted in 2-dimensional subspaces of the state space. Fujimoto and Scheeres fully developed ways of characterizing intersections of admissible regions in the full 6-dimensional state space. They showed through topological arguments that a positive correlation also simultaneously provides an initial orbit estimate. A method of linearly mapping admissible regions to the state space was introduced in order to improve computational turn-around, and was validated with a series of numerical tests. For space-based observations, the observation location vector, previously assumed to be Earth-fixed, is now allowed to propagate under two-body dynamics. Several technical challenges arise when we make this change. First, the admissible region spans over a larger region in the state space, making the correlation process more computationally intensive. Second, a modification must be made to the correlation process as the observer's state is always a valid solution. That is, any admissible region map from a space-based observation will intersect with any other map from the same observing satellite at the observing satellite's state. This problem is circumvented by automatically refining the state space discretization and throwing away solutions near the observing satellite's state. Numerical examples for several observation scenarios are discussed in this paper, including LEO-on-GEO and GEO-on-GEO observations. The LEO satellite is in a circular sun-synchronous orbit at 630 km altitude, much like the SBSS System. For existing IOD techniques there are known observation geometries that experience singularities such as the GEO-on-GEO case. Preliminary results show that our method does not suffer such singularities for the GEO-on-GEO observation scenario. This outcome is most likely due to the fact that we are combining 2 observations for a total of 8 observable variables, instead of the minimum 6, to obtain an initial orbit estimate. We believe this additional information removes the singularity from the problem.

Fujimoto, K.; Scheeres, D.

2011-09-01

5

A Comprehensive Comparison Between Angles-Only Initial Orbit Determination Techniques  

E-print Network

the error have been proposed previously. Unfortunately, many of these methods can overwhelm the analyst with data. A new method is used here that has been shown in previous research by the author. The orbit error is here quantified by two new general orbit...

Schaeperkoetter, Andrew Vernon

2012-02-14

6

A method of initial orbit determination from three or more observations on a short arc. (Russian Title: ????? ??????????? ?????????????? ?????? ?? ???? ? ????? ??????????? ?? ???????? ????)  

NASA Astrophysics Data System (ADS)

A new method is suggested for computing the initial orbit of a small celestial body from its three or more pairs of angular measurements at three times. The method is based on using the approach that we previously developed for constructing the intermediate orbit from minimal number of observations. This intermediate orbit allows for most of the perturbations in the motion of the body under study. The method proposed uses the Herget's algorithmic scheme that makes it possible to involve additional observations as well. The methodical error of orbit computation by the proposed method is two orders smaller than the corresponding error of the Herget's approach based on the construction of the unperturbed Keplerian orbit. The new method is especially efficient if applied to high-accuracy observational data covering short orbital arcs.

Shefer, V. A.

2010-12-01

7

Satellite orbit determination  

NASA Technical Reports Server (NTRS)

A historic account of the activities of the Satellite OD Group during the MM'71 mission is given along with an assessment of the accuracy of the determined orbit of the Mariner 9 spacecraft. Preflight study results are reviewed, and the major error sources described. Tracking and data fitting strategy actually used in the real time operations is itemized, and Deep Space Network data available for orbit fitting during the mission and the auxiliary information used by the navigation team are described. A detailed orbit fitting history of the first four revolutions of the satellite orbit of Mariner 9 is presented, with emphasis on the convergence problems and the delivered solution for the first orbit trim maneuver. Also included are a solution accuracy summary, the history of the spacecraft orbit osculating elements, the results of verifying the radio solutions with TV imaging data, and a summary of the normal points generated for the relativity experiment.

Jordan, J. F.; Boggs, D. H.; Born, G. H.; Christensen, E. J.; Ferrari, A. J.; Green, D. W.; Hylkema, R. K.; Mohan, S. N.; Reinbold, S. J.; Sievers, G. L.

1973-01-01

8

Ulysses orbit determination  

NASA Astrophysics Data System (ADS)

The Ulysses mission ESA spacecraft with ESA and NASA experiments explores the polar regions of the sun by sending a spacecraft on a trajectory out of the ecliptic after a Jupiter flyby. After correcting for launch errors and refining the aimpoint, orbit determination results show the change and general improvement in the Jupiter arrival point. Orbit determination results are further discussed, and future plans are mentioned.

Gordon, H. J.; Luthey, J. L.; McElrath, T. P.; Menon, P. R.

1992-08-01

9

Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis  

NASA Technical Reports Server (NTRS)

Results from operational OD produced by the NASA Goddard Flight Dynamics Facility for the LRO nominal and extended mission are presented. During the LRO nominal mission, when LRO flew in a low circular orbit, orbit determination requirements were met nearly 100% of the time. When the extended mission began, LRO returned to a more elliptical frozen orbit where gravity and other modeling errors caused numerous violations of mission accuracy requirements. Prediction accuracy is particularly challenged during periods when LRO is in full-Sun. A series of improvements to LRO orbit determination are presented, including implementation of new lunar gravity models, improved spacecraft solar radiation pressure modeling using a dynamic multi-plate area model, a shorter orbit determination arc length, and a constrained plane method for estimation. The analysis presented in this paper shows that updated lunar gravity models improved accuracy in the frozen orbit, and a multiplate dynamic area model improves prediction accuracy during full-Sun orbit periods. Implementation of a 36-hour tracking data arc and plane constraints during edge-on orbit geometry also provide benefits. A comparison of the operational solutions to precision orbit determination solutions shows agreement on a 100- to 250-meter level in definitive accuracy.

Slojkowski, Steven E.

2014-01-01

10

Interplanetary orbit determination  

NASA Technical Reports Server (NTRS)

The logistical aspects of orbit determination (OD) in the interplanetary phase of the Mariner Mars 1971 mission are described and the working arrangements for the OD personnel, both within the Navigation Team and with outside groups are given. Various types of data used in the OD process are presented along with sources of the data. Functional descriptions of the individual elements of the OD software and brief sketches of their modes of operation are provided.

Zielenbach, J. W.; Acton, C. H.; Born, G. H.; Breckenridge, W. G.; Chao, C. C.; Duxbury, T. C.; Green, D. W.; Jerath, N.; Jordan, J. F.; Mottinger, N. A.

1973-01-01

11

Orbit Determination Toolbox  

NASA Technical Reports Server (NTRS)

The Orbit Determination Toolbox is an orbit determination (OD) analysis tool based on MATLAB and Java that provides a flexible way to do early mission analysis. The toolbox is primarily intended for advanced mission analysis such as might be performed in concept exploration, proposal, early design phase, or rapid design center environments. The emphasis is on flexibility, but it has enough fidelity to produce credible results. Insight into all flight dynamics source code is provided. MATLAB is the primary user interface and is used for piecing together measurement and dynamic models. The Java Astrodynamics Toolbox is used as an engine for things that might be slow or inefficient in MATLAB, such as high-fidelity trajectory propagation, lunar and planetary ephemeris look-ups, precession, nutation, polar motion calculations, ephemeris file parsing, and the like. The primary analysis functions are sequential filter/smoother and batch least-squares commands that incorporate Monte-Carlo data simulation, linear covariance analysis, measurement processing, and plotting capabilities at the generic level. These functions have a user interface that is based on that of the MATLAB ODE suite. To perform a specific analysis, users write MATLAB functions that implement truth and design system models. The user provides his or her models as inputs to the filter commands. The software provides a capability to publish and subscribe to a software bus that is compliant with the NASA Goddard Mission Services Evolution Center (GMSEC) standards, to exchange data with other flight dynamics tools to simplify the flight dynamics design cycle. Using the publish and subscribe approach allows for analysts in a rapid design center environment to seamlessly incorporate changes in spacecraft and mission design into navigation analysis and vice versa.

Carpenter, James R.; Berry, Kevin; Gregpru. Late; Speckman, Keith; Hur-Diaz, Sun; Surka, Derek; Gaylor, Dave

2010-01-01

12

Orbit Determination of the Lunar Reconnaissance Orbiter  

NASA Technical Reports Server (NTRS)

We present the results on precision orbit determination from the radio science investigation of the Lunar Reconnaissance Orbiter (LRO) spacecraft. We describe the data, modeling and methods used to achieve position knowledge several times better than the required 50-100m (in total position), over the period from 13 July 2009 to 31 January 2011. In addition to the near-continuous radiometric tracking data, we include altimetric data from the Lunar Orbiter Laser Altimeter (LOLA) in the form of crossover measurements, and show that they strongly improve the accuracy of the orbit reconstruction (total position overlap differences decrease from approx.70m to approx.23 m). To refine the spacecraft trajectory further, we develop a lunar gravity field by combining the newly acquired LRO data with the historical data. The reprocessing of the spacecraft trajectory with that model shows significantly increased accuracy (approx.20m with only the radiometric data, and approx.14m with the addition of the altimetric crossovers). LOLA topographic maps and calibration data from the Lunar Reconnaissance Orbiter Camera were used to supplement the results of the overlap analysis and demonstrate the trajectory accuracy.

Mazarico, Erwan; Rowlands, D. D.; Neumann, G. A.; Smith, D. E.; Torrence, M. H.; Lemoine, F. G.; Zuber, M. T.

2011-01-01

13

Preliminary orbit determination by static multivariate search  

NASA Astrophysics Data System (ADS)

A static multivariate search algorithm based on the Gram-Schmidt method is used for the problem of preliminary orbit determination using tracking data covering a very short arc of the orbit and very approximate initial estimate. The method is based on orthogonalization to find the primary and secondary search directions. No partial derivatives are needed. The extremum is found by parabolic extrapolation or interpolation of the function values. The suitability and effectiveness of the method for the problem of preliminary orbit determination is demonstrated. The approach yields desirable accuracies in simulated tracking data and application to actual tracking data of Indian satellites BHASKARA-2 APPLE and INSAT 1-A.

Rajendraprasad, P.; Gopinath, N. S.; Bhat, R. S.

14

Orbit Determination Issues for Libration Point Orbits  

NASA Technical Reports Server (NTRS)

Libration point mission designers require knowledge of orbital accuracy for a variety of analyses including station keeping control strategies, transfer trajectory design, and formation and constellation control. Past publications have detailed orbit determination (OD) results from individual libration point missions. This paper collects both published and unpublished results from four previous libration point missions (ISEE (International Sun-Earth Explorer) -3, SOHO (Solar and Heliospheric Observatory), ACE (Advanced Composition Explorer) and MAP (Microwave Anisotropy Probe)) supported by Goddard Space Flight Center's Guidance, Navigation & Control Center. The results of those missions are presented along with OD issues specific to each mission. All past missions have been limited to ground based tracking through NASA ground sites using standard range and Doppler measurement types. Advanced technology is enabling other OD options including onboard navigation using seaboard attitude sensors and the use of the Very Long Baseline Interferometry (VLBI) measurement Delta Differenced One-Way Range (DDOR). Both options potentially enable missions to reduce coherent dedicated tracking passes while maintaining orbital accuracy. With the increased projected loading of the DSN (Deep Space Network), missions must find alternatives to the standard OD scenario.

Beckman, Mark; Bauer, Frank (Technical Monitor)

2002-01-01

15

Orbit Determination Issues for Libration Point Orbits  

NASA Technical Reports Server (NTRS)

Libration point mission designers require knowledge of orbital accuracy for a variety of analyses including station keeping control strategies, transfer trajectory design, and formation and constellation control. Past publications have detailed orbit determination (OD) results from individual notation point missions. This paper collects both published and unpublished results from four previous notation point missions (ISEE-3, SOHO, ACE and MAP) supported by Goddard Space Flight Center's Guidance, Navigation & Control Center. The results of those missions are presented along with OD issues specific to each mission. All past missions have been limited to ground based tracking through NASA ground sites using standard marine and Doppler measurement types. Advanced technology is enabling other OD options including onboard navigation using onboard attitude sensors and the use of the Very Long Baseline Interferometry (VLBI) measurement Delta Differenced One-Way Range (DDOR). Both options potentially enable missions to reduce coherent dedicated tracking passes while maintaining orbital accuracy. With the increased projected loading of the DSN, missions must find alternatives to the standard OD scenario.

Beckman, Mark; Bauer, Frank (Technical Monitor)

2002-01-01

16

Mars Observer orbit determination analysis  

NASA Technical Reports Server (NTRS)

Results are presented of a simulated orbit determination analysis for three phases of the Mars Observer mission (interplanetary cruise, orbit insertion, and mapping), together with a summary of orbital accuracies throughout the Mars Observer mission. The plan for achieving the navigation objectives of the Mars Observer mission is described. These objectives are to navigate the Mars Observer spacecraft to Mars and achieve accurate targeting at Mars; to propulsively maneuver the spacecraft into a 3-day period, capture orbit; to navigate the spacecraft into a 1.96-hr period low-altitude, nearly circular mapping orbit; and to maintain Mars Observer in the mapping orbit throughout the 687 days devoted for scientific data acquisition. Factors that will affect the spacecraft during each of the three phases are discussed.

Esposito, Pasquale; Roth, Duane; Demcak, Stuart

1991-01-01

17

Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis  

NASA Technical Reports Server (NTRS)

LRO definitive and predictive accuracy requirements were easily met in the nominal mission orbit, using the LP150Q lunar gravity model. center dot Accuracy of the LP150Q model is poorer in the extended mission elliptical orbit. center dot Later lunar gravity models, in particular GSFC-GRAIL-270, improve OD accuracy in the extended mission. center dot Implementation of a constrained plane when the orbit is within 45 degrees of the Earth-Moon line improves cross-track accuracy. center dot Prediction accuracy is still challenged during full-Sun periods due to coarse spacecraft area modeling - Implementation of a multi-plate area model with definitive attitude input can eliminate prediction violations. - The FDF is evaluating using analytic and predicted attitude modeling to improve full-Sun prediction accuracy. center dot Comparison of FDF ephemeris file to high-precision ephemeris files provides gross confirmation that overlap compares properly assess orbit accuracy.

Slojkowski, Steven E.

2014-01-01

18

Initial Statistical Ranging of Orbits for Trans-Neptunian objects  

NASA Astrophysics Data System (ADS)

We consider initial determination of orbits for Trans-Neptunian objects (TNOs), a topical theme because of the rapidly growing TNO population and the challenges in recovering lost TNOs. We apply the method of initial phase-space ranging of orbits to the poorly observed TNOs. The a posteriori probability density of the TNO orbital elements can be highly complicated, and the covariance matrix of the linear approximation can fail to describe the true orbital uncertainties. With our new computation method, we can solve the inverse problem even for the case of two observations only. The a posteriori probability density for the elements is examined with a Monte Carlo technique by varying the TNO topocentric distances corresponding to the observation dates. We can optionally adopt a Bayesian approach in order to select the region of phase space with the most plausible orbits. This is accomplished by incorporating the semimajor axes, eccentricities, inclinations, and the absolute magnitudes of multi-apparition TNOs as a priori information. The resulting a posteriori distributions enable ephemeris prediction for TNO recovery observations, and we study the evolution of sky-plane uncertainties as a function of time elapsed from the discovery.

Muinonen, K.; Virtanen, J.; Bowell, E.

19

Orbit determination by genetic algorithm and application to GEO observation  

NASA Astrophysics Data System (ADS)

This paper demonstrates an initial orbit determination method that solves the problem by a genetic algorithm using two well-known solutions for the Lambert's problem: universal variable method and Battin method. This paper also suggests an intuitive error evaluation method in terms of rotational angle and orbit shape by separating orbit elements into two groups. As reference orbit, mean orbit elements (original two-lines elements) and osculating orbit elements considering the J2 effect are adopted and compared. Our proposed orbit determination method has been tested with actual optical observations of a geosynchronous spacecraft. It should be noted that this demonstration of the orbit determination is limited to one test case. This observation was conducted during approximately 70 min on 2013/05/15 UT. Our method was compared with the orbit elements propagated by SGP4 using the TLE of the spacecraft. The result indicates that our proposed method had a slightly better performance on estimating orbit shape than Gauss's methods and Escobal's method by 120 km. In addition, the result of the rotational angle is closer to the osculating orbit elements than the mean orbit elements by 0.02°, which supports that the estimated orbit is valid.

Hinagawa, Hideaki; Yamaoka, Hitoshi; Hanada, Toshiya

2014-02-01

20

Classical and modern orbit determination for asteroids  

NASA Astrophysics Data System (ADS)

With the substantial improvements in observational techniques we have to deal with very big databases, consisting of a few positions of an object over a short time span; this is often not enough to compute a preliminary orbit with traditional tools. In this paper we first review a classical method by C.F. Gauss to compute a preliminary orbit for asteroids. This method, followed by a least squares fit to improve the orbit, still today gives successful results when we have at least three separate observations. Then we introduce the basics of a very recent orbit determination theory, that has been thought just to be used with modern sets of data. These data allow us in many cases to know the angular position and velocity of an asteroid at a given time, even though the radial distance and velocity (r,dot r), needed to compute its full orbit, are unknown. The variables (r,dot r) can be constrained to a compact set, that we call the admissible region(AR), whose definition requires that the body belongs to the Solar System, that it is not a satellite of the Earth, and that it is not a "shooting star" (i.e. very close and very small). We provide a mathematical description of the AR: its topological properties are surprisingly simple, in fact it turns out that the AR cannot have more than two connected components. A sampling of the AR can be performed by means of a Delaunay triangulation; a finite number of six-parameter sets of initial conditions are thus defined, with each node of the triangulation representing a possible orbit (a virtual asteroid).

Gronchi, Giovanni F.

2005-04-01

21

Orbit Determination Analysis Utilizing Radiometric and Laser Ranging Measurements for GPS Orbit  

NASA Technical Reports Server (NTRS)

While navigation systems for the determination of the orbit of the Global Position System (GPS) have proven to be very effective, the current issues involve lowering the error in the GPS satellite ephemerides below their current level. In this document, the results of an orbit determination covariance assessment are provided. The analysis is intended to be the baseline orbit determination study comparing the benefits of adding laser ranging measurements from various numbers of ground stations. Results are shown for two starting longitude assumptions of the satellite location and for nine initial covariance cases for the GPS satellite state vector.

Welch, Bryan W.

2007-01-01

22

Simulation of precise orbit determination of lunar orbiters  

Microsoft Academic Search

Based on the ongoing Chinese lunar exploration mission, i.e. the “Chang'e 1” project, precise orbit determination of lunar orbiters is analyzed for the actual geographical distribution and observational accuracy of the Chinese united S-band (USB) observation and control network as well as the very long baseline interferometry (VLBI) tracking network. The observed data are first simulated, then solutions are found

Xiao-Gong Hu; Cheng Huang; Yong Huang

2005-01-01

23

Topocentric Orbit Determination: Algorithms for the Next Generation Surveys  

E-print Network

Topocentric Orbit Determination: Algorithms for the Next Generation Surveys Andrea Milani1 October 2007 Manuscript pages: 53 Figures: 8; Tables: 10 1 #12;Running head: Orbit Determination steps: preliminary orbit determination, least squares orbit fitting, and quality control assessing

Knezevic, Zoran

24

Orbit determination for ISRO satellite missions  

NASA Astrophysics Data System (ADS)

Indian Space Research Organisation (ISRO) has been successful in using the in-house developed orbit determination and prediction software for satellite missions of Bhaskara, Rohini and APPLE. Considering the requirements of satellite missions, software packages are developed, tested and their accuracies are assessed. Orbit determination packages developed are SOIP, for low earth orbits of Bhaskara and Rohini missions, ORIGIN and ODPM, for orbits related to all phases of geo-stationary missions and SEGNIP, for drift and geo-stationary orbits. Software is tested and qualified using tracking data of SIGNE-3, D5-B, OTS, SYMPHONIE satellites with the help of software available with CNES, ESA and DFVLR. The results match well with those available from these agencies. These packages have supported orbit determination successfully throughout the mission life for all ISRO satellite missions. Member-Secretary

Rao, Ch. Sreehari; Sinha, S. K.

25

Determination of GPS orbits to submeter accuracy  

NASA Technical Reports Server (NTRS)

Orbits for satellites of the Global Positioning System (GPS) were determined with submeter accuracy. Tests used to assess orbital accuracy include orbit comparisons from independent data sets, orbit prediction, ground baseline determination, and formal errors. One satellite tracked 8 hours each day shows rms error below 1 m even when predicted more than 3 days outside of a 1-week data arc. Differential tracking of the GPS satellites in high Earth orbit provides a powerful relative positioning capability, even when a relatively small continental U.S. fiducial tracking network is used with less than one-third of the full GPS constellation. To demonstrate this capability, baselines of up to 2000 km in North America were also determined with the GPS orbits. The 2000 km baselines show rms daily repeatability of 0.3 to 2 parts in 10 to the 8th power and agree with very long base interferometry (VLBI) solutions at the level of 1.5 parts in 10 to the 8th power. This GPS demonstration provides an opportunity to test different techniques for high-accuracy orbit determination for high Earth orbiters. The best GPS orbit strategies included data arcs of at least 1 week, process noise models for tropospheric fluctuations, estimation of GPS solar pressure coefficients, and combine processing of GPS carrier phase and pseudorange data. For data arc of 2 weeks, constrained process noise models for GPS dynamic parameters significantly improved the situation.

Bertiger, W. I.; Lichten, S. M.; Katsigris, E. C.

1988-01-01

26

Determination and prediction of Magellan's orbit  

NASA Technical Reports Server (NTRS)

The Magellan spacecraft has been systematically mapping the surface of Venus since September 15, 1990, using a synthetic aperture radar. The spacecraft orbit about Venus is nearly polar, with an orbital period of 3.26 hours and periapsis altitude of 295 km. The radiometric measurements and the data reduction method used to determine and predict the spacecraft state are described. Orbit determination and prediction results are given for the first 146 days of mapping (through February 8, 1991, 60 percent of the first rotation of Venus). Orbit accuracy requirements of 150 meters in the radial position, and 1 km in the along-track and cross-track positions are shown to be met, but with exceptions. All error requirements were exceeded during a combined period of limited in-plane orbit observability due to earth-orbit relative geometry, and increased measurement noise due to superior conjunction.

Engelhardt, D. B.; Mcnamee, J. B.; Wong, S. K.; Bonneau, F. G.; Graat, E. J.; Haw, R. J.; Kronschnabl, G. R.; Ryne, M. S.

1991-01-01

27

CATALOG OF ORBIT DETERMINATION RESULTS FOR LINKED, AUTONOMOUS,  

E-print Network

CATALOG OF ORBIT DETERMINATION RESULTS FOR LINKED, AUTONOMOUS, INTERPLANETARY SATELLITE ORBIT for Astrodynamics Research University of Colorado Boulder, CO 80309 Revised 3 Feb 2006 #12;CATALOG OF ORBIT DETERMINATION RESULTS FOR LINKED, AUTONOMOUS, INTERPLANETARY SATELLITE ORBIT NAVIGATION (Li

Born, George

28

Ionospheric refraction effects on orbit determination using the orbit determination error analysis system  

Microsoft Academic Search

The influence of ionospheric refraction on orbit determination was studied through the use of the Orbit Determination Error Analysis System (ODEAS). The results of a study of the orbital state estimate errors due to the ionospheric refraction corrections, particularly for measurements involving spacecraft-to-spacecraft tracking links, are presented. In current operational practice at the Goddard Space Flight Center (GSFC) Flight Dynamics

C. P. Yee; D. A. Kelbel; T. Lee; J. B. Dunham; G. D. Mistretta

1990-01-01

29

Modeling issues in precision orbit determination for Mars orbiter  

NASA Technical Reports Server (NTRS)

This paper examines the accuracy of recent Mars gravity models and the importance of perturbations due to the Mars radiation pressure and the Martian moons, Phobos and Deimos, on the trajectories of Mars orbiters. A linear orbit perturbation theory is used to characterize the patterns of gravity field near resonances for the Viking and Mariner 9 spacecraft. These resonances are shown to have considerable power and their potential for contributing to Mars gravity solutions is emphasized. It is shown that some of the same resonance orders which appear in the Viking orbits, dominate the radial orbit error spectrum for Mars Observer. Results of orbit determination simulations at the Goddard Space Flight Center show that the perturbations caused by the Martian moons and the Mars radiation pressure are larger than 0.1 mm/s, the expected precision of the Mars Observer Doppler tracking data. Tests with the Viking Doppler data indicate that best analysis of these data mandates the inclusion of the Phobos gravitational perturbation in the modeling of Viking spacecraft trajectories.

Lemoine, Frank G.; Rosborough, George W.; Smith, David E.

1990-01-01

30

Orbit Determination of Spacecraft in Earth-Moon L1 and L2 Libration Point Orbits  

NASA Technical Reports Server (NTRS)

The ARTEMIS mission, part of the THEMIS extended mission, is the first to fly spacecraft in the Earth-Moon Lissajous regions. In 2009, two of the five THEMIS spacecraft were redeployed from Earth-centered orbits to arrive in Earth-Moon Lissajous orbits in late 2010. Starting in August 2010, the ARTEMIS P1 spacecraft executed numerous stationkeeping maneuvers, initially maintaining a lunar L2 Lissajous orbit before transitioning into a lunar L1 orbit. The ARTEMIS P2 spacecraft entered a L1 Lissajous orbit in October 2010. In April 2011, both ARTEMIS spacecraft will suspend Lissajous stationkeeping and will be maneuvered into lunar orbits. The success of the ARTEMIS mission has allowed the science team to gather unprecedented magnetospheric measurements in the lunar Lissajous regions. In order to effectively perform lunar Lissajous stationkeeping maneuvers, the ARTEMIS operations team has provided orbit determination solutions with typical accuracies on the order of 0.1 km in position and 0.1 cm/s in velocity. The ARTEMIS team utilizes the Goddard Trajectory Determination System (GTDS), using a batch least squares method, to process range and Doppler tracking measurements from the NASA Deep Space Network (DSN), Berkeley Ground Station (BGS), Merritt Island (MILA) station, and United Space Network (USN). The team has also investigated processing of the same tracking data measurements using the Orbit Determination Tool Kit (ODTK) software, which uses an extended Kalman filter and recursive smoother to estimate the orbit. The orbit determination results from each of these methods will be presented and we will discuss the advantages and disadvantages associated with using each method in the lunar Lissajous regions. Orbit determination accuracy is dependent on both the quality and quantity of tracking measurements, fidelity of the orbit force models, and the estimation techniques used. Prior to Lissajous operations, the team determined the appropriate quantity of tracking measurements that would be needed to meet the required orbit determination accuracies. Analysts used the Orbit Determination Error Analysis System (ODEAS) to perform covariance analyses using various tracking data schedules. From this analysis, it was determined that 3.5 hours of DSN TRK-2-34 range and Doppler tracking data every other day would suffice to meet the predictive orbit knowledge accuracies in the Lissajous region. The results of this analysis are presented. Both GTDS and ODTK have high-fidelity environmental orbit force models that allow for very accurate orbit estimation in the lunar Lissajous regime. These models include solar radiation pressure, Earth and Moon gravity models, third body gravitational effects from the Sun, and to a lesser extent third body gravitational effects from Jupiter, Venus, Saturn, and Mars. Increased position and velocity uncertainties following each maneuver, due to small execution performance errors, requires that several days of post-maneuver tracking data be processed to converge on an accurate post-maneuver orbit solution. The effects of maneuvers on orbit determination accuracy will be presented, including a comparison of the batch least squares technique to the extended Kalman filter/smoother technique. We will present the maneuver calibration results derived from processing post-maneuver tracking data. A dominant error in the orbit estimation process is the uncertainty in solar radiation pressure and the resultant force on the spacecraft. An estimation of this value can include many related factors, such as the uncertainty in spacecraft reflectivity and surface area which is a function of spacecraft orientation (spin-axis attitude), uncertainty in spacecraft wet mass, and potential seasonal variability due to the changing direction of the Sun line relative to the Earth-Moon Lissajous reference frame. In addition, each spacecraft occasionally enters into Earth or Moon penumbra or umbra and these shadow crossings reduche solar radiation force for several hours. The effects of these events on orbit determination ac

Woodard, Mark; Cosgrove, Daniel; Morinelli, Patrick; Marchese, Jeff; Owens, Brandon; Folta, David

2011-01-01

31

On the determination of meteoroid orbital elements  

Microsoft Academic Search

The classical method of the determination of the orbital elements of meteoroids is based on a sequence of corrections applied to the velocity vector of an observed meteor. The main aim of such an approach is the determination of the meteoroid's motion under the gravitational influence of the Sun but we are able to observe this motion only under the

P. Pecina

1994-01-01

32

Mars Exploration Rovers orbit determination filter strategy  

NASA Technical Reports Server (NTRS)

The successful delivery of the Mars Exploration Rover (MER) landers to well with in the boundaries of their surface target areas in January of 2004 was the culmination of years of orbit determination analysis. The process began with a careful consideration of the filter parameters used for pre-launch covariance studies, and continued with the refinement of the filter after launch based on operational experience. At the same time, tools were developed to run a plethora of variations around the nominal filter and anlyze the results in ways that had never been previously attempted for an interplanetary mission. In addition to the achieved sub-kilometer Mars B plane orbit determination knowledge, the filter strategy and process responded to unexpected error sources by both detecting them and proving robust. All these facets of the MER orbit determination filter strategy are described in this paper.

McElrath, Tim; Watkins, Michael L.; Portock, Brian; Graat, Eric; Baird, Darren; Wawrzyniak, Geoffrey; Guinn, Joseph; Antreasian, Peter; Attiyah, Amy; Baalke, Ronald; Taber, William

2004-01-01

33

Ionospheric refraction effects on orbit determination using the orbit determination error analysis system  

NASA Technical Reports Server (NTRS)

The influence of ionospheric refraction on orbit determination was studied through the use of the Orbit Determination Error Analysis System (ODEAS). The results of a study of the orbital state estimate errors due to the ionospheric refraction corrections, particularly for measurements involving spacecraft-to-spacecraft tracking links, are presented. In current operational practice at the Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF), the ionospheric refraction effects on the tracking measurements are modeled in the Goddard Trajectory Determination System (GTDS) using the Bent ionospheric model. While GTDS has the capability of incorporating the ionospheric refraction effects for measurements involving ground-to-spacecraft tracking links, such as those generated by the Ground Spaceflight Tracking and Data Network (GSTDN), it does not have the capability to incorporate the refraction effects for spacecraft-to-spacecraft tracking links for measurements generated by the Tracking and Data Relay Satellite System (TDRSS). The lack of this particular capability in GTDS raised some concern about the achievable accuracy of the estimated orbit for certain classes of spacecraft missions that require high-precision orbits. Using an enhanced research version of GTDS, some efforts have already been made to assess the importance of the spacecraft-to-spacecraft ionospheric refraction corrections in an orbit determination process. While these studies were performed using simulated data or real tracking data in definitive orbit determination modes, the study results presented here were obtained by means of covariance analysis simulating the weighted least-squares method used in orbit determination.

Yee, C. P.; Kelbel, D. A.; Lee, T.; Dunham, J. B.; Mistretta, G. D.

1990-01-01

34

The simplified method of calculation of initial estimate in the orbit fitting problem. (Russian Title: ?????????? ????? ??????????? ?????????? ??????????? ??? ????????? ?????)  

NASA Astrophysics Data System (ADS)

The simplified method of setting of initial coordinates and velocities vector in the orbit fitting problem has been considered. The method is appropriate for the objects observed in a short arc. This method consists in the determination of coordinates and velocities by two close angular observations. The missing distance to the observed object is setting approximately. It is more convenient to compare with traditional methods of preliminary orbit calculation because it need not solving of eight-power equation. The testing of the method for several asteroids and comets has indicated that the accuracy of the resulting initial vector is sufficient for the further least-square orbit improvement.

Baturin, A. P.; Chuvashov, I. N.

2006-03-01

35

Algorithms for Autonomous GS Orbit Determination and Formation Flying  

NASA Technical Reports Server (NTRS)

This final report for our study of autonomous Global Positioning System (GPS) satellite orbit determination comprises two sections. The first is the Ph.D. dissertation written by Michael C. Moreau entitled, "GPS Receiver Architecture for Autonomous Navigation in High Earth Orbits." Dr. Moreau's work was conducted under both this project and a NASA GSRP. His dissertation describes the key design features of a receiver specifically designed for autonomous operation in high earth orbits (HEO). He focused on the implementation and testing of these features for the GSFC PiVoT receiver. The second part is a memo describing a robust method for autonomous initialization of the orbit estimate given very little a priori information and sparse measurements. This is a key piece missing in the design of receivers for HEO.

Moreau, Michael C.; Speed, Eden Denton-Trost; Axelrad, Penina; Leitner, Jesse (Technical Monitor)

2001-01-01

36

Filtering theory applied to orbit determination  

NASA Technical Reports Server (NTRS)

Modifications to the extended Kalman filter and the Jazwinski filter are made and compared with the classical extended Kalman filter in applications to orbit determination using real data. The results show that with the kind of data available today, the application of filtering theories in this field presents many problems.

Torroglosa, V.

1973-01-01

37

James Webb Space Telescope Orbit Determination Analysis  

NASA Technical Reports Server (NTRS)

The James Webb Space Telescope (JWST) is designed to study and answer fundamental astrophysical questions from an orbit about the Sun-Earth/Moon L2 libration point, 1.5 million km away from Earth. This paper describes the results of an orbit determination (OD) analysis of the JWST mission emphasizing the challenges specific to this mission in various mission phases. Three mid-course correction (MCC) maneuvers during launch and early orbit phase and transfer orbit phase are required for the spacecraft to reach L2. These three MCC maneuvers are MCC-1a at Launch+12 hours, MCC-1b at L+2.5 days and MCC-2 at L+30 days. Accurate OD solutions are needed to support MCC maneuver planning. A preliminary analysis shows that OD performance with the given assumptions is adequate to support MCC maneuver planning. During the nominal science operations phase, the mission requires better than 2 cm/sec velocity estimation performance to support stationkeeping maneuver planning. The major challenge to accurate JWST OD during the nominal science phase results from the unusually large solar radiation pressure force acting on the huge sunshield. Other challenges are stationkeeping maneuvers at 21-day intervals to keep JWST in orbit around L2, frequent attitude reorientations to align the JWST telescope with its targets and frequent maneuvers to unload momentum accumulated in the reaction wheels. Monte Carlo analysis shows that the proposed OD approach can produce solutions that meet the mission requirements.

Yoon, Sungpil; Rosales, Jose; Richon, Karen

2014-01-01

38

James Webb Space Telescope Orbit Determination Analysis  

NASA Technical Reports Server (NTRS)

The James Webb Space Telescope (JWST) is designed to study and answer fundamental astrophysical questions from an orbit about the Sun-EarthMoon L2 libration point, 1.5 million km away from Earth. Three mid-course correction (MCC) maneuvers during launch and early orbit phase and transfer orbit phase are required for the spacecraft to reach L2. These three MCC maneuvers are MCC-1a at Launch+12 hours, MCC-1b at L+2.5 days and MCC-2 at L+30 days. Accurate orbit determination (OD) solutions are needed to support MCC maneuver planning. A preliminary analysis shows that OD performance with the given assumptions is adequate to support MCC maneuver planning. During the nominal science operations phase, the mission requires better than 2 cmsec velocity estimation performance to support stationkeeping maneuver planning. The major challenge to accurate JWST OD during the nominal science phase results from the unusually large solar radiation pressure force acting on the huge sunshield. Other challenges are stationkeeping maneuvers at 21-day intervals to keep JWST in orbit around L2, frequent attitude reorientations to align the JWST telescope with its targets and frequent maneuvers to unload momentum accumulated in the reaction wheels. Monte Carlo analysis shows that the proposed OD approach can produce solutions that meet the mission requirements.

Yoon, Sungpil; Rosales, Jose; Richon, Karen

2014-01-01

39

Tethered body problems and relative motion orbit determination  

NASA Technical Reports Server (NTRS)

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.

Eades, J. B., Jr.; Wolf, H.

1972-01-01

40

Energy integral method for gravity field determination from satellite orbit coordinates  

Microsoft Academic Search

A fast iterative method for gravity field determination from low Earth satellite orbit coordinates has been developed and implemented successfully. The method is based on energy conservation and avoids problems related to orbit dynamics and initial state. In addition, the particular geometry of a repeat orbit is exploited by using a very efficient iterative estimation scheme, in which a set

P. N. A. M. Visser; N. Sneeuw; C. Gerlach

2003-01-01

41

Orbit Determination of GPS and Koreasat 2 Satellite Using Angle-Only Data and Requirements for Optical Tracking System  

Microsoft Academic Search

Gauss method for the initial orbit determination was tested using angle-only data obtained by orbit propagation using TLE and SGP4\\/SDP4 orbit propagation model. As the analysis of this simulation, a feasible time span between observation time of satellite resulting the minimum error to the true orbit was found. Initial orbit determination is performed using observational data of GPS 26 and

Woo-Kyoung Lee; Hyung-Chul Lim; Pil-Ho Park; Jae-Hyuk Youn; Hong-Suh Yim; Hong-Kyu Moon

2004-01-01

42

Initial Results from the Lunar Reconnaissance Orbiter Laser Ranging Investigation  

Microsoft Academic Search

The Lunar Reconnaissance Orbiter (LRO) Laser Ranging (LR) system is enabling the spacecraft to achieve its precision orbit determination requirement. The LR is routinely making one-way range measurements via laser pulse time-of-flight from the Earth to LRO. The LR consists of a receiver telescope mounted on LRO's high-gain antenna that captures the uplinked laser signal, and a fiber optic cable

M. H. Torrence; M. T. Zuber; D. E. Smith; E. Mazarico; F. G. Lemoine; J. F. Cavanaugh; X. Sun; T. Zagwodzki; P. Liiva

2009-01-01

43

Formation Flying In Highly Elliptical Orbits Initializing the Formation  

NASA Technical Reports Server (NTRS)

In this paper several methods are examined for initializing formations in which all spacecraft start in a common elliptical orbit subsequent to separation from the launch vehicle. The tetrahedron formation used on missions such as the Magnetospheric Multiscale (MMS), Auroral Multiscale Midex (AMM), and Cluster is used as a test bed Such a formation provides full three degrees-of-freedom in the relative motion about the reference orbit and is germane to several missions. The type of maneuver strategy that can be employed depends on the specific initial conditions of each member of the formation. Single-impulse maneuvers based on a Gaussian variation-of-parameters (VOP) approach, while operationally simple and intuitively-based, work only in a limited sense for a special class of initial conditions. These 'tailored' initial conditions are characterized as having only a few of the Keplerian elements different from the reference orbit. Attempts to achieve more generic initial conditions exceed the capabilities of the single impulse VOP. For these cases, multiple-impulse implementations are always possible but are generally less intuitive than the single-impulse case. The four-impulse VOP formalism discussed by Schaub is examined but smaller delta-V costs are achieved in our test problem by optimizing a Lambert solution.

Mailhe, Laurie; Schiff, Conrad; Hughes, Steven

2000-01-01

44

Orbit determination via adaptive Gaussian swarm optimization  

NASA Astrophysics Data System (ADS)

Accurate orbit determination (OD) is vital for every space mission. This paper proposes a novel heuristic filter based on adaptive sample-size Gaussian swarm optimization (AGSF). The proposed estimator considers the OD as a stochastic dynamic optimization problem that utilizes a swarm of particles in order to find the best estimation at every time step. One of the key contributions of this paper is the adaptation of the swarm size using a weighted variance approach. The proposed strategy is simulated for a low Earth orbit (LEO) OD problem utilizing geomagnetic field measurements at 700 km altitude. The performance of the proposed AGSF is verified using Monte Carlo simulation whose results are compared with other advanced sample based nonlinear filters. It is demonstrated that the adopted filter achieves about 2.5 km accuracy in position estimation that fulfills the essential requirements of accuracy and convergence time for OD problem.

Kiani, Maryam; Pourtakdoust, Seid H.

2015-02-01

45

Determination of orbits with Torun Orbit Processor system  

Microsoft Academic Search

The Torun Orbit Processor system (TOP) is a multipurpose system designed to provide the research requirements of the various orbital problems for artificial satellites. The analysis of mathematical model for the TOP system began in 1991 and coding for the IBM PC and Sun SparcStation 10 computers was completed in 1993. TOP was first used for laser data processing of

A. Drozyner

1995-01-01

46

Orbit determination of Tance-1 satellite using VLBI data  

NASA Astrophysics Data System (ADS)

On 30 December, 2003, China successfully launched the first satellite Tance-1 of Chinese Geospace Double Star Exploration Program, i.e. "Double Star Program (DSP)", on an improved Long March 2C launch vehicle. The Tance-1 satellite is operating at an orbit around the earth with a 550km perigee, 78000km apogee and 28.5 degree inclination.VLBI technique can track Tance-1 satellite or even far satellites such as lunar vehicles. To validate the VLBI technique in the on-going Chinese lunar exploration mission, Shanghai Astronomical Observatory (SHAO) organized to track the Tance-1 satellite with Chinese three VLBI stations: Shanghai, Kunming and Urumchi Orbit Determination (OD) of the Tance-1 satellite with about two days VLBI dada, and the capability of OD with VLBI data are studied. The results show that the VLBI-based orbit solutions improve the fit level over the initial orbit. The VLBI-delay-based orbit solution shows that the RMS of residuals of VLBI delay data is about 5.5m, and about 2.0cm/s for the withheld VLBI delay rate data. The VLBI-delay-rate-based orbit solution shows that the RMS of residuals of VLBI delay rate data is about 1.3cm/s, and about 29m for the withheld VLBI delay data. In the situation of orbit determination with VLBI delay and delay rate data with data sigma 5.5m and 1.3cm/s respectively, the RMS of residuals are 5.5,m and 2.0cm/s respectively. The simulation data assess the performance of the solutions. Considering the dynamic model errors of the Tance-1 satellite, the accuracy of the position is about km magnitude, and the accuracy of the velocity is about cm/s magnitude. The simulation work also show the dramatic accuracy improvement of OD with VLBI and USB combined.

Huang, Y.; Hu, X. G.; Huang, C.; Jiang, D. R.

2006-01-01

47

A numerical comparison with the Ceplecha analytical meteoroid orbit determination method  

E-print Network

A numerical comparison with the Ceplecha analytical meteoroid orbit determination method David L accepted 11 May 2011) Abstract­Analytic methods by Ceplecha have long been used for the determination of meteoroid heliocentric orbits. These methods include both the derivation of an initial atmospheric contact

Wiegert, Paul

48

Sequential Orbit Determination with the Cubed-Sphere Gravity Model  

E-print Network

Sequential Orbit Determination with the Cubed-Sphere Gravity Model Brandon A. Jones1 , George H characterizes the improved computational efficiency of sequential orbit determination, specifically the extended, orbit propagation and determination systems may now use this model to improve fidelity without any

Born, George

49

From Ancient Paradoxes to Modern Orbit Determination  

NASA Astrophysics Data System (ADS)

In the 5th century BC, Zeno advanced a set of paradoxes to show motion and time are impossible, hence an illusion. The problem of motion has since driven much scientific thought and discovery, extending to Einstein's insights and the quantum revolution. To determine and predict the motion of remote objects within the solar system, a methodology has been refined over centuries. It integrates ideas from astronomy, physics, mathematics, measurement, and probability theory, having motivated most of those developments. Recently generalized and made numerically efficient, statistical orbit determination has made it possible to remotely fly Magellan and other spacecraft through the turbulent atmospheres of Venus and other planets while estimating atmospheric structure and internal mass distributions of the planet. Over limited time-scales, the methodology can predict the position of the Moon within a meter and asteroids within tens of meters -- their velocities at the millimeter per second level -- while characterizing the probable correctness of the prediction. Current software and networks disseminate such ephemeris information in moments; over the last 12 years, 10 million ephemerides have been provided by the Horizons system, at the request of 300000 different users. Applications range from ground and space telescope pointing to correlation with observations recorded on Babylonian cuneiform tablets. Rapid orbit updates are particularly important for planetary radars integrating weak small-body echoes moving quickly through the frequency spectrum due to relative motion. A loop is established in which the predicted delay-Doppler measurement and uncertainties are used to configure the radar. Both predictions are then compared to actual results, the asteroid or comet orbit solution improved, and the radar system optimally adjusted. Still, after 2500 years and tremendous descriptive success, there remain substantial problems understanding and predicting motion.

Giorgini, Jon D.

2008-09-01

50

GPS as an orbit determination subsystems  

NASA Technical Reports Server (NTRS)

This paper evaluates the use of Global Positioning System (GPS) receivers as a primary source of tracking data for low-Earth orbit satellites. GPS data is an alternative to using range, azimuth, elevation, and range-rate (RAER) data from the Air Force Satellite Control Network antennas, the Space Ground Link System (SGLS). This evaluation is applicable to missions such as Skipper, a joint U.S. and Russian atmosphere research mission, that will rely on a GPS receiver as a primary tracking data source. The Detachment 2, Space and Missile Systems Center's Test Support Complex (TSC) conducted the evaluation based on receiver data from the Space Test Experiment Platform Mission O (STEP-O) and Advanced Photovoltaic and Electronics Experiments (APEX) satellites. The TSC performed orbit reconstruction and prediction on the STEP-0 and APEX vehicles using GPS receiver navigation solution data, SGLS RAER data, and SGLS anglesonly (azimuth and elevation) data. For the STEP-O case, the navigation solution based orbits proved to be more accurate than SGLS RAER based orbits. For the APEX case, navigation solution based orbits proved to be less accurate than SGLS RAER based orbits for orbit prediction, and results for orbit reconstruction were inconclusive due to the lack of a precise truth orbit. After evaluating several different GPS data processing methods, the TSC concluded that using GPS navigation solution data is a viable alternative to using SGLS RAER data.

Fennessey, Richard; Roberts, Pat; Knight, Robin; Vanvolkinburg, Bart

1995-01-01

51

WHEN IS A GROUP ACTION DETERMINED BY IT'S ORBIT STRUCTURE?  

E-print Network

WHEN IS A GROUP ACTION DETERMINED BY IT'S ORBIT STRUCTURE? DAVID FISHER AND KEVIN WHYTE Abstract. We present a simple approach to questions of topological orbit equivalence for actions of countable for any element are contained in codimension two submanifolds, ev­ ery orbit equivalence is equivariant

Fisher, David

52

A new method for determination of satellite orbits by transfer  

Microsoft Academic Search

The original idea of a new method for determination of satellite orbits by transfer is from Two-Way Satellite Time and Frequency\\u000a Transfer (TWSTFT). The original method is called “determination of satellite orbit by transfer”. The method is not only for\\u000a determination of satellite orbit but also for the time transfer with high accuracy and precision. The advantage is that the

Zhigang Li; Xuhai Yang; Guoxiang Ai; Huli Si; Rongchuan Qiao; Chugang Feng

2009-01-01

53

Orbit Determination of GPS and Koreasat 2 Satellite Using Angle-Only Data and Requirements for Optical Tracking System  

NASA Astrophysics Data System (ADS)

Gauss method for the initial orbit determination was tested using angle-only data obtained by orbit propagation using TLE and SGP4/SDP4 orbit propagation model. As the analysis of this simulation, a feasible time span between observation time of satellite resulting the minimum error to the true orbit was found. Initial orbit determination is performed using observational data of GPS 26 and Koreasat 2 from 0.6m telescope of KAO(Korea Astronomy Observatory) and precise orbit determination is also performed using simulated data. The result of precise orbit determination shows that the accuracy of resulting orbit is related to the accuracy of the observations and the number of data.

Lee, Woo-Kyoung; Lim, Hyung-Chul; Park, Pil-Ho; Youn, Jae-Hyuk; Yim, Hong-Suh; Moon, Hong-Kyu

2004-09-01

54

Optimal solutions of unobservable orbit determination problems  

NASA Astrophysics Data System (ADS)

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.

Cicci, David A.; Tapley, Byron D.

1988-12-01

55

Spacecraft Orbit Determination with The B-spline Approximation Method  

NASA Astrophysics Data System (ADS)

It is known that the dynamical orbit determination is the most common way to get the precise orbits of spacecraft. However, it is hard to build up the precise dynamical model of spacecraft sometimes. In order to solve this problem, the technique of the orbit determination with the B-spline approximation method based on the theory of function approximation is presented in this article. In order to verify the effectiveness of this method, simulative orbit determinations in the cases of LEO (Low Earth Orbit), MEO (Medium Earth Orbit), and HEO (Highly Eccentric Orbit) satellites are performed, and it is shown that this method has a reliable accuracy and stable solution. The approach can be performed in both the conventional celestial coordinate system and the conventional terrestrial coordinate system. The spacecraft's position and velocity can be calculated directly with the B-spline approximation method, it needs not to integrate the dynamical equations, nor to calculate the state transfer matrix, thus the burden of calculations in the orbit determination is reduced substantially relative to the dynamical orbit determination method. The technique not only has a certain theoretical significance, but also can serve as a conventional algorithm in the spacecraft orbit determination.

Song, Ye-zhi; Huang, Yong; Hu, Xiao-gong; Li, Pei-jia; Cao, Jian-feng

2014-04-01

56

Two Line Element Aided Orbit Determination Using Single Station SLR Data  

NASA Astrophysics Data System (ADS)

It is difficult to use the single-station satellite laser ranging (SLR) data for orbit determination, due to the singular geometrical distribution of the observations. The single-station data generated by performing diffuse-reflection SLR to the orbital space debris are therefore ineffective for orbit improvement. We propose a method to resolve the singularity in the observation distribution. Since the initial orbits of space debris such as the two line elements (TLE) exist prior to the SLR tracking, we use it to simulate observations from other SLR sites. We combine the simulated and actual observations with a proper weight to fit an orbit, thus resolving the singularity in the observation distribution. We then propagate the fitted orbit forward in time to validate against the precision ephemeris derived from the international laser ranging service (ILRS). The method is implemented and applied to the satellite Ajisai. Using the single-station SLR data of five passes in one day and corresponding TLE as the initial orbit, we fit the orbit and the generated predictions. The predicted position error is less than 40 meter in five-day span, significantly improved over the initial SGP4 propagated orbit. The method's potential application to space debris orbit improvement is also discussed.

Liang, Z. P.; Liu, C. Z.; Fan, C. B.; Sun, M. G.

2012-03-01

57

Orbit determination and prediction study for Dynamic Explorer 2  

NASA Technical Reports Server (NTRS)

Definitive orbit determination accuracy and orbit prediction accuracy for the Dynamic Explorer-2 (DE-2) are studied using the trajectory determination system for the period within six weeks of spacecraft reentry. Baseline accuracies using standard orbit determination models and methods are established. A promising general technique for improving the orbit determination accuracy of high drag orbits, estimation of random drag variations at perigee passages, is investigated. This technique improved the fit to the tracking data by a factor of five and improved the solution overlap consistency by a factor of two during a period in which the spacecraft perigee altitude was below 200 kilometers. The results of the DE-2 orbit predictions showed that improvement in short term prediction accuracy reduces to the problem of predicting future drag scale factors: the smoothness of the solar 10.7 centimeter flux density suggests that this may be feasible.

Smith, R. L.; Nakai, Y.; Doll, C. E.

1983-01-01

58

Determination of the orbital parameters of binary pulsars  

E-print Network

We present a simple novel method for determining the orbital parameters of binary pulsars. This method works with any sort of orbital sampling, no matter how sparse, provided that information on the period derivatives is available with each measurement of the rotational period of the pulsar, and it is applicable to binary systems with nearly circular orbits. We use the technique to precisely estimate the hitherto unknown orbital parameters of two binary millisecond pulsars in the globular cluster 47 Tucanae, 47 Tuc S and T. The method can also be used more generally to make first-order estimates of the orbital parameters of binary systems using a minimal amount of data.

P. C. Freire; M. Kramer; A. G. Lyne

2000-10-23

59

The ROAD program. [(rapid orbit analysis and determination)  

NASA Technical Reports Server (NTRS)

The philosophy, history, operation, calibration of and some analyses with the ROAD (Rapid Orbit Analysis and Determination) program are described. This semi-numeric trajectory program integrates and analyses mean element variations for earth orbits with great efficiency. Through it's use, extensive zonal, resonant harmonic and earth tidal determinations have been made at Goddard Space Flight Center since 1969.

Wagner, C. A.; Douglas, B. C.; Williamson, R. G.

1974-01-01

60

The determination of the satellite orbit of Mariner 9.  

NASA Technical Reports Server (NTRS)

This paper presents a comprehensive analysis of the Mars orbital phase of the Mariner 9 trajectory as determined from Earth based radio data. Both the method and accuracy of the orbit determination process are reviewed. Analysis is presented to show the effects of Mars gravity model and node in the plane of the sky errors on the accuracy of orbit determination. In addition the long term evolution of the orbit from insertion to date is presented, and is decomposed into effects from the Mars gravity field, n-body perturbations, and solar radiation pressure. Since the orbit period is nearly commensurable with the Mars rotational period, the orbit experiences significant resonance perturbations. The primary perturbation is in-track with a maximum amplitude of 1000 km and a wavelength of 39 revolutions.

Born, G. H.; Christensen, E. J.; Ferrari, A. J.; Jordan, J. F.; Reinbold, S. J.

1972-01-01

61

TOPEX/Poseidon precision orbit determination production and expert system  

NASA Technical Reports Server (NTRS)

TOPEX/Poseidon (T/P) is a joint mission between NASA and the Centre National d'Etudes Spatiales (CNES), the French Space Agency. The TOPEX/Poseidon Precision Orbit Determination Production System (PODPS) was developed at Goddard Space Flight Center (NASA/GSFC) to produce the absolute orbital reference required to support the fundamental ocean science goals of this satellite altimeter mission within NASA. The orbital trajectory for T/P is required to have a RMS accuracy of 13 centimeters in its radial component. This requirement is based on the effective use of the satellite altimetry for the isolation of absolute long-wavelength ocean topography important for monitoring global changes in the ocean circulation system. This orbit modeling requirement is at an unprecedented accuracy level for this type of satellite. In order to routinely produce and evaluate these orbits, GSFC has developed a production and supporting expert system. The PODPS is a menu driven system allowing routine importation and processing of tracking data for orbit determination, and an evaluation of the quality of the orbit so produced through a progressive series of tests. Phase 1 of the expert system grades the orbit and displays test results. Later phases undergoing implementation, will prescribe corrective actions when unsatisfactory results are seen. This paper describes the design and implementation of this orbit determination production system and the basis for its orbit accuracy assessment within the expert system.

Putney, Barbara; Zelensky, Nikita; Klosko, Steven

1993-01-01

62

Phenomenological determination of the orbital angular momentum.  

SciTech Connect

Measurements involving the gluon spin, {Delta}G(x, t) and the corresponding asymmetry, A(x,t) = {Delta}G(x,t)/G(x,t) play an important role in quantitative understanding of proton structure. We have modeled the asymmetry perturbatively and calculated model corrections to obtain information about non-perturbative spin-orbit effects. These models are consistent with existing COMPASS and HERMES data on the gluon asymmetry. The J{sub z} = 1/2 sum rule is used to generate values of orbital angular momentum at LO and NLO. For models consistent with data, the orbital angular momentum is small. Our studies specify accuracy that future measurements should achieve to constrain theoretical models for nucleon structure.

Ramsey, G. P.; High Energy Physics; Loyola Univ.

2009-01-01

63

Phenomenological Determination of the Orbital Angular Momentum  

SciTech Connect

Measurements involving the gluon spin, {delta}G(x, t) and the corresponding asymmetry, A(x,t) = {delta}G(x,t)/G(x,t) play an important role in quantitative understanding of proton structure. We have modeled the asymmetry perturbatively and calculated model corrections to obtain information about non-perturbative spin-orbit effects. These models are consistent with existing COMPASS and HERMES data on the gluon asymmetry. The J{sub z} = (1/2) sum rule is used to generate values of orbital angular momentum at LO and NLO. For models consistent with data, the orbital angular momentum is small. Our studies specify accuracy that future measurements should achieve to constrain theoretical models for nucleon structure.

Ramsey, Gordon P. [Physics Department, Loyola University, Chicago, IL 60626 (United States) and High Energy Physics Division, Argonne National Lab, Argonne, IL 60439 (United States)

2009-08-04

64

The Study and Applications of Satellite and Satellite Constellation Autonomous Orbit Determination Using Star Sensor  

NASA Astrophysics Data System (ADS)

Autonomous satellite orbit determination is a key technique in autonomous satellite navigation. Many kinds of technologies have been proposed to realize the autonomous satellite navigation, such as the star sensor, the Earth magnetometer, the occultation time survey, and the phase measurement of X-ray pulsar signals. This dissertation studies a method of autonomous satellite orbit determination using star sensor. Moreover, the method is extended to the autonomous navigation of satellite constellation and the space-based surveillance. In chapters 1 and 2, some usual time and reference systems are introduced. Then the principles of several typical autonomous navigation methods, and their merits and shortcomings are analyzed. In chapter 3, the autonomous satellite orbit determination using star sensor and infrared Earth sensor (IRES) is specifically studied, which is based on the status movement simulation, the stellar background observation from star sensor, and the Earth center direction survey from IRES. By simulating the low Earth orbit satellites and pseudo Geostationary Earth orbit (PGEO) satellites, the precision of position and speed with autonomous orbit determination using star sensor is obtained. Besides, the autonomous orbit determination using star sensor with double detectors is studied. According to the observation equation's characters, an optimized type of star sensor and IRES initial assembly model is proposed. In the study of the PGEO autonomous orbit determination, an efficient sampling frequency of measurements is promoted. The simulation results confirm that the autonomous satellite orbit determination using star sensor is feasible for satellites with all kinds of altitudes. In chapter 4, the method of autonomous satellite orbit determination using star sensor is extended to the autonomous navigation of mini-satellite constellation. Combining with the high-accuracy inter satellite links data, the precision of the determined orbit and constellation configuration is higher than that ever expected. In chapter 5, two related pre-project researches are developed with respect to the space-based satellite surveillance. One solves the un-convergence question in the preliminary orbit determination and finds an advantageous preliminary orbit determination using inter satellite angle measurement. In the other pre-project research, a creative space-based satellite surveillance model is proposed, which is based on the autonomous surveillance platform navigation. Using the star sensor's navigation data associated with the inter satellite angle measurement, the orbit parameters of the tracking space objects and the surveillance platform are determined. Compared to the available experiment results overseas, the preliminary orbit determination method and the autonomous navigation surveillance platform model are found to be feasible. The research will significantly contribute to the new conception of ``space awareness'', as well as our country's space security construction.

Gan, Q. B.

2012-07-01

65

Method of resolving radio phase ambiguity in satellite orbit determination  

NASA Technical Reports Server (NTRS)

For satellite orbit determination, the most accurate observable available today is microwave radio phase, which can be differenced between observing stations and between satellites to cancel both transmitter- and receiver-related errors. For maximum accuracy, the integer cycle ambiguities of the doubly differenced observations must be resolved. To perform this ambiguity resolution, a bootstrapping strategy is proposed. This strategy requires the tracking stations to have a wide ranging progression of spacings. By conventional 'integrated Doppler' processing of the observations from the most widely spaced stations, the orbits are determined well enough to permit resolution of the ambiguities for the most closely spaced stations. The resolution of these ambiguities reduces the uncertainty of the orbit determination enough to enable ambiguity resolution for more widely spaced stations, which further reduces the orbital uncertainty. In a test of this strategy with six tracking stations, both the formal and the true errors of determining Global Positioning System satellite orbits were reduced by a factor of 2.

Councelman, Charles C., III; Abbot, Richard I.

1989-01-01

66

Determination of the orbital parameters of binary pulsars  

Microsoft Academic Search

We present a simple novel method for determining the orbital parameters of\\u000abinary pulsars. This method works with any sort of orbital sampling, no matter\\u000ahow sparse, provided that information on the period derivatives is available\\u000awith each measurement of the rotational period of the pulsar, and it is\\u000aapplicable to binary systems with nearly circular orbits. We use the

P. C. Freire; M. Kramer; A. G. Lyne

2000-01-01

67

Orbit determination of the Lunar Reconnaissance Orbiter using laser ranging and radiometric tracking data  

NASA Astrophysics Data System (ADS)

The Lunar Reconnaissance Orbiter (LRO) launched in 2009 by the National Aeronautics and Space Administration (NASA) still orbits the Moon in a polar orbit at an altitude of 50 kilometers and below. Its main objective is the detailed exploration of the Moon's surface by means of the Lunar Orbiter Laser Altimeter (LOLA) and three high resolution cameras bundled in the Lunar Reconnaissance Orbiter Camera (LROC) unit. Referring these observations to a Moon-fixed reference frame requires the computation of highly accurate and consistent orbits. For this task only Earth-based observations are available, primarily radiometric tracking data from stations in the United States, Australia and Europe. In addition, LRO is prepared for one-way laser measurements from specially adapted sites. Currently, 10 laser stations participate more or less regularly in this experiment. For operational reasons, the official LRO orbits from NASA only include radiometric data so far. In this presentation, we investigate the benefit of the laser ranging data by feeding both types of observations in an integrated orbit determination process. All computations are performed by an in-house software development based on a dynamical approach improving orbit and force parameters in an iterative way. Special attention is paid to the determination of bias parameters, in particular of timing biases between radio and laser stations and the drift and aging of the LRO spacecraft clock. The solutions from the combined data set will be compared to radio- and laser-only orbits as well as to the NASA orbits. Further results will show how recent gravity field models from the GRAIL mission can improve the accuracy of the LRO orbits.

Löcher, Anno; Kusche, Jürgen

2014-05-01

68

Decentralized determination of relative orbit for formation flying satellite  

Microsoft Academic Search

Autonomous formation flying is an important technology for the future space missions involving multiple satellites, and one of the key requirements of formation flying is accurate relative navigation. This paper develops an efficient approach of autonomous relative orbit determination for formation flying satellite. In view of that some formation flying satellites work at the orbits which are beyond the range

Dan Xue; Xibin Cao; Yunhua Wu

2006-01-01

69

Simplified Orbit Determination Algorithm for Low Earth Orbit Satellites Using Spaceborne Gps Navigation Sensor  

NASA Astrophysics Data System (ADS)

In this paper, the main work is focused on designing and simplifying the orbit determination algorithm which will be used for Low Earth Orbit (LEO) navigation. The various data processing algorithms, state estimation algorithms and modeling forces were studied in detail, and simplified algorithm is selected to reduce hardware burden and computational cost. This is done by using raw navigation solution provided by GPS Navigation sensor. A fixed step-size Runge-Kutta 4th order numerical integration method is selected for orbit propagation. Both, the least square and Extended Kalman Filter (EKF) orbit estimation algorithms are developed and the results of the same are compared with each other. EKF algorithm converges faster than least square algorithm. EKF algorithm satisfies the criterions of low computation burden which is required for autonomous orbit determination. Simple static force models also feasible to reduce the hardware burden and computational cost.

Tukaram Aghav, Sandip; Achyut Gangal, Shashikala

2014-06-01

70

An exact solution to determination of an open orbit  

E-print Network

We present an exact solution of the equations for orbit determination of a two body system in a hyperbolic or parabolic motion. In solving this problem, we extend the method employed by Asada, Akasaka and Kasai (AAK) for a binary system in an elliptic orbit. The solutions applicable to each of elliptic, hyperbolic and parabolic orbits are obtained by the new approach, and they are all expressed in an explicit form, remarkably, only in terms of elementary functions. We show also that the solutions for an open orbit are recovered by making a suitable transformation of the AAK solution for an elliptic case.

Hideki Asada

2006-10-23

71

19 CFR 207.114 - Initial determination.  

Code of Federal Regulations, 2010 CFR

... Customs Duties UNITED STATES INTERNATIONAL TRADE COMMISSION NONADJUDICATIVE INVESTIGATIONS...Regulations for the North American Free Trade Agreement Procedures for Imposing...and convincing evidence. (d) Effect of initial determination....

2010-04-01

72

49 CFR 7.31 - Initial determinations.  

Code of Federal Regulations, 2010 CFR

...writing, at the same time he or she is notified...responsible for the initial determination to...of work and/or time needed to process...component doing so will contact the requestor either...may be made at the time of the initial request for...

2010-10-01

73

Real-time on-board orbit determination with DORIS  

NASA Technical Reports Server (NTRS)

A spaceborne orbit determination system is being developed by the French Space Agency (CNES) for the SPOT 4 satellite. It processes DORIS measurements to produce an orbit with an accuracy of about 50O meters rms. In order to evaluate the reliability of the software, it was combined with the MERCATOR man/machine interface and used to process the TOPEX/Poseidon DORIS data in near real time during the validation phase of the instrument, at JPL and at CNES. This paper gives an overview of the orbit determination system and presents the results of the TOPEX/Poseidon experiment.

Berthias, J.-P.; Jayles, C.; Pradines, D.

1993-01-01

74

GEODYN Orbit Determination of Dawn at Vesta using Image Constraints  

NASA Astrophysics Data System (ADS)

The Dawn spacecraft has completed the orbital phase of its mapping mission of the asteroid 4 Vesta. We utilized radiometric measurements and image constraints to compute the spacecraft orbit using the GEODYN II orbit determination software. Image constraints are computed control point vectors which point from the spacecraft to landmarks observed in two images of the same region of Vesta, and are a newly developed measurement type for GEODYN. This capability was added because image constraints can provide supplemental information on the spacecraft trajectory especially in a weak gravity environment. Due to the geometric nature of image constraints, they can reduce the orbital errors in the along- and cross-track directions, which have typically carried higher uncertainty in previous interplanetary missions. Image constraints are also useful during times of absence of radiometric tracking data. Improvements to orbit determination can provide improved gravity field estimation and knowledge of the interior structure of Vesta. The NASA Deep Space Network (DSN) provides X-band tracking measurements for Dawn. Radiometric and image constraints were processed for the High Altitude Mapping Orbit (HAMO) I and II, and the Low Altitude Mapping Orbit (LAMO), from 23 Sept 2011 to 26 July 2012. The spacecraft altitude was roughly 685 km during HAMO and 200 km during LAMO. Doppler and range residual RMS were under 1 mm/s and 10 m, respectively. Improvement in orbital knowledge from image constraints is typically greatest in the cross-track direction and in our analysis these residuals were typically better than 500 m.

Centinello, F. J., III; Mazarico, E.; Zuber, M. T.

2012-12-01

75

Modifications to Encke's method for long arc orbit determination solutions  

NASA Technical Reports Server (NTRS)

An expanded model is developed that permits the extrapolation of Encke's method for the determination of orbits with long arcs, and the model is used to determine a solution for the Lageos trajectory. Encke's method is reviewed emphasizing the nature of the growth of the Encke ratio and the reliability of extrapolated reference trajectories. The reference-orbit formulation is improved by including parameters that accommodate drag and large-amplitude perodic variations in the orbital elements. The proposed Long Arc Model is expected to provide a maximum Encke ratio that is an order of magnitude more reliable than that given by the secularly precessing ellipse. The computational cost of using the Long Arc Model is shown to compare favorably with that of the true force model, and the long arc solutions are useful for current orbit-determination needs.

Lundberg, J. B.; Bettadpur, S.; Eanes, R. J.

1992-01-01

76

Determination of the orbital parameters of binary pulsars  

E-print Network

We present a simple method for determination of the orbital parameters of binary pulsars, using data on the pulsar period at multiple observing epochs. This method uses the circular nature of the velocity space orbit of Keplerian motion and produces preliminary values based on two one dimensional searches. Preliminary orbital parameter values are then refined using a computationally efficient linear least square fit. This method works for random and sparse sampling of the binary orbit. We demonstrate the technique on (a) the highly eccentric binary pulsar PSR J0514-4002 (the first known pulsar in the globular cluster NGC 1851) and (b) 47 Tuc T, a binary pulsar with a nearly circular orbit.

Bhaswati Bhattacharyya; Rajaram Nityananda

2008-04-03

77

UD filtering and smoothing applied to orbit determination  

NASA Astrophysics Data System (ADS)

The performance is described of filtering and smoothing techniques applied to orbit determination of earth satellites. A (forward pass) Kalman filter along with an adaptive procedure for estimating the dynamic noise level which prevents the divergence of estimates due to inaccurate modelling of the orbital motion is implemented in the UD factorization form. The backward smoother is a numerically efficient version of the Rauch-Tung-Striebel (RTS) smoother. This smoother, developed in the UD form, has proven to be economical, compact and competitive for computer implementation. Digital simulations are performed for 2 situations of orbit determination: short arc orbit determination with favorably tracking geometry; and long arc orbit determination with existing tracking stations. Tests containing many levels of modelling degradation are carried out. The forward pass adaptive UD filter behaves so as to deal with these modelling nuisances and does not allow the divergence phenomenon to occur. In no real time operations, the backward UD smoother is used to improve the accuracy of the estimates and of the covariances resulting from the filtering phase. The results show, in the main, that the UD smoother can enhance the accuracy of the forward pass filter, sometimes by an order of magnitude. For post-flight analysis, the UD smoother is a useful tool when one aims at reconstituting the entire trajectory of the orbital motion covered by the tracking data.

Kuga, Helio Koiti; Rios-Neto, Atair; Orlando, Valcir

1989-08-01

78

Orbit Determination Accuracy for Comets on Earth-Impacting Trajectories  

NASA Technical Reports Server (NTRS)

The results presented show the level of orbit determination accuracy obtainable for long-period comets discovered approximately one year before collision with Earth. Preliminary orbits are determined from simulated observations using Gauss' method. Additional measurements are incorporated to improve the solution through the use of a Kalman filter, and include non-gravitational perturbations due to outgassing. Comparisons between observatories in several different circular heliocentric orbits show that observatories in orbits with radii less than 1 AU result in increased orbit determination accuracy for short tracking durations due to increased parallax per unit time. However, an observatory at 1 AU will perform similarly if the tracking duration is increased, and accuracy is significantly improved if additional observatories are positioned at the Sun-Earth Lagrange points L3, L4, or L5. A single observatory at 1 AU capable of both optical and range measurements yields the highest orbit determination accuracy in the shortest amount of time when compared to other systems of observatories.

Kay-Bunnell, Linda

2004-01-01

79

Determination of Eros Physical Parameters for Near Earth Asteroid Rendezvous Orbit Phase Navigation  

NASA Technical Reports Server (NTRS)

Navigation of the orbit phase of the Near Earth steroid Rendezvous (NEAR) mission will re,quire determination of certain physical parameters describing the size, shape, gravity field, attitude and inertial properties of Eros. Prior to launch, little was known about Eros except for its orbit which could be determined with high precision from ground based telescope observations. Radar bounce and light curve data provided a rough estimate of Eros shape and a fairly good estimate of the pole, prime meridian and spin rate. However, the determination of the NEAR spacecraft orbit requires a high precision model of Eros's physical parameters and the ground based data provides only marginal a priori information. Eros is the principal source of perturbations of the spacecraft's trajectory and the principal source of data for determining the orbit. The initial orbit determination strategy is therefore concerned with developing a precise model of Eros. The original plan for Eros orbital operations was to execute a series of rendezvous burns beginning on December 20,1998 and insert into a close Eros orbit in January 1999. As a result of an unplanned termination of the rendezvous burn on December 20, 1998, the NEAR spacecraft continued on its high velocity approach trajectory and passed within 3900 km of Eros on December 23, 1998. The planned rendezvous burn was delayed until January 3, 1999 which resulted in the spacecraft being placed on a trajectory that slowly returns to Eros with a subsequent delay of close Eros orbital operations until February 2001. The flyby of Eros provided a brief glimpse and allowed for a crude estimate of the pole, prime meridian and mass of Eros. More importantly for navigation, orbit determination software was executed in the landmark tracking mode to determine the spacecraft orbit and a preliminary shape and landmark data base has been obtained. The flyby also provided an opportunity to test orbit determination operational procedures that will be used in February of 2001. The initial attitude and spin rate of Eros, as well as estimates of reference landmark locations, are obtained from images of the asteroid. These initial estimates are used as a priori values for a more precise refinement of these parameters by the orbit determination software which combines optical measurements with Doppler tracking data to obtain solutions for the required parameters. As the spacecraft is maneuvered; closer to the asteroid, estimates of spacecraft state, asteroid attitude, solar pressure, landmark locations and Eros physical parameters including mass, moments of inertia and gravity harmonics are determined with increasing precision. The determination of the elements of the inertia tensor of the asteroid is critical to spacecraft orbit determination and prediction of the asteroid attitude. The moments of inertia about the principal axes are also of scientific interest since they provide some insight into the internal mass distribution. Determination of the principal axes moments of inertia will depend on observing free precession in the asteroid's attitude dynamics. Gravity harmonics are in themselves of interest to science. When compared with the asteroid shape, some insight may be obtained into Eros' internal structure. The location of the center of mass derived from the first degree harmonic coefficients give a direct indication of overall mass distribution. The second degree harmonic coefficients relate to the radial distribution of mass. Higher degree harmonics may be compared with surface features to gain additional insight into mass distribution. In this paper, estimates of Eros physical parameters obtained from the December 23,1998 flyby will be presented. This new knowledge will be applied to simplification of Eros orbital operations in February of 2001. The resulting revision to the orbit determination strategy will also be discussed.

Miller, J. K.; Antreasian, P. J.; Georgini, J.; Owen, W. M.; Williams, B. G.; Yeomans, D. K.

1995-01-01

80

GOCE: precise orbit determination for the entire mission  

NASA Astrophysics Data System (ADS)

The Gravity field and steady-state Ocean Circulation Explorer (GOCE) was the first Earth explorer core mission of the European Space Agency. It was launched on March 17, 2009 into a Sun-synchronous dusk-dawn orbit and re-entered into the Earth's atmosphere on November 11, 2013. The satellite altitude was between 255 and 225 km for the measurement phases. The European GOCE Gravity consortium is responsible for the Level 1b to Level 2 data processing in the frame of the GOCE High-level processing facility (HPF). The Precise Science Orbit (PSO) is one Level 2 product, which was produced under the responsibility of the Astronomical Institute of the University of Bern within the HPF. This PSO product has been continuously delivered during the entire mission. Regular checks guaranteed a high consistency and quality of the orbits. A correlation between solar activity, GPS data availability and quality of the orbits was found. The accuracy of the kinematic orbit primarily suffers from this. Improvements in modeling the range corrections at the retro-reflector array for the SLR measurements were made and implemented in the independent SLR validation for the GOCE PSO products. The satellite laser ranging (SLR) validation finally states an orbit accuracy of 2.42 cm for the kinematic and 1.84 cm for the reduced-dynamic orbits over the entire mission. The common-mode accelerations from the GOCE gradiometer were not used for the official PSO product, but in addition to the operational HPF work a study was performed to investigate to which extent common-mode accelerations improve the reduced-dynamic orbit determination results. The accelerometer data may be used to derive realistic constraints for the empirical accelerations estimated for the reduced-dynamic orbit determination, which already improves the orbit quality. On top of that the accelerometer data may further improve the orbit quality if realistic constraints and state-of-the-art background models such as gravity field and ocean tide models are used for the reduced-dynamic orbit determination.

Bock, Heike; Jäggi, Adrian; Beutler, Gerhard; Meyer, Ulrich

2014-07-01

81

Orbit determination for the Mariner Mark II Comet Rendezvous/Asteroid Flyby mission - The orbiting phase  

NASA Technical Reports Server (NTRS)

The Comet Rendezvous/Asteroid Flyby (CRAF) mission is the first of the Mariner Mark II mission set, designed to explore the outer solar system. Major objectives of orbit determination will be determine the positions and masses of the comet and asteroid and the relative position of the spacecraft, which is important to accurate pointing of the scan platform on which the narrow angle camera and scientific instruments are positioned. Position prediction is also important, since continuous commuication with the spacecraft will not be possible. The small gravitational attractions and poorly known ephemerides of the comet and asteroid, and the small, slow spacecraft orbit about the comet, pose significant new problems for orbit determination. Results of simulations studying the effectiveness of key data types, the accuracies of estimates, and prediction capabilities, are presented.

Weeks, C. J.

1986-01-01

82

Orbit determination for the Mariner Mark II Comet Rendezvous/Asteroid Flyby mission - The orbiting phase  

NASA Astrophysics Data System (ADS)

The Comet Rendezvous/Asteroid Flyby (CRAF) mission is the first of the Mariner Mark II mission set, designed to explore the outer solar system. Major objectives of orbit determination will be determine the positions and masses of the comet and asteroid and the relative position of the spacecraft, which is important to accurate pointing of the scan platform on which the narrow angle camera and scientific instruments are positioned. Position prediction is also important, since continuous commuication with the spacecraft will not be possible. The small gravitational attractions and poorly known ephemerides of the comet and asteroid, and the small, slow spacecraft orbit about the comet, pose significant new problems for orbit determination. Results of simulations studying the effectiveness of key data types, the accuracies of estimates, and prediction capabilities, are presented.

Weeks, C. J.

1986-08-01

83

Implementation of a low-cost, commercial orbit determination system  

NASA Technical Reports Server (NTRS)

Traditional satellite and launch control systems have consisted of custom solutions requiring significant development and maintenance costs. These systems have typically been designed to support specific program requirements and are expensive to modify and augment after delivery. The expanding role of space in today's marketplace combined with the increased sophistication and capabilities of modern satellites has created a need for more efficient, lower cost solutions to complete command and control systems. Recent technical advances have resulted in commercial-off-the-shelf products which greatly reduce the complete life-cycle costs associated with satellite launch and control system procurements. System integrators and spacecraft operators have, however, been slow to integrate these commercial based solutions into a comprehensive command and control system. This is due, in part, to a resistance to change and the fact that many available products are unable to effectively communicate with other commercial products. The United States Air Force, responsible for the health and safety of over 84 satellites via its Air Force Satellite Control Network (AFSCN), has embarked on an initiative to prove that commercial products can be used effectively to form a comprehensive command and control system. The initial version of this system is being installed at the Air Force's Center for Research Support (CERES) located at the National Test Facility in Colorado Springs, Colorado. The first stage of this initiative involved the identification of commercial products capable of satisfying each functional element of a command and control system. A significant requirement in this product selection criteria was flexibility and ability to integrate with other available commercial products. This paper discusses the functions and capabilities of the product selected to provide orbit determination functions for this comprehensive command and control system.

Corrigan, Jim

1994-01-01

84

Intial orbit determination results for Jason-1: towards a 1-cm orbit  

NASA Technical Reports Server (NTRS)

The U.S/France Jason-1 oceanographic mission is carrying state-of-the-art radiometric tracking systems (GPS and Doris) to support precise orbit determination (POD) requirements. The performance of the systems is strongly reflected in the early POD results. Results of both internal and external (e.g., satellite laser ranging) comparisons support that the 2.5 cm radial Rh4S requirement is being readily met, and provide reasons for optimism that 1 cm can be achieved. We discuss the POD strategy underlying these orbits, as well as the challenging issues that bear on the understanding and characterization of an orbit solution at the l-cm level. We also describe a system for producing science quality orbits in near real time in order to support emerging applications in operational oceanography.

Haines, B. J.; Haines, B.; Bertiger, W.; Desai, S.; Kuang, D.; Munson, T.; Reichert, A.; Young, L.; Willis, P.

2002-01-01

85

Precise Tracking of the Magellan and Pioneer Venus Orbiters by Same-Beam Interferometry. Part 2: Orbit Determination Analysis  

NASA Technical Reports Server (NTRS)

A new radio metric positioning technique has demonstrated improved orbit determination accuracy for the Magellan and Pioneer Venus Orbiter orbiters. The new technique, known as Same-Beam Interferometry (SBI), is applicable to the positioning of multiple planetary rovers, landers, and orbiters which may simultaneously be observed in the same beamwidth of Earth-based radio antennas. Measurements of carrier phase are differenced between spacecraft and between receiving stations to determine the plane-of-sky components of the separation vector(s) between the spacecraft. The SBI measurements complement the information contained in line-of-sight Doppler measurements, leading to improved orbit determination accuracy. Orbit determination solutions have been obtained for a number of 48-hour data arcs using combinations of Doppler, differenced-Doppler, and SBI data acquired in the spring of 1991. Orbit determination accuracy is assessed by comparing orbit solutions from adjacent data arcs. The orbit solution differences are shown to agree with expected orbit determination uncertainties. The results from this demonstration show that the orbit determination accuracy for Magellan obtained by using Doppler plus SBI data is better than the accuracy achieved using Doppler plus differenced-Doppler by a factor of four and better than the accuracy achieved using only Doppler by a factor of eighteen. The orbit determination accuracy for Pioneer Venus Orbiter using Doppler plus SBI data is better than the accuracy using only Doppler data by 30 percent.

Folkner, W. M.; Border, J. S.; Nandi, S.; Zukor, K. S.

1993-01-01

86

Orbit determination support of the Ocean Topography Experiment (TOPEX)/Poseidon operational orbit  

NASA Technical Reports Server (NTRS)

The Ocean Topography Experiment (TOPEX/Poseidon) mission is designed to determine the topography of the Earth's sea surface over a 3-year period, beginning shortly after launch in July 1992. TOPEX/Poseidon is a joint venture between the United States National Aeronautics and Space Administration (NASA) and the French Centre Nationale d'Etudes Spatiales. The Jet Propulsion Laboratory is NASA's TOPEX/Poseidon project center. The Tracking and Data Relay Satellite System (TDRSS) will nominally be used to support the day-to-day orbit determination aspects of the mission. Due to its extensive experience with TDRSS tracking data, the NASA Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF) will receive and process TDRSS observational data. To fulfill the scientific goals of the mission, it is necessary to achieve and maintain a very precise orbit. The most stringent accuracy requirements are associated with planning and evaluating orbit maneuvers, which will place the spacecraft in its mission orbit and maintain the required ground track. To determine if the FDF can meet the TOPEX/Poseidon maneuver accuracy requirements, covariance analysis was undertaken with the Orbit Determination Error Analysis System (ODEAS). The covariance analysis addressed many aspects of TOPEX/Poseidon orbit determination, including arc length, force models, and other processing options. The most recent analysis has focused on determining the size of the geopotential field necessary to meet the maneuver support requirements. Analysis was undertaken with the full 50 x 50 Goddard Earth Model (GEM) T3 field as well as smaller representations of this model.

Schanzle, A. F.; Rovnak, J. E.; Bolvin, D. T.; Doll, C. E.

1993-01-01

87

Orbit determination of space objects based on sparse optical data  

E-print Network

While building up a catalog of Earth orbiting objects, if the available optical observations are sparse, not deliberate follow ups of specific objects, no orbit determination is possible without previous correlation of observations obtained at different times. This correlation step is the most computationally intensive, and becomes more and more difficult as the number of objects to be discovered increases. In this paper we tested two different algorithms (and the related prototype software) recently developed to solve the correlation problem for objects in geostationary orbit (GEO), including the accurate orbit determination by full least squares solutions with all six orbital elements. Because of the presence in the GEO region of a significant subpopulation of high area to mass objects, strongly affected by non-gravitational perturbations, it was actually necessary to solve also for dynamical parameters describing these effects, that is to fit between 6 and 8 free parameters for each orbit. The validation was based upon a set of real data, acquired from the ESA Space Debris Telescope (ESASDT) at the Teide observatory (Canary Islands). We proved that it is possible to assemble a set of sparse observations into a set of objects with orbits, starting from a sparse time distribution of observations, which would be compatible with a survey capable of covering the region of interest in the sky just once per night. This could result in a significant reduction of the requirements for a future telescope network, with respect to what would have been required with the previously known algorithm for correlation and orbit determination.

A. Milani; G. Tommei; D. Farnocchia; A. Rossi; T. Schildknecht; R. Jehn

2010-12-23

88

Spacecraft Orbit Anomaly Representation Using Thrust-Fourier-Coefficients with Orbit Determination Toolbox  

NASA Astrophysics Data System (ADS)

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) is modified to adapt this technique in order to verify the performance of this interpolation approach. Spacecraft anomaly cases are based on either single or multiple low or high thrust maneuvers and the unknown thrust accelerations are recovered and compared with the true thrust acceleration. The advantage of this approach is to easily append TFCs and its dynamics to the pre-built ODTBX, which enables us to blend post-anomaly tracking data to improve the performance of the interpolation representation in the absence of detailed information about a maneuver. It allows us to improve space situational awareness in the areas of uncertainty propagation, anomaly characterization and track correlation.

Ko, H.; Scheeres, D.

2014-09-01

89

Autonomous satellite orbital navigation and attitude determination  

NASA Technical Reports Server (NTRS)

A known linear landmark navigation system is described. It involves the use of an electro-optical sensor to provide sightings to linear earth features such as highways and coast lines. The sensor concept and the navigation system mechanization are described. Performance analysis results show that landmark sightings provide accurate navigation update and that this accuracy can be preserved using radar altimeter measurements. Description of a stellar inertial attitude determination system is also presented. Attitude reference performance consistent with the requirement of the navigation system is shown to be achievable by this method.

Kau, S. P.

1978-01-01

90

The definition of initial orbital elements of comet Herschel-Rigollet. (Russian Title: ??????????? ????????? ?????????? ?????? ?????? ???????-???????)  

NASA Astrophysics Data System (ADS)

The analysis various systems of initial orbital elements of comet Herschel-Rigollet defined in bases on different sample of observations was given. In spite of slight quantity of first appearance observations the introduction of weighting coefficients and the new rejection algorithm is allowed to define the most precise system of orbital elements with the least value of volume confidence region.

Syusina, O. M.; Chernitsov, A. M.; Tamarov, V. A.; Baturin, A. P.

2011-07-01

91

An intelligent interface for satellite operations: Your Orbit Determination Assistant (YODA)  

NASA Technical Reports Server (NTRS)

An intelligent interface is often characterized by the ability to adapt evaluation criteria as the environment and user goals change. Some factors that impact these adaptations are redefinition of task goals and, hence, user requirements; time criticality; and system status. To implement adaptations affected by these factors, a new set of capabilities must be incorporated into the human-computer interface design. These capabilities include: (1) dynamic update and removal of control states based on user inputs, (2) generation and removal of logical dependencies as change occurs, (3) uniform and smooth interfacing to numerous processes, databases, and expert systems, and (4) unobtrusive on-line assistance to users of concepts were applied and incorporated into a human-computer interface using artificial intelligence techniques to create a prototype expert system, Your Orbit Determination Assistant (YODA). YODA is a smart interface that supports, in real teime, orbit analysts who must determine the location of a satellite during the station acquisition phase of a mission. Also described is the integration of four knowledge sources required to support the orbit determination assistant: orbital mechanics, spacecraft specifications, characteristics of the mission support software, and orbit analyst experience. This initial effort is continuing with expansion of YODA's capabilities, including evaluation of results of the orbit determination task.

Schur, Anne

1988-01-01

92

Evaluation of advanced geopotential models for operational orbit determination  

NASA Technical Reports Server (NTRS)

To meet future orbit determination accuracy requirements for different NASA projects, analyses are performed using Tracking and Data Relay Satellite System (TDRSS) tracking measurements and orbit determination improvements in areas such as the modeling of the Earth's gravitational field. Current operational requirements are satisfied using the Goddard Earth Model-9 (GEM-9) geopotential model with the harmonic expansion truncated at order and degree 21 (21-by-21). This study evaluates the performance of 36-by-36 geopotential models, such as the GEM-10B and Preliminary Goddard Solution-3117 (PGS-3117) models. The Earth Radiation Budget Satellite (ERBS) and LANDSAT-5 are the spacecraft considered in this study.

Radomski, M. S.; Davis, B. E.; Samii, M. V.; Engel, C. J.; Doll, C. E.

1988-01-01

93

JASON-1: a New Reference for Precise Orbit Determination  

NASA Astrophysics Data System (ADS)

- The French-American satellite Jason-1 was launched in December 2001 to continue the mission of the TOPEX/Poseïdon satellite. Following the same ground track as its famous predecessor since January 14, 2002, Jason-1 continues the collection of high precision altimeter data over the oceans that contributes to our understanding of how oceans influence global climate processes. One of the key features of both the TOPEX/Poseïdon and the Jason missions is the precision of the orbit determination, better than 3 cm RMS on the radial component, which is without equal today. This is the result of many years of improvements in the knowledge of the Earth gravity field, as well as a very important efforts in the design of the satellites and in the modeling of the surface forces. It also benefits from the use of the most sophisticated tracking instrument available today . Equipped with the most advanced DORIS receiver, with a high quality Laser retroreflector array and with a top of the line dual frequency GPS receiver, Jason has become the new laboratory for precision orbit determination and for comparing the performances of tracking systems. The availability of the altimeter data offers a valuable additional source of validation of the orbits. Results show that these combined efforts are paying off. Orbits computed by many POD groups associated with the Jason project compare to the few centimeter level. Furthermore, orbits computed independantly with each of the available data types compare to within 2 cm RMS radially without any tuning of spacecraft models or excessive use of empirical accelerations. The combination of DORIS, SLR and GPS data now appears feasible and meaningful. In this paper, we will present the principles behind the Jason precise orbit determination, the current results and the efforts underway to improve the orbit precision.

Berthias, Jean-Paul; Broca, Patrick; Ferrier, Christophe; Gratton, Serge

94

The role of laser determined orbits in geodesy and geophysics  

NASA Technical Reports Server (NTRS)

Some of the results of orbit analysis from the NASA SLR analysis group are presented. The earth's orientation was determined for 5-day intervals to 1.9 mas for the pole and 0.09 msec for length of day. The 3d center of mass station positions was determined to 33 mm over a period of 3 months, and geodesic rates of SLR tracking sites were determined to 5 mm/yr.

Kolenkiewicz, R.; Smith, D. E.; Dunn, P. J.; Torrence, M. H.; Robbins, J. W.

1991-01-01

95

Use of the VLBI delay observable for orbit determination of Earth-orbiting VLBI satellites  

NASA Technical Reports Server (NTRS)

Very long-baseline interferometry (VLBI) observations using a radio telescope in Earth orbit were performed first in the 1980s. Two spacecraft dedicated to VLBI are scheduled for launch in 1995; the primary scientific goals of these missions will be astrophysical in nature. This article addresses the use of space VLBI delay data for the additional purpose of improving the orbit determination of the Earth-orbiting spacecraft. In an idealized case of quasi-simultaneous observations of three radio sources in orthogonal directions, analytical expressions are found for the instantaneous spacecraft position and its error. The typical position error is at least as large as the distance corresponding to the delay measurement accuracy but can be much greater for some geometries. A number of practical considerations, such as system noise and imperfect calibrations, set bounds on the orbit-determination accuracy realistically achievable using space VLBI delay data. These effects limit the spacecraft position accuracy to at least 35 cm (and probably 3 m or more) for the first generation of dedicated space VLBI experiments. Even a 35-cm orbital accuracy would fail to provide global VLBI astrometry as accurate as ground-only VLBI. Recommended charges in future space VLBI missions are unlikely to make space VLBI competitive with ground-only VLBI in global astrometric measurements.

Ulvestad, J. S.

1992-01-01

96

Simplified solution to determination of a binary orbit  

E-print Network

We present a simplified solution to orbit determination of a binary system from astrometric observations. An exact solution was found by Asada, Akasaka and Kasai by assuming no observational errors. We extend the solution considering observational data. The generalized solution is expressed in terms of elementary functions, and therefore requires neither iterative nor numerical methods.

Hideki Asada; Toshio Akasaka; Kazuya Kudoh

2006-12-04

97

Determination of orbital drag perturbations caused by atmospheric effects  

Microsoft Academic Search

Atmospheric perturbations of the elements of the artificial satellites orbits are determined using a special model of distribution and variations of the total density of the upper atmosphere between 200-500 km. The model includes diurnal and semi-annual density variations, variations with solar activity and geomagnetic index and latitudinal changes. The height profile is expressed by multiple exponential functions. The equations

L. Sehnal

1986-01-01

98

Precise Orbit Determination of Earth's Satellites for Climate Change Investigation  

Microsoft Academic Search

The tremendous improvement of the gravity field models which we are achieving with the last Earth's satellite missions like, CHAMP, GRACE and GOCE devoted to its recovery could make feasibile the use of precise orbit determination (POD) of Earth satellites as a tool for sensing global changes of some key atmosphere parameters like refractivity and extinction. Such improvements indeed, coupled

Francesco Vespe

2010-01-01

99

Modeling GPS satellite attitude variation for precise orbit determination  

Microsoft Academic Search

High precision geodetic application of the Global Positioning System (GPS) require highly precise ephemerides of the GPS satellites. An accurate model for the non-gravitational forces on the GPS satellites is a key to high quality GPS orbit determination, especially in long arcs. In this paper the effect of the satellite solar panel orientation error is investigated. These effects are approximated

D. Kuang; H. J. Rim; B. E. Schutz; P. A. M. Abusali

1996-01-01

100

Capabilities of a single TDRS to support user orbit determination  

NASA Astrophysics Data System (ADS)

It is shown that the single-TDRS S-band tracking configuration satisfies the navigation certification requirements for operational orbit determination support for the Landsat-5, SMM, SME, and Earth Radiation Budget Satellite (ERBS) spacecraft. It is also shown that a pair of 3-min bilateration ranging transponder system (BRTS) tracking passes every 4 hrs, one each from two different BRTS locations, is sufficient to maintain user orbit accuracy to the navigation certification requirements. The BRTS tracking requirements for the single-TDRS configuration will also apply to each TDRS in a multiple-TDRS configuration.

Cappellari, J. O., Jr.; Kay, P. Y.; Nicholson, A. M.

101

Capabilities of a single TDRS to support user orbit determination  

NASA Technical Reports Server (NTRS)

It is shown that the single-TDRS S-band tracking configuration satisfies the navigation certification requirements for operational orbit determination support for the Landsat-5, SMM, SME, and Earth Radiation Budget Satellite (ERBS) spacecraft. It is also shown that a pair of 3-min bilateration ranging transponder system (BRTS) tracking passes every 4 hrs, one each from two different BRTS locations, is sufficient to maintain user orbit accuracy to the navigation certification requirements. The BRTS tracking requirements for the single-TDRS configuration will also apply to each TDRS in a multiple-TDRS configuration.

Cappellari, J. O., Jr.; Kay, P. Y.; Nicholson, A. M.

1988-01-01

102

Automated Orbit Determination System (AODS) requirements definition and analysis  

NASA Technical Reports Server (NTRS)

The requirements definition for the prototype version of the automated orbit determination system (AODS) is presented including the AODS requirements at all levels, the functional model as determined through the structured analysis performed during requirements definition, and the results of the requirements analysis. Also specified are the implementation strategy for AODS and the AODS-required external support software system (ADEPT), input and output message formats, and procedures for modifying the requirements.

Waligora, S. R.; Goorevich, C. E.; Teles, J.; Pajerski, R. S.

1980-01-01

103

Expected orbit determination performance for the TOPEX/Poseidon mission  

SciTech Connect

The TOPEX/Poseidon (T/P) mission, launched during the summer of 1992, has the requirement that the radial component of its orbit must be computed to an accuracy of 13 cm root-mean-square (rms) or better, allowing measurements of the sea surface height to be computed to similar accuracy when the satellite height is differenced with the altimeter measurements. This will be done by combining precise satellite tracking measurements with precise models of the forces acting on the satellite. The Space Geodesy Branch at Goddard Space Flight Center (GSFC), as part of the T/P precision orbit determination (POD) Team, has the responsibility within NASA for the T/P precise orbit computations. The prelaunch activities of the T/P POD Team have been mainly directed towards developing improved models of the static and time-varying gravitational forces acting on T/P and precise models for the non-conservative forces perturbing the orbit of T/P such as atmospheric drag, solar and Earth radiation pressure, and thermal imbalances. The radial orbit error budget for T/P allows 10 cm rms error due to gravity field mismodeling, 3 cm due to solid Earth and ocean tides, 6 cm due to radiative forces, and 3 cm due to atmospheric drag. A prelaunch assessment of the current modeling accuracies for these forces indicates that the radial orbit error requirements can be achieved with the current models, and can probably be surpassed once T/P tracking data are used to fine tune the models. Provided that the performance of the T/P spacecraft is nominal, the precise orbits computed by the T/P POD Team should be accurate to 13 cm or better radially.

Nerem, R.S.; Putney, B.H.; Marshall, J.A.; Lerch, F.J. (NASA/Goddard Space Flight Center, Greenbelt, MD (United States)); Pavlis, E.C. (Univ. of Maryland, College Park (United States)); Klosko, S.M.; Luthcke, S.B.; Patel, G.B.; Williamson, R.G.; Zelensky, N.P.

1993-03-01

104

Applicable Tracking Data Arcs for NORAD TLE Orbit Determination of the KOMPSAT-1 Satellite Using GPS Navigation Solutions  

NASA Astrophysics Data System (ADS)

NORAD Two Line Element (TLE) is very useful to simplify the ground station antenna pointing and mission operations. When a satellite operations facility has the capability to determine NORAD type TLE which is independent of NORAD, it is important to analyze the applicable tracking data arcs for obtaining the best possible orbit. The applicable tracking data arcs for NORAD independent TLE orbit determination of the KOMPSAT-1 using GPS navigation solutions was analyzed for the best possible orbit determination and propagation results. Data spans of the GPS navi gation solutions from 1 day to 5 days were used for TLE orbit determination and the results were used as initial orbit for SGP4 orbit propagation. The operational orbit determination results using KOMPSAT-1 Mission Analysis and Planning System (MAPS) were used as references for the comparisons. The best-matched orbit determination was obtained when 3 days of GPS navigation solutions were used. The resulting 4 days of orbit propagation results were within 2 km of the KOMPSAT-1 MAPS results.

Lee, Byoung-Sun

2005-09-01

105

Enhancing the kinematic precise orbit determination of low earth orbiters using GPS receiver clock modelling  

NASA Astrophysics Data System (ADS)

Clock error estimation has been the focus of a great deal of research because of the extensive usage of clocks in GPS positioning applications. The receiver clock error in the spacecraft orbit determination is commonly estimated on an epoch-by-epoch basis, along with the spacecraft’s position. However, due to the high correlation between the spacecraft orbit altitude and the receiver clock parameters, estimates of the radial component are degraded in the kinematic approach. Using clocks with high stability, the predictable behaviour of the receiver oscillator can be exploited to improve the positioning accuracy, especially for the radial component. This paper introduces two GPS receiver clock models to describe the deterministic and stochastic property of the receiver clock, both of which can improve the accuracy of kinematic orbit determination for spacecraft in low earth orbit. In particular, the clock parameters are estimated as time offset and frequency offset in the two-state model. The frequency drift is also estimated as an unknown parameter in the three-state model. Additionally, residual non-deterministic random errors such as frequency white noise, frequency random walk noise and frequency random run noise are modelled. Test results indicate that the positioning accuracy could be improved significantly using one day of GRACE flight data. In particular, the error of the radial component was reduced by over 40.0% in the real-time scenario.

Yang, Yang; Yue, Xiaokui; Yuan, Jianping; Rizos, Chris

2014-11-01

106

Nonorthogonal molecular orbital method: Single-determinant theory  

NASA Astrophysics Data System (ADS)

Using the variational principle, we have derived a variant of the Adams-Gilbert equation for nonorthogonal orbitals of a single-determinant wave function, which we name the modified Adams-Gilbert equation. If we divide the molecular system into several subsystems, such as bonds, lone pairs, and residues, we can solve the equations for the subsystems one by one. Thus, this procedure has linear scaling. We have presented a practical procedure for solving the equations that is also applicable to macromolecular calculations. The numerical examples show that the procedure yields, with reasonable effort, results comparable with those of the Hartree-Fock-Roothaan method for orthogonal orbitals. To resolve the convergence difficulty in the self-consistent-field iterations, we have found that virtual molecular-orbital shifts are very effective.

Watanabe, Yoshihiro; Matsuoka, Osamu

2014-05-01

107

Orbit Determination Support for the Microwave Anisotropy Probe (MAP)  

NASA Technical Reports Server (NTRS)

NASA's Microwave Anisotropy Probe (MAP) was launched from the Cape Canaveral Air Force Station Complex 17 aboard a Delta II 7425-10 expendable launch vehicle on June 30, 2001. The spacecraft received a nominal direct insertion by the Delta expendable launch vehicle into a 185-km circular orbit with a 28.7deg inclination. MAP was then maneuvered into a sequence of phasing loops designed to set up a lunar swingby (gravity-assisted acceleration) of the spacecraft onto a transfer trajectory to a lissajous orbit about the Earth-Sun L2 Lagrange point, about 1.5 million km from Earth. Because of its complex orbital characteristics, the mission provided a unique challenge for orbit determination (OD) support in many orbital regimes. This paper summarizes the premission trajectory covariance error analysis, as well as actual OD results. The use and impact of the various tracking stations, systems, and measurements will be also discussed. Important lessons learned from the MAP OD support team will be presented. There will be a discussion of the challenges presented to OD support including the effects of delta-Vs at apogee as well as perigee, and the impact of the spacecraft attitude mode on the OD accuracy and covariance analysis.

Bauer, Frank (Technical Monitor); Truong, Son H.; Cuevas, Osvaldo O.; Slojkowski, Steven

2003-01-01

108

Hardware in-the-Loop Demonstration of Real-Time Orbit Determination in High Earth Orbits  

NASA Technical Reports Server (NTRS)

This paper presents results from a study conducted at Goddard Space Flight Center (GSFC) to assess the real-time orbit determination accuracy of GPS-based navigation in a number of different high Earth orbital regimes. Measurements collected from a GPS receiver (connected to a GPS radio frequency (RF) signal simulator) were processed in a navigation filter in real-time, and resulting errors in the estimated states were assessed. For the most challenging orbit simulated, a 12 hour Molniya orbit with an apogee of approximately 39,000 km, mean total position and velocity errors were approximately 7 meters and 3 mm/s respectively. The study also makes direct comparisons between the results from the above hardware in-the-loop tests and results obtained by processing GPS measurements generated from software simulations. Care was taken to use the same models and assumptions in the generation of both the real-time and software simulated measurements, in order that the real-time data could be used to help validate the assumptions and models used in the software simulations. The study makes use of the unique capabilities of the Formation Flying Test Bed at GSFC, which provides a capability to interface with different GPS receivers and to produce real-time, filtered orbit solutions even when less than four satellites are visible. The result is a powerful tool for assessing onboard navigation performance in a wide range of orbital regimes, and a test-bed for developing software and procedures for use in real spacecraft applications.

Moreau, Michael; Naasz, Bo; Leitner, Jesse; Carpenter, J. Russell; Gaylor, Dave

2005-01-01

109

Tests of Magnetometer/Sun-Sensor Orbit Determination Using Flight Data and Mark L. Psiaki  

E-print Network

Tests of Magnetometer/Sun-Sensor Orbit Determination Using Flight Data Hee Jung* and Mark L. Psiaki Cornell University, Ithaca, N.Y. 14853-7501 Abstract A magnetometer-based orbit determination batch filter the performance of a low-cost autonomous orbit determination system. The spacecraft's orbit, magnetometer biases

Psiaki, Mark L.

110

American Institute of Aeronautics and Astronautics Absolute Orbit and Gravity Determination using Relative  

E-print Network

American Institute of Aeronautics and Astronautics 1 Absolute Orbit and Gravity Determination using a pair of Lunar orbiting spacecraft. I. Introduction he field of orbit determination is as old as Kepler and has reached a high state of maturity. A modern treatment of orbit determination is contained in a text

Psiaki, Mark L.

111

AIAA-98-4308 Autonomous LEO Orbit Determination From Magnetometer and Sun Sensor Data  

E-print Network

AIAA-98-4308 Autonomous LEO Orbit Determination From Magnetometer and Sun Sensor Data Mark L-accuracy autonomous orbit determination system. The system uses a batch filter to estimate the Keplerian orbital orbit determination systems. Traditional systems rely on ground-based range and range-rate data

Psiaki, Mark L.

112

ORBIT DETERMINATION WITH THE CUBED-SPHERE GRAVITY Brandon A. Jones, George H. Born  

E-print Network

AAS 10-237 ORBIT DETERMINATION WITH THE CUBED-SPHERE GRAVITY MODEL Brandon A. Jones, George H. Born singularity, and thus im- proves model reliability. This paper also discusses orbit determination improve- ments when utilizing this model. This orbit determination study utilized orbits comparable to the GRACE

Born, George

113

Two locations, two times, and the element set. [applicable to orbit determination of artificial satellites  

NASA Technical Reports Server (NTRS)

A robust analytical formulation is developed to apply classical initial orbital determination to artificial satellites whose locations are uncertain to about 1 cu km and separated in time by no more than 30 min. An analytical simplification reduces Gauss's method, iteration on the semilatus rectum, iteration on the true anomaly, and the Lambert-Euler technique, to the solution of a single equation in one unknown, instead of the usual coupled triplet of three equations in three unknowns. The method is demonstrated for all common artificial satellite orbits over a variety of time intervals between the two location vectors, and for a varied set of position and distance errors.

Taff, L. G.; Randall, P. M. S.

1985-01-01

114

How to Determine an Exomoon's Sense of Orbital Motion  

NASA Astrophysics Data System (ADS)

We present two methods to determine an exomoon's sense of orbital motion (SOM), one with respect to the planet's circumstellar orbit and one with respect to the planetary rotation. Our simulations show that the required measurements will be possible with the European Extremely Large Telescope (E-ELT). The first method relies on mutual planet-moon events during stellar transits. Eclipses with the moon passing behind (in front of) the planet will be late (early) with regard to the moon's mean orbital period due to the finite speed of light. This "transit timing dichotomy" (TTD) determines an exomoon's SOM with respect to the circumstellar motion. For the 10 largest moons in the solar system, TTDs range between 2 and 12 s. The E-ELT will enable such measurements for Earth-sized moons around nearby Sun-like stars. The second method measures distortions in the IR spectrum of the rotating giant planet when it is transited by its moon. This Rossiter-McLaughlin effect (RME) in the planetary spectrum reveals the angle between the planetary equator and the moon's circumplanetary orbital plane, and therefore unveils the moon's SOM with respect to the planet's rotation. A reasonably large moon transiting a directly imaged planet like ? Pic b causes an RME amplitude of almost 100 m s-1, about twice the stellar RME amplitude of the transiting exoplanet HD209458 b. Both new methods can be used to probe the origin of exomoons, that is, whether they are regular or irregular in nature.

Heller, René; Albrecht, Simon

2014-11-01

115

Precise Orbit Determination for a New Horizons KBO  

NASA Astrophysics Data System (ADS)

The New Horizons {NH} spacecraft is on its way to study the Pluto system during a flyby after which the spacecraft will be retargeted to one or more Kuiper Belt Objects {KBOs} to learn about small KBOs and the Kuiper Belt population. We are actively carrying out dedicated ground-based observations to identify a target for NH to flyby and continue to improve our analysis algorithms. To date, we have 28 discoveries including five objects that are long-range reconnaissance candidates, two that are pre-Pluto encounter observation candidates and two that current orbit predictions require about a factor of 2 more propellant than available for the targeting maneuver. Our searches are continuing in to 2013. Unfortunately, NH's trajectory line of site is within the galactic center {Sagittarius} making stellar confusion a major problem in obtaining precise astrometry and high precision orbits for these objects from the ground. HST's sensitivity, resolution and PSF stability are crucial components for determining precise orbits for these objects. We request 2 TOO orbits to be triggered in the event that a candidate object is found within the targetable region. These observations will provide the required high precision astrometry, will evaluate if the NH candidate is binary { 30%} and will make a preliminary color determination to assist in fly-by planning.

Benecchi, Susan

2013-10-01

116

Magnetospheric Multiscale (MMS) Mission Commissioning Phase Orbit Determination Error Analysis  

NASA Technical Reports Server (NTRS)

The Magnetospheric MultiScale (MMS) mission commissioning phase starts in a 185 km altitude x 12 Earth radii (RE) injection orbit and lasts until the Phase 1 mission orbits and orientation to the Earth-Sun li ne are achieved. During a limited time period in the early part of co mmissioning, five maneuvers are performed to raise the perigee radius to 1.2 R E, with a maneuver every other apogee. The current baseline is for the Goddard Space Flight Center Flight Dynamics Facility to p rovide MMS orbit determination support during the early commissioning phase using all available two-way range and Doppler tracking from bo th the Deep Space Network and Space Network. This paper summarizes th e results from a linear covariance analysis to determine the type and amount of tracking data required to accurately estimate the spacecraf t state, plan each perigee raising maneuver, and support thruster cal ibration during this phase. The primary focus of this study is the na vigation accuracy required to plan the first and the final perigee ra ising maneuvers. Absolute and relative position and velocity error hi stories are generated for all cases and summarized in terms of the ma ximum root-sum-square consider and measurement noise error contributi ons over the definitive and predictive arcs and at discrete times inc luding the maneuver planning and execution times. Details of the meth odology, orbital characteristics, maneuver timeline, error models, and error sensitivities are provided.

Chung, Lauren R.; Novak, Stefan; Long, Anne; Gramling, Cheryl

2009-01-01

117

Meteoroid and Orbital Debris Threats to NASA's Docking Seals: Initial Assessment and Methodology  

NASA Technical Reports Server (NTRS)

The Crew Exploration Vehicle (CEV) will be exposed to the Micrometeoroid Orbital Debris (MMOD) environment in Low Earth Orbit (LEO) during missions to the International Space Station (ISS) and to the micrometeoroid environment during lunar missions. The CEV will be equipped with a docking system which enables it to connect to ISS and the lunar module known as Altair; this docking system includes a hatch that opens so crew and supplies can pass between the spacecrafts. This docking system is known as the Low Impact Docking System (LIDS) and uses a silicone rubber seal to seal in cabin air. The rubber seal on LIDS presses against a metal flange on ISS (or Altair). All of these mating surfaces are exposed to the space environment prior to docking. The effects of atomic oxygen, ultraviolet and ionizing radiation, and MMOD have been estimated using ground based facilities. This work presents an initial methodology to predict meteoroid and orbital debris threats to candidate docking seals being considered for LIDS. The methodology integrates the results of ground based hypervelocity impacts on silicone rubber seals and aluminum sheets, risk assessments of the MMOD environment for a variety of mission scenarios, and candidate failure criteria. The experimental effort that addressed the effects of projectile incidence angle, speed, mass, and density, relations between projectile size and resulting crater size, and relations between crater size and the leak rate of candidate seals has culminated in a definition of the seal/flange failure criteria. The risk assessment performed with the BUMPER code used the failure criteria to determine the probability of failure of the seal/flange system and compared the risk to the allotted risk dictated by NASA's program requirements.

deGroh, Henry C., III; Nahra, Henry K.

2009-01-01

118

Meteoroid and Orbital Debris Threats to NASA's Docking Seals: Initial Assessment and Methodology  

NASA Technical Reports Server (NTRS)

The Crew Exploration Vehicle (CEV) will be exposed to the Micrometeoroid Orbital Debris (MMOD) environment in Low Earth Orbit (LEO) during missions to the International Space Station (ISS) and to the micrometeoroid environment during lunar missions. The CEV will be equipped with a docking system which enables it to connect to ISS and the lunar module known as Altair; this docking system includes a hatch that opens so crew and supplies can pass between the spacecrafts. This docking system is known as the Low Impact Docking System (LIDS) and uses a silicone rubber seal to seal in cabin air. The rubber seal on LIDS presses against a metal flange on ISS (or Altair). All of these mating surfaces are exposed to the space environment prior to docking. The effects of atomic oxygen, ultraviolet and ionizing radiation, and MMOD have been estimated using ground based facilities. This work presents an initial methodology to predict meteoroid and orbital debris threats to candidate docking seals being considered for LIDS. The methodology integrates the results of ground based hypervelocity impacts on silicone rubber seals and aluminum sheets, risk assessments of the MMOD environment for a variety of mission scenarios, and candidate failure criteria. The experimental effort that addressed the effects of projectile incidence angle, speed, mass, and density, relations between projectile size and resulting crater size, and relations between crater size and the leak rate of candidate seals has culminated in a definition of the seal/flange failure criteria. The risk assessment performed with the BUMPER code used the failure criteria to determine the probability of failure of the seal/flange system and compared the risk to the allotted risk dictated by NASA s program requirements.

deGroh, Henry C., III; Gallo, Christopher A.; Nahra, Henry K.

2009-01-01

119

Orbit determination and orbit control for the Earth Observing System (EOS) AM spacecraft  

NASA Astrophysics Data System (ADS)

Future NASA Earth Observing System (EOS) Spacecraft will make measurements of the earth's clouds, oceans, atmosphere, land and radiation balance. These EOS Spacecraft will be part of the NASA Mission to Planet Earth. This paper specifically addresses the EOS AM Spacecraft, referred to as 'AM' because it has a sun-synchronous orbit with a 10:30 AM descending node. This paper describes the EOS AM Spacecraft mission orbit requirements, orbit determination, orbit control, and navigation system impact on earth based pointing. The EOS AM Spacecraft will be the first spacecraft to use the TDRSS Onboard Navigation System (TONS) as the primary means of navigation. TONS flight software will process one-way forward Doppler measurements taken during scheduled TDRSS contacts. An extended Kalman filter will estimate spacecraft position, velocity, drag coefficient correction, and ultrastable master oscillator frequency bias and drift. The TONS baseline algorithms, software, and hardware implementation are described in this paper. TONS integration into the EOS AM Spacecraft Guidance, Navigation, and Control (GN&C) System; TONS assisted onboard time maintenance; and the TONS Ground Support System (TGSS) are also addressed.

Herberg, Joseph R.; Folta, David C.

1993-02-01

120

Orbit Determination Support for the Microwave Anisotropy Probe (MAP)  

NASA Technical Reports Server (NTRS)

The Microwave Anisotropy Probe (MAP) is a Medium Class Explorers (MIDEX) mission produced in partnership between Goddard Space Flight Center (GSFC) and Princeton University. The main science objective of the MAP mission is to produce an accurate full-sky map of the cosmic microwave background temperature fluctuations anisotropy. MAP was launched from the Cape Canaveral Air Force Station Complex 17 aboard a Delta II 7425-10 expendable launch vehicle at exactly 19:46:46.183 UTC on June 30, 2001. The spacecraft received a nominal direct insertion by the Delta into a 185 km circular orbit. MAP was then maneuvered into a sequence of phasing loops designed to set up a lunar swingby (gravity-assisted acceleration) of the spacecraft onto a transfer trajectory to a Lissajous orbit about the Earth-Sun L2 point. The mission duration is approximately 27 months with 3 to 4 months of transfer time to the final mission orbit about L2. The MAP transfer orbit consisted of 3.5 phasing loops: the first loop has a 7-day period, the second and third loops have a 9-day period, and the last half loop has a 4-day period as illustrated in Figure 1, which also indicates the placement of maneuvers. A Pfinal correction maneuver was performed 18 hours after the last perigee to more closely achieve the targeted lissajous orbit. The lunar encounter or swingby took place approximately 30 days after launch. After the lunar encounter, the spacecraft will cruise for approximately 120 days before it arrives at L2. A Mid-Course Correction (MCC) maneuver was executed seven days after the swingby to further refine the trajectory. Once the MAP satellite is injected into the L2 Lissajous orbit, it will perform occasional stationkeeping maneuvers to maintain the Lissajous orbit for a minimum of two years (and a goal of four years). Because of its complex orbital characteristics, the mission provided a unique challenge to orbit determination (OD) support in many orbital regimes. Extensive trajectory error covariance analysis was performed to predict ephemeris accuracy for the OD process using a Bayesian least-squares technique. The orbit determination error analysis is essential for maneuver planning and maneuver recovery study. Several tracking scenarios were investigated for each phase of the mission. This paper provides a summary of the premission trajectory covariance error analysis, as well as actual real-time OD results. The use and impact of the various tracking stations, systems, and measurements will be discussed. Details of the operational OD support and the inferred OD accuracy will be presented, and the results will be compared to the premission covariance analysis, In addition, there will be a discussion of the challenges presented to OD support including delta-Vs at apogee as well as perigee, and effects due to spacecraft attitude mode, in light of their implications to the OD accuracy and covariance analysis.

Truong, Son H.; Cuevas, Osvaldo O.; Slojkowski, Steven; Bauer, Frank H. (Technical Monitor)

2002-01-01

121

Orbit Determination Support for the Microwave Anisotropy Probe (MAP)  

NASA Technical Reports Server (NTRS)

THe microwave Anisotropy Probe (MAP) ia the second Medium Class Explorer (MIDEX) mission of the National Aeronautics and Space Administration (NASA). The main goal of the MAP observatory is to measure the temperature fluctuations, known as anisotropy, of the cosmic microwave background (CBG) radiation over the entire sky and to produce a map of the CMB anisotropies with an angular resolution of approximately 3 degrees. MAP was launched from the Cape Canaveral Air Force Station Complex 17 aboard a Delta II 7425-10 expendable launch vehicle at exactly 19:46:46.183 UTC on June 30, 20001. The spacecraft receiver a nominal direct insertion by the Delta expendable launch vehicle into a 185-km circular orbit with a 28.7 deg. inclination. MAP was than maneuvered into a sequence of phasing loops designed to set up a lunar gravity-assisted acceleration of the spacecraft onto a transfer trajectory to a lissajous orbit about the Earth-Sun L2 Lagrange point, about 1.5 million km from Earth. The science mission minimum lifetime is two years of observations at L2 with a desired lifetime of 4 years. The MAP transfer orbit consisted of 3.5 phasing loops.The MAP trajectory schematic all the way through L2 is shown. The first loop had a period of 7 days, the second and third loops were 10 days long, and the last half loop was 5 days. The periselene (i.e., lunar encounter or swingby) took place approximately 30 days after launch. After the periselene, the spacecraft cruised for approximately 60 days before it arrived in the vicinity of the L2 libration point. Two mid-course correction (MCC) maneuvers were performed to refine MAP's post-launch trajectory-one after periselene and one prior to arrival at vicinity of L2. Now that MAP is at its operational L2 lissajous orbit, the MAP satellite is commanded to perform occasional station-keeping (SK) maneuvers in order to maintain its orbit around L2. Because of its complex orbital characteristics, the mission provided a unique challenge to orbit determination (OD) support in many orbital regimes.

Truong, Son H.; Cuevas, Osvaldo O.; Slojkowski, Steven

2003-01-01

122

Improved DORIS accuracy for precise orbit determination and geodesy  

NASA Technical Reports Server (NTRS)

In 2001 and 2002, 3 more DORIS satellites were launched. Since then, all DORIS results have been significantly improved. For precise orbit determination, 20 cm are now available in real-time with DIODE and 1.5 to 2 cm in post-processing. For geodesy, 1 cm precision can now be achieved regularly every week, making now DORIS an active part of a Global Observing System for Geodesy through the IDS.

Willis, Pascal; Jayles, Christian; Tavernier, Gilles

2004-01-01

123

Enhanced orbit determination filter sensitivity analysis: Error budget development  

NASA Technical Reports Server (NTRS)

An error budget analysis is presented which quantifies the effects of different error sources in the orbit determination process when the enhanced orbit determination filter, recently developed, is used to reduce radio metric data. The enhanced filter strategy differs from more traditional filtering methods in that nearly all of the principal ground system calibration errors affecting the data are represented as filter parameters. Error budget computations were performed for a Mars Observer interplanetary cruise scenario for cases in which only X-band (8.4-GHz) Doppler data were used to determine the spacecraft's orbit, X-band ranging data were used exclusively, and a combined set in which the ranging data were used in addition to the Doppler data. In all three cases, the filter model was assumed to be a correct representation of the physical world. Random nongravitational accelerations were found to be the largest source of error contributing to the individual error budgets. Other significant contributors, depending on the data strategy used, were solar-radiation pressure coefficient uncertainty, random earth-orientation calibration errors, and Deep Space Network (DSN) station location uncertainty.

Estefan, J. A.; Burkhart, P. D.

1994-01-01

124

General Relativistic Initial Data for the Binary Black Hole / Neutron Star System in Quasicircular Orbit  

E-print Network

We present an algorithm for solving the general relativistic initial value equations for a corotating polytropic star in quasicircular orbit with a nonspinning black hole. The algorithm is used to obtain initial data for cases where the black hole mass is 1, 3, and 10 times larger than the mass of the star. By analyzing sequences of constant baryon mass, constant black hole mass initial data sets and carefully monitoring the numerical error, we find innermost stable circular orbit (ISCO) configuration for these cases. While these quasiequilibrium, conformally flat sequences of initial data sets are not true solutions of the Einstein equations (each set, however, solves the full initial value problem), and thus, we do not expect the ISCO configurations found here to be completely consistent with the Einstein equations, they will be used as convenient starting points for future numerical evolutions of the full 3+1 Einstein equations.

Mark Miller

2001-06-06

125

Position determination systems. [using orbital antenna scan of celestial bodies  

NASA Technical Reports Server (NTRS)

A system for an orbital antenna, operated at a synchronous altitude, to scan an area of a celestial body is disclosed. The antenna means comprises modules which are operated by a steering signal in a repetitive function for providing a scanning beam over the area. The scanning covers the entire area in a pattern and the azimuth of the scanning beam is transmitted to a control station on the celestial body simultaneous with signals from an activated ground beacon on the celestial body. The azimuth of the control station relative to the antenna is known and the location of the ground beacon is readily determined from the azimuth determinations.

Shores, P. W. (inventor)

1976-01-01

126

(42355) Typhon-Echidna: Scheduling Observations for Binary Orbit Determination  

E-print Network

We describe a strategy for scheduling astrometric observations to minimize the number required to determine the mutual orbits of binary transneptunian systems. The method is illustrated by application to Hubble Space Telescope observations of (42355) Typhon-Echidna, revealing that Typhon and Echidna orbit one another with a period of 18.971 +/- 0.006 days and a semimajor axis of 1628 +/- 29 km, implying a system mass of (9.49 +/- 0.52) x 10^17 kg. The eccentricity of the orbit is 0.526 +/- 0.015. Combined with a radiometric size determined from Spitzer Space Telescope data and the assumption that Typhon and Echidna both have the same albedo, we estimate that their radii are 76 +14/-16 and 42 +8/-9 km, respectively. These numbers give an average bulk density of only 0.44 +0.44/-0.17 g cm^-3, consistent with very low bulk densities recently reported for two other small transneptunian binaries.

W. M. Grundy; K. S. Noll; J. Virtanen; K. Muinonen; S. D. Kern; D. C. Stephens; J. A. Stansberry; H. F. Levison; J. R. Spencer

2008-04-15

127

An independent determination of Fomalhaut b's orbit and the dynamical effects on the outer dust belt  

NASA Astrophysics Data System (ADS)

Context. The nearby star Fomalhaut harbors a cold, moderately eccentric (e ~ 0.1) dust belt with a sharp inner edge near 133 au. A low-mass, common proper motion companion, Fomalhaut b (Fom b), was discovered near the inner edge and was identified as a planet candidate that could account for the belt morphology. However, the most recent orbit determination based on four epochs of astrometry over eight years reveals a highly eccentric orbit (e = 0.8 ± 0.1) that appears to cross the belt in the sky plane projection. Aims: We perform here a full orbital determination based on the available astrometric data to independently validate the orbit estimates previously presented. Adopting our values for the orbital elements and their associated uncertainties, we then study the dynamical interaction between the planet and the dust ring, to check whether the proposed disk sculpting scenario by Fom b is plausible. Methods: We used a dedicated MCMC code to derive the statistical distributions of the orbital elements of Fom b. Then we used symplectic N-body integration to investigate the dynamics of the dust belt, as perturbed by a single planet. Different attempts were made assuming different masses for Fom b. We also performed a semi-analytical study to explain our results. Results: Our results are in good agreement with others regarding the orbit of Fom b. We find that the orbit is highly eccentric, is close to apsidally aligned with the belt, and has a mutual inclination relative to the belt plane of <29° (67% confidence). If coplanar, this orbit crosses the disk. Our dynamical study then reveals that the observed planet could sculpt a transient belt configuration with a similar eccentricity to what is observed, but it would not be simultaneously apsidally aligned with the planet. This transient configuration only occurs a short time after the planet is placed on such an orbit (assuming an initially circular disk), a time that is inversely proportional to the planet's mass, and that is in any case much less than the 440 Myr age of the star. Conclusions: We constrain how long the observed dust belt could have survived with Fom b on its current orbit, as a function of its possible mass. This analysis leads us to conclude that Fom b is likely to have low mass, that it is unlikely to be responsible for the sculpting of the belt, and that it supports the hypothesis of a more massive, less eccentric planet companion Fomalhaut c.

Beust, H.; Augereau, J.-C.; Bonsor, A.; Graham, J. R.; Kalas, P.; Lebreton, J.; Lagrange, A.-M.; Ertel, S.; Faramaz, V.; Thébault, P.

2014-01-01

128

Orbit Determination with the two-body Integrals. II  

E-print Network

The first integrals of the Kepler problem are used to compute preliminary orbits starting from two short observed arcs of a celestial body, which may be obtained either by optical or radar observations. We write polynomial equations for this problem, that we can solve using the powerful tools of computational Algebra. An algorithm to decide if the linkage of two short arcs is successful, i.e. if they belong to the same observed body, is proposed and tested numerically. In this paper we continue the research started in [Gronchi, Dimare, Milani, 'Orbit determination with the two-body intergrals', CMDA (2010) 107/3, 299-318], where the angular momentum and the energy integrals were used. A suitable component of the Laplace-Lenz vector in place of the energy turns out to be convenient, in fact the degree of the resulting system is reduced to less than half.

Giovanni F. Gronchi; Davide Farnocchia; Linda Dimare

2011-01-24

129

Automated Precision Orbit Determination for TOPEX/Poseidon with GPS  

NASA Technical Reports Server (NTRS)

A highly automated GPS data processing system for the orbit determination of TOPEX/Poseidon is described. The orbit is recovered to an estimated accuracy of better than 4 cm in altitude, 6 cm crosstrack, and 11 cm down track. The RMS postfit residuals on the ionospherically calibrated carrier phase observable are less than 5 mm. The RMS difference over a 4.5-hour overlap period between two 30-hour data arcs is 1 cm in altitude, 5 cm cross track, and 4 cm down track. These results can be obtained within two days of onboard GPS data collection. Most of the data processing for a 30-hour arc of GPS data can be performed on a single workstation in less than 6 hours of CPU time. The estimation scenarios are explained, the automated data processing steps are described, and means to assess solution quality are discussed.

Wu, S. C.; Muellerschoen, R. J.; Bertiger, W. I.; Yunck, T. P.; Bar-Sever, Y. E.; Munson, T. N.

1993-01-01

130

Orbit determination covariance analysis for the Deep Space Program Science Experiment mission  

NASA Technical Reports Server (NTRS)

To define an appropriate orbit support procedure for the DSPSE mission, detailed permission orbit determination covariance analyses have been performed for the translunar and trans-Geographos mission phases. Preliminary analyses were also performed for the lunar mapping mission phase. These analyses are designed to assess the tracking patterns and the amount of tracking data needed to obtain orbit solutions of required accuracy for each mission phase and before and after each major orbit perturbation, such as orbit maneuvers and flybys of the Earth and Moon. In addition to operational orbit determination procedures, these analyses identify major error sources, estimate their contribution to orbital errors, and address possible strategies to reduce orbit determination error. For the lunar orbit phase, several lunar gravity error modeling approaches have been investigated. The covariance analysis results presented in this paper will serve as a guide for providing orbit determination support for the DSPSE mission.

Beckman, M.; Yee, C.; Lee, T.; Hoppe, M.; Oza, D.

1993-01-01

131

Orbit/Attitude Determination and Control for the UMRSAT Mission  

NASA Astrophysics Data System (ADS)

As satellite missions become increasingly complex, a need for accurate determination and control systems using low cost hardware arises. This is especially true for university satellite programs such as the University of Missouri - Rolla satellite design team, or UMR SAT. With limited resources, mission success relies on creative and innovative hardware and software designs. This paper describes the development of control algorithms that will be used onboard the UMR SAT satellite pair. Using novel attitude and orbit control techniques and magnetometer-only attitude determination, the mission can be accomplished with low cost COTS hardware. The UMR developed ?-D controller will be used to facilitate the attitude and formation control, and the ?-D filter will be used for orbit determination. The ?-D technique has been successfully applied to a wide variety of applications ranging from wing aeroelastic flutter suppression to hit-to-kill missile autopilot design to reusable launch vehicle control. The results of each application have been very promising and show the potential improvement over pre-existing control techniques offered by the ?-D method. Along with software development, this paper also provides high fidelity simulations of the determination and control system are presented to demonstrate the effectiveness of the algorithms.

Dancer, M. W.; Searcy, J. D.

2008-08-01

132

Precise Orbit Determination for a New Horizons KBO  

NASA Astrophysics Data System (ADS)

The New Horizons (NH) spacecraft will flyby the Pluto system next summer, after this the spacecraft will be retargeted to one or more Kuiper Belt Objects (KBOs) to learn about the remnant material from our outer solar system's formation. We are actively carrying out dedicated ground-based observations to identify a target for NH to flyby and continue to improve our analysis algorithms. To date, we have 52 discoveries including five objects that are long-range reconnaissance candidates, and two that current orbit predictions require about a factor of 2 more propellant than is available for the encounter maneuver. Our searches are continuing in to 2014 and we anticipate as many as 2 objects that will require high precision HST imaging. Unfortunately, NH's trajectory line of site is within the galactic center (Sagittarius) making stellar confusion a major problem in recovering these objects from the ground to obtain precise astrometry and high precision orbits. HST's sensitivity, resolution and PSF stability are crucial components for the success of the NH Kuiper belt mission component. We are requesting 4 TOO orbits to be triggered when a candidate object is found within the targetable region. These observations will provide the required high precision astrometry required for targeting, will evaluate if the NH candidate is binary (~30%) and will make a preliminary color determination to assist in long or short range encounter planning.

Benecchi, Susan

2014-10-01

133

Application of semianalytical satellite theories to precision orbit determination  

NASA Technical Reports Server (NTRS)

Those factors which limit the usefulness of current implementations of the semianalytical approach are discussed. Numerical and analytical enhancements to the semianalytical approach are considered. A simple mathematical model is provided to estimate the computational speed of a semianalytical theory employing the suggested enhancements. The model can factor in current experience with semianalytical theories (integration stepsizes, quadrature orders, speed of recursive formulations, etc.) and the characteristics of the particular output requirement (observation span (or orbit determination interval), observation rate, observation model, etc.). Comparisons with numerical integration are suggested.

Cefola, P. J.

1978-01-01

134

Orbit Determination of Close Binary Systems using Lucky F. M. Rica1,2*  

E-print Network

Orbit Determination of Close Binary Systems using Lucky Imaging F. M. Rica1,2* , R. Barrena3,4 , G. The stellar mass is determined from orbital information which can be obtained using a set of astrometric measures. To determine the stellar masses accurately, high-quality orbital parameters and trigonometrical

135

Orbit Determination Using TDMA Radio Navigation Data with Implicit Measurement Times  

E-print Network

Orbit Determination Using TDMA Radio Navigation Data with Implicit Measurement Times Ryan C. Dougherty and Mark L. Psiaki Cornell University, Ithaca, New York, 14853-7501 An orbit determination Kalman measurement. This algorithm will enable precise orbit determination of satellites broadcasting TDMA signals

Psiaki, Mark L.

136

AIAA-98-4560 AUTONOMOUS ORBIT DETERMINATION FOR TWO SPACECRAFT FROM RELATIVE POSITION  

E-print Network

AIAA-98-4560 AUTONOMOUS ORBIT DETERMINATION FOR TWO SPACECRAFT FROM RELATIVE POSITION MEASUREMENTS and analyzed to autonomously determine the orbits of 2 spacecraft based on measurements of the relative-precision autonomous orbit determination for systems that cannot be dependent on signals from the GPS constellation

Psiaki, Mark L.

137

Initial Mars Orbiter Laser Altimeter (MOLA) Measurements of the Mars Surface and Atmosphere  

NASA Technical Reports Server (NTRS)

The Mars Orbiter Laser Altimeter (MOLA) has made an initial set of measurements of the Mars surface and atmosphere. As of this writing 27 orbital passes have been completed, starting Sept. 15, 1997 on orbit Pass 3 and orbits 20-36 and beginning again on March 27, 1998 for orbit passes 203 - 212. The lidar is working well in Mars orbit, and its data show contiguous measurement profiles of the Mars surface to its maximum range of 786 km, an average pulse detection rate of > 99% under clear atmospheric conditions, and < 1 m range resolution. MOLA has profiled the shape and heights of a variety of interesting Mars surface features, including Olympus Mons, the flat northern plains of Mars, Valles Marineris and the northern polar ice cap. It has also detected and profiled a series of cloud layers which occur near the edge of the polar cap and near 60-70 deg N latitude. This is the first time clouds around another planet have been measured using lidar.

Abshire, James B.; Sun, Xiaoli; Afzal, Robert S.

1998-01-01

138

Improved Space Object Orbit Determination Using CMOS Detectors  

NASA Astrophysics Data System (ADS)

CMOS-sensors, or in general Active Pixel Sensors (APS), are rapidly replacing CCDs in the consumer camera market. Due to significant technological advances during the past years these devices start to compete with CCDs also for demanding scientific imaging applications, in particular in the astronomy community. CMOS detectors offer a series of inherent advantages compared to CCDs, due to the structure of their basic pixel cells, which each contains their own amplifier and readout electronics. The most prominent advantages for space object observations are the extremely fast and flexible readout capabilities, feasibility for electronic shuttering and precise epoch registration, and the potential to perform image processing operations on-chip and in real-time. The major challenges and design drivers for ground-based and space-based optical observation strategies have been analyzed. CMOS detector characteristics were critically evaluated and compared with the established CCD technology, especially with respect to the above mentioned observations. Similarly, the desirable on-chip processing functionalities which would further enhance the object detection and image segmentation were identified. Finally, we simulated several observation scenarios for ground- and space-based sensor by assuming different observation and sensor properties. We will introduce the analyzed end-to-end simulations of the ground- and space-based strategies in order to investigate the orbit determination accuracy and its sensitivity which may result from different values for the frame-rate, pixel scale, astrometric and epoch registration accuracies. Two cases were simulated, a survey using a ground-based sensor to observe objects in LEO for surveillance applications, and a statistical survey with a space-based sensor orbiting in LEO observing small-size debris in LEO. The ground-based LEO survey uses a dynamical fence close to the Earth shadow a few hours after sunset. For the space-based scenario a sensor in a sun-synchronous LEO orbit, always pointing in the anti-sun direction to achieve optimum illumination conditions for small LEO debris, was simulated. For the space-based scenario the simulations showed a 20 130 % improvement of the accuracy of all orbital parameters when varying the frame rate from 1/3 fps, which is the fastest rate for a typical CCD detector, to 50 fps, which represents the highest rate of scientific CMOS cameras. Changing the epoch registration accuracy from a typical 20.0 ms for a mechanical shutter to 0.025 ms, the theoretical value for the electronic shutter of a CMOS camera, improved the orbit accuracy by 4 to 190 %. The ground-based scenario also benefit from the specific CMOS characteristics, but to a lesser extent.

Schildknecht, T.; Peltonen, J.; Sännti, T.; Silha, J.; Flohrer, T.

2014-09-01

139

Determination of the inflight OTF of orbital earth resources sensors  

NASA Technical Reports Server (NTRS)

There are no author-identified significant results in this report. A technique has been investigated that is particularly applicable to evaluation of earth-orbiting multispectral sensors. In all programs employing such sensors, simultaneous underflight photography from aircraft is made during passes of the spacecraft. To evaluate the spacecraft imagery, the two sets of photographs are scanned and digitized with a microdensitometer. The data are then Fourier analyzed, and the spatial frequency spectra is calculated. The spatial frequencies in the underflight trace are scaled to those in the spacecraft trace, and the ratio of the spectra gives the in-flight optical transfer function (OTF) for the orbiting sensor. The method has been applied to an Apollo 9 frame and the sensor OTF has been calculated. The results are good enough to encourage use of the technique and to indicate the accuracies required of the various measurements involved in determining in-flight sensor OTF by this method. A technique for determining correct scan registration and scaling between the two sets of imagery and a promising approach to noise reduction, in the form of weighted averaging of OTF's, are discussed.

Slater, P. N. (principal investigator); Schowengerdt, R. A.

1972-01-01

140

Filter parameter tuning analysis for operational orbit determination support  

NASA Technical Reports Server (NTRS)

The use of an extended Kalman filter (EKF) for operational orbit determination support is being considered by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD). To support that investigation, analysis was performed to determine how an EKF can be tuned for operational support of a set of earth-orbiting spacecraft. The objectives of this analysis were to design and test a general purpose scheme for filter tuning, evaluate the solution accuracies, and develop practical methods to test the consistency of the EKF solutions in an operational environment. The filter was found to be easily tuned to produce estimates that were consistent, agreed with results from batch estimation, and compared well among the common parameters estimated for several spacecraft. The analysis indicates that there is not a sharply defined 'best' tunable parameter set, especially when considering only the position estimates over the data arc. The comparison of the EKF estimates for the user spacecraft showed that the filter is capable of high-accuracy results and can easily meet the current accuracy requirements for the spacecraft included in the investigation. The conclusion is that the EKF is a viable option for FDD operational support.

Dunham, J.; Cox, C.; Niklewski, D.; Mistretta, G.; Hart, R.

1994-01-01

141

Modification of an impulse-factoring orbital transfer technique to account for orbit determination and maneuver execution errors  

NASA Technical Reports Server (NTRS)

A method has previously been developed to satisfy terminal rendezvous and intermediate timing constraints for planetary missions involving orbital operations. The method uses impulse factoring in which a two-impulse transfer is divided into three or four impulses which add one or two intermediate orbits. The periods of the intermediate orbits and the number of revolutions in each orbit are varied to satisfy timing constraints. Techniques are developed to retarget the orbital transfer in the presence of orbit-determination and maneuver-execution errors. Sample results indicate that the nominal transfer can be retargeted with little change in either the magnitude (Delta V) or location of the individual impulses. Additonally, the total Delta V required for the retargeted transfer is little different from that required for the nominal transfer. A digital computer program developed to implement the techniques is described.

Kibler, J. F.; Green, R. N.; Young, G. R.; Kelly, M. G.

1974-01-01

142

IAC-14-A6.9.4 Orbit Determination of Space Debris Using a Bi-static Radar Configuration  

E-print Network

IAC-14-A6.9.4 Orbit Determination of Space Debris Using a Bi-static Radar Configuration (i.e. from measurement and data acquisition to orbit determination) is described. The Orbit, tailored orbit determination algorithms have to be developed. The orbit determination algorithm receives

143

Geocoding of SAR Image Using the Orbit and Attitude Determination of RADARSAT  

NASA Astrophysics Data System (ADS)

The Synthetic Aperture Radar (SAR) image and the Digital Elevation Model (DEM) of an target area are put into use to generate three dimensional image map. An method of image map generation is explained. The orbit and attitude determination of satellite makes it possible to model signal acquisition configuration precisely, which is a key to mapping image coordinates to geographic coordinates of concerned area. An application is made to RADARSAT in the purpose of testing its validity. To determine the orbit, zero Doppler range is used. And to determine the attitude, Doppler centroid frequency, which is the frequency observed when target is in the center of antenna's view, is used. Conventional geocoding has been performed on the basis of direct method(mapping image coordinates to geographic coordinates), but in this research the inverse method (mapping from geographic coordinates to image coordinates) is taken. This paper shows that precise signal acquisition modeling based on the orbit and attitude determination of satellite as a platform leads to a satellite-centered accurate geocoding process. It also shows how to model relative motion between spaceborne radar and target. And the relative motion is described in ECIC (earth-centered initial coordinates) using Doppler equation and signal acquisition geometry.

So, Jin Wook; Choi, Kyu-Hong; Won, Joong-Sun

1998-06-01

144

EMPIRICALLY DETERMINED RESPONSE MATRICES FOR ON-LINE ORBIT AND ENERGY CORRECTION AT THOMAS JEFFERSON  

E-print Network

EMPIRICALLY DETERMINED RESPONSE MATRICES FOR ON-LINE ORBIT AND ENERGY CORRECTION AT THOMAS this feedback system to use empirically determined response matrices whereby the software introduces small orbit Accelerator Facility's (CEBAF) electron beam orbit and energy. Previous incarnations of these loops used

145

Attitude determination and orbital estimation using Earth position and magnetic field vector measurements  

Microsoft Academic Search

An attitude determination routine based on geometric relations coupled with an orbital position estimator is designed. The proposed determination algorithm utilizes Earth position and magnetic field vector measurements. Orbital position data is provided by an extended Kalman filter (EKF) estimation of the Keplerian orbital elements. This estimator uses only measurements of the magnitude of the Earth's magnetic field. Coupling the

Brogan Page Morton; K. Koprubasi; M.-W. L. Thein

2004-01-01

146

Orbits  

NSDL National Science Digital Library

This Topic in Depth explores the Web's offerings on Orbits. The first site is offered by Northwestern University and asks: What is an orbit? (1 ). The site answers questions such as What causes an orbit to happen?, What is a satellite?, What travels in an orbit?, and Are there orbits within orbits?. A great starting site for this subject, visitors should come away with a broad and clear description of the topic. The second site, called Orbit Diagrams (2 ) is provided by the Harvard-Smithsonian Center for Astrophysics. The diagrams are "intended to aid in the visualization of the three-dimensional nature of the orbits and how they are orientated with respect to the orbit of the earth." Next, from the University of Wisconsin-Madison Department of Astronomy comes the Moon Phases (3 ) interactive Web site. Users are able to animate the moon's orbit in various phases and views as well as learn all the names of the phases. The fourth site is another virtual visualization tool provided by NASA's Near Earth Object Program called Orbits (4 ). The site lets users enter the designation or name of any asteroid or comet and then view the three-dimensional orbit of that object. The next site, maintained by the Conservation, Astronomy, Physics and Soaring Page, is called Satellite Orbits - Gravitational Assist from Planets (5 ). The site contains information on Kepler's Laws, which apply to elliptical orbits involving two bodies, hyperbolic orbits, relative motion, and the gravitational sphere of influence. The sixth site is an educational lesson provided by Dr. Richard L. Bowman of Bridgewater College called Planetary Orbit Exercise (6 ). Students are given information on Keplar's Laws of Planetary Motion, a list of definitions, links to outside sites for additional information, and then several questions to answer. The Planetary Physical Data (7 ) page is part of the larger Smithsonian Center for Earth and Planetary Studies Web site. Visitors will find a list of planets along with various information such as their relative sidereal period of orbit, mean orbital velocity, orbital eccentricity, and much more. The last site related to orbits is an educational activity provided by the Physics Classroom called Circular Motion and Planetary Motion (8 ). Four lessons are presented including Motion Characteristics for Circular Motion, Applications of Circular Motion, Universal Gravitation, and Planetary and Satellite Motion. Each contain clear and well written descriptions along with all the necessary information for successful completion.

Brieske, Joel A.

147

Determination of the GOCE Satellite Orbit Sensitivity Under the Influence of Perturbing Forces  

NASA Astrophysics Data System (ADS)

The work contains the results of research into the simulated orbit of GOCE satellite. Satellite accelerations due to atmospheric drag, the gravitation of the Moon, the Sun, and the planets, the Earth tides, the ocean tides, the solar radiation pressure, the reflected solar radiation pressure and the relativity effects were computed. Besides the reference orbit (i.e. the orbit as close as possible to the GOCE planned orbit), the various variants of the satellite orbit (called the modified reference orbits - with different motion models) were obtained. The motion models contained the forces determining the satellite motion. For the orbital computations, the Cowell numerical integration of the eighths order was used. The geopotential was described by means of the EGM96 model. In order to obtain the influence of the aforementioned forces on the GOCE orbit, the percentage contributions of the accelerations due to these forces in the sum of all accelerations were computed. The maximum values of the mentioned accelerations were computed for the GOCE orbit variant with the motion model containing all forces given above. These values were compared with the measurement error of the linear accelerations by the GOCE satellite control system. The comparison between the reference orbit and the computed variants of the orbit was performed. In order to perform this comparison, the distances between the satellite position in the reference orbit and the satellite position in the given modified reference orbit (i.e. in a given orbit variant) were determined. These distances were compared with the total error of the GOCE satellite position determination. The orbital arc length, for which the selected forces can be neglected in the satellite motion model, were determined from this comparison. For these orbital arc lengths, the distance between the satellite position in the reference orbit and the satellite position in the given modified reference orbit is less or equal to the total error of the GOCE satellite position determination.

Boboj?, A.; Dro?yner

148

Cassini Orbit Determination Performance (July 2008 - December 2011)  

NASA Technical Reports Server (NTRS)

This paper reports on the orbit determination performance for the Cassini spacecraft from July 2008 to December 2011. During this period, Cassini made 85 revolutions around Saturn and had 52 close satellite encounters. 35 of those were with the massive Titan, 13 with the small, yet interesting, Enceladus as well as 2 with Rhea and 2 with Dione. The period also includes 4 double encounters, where engineers had to plan the trajectory for two close satellite encounters within days of each other at once. Navigation performance is characterized by ephemeris errors relative to in-flight predictions. Most Titan encounters 3-dimensional results are within a 1.5 formal sigma, with a few exceptions, mostly attributable to larger maneuver execution errors. Results for almost all other satellite encounter reconstructions are less than 3 sigma from their predictions. The errors are attributable to satellite ephemerides errors and in some cases to maneuver execution errors.

Pelletier, Frederic J.; Antreasian, Peter; Ardalan, Shadan; Buffington, Brent; Criddle, Kevin; Ionasescu, Rodica; Jacobson, Robert; Jones, Jeremy; Nandi, Sumita; Nolet, Simon; Parcher, Daniel; Roth, Duane; Smith, Jonathon; Thompson, Paul

2012-01-01

149

13 Years of TOPEX/POSEIDON Precision Orbit Determination and the 10-fold Improvement in Expected Orbit Accuracy  

NASA Technical Reports Server (NTRS)

Launched in the summer of 1992, TOPEX/POSEIDON (T/P) was a joint mission between NASA and the Centre National d Etudes Spatiales (CNES), the French Space Agency, to make precise radar altimeter measurements of the ocean surface. After the remarkably successful 13-years of mapping the ocean surface T/P lost its ability to maneuver and was de-commissioned January 2006. T/P revolutionized the study of the Earth s oceans by vastly exceeding pre-launch estimates of surface height accuracy recoverable from radar altimeter measurements. The precision orbit lies at the heart of the altimeter measurement providing the reference frame from which the radar altimeter measurements are made. The expected quality of orbit knowledge had limited the measurement accuracy expectations of past altimeter missions, and still remains a major component in the error budget of all altimeter missions. This paper describes critical improvements made to the T/P orbit time series over the 13-years of precise orbit determination (POD) provided by the GSFC Space Geodesy Laboratory. The POD improvements from the pre-launch T/P expectation of radial orbit accuracy and Mission requirement of 13-cm to an expected accuracy of about 1.5-cm with today s latest orbits will be discussed. The latest orbits with 1.5 cm RMS radial accuracy represent a significant improvement to the 2.0-cm accuracy orbits currently available on the T/P Geophysical Data Record (GDR) altimeter product.

Lemoine, F. G.; Zelensky, N. P.; Luthcke, S. B.; Rowlands, D. D.; Beckley, B. D.; Klosko, S. M.

2006-01-01

150

32 CFR 286.23 - Initial determinations.  

Code of Federal Regulations, 2010 CFR

...request or arrange for an alternative time frame shall be considered a factor in determining...submitter notification and subsequent analysis is required. The proposal shall...proposal itself. Submitter notice, and analysis as appropriate, are required for...

2010-07-01

151

32 CFR 286.23 - Initial determinations.  

Code of Federal Regulations, 2011 CFR

...request or arrange for an alternative time frame shall be considered a factor in determining...submitter notification and subsequent analysis is required. The proposal shall...proposal itself. Submitter notice, and analysis as appropriate, are required for...

2011-07-01

152

The Molecular Orbital Theory of Chemical Valency. I. The Determination of Molecular Orbitals  

Microsoft Academic Search

In the molecular orbital theory of valency the electrons are assigned to the whole molecule rather than to atoms or to other localized parts. While the method has advantages in dealing with the properties of a molecule as a whole, such as its energy states, the extension of each orbital over the molecular framework is a disadvantage when dealing with

John Lennard-Jones

1949-01-01

153

Initial On-Orbit Radiometric Calibration of the Suomi NPP VIIRS Reflective Solar Bands  

NASA Technical Reports Server (NTRS)

The on-orbit radiometric response calibration of the VISible/Near InfraRed (VISNIR) and the Short-Wave InfraRed (SWIR) bands of the Visible/Infrared Imager/Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (NPP) satellite is carried out through a Solar Diffuser (SD). The transmittance of the SD screen and the SD's Bidirectional Reflectance Distribution Function (BRDF) are measured before launch and tabulated, allowing the VIIRS sensor aperture spectral radiance to be accurately determined. The radiometric response of a detector is described by a quadratic polynomial of the detector?s digital number (dn). The coefficients were determined before launch. Once on orbit, the coefficients are assumed to change by a common factor: the F-factor. The radiance scattered from the SD allows the determination of the F-factor. In this Proceeding, we describe the methodology and the associated algorithms in the determination of the F-factors and discuss the results.

Lei, Ning; Wang, Zhipeng; Fulbright, Jon; Lee, Shihyan; McIntire, Jeff; Chiang, Vincent; Xiong, Jack

2012-01-01

154

Initial elementary processes in tetrafluoroethylene plasma: An ab initio molecular orbital study  

NASA Astrophysics Data System (ADS)

Initial elementary processes in tetrafluoroethylene plasma are studied by using an ab initio molecular orbital method. The energy-surfaces at excited states are obtained by the Hartree-Fock method with a double zeta basis set, plus Rydberg orbitals. A ?-?* transition is low-lying both at singlet and triplet excited states. Vinyl-polymerization-type reactions are expected in the presence of some radical species via these transitions. The C=C bond cleaves via a triplet ?-?* transition to form CF2. The predicted elementary processes via these states are compatible with experimental results that C2F4* and CF2 are primary precursors. No excited states that bring about a C—F bond cleavage are obtained within 10 eV of the ground state. As a path for a C—F bond cleavage, a dissociative electron attachment process is found in a low energy region. This process is considered to be important for producing fluorine anions.

Sato, Kota; Komatsu, Toru; Iwabuchi, Susumu

1993-12-01

155

The direct determination of Brueckner orbitals with application to the H 2 molecule  

Microsoft Academic Search

An iterative procedure is presented which allows for the direct determination of approximate Brueckner orbitals for small atomic and molecular systems. Starting from the Hartree-Fock determinant one first determines pair natural orbitals (PNOs) of independent electron pairs in the HF-field of the remaining electrons. The use of the generalized Brillouin-theorem then leads to an approximate Brueckner orbital for each electron

Volker Staemmler; Martin Jungen

1972-01-01

156

When is a group action determined by its orbit structure?  

Microsoft Academic Search

We present a simple approach to questions of topological orbit equivalence for actions of countable groups. For example, for any action of a countable group GG on a topological manifold where the fixed sets for any element are contained in codimension two submanifolds, every orbit equivalence is equivariant. Even in the presence of larger fixed sets, for actions preserving rigid

David Fisher; Kevin Whyte

2003-01-01

157

Black Hole Mass Determinations From Orbit Superposition Models are Reliable  

Microsoft Academic Search

We show that orbit-superposition dynamical models (Schwarzschild's method) provide reliable estimates of nuclear black hole masses and errors when constructed from adequate orbit libraries and kinematic data. We thus rebut two recent papers that argue that BH masses obtained from this method are unreliable. These papers claim to demonstrate that the range of allowable BH masses derived from a given

Douglas Richstone; Karl Gebhardt; Monique Aller; Ralf Bender; Gary Bower; Alan Dressler; S. M. Faber; Alexei V. Filippenko; Richard Green; Luis C. Ho; John Kormendy; Tod R. Lauer; John Magorrian; Jason Pinkney; Christos Siopis; Scott Tremaine

2004-01-01

158

Paul SWATSCHINA: Dynamic and ReducedDynamic LEO Orbit Determination (completed in October 2009)  

E-print Network

Paul SWATSCHINA: Dynamic and ReducedDynamic LEO Orbit Determination (completed in October 2009 of the observations, which leads to a considerably improved precise orbit determination. With the planned additional) The satellites CHAMP and GRACE belong to a series of dedicated satellite missions for the precise determination

Schuh, Harald

159

Determining the eccentricity of the Moon's orbit without a telescope  

NASA Astrophysics Data System (ADS)

Prior to the invention of the telescope many astronomers worked out models of the motion of the Moon to predict the position of the Moon in the sky. These geometrical models implied a certain range of distances of the Moon from Earth. Ptolemy's most quoted model predicted that the Moon was nearly twice as far away at apogee than at perigee. Measurements of the angular size of the Moon were within the capabilities of pretelescopic astronomers. Such measurements could have helped refine the models of the motion of the Moon, but hardly anyone seems to have made any measurements that have come down to us. We use a piece of cardboard with a small hole in it which slides up and down a yardstick to show that it is possible to determine the eccentricity ?~0.039+/-0.006 of the Moon's orbit. A typical measurement uncertainty of the Moon's angular size is +/-0.8 arc min. Because the Moon's angular size ranges from 29.4 to 33.5 arc min, carefully taken naked eye data are accurate enough to demonstrate periodic variations of the Moon's angular size.

Krisciunas, Kevin

2010-08-01

160

An analytic development of orbit determination for a distant, planetary orbiter  

NASA Technical Reports Server (NTRS)

With the advent of the Mariner '71 Mission, NASA has been sending spacecraft to orbit various distant bodies within the solar system. At present, there is still no adequate theory describing the inherent state estimation accuracy, based on two-way, coherent range-rate data. It is the purpose of this article to lay the groundwork for a general elliptic theory, and in addition to provide an analytic solution for the special case of circular orbits. It is shown that circular orbits about distant planets may suffer singularities in over-all position error estimation. These singularities are due to orbit inclination, placement of the line-of-nodes, and insignificant cross-velocity at the start and end of retrograde motion when orbiting a superior planet. Even though these conclusions appear to yield poor state estimation, one should not be unduly alarmed inasmuch as the stated conditions for singularity are not maintained for extended periods during typical mission scenarios. However, mission analysts should be aware of these potential pitfalls and realize that spuriously large results for circular orbiters can be obtained and are not the result of incorrect assumptions or faulty software. The general elliptic problem appears so involved that analytic inversion at this time is just not feasible, and in any case the resulting expression for the position error would likely be so lengthy that any understanding would be lost in the maze.

Russell, R. K.; Thurman, S. W.

1989-01-01

161

A sub-determinant approach for pseudo-orbit expansions of spectral determinants in quantum maps and quantum graphs  

E-print Network

We study implications of unitarity for pseudo-orbit expansions of the spectral determinants of quantum maps and quantum graphs. In particular, we advocate to group pseudo-orbits into sub-determinants. We show explicitly that the cancellation of long orbits is elegantly described on this level and that unitarity can be built in using a simple sub-determinant identity which has a non-trivial interpretation in terms of pseudo-orbits. This identity yields much more detailed relations between pseudo orbits of different length than known previously. We reformulate Newton identities and the spectral density in terms of sub-determinant expansions and point out the implications of the sub-determinant identity for these expressions. We analyse furthermore the effect of the identity on spectral correlation functions such as the auto-correlation and parametric cross correlation functions of the spectral determinant and the spectral form factor.

Daniel Waltner; Sven Gnutzmann; Gregor Tanner; Klaus Richter

2013-05-30

162

The binary Asteroid 22 Kalliope: Linus orbit determination on the basis of speckle interferometric observations  

NASA Astrophysics Data System (ADS)

In this paper we present the orbital elements of Linus satellite of 22 Kalliope asteroid. Orbital element determination is based on the speckle interferometry data obtained with the 6-m BTA telescope operated by SAO RAS. We processed 9 accurate positions of Linus orbiting around the main component of 22 Kalliope between 10 and 16 December, 2011. In order to determine the orbital elements of the Linus we have applied the direct geometric method. The formal errors are about 5 mas. This accuracy makes it possible to study the variations of the Linus orbital elements influenced by different perturbations over the course of time. Estimates of six classical orbital elements, such as the semi-major axis of the Linus orbit a = 1109 ± 6 km, eccentricity e = 0.016 ± 0.004, inclination i = 101° ± 1° to the ecliptic plane and others, are presented in this work.

Sokova, I. A.; Sokov, E. N.; Roschina, E. A.; Rastegaev, D. A.; Kiselev, A. A.; Balega, Yu. Yu.; Gorshanov, D. L.; Malogolovets, E. V.; Dyachenko, V. V.; Maksimov, A. F.

2014-07-01

163

Orbit Determination Accuracy Analysis of the Magnetospheric Multiscale Mission During Perigee Raise  

NASA Technical Reports Server (NTRS)

The Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF) will provide orbit determination and prediction support for the Magnetospheric Multiscale (MMS) mission during the mission's commissioning period. The spacecraft will launch into a highly elliptical Earth orbit in 2015. Starting approximately four days after launch, a series of five large perigee-raising maneuvers will be executed near apogee on a nearly every-other-orbit cadence. This perigee-raise operations concept requires a high-accuracy estimate of the orbital state within one orbit following the maneuver for performance evaluation and a high-accuracy orbit prediction to correctly plan and execute the next maneuver in the sequence. During early mission design, a linear covariance analysis method was used to study orbit determination and prediction accuracy for this perigee-raising campaign. This paper provides a higher fidelity Monte Carlo analysis using the operational COTS extended Kalman filter implementation that was performed to validate the linear covariance analysis estimates and to better characterize orbit determination performance for actively maneuvering spacecraft in a highly elliptical orbit. The study finds that the COTS extended Kalman filter tool converges on accurate definitive orbit solutions quickly, but prediction accuracy through orbits with very low altitude perigees is degraded by the unpredictability of atmospheric density variation.

Pachura, Daniel A.; Vavrina, Matthew A.; Carpenter, J. Russell; Wright, Cinnamon A.

2014-01-01

164

Orbit Determination Accuracy Analysis of the Magnetospheric Multiscale Mission During Perigee Raise  

NASA Technical Reports Server (NTRS)

The Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF) will provide orbit determination and prediction support for the Magnetospheric Multiscale (MMS) mission during the missions commissioning period. The spacecraft will launch into a highly elliptical Earth orbit in 2015. Starting approximately four days after launch, a series of five large perigee-raising maneuvers will be executed near apogee on a nearly every-other-orbit cadence. This perigee-raise operations concept requires a high-accuracy estimate of the orbital state within one orbit following the maneuver for performance evaluation and a high-accuracy orbit prediction to correctly plan and execute the next maneuver in the sequence. During early mission design, a linear covariance analysis method was used to study orbit determination and prediction accuracy for this perigee-raising campaign. This paper provides a higher fidelity Monte Carlo analysis using the operational COTS extended Kalman filter implementation that was performed to validate the linear covariance analysis estimates and to better characterize orbit determination performance for actively maneuvering spacecraft in a highly elliptical orbit. The study finds that the COTS extended Kalman filter tool converges on accurate definitive orbit solutions quickly, but prediction accuracy through orbits with very low altitude perigees is degraded by the unpredictability of atmospheric density variation.

Pachura, Daniel A.; Vavrina, Matthew A.; Carpenter, J. R.; Wright, Cinnamon A.

2014-01-01

165

A determination of the orbit of GX 301-2  

Microsoft Academic Search

The pulse phase of GX 301-2(4U 1223-62) was tracked for 30 days with the SAS 3 satellite during 1979 January and February. It is suggested that most of the observed changes in pulse period are the result of Doppler shifts in a binary orbit, as opposed to changes in the intrinsic pulse period alone. The SAS 3 data allow orbital

R. Kelley; S. Rappaport; R. Petre

1980-01-01

166

The three-dimensional general three-body problem: Determination of periodic orbits  

Microsoft Academic Search

The three-dimensional general three-body problem is formulated suitably for the numerical determination of periodic orbits either directly or by continuation from the three-dimensional periodic orbits of the restricted problem. The symmetry properties of the equations of motion are established and the algorithms for the numerical determination of families of periodic orbits are outlined. A normalization scheme based on the concept

V. V. Markellos

1980-01-01

167

Determining the Eccentricity of the Moon's Orbit without a Telescope  

NASA Astrophysics Data System (ADS)

Ancient Greek astronomers knew that Moon's distance from the Earth was not constant. Ptolemy's model of the Moon's motion implied that the Moon ranged in distance from 33 to 64 Earth radii. This implied that its angular size ranged nearly a factor of two. Tycho Brahe's model of the Moon's motion implied a smaller distance range, some ±3 percent at syzygy. However, the ancient and Renaissance astronomers are notably silent on the subject of measuring the angular size of the Moon as a check on the implied range of distance from their models of the position of the Moon. Using a quarter-inch hole in a piece of cardboard that slides along a yardstick, we show that pre-telescopic astronomers could have measured an accurate mean value of the angular size of the Moon, and that they could have determined a reasonably accurate value of the eccentricity of the Moon's orbit. The principal calibration for each observer is to measure the apparent angular diameter of a 91 mm disk viewed at a distance of 10 meters, giving a true angular size of 31.3 arcmin (the Moon's mean angular size). Because the sighting hole is not much bigger than the size of one's pupil, each observer obtains a personal correction factor with which to scale the raw measures. If one takes data over the course of 7 lunations (7.5 anomalistic months), any systematic errors which are a function of phase should even out over the course of the observations. We find that the random error of an individual observation of ±0.8 arcmin can be achieved.

Krisciunas, Kevin

2010-01-01

168

Upper-atmosphere zonal winds determined from orbital analysis of Cosmos 482, 1972-23A  

Microsoft Academic Search

Atmospheric rotation produces a change in orbital inclination which decreases under the effect of zonal winds. Inclination values obtained for Cosmos 482 are analyzed to determine the atmospheric rotation rate of the zonal wind (East-West) at a height near 235 km. Orbital parameters of Cosmos 482 at 55 epochs from August 1975 to October 1977 were determined by the PROP

P. Moore

1981-01-01

169

Flight Mechanics/Estimation Theory Symposium. [with application to autonomous navigation and attitude/orbit determination  

NASA Technical Reports Server (NTRS)

Onboard and real time image processing to enhance geometric correction of the data is discussed with application to autonomous navigation and attitude and orbit determination. Specific topics covered include: (1) LANDSAT landmark data; (2) star sensing and pattern recognition; (3) filtering algorithms for Global Positioning System; and (4) determining orbital elements for geostationary satellites.

Fuchs, A. J. (editor)

1979-01-01

170

Integrated magnetometer-horizon sensor low-earth orbit determination using UKF  

NASA Astrophysics Data System (ADS)

The estimation of the satellite orbital elements using the integrated magnetometer and horizon sensors data has been investigated in this study. These sensors are generally employed for attitude estimation. The magnetometer and the horizon sensor measure the Earth's magnetic field as well as the Earth's center direction in the body frame, respectively. The magnitude of the magnetic field and the angle between two vectors have been used for orbit estimation purpose. This excludes the knowledge of the attitude in the orbit determination. The Gaussian variation of parameters equations is used for the orbital motion dynamical model to have the orbital elements as the states of the system. Since the dynamics of the system and the measurement model are nonlinear, the unscented Kalman filter (UKF) is utilized. Moreover, the magnetometer is subjected to scale factor and bias errors and these parameters are also estimated together with the orbital elements. It has been revealed that the UKF-based orbit determination algorithm can determine the sensor error parameters as well as the Keplerian orbital elements. The sensitivity analysis results show that this approach is insensitive to inclination and eccentricity for most orbits and can be adopted for near equatorial as well as near circular orbits.

Farahanifar, Mohammad; Assadian, Nima

2015-01-01

171

Orbit Determination Error Analysis Results for the Triana Sun-Earth L2 Libration Point Mission  

NASA Technical Reports Server (NTRS)

Using the NASA Goddard Space Flight Center's Orbit Determination Error Analysis System (ODEAS), orbit determination error analysis results are presented for all phases of the Triana Sun-Earth L1 libration point mission and for the science data collection phase of a future Sun-Earth L2 libration point mission. The Triana spacecraft was nominally to be released by the Space Shuttle in a low Earth orbit, and this analysis focuses on that scenario. From the release orbit a transfer trajectory insertion (TTI) maneuver performed using a solid stage would increase the velocity be approximately 3.1 km/sec sending Triana on a direct trajectory to its mission orbit. The Triana mission orbit is a Sun-Earth L1 Lissajous orbit with a Sun-Earth-vehicle (SEV) angle between 4.0 and 15.0 degrees, which would be achieved after a Lissajous orbit insertion (LOI) maneuver at approximately launch plus 6 months. Because Triana was to be launched by the Space Shuttle, TTI could potentially occur over a 16 orbit range from low Earth orbit. This analysis was performed assuming TTI was performed from a low Earth orbit with an inclination of 28.5 degrees and assuming support from a combination of three Deep Space Network (DSN) stations, Goldstone, Canberra, and Madrid and four commercial Universal Space Network (USN) stations, Alaska, Hawaii, Perth, and Santiago. These ground stations would provide coherent two-way range and range rate tracking data usable for orbit determination. Larger range and range rate errors were assumed for the USN stations. Nominally, DSN support would end at TTI+144 hours assuming there were no USN problems. Post-TTI coverage for a range of TTI longitudes for a given nominal trajectory case were analyzed. The orbit determination error analysis after the first correction maneuver would be generally applicable to any libration point mission utilizing a direct trajectory.

Marr, G.

2003-01-01

172

FIRST ORBIT AND MASS DETERMINATIONS FOR NINE VISUAL BINARIES  

SciTech Connect

This paper presents the first published orbits and masses for nine visual double stars: WDS 00149-3209 (B 1024), WDS 01006+4719 (MAD 1), WDS 03130+4417 (STT 51), WDS 04357+3944 (HU 1084), WDS 19083+2706 (HO 98 AB), WDS 19222-0735 (A 102 AB), WDS 20524+2008 (HO 144), WDS 21051+0757 (HDS 3004 AB), and WDS 22202+2931 (BU 1216). Masses were calculated from the updated Hipparcos parallax data when available and sufficiently precise, or from dynamical parallaxes otherwise. Other physical and orbital properties are also discussed.

Ling, J. F., E-mail: josefinaf.ling@usc.es [Departamento de Matematica Aplicada, Universidade de Santiago de Compostela (Spain)

2012-01-15

173

Comparison of TOPEX/Poseidon orbit determination solutions obtained by the Goddard Space Flight Center Flight Dynamics Division and Precision Orbit Determination Teams  

NASA Technical Reports Server (NTRS)

Orbit determination results are obtained by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) using the Goddard Trajectory Determination System (GTDS) and a real-time extended Kalman filter estimation system to process Tracking Data and Relay Satellite (TDRS) System (TDRSS) measurements in support of the Ocean Topography Experiment (TOPEX)/Poseidon spacecraft navigation and health and safety operations. GTDS is the operational orbit determination system used by the FDD, and the extended Kalman fliter was implemented in an analysis prototype system, the Real-Time Orbit Determination System/Enhanced (RTOD/E). The Precision Orbit Determination (POD) team within the GSFC Space Geodesy Branch generates an independent set of high-accuracy trajectories to support the TOPEX/Poseidon scientific data. These latter solutions use the Geodynamics (GEODYN) orbit determination system with laser ranging tracking data. The TOPEX/Poseidon trajectories were estimated for the October 22 - November 1, 1992, timeframe, for which the latest preliminary POD results were available. Independent assessments were made of the consistencies of solutions produced by the batch and sequential methods. The batch cases were assessed using overlap comparisons, while the sequential cases were assessed with covariances and the first measurement residuals. The batch least-squares and forward-filtered RTOD/E orbit solutions were compared with the definitive POD orbit solutions. The solution differences were generally less than 10 meters (m) for the batch least squares and less than 18 m for the sequential estimation solutions. The differences among the POD, GTDS, and RTOD/E solutions can be traced to differences in modeling and tracking data types, which are being analyzed in detail.

Doll, C.; Mistretta, G.; Hart, R.; Oza, D.; Cox, C.; Nemesure, M.; Bolvin, D.; Samii, Mina V.

1993-01-01

174

2A10Laser experiments for determining satellite orbits  

Microsoft Academic Search

The results from a series of experiments at the Smithsonian Astrophysical Observing Station, Organ Pass, N. Mex., indicate how lasers may be used to supplement the worldwide network of Baker-Nunn cameras in obtaining precise satellite orbits for geodesy and other purposes. A pulsed ruby laser and photoelectric receiver were located at the observing station. Laser returns were obtained from the

P. Anderson; C. Lehr; L. Maestre; G. Snyder

1966-01-01

175

20 CFR 410.620 - Notice of initial determination.  

Code of Federal Regulations, 2010 CFR

...FEDERAL COAL MINE HEALTH AND SAFETY ACT OF 1969, TITLE IV-BLACK LUNG BENEFITS (1969- ) Determinations of Disability...party's entitlement to benefits has ended because of such party's death (see § 410.610(c)). If the initial...

2010-04-01

176

20 CFR 410.620 - Notice of initial determination.  

Code of Federal Regulations, 2011 CFR

...FEDERAL COAL MINE HEALTH AND SAFETY ACT OF 1969, TITLE IV-BLACK LUNG BENEFITS (1969- ) Determinations of Disability...party's entitlement to benefits has ended because of such party's death (see § 410.610(c)). If the initial...

2011-04-01

177

OCO-2 (Orbiting Carbon Observatory-2) mission operations planning and initial operations experiences  

NASA Astrophysics Data System (ADS)

OCO-2 (Orbiting Carbon Observatory-2) is the first NASA (National Aeronautics and Space Administration) mission dedicated to studying atmospheric carbon dioxide, specifically to identify sources (emitters) and sinks (absorbers) on a regional (1000 km x 1000 km) scale. The mission is designed to meet a science imperative by providing critical and urgent measurements needed to improve understanding of the carbon cycle and global climate change processes. The single instrument consisting of three grating spectrometers was built at the Jet Propulsion Laboratory, but is based on the design co-developed with Hamilton Sundstrand Corporation for the original OCO mission. The instrument underwent an extensive ground test program. This was generally made possible through the use of a thermal vacuum chamber with a window/port that allowed optical ground support equipment to stimulate the instrument. The instrument was later delivered to Orbital Sciences Corporation for integration and test with the LEOStar-2 spacecraft. During the overall ground test campaign, proper function and performance in simulated launch, ascent, and space environments were verified. The observatory was launched into space on 02 July 2014. Initial indications are that the instrument is meeting functional and performance specifications, and there is every expectation that the spatially-order, geo-located, calibrated spectra of reflected sunlight and the science retrievals will meet the Level 1 science requirements.

Basilio, Ralph R.; Pollock, H. Randy; Hunyadi-Lay, Sarah L.

2014-10-01

178

Orbit Determination and Navigation of the Solar Terrestrial Relations Observatory (STEREO)  

NASA Technical Reports Server (NTRS)

This paper provides an overview of the required upgrades necessary for navigation of NASA's twin heliocentric science missions, Solar TErestrial RElations Observatory (STEREO) Ahead and Behind. The orbit determination of the STEREO spacecraft was provided by the NASA Goddard Space Flight Center's (GSFC) Flight Dynamics Facility (FDF) in support of the mission operations activities performed by the Johns Hopkins University Applied Physics Laboratory (APL). The changes to FDF's orbit determination software included modeling upgrades as well as modifications required to process the Deep Space Network X-band tracking data used for STEREO. Orbit results as well as comparisons to independently computed solutions are also included. The successful orbit determination support aided in maneuvering the STEREO spacecraft, launched on October 26, 2006 (00:52 Z), to target the lunar gravity assists required to place the spacecraft into their final heliocentric drift-away orbits where they are providing stereo imaging of the Sun.

Mesarch, Michael A.; Robertson, Mika; Ottenstein, Neil; Nicholson, Ann; Nicholson, Mark; Ward, Douglas T.; Cosgrove, Jennifer; German, Darla; Hendry, Stephen; Shaw, James

2007-01-01

179

Orbit Determination with the two-body Integrals. III  

E-print Network

We present the results of our investigation on the use of the two-body integrals to compute preliminary orbits by linking too short arcs of observations of celestial bodies. This work introduces a significant improvement with respect to the previous papers on the same subject (see Gronchi et al. 2010, 2011). Here we find a univariate polynomial equation of degree 9 in the radial distance $\\rho$ of the orbit at the mean epoch of one of the two arcs. This is obtained by a combination of the algebraic integrals of the two-body problem. Moreover, the elimination step, which in Gronchi et al. 2010, 2011 was done by resultant theory coupled with the discrete Fourier transform, is here obtained by elementary calculations. We also show some numerical tests to illustrate the performance of the new algorithm.

Giovanni F. Gronchi; Giulio Bau'; Stefano Maro'

2015-01-15

180

Determination of Spin-Orbit Interaction in InAs Heterostructure  

Microsoft Academic Search

Spin-orbit interaction (SOI) gives a useful tool to control spin precession in the semiconductor without external magnetic field. The Rashba effect induced by spin-orbit interaction enables to imagine the spin field effect transistor in which the resistance modulation is achieved by precession of spins moving in a channel. The oscillatory magnetoresistance was measured to determine SOI parameter of inverted type

Tae Young Lee; Hyun Cheol Koo; Kyung Ho Kim; Hyung-Jun Kim; Joonyeon Chang; Suk-Hee Han

2009-01-01

181

Prospects for the Determination of Star Orbits near the Galactic Center  

Microsoft Academic Search

We simulate the observations of proper motion of stars very close to the Galactic center. We show that the speckle interferometry done with the Keck II telescope is accurate enough to obtain orbital parameters for stars with the period P~10 yr during ~10 seasons of astrometric observations made once a year. The determination of a single orbit will give a

M. Jaroszynski

1999-01-01

182

A new method to determine the periodic orbit of a nonlinear dynamic system and its period  

Microsoft Academic Search

Periodic motion is an important steady-state motion in the real world. In this paper, a new generalized shooting method for determining the periodic orbit of a nonlinear dynamic system and its period is presented by rebuilding the traditional shooting method. First, by changing the time scale, the period of the periodic orbit of a nonlinear system is drawn into the

Dexin Li; Jianxue Xu

2005-01-01

183

Aleksandar KOSTADINOV: Expected performance of Orbit Determination of the GALILEO Satellites  

E-print Network

Aleksandar KOSTADINOV: Expected performance of Orbit Determination of the GALILEO Satellites satellite navigation system. The system will consist of about 30 satellites in medium earth orbits (MEOs) at 23600 km altitude. The launch of the first GALILEO satellites can be expected

Schuh, Harald

184

Thermal re-radiation modelling for the precise prediction and determination of spacecraft orbits  

NASA Astrophysics Data System (ADS)

Thermal re-radiation (TRR) affects spacecraft orbits when a net recoil force results from the uneven emission of radiation from the spacecraft surface these forces can perturb spacecraft trajectories by several metres over a few hours. The mis-modelling of TRR limits the accuracy with which some spacecraft orbits can be computed, and in turn limits capabilities of applications where satellite positioning is key. These range from real-time navigation to geodetic measurements using low earth orbiting spacecraft. Approaches for the precise analytical modelling of TRR forces are presented. These include methods for the treatment of spacecraft multilayer insulation (MLI), solar panels and other spacecraft components. Techniques for determining eclipse boundary crossing times for an oblate earth and modelling penumbral fluxes are also described. These affect both the thermal force and the considerably larger solar radiation pressure (SRP) force. These methods are implemented for the Global Positioning System (GPS) Block IIR spacecraft and the altimetry satellite Jason-1. For GPS Block IIR, model accuracy is assessed by orbit prediction through numerical integration of the spacecraft force model. Orbits were predicted over 12 hours and compared to precise orbits before and after thermal and eclipse-related models were included. When the solar panel model was included, mean orbit prediction errors dropped from 3.3m to 3.0m over one orbit inclusion of the MLI model reduced errors further to 0.6m. For eclipsing satellites, the penumbral flux model reduced errors from 0.7 m to 0.56m. The Jason-1 models were tested by incorporation into GIPSY-OASIS II, the Jet Propulsion Laboratory's (JPL) orbit determination software. A combined SRP and TRR model yielded significant improvements in orbit determination over all other existing models and is now used routinely by JPL in the operational orbit determination of Jason-1.

Adhya, Sima

185

NEW TECHNIQUES FOR ORBIT DETERMINATION OF GEOSYNCHRONOUS, GEOSYNCHRONOUS-TRANSFER, AND OTHER HIGH-ALTITUDE EARTH ORBITERS  

Microsoft Academic Search

This paper explores two innovative approaches to high-altitude orbit determination. GPS-enhanced tracking (GET), which has been field-tested by JPL with two geosynchronous satellites, utilizes inexpensive ground terminals developed from commercial GPS receivers. The second approach involves tracking GPS directly onboard, soon to be tested by JPL with a new microGPS receiver, also known as the Bit Grabber GPS Space Receiver

S. M. Lichtent; S. C. Wut; L. E. Youngt; B. J. Hairiest; Peter Coulson

186

Prospective new transportation application initiatives in NASA's earth-to-orbit propulsion technology program  

NASA Technical Reports Server (NTRS)

NASA's Earth-to-Orbit (ETO) Propulsion Technology Program, a multi-year/multi-task focused technology effort is, today, highly focused on conventional high-thrust cryogenic liquid chemical rocket engines and their envisioned future technology needs. But as highlighted in the U.S. National Ten-Year Space Launch Technology Plan, a set of less-conventional propulsion subjects, ones which offer significant promise for both, improving the state of the art and opening up new propulsion-capability possibilities, is now directed to the space propulsion planning community's attention. In conducting its forward-planning activities, it is highly appropriate that the ETO Program (and other programs as well) carefully consider integrating these "new initiative" subjects into the taskwork of future years. After an introductory consideration of the National Plan's propulsion-related directives, followed by a brief background overview of the ETO Program, the following specific new-initiative candidates are discussed from the standpoint of technology-program planning: operationally efficient propulsion systems; high-thrust hybrid rocket propulsion; low-cost, low-pressure expendable propulsion subsystems; advanced cryogenic in-space propulsion systems; integrated modular engine (IME) configured propulsion systems, and combined-cycle airbreathing/rocket propulsion systems.

Escher, William J. D.

1992-01-01

187

Lunar Prospector Orbit Determination Uncertainties Using the High Resolution Lunar Gravity Models  

NASA Technical Reports Server (NTRS)

The Lunar Prospector (LP) mission began on January 6, 1998, when the LP spacecraft was launched from Cape Canaveral, Florida. The objectives of the mission were to determine whether water ice exists at the lunar poles, generate a global compositional map of the lunar surface, detect lunar outgassing, and improve knowledge of the lunar magnetic and gravity fields. Orbit determination of LP performed at the Jet Propulsion Laboratory (JPL) is conducted as part of the principal science investigation of the lunar gravity field. This paper will describe the JPL effort in support of the LP Gravity Investigation. This support includes high precision orbit determination, gravity model validation, and data editing. A description of the mission and its trajectory will be provided first, followed by a discussion of the orbit determination estimation procedure and models. Accuracies will be examined in terms of orbit-to-orbit solution differences, as a function of oblateness model truncation, and inclination in the plane-of-sky. Long term predictions for several gravity fields will be compared to the reconstructed orbits to demonstrate the accuracy of the orbit determination and oblateness fields developed by the Principal Gravity Investigator.

Carranza, Eric; Konopliv, Alex; Ryne, Mark

1999-01-01

188

Orbit Determination with Topocentric Correction: Algorithms for the Next Generation Surveys  

E-print Network

Given a set of astrometric observations of the same object, the problem of orbit determination is to compute the orbit and to assess its uncertainty and reliability. For the next generation surveys, with much larger number density of observed objects, new algorithms or substantial revisions of the classical ones are needed. The problem has three main steps, preliminary orbit, least squares orbit, and quality control. The classical theory of preliminary orbits was incomplete: the consequences of the topocentric correction had not been fully studied. We show that it is possible to account for this correction, possibly with an increase in the number of preliminary solutions, without impairing the overall orbit determination performance. We have developed modified least squares orbit determination algorithms that can be used to improve the reliability of the procedure. We have tested the complete procedure on two simulations with number densities comparable to that expected from the next generation surveys such as Pan-STARRS and LSST. To control the problem of false identifications we have introduced a quality control on the fit residuals based on an array of metrics and a procedure to remove duplications and contradictions in the output. The results confirm that large sets of discoveries can be obtained with good quality orbits and very high success rate losing only 0.6 to 1.3% of objects and a false identification rate in the range 0.02 to 0.06%.

Andrea Milani; Giovanni F. Gronchi; Davide Farnocchia; Zoran Knezevic; Robert Jedicke; Larry Denneau; Francesco Pierfederici

2007-07-28

189

On precise orbit determination of HY-2 with space geodetic techniques  

NASA Astrophysics Data System (ADS)

As the first radar altimetric satellite of China, HY-2 requires the precise orbit determination with a higher accuracy than that of other satellites. In order to achieve the designed radial orbit with the accuracy better than 10 cm for HY-2, the methods of precise orbit determination for HY-2 with the centimeter-level accuracy based on space geodetic techniques (DORIS, SLR, and satellite-borne GPS) are studied in this paper. Perturbations on HY-2 orbit are analyzed, in particular those due to the non-spherical gravitation of the earth, ocean tide, solid earth tide, solar and earth radiation, and atmospheric drag. Space geodetic data of HY-2 are simulated with the designed HY-2 orbit parameters based on the orbit dynamics theory to optimize the approaches and strategies of precise orbit determination of HY-2 with the dynamic and reduced-dynamic methods, respectively. Different methods based on different techniques are analyzed and compared. The experiment results show that the nonspherical perturbation modeled by GGM02C causes a maximum perturbation, and errors caused by the imperfect modeling of atmospheric drag have an increasing trend on T direction, but errors are relatively stable on the other two directions; besides, the methods with three space geodetic techniques achieve the radial orbit with the precision better than 10 cm.

Guo, Jinyun; Kong, Qiaoli; Qin, Jian; Sun, Yu

2013-06-01

190

Experimental determination of spin orbital coupling states of O2(-)  

Microsoft Academic Search

Electron affinities, Ea, E1 and A1 are reported for the 12 primary X, A-K (27 spin) states of O2(-): KeqT3\\/2 = (SanQan)(2pimek\\/h2)3\\/2exp(Ea\\/RT) k1 = A1T-1\\/2exp(-E1\\/RT). These are obtained from pulsed discharge electron capture detector data by rigorously including literature values and uncertainties in a global non-linear least-squares adjustment. Simple molecular orbital theory predicts 27 bonding and 27 anti-bonding low-lying spin

Edward C. M. Chen; Charles Herder; Winston Chang; Regina Ting; Edward S. Chen

2006-01-01

191

Periodic-orbit determination of dynamical correlations in stochastic processes  

E-print Network

It is shown that large deviation statistical quantities of the discrete time, finite state Markov process $P_{n+1}^{(j)}=\\sum_{k=1}^NH_{jk}P_n^{(k)}$, where P_n^{(j)} is the probability for the j-state at the time step n and H_{jk} is the transition probability, completely coincides with those from the Kalman map corresponding to the above Markov process. Furthermore, it is demonstrated that by using simple examples, time correlation functions in finite state Markov processes can be well described in terms of unstable periodic orbits embedded in the equivalent Kalman maps.

Miki U. Kobayashi; Hirokazu Fujisaka; Syuji Miyazaki

2007-08-10

192

Orbit determination for a Jupiter orbiter tour of the Galilean satellites  

NASA Technical Reports Server (NTRS)

Current NASA planning envisions an ambitious Jupiter tour mission which will arrive at the planet in the year, 1984. The objectives of this mission are to broaden our knowledge of the outer solar system and in particular to extend our understanding of the physical processes at work in the Jupiter and Galilean satellite environment. To achieve these goals, precise spacecraft navigation is a fundamental requirement inasmuch as very near encounters with the satellites are necessary both for the planned scientific investigations and to reduce fuel requirements necessary for orbital insertion about the planet. This paper, deals with problems of producing precise spacecraft state estimates relative to the Galilean satellites, with the aid of both earth-based radio and on-board video data.

Russell, R. K.; Ellis, J.

1974-01-01

193

TOPEX orbit determination and gravity recovery using Global Positioning System data from repeat orbits  

NASA Technical Reports Server (NTRS)

A covariance analysis is presented for satellite tracking and gravity recovery with a differential Global Positioning System-based technique to be demonstrated on TOPEX in the early 1990s. The technique employs data from an ensemble of repeat ground tracks to recover a unique satellite epoch state for each track and a set of invariant positional parameters common to all tracks. The positional parameters represent the effect of mismodeled gravitational field on the satellite orbit. At an altitude of 1336 km, where gravity modeling is the dominant systematic error, averaging of random error over many arcs and adjustment of the gravity model reduce the final satellite position error. The positional parameters can then be used to produce a refined global gravity model. The analysis indicates that errors ranging from 5 to 8 cm in TOPEX altitude and 0.05 to 0.2 mGal for the gravity field can be achieved, depending on the number of repeat arcs used.

Wu, Jiun-Tsong; Yunck, Thomas P.

1992-01-01

194

Prospects for the Determination of Star Orbits Near the Galactic Center  

E-print Network

We simulate the observations of proper motion of stars very close to the Galactic Center. We show that the speckle interferometry done with the Keck II telescope is accurate enough to obtain orbital parameters for stars with the period P about 10 y during 10 seasons of astrometric observations made once a year. The determination of a single orbit will give central mass estimate with the typical uncertainty of the existing mass determinations based on velocity dispersion measurements. A much higher precision orbits will be measured in several years when Keck Interferometer becomes operational, and fainter stars are discovered even closer to Sgr A*. Astrometry alone will provide accurate determination of the ratio: M/D^3, where M is the black hole mass and D is the distance to the Galactic Center. If spectroscopic orbits of the stars are also measured then both: M and D will be precisely determined.

M. Jaroszynski

1999-03-23

195

Evaluation of the accuracy of volume determination on the orbit and eyeball using MRI  

Microsoft Academic Search

PurposeThis study reports a calibration carried out on phantoms simulating the orbit and eyeball to evaluate the accuracy of volumetric determination using MRI DICOM (Digital Imaging and Communication in Medicine) images.

Anson Chau; Karl Fung; Maurice Yap

2005-01-01

196

Orbit on demand - Will cost determine best design?  

NASA Technical Reports Server (NTRS)

Eleven design concepts for vertical (V) and horizontal (H) take-off launch-on-demand manned orbital vehicles are discussed. Attention is given to up to three stages, Mach numbers (sub-, 2, or 3), expendable boosters, drop tanks (DT), and storable (S) or cryogenic fuels. All the concepts feature lifting bodies with circular cross-section and most have a 7 ft diam, 15 ft long payload bay as well as a crew compartment. Expendable elements impose higher costs and in some cases reduce all-azimuth launch capabilities. Single-stage vehicles simplify the logistics whether in H or V configuration. A two-stage H vehicle offers launch offset for the desired orbital plane before firing the rocket engines after take-off and subsonic acceleration. A two-stage fully reusable V form has the second lowest weight of the vehicles studied and an all-azimuth launch capability. Better definition of the prospective mission requirements is needed before choosing among the alternatives.

Macconochie, J. O.; Mackley, E. A.; Morris, S. J.; Phillips, W. P.; Breiner, C. A.; Scotti, S. J.

1985-01-01

197

Orbit Determination with the two-body Integrals  

E-print Network

We investigate a method to compute a finite set of preliminary orbits for solar system bodies using the first integrals of the Kepler problem. This method is thought for the applications to the modern sets of astrometric observations, where often the information contained in the observations allows only to compute, by interpolation, two angular positions of the observed body and their time derivatives at a given epoch; we call this set of data attributable. Given two attributables of the same body at two different epochs we can use the energy and angular momentum integrals of the two-body problem to write a system of polynomial equations for the topocentric distance and the radial velocity at the two epochs. We define two different algorithms for the computation of the solutions, based on different ways to perform elimination of variables and obtain a univariate polynomial. Moreover we use the redundancy of the data to test the hypothesis that two attributables belong to the same body (linkage problem). It is also possible to compute a covariance matrix, describing the uncertainty of the preliminary orbits which results from the observation error statistics. The performance of this method has been investigated by using a large set of simulated observations of the Pan-STARRS project.

Giovanni Federico Gronchi; Linda Dimare; Andrea Milani

2010-03-31

198

A Restricted Poincare Map for Determining Exponentially Stable Periodic Orbits in Systems with Impulse Effects: Application to Bipedal Robots  

E-print Network

A Restricted Poincar´e Map for Determining Exponentially Stable Periodic Orbits in Systems orbit can be determined on the basis of the restricted Poincar´e map, that is, the Poincar´e return map to determine the existence and stability of periodic orbits in a broad range of system models, such as time

Grizzle, Jessy W.

199

NCAR's contribution to Improved tropospheric delay measurement and precision orbit determination for satellite ocean altimetry. 1 NCAR's contribution to  

E-print Network

NCAR's contribution to Improved tropospheric delay measurement and precision orbit determination orbit determination for satellite ocean altimetry. a JPL/NCAR project, Yoaz Bar-Sever, Principal and precision orbit determination for satellite ocean altimetry. 2 1.0 Introduction Satellite Oceanic altimetry

200

Determination of orbital parameters of interacting galaxies using a genetic algorithm. Description of the method and application to artificial data  

Microsoft Academic Search

A method for determining the orbital parameters of interacting pairs of galaxies is presented and evaluated using artificial data. The method consists of a genetic algorithm which can search efficiently through the very large space of possible orbits. It is found that orbital parameters close to the actual orbital parameters of the pair can in general be found, even in

M. Wahde

1998-01-01

201

Initial refinement of minor planet orbits for pointing and observation with the Hubble Space Telescope  

NASA Technical Reports Server (NTRS)

Refinements of the orbital elements for 24 minor planets that will be observed with the Fine Guidance Sensors (FGSs) on the Hubble Space Telescope (HST) are presented. The accuracy of these orbits is discussed in the context of the ephemeris requirements for target acquisition with the FGSs. Comparisons with standard catalog orbits are made to evaluate the suitability of the use of the catalog orbits for HST pointing. It is found that the orbits published in the most recent Minor Planet Circulars are capable of positional predictions that are accurate at the 1-arcsec level. However, there are still many orbits that have not been revised in the last 10 yr and these should not be used for critical pointing ephemerides. In many cases, the orbital elements will have to be refined using recent ground-based observations before a minor planet can be reliably observed by HST.

Whipple, Arthur L.; Hemenway, Paul D.; Ingram, Doug

1991-01-01

202

Study of geopotential error models used in orbit determination error analysis  

NASA Technical Reports Server (NTRS)

The uncertainty in the geopotential model is currently one of the major error sources in the orbit determination of low-altitude Earth-orbiting spacecraft. The results of an investigation of different geopotential error models and modeling approaches currently used for operational orbit error analysis support at the Goddard Space Flight Center (GSFC) are presented, with emphasis placed on sequential orbit error analysis using a Kalman filtering algorithm. Several geopotential models, known as the Goddard Earth Models (GEMs), were developed and used at GSFC for orbit determination. The errors in the geopotential models arise from the truncation errors that result from the omission of higher order terms (omission errors) and the errors in the spherical harmonic coefficients themselves (commission errors). At GSFC, two error modeling approaches were operationally used to analyze the effects of geopotential uncertainties on the accuracy of spacecraft orbit determination - the lumped error modeling and uncorrelated error modeling. The lumped error modeling approach computes the orbit determination errors on the basis of either the calibrated standard deviations of a geopotential model's coefficients or the weighted difference between two independently derived geopotential models. The uncorrelated error modeling approach treats the errors in the individual spherical harmonic components as uncorrelated error sources and computes the aggregate effect using a combination of individual coefficient effects. This study assesses the reasonableness of the two error modeling approaches in terms of global error distribution characteristics and orbit error analysis results. Specifically, this study presents the global distribution of geopotential acceleration errors for several gravity error models and assesses the orbit determination errors resulting from these error models for three types of spacecraft - the Gamma Ray Observatory, the Ocean Topography Experiment, and the Cosmic Background Explorer.

Yee, C.; Kelbel, D.; Lee, T.; Samii, M. V.; Mistretta, G. D.; Hart, R. C.

1991-01-01

203

Orbiting Deep Space Relay Station (ODSRS). Volume 1: Requirement determination  

NASA Technical Reports Server (NTRS)

The deep space communications requirements of the post-1985 time frame are described and the orbiting deep space relay station (ODSRS) is presented as an option for meeting these requirements. Under current conditions, the ODSRS is not yet cost competitive with Earth based stations to increase DSN telemetry performance, but has significant advantages over a ground station, and these are sufficient to maintain it as a future option. These advantages include: the ability to track a spacecraft 24 hours per day with ground stations located only in the USA; the ability to operate at higher frequencies that would be attenuated by Earth's atmosphere; and the potential for building very large structures without the constraints of Earth's gravity.

Hunter, J. A.

1979-01-01

204

78 FR 48191 - Certain Linear Actuators; Commission Determination Not To Review an Initial Determination...  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Investigation No. 337-TA-880 Certain Linear Actuators; Commission Determination Not To Review an Initial Determination...within the United States after importation of certain linear actuators by reason of infringement of U.S. Patent No...

2013-08-07

205

Improved solution accuracy for Landsat-4 (TDRSS-user) orbit determination  

NASA Technical Reports Server (NTRS)

This paper presents the results of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite System (TDRSS) user spacecraft, Landsat-4, obtained using a Prototype Filter Smoother (PFS), with the accuracy of an established batch-least-squares system, the Goddard Trajectory Determination System (GTDS). The results of Landsat-4 orbit determination will provide useful experience for the Earth Observing System (EOS) series of satellites. The Landsat-4 ephemerides were estimated for the January 17-23, 1991, timeframe, during which intensive TDRSS tracking data for Landsat-4 were available. Independent assessments were made of the consistencies (overlap comparisons for the batch case and convariances for the sequential case) of solutions produced by the batch and sequential methods. The filtered and smoothed PFS orbit solutions were compared with the definitive GTDS orbit solutions for Landsat-4; the solution differences were generally less than 15 meters.

Oza, D. H.; Niklewski, D. J.; Doll, C. E.; Mistretta, G. D.; Hart, R. C.

1994-01-01

206

TDRSS-user orbit determination using batch least-squares and sequential methods  

NASA Technical Reports Server (NTRS)

The Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) commissioned Applied Technology Associates, Incorporated, to develop the Real-Time Orbit Determination/Enhanced (RTOD/E) system on a Disk Operating System (DOS)-based personal computer (PC) as a prototype system for sequential orbit determination of spacecraft. This paper presents the results of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite System (TDRSS) user spacecraft, Landsat-4, obtained using RTOD/E, operating on a PC, with the accuracy of an established batch least-squares system, the Goddard Trajectory Determination System (GTDS), and operating on a mainframe computer. The results of Landsat-4 orbit determination will provide useful experience for the Earth Observing System (EOS) series of satellites. The Landsat-4 ephemerides were estimated for the January 17-23, 1991, timeframe, during which intensive TDRSS tracking data for Landsat-4 were available. Independent assessments were made of the consistencies (overlap comparisons for the batch case and covariances and the first measurement residuals for the sequential case) of solutions produced by the batch and sequential methods. The forward-filtered RTOD/E orbit solutions were compared with the definitive GTDS orbit solutions for Landsat-4; the solution differences were less than 40 meters after the filter had reached steady state.

Oza, D. H.; Jones, T. L.; Hakimi, M.; Samii, Mina V.; Doll, C. E.; Mistretta, G. D.; Hart, R. C.

1993-01-01

207

ORBIT DETERMINATION OF DOUBLE-LINED SPECTROSCOPIC BINARIES BY FITTING THE REVISED HIPPARCOS INTERMEDIATE ASTROMETRIC DATA  

SciTech Connect

Untill now, the Hipparcos intermediate astrometric data (HIAD) have contributed little to the full orbit determination of double-lined spectroscopic binaries (SB2s). This is because the photocenter of such a binary system is usually not far from the system mass center, and its orbital wobble is generally weak with respect to the accuracy of the HIAD. However, the HIAD have been recently revised and the accuracy is increased by a factor of 2.2 in the total weight. Therefore, it is interesting to see if the revised HIAD can be used in the orbit determination at least for some SB2s. In this paper, we first search the 9th Catalogue of Orbits of Spectroscopic Binaries (S{sub B{sup 9}}) for SB2s with reliable spectroscopic orbital solutions and with periods between 50 days and 3.2 years. This leaves us with 56 systems. The full orbital solutions of these systems are then determined from the HIAD by a highly efficient grid search method developed in this paper. The high efficiency is achieved by reducing the number of nonlinear model parameters to one, and by allowing all parameters to be adjustable within a region centered at each grid point. After a variety of tests, we finally accept orbital solutions of 13 systems. Among these systems, six (HIP 677, 20894, 87895, 95995, 101382, and 111170) are well resolved with reliable interferometric data. Orbital solutions from these data are consistent with our results. The full orbital solutions of the other seven systems (HIP 9121, 17732, 32040, 57029, 76006, 102431, and 116360) are determined for the first time.

Ren Shulin; Fu Yanning, E-mail: rensl@pmo.ac.c, E-mail: fyn@pmo.ac.c [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2010-05-15

208

Implementing Self-Determination Initiatives: Some Notes on Complex Change.  

ERIC Educational Resources Information Center

This paper presents thoughts resulting from review of proposals by state developmental disabilities authorities, submitted to the Robert Wood Johnson Foundation, that were designs for change initiatives in self-determination systems. These reflections on the use of service money and the provision of supports to people with developmental…

O'Brien, John

209

Orbit determination error analysis and a station-keeping strategy for sun-earth L1 libration point orbits  

NASA Astrophysics Data System (ADS)

Spacecraft in orbits near the interior libration point in the Sun-Earth system are excellent platforms for scientific investigations concerning solar effects on the terrestrial environment. Since such libration point trajectories are generally unstable, spacecraft moving on these paths must use some form of trajectory control to remain close to their nominal orbit. An integral part of any station-keeping investigation is estimation of the spacecraft state vector. The trajectory estimation process will be affected by many sources of error. Several orbit determination error analysis methods are mentioned and some results are summarized. The primary goal of this effort, however, is the development of a station-keeping strategy applicable to such trajectories. This approach uses maneuvers executed (impulsively) at discrete time intervals. The analysis includes some investigation of a number of the problem parameters that affect the overall maneuver costs. Simulations are designed to provide representative station-keeping costs for a spacecraft moving in a libration point trajectory; preliminary results are summarized.

Howell, K. C.; Gordon, S. C.

1994-04-01

210

Radial orbit error reduction and sea surface topography determination using satellite altimetry  

NASA Technical Reports Server (NTRS)

A method is presented in satellite altimetry that attempts to simultaneously determine the geoid and sea surface topography with minimum wavelengths of about 500 km and to reduce the radial orbit error caused by geopotential errors. The modeling of the radial orbit error is made using the linearized Lagrangian perturbation theory. Secular and second order effects are also included. After a rather extensive validation of the linearized equations, alternative expressions of the radial orbit error are derived. Numerical estimates for the radial orbit error and geoid undulation error are computed using the differences of two geopotential models as potential coefficient errors, for a SEASAT orbit. To provide statistical estimates of the radial distances and the geoid, a covariance propagation is made based on the full geopotential covariance. Accuracy estimates for the SEASAT orbits are given which agree quite well with already published results. Observation equations are develped using sea surface heights and crossover discrepancies as observables. A minimum variance solution with prior information provides estimates of parameters representing the sea surface topography and corrections to the gravity field that is used for the orbit generation. The simulation results show that the method can be used to effectively reduce the radial orbit error and recover the sea surface topography.

Engelis, Theodossios

1987-01-01

211

A demonstration of high precision GPS orbit determination for geodetic applications  

NASA Technical Reports Server (NTRS)

High precision orbit determination of Global Positioning System (GPS) satellites is a key requirement for GPS-based precise geodetic measurements and precise low-earth orbiter tracking, currently under study at JPL. Different strategies for orbit determination have been explored at JPL with data from a 1985 GPS field experiment. The most successful strategy uses multi-day arcs for orbit determination and includes fine tuning of spacecraft solar pressure coefficients and station zenith tropospheric delays using the GPS data. Average rms orbit repeatability values for 5 of the GPS satellites are 1.0, 1.2, and 1.7 m in altitude, cross-track, and down-track componenets when two independent 5-day fits are compared. Orbit predictions up to 24 hours outside the multi-day arcs agree within 4 m of independent solutions obtained with well tracked satellites in the prediction interval. Baseline repeatability improves with multi-day as compared to single-day arc orbit solutions. When tropospheric delay fluctuations are modeled with process noise, significant additional improvement in baseline repeatability is achieved. For a 246-km baseline, with 6-day arc solutions for GPS orbits, baseline repeatability is 2 parts in 100 million (0.4-0.6 cm) for east, north, and length components and 8 parts in 100 million for the vertical component. For 1314 and 1509 km baselines with the same orbits, baseline repeatability is 2 parts in 100 million for the north components (2-3 cm) and 4 parts in 100 million or better for east, length, and vertical components.

Lichten, S. M.; Border, J. S.

1987-01-01

212

Investigations to Determine the Origin of the Solar Wind with SPICE and SolarOrbiter  

NASA Astrophysics Data System (ADS)

At large spatial scales, the structure of the solar wind and it's mapping back to the solar corona, is thought to be reasonably well understood. However, the detailed structure of the various source regions at chromospheric and transition region heights is extremely complex, and less well understood. Determining this connection between heliospheric structures and their source regions at the Sun is one of the overarching objective of the Solar Orbiter mission. During perihelion segments of its orbit, when the spacecraft is in quasi-corotation with the Sun, Solar Orbiter will determine the plasma parameters and compositional signatures of the solar wind, which can be compared directly with the spectroscopic signatures of coronal ions with differing charge-to-mass ratios and FIP. One of the key instruments on the Solar Orbiter mission to make these remote sensing measurements is the SPICE (Spectral Imaging of the Coronal Environment) imaging spectrograph. SPICE will provide the images and plasma diagnostics needed to characterize the plasma state in different source regions, from active regions to quiet Sun to coronal holes. By comparing composition, plasma parameters, and low/high FIP ratios of structures remotely, with those measured directly at the Solar Orbiter spacecraft, Solar Orbiter will provide the first direct link between solar wind structures and their source regions at the Sun. This talk will provide a background of previous compositional correlation measurements and an outline of the method to be used for comparing the spectroscopic and in-situ plasma parameters to be measured with Solar Orbiter.

Hassler, Donald M.; DeForest, C.; Wilkinson, E.; Davila, J.; SPICE Team

2011-05-01

213

Orbit determination error analysis and comparison of station-keeping costs for Lissajous and halo-type libration point orbits and sensitivity analysis using experimental design techniques  

NASA Technical Reports Server (NTRS)

Spacecraft in orbit near libration point L1 in the Sun-Earth system are excellent platforms for research concerning solar effects on the terrestrial environment. One spacecraft mission launched in 1978 used an L1 orbit for nearly 4 years, and future L1 orbital missions are also being planned. Orbit determination and station-keeping are, however, required for these orbits. In particular, orbit determination error analysis may be used to compute the state uncertainty after a predetermined tracking period; the predicted state uncertainty levels then will impact the control costs computed in station-keeping simulations. Error sources, such as solar radiation pressure and planetary mass uncertainties, are also incorporated. For future missions, there may be some flexibility in the type and size of the spacecraft's nominal trajectory, but different orbits may produce varying error analysis and station-keeping results. The nominal path, for instance, can be (nearly) periodic or distinctly quasi-periodic. A periodic 'halo' orbit may be constructed to be significantly larger than a quasi-periodic 'Lissajous' path; both may meet mission requirements, but perhaps the required control costs for these orbits are probably different. Also for this spacecraft tracking and control simulation problem, experimental design methods can be used to determine the most significant uncertainties. That is, these methods can determine the error sources in the tracking and control problem that most impact the control cost (output); it also produces an equation that gives the approximate functional relationship between the error inputs and the output.

Gordon, Steven C.

1993-01-01

214

FEDS - An experiment with a microprocessor-based orbit determination system using TDRS data  

NASA Technical Reports Server (NTRS)

An experiment in microprocessor-based onboard orbit determination has been conducted at NASA's Goddard Space Flight Center. The experiment collected forward-link observation data in real time from a prototype transponder and performed orbit estimation on a typical low-earth scientific satellite. This paper discusses the hardware and organizational configurations of the experiment, the structure of the onboard software, the mathematical models, and the experiment results.

Shank, D.; Pajerski, R.

1986-01-01

215

Initial Results of 3D Topographic Mapping Using Lunar Reconnaissance Orbiter Camera (LROC) Stereo Imagery  

Microsoft Academic Search

The Lunar Reconnaissance Orbiter (LRO), launched June 18, 2009, carries the Lunar Reconnaissance Orbiter Camera (LROC) as one of seven remote sensing instruments on board. The camera system is equipped with a Wide Angle Camera (WAC) and two Narrow Angle Cameras (NAC) for systematic lunar surface mapping and detailed site characterization for potential landing site selection and resource identification. The

R. Li; J. Oberst; A. S. McEwen; B. A. Archinal; R. A. Beyer; P. C. Thomas; Y. Chen; J. Hwangbo; J. D. Lawver; F. Scholten; S. S. Mattson; A. E. Howington-Kraus; M. S. Robinson

2009-01-01

216

Improving Fermi Orbit Determination and Prediction in an Uncertain Atmospheric Drag Environment  

NASA Technical Reports Server (NTRS)

Orbit determination and prediction of the Fermi Gamma-ray Space Telescope trajectory is strongly impacted by the unpredictability and variability of atmospheric density and the spacecraft's ballistic coefficient. Operationally, Global Positioning System point solutions are processed with an extended Kalman filter for orbit determination, and predictions are generated for conjunction assessment with secondary objects. When these predictions are compared to Joint Space Operations Center radar-based solutions, the close approach distance between the two predictions can greatly differ ahead of the conjunction. This work explores strategies for improving prediction accuracy and helps to explain the prediction disparities. Namely, a tuning analysis is performed to determine atmospheric drag modeling and filter parameters that can improve orbit determination as well as prediction accuracy. A 45% improvement in three-day prediction accuracy is realized by tuning the ballistic coefficient and atmospheric density stochastic models, measurement frequency, and other modeling and filter parameters.

Vavrina, Matthew A.; Newman, Clark P.; Slojkowski, Steven E.; Carpenter, J. Russell

2014-01-01

217

Early results from the TOPEX/POSEIDON GPS precise orbit determination demonstration  

NASA Technical Reports Server (NTRS)

TOPEX/POSEIDON, a US/French oceanographic mission launched in August 1992, is the first earth satellite to carry a multi-channel, dual frequency Global Positioning System (GPS) receiver capable of making high precision P-code pseudorange and carrier phase measurements. The receiver was placed on TOPEX/POSEIDON as an experiment to demonstrate the potential of differential GPS tracking for subdecimeter orbit determination. In addition to the receiver, TOPEX/POSEIDON carries two flight-proven tracking systems to provide the operational precise orbit determination needed to meet the mission scientific requirements. These include a French-built one-way Doppler system known as DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) and a circular ring of laser retroreflectors. Here we evaluate the quality of the GPS-determined orbits by examining post-fit residuals, orbit comparisons with DORIS, and orbit repeatability on overlapping data arcs. Overlapping data arcs with 6 hrs of common data out of a 30-hr arc have an average root-mean-square (RMS) altitude difference of 3.0 cm for 9 arcs. The average RMS altitude difference about the mean with a DORIS orbit was 5.7 cm.

Bertiger, Willy; Wu, Sien; Yunck, Tom; Muellerschoen, Ron; Willis, Pascal; Bar-Sever, Yoaz; Davis, AB; Haines, Bruce; Munson, Tim; Lichten, Steve

1993-01-01

218

TOPEX/Poseidon Precision Orbit Determination Using Combined GPS, SLR, and DORIS  

NASA Technical Reports Server (NTRS)

TOPEX/Poseidon (T/P) is a joint spaceborne oceanographic mission of U.W. NASA and France CNES design launched August 10, 1992. The satellite has a variety tracking systems for both operational and precision orbit determination. Three precise tracking systems: Satellite Laser Ranging (SLR), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and Global Positioning System (GPS) provide high quality measurements essential for reconstructing the T/P orbital height with centimeter precision. This paper presents results of simultaneously processing all three data types to exploit the inherent strength of each in a combined solution. SLR and DORIS are routinely combined to provide orbit solutions for the T/P science team. GPS orbit solutions are produced as part of the first demonstration flight of a high quality spaceborne GPS receiver. Coordinate frame and software system differences between the combined SLR/DORIS orbits and the GPS orbits induce orbital height differences of 2 to 3 centimeters. Combining the three data types within a single software system permits removal of software system differences while obtaining coordinate frame calibration information. These calibrations will aid future spaceborne GPS missions that are not complemented with SLR and/or DORIS.

Guinn, Joseph R.

1995-01-01

219

Statistical Orbit Determination using the Particle Filter for Incorporating Non-Gaussian Uncertainties  

NASA Technical Reports Server (NTRS)

The tracking of space objects requires frequent and accurate monitoring for collision avoidance. As even collision events with very low probability are important, accurate prediction of collisions require the representation of the full probability density function (PDF) of the random orbit state. Through representing the full PDF of the orbit state for orbit maintenance and collision avoidance, we can take advantage of the statistical information present in the heavy tailed distributions, more accurately representing the orbit states with low probability. The classical methods of orbit determination (i.e. Kalman Filter and its derivatives) provide state estimates based on only the second moments of the state and measurement errors that are captured by assuming a Gaussian distribution. Although the measurement errors can be accurately assumed to have a Gaussian distribution, errors with a non-Gaussian distribution could arise during propagation between observations. Moreover, unmodeled dynamics in the orbit model could introduce non-Gaussian errors into the process noise. A Particle Filter (PF) is proposed as a nonlinear filtering technique that is capable of propagating and estimating a more complete representation of the state distribution as an accurate approximation of a full PDF. The PF uses Monte Carlo runs to generate particles that approximate the full PDF representation. The PF is applied in the estimation and propagation of a highly eccentric orbit and the results are compared to the Extended Kalman Filter and Splitting Gaussian Mixture algorithms to demonstrate its proficiency.

Mashiku, Alinda; Garrison, James L.; Carpenter, J. Russell

2012-01-01

220

Self-consistent treatment of tidal variations in the geocenter for precise orbit determination  

NASA Astrophysics Data System (ADS)

We show that the current levels of accuracy being achieved for the precise orbit determination (POD) of low-Earth orbiters demonstrate the need for the self-consistent treatment of tidal variations in the geocenter. Our study uses as an example the POD of the OSTM/Jason-2 satellite altimeter mission based upon Global Positioning System (GPS) tracking data. Current GPS-based POD solutions are demonstrating root-mean-square (RMS) radial orbit accuracy and precision of cm and 1 mm, respectively. Meanwhile, we show that the RMS of three-dimensional tidal geocenter variations is mm, but can be as large as 15 mm, with the largest component along the Earth's spin axis. Our results demonstrate that GPS-based POD of Earth orbiters is best performed using GPS satellite orbit positions that are defined in a reference frame whose origin is at the center of mass of the entire Earth system, including the ocean tides. Errors in the GPS-based POD solutions for OSTM/Jason-2 of mm (3D RMS) and mm (radial RMS) are introduced when tidal geocenter variations are not treated consistently. Nevertheless, inconsistent treatment is measurable in the OSTM/Jason-2 POD solutions and manifests through degraded post-fit tracking data residuals, orbit precision, and relative orbit accuracy. For the latter metric, sea surface height crossover variance is higher by when tidal geocenter variations are treated inconsistently.

Desai, Shailen D.; Bertiger, Willy; Haines, Bruce J.

2014-08-01

221

Experimental Study on the Precise Orbit Determination of the BeiDou Navigation Satellite System  

PubMed Central

The regional service of the Chinese BeiDou satellite navigation system is now in operation with a constellation including five Geostationary Earth Orbit satellites (GEO), five Inclined Geosynchronous Orbit (IGSO) satellites and four Medium Earth Orbit (MEO) satellites. Besides the standard positioning service with positioning accuracy of about 10 m, both precise relative positioning and precise point positioning are already demonstrated. As is well known, precise orbit and clock determination is essential in enhancing precise positioning services. To improve the satellite orbits of the BeiDou regional system, we concentrate on the impact of the tracking geometry and the involvement of MEOs, and on the effect of integer ambiguity resolution as well. About seven weeks of data collected at the BeiDou Experimental Test Service (BETS) network is employed in this experimental study. Several tracking scenarios are defined, various processing schemata are designed and carried out; and then, the estimates are compared and analyzed in detail. The results show that GEO orbits, especially the along-track component, can be significantly improved by extending the tracking network in China along longitude direction, whereas IGSOs gain more improvement if the tracking network extends in latitude. The involvement of MEOs and ambiguity-fixing also make the orbits better. PMID:23529116

He, Lina; Ge, Maorong; Wang, Jiexian; Wickert, Jens; Schuh, Harald

2013-01-01

222

Orbit determination accuracies using satellite-to-satellite tracking  

NASA Technical Reports Server (NTRS)

The uncertainty in relay satellite sate is a significant error source which cannot be ignored in the reduction of satellite-to-satellite tracking data. Based on simulations and real data reductions, it is numerically impractical to use simultaneous unconstrained solutions to determine both relay and user satellite epoch states. A Bayesian or least squares estimation technique with an a priori procedure is presented which permits the adjustment of relay satellite epoch state in the reduction of satellite-to-satellite tracking data without the numerical difficulties introduced by an ill-conditioned normal matrix.

Vonbun, F. O.; Argentiero, P. D.; Schmid, P. E.

1977-01-01

223

Investigating On-Orbit Attitude Determination Anomalies for the Solar Dynamics Observatory Mission  

NASA Technical Reports Server (NTRS)

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 following the oscillating biases, resulting in movement of the spacecraft on the order of plus or minus 20 arcsec. Though this level of error met the ACS attitude knowledge requirement of [35, 70, 70] arcsec, 3 sigma, the desire of the ACS and instrument teams was to remove as much of the oscillation as possible. The Kearfott IRUs have an internal temperature controller, designed to maintain the IRU temperature at a constant temperature of approximately 70 C, thus minimizing the change in the bias drift and scale factors of the mechanical gyros. During ground testing of the observatory, it was discovered that the 83-Hz control cycle of the IRU heaters put a tremendous amount of stress on the spacecraft battery. Analysis by the power systems team indicated that the constant charge/discharge on the battery due to the IRU thermal control cycle could potentially limit the life of the battery. After much analysis, the decision was made not to run the internal IRU heaters. Analysis of on orbit data revealed that the oscillations in the IRU bias had a connection to the temperature of the IRU; changes in IRU temperature resulted in changes in the amplitude and period of the IRU biases. Several mitigating solutions were investigated, the result of which was to tune the KF with larger IRU noise assumptions which allows the KF to follow and correct for the time-varying IRU biases.

Vess, Melissa F.; Starin, Scott R.; Chia-Kuo, Alice Liu

2011-01-01

224

DETERMINATION OF ORBITAL ELEMENTS OF SPECTROSCOPIC BINARIES USING HIGH-DISPERSION SPECTROSCOPY  

SciTech Connect

Orbital elements of 37 single-lined spectroscopic binary systems (SB1s) and 5 double-lined spectroscopic binary systems (SB2s) were determined using high-dispersion spectroscopy. To determine the orbital elements accurately, we carried out precise Doppler shift measurements using the HIgh Dispersion Echelle Spectrograph mounted on the Okayama Astrophysical Observatory 1.88 m telescope. We achieved a radial-velocity precision of {approx}10 m s{sup -1} over seven years of observations. The targeted binaries have spectral types between F5 and K3, and are brighter than the 7th magnitude in the V band. The orbital elements of 28 SB1s and 5 SB2s were determined at least 10 times more precisely than previous measurements. Among the remaining nine SB1s, five objects were found to be single stars, and the orbital elements of four objects were not determined because our observations did not cover the entire orbital period. We checked the absorption lines from the secondary star for 28 SB1s and found that three objects were in fact SB2s.

Katoh, Noriyuki [Graduate School of Science, Kobe University, 1-1 Rokkoudai, Nada-ku, Kobe, Hyogo 657-8501 (Japan); Itoh, Yoichi [Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, 407-2 Nishigaichi, Sayo, Sayo, Hyogo 679-5313 (Japan); Toyota, Eri [Kobe Science Museum, 7-7-6 Minatojimanakacho, Chou-ku, Kobe, Hyogo 650-0046 (Japan); Sato, Bun'ei [Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)

2013-02-01

225

Cassini Orbit Determination Performance during Saturn Satellite Tour: August 2005 - January 2006  

NASA Technical Reports Server (NTRS)

During the period spanning the second Enceladus flyby in July 2005 through the eleventh Titan encounter in January 2006, the Cassini spacecraft was successfully navigated through eight close-targeted satellite encounters. Three of these encounters included the 500 km flybys of the icy satellites Hyperion, Dione and Rhea and five targeted flybys of Saturn's largest moon, Titan. This paper will show how our refinements to Saturn's satellite ephemerides have improved orbit determination predictions. These refinements include the mass estimates of Saturn and its satellites by better than 0.5%. Also, it will be shown how this better orbit determination performance has helped to eliminate several statistical maneuvers that were scheduled to clean-up orbit determination and/or maneuver-execution errors.

Antreasian, Peter G.; Bordi, J. J.; Criddle, K. E.; Ionasescu, R.; Jacobson, R. A.; Jones, J. B.; MacKenzie, R. A.; Parcher, D. W.; Pelletier, F. J.; Roth, D. C.; Stauch, J. R.

2007-01-01

226

Mineral identification from orbit: Initial results from the shuttle multispectral infrared radiometer  

USGS Publications Warehouse

A shuttle-borne radiometer containing ten channels in the reflective infrared has demonstrated that direct identification of carbonates and hydroxyl-bearing minerals is possible by remote measurement from Earth orbit. Copyright ?? 1982 AAAS.

Goetz, A.F.H.; Rowan, L.C.; Kingston, M.J.

1982-01-01

227

Phase Function Determination in Support of Orbital Debris Size Estimation  

NASA Technical Reports Server (NTRS)

To recover the size of a space debris object from photometric measurements, it is necessary to determine its albedo and basic shape: if the albedo is known, the reflective area can be calculated; and if the shape is known, the shape and area taken together can be used to estimate a characteristic dimension. Albedo is typically determined by inferring the object s material type from filter photometry or spectroscopy and is not the subject of the present study. Object shape, on the other hand, can be revealed from a time-history of the object s brightness response. The most data-rich presentation is a continuous light-curve that records the object s brightness for an entire sensor pass, which could last for tens of minutes to several hours: from this one can see both short-term periodic behavior as well as brightness variations with phase angle. Light-curve interpretation, however, is more art than science and does not lend itself easily to automation; and the collection method, which requires single-object telescope dedication for long periods of time, is not well suited to debris survey conditions. So one is led to investigate how easily an object s brightness phase function, which can be constructed from the more survey-friendly point photometry, can be used to recover object shape. Such a recovery is usually attempted by comparing a phase-function curve constructed from an object s empirical brightness measurements to analytically-derived curves for basic shapes or shape combinations. There are two ways to accomplish this: a simple averaged brightness-versus phase curve assembled from the empirical data, or a more elaborate approach in which one is essentially calculating a brightness PDF for each phase angle bin (a technique explored in unpublished AFRL/RV research and in Ojakangas 2011); in each case the empirical curve is compared to analytical results for shapes of interest. The latter technique promises more discrimination power but requires more data; the former can be assembled in its essentials from fewer measurements but will be less definitive in its assignments. The goal of the present study is to evaluate both techniques under debris survey conditions to determine their relative performance and, additionally, to learn precisely how a survey should be conducted in order to maximize their performance. Because the distendedness of objects has more of an effect than their precise shape in calculating a characteristic dimension, one is interested in the techniques discrimination ability to distinguish between an elongated rectangular prism and a short rectangular prism or cube, or an elongated cylinder from a squat cylinder or sphere. Sensitivity studies using simulated data will be conducted to determine discrimination power for both techniques as a function of amount of data collected and range (and specific region) of phase angles sampled. Empirical GEODSS photometry data for distended objects (dead payloads with solar panels, rocket bodies) and compact objects (cubesats, calibration spheres, squat payloads) will also be used to test this discrimination ability. The result will be a recommended technique and data collection paradigm for debris surveys in order to maximize this type of discrimination.

Hejduk, M. D.; Cowardin, H. M.; Stansbery, Eugene G.

2012-01-01

228

Landsat-4 (TDRSS-user) orbit determination using batch least-squares and sequential methods  

NASA Technical Reports Server (NTRS)

TDRSS user orbit determination is analyzed using a batch least-squares method and a sequential estimation method. It was found that in the batch least-squares method analysis, the orbit determination consistency for Landsat-4, which was heavily tracked by TDRSS during January 1991, was about 4 meters in the rms overlap comparisons and about 6 meters in the maximum position differences in overlap comparisons. The consistency was about 10 to 30 meters in the 3 sigma state error covariance function in the sequential method analysis. As a measure of consistency, the first residual of each pass was within the 3 sigma bound in the residual space.

Oza, D. H.; Jones, T. L.; Hakimi, M.; Samii, M. V.; Doll, C. E.; Mistretta, G. D.; Hart, R. C.

1992-01-01

229

Desaturation manoeuvres and precise orbit determination for the BepiColombo mission  

NASA Astrophysics Data System (ADS)

This work analyses the consequences that the desaturation manoeuvres can have on the precise orbit determination corresponding to the Mercury Orbiter Radioscience Experiment (MORE) of the BepiColombo mission to Mercury. This is an ESA/JAXAjoint project with challenging objectives regarding geodesy, geophysics and fundamental physics. We will show how these manoeuvres affect the orbit of the s/c and the radio science measurements and how to include them in the orbit determination and parameter estimation procedure. The non-linear least-squares fit is applied on a set of observational arcs separated by intervals of time where the probe is not visible. With the current baseline of two ground stations, two manoeuvres are performed per day, one during the observing session and the other in the dark. To reach the scientific goals of the mission, they have to be treated as 'solve for quantities'. We developed a specific methodology based on the deterministic propagation of the orbit, which is able to deal with these variables, by connecting subsequent observational arcs in a smooth way. The numerical simulations demonstrate that this constrained multi-arc strategy is able to determine all the manoeuvres together with the other parameters of interest at a high level of accuracy.

Alessi, E. M.; Cicalò, S.; Milani, A.; Tommei, G.

2012-07-01

230

Accurate orbit determination strategies for the tracking and data relay satellites  

NASA Technical Reports Server (NTRS)

The National Aeronautics and Space Administration (NASA) has developed the Tracking and Data Relay Satellite (TDRS) System (TDRSS) for tracking and communications support of low Earth-orbiting satellites. TDRSS has the operational capability of providing 85% coverage for TDRSS-user spacecraft. TDRSS currently consists of five geosynchronous spacecraft and the White Sands Complex (WSC) at White Sands, New Mexico. The Bilateration Ranging Transponder System (BRTS) provides range and Doppler measurements for each TDRS. The ground-based BRTS transponders are tracked as if they were TDRSS-user spacecraft. Since the positions of the BRTS transponders are known, their radiometric tracking measurements can be used to provide a well-determined ephemeris for the TDRS spacecraft. For high-accuracy orbit determination of a TDRSS user, such as the Ocean Topography Experiment (TOPEX)/Poseidon spacecraft, high-accuracy TDRS orbits are required. This paper reports on successive refinements in improved techniques and procedures leading to more accurate TDRS orbit determination strategies using the Goddard Trajectory Determination System (GTDS). These strategies range from the standard operational solution using only the BRTS tracking measurements to a sophisticated iterative process involving several successive simultaneous solutions for multiple TDRSs and a TDRSS-user spacecraft. Results are presented for GTDS-generated TDRS ephemerides produced in simultaneous solutions with the TOPEX/Poseidon spacecraft. Strategies with different user spacecraft, as well as schemes for recovering accurate TDRS orbits following a TDRS maneuver, are also presented. In addition, a comprehensive assessment and evaluation of alternative strategies for TDRS orbit determination, excluding BRTS tracking measurements, are presented.

Oza, D. H.; Bolvin, D. T.; Lorah, J. M.; Lee, T.; Doll, C. E.

1995-01-01

231

First-principles determination of charge and orbital interactions in Fe3O4 Fei Zhou ( * and Gerbrand Ceder  

E-print Network

First-principles determination of charge and orbital interactions in Fe3O4 Fei Zhou; published 17 May 2010 The interactions between charge and orbitally ordered d electrons are important. The frustration between optimal charge and orbital orderings leads to a complex energy landscape whereby

Ceder, Gerbrand

232

Orbit Determination Analysis for a Joint UK-Australian Space Surveillance Experiment  

NASA Astrophysics Data System (ADS)

In February 2014 the UK and Australia carried out a joint space surveillance target tracking, cueing, and sensor data fusion experiment involving the STFC Chilbolton Observatory radar in the UK, the EOS laser-ranging system in Australia and a small telescope operated by DSTO, also in Australia. The experiment, coordinated by DSTL (UK) and DSTO (Aus), was designed to explore the combination of several different, geographically separated sensors for space situational awareness. The primary goal of the experiment was to use data from the radar in the UK to generate an orbital cue to the EOS SLR. A variety of targets sizes and orbits were chosen, under the limitations of observability by both the radar and EOS SLR, in order to explore the variation of cueing accuracy with amount of data incorporated and timeliness from generation. As a secondary objective the effect on cue accuracy of targets in lower orbital regimes was examined. This paper examines the orbit determination techniques used to generate cues from radar and the refined orbits resulting from accumulating SLR data. The construction of tracks using data from all three sensors is explored. Analysis of the accuracy of the orbital reconstructions is made based on comparisons with the measured data and accurate ephemerides provided by the ILRS. The accuracy is tested against the cueing precision requirements for each sensor. Two companion papers describe the experimental goals, execution and achievements (Harwood et. al.) and the sensor aspects of the experiment (Eastment et al.).

Rutten, M.; Harwood, N.; Bennett, J.; Donnelly, P.; Ash, A.; Eastment, J.; Ladd, D.; Gordon, N.; Bessell, T.; Smith, C.; Ritchie, I.

2014-09-01

233

Determination of orbital parameters of interacting galaxies using a genetic algorithm. Description of the method and application to artificial data  

E-print Network

A method for determining the orbital parameters of interacting pairs of galaxies is presented and evaluated using artificial data. The method consists of a genetic algorithm which can search efficiently through the very large space of possible orbits. It is found that, in most cases, orbital parameters close to the actual orbital parameters of the pair can be found. The method does not require information about the velocity field of the interacting system, and is able to cope with noisy data. The inner regions of the galaxies, which are difficult to model, can be neglected, and the orbital parameters can be determined using the remaining information.

M. Wahde

1997-10-24

234

First orbit determination with numerical methods based on short arcs acquired in space debris surveys  

NASA Astrophysics Data System (ADS)

Surveys for space debris aim at improving our knowledge of the space debris population. The survey results are fed either into space debris environment models or into orbital element catalogue of space debris objects, depending on whether the objects should be tracked later on. In both cases first orbit determination is a crucial step. The determined orbital elements together with estimated of the magnitude of the object allow first estimates of the object size. The orbital elements are also the central input to validate and improve the space debris environment models. Considering catalogue build-up and maintenance, the results from the first orbit determination set important constraints for the correlation of the new object with the catalogue, the re-acquisition and finally the identification of the object. In the case of space debris surveys first orbits must be determined from very short arcs of observations, which are due to the limits of the current sensor technology, in particular due to the limited field-of-view diameter of the telescopes used for optical surveys. The quality of the first orbits is in any case a function of the measurement accuracy. We present an approach for first orbit determination, which is derived from the boundary value method implemented in the CelMech program system (Beutler, 2005). The approach considers angular measurements, as derived from optical observation systems. The CelMech module ORBDET was generalized to perform a two-dimensional search by systematically varying the topocentric ranges at the boundary epochs of the observed arc. The search aims at identifying local minima of a least-square adjustment of all available observations using a truncated Taylor series to approximate the particular solution of the equation of motion for the debris considered. We apply this method to observations from ongoing space debris surveys of ESA using the 1-m telescope at the Optical Ground Station in Tenerife. Furthermore we apply this approach to a proposed space-based optical observation system. Last, but not least we consider the inclusion of range observations in our algorithm. Beutler G (2005) Methods of Celestial Mechanics. Springer, Berlin, Heidelberg, New York

Flohrer, Tim; Beutler, Gerhard; Schildknecht, Thomas

235

A modified genetic algorithm for precise determination the geometrical orbital elements of binary stars  

Microsoft Academic Search

The paper presents a modified genetic algorithm called adapted genetic algorithm with adjusting population size (AGA-POP) for precise determination the orbital elements of binary stars. The proposed approach is a simple, robust way that can be considered to be a new member in the class of self organizing genetic algorithms. The proposed AGA-POP is applied on the star ? Bootis

Abdel-Fattah Attia; Eman Mahmoud; H. I. Shahin; A. M. Osman

2009-01-01

236

Hubble and Planck scale limits on the determination of orbital angular momentum states of light  

E-print Network

We review Heisenberg's uncertainty principle for the orbital angular momentum (OAM) of light. By taking into account the largest and smallest scales present in nature, such as the the Hubble radius and the Planck length, we have found that there exist upper and lower physical limits to the determination of the OAM of a photon.

F. Tamburini; B. Thidé; A. Sponselli

2012-01-16

237

An X-ray determination of the orbital elements of 3U 0900-40  

NASA Technical Reports Server (NTRS)

The orbital elements of the 3U 0900-40 binary system were determined by measuring the variations in the arrival times of the 283-second X-ray pulses. The best-fit values of the system parameters and their 95% confidence limits are listed.

Mcclintock, J.; Joss, P. C.; Rappaport, S.

1976-01-01

238

Short arc orbit determination for altimeter calibration and validation on TOPEX/POSEIDON  

NASA Technical Reports Server (NTRS)

TOPEX/POSEIDON (T/P) is a joint mission of United States' National Aeronautics and Space Administration (NASA) and French Centre National d'Etudes Spatiales (CNES) design launched August 10, 1992. It carries two radar altimeters which alternately share a common antenna. There are two project designated verification sites, a NASA site off the coast at Pt. Conception, CA and a CNES site near Lampedusa Island in the Mediterranean Sea. Altimeter calibration and validation for T/P is performed over these highly instrumented sites by comparing the spacecraft's altimeter radar range to computed range based on in situ measurements which include the estimated orbit position. This paper presents selected results of orbit determination over each of these sites to support altimeter verification. A short arc orbit determination technique is used to estimate a locally accurate position determination of T/P from less than one revolution of satellite laser ranging (SLR) data. This technique is relatively insensitive to gravitational and non-gravitational force modeling errors and is demonstrated by covariance analysis and by comparison to orbits determined from longer arcs of data and other tracking data types, such as Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) and Global Positioning System Demonstration Receiver (GPSDR) data.

Williams, B. G.; Christensen, E. J.; Yuan, D. N.; Mccoll, K. C.; Sunseri, R. F.

1993-01-01

239

NORAD TLE Type Orbit Determination of LEO Satellites Using GPS Navigation Solutions  

Microsoft Academic Search

NORAD Two Line Elements (TLE) are widely used for the increasing number of small satellite mission operations and analysis. However, due to the irregular periodicity of generation of the NORAD TLE, a new TLE that is independent of NORAD is required. A TLE type Orbit Determination (TLEOD) has been developed for the generation of a new TLE. Thus, the TLEOD

Chang-Hwa Cho; Byoung-Sun Lee; Jeong-Sook Lee; Jae-Hoon Kim; Kyu-Hong Choi

2002-01-01

240

Determination of orbit chaoticity indicators with analytically normalized tangent vector. (Russian Title: ??????????? ??????????? ??????????? ????? ? ???????????? ????????????? ??????????? ???????? )  

NASA Astrophysics Data System (ADS)

Transformations of differential equations of the methods for determining the Lyapunov Characteristic Indicator and MEGNO indicators are suggested. The transformations improve the behavior of the differential equations by their simultaneous numerical integration. The use of the transformed equations is especially efficient for the investigation of orbits in stochastic regimes.

Shefer, V. A.

2011-07-01

241

Houston Operations Predictor/Estimator (HOPE) programming manual, volume 1. [Apollo orbit determination  

NASA Technical Reports Server (NTRS)

The programming techniques used to implement the equations and mathematical techniques of the Houston Operations Predictor/Estimator (HOPE) orbit determination program on the UNIVAC 1108 computer are described. Detailed descriptions are given of the program structure, the internal program structure, the internal program tables and program COMMON, modification and maintainence techniques, and individual subroutine documentation.

Daly, J. K.

1974-01-01

242

Satellite Orbit Determination Using a Single-Channel Global Positioning System Receiver by Mark L. Psiaki  

E-print Network

Satellite Orbit Determination Using a Single-Channel Global Positioning System Receiver by Mark L system has been analyzed, one that uses measurements from a single-channel Global Positioning System (GPS. Introduction The Global Positioning System (GPS) offers an attractive alternative to ground-based tracking

Psiaki, Mark L.

243

MASS AND ORBIT DETERMINATION FROM TRANSIT TIMING VARIATIONS OF EXOPLANETS David Nesvorny1  

E-print Network

MASS AND ORBIT DETERMINATION FROM TRANSIT TIMING VARIATIONS OF EXOPLANETS David Nesvorny´1 of transits of an exoplanet provide means of detecting additional planets in the system. The short-period and resonant variations of the transit signal are probably the most diagnostic of the perturbing planet's mass

Morbidelli, Alessandro

244

Autonomous determination of relative orbit for satellite formation flying using fault tolerant UKF  

Microsoft Academic Search

In the universe, the outliers always be included in the devices used for measuring on satellite, which affect the orthogonal property of Filter innovation sequence, filtering accuracy and make estimation inaccurate. In this paper, based on residual orthogonal UKF fault tolerant filtering method is used for autonomous determination of relative orbit for satellite formation flying, the outliers eliminating and instant

Wang Hui; Gu Xuemai

2009-01-01

245

A Decision-Making Framework to Determine the Value of On-Orbit Servicing  

E-print Network

;#12;Dedicated to the astronauts of Apollo 1, Space Shuttle Challenger, and Space Shuttle Columbia, who gave of Space Telescopes Mark Baldesarra, Professor David W. Miller June 2007 SSL # 13-07 #12;A Decision-Making Framework to Determine the Value of On-Orbit Servicing Compared to Replacement of Space Telescopes by Mark

246

N-observations and radar orbits  

Microsoft Academic Search

Initial asteriod orbits are determined by a least squares adjustment of an arbitrary number (N) of optical and radar observations. The usual separation, into an orbit determination by three observations and a subsequent differential orbit improvement, is combined into a single algorithm. A priori information is used for very small arcs. Ephemerides very suitable for linking are obtained by strictly

Leif Kahl Kristensen

2007-01-01

247

Determination of ASPS performance for large payloads in the shuttle orbiter disturbance environment. [digital simulation  

NASA Technical Reports Server (NTRS)

A high fidelity simulation of the annular suspension and pointing system (ASPS), its payload, and the shuttle orbiter was used to define the worst case orientations of the ASPS and its payload for the various vehicle disturbances, and to determine the performance capability of the ASPS under these conditions. The most demanding and largest proposed payload, the Solar Optical Telescope was selected for study. It was found that, in all cases, the ASPS more than satisfied the payload's requirements. It is concluded that, to satisfy facility class payload requirements, the ASPS or a shuttle orbiter free-drift mode (control system off) should be utilized.

Keckler, C. R.; Kibler, K. S.; Powell, L. F.

1979-01-01

248

Improved treatment of global positioning system force parameters in precise orbit determination applications  

NASA Technical Reports Server (NTRS)

Data collected from a worldwide 1992 experiment were processed at JPL to determine precise orbits for the satellites of the Global Positioning System (GPS). A filtering technique was tested to improve modeling of solar-radiation pressure force parameters for GPS satellites. The new approach improves orbit quality for eclipsing satellites by a factor of two, with typical results in the 25- to 50-cm range. The resultant GPS-based estimates for geocentric coordinates of the tracking sites, which include the three DSN sites, are accurate to 2 to 8 cm, roughly equivalent to 3 to 10 nrad of angular measure.

Vigue, Y.; Lichten, S. M.; Muellerschoen, R. J.; Blewitt, G.; Heflin, M. B.

1993-01-01

249

20 CFR 405.210 - How to request review of an initial determination.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false How to request review of an initial determination. 405.210...SECURITY ADMINISTRATION ADMINISTRATIVE REVIEW PROCESS FOR ADJUDICATING INITIAL DISABILITY CLAIMS Review of Initial Determinations by a...

2010-04-01

250

20 CFR 405.210 - How to request review of an initial determination.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false How to request review of an initial determination. 405.210...SECURITY ADMINISTRATION ADMINISTRATIVE REVIEW PROCESS FOR ADJUDICATING INITIAL DISABILITY CLAIMS Review of Initial Determinations by a...

2011-04-01

251

NORAD TLE Type Orbit Determination of LEO Satellites Using GPS Navigation Solutions  

NASA Astrophysics Data System (ADS)

NORAD Two Line Elements (TLE) are widely used for the increasing number of small satellite mission operations and analysis. However, due to the irregular periodicity of generation of the NORAD TLE, a new TLE that is independent of NORAD is required. A TLE type Orbit Determination (TLEOD) has been developed for the generation of a new TLE. Thus, the TLEOD system can provide an Antenna Control Unit (ACU) with the orbit determination result in the type of a TLE, which provides a simple interface for the commercialized ACU system. For the TLEOD system, NORAD SGP4 was used to make a new orbit determination system. In addition, a least squares method was implemented for the TLEOD system with the GPS navigation solutions of the KOMPSAT-1. Considering both the Orbit Propagation (OP) difference and the tendency of B* value, the preferable span of the day in the observation data was selected to be 3 days. Through the OD with 3 days observation data, the OP difference was derived and compared with that of Mission Analysis and Planning (MAPS) for the KOMPSAT-1. It has the extent from 2 km after six days to 4 km after seven days. This is qualified enough for the efficiency of an ACU in image reception and processing center of the KOMPSAT-2.

Cho, Chang-Hwa; Lee, Byoung-Sun; Lee, Jeong-Sook; Kim, Jae-Hoon; Choi, Kyu-Hong

2002-09-01

252

A multi-satellite orbit determination problem in a parallel processing environment  

NASA Technical Reports Server (NTRS)

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.

Deakyne, M. S.; Anderle, R. J.

1988-01-01

253

The effects of geopotential resonance on orbit determination for Landsat-4  

NASA Technical Reports Server (NTRS)

Analysis is presented demonstrating improved performance for Landsat-4 orbit determination using the Goddard Trajectory Determination System with an adjusted Goddard Earth Model-9 (GEM-9) for geopotential coefficients of the 15th degree and order. The orbital state is estimated along with the sine and cosine coefficients of degree and order 15, (C, S) sub 15,15. The estimates are made for two 5-day intervals of range and doppler data, primarily from the Tracking and Data Relay Satellite, during a period of low solar activity in January 1987. The average values of the estimated coefficients (C, S) sub 15,15 are used to modify the GEM-9 model, and orbit determination performance is tested on 17 consecutive 34-hour operational tracking data arcs in January 1987. Significant reductions in the mean values and standard deviations of the along-track position difference and the drag model scaling parameter from solution to solution are observed. The approach is guided by the shallow resonance theory of geopotential orbit perturbations.

Hoge, S. L.; Casteel, D. O.; Phenneger, M. C.; Smith, E. A.

1988-01-01

254

The GLAS Algorithm Theoretical Basis Document for Precision Orbit Determination (POD)  

NASA Technical Reports Server (NTRS)

The Geoscience Laser Altimeter System (GLAS) was the sole instrument for NASA's Ice, Cloud and land Elevation Satellite (ICESat) laser altimetry mission. The primary purpose of the ICESat mission was to make ice sheet elevation measurements of the polar regions. Additional goals were to measure the global distribution of clouds and aerosols and to map sea ice, land topography and vegetation. ICESat was the benchmark Earth Observing System (EOS) mission to be used to determine the mass balance of the ice sheets, as well as for providing cloud property information, especially for stratospheric clouds common over polar areas. The GLAS instrument operated from 2003 to 2009 and provided multi-year elevation data needed to determine changes in sea ice freeboard, land topography and vegetation around the globe, in addition to elevation changes of the Greenland and Antarctic ice sheets. This document describes the Precision Orbit Determination (POD) algorithm for the ICESat mission. The problem of determining an accurate ephemeris for an orbiting satellite involves estimating the position and velocity of the satellite from a sequence of observations. The ICESatGLAS elevation measurements must be very accurately geolocated, combining precise orbit information with precision pointing information. The ICESat mission POD requirement states that the position of the instrument should be determined with an accuracy of 5 and 20 cm (1-s) in radial and horizontal components, respectively, to meet the science requirements for determining elevation change.

Rim, Hyung Jin; Yoon, S. P.; Schultz, Bob E.

2013-01-01

255

The determination of maximum deep space station slew rates for a high Earth orbiter  

NASA Technical Reports Server (NTRS)

As developing national and international space ventures, which seek to employ NASA's Deep Space Network (DSN) for tracking and data acquisition, evolve, it is essential for navigation and tracking system analysts to evaluate the operational capability of Deep Space Station antennas. To commission the DSN for use in tracking a highly eccentric Earth orbiter could quite possibly yield the greatest challenges in terms of slewing capability; certainly more so than with a deep-space probe. The focus here is on the determination of the maximum slew rates needed to track a specific high Earth orbiter, namely the Japanese MUSES-B spacecraft of the Very Long Baseline Interferometry Space Observatory Program. The results suggest that DSN 34-m antennas are capable of meeting the slew rate requirements for the nominal MUSES-B orbital geometries currently being considered.

Estefan, J. A.

1990-01-01

256

Determination of the area and mass distribution of orbital debris fragments  

NASA Technical Reports Server (NTRS)

A technique is described to estimate the area-to-mass ratio of debris fragments using orbital fragments obtained by radar. The area-to-mass ratio of about 2600 fragments arising from the breakup of 24 artificial satellites was determined; an analysis of the data on about 200 objects with known mass, size, and shape has been made, and a calibration of the observed radar cross-section (RCS) to the effective area of these objects has provided a method to estimate the effective area of debris fragments. From the knowledge of the effective area and the estimated area-to-mass ratio, the mass and area distribution of each of the known breakup has been obtained. As a function of time, the orbital elements can be used to invert any propagation algorithm to yield the area-to-mass ratio of an orbiting object.

Badhwar, Gautam D.; Anz-Meador, Phillip D.

1989-01-01

257

TOPEX/POSEIDON operational orbit determination results using global positioning satellites  

NASA Technical Reports Server (NTRS)

Results of operational orbit determination, performed as part of the TOPEX/POSEIDON (T/P) Global Positioning System (GPS) demonstration experiment, are presented in this article. Elements of this experiment include the GPS satellite constellation, the GPS demonstration receiver on board T/P, six ground GPS receivers, the GPS Data Handling Facility, and the GPS Data Processing Facility (GDPF). Carrier phase and P-code pseudorange measurements from up to 24 GPS satellites to the seven GPS receivers are processed simultaneously with the GDPF software MIRAGE to produce orbit solutions of T/P and the GPS satellites. Daily solutions yield subdecimeter radial accuracies compared to other GPS, LASER, and DORIS precision orbit solutions.

Guinn, J.; Jee, J.; Wolff, P.; Lagattuta, F.; Drain, T.; Sierra, V.

1994-01-01

258

Precise orbit determination using the batch filter based on particle filtering with genetic resampling approach  

NASA Astrophysics Data System (ADS)

In this study, genetic resampling (GRS) approach is utilized for precise orbit determination (POD) using the batch filter based on particle filtering (PF). Two genetic operations, which are arithmetic crossover and residual mutation, are used for GRS of the batch filter based on PF (PF batch filter). For POD, Laser-ranging Precise Orbit Determination System (LPODS) and satellite laser ranging (SLR) observations of the CHAMP satellite are used. Monte Carlo trials for POD are performed by one hundred times. The characteristics of the POD results by PF batch filter with GRS are compared with those of a PF batch filter with minimum residual resampling (MRRS). The post-fit residual, 3D error by external orbit comparison, and POD repeatability are analyzed for orbit quality assessments. The POD results are externally checked by NASA JPL’s orbits using totally different software, measurements, and techniques. For post-fit residuals and 3D errors, both MRRS and GRS give accurate estimation results whose mean root mean square (RMS) values are at a level of 5 cm and 10-13 cm, respectively. The mean radial orbit errors of both methods are at a level of 5 cm. For POD repeatability represented as the standard deviations of post-fit residuals and 3D errors by repetitive PODs, however, GRS yields 25% and 13% more robust estimation results than MRRS for post-fit residual and 3D error, respectively. This study shows that PF batch filter with GRS approach using genetic operations is superior to PF batch filter with MRRS in terms of robustness in POD with SLR observations.

Kim, Young-Rok; Park, Eunseo; Choi, Eun-Jung; Park, Sang-Young; Park, Chandeok; Lim, Hyung-Chul

2014-09-01

259

GPS-Based Navigation and Orbit Determination for the AMSAT Phase 3D Satellite  

NASA Technical Reports Server (NTRS)

This paper summarizes the results of processing GPS data from the AMSAT Phase 3D (AP3) satellite for real-time navigation and post-processed orbit determination experiments. AP3 was launched into a geostationary transfer orbit (GTO) on November 16, 2000 from Kourou, French Guiana, and then was maneuvered into its HEO over the next several months. It carries two Trimble TANS Vector GPS receivers for signal reception at apogee and at perigee. Its spin stabilization mode currently makes it favorable to track GPS satellites from the backside of the constellation while at perigee, and to track GPS satellites from below while at perigee. To date, the experiment has demonstrated that it is feasible to use GPS for navigation and orbit determination in HEO, which will be of great benefit to planned and proposed missions that will utilize such orbits for science observations. It has also shown that there are many important operational considerations to take into account. For example, GPS signals can be tracked above the constellation at altitudes as high as 58000 km, but sufficient amplification of those weak signals is needed. Moreover, GPS receivers can track up to 4 GPS satellites at perigee while moving as fast as 9.8 km/sec, but unless the receiver can maintain lock on the signals long enough, point solutions will be difficult to generate. The spin stabilization of AP3, for example, appears to cause signal levels to fluctuate as other antennas on the satellite block the signals. As a result, its TANS Vectors have been unable to lock on to the GPS signals long enough to down load the broadcast ephemeris and then generate position and velocity solutions. AP3 is currently in its eclipse season, and thus most of the spacecraft subsystems have been powered off. In Spring 2002, they will again be powered up and AP3 will be placed into a three-axis stabilization mode. This will significantly enhance the likelihood that point solutions can be generated, and perhaps more important, that the receiver clock can be synchronized to GPS time. This is extremely important for real-time and post-processed orbit determination, where removal of receiver clock bias from the data time tags is needed, for time-tagging of science observations. Current analysis suggests that the inability to generate point solutions has allowed the TANS Vector clock bias to drift freely, being perhaps as large as 5-7 seconds by October, 2001, thus causing up to 50 km of along-track orbit error. The data collected in May, 2002 while in three-axis stabilized mode should provide a significant improvement in the orbit determination results.

Davis, George; Carpenter, Russell; Moreau, Michael; Bauer, Frank H.; Long, Anne; Kelbel, David; Martin, Thomas

2002-01-01

260

N -observations and radar orbits  

Microsoft Academic Search

Initial asteriod orbits are determined by a least squares adjustment of an arbitrary number (N) of optical and radar observations. The usual separation, into an orbit determination by three observations and a subsequent\\u000a differential orbit improvement, is combined into a single algorithm. A priori information is used for very small arcs. Ephemerides\\u000a very suitable for linking are obtained by strictly

Leif Kahl Kristensen

2007-01-01

261

Orbit Determination of the SELENE Satellites Using Multi-Satellite Data Types and Evaluation of SELENE Gravity Field Models  

NASA Technical Reports Server (NTRS)

The SELENE mission, consisting of three separate satellites that use different terrestrial-based tracking systems, presents a unique opportunity to evaluate the contribution of these tracking systems to orbit determination precision. The tracking data consist of four-way Doppler between the main orbiter and one of the two sub-satellites while the former is over the far side, and of same-beam differential VLBI tracking between the two sub-satellites. Laser altimeter data are also used for orbit determination. The contribution to orbit precision of these different data types is investigated through orbit overlap analysis. It is shown that using four-way and VLBI data improves orbit consistency for all satellites involved by reducing peak values in orbit overlap differences that exist when only standard two-way Doppler and range data are used. Including laser altimeter data improves the orbit precision of the SELENE main satellite further, resulting in very smooth total orbit errors at an average level of 18m. The multi-satellite data have also resulted in improved lunar gravity field models, which are assessed through orbit overlap analysis using Lunar Prospector tracking data. Improvements over a pre-SELENE model are shown to be mostly in the along-track and cross-track directions. Orbit overlap differences are at a level between 13 and 21 m with the SELENE models, depending on whether l-day data overlaps or I-day predictions are used.

Goossens, S.; Matsumoto, K.; Noda, H.; Araki, H.; Rowlands, D. D.; Lemoine, F. G.

2011-01-01

262

Analysis of Multi-Satellite Tracking Data of the Kaguya Satellites for Orbit and Gravity Field Determination  

NASA Astrophysics Data System (ADS)

The Kaguya spacecraft were launched from Tanegashima Space Center on September 14, 2007. Kaguya consists of three orbiters: a main orbiter in a low-altitude (100 km) circular polar orbit, and two sub-satellites (Rstar and Vstar) in elliptical orbits. The satellites were tracked by a variety of terrestrial based tracking systems: in addition to standard two-way Doppler and range tracking, there was 4-way Doppler tracking between Rstar and the main orbiter, providing the first tracking data of a satellite over the lunar far side, and there was same-beam differential VLBI tracking between the two sub-satellites, providing precise orbits for these satellites. The main orbiter was also equipped with a laser altimeter (LALT) to measure the topography of the Moon. At points where the ground tracks of different orbits intersect, these data can provide further constraints on the orbit of the main satellite in the form of crossovers, as essentially the same topography should be measured. This comprehensive data set between the satellites allows for a unique opportunity to evaluate the contribution of these tracking systems to orbit and gravity field determination. Precise orbits are important for geolocation of the topography and camera data, whereas the gravity field can be used for studies of the lunar interior. Here, we present the analysis of the combinations of these tracking data. The use of 4-way and same-beam differential VLBI data leads to large improvements in orbit precision of all satellites involved, where especially peaks in orbit overlap differences during edge-on periods are reduced. The use of the altimetry crossovers improves the orbit of the main satellite further, resulting in an orbit precision of in general less than 20 m. We have also used the full set of SELENE tracking data (including all 4-way and all S-band same-beam differential VLBI data), together with historical data, for gravity field determination. We show a lunar gravity field model with an improved orbit determination performance, especially for orbits over the deep far side. Finally, we use the improved gravity field model to investigate the determination of the lower degrees of the spherical harmonics expansion. These results thus show the benefits from having multiple spacecraft tracking for orbit and gravity field determination.

Goossens, S. J.; Matsumoto, K.; Kikuchi, F.; Liu, Q.; Hanada, H.; Lemoine, F. G.; Rowlands, D. D.; Ishihara, Y.; Jianguo, Y.; Araki, H.; Noda, H.; Namiki, N.; Iwata, T.

2010-12-01

263

Technique for rapid determination of relative ages of lunar areas from orbital photography.  

NASA Technical Reports Server (NTRS)

Development of a technique for determining relative ages of regions of the lunar surface from orbital photography using a model of small-impact erosion. The erosion model relates the shape of a crater to the integrated flux of debris that has impacted the surface since that crater was fresh. The shape of the most modified crater of a particular diameter is thereby related to the relative age of the surface. Application of this analysis to orbital photography reveals that the major mare units vary in the accumulation of impacts by more than a factor of 3. Comparison of these data with crystallization ages determined from samples collected during the Apollo 11 and 12 missions indicates that the impact fluxes were decreasing during the stages of mare formation. An exponentially decaying flux for the last 3.5 b.y. with a half-life of 0.6 to 1.4 b.y. is compatible with the data.

Soderblom, L. A.; Lebofsky, L. A.

1972-01-01

264

Atmospheric drag model for Cassini orbit determination during low altitude Titan flybys  

NASA Technical Reports Server (NTRS)

On April 16, 2005, the Cassini spacecraft performed its lowest altitude flyby of Titan to date, the Titan-5 flyby, flying 1027 km above the surface of Titan. This document discusses the development of a Titan atmospheric drag model for the purpose of the orbit determination of Cassini. Results will be presented for the Titan A flyby, the Titan-5 flyby as well as the most recent low altitude Titan flyby, Titan-7. Different solutions will be compared against OD performance in terms of the flyby B-plane parameters, spacecraft thrusting activity and drag estimates. These low altitude Titan flybys were an excellent opportunity to observe the effect of Titan's atmospheric drag on the orbit determination solution and results show that the drag was successfully modeled to provide accurate flyby solutions.

Pelletier, F. J.; Antreasian, P. G.; Bordi, J. J.; Criddle, K. E.; Ionasescu, R.; Jacobson, R. A.; Mackenzie, R. A.; Parcher, D. W.; Stauch, J. R.

2006-01-01

265

An information fusion algorithm for integrated autonomous orbit determination of navigation satellites  

NASA Astrophysics Data System (ADS)

This paper focuses on the information fusion problem of integrated autonomous orbit determination using the observations from inter-satellite-link (ISL), X-ray pulsars and star sensors. A step Kalman filter structure is proposed to solve the information fusion problem of multiple subsystems that have greatly different filtering precision. The subsystems are grouped according to their measurement accuracy and the state parameters and covariance matrix of a group can be calculated using the federated filter structure and propagated to the next group step-by-step. Simulation results show that the mean user range error (URE) of the constellation will be less than 1.5 m in 60 days using the step Kalman filter structure for information fusion. And it has better performance than the federated structure in dealing with information fusion of the astronomical observations and the ISL ranging measurements in integrated autonomous orbit determination.

Shang, Lin; Liu, Guohua; Zhang, Rui; Li, Guotong

2013-04-01

266

Constructive Axiomatic Approach to the Determination of the Orbit Spaces of Coregular Compact Linear Groups  

Microsoft Academic Search

We review the proposal of a constructive axiomatic approach to the determination of the orbit spaces of all the real compact linear groups, obtained through the computation of a metric matrix \\u000a\\u000a\\u000a, which is defined only in terms of the scalar products between the gradients ?p1(x),.?.?.,?pq(x) of the elements of a minimal integrity basis (MIB) for the ring R[Rn]G of

G. Sartori; G. Valente

2005-01-01

267

Determination of periodic orbits of nonlinear oscillators by means of piecewise-linearization methods  

Microsoft Academic Search

An approximate method based on piecewise linearization is developed for the determination of periodic orbits of nonlinear oscillators. The method is based on Taylor series expansions, provides piecewise analytical solutions in three-point intervals which are continuous everywhere and explicit three-point difference equations which are P-stable and have an infinite interval of periodicity. It is shown that the method presented here

J. I. Ramos

2006-01-01

268

Comparison of Sigma-Point and Extended Kalman Filters on a Realistic Orbit Determination Scenario  

NASA Technical Reports Server (NTRS)

Sigma-point filters have received a lot of attention in recent years as a better alternative to extended Kalman filters for highly nonlinear problems. In this paper, we compare the performance of the additive divided difference sigma-point filter to the extended Kalman filter when applied to orbit determination of a realistic operational scenario based on the Interstellar Boundary Explorer mission. For the scenario studied, both filters provided equivalent results. The performance of each is discussed in detail.

Gaebler, John; Hur-Diaz. Sun; Carpenter, Russell

2010-01-01

269

Preliminary study of GPS orbit determination accuracy achievable from worldwide tracking data  

NASA Technical Reports Server (NTRS)

The improvement in the orbit accuracy if high accuracy tracking data from a substantially larger number of ground stations is available was investigated. Observations from 20 ground stations indicate that 20 cm or better accuracy can be achieved for the horizontal coordinates of the GPS satellites. With this accuracy, the contribution to the error budget for determining 1000 km baselines by GPS geodetic receivers would be only about 1 cm.

Larden, D. R.; Bender, P. L.

1982-01-01

270

Application of the total least squares method to the determination of preliminary orbit  

NASA Astrophysics Data System (ADS)

Based on the analysis of the characteristics of the equations of condition in the UVM2 (Unit Vector Method 2), the total least squares method (TLS) is introduced into the orbital determination and the linearization of the vis-viva formula in the original algorithm is thereby avoided. The calculated results from simulation and observation data show that the application of TLS to UVM2 is effective.

Chen, Wu-shen; Zhang, Jing; Ma, Jing-yuan; Lu, Ben-kui

2006-10-01

271

Determination Of The Orbit Of The Planetary Companion To The Metal Rich Star HD 45350  

E-print Network

We present the precise radial velocity (RV) data for the metal-rich star HD 45350 collected with the Harlan J. Smith (HJS) 2.7 m telescope and the Hobby-Eberly Telescope (HET) at McDonald Observatory. This star was noticed by us as a candidate for having a giant planetary companion in a highly eccentric orbit, but the lack of data close to periastron left the amplitude and thus mass of the planet poorly constrained. Marcy et al. (2005) announced the presence of the planet based on their Keck/HIRES data, but those authors also cautioned that the remaining uncertainties in the orbital solution might be large due to insufficient data near periastron passage. In order to close this phase gap we exploited the flexible queue scheduled observing mode of the HET to obtain intensive coverage of the most recent periastron passage of the planet. In combination with the long term data from the HJS 2.7 m telescope we determine a Keplerian orbital solution for this system with a period of 962 days, an eccentricity of e=0.76 and a velocity semi-amplitude K of 57.4 m/s. The planet has a minimum mass of m sin i = 1.82 +- 0.14 M_Jup and an orbital semi-major axis of a = 1.92 +-0.07 AU.

Michael Endl; William D. Cochran; Robert A. Wittenmyer; Artie P. Hatzes

2006-02-28

272

Pinhole cameras as sensors for atomic oxygen in orbit; application to attitude determination of the LDEF  

NASA Technical Reports Server (NTRS)

Images produced by pinhole cameras using film sensitive to atomic oxygen provide information on the ratio of spacecraft orbital velocity to the most probable thermal speed of oxygen atoms, provided the spacecraft orientation is maintained stable relative to the orbital direction. Alternatively, as it is described, information on the spacecraft attitude relative to the orbital velocity can be obtained, provided that corrections are properly made for thermal spreading and a co-rotating atmosphere. The LDEF orientation, uncorrected for a co-rotating atmosphere, was determined to be yawed 8.0 minus/plus 0.4 deg from its nominal attitude, with an estimated minus/plus 0.35 deg oscillation in yaw. The integrated effect of inclined orbit and co-rotating atmosphere produces an apparent oscillation in the observed yaw direction, suggesting that the LDEF attitude measurement will indicate even better stability when corrected for a co-rotating atmosphere. The measured thermal spreading is consistent with major exposure occurring during high solar activity, which occurred late during the LDEF mission.

Peters, Palmer N.; Gregory, John C.

1991-01-01

273

Direct determination of spin-orbit interaction coefficients and realization of the persistent spin helix symmetry.  

PubMed

The spin-orbit interaction plays a crucial role in diverse fields of condensed matter, including the investigation of Majorana fermions, topological insulators, quantum information and spintronics. In III-V zinc-blende semiconductor heterostructures, two types of spin-orbit interaction--Rashba and Dresselhaus--act on the electron spin as effective magnetic fields with different directions. They are characterized by coefficients ? and ?, respectively. When ? is equal to ?, the so-called persistent spin helix symmetry is realized. In this condition, invariance with respect to spin rotations is achieved even?in the presence of the spin-orbit interaction, implying strongly enhanced spin lifetimes for spatially periodic spin modes. Existing methods to evaluate ?/? require fitting analyses that often include ambiguity in the parameters used. Here, we experimentally demonstrate a simple and fitting parameter-free technique to determine ?/? and to deduce the absolute values of ? and ?. The method is based on the detection of the effective magnetic field direction and the strength induced by the two spin-orbit interactions. Moreover, we observe the persistent spin helix symmetry by gate tuning. PMID:25017310

Sasaki, A; Nonaka, S; Kunihashi, Y; Kohda, M; Bauernfeind, T; Dollinger, T; Richter, K; Nitta, J

2014-09-01

274

On simulation of precise orbit determination of HY-2 with centimeter precision based on satellite-borne GPS technique  

NASA Astrophysics Data System (ADS)

The HY-2 satellite carrying a satellite-borne GPS receiver is the first Chinese radar altimeter satellite, whose radial orbit determination precision must reach the centimeter level. Now HY-2 is in the test phase so that the observations are not openly released. In order to study the precise orbit determination precision and procedure for HY-2 based on the satellite-borne GPS technique, the satellite-borne GPS data are simulated in this paper. The HY-2 satellite-borne GPS antenna can receive at least seven GPS satellites each epoch, which can validate the GPS receiver and antenna design. What's more, the precise orbit determination processing flow is given and precise orbit determination experiments are conducted using the HY-2-borne GPS data with both the reduced-dynamic method and the kinematic geometry method. With the 1 and 3 mm phase data random errors, the radial orbit determination precision can achieve the centimeter level using these two methods and the kinematic orbit accuracy is slightly lower than that of the reduced-dynamic orbit. The earth gravity field model is an important factor which seriously affects the precise orbit determination of altimeter satellites. The reduced-dynamic orbit determination experiments are made with different earth gravity field models, such as EIGEN2, EGM96, TEG4, and GEMT3. Using a large number of high precision satellite-borne GPS data, the HY-2 precise orbit determination can reach the centimeter level with commonly used earth gravity field models up to above 50 degrees and orders.

Guo, Jin-Yun; Qin, Jian; Kong, Qiao-Li; Li, Guo-Wei

2012-03-01

275

Upper-atmosphere rotation rate determined from the orbit of CHINA 6 rocket \\/1976-87B  

Microsoft Academic Search

The orbit of CHINA 6 rocket, 1976-87B, has been determined at 51 epochs during its 17 month life, using the RAE orbit refinement computer program, PROP 6, with over 4000 radar and optical observations. The rotation rate of the upper atmosphere in lambda rev\\/day, for the height-band of 200-230 km, was calculated from the decrease in orbital inclination to give

H. Hiller

1980-01-01

276

Initiation stage of alkene metathesis: Insights from natural bond orbital and charge decomposition analyses  

NASA Astrophysics Data System (ADS)

The Rusbnd PR3 bonds of 1-2(a-b)-PC, Rudbnd CHPh bonds of 1a-b, 2-Inact/Act and 1a-b, 2-RCB were analyzed by charge decomposition (CDA) and natural bond orbital (NBO). We have found that the dissociation step of the Rusbnd PR3 bond is driven by charge transfer, while the RCB by polarization effects. Furthermore, the ?(Cipso)-?*(Rudbnd C) interaction was associated with delocalization effects in the benzylidene ring. Likewise, the nature of the rotameric changes in the carbene was studied through the resonance stabilization energy (ENLW). 2 presented a lower ?ENLW (Inactive ? Active) than 1a-b, which confirms that the delocalization effects are related to a low carbene rotameric energy.

Paredes-Gil, Katherine; Jaque, Pablo

2015-01-01

277

Desaturation Maneuvers and Precise Orbit Determination for the BepiColombo Mission  

E-print Network

The purpose of this work is the analysis of the consequences that desaturation maneuvers can have in the precise orbit determination corresponding to the Radio Science Experiment (MORE) of the BepiColombo mission to Mercury. This mission is an ESA/JAXA joint project with very challenging objectives regarding geodesy, geophysics and fundamental physics. In the neighborhood of Mercury, the s/c will experience strong solar radiation pressure torques; the s/c attitude is controlled by inertial wheels that after some time reach their maximum rotation state. Then they have to be slowed down by means of thruster pulses, inducing a residual acceleration on the s/c, with a desaturation (or off-loading) maneuver. In this paper, we will show how such maneuvers affect the orbit of the s/c and the radio science measurements and, also, how to include them in the orbit determination and parameter estimation procedure. The non linear least squares fit we consider is applied on a set of observational arcs separated by intervals of time where the probe is not visible. With the current baseline of two ground stations, two maneuvers are performed per day, one during the observing session, the other in the dark. To reach the scientific goals of the mission, they have to be treated as "solve for quantities". We have developed a specific methodology based on the deterministic propagation of the orbit, which is able to deal with these variables, by connecting subsequent observational arcs in a smooth way. The numerical simulations we will show demonstrate that this constrained multi-arc strategy is able to determine the maneuvers, including the ones in the dark, together with the other parameters of interest at a high level of accuracy. The future development consists in including accelerometer readings and calibrations in the method.

Elisa Maria Alessi; Stefano Cicalo'; Andrea Milani; Giacomo Tommei

2012-02-28

278

Orbit Determination for Comet C/2011 W3 (Lovejoy) Using a New Technique  

NASA Astrophysics Data System (ADS)

On Nov. 27, 2011, a bright, new member of the Kreutz system of sungrazing comets was discovered, designated C/2011 W3 (Lovejoy). During the 18 days remaining before perihelion, 116 ground-based astrometric observations were made, along with a several dozen from spacecraft observing the Sun. Unfortunately, pre-perihelion data alone was not sufficient for an accurate determination of the orbital period, and the spaceborne astrometric observations were not sufficiently accurate to help. Surprisingly, the comet survived perihelion, but it clearly underwent major changes: the nuclear condensation completely disappeared within days, and a narrow spine tail formed. Post-perihelion ground-based astrometry from Rob McNaught was referenced to the sunward tip of the spine tail, but it could not be used successfully in orbit solutions. We show that the spine tail was a synchronic feature which originated from the terminal disintegration of the nucleus, on Dec. 17.6 ± 0.2 UT (Sekanina & Chodas, submitted). In a new technique, we derive astrometric positions of the missing nucleus via two constraints: first, that it would lie on the extrapolated spine tail, and second, that it would lie on a line of orbital-period variation, obtained by forcing a range or orbital periods to sets of elements based on pre-perihelion astrometry. The resulting osculating orbital period is 698 ± 2 years, which shows that C/2011 W3 cannot be a fragment of any sungrazer observed since the 17th century, and must be a member of the expected new 21st-century cluster of bright Kreutz-system sungrazers, predicted by Sekanina & Chodas (2007).

Chodas, Paul; Sekanina, Z.

2012-10-01

279

An energy criterion for determining d orbital contribution to adsorbate bonding to a transition metal: CO\\/Fe 12  

Microsoft Academic Search

Summary A new criterion is presented for determining the contribution of a particular class or group of orbitals to a chemical bond. The new criterion is the diatomic energy contribution of particular orbitals to a bond. In neglect to differential overlap methods the total energy may be decomposed entirely into monoatomic and diatomic terms. The contribution of the electrons ind

George Blyholder; Michael Lawless

1990-01-01

280

Initial observations of the nightside ionosphere of venus from pioneer venus orbiter radio occultations.  

PubMed

Pioneer Venus orbiter dual-frequency radio occultation measurements have produced many electron density profiles of the nightside ionosphere of Venus. Thirty-six of these profiles, measured at solar zenith angles (chi) from 90.60 degrees to 163.5 degrees , are discussed here. In the "deep" nightside ionosphere (chi > 110 degrees ), the structure and magnitude of the ionization peak are highly variable; the mean peak electron density is 16,700 +/- 7,200 (standard deviation) per cubic centimeter. In contrast, the altitude of the peak remains fairly constant with a mean of 142.2 +/- 4.1 kilometers, virtually identical to the altitude of the main peak of the dayside terminator ionosphere. The variations in the peak ionization are not directly related to contemporal variations in the solar wind speed. It is shown that electron density distributions similar to those observed in both magnitude and structure can be produced by the precipitation on the nightside of Venus of electron fluxes of about 108 per square centimeter per second with energies less than 100 electron volts. This mechanism could very likely be responsible for the maintenance of the persistent nightside ionosphere of Venus, although transport processes may also be important. PMID:17778916

Kliore, A J; Patel, I R; Nagy, A F; Cravens, T E; Gombosi, T I

1979-07-01

281

Initial observations of the nightside ionosphere of Venus from Pioneer Venus Orbiter radio occultations  

NASA Technical Reports Server (NTRS)

Results of radio occultation measurements of electron density profiles of the nightside ionosphere of Venus at solar zenith angles from 90 to 164 deg, obtained from the Pioneer Venus Orbiter, are reported. Data were derived from closed-loop S- and X-band signals received by the Deep Space Network upon ionospheric entry and exit of the spacecraft. Nightside electron density profiles are found to be rather uniform in the solar zenith angle range of from 95 to 107 deg, with peak electron densities ranging from 23,000 to 40,000/cu cm, while between 110 and 164 deg, profiles exhibit a high degree of variability and peak electron densities vary from 7,600 to 31,800/cu cm. A possible mechanism for the maintenance of the nightside Venus ionosphere during the long Venus night, which is consistent with the observed spatial and temporal variability of deep ionospheric electron density profiles, is proposed to be impact ionization by precipitating particles, although transport processes from the dayside may also be important.

Kliore, A. J.; Patel, I. R.; Nagy, A. F.; Cravens, T. E.; Gombosi, T. I.

1979-01-01

282

An efficient initial guess formation of broken-symmetry solutions by using localized natural orbitals  

NASA Astrophysics Data System (ADS)

A novel procedure to generate initial broken-symmetry solutions is proposed. Conventional methods for the initial broken-symmetry solutions are the MO alter, HOMO-LUMO mixing and fragment methods. These procedures, however, are quite complex. Our new approach is efficient, automatic and highly practical especially for large QM systems. This approach, called the LNO method, is applied to the following four typical open-shell systems: H2, dicarbene and two iron-sulfur clusters of Rieske-type [2Fe-2S] and [4Fe-4S]. The performance and the efficiency as an electronic structural analysis are discussed. The LNO method will be applicable for general systems in the complicated broken symmetry states.

Shoji, Mitsuo; Yoshioka, Yasunori; Yamaguchi, Kizashi

2014-07-01

283

11 CFR 9033.10 - Procedures for initial and final determinations.  

Code of Federal Regulations, 2010 CFR

...Commission's determination and will summarize the results of any investigation upon which the determination is based. (d) Effect on other determinations. If the Commission makes an initial determination under this section, but decides to...

2010-01-01

284

78 FR 44971 - Certain Robotic Toys and Components Thereof; Commission Determination Not To Review an Initial...  

Federal Register 2010, 2011, 2012, 2013

...INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-869] Certain Robotic Toys and Components Thereof; Commission Determination Not To Review an Initial Determination Granting a Joint Motion for...

2013-07-25

285

Ground testing on the nonvented fill method of orbital propellant transfer: Results of initial test series  

NASA Technical Reports Server (NTRS)

The results are presented of a series of no-vent fill experiments conducted on a 175 cu ft flightweight hydrogen tank. The experiments consisted of the nonvented fill of the tankage with liquid hydrogen using two different inlet systems (top spray, and bottom spray) at different tank initial conditions and inflow rates. Nine tests were completed of which six filled in excess of 94 percent. The experiments demonstrated a consistent and repeatable ability to fill the tank in excess of 94 percent using the nonvented fill technique. Ninety-four percent was established as the high level cutoff due to requirements for some tank ullage to prevent rapid tank pressure rise which occurs in a tank filled entirely with liquid. The best fill was terminated at 94 percent full with a tank internal pressure less than 26 psia. Although the baseline initial tank wall temperature criteria was that all portions of the tank wall be less than 40 R, fills were achieved with initial wall temperatures as high as 227 R.

Chato, David J.

1991-01-01

286

A new method of intermediate orbit determination based on range and range rate measurements at three times. (Russian Title: ????? ????? ??????????? ????????????? ?????? ?? ?????????? ????????? ? ???????? ?? ????????? ? ??? ??????? ???????)  

NASA Astrophysics Data System (ADS)

A new method is proposed for computing the preliminary orbit of a small celestial body from three pairs of range and range rate observations. The method is based on using the superosculating intermediate orbit with a fourth-order tangency that we previously constructed. This intermediate orbit allows for most of the perturbations in the motion of the body under study. The methodical error of orbit determination by the proposed method is three orders smaller than the corresponding error of the commonly used approach based on the construction of the unperturbed Keplerian orbit. Using the examples of finding the orbits of artificial Earth satellites, the results obtained by the procedure implementing the traditional approach and the new method are compared. The comparison shows that the new method is a highly efficient means for studying perturbed motion.

Shefer, V. A.

2013-12-01

287

Abstract In previous studies of saccadic eye movement reaction time, the manipulation of initial eye position re-vealed a behavioral bias that facilitates the initiation of movements towards the central orbital position. An inter-esting  

E-print Network

Abstract In previous studies of saccadic eye movement reaction time, the manipulation of initial eye position re-vealed a behavioral bias that facilitates the initiation of movements towards of positions that the eyes can take in the orbits delimits the extent of visual exploration by head

Munoz, Douglas Perry

288

20 CFR 410.621 - Effect of initial determination.  

Code of Federal Regulations, 2010 CFR

... Employees' Benefits SOCIAL SECURITY ADMINISTRATION FEDERAL COAL MINE HEALTH AND SAFETY ACT OF 1969, TITLE IV-BLACK LUNG BENEFITS (1969- ) Determinations of Disability, Other Determinations, Administrative Review, Finality of Decisions,...

2010-04-01

289

Orbit determination error analysis for an interior libration point orbit in the Sun-Earth+Moon elliptic restricted three-body problem  

NASA Astrophysics Data System (ADS)

A spacecraft in a libration point orbit between the Earth and the Sun can be useful to study the interaction of the Sun's corona with the terrestrial environment. However, the spacecraft in such an orbit will drift from the nominal (unstable) path, and the forces individually have some level of uncertainty. Both range and range-rate tracking also include some inaccuracy in the data obtained. The accumulated error in the spacecraft's position and velocity relative to the nominal path after a predetermined period of tracking can be measured. This error, or uncertainty, in the spacecraft state is measured through simulations commonly referred to as orbit determination error analysis. The specific error analysis method used here is covariance analysis; the covariance matrix, after a predetermined period of tracking along the nominal path, contains the state uncertainties (state vector element variances) along its diagonal.

Gordon, Steven C.

1991-09-01

290

Single Step to Orbit; a First Step in a Cooperative Space Exploration Initiative  

NASA Technical Reports Server (NTRS)

At the end of the Cold War, disarmament planners included a recommendation to ease reduction of the U.S. and Russian aerospace industries by creating cooperative scientific pursuits. The idea was not new, having earlier been suggested by Eisenhower and Khrushchev to reduce the pressure of the "Military Industrial Complex" by undertaking joint space exploration. The Space Exploration Initiative (SEI) proposed at the end of the Cold War by President Bush and Premier Gorbachev was another attempt to ease the disarmament process by giving the bloated war industries something better to do. The engineering talent and the space rockets could be used for peaceful pursuits, notably for going back to the Moon and then on to Mars with human exploration and settlement. At the beginning of this process in 1992 staff of the Stanford Center for International Cooperation in Space attended the International Space University in Canada, met with Russian participants and invited a Russian team to work with us on a joint Stanford-Russian Mars Exploration Study. A CIA student and Airforce and Navy students just happened to join the Stanford course the next year and all students were aware that the leader of the four Russian engineers was well versed in Russian security. But, as long as they did their homework, they were welcome to participate with other students in defining the Mars mission and the three engineers they sent were excellent. At the end of this study we were invited to give a briefing to Dr. Edward Teller at Stanford's Hoover Institution of War and Peace. We were also encouraged to hold a press conference on Capitol Hill to introduce the study to the world. At a pre-conference briefing at the Space Council, we were asked to please remind the press that President Bush had asked for a cooperative exploration proposal not a U.S. alone initiative. The Stanford-Russian study used Russia's Energia launchers, priced at $300 Million each. The mission totaled out to $71.5 Billion, to send a six-person crew to establish a Mars base and return. It was an on going international venture with plans for new crews, base expansion, and extended exploration at every two year opportunity. The $71.5 Billion international approach contrasted with NASA's own 90-day U.S. - alone study that proposed a package topping $500 Billion by some admissions. NASA's approach was also challenged by an internal D.O.E. proposal at much lower cost, described to the Mars Society last year by Lowell Wood and, of course, by Bob Zubrin's "Mars Direct" proposal.

Lusignan, Bruce; Sivalingam, Shivan

1999-01-01

291

Orbit Determination and Gravity Field Estimation of the Dawn spacecraft at Vesta Using Radiometric and Image Constraints with GEODYN Software  

NASA Astrophysics Data System (ADS)

The Dawn spacecraft orbited the protoplanet Vesta from May 3, 2011 to July 25, 2012. Precise orbit determination was critical for the geophysical investigation, as well as the definition of the Vesta-fixed reference frame and the subsequent registration of datasets to the surface. GEODYN, the orbit determination and geodetic parameter estimation software of NASA Goddard Spaceflight Center, was used to compute the orbit of the Dawn spacecraft and estimate the gravity field of Vesta. GEODYN utilizes radiometric Doppler and range measurements, and was modified to process image data from Dawn's cameras. X-band radiometric measurements were acquired by the NASA Deep Space Network (DSN). The addition of the capability to process image constraints decreases position uncertainty in the along- and cross-orbit track directions because of their geometric strengths compared with radiometric measurements. This capability becomes critical for planetary missions such as Dawn due to the weak gravity environment, where non-conservative forces affect the orbit more than typical of orbits at larger planetary bodies. Radiometric measurements were fit to less than 0.1 mm/s and 5 m for Doppler and range during the Survey orbit phase (compared with measurement noise RMS of about 0.05 mm/s and 2 m for Doppler and range). Image constraint RMS was fit to less than 100 m (resolution is 5 - 150 m/pixel, depending on the spacecraft altitude). Orbits computed using GEODYN were used to estimate a 20th degree and order gravity field of Vesta. The quality of the orbit determination and estimated gravity field with and without image constraints was assessed through comparison with the spacecraft trajectory and gravity model provided by the Dawn Science Team.

Centinello, F. J.; Zuber, M. T.; Mazarico, E.

2013-12-01

292

PSA: A program to streamline orbit determination for launch support operations  

NASA Technical Reports Server (NTRS)

An interactive, menu driven computer program was written to streamline the orbit determination process during the critical launch support phase of a mission. Residing on a virtual memory minicomputer, this program retains the quantities in-core needed to obtain a least squares estimate of the spacecraft trajectory with interactive displays to assist in rapid radio metric data evaluation. Menu-driven displays allow real time filter and data strategy development. Graphical and tabular displays can be sent to a laser printer for analysis without exiting the program. Products generated by this program feed back to the main orbit determination program in order to further refine the estimate of the trajectory. The final estimate provides a spacecraft ephemeris which is transmitted to the mission control center and used for antenna pointing and frequency predict generation by the Deep Space Network. The development and implementation process of this program differs from that used for most other navigation software by allowing the users to check important operating features during development and have changes made as needed.

Legerton, V. N.; Mottinger, N. A.

1988-01-01

293

Galileo precise orbit and clocks determination at the CNES-CLS IGS Analysis Center  

NASA Astrophysics Data System (ADS)

Thanks to the IGS (International GNSS Service) Multi-GNSS Experiment (M-GEX), signals from new GNSS satellites like Galileo are now available. CNES and IGN joined their efforts to contribute with others international agency to the densification of this multi-GNSS global network through the REGINA project. Since mid-2012 we process the data from the global M-GEX tracking network (~50 stations) to determine precise orbit of the Galileo satellites. The strategy followed at the CNES-CLS IGS Analysis Center uses a combined computation of GPS (E1/E2) and GALILEO (E1/E5a) data. This strategy allows the continuous determination of receiver clocks and the recovering of pseudo-range and phase biases between receivers and between GPS and Galileo observations. In parallel with orbit and clocks solutions we provide a daily monitoring of the network receivers coordinates. The quality of our products is accessed through their comparison with the other agencies participating to the M-GEX project as well as PPP (Precise Point Positioning) tests.

Loyer, S.; Mercier, F.; Capdeville, H.; Andrianavonimiarina, J.; Mezerette, A.; Perosanz, F.; Boulanger, C.; Lestarquit, L.

2013-12-01

294

Ab Initio determination of Cu 3d orbital energies in layered copper oxides  

PubMed Central

It has long been argued that the minimal model to describe the low-energy physics of the high Tc superconducting cuprates must include copper states of other symmetries besides the canonical one, in particular the orbital. Experimental and theoretical estimates of the energy splitting of these states vary widely. With a novel ab initio quantum chemical computational scheme we determine these energies for a range of copper-oxides and -oxychlorides, determine trends with the apical Cu–ligand distances and find excellent agreement with recent Resonant Inelastic X-ray Scattering measurements, available for La2CuO4, Sr2CuO2Cl2, and CaCuO2. PMID:22355584

Hozoi, Liviu; Siurakshina, Liudmila; Fulde, Peter; van den Brink, Jeroen

2011-01-01

295

Validity of repeated initial rise thermoluminescence kinetic parameter determinations  

SciTech Connect

The validity of thermoluminescence (TL) analysis by repeated initial rise measurements has been studied by computer simulation. Thermoluminescence described by 1st Order, 2nd Order, General One Trap and Interactive TL Kinetics was investigated. In the simulation each of the repeated temperature increase and decrease cycles contains a linear temperature increase followed by a decrease appropriate for radiative cooling, i.e. the latter is approximated by a decreasing exponential. The activation energies computed from the simulated emission are readily compared with those used to compute the TL emission. In all cases studied, the repeated initial rise technique provides reliable results only for single peak glow curves or for glow curves containing peaks that do not overlap and, if sufficiently separated, the lowest temperature peak in multipeak curves. Also the temperatures, or temperature cycles corresponding to correct activation energies occur on the low temperature side of the normal glow curve, often well below the peak temperature. A variety of misleading and/or incorrect results an be obtained when the repeated initial rise technique is applied to TL systems that produce overlapping peaks in the usual glow curve. 6 refs., 10 figs.

Kierstead, J.A.; Levy, P.W.

1990-01-01

296

A method of high-accuracy orbit determination from three observations of a small celestial body. (Russian Title: ????? ????????????? ??????????? ?????? ?? ???? ??????????? ?????? ????????? ????)  

NASA Astrophysics Data System (ADS)

A new method is suggested for finding the preliminary orbit of a small celestial body from its three pairs of angular measurements at three times. The method uses the intermediate orbit that we previously constructed from three position vectors and the corresponding times. This intermediate orbit allows for most of the perturbations in the motion of the body under study. The methodical error of orbit computation by the proposed method is generally three orders smaller than the corresponding error of the traditional approach based on the construction of the unperturbed Keplerian orbit. This fact allows such a reference arc to be selected that the accuracy of the intermediate orbit would always match that of the reference observations that determine this arc. The new method is a highly efficient tool, which allows reliable parameters of the perturbed motion to be obtained already at the stage of computing the preliminary orbit. It is especially efficient if applied to high-accuracy observational data covering short orbital arcs.

Shefer, V. A.

2009-11-01

297

Investigations to Determine the Origin of the Solar Wind with the SPICE EUV Imaging Spectrograph and the Solar Orbiter Mission  

NASA Astrophysics Data System (ADS)

At large spatial scales, the structure of the solar wind and it's mapping back to the solar corona, is thought to be reasonably well understood. However, the detailed structure of the various source regions at chromospheric and transition region heights is extremely complex, and less well understood. Determining this connection between heliospheric structures and their source regions at the Sun is one of the overarching objective of the Solar Orbiter mission. During perihelion segments of its orbit, when the spacecraft is in quasi-corotation with the Sun, Solar Orbiter will determine the plasma parameters and compositional signatures of the solar wind, which can be compared directly with the spectroscopic signatures of coronal ions with differing charge-to-mass ratios and FIP. One of the key instruments on the Solar Orbiter mission to make these remote sensing measurements is the SPICE (Spectral Imaging of the Coronal Environment) imaging spectrograph. SPICE will provide the images and plasma diagnostics needed to characterize the plasma state in different source regions, from active regions to quiet Sun to coronal holes. By comparing composition, plasma parameters, and low/high FIP ratios of structures remotely, with those measured directly at the Solar Orbiter spacecraft, Solar Orbiter will provide the first direct link between solar wind structures and their source regions at the Sun. This talk will provide a background of previous compositional correlation measurements and an outline of the method to be used for comparing the spectroscopic and in-situ plasma parameters to be measured with Solar Orbiter.

Hassler, D. M.; Deforest, C.; Spice Team

2011-12-01

298

Discovery of 13.5 s X-ray pulsations from LMC X-4 and an orbital determination  

NASA Technical Reports Server (NTRS)

X-ray pulsations with a 13.5-sec period have been detected from the 1.4-d X-ray binary LMC X-4. By measuring the apparent pulse period at several binary orbital phases, and assuming the orbit to be nearly circular, the semimajor axis of the orbit is determined to be 30 + or - 5 ly-sec. This result, together with a revised orbital velocity amplitude of 37.9 + or - 2.4 km/sec, and other available information, suffice for the determination of the component masses of the binary system and the radius of the companion star. The mass of the neutron star is found to be 1.6 +1.0 -0.5 solar masses, while the mass, radius, and effective temperature of the companion star indicate that it may be undermassive for its luminosity.

Kelley, R. L.; Jernigan, J. G.; Levine, A.; Petro, L. D.; Rappaport, S.

1983-01-01

299

On the Determination of Poisson Statistics for Haystack Radar Observations of Orbital Debris  

NASA Technical Reports Server (NTRS)

A convenient and powerful method is used to determine if radar detections of orbital debris are observed according to Poisson statistics. This is done by analyzing the time interval between detection events. For Poisson statistics, the probability distribution of the time interval between events is shown to be an exponential distribution. This distribution is a special case of the Erlang distribution that is used in estimating traffic loads on telecommunication networks. Poisson statistics form the basis of many orbital debris models but the statistical basis of these models has not been clearly demonstrated empirically until now. Interestingly, during the fiscal year 2003 observations with the Haystack radar in a fixed staring mode, there are no statistically significant deviations observed from that expected with Poisson statistics, either independent or dependent of altitude or inclination. One would potentially expect some significant clustering of events in time as a result of satellite breakups, but the presence of Poisson statistics indicates that such debris disperse rapidly with respect to Haystack's very narrow radar beam. An exception to Poisson statistics is observed in the months following the intentional breakup of the Fengyun satellite in January 2007.

Stokely, Christopher L.; Benbrook, James R.; Horstman, Matt

2007-01-01

300

Determinants of initiation and progression of idiopathic pulmonary fibrosis  

PubMed Central

IPF is a devastating disease with few therapeutic options. The precise aetiology of IPF remains elusive. However, our understanding of the pathologic processes involved in the initiation and progression of this disease is improving. Data on the mechanisms underlying IPF have been generated from epidemiologic investigations as well as cellular and molecular studies of human tissues. Although no perfect animal model of human IPF exists, pre-clinical animal studies have helped define pathways which are likely important in human disease. Epithelial injury, fibroblast activation and repetitive cycles of injury and abnormal repair are almost certainly key events. Factors which have been associated with initiation and/or progression of IPF include viral infections, abnormal cytokine, chemokine and growth factor production, oxidant stress, autoimmunity, inhalational of toxicants and gastro-oesophageal reflux disease. Furthermore, recent evidence identifies a role for a variety of genetic and epigenetic abnormalities ranging from mutations in surfactant protein C to abnormalities in telomere length and telomerase activity. The challenge remains to identify additional inciting agents and key dysregulated pathways that lead to disease progression so that we can develop targeted therapies to treat or prevent this serious disease. PMID:19740254

Kottmann, Robert Matthew; Hogan, Christopher M.; Phipps, Richard P.; Sime, Patricia J.

2013-01-01

301

Ledge X-ray absorption spectroscopy of non-heme iron sites: experimental determination of differential orbital covalency  

Microsoft Academic Search

X-ray absorption spectroscopy has been utilized to obtain the L-edge multiplet spectra for a series of non-heme ferric and ferrous complexes. Using these data, a methodology for determining the total covalency and the differential orbital covalency (DOC), that is, differences in covalency in the different symmetry sets of the d orbitals, has been developed. The integrated L-edge intensity is proportional

Erik C. Wasinger; Frank M. F. de Groot; Britt Hedman; Keith O. Hodgson; Edward I. Solomon

2003-01-01

302

Calculating role similarities: An algorithm that helps determine the orbits of a graph  

Microsoft Academic Search

The orbits or a graph, digraph or network provide an effective definition for role equivalence since they are a natural generalization of the principle of substitutability of structural equivalence. Calculation of the orbits is a computationally difficult task but in this paper we present a fast and efficient algorithm which finds the orbits of a large class of graphs. In

Martin G. Everett; Steve Borgatti

1988-01-01

303

45 CFR 212.4 - Reception; initial determination, provisions of temporary assistance.  

Code of Federal Regulations, 2013 CFR

...initial determination, provisions of temporary assistance. 212.4 Section 212.4 Public Welfare Regulations Relating to Public Welfare OFFICE OF FAMILY ASSISTANCE (ASSISTANCE PROGRAMS), ADMINISTRATION...

2013-10-01

304

45 CFR 212.4 - Reception; initial determination, provisions of temporary assistance.  

Code of Federal Regulations, 2012 CFR

...initial determination, provisions of temporary assistance. 212.4 Section 212.4 Public Welfare Regulations Relating to Public Welfare OFFICE OF FAMILY ASSISTANCE (ASSISTANCE PROGRAMS), ADMINISTRATION...

2012-10-01

305

45 CFR 212.4 - Reception; initial determination, provisions of temporary assistance.  

Code of Federal Regulations, 2010 CFR

...initial determination, provisions of temporary assistance. 212.4 Section 212.4 Public Welfare Regulations Relating to Public Welfare OFFICE OF FAMILY ASSISTANCE (ASSISTANCE PROGRAMS), ADMINISTRATION...

2010-10-01

306

45 CFR 212.4 - Reception; initial determination, provisions of temporary assistance.  

Code of Federal Regulations, 2011 CFR

...initial determination, provisions of temporary assistance. 212.4 Section 212.4 Public Welfare Regulations Relating to Public Welfare OFFICE OF FAMILY ASSISTANCE (ASSISTANCE PROGRAMS), ADMINISTRATION...

2011-10-01

307

45 CFR 212.4 - Reception; initial determination, provisions of temporary assistance.  

...initial determination, provisions of temporary assistance. 212.4 Section 212.4 Public Welfare Regulations Relating to Public Welfare OFFICE OF FAMILY ASSISTANCE (ASSISTANCE PROGRAMS), ADMINISTRATION...

2014-10-01

308

Enhanced orbit determination filter: Inclusion of ground system errors as filter parameters  

NASA Technical Reports Server (NTRS)

The theoretical aspects of an orbit determination filter that incorporates ground-system error sources as model parameters for use in interplanetary navigation are presented in this article. This filter, which is derived from sequential filtering theory, allows a systematic treatment of errors in calibrations of transmission media, station locations, and earth orientation models associated with ground-based radio metric data, in addition to the modeling of the spacecraft dynamics. The discussion includes a mathematical description of the filter and an analytical comparison of its characteristics with more traditional filtering techniques used in this application. The analysis in this article shows that this filter has the potential to generate navigation products of substantially greater accuracy than more traditional filtering procedures.

Masters, W. C.; Scheeres, D. J.; Thurman, S. W.

1994-01-01

309

A numerical comparison of discrete Kalman filtering algorithms: An orbit determination case study  

NASA Technical Reports Server (NTRS)

The numerical stability and accuracy of various Kalman filter algorithms are thoroughly studied. Numerical results and conclusions are based on a realistic planetary approach orbit determination study. The case study results of this report highlight the numerical instability of the conventional and stabilized Kalman algorithms. Numerical errors associated with these algorithms can be so large as to obscure important mismodeling effects and thus give misleading estimates of filter accuracy. The positive result of this study is that the Bierman-Thornton U-D covariance factorization algorithm is computationally efficient, with CPU costs that differ negligibly from the conventional Kalman costs. In addition, accuracy of the U-D filter using single-precision arithmetic consistently matches the double-precision reference results. Numerical stability of the U-D filter is further demonstrated by its insensitivity of variations in the a priori statistics.

Thornton, C. L.; Bierman, G. J.

1976-01-01

310

Determination of orbits and SLR stations’ coordinates on the basis of laser observations of the satellites Starlette and Stella  

Microsoft Academic Search

Orbits of two low satellites Starlette and Stella have been determined on the basis of the observational data collected in 2001 from the best 14 Satellite Laser Ranging stations. The coordinates of seven SLR stations have been determined in the ITRF2000 coordinates frame and compared with the results calculated for the same stations on the basis of Lageos data. All

P. Lejba; S. Schillak; E. Wnuk

2007-01-01

311

Towards the GEOSAT Follow-On Precise Orbit Determination Goals of High Accuracy and Near-Real-Time Processing  

NASA Technical Reports Server (NTRS)

The US Navy's GEOSAT Follow-On spacecraft (GFO) primary mission objective is to map the oceans using a radar altimeter. Satellite laser ranging data, especially in combination with altimeter crossover data, offer the only means of determining high-quality precise orbits. Two tuned gravity models, PGS7727 and PGS7777b, were created at NASA GSFC for GFO that reduce the predicted radial orbit through degree 70 to 13.7 and 10.0 mm. A macromodel was developed to model the nonconservative forces and the SLR spacecraft measurement offset was adjusted to remove a mean bias. Using these improved models, satellite-ranging data, altimeter crossover data, and Doppler data are used to compute both daily medium precision orbits with a latency of less than 24 hours. Final precise orbits are also computed using these tracking data and exported with a latency of three to four weeks to NOAA for use on the GFO Geophysical Data Records (GDR s). The estimated orbit precision of the daily orbits is between 10 and 20 cm, whereas the precise orbits have a precision of 5 cm.

Lemoine, Frank G.; Zelensky, Nikita P.; Chinn, Douglas S.; Beckley, Brian D.; Lillibridge, John L.

2006-01-01

312

20 CFR 408.1006 - What is the effect of an initial determination?  

Code of Federal Regulations, 2010 CFR

...determination? 408.1006 Section 408.1006 Employees' Benefits SOCIAL SECURITY ADMINISTRATION SPECIAL BENEFITS FOR CERTAIN WORLD WAR II VETERANS Determinations and the Administrative Review Process Introduction, Definitions, and Initial...

2010-04-01

313

20 CFR 408.1003 - Which administrative actions are initial determinations?  

Code of Federal Regulations, 2012 CFR

...determinations? 408.1003 Section 408.1003 Employees' Benefits SOCIAL SECURITY ADMINISTRATION SPECIAL BENEFITS FOR CERTAIN WORLD WAR II VETERANS Determinations and the Administrative Review Process Introduction, Definitions, and Initial...

2012-04-01

314

20 CFR 408.1005 - Will we mail you a notice of the initial determination?  

Code of Federal Regulations, 2013 CFR

...determination? 408.1005 Section 408.1005 Employees' Benefits SOCIAL SECURITY ADMINISTRATION SPECIAL BENEFITS FOR CERTAIN WORLD WAR II VETERANS Determinations and the Administrative Review Process Introduction, Definitions, and Initial...

2013-04-01

315

20 CFR 408.1006 - What is the effect of an initial determination?  

Code of Federal Regulations, 2011 CFR

...determination? 408.1006 Section 408.1006 Employees' Benefits SOCIAL SECURITY ADMINISTRATION SPECIAL BENEFITS FOR CERTAIN WORLD WAR II VETERANS Determinations and the Administrative Review Process Introduction, Definitions, and Initial...

2011-04-01

316

20 CFR 408.1003 - Which administrative actions are initial determinations?  

Code of Federal Regulations, 2011 CFR

...determinations? 408.1003 Section 408.1003 Employees' Benefits SOCIAL SECURITY ADMINISTRATION SPECIAL BENEFITS FOR CERTAIN WORLD WAR II VETERANS Determinations and the Administrative Review Process Introduction, Definitions, and Initial...

2011-04-01

317

Influence of radiant energy exchange on the determination of convective heat transfer rates to Orbiter leeside surfaces during entry  

NASA Technical Reports Server (NTRS)

Temperatures measured at the aerodynamic surface of the Orbiter's thermal protection system (TPS), and calorimeter measurements, are used to determine heating rates to the TPS surface during atmospheric entry. On the Orbiter leeside, where convective heating rates are low, it is possible that a significant portion of the total energy input may result from solar radiation, and for the wing, cross radiation from the hot (relatively) Orbiter fuselage. In order to account for the potential impact of these sources, values of solar- and cross-radiation heat transfer are computed, based upon vehicle trajectory and attitude information and measured surface temperatures. Leeside heat-transfer data from the STS-2 mission are presented, and the significance of solar radiation and fuselage-to-wing cross-radiation contributions to total energy input to Orbiter leeside surfaces is assessed.

Throckmorton, D. A.

1982-01-01

318

A computerized survey of a selected subset of initial orbit determination methods  

E-print Network

1 3 2 5 (7up ? 3upq ? up)dt + 8 o o 0 0 0 0 0 i (121) and 1 3 1 4 g = bt. ? ? u 4t. + ? u p 4t. + i 6 o i 4 o o i 1 (9uq -45up +u)dt + 2 2 5 0 0 0 0 0 (122) 29 and where u 0 3 r 0 (123) r ~ r po = r (124 ) 2 2 v -ru 0 qo 2 r (125... 0 0 0 5 3 2 4 + ? (7 up ? 3upq -up)bt 8 onooooo 1 1 2 2 3 2 4 + (630upq ? 24 uq -u ? 45 uq ? 945 p 120 o 0 o 0 0 0 0 0 o + 210 u p )btl + . 2 2 5 0 0 (132) and = 1 ? ? u bt + u p bt + ? (9 u q, ? 45 u p + u )bt 1 2 3 5 2 2 4 1 2 o 1 oo 1 120 o'o...

Cleveland, Durand Ennis

2012-06-07

319

Determination of the orbital lineup at reactive organic semiconductor interfaces using photoemission spectroscopy  

SciTech Connect

We determined the orbital lineup of the tris (8-hydroxyquinolinato) gallium (Gaq{sub 3})/Mg interface using combined x-ray and ultraviolet photoemission spectroscopy (XPS and UPS) measurements. The Gaq{sub 3}/Mg system is a prototypical model structure for organic electron/low work function electrode transporting materials interfaces found in organic light emitting diodes (OLED). A Gaq{sub 3} thin film was grown in 15 steps on a previously sputter-cleaned Mg substrate starting at a 1 Aa nominal thickness up to a final thickness of 512 Aa. Before, and in between the growth steps, the sample surface was characterized by XPS and UPS. The results indicate the formation of a reaction layer of about 12 Aa thickness at the Mg interface, which resulted in a 0.96 V interface dipole potential. At Gaq{sub 3} coverages higher than 256 Aa, a strong charging shift occurred in the overlayer related UPS-emission lines, which was identified by measuring the high binding energy cutoff (secondary edge) of both the XP and UP spectra. The several magnitudes different x-ray and ultraviolet source photon intensities allow pinpointing charging shifts with high sensitivity. Due to the low work function of the reacted interface layer, the Gaq{sub 3} electronic states are aligned at a binding energy below the substrate Fermi edge that exceeds the magnitude of the optical gap between the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO). This allowed the conclusion that the ground state exciton binding energy of Gaq{sub 3} needs to be larger than 0.43 eV. Based on these considerations, the lowest possible electron injection barrier matching the experimental data was estimated to be 0.15 eV. {copyright} 2001 American Institute of Physics.

Schlaf, R.; Merritt, C. D.; Picciolo, L. C.; Kafafi, Z. H.

2001-08-15

320

A review of averaging techniques and their application to orbit determination systems  

NASA Technical Reports Server (NTRS)

The theory of numerical averaging and analytical averaging will be reviewed and the application of these techniques to orbit and parameter estimation problems will be presented. Comparisons will be made between utilizing mean elements versus tracking data as the observation types. Results will be presented comparing the accuracy and efficiency of the combined orbit estimation and orbit prediction problem using averaged equations of motion, the Cowell equations of motion and the Brouwer general perturbation theory. The problem of converting the averaged element space back to osculating element space for orbit operations will also be discussed.

Velez, C. E.; Fuchs, A. J.

1974-01-01

321

Determination of orbits and SLR stations’ coordinates on the basis of laser observations of the satellites Starlette and Stella  

NASA Astrophysics Data System (ADS)

Orbits of two low satellites Starlette and Stella have been determined on the basis of the observational data collected in 2001 from the best 14 Satellite Laser Ranging stations. The coordinates of seven SLR stations have been determined in the ITRF2000 coordinates frame and compared with the results calculated for the same stations on the basis of Lageos data. All the calculations have been made assuming two models of the Earth gravity field EGM96 and EIGEN-GRACE02S. It has been shown that the best results of satellite orbits determination are obtained with the latest model of the Earth gravity field proposed on the basis of the GRACE mission results. With respect to the results obtained assuming the EGM96 model, the improvement reaches 10-50% both in the values of orbital RMS, and the station coordinates. All the calculations have been performed with the use of GEODYN-II program. The RMS of the orbits of Starlette and Stella varies from 1.02 to 1.90 cm. Such RMS values permit determination of the laser stations to a high accuracy. The results presented in this work show that the data obtained for low satellites such as Starlette or Stella can be successfully applied for determination of the SLR station coordinates.

Lejba, P.; Schillak, S.; Wnuk, E.

322

Ionospheric refraction effects on TOPEX orbit determination accuracy using the Tracking and Data Relay Satellite System (TDRSS)  

NASA Technical Reports Server (NTRS)

This investigation concerns the effects on Ocean Topography Experiment (TOPEX) spacecraft operational orbit determination of ionospheric refraction error affecting tracking measurements from the Tracking and Data Relay Satellite System (TDRSS). Although tracking error from this source is mitigated by the high frequencies (K-band) used for the space-to-ground links and by the high altitudes for the space-to-space links, these effects are of concern for the relatively high-altitude (1334 kilometers) TOPEX mission. This concern is due to the accuracy required for operational orbit-determination by the Goddard Space Flight Center (GSFC) and to the expectation that solar activity will still be relatively high at TOPEX launch in mid-1992. The ionospheric refraction error on S-band space-to-space links was calculated by a prototype observation-correction algorithm using the Bent model of ionosphere electron densities implemented in the context of the Goddard Trajectory Determination System (GTDS). Orbit determination error was evaluated by comparing parallel TOPEX orbit solutions, applying and omitting the correction, using the same simulated TDRSS tracking observations. The tracking scenarios simulated those planned for the observation phase of the TOPEX mission, with a preponderance of one-way return-link Doppler measurements. The results of the analysis showed most TOPEX operational accuracy requirements to be little affected by space-to-space ionospheric error. The determination of along-track velocity changes after ground-track adjustment maneuvers, however, is significantly affected when compared with the stringent 0.1-millimeter-per-second accuracy requirements, assuming uncoupled premaneuver and postmaneuver orbit determination. Space-to-space ionospheric refraction on the 24-hour postmaneuver arc alone causes 0.2 millimeter-per-second errors in along-track delta-v determination using uncoupled solutions. Coupling the premaneuver and postmaneuver solutions, however, appears likely to reduce this figure substantially. Plans and recommendations for response to these findings are presented.

Radomski, M. S.; Doll, C. E.

1991-01-01

323

Precise Orbit Determination for GEOSAT Follow-On Using Satellite Laser Ranging Data and Intermission Altimeter Crossovers  

NASA Technical Reports Server (NTRS)

The US Navy's GEOSAT Follow-On Spacecraft was launched on February 10, 1998 with the primary objective of the mission to map the oceans using a radar altimeter. Following an extensive set of calibration campaigns in 1999 and 2000, the US Navy formally accepted delivery of the satellite on November 29, 2000. Satellite laser ranging (SLR) and Doppler (Tranet-style) beacons track the spacecraft. Although limited amounts of GPS data were obtained, the primary mode of tracking remains satellite laser ranging. The GFO altimeter measurements are highly precise, with orbit error the largest component in the error budget. We have tuned the non-conservative force model for GFO and the gravity model using SLR, Doppler and altimeter crossover data sampled over one year. Gravity covariance projections to 70x70 show the radial orbit error on GEOSAT was reduced from 2.6 cm in EGM96 to 1.3 cm with the addition of SLR, GFO/GFO and TOPEX/GFO crossover data. Evaluation of the gravity fields using SLR and crossover data support the covariance projections and also show a dramatic reduction in geographically-correlated error for the tuned fields. In this paper, we report on progress in orbit determination for GFO using GFO/GFO and TOPEX/GFO altimeter crossovers. We will discuss improvements in satellite force modeling and orbit determination strategy, which allows reduction in GFO radial orbit error from 10-15 cm to better than 5 cm.

Lemoine, Frank G.; Rowlands, David D.; Luthcke, Scott B.; Zelensky, Nikita P.; Chinn, Douglas S.; Pavlis, Despina E.; Marr, Gregory

2001-01-01

324

Ephemeris calculation and orbit determination of geostationary satellites, using Taylor series integration  

NASA Astrophysics Data System (ADS)

It is shown that Taylor series integration allows problems of celestial mechanics for interplanetary orbits to be solved with relatively simple orbit models. The method is adapted to the computation of satellite orbits. A new implementation concept is included, which allows a programmation of the equations of motion. It offers simultaneously extension possibilities, which are necessary for the computation of special terms of the power function. The linking of Sun and Moon ephemeris for the treatment of gavitational disturbances of the satellite orbit is used as an example. This concept is represented with the principles of Taylor series integration, and compared with variants of the process. The power spectrum of the method is examined for disturbed and undisturbed Kepler orbits.

Montenbruck, Oliver

1991-02-01

325

Applicable Tracking Data Arcs for NORAD TLE Orbit Determination of the KOMPSAT-1 Satellite Using GPS Navigation Solutions  

Microsoft Academic Search

NORAD Two Line Element (TLE) is very useful to simplify the ground station antenna pointing and mission operations. When a satellite operations facility has the capability to determine NORAD type TLE which is independent of NORAD, it is important to analyze the applicable tracking data arcs for obtaining the best possible orbit. The applicable tracking data arcs for NORAD independent

Byoung-Sun Lee

2005-01-01

326

Reduced dynamic orbit determination using GPS code and carrier measurements Reduziert-dynamische Bahnbestimmung mit GPS Code und Phasenmessungen  

Microsoft Academic Search

The three-dimensional nature of Global Positioning System (GPS) measurements provides a unique opportunity for accurately determining the position and velocity of satellites in low Earth orbit (LEO). For optimum results a reduced dynamic technique is commonly preferred, which combines the merits of kinematic positioning techniques with those of a fully dynamic trajectory modeling. As part of the present study two

Oliver Montenbruck; Tom van Helleputte; Remco Kroes; Eberhard Gill

327

Chelyabinsk Superbolide: a detailed analysis of the passage through the~atmosphere and orbit determination  

NASA Astrophysics Data System (ADS)

A detailed analysis of the passage through the atmosphere of a very bright meteor that exploded in the air near Chelyabinsk, Russia on February 15, 2013 is presented. A number of videos and photographs were examined thoroughly to determine the meteor trajectory beginning from the recorded atmospheric entry height of about 62.5 km until its disappearance at about 9.8 km. The calculated velocity changes as a function time revealed an unusual behavior: during the first 10 seconds the meteor velocity increased from 16.6 km/s up to about 20.6 km/s in the main air burst at the altitude of 26.5 km. Afterwards it decreased rapidly. The light curves derived from videos enabled the total radiant energy and mass loss variations to be calculated. The heliocentric orbit of the meteoroid and possible parent bodies were computed. We proposed an additional 'close approaches' method to the existing method of checking meteoroid/bolide parent bodies based on different D-criteria.

W?odarczyk, K.; W?odarczyk, I.

2014-07-01

328

GEO/LEO satellites joint orbit determination based on satellite-to-satellite tracking  

NASA Astrophysics Data System (ADS)

TDRSS and Double Satellite Positioning System DSPS usually consist of two or three operational geosynchronous GEO satellites and a few customers LEO satellites The satellite-to-satellite tracking data provided by these systems put forward the requirement for multi-satellite joint orbit determination OD This paper will introduce the difference between OD with known GEO ephemeredes and OD with unknown GEO ephemeredes describe the measure model for sum of range observable and the difficulties on multi-satellite joint OD and examine the OD accuracy for the whole system The system including 2 GEOs 1 LEO and 3 ground stations tracking GEO is regarded as the standard mode for TDRSS or DSPS OD using the imitation observations on this mode indicates that GEO LEO satellites joint OD can achieve better positioning accuracy than LEO single satellite OD under the same measurement and force model error On the extreme mode 1 GEO 1 LEO 3 ground stations or 2 GEOs 1 LEO and 1 ground station the error on GEO satellite solar radiation force modeling is found to be decisive to the OD accuracy for the whole system On the constellation mode 2 GEOs N LEOs e g N 3 3 ground stations the accuracy of 5-satellite joint OD can get further improved compared with the standard 3-satellite OD mode

Wang, J. S.; Chen, J. R.; Wu, G. Y.; Li, J. S.; Chen, C. G.; Wang, Z. M.; Yang, K. Z.

329

Orbit-determination performance of Doppler data for interplanetary cruise trajectories. Part 1: Error analysis methodology  

NASA Technical Reports Server (NTRS)

An error covariance analysis methodology is used to investigate different weighting schemes for two-way (coherent) Doppler data in the presence of transmission-media and observing-platform calibration errors. The analysis focuses on orbit-determination performance in the interplanetary cruise phase of deep-space missions. Analytical models for the Doppler observable and for transmission-media and observing-platform calibration errors are presented, drawn primarily from previous work. Previously published analytical models were improved upon by the following: (1) considering the effects of errors in the calibration of radio signal propagation through the troposphere and ionosphere as well as station-location errors; (2) modelling the spacecraft state transition matrix using a more accurate piecewise-linear approximation to represent the evolution of the spacecraft trajectory; and (3) incorporating Doppler data weighting functions that are functions of elevation angle, which reduce the sensitivity of the estimated spacecraft trajectory to troposphere and ionosphere calibration errors. The analysis is motivated by the need to develop suitable weighting functions for two-way Doppler data acquired at 8.4 GHz (X-band) and 32 GHz (Ka-band). This weighting is likely to be different from that in the weighting functions currently in use; the current functions were constructed originally for use with 2.3 GHz (S-band) Doppler data, which are affected much more strongly by the ionosphere than are the higher frequency data.

Ulvestad, J. S.; Thurman, S. W.

1992-01-01

330

Determination of the initial billet geometry for a forged product using neural networks  

Microsoft Academic Search

In the paper, the authors propose a new technique to determine the initial billet geometry for the forged products using a function approximation in neural networks. A three-layer neural network is used and the back-propagation algorithm is employed to train the network. The billet geometry is determined by applying the ability of the function approximation of neural networks to determine

D. J Kim; B. M Kim; J. C Choi

1997-01-01

331

Lifetimes of lunar satellite orbits  

NASA Technical Reports Server (NTRS)

The Space Exploration Initiative has generated a renewed interest in lunar mission planning. The lunar missions currently under study, unlike the Apollo missions, involve long stay times. Several lunar gravity models have been formulated, but mission planners do not have enough confidence in the proposed models to conduct detailed studies of missions with long stay times. In this report, a particular lunar gravitational model, the Ferrari 5 x 5 model, was chosen to determine the lifetimes for 100-km and 300-km perilune altitude, near-circular parking orbits. The need to analyze orbital lifetimes for a large number of initial orbital parameters was the motivation for the formulation of a simplified gravitational model from the original model. Using this model, orbital lifetimes were found to be heavily dependent on the initial conditions of the nearly circular orbits, particularly the initial inclination and argument of perilune. This selected model yielded lifetime predictions of less than 40 days for some orbits, and other orbits had lifetimes exceeding a year. Although inconsistencies and limitations are inherent in all existing lunar gravity models, primarily because of a lack of information about the far side of the moon, the methods presented in this analysis are suitable for incorporating the moon's nonspherical gravitational effects on the preliminary design level for future lunar mission planning.

Meyer, Kurt W.; Buglia, James J.; Desai, Prasun N.

1994-01-01

332

22 CFR 215.9 - Appeal of initial adverse agency determination.  

Code of Federal Regulations, 2010 CFR

...designated in writing by the Director or Administrator, shall undertake an independent review of the initial determination...someone other than the Director or the Assistant Administrator...who is organizationally independent of or senior to the...

2010-04-01

333

49 CFR 7.31 - What time limits apply to DOT with respect to initial determinations?  

... 2014-10-01 2014-10-01 false What time limits apply to DOT with respect to initial determinations...Transportation PUBLIC AVAILABILITY OF INFORMATION Time Limits § 7.31 What time limits apply to DOT with respect to initial...

2014-10-01

334

Three Decades of Precision Orbit Determination Progress, Achievements, Future Challenges and its Vital Contribution to Oceanography and Climate Research  

NASA Technical Reports Server (NTRS)

Although satellite altimetry has been around for thirty years, the last fifteen beginning with the launch of TOPEX/Poseidon (TP) have yielded an abundance of significant results including: monitoring of ENS0 events, detection of internal tides, determination of accurate global tides, unambiguous delineation of Rossby waves and their propagation characteristics, accurate determination of geostrophic currents, and a multi-decadal time series of mean sea level trend and dynamic ocean topography variability. While the high level of accuracy being achieved is a result of both instrument maturity and the quality of models and correction algorithms applied to the data, improving the quality of the Climate Data Records produced from altimetry is highly dependent on concurrent progress being made in fields such as orbit determination. The precision orbits form the reference frame from which the radar altimeter observations are made. Therefore, the accuracy of the altimetric mapping is limited to a great extent by the accuracy to which a satellite orbit can be computed. The TP mission represents the first time that the radial component of an altimeter orbit was routinely computed with an accuracy of 2-cm. Recently it has been demonstrated that it is possible to compute the radial component of Jason orbits with an accuracy of better than 1-cm. Additionally, still further improvements in TP orbits are being achieved with new techniques and algorithms largely developed from combined Jason and TP data analysis. While these recent POD achievements are impressive, the new accuracies are now revealing subtle systematic orbit error that manifest as both intra and inter annual ocean topography errors. Additionally the construction of inter-decadal time series of climate data records requires the removal of systematic differences across multiple missions. Current and future efforts must focus on the understanding and reduction of these errors in order to generate a complete and consistent time series of improved orbits across multiple missions and decades required for the most stringent climate-related research. This presentation discusses the POD progress and achievements made over nearly three decades, and presents the future challenges, goals and their impact on altimetric derived ocean sciences.

Luthcke, Scott; Rowlands, David; Lemoine, Frank; Zelensky, Nikita; Beckley, Brian; Klosko, Steve; Chinn, Doug

2006-01-01

335

Biorthogonal Laurent Polynomials, Toplitz Determinants, Minimal Toda Orbits and Isomonodromic Tau Functions  

Microsoft Academic Search

We consider the class of biorthogonal polynomials that are used to solve the inverse spectral problem associated to elementary\\u000a co-adjoint orbits of the Borel group of upper triangular matrices; these orbits are the phase space of generalized integrable\\u000a lattices of Toda type. Such polynomials naturally interpolate between the theory of orthogonal polynomials on the line and\\u000a orthogonal polynomials on the

M. Bertola; M. Gekhtman

2007-01-01

336

Exploring gravity field determination from orbit perturbations of the European Gravity Mission GOCE  

Microsoft Academic Search

.  ?A comparison was made between two methods for gravity field recovery from orbit perturbations that can be derived from global\\u000a positioning system satellite-to-satellite tracking observations of the future European gravity field mission GOCE (Gravity\\u000a Field and Steady-State Ocean Circulation Explorer). The first method is based on the analytical linear orbit perturbation\\u000a theory that leads under certain conditions to a block-diagonal

P. N. A. M. Visser; J. van den IJssel; R. Koop; R. Klees

2001-01-01

337

A procedure of selection of meteors from major streams for determination of mean orbits  

Microsoft Academic Search

A procedure of selection of meteoroids from major streams is suggested and applied to the IAU Lund photographic database modified by a check for internal consistency among orbital elements (3411 orbits). Limits for choice of stream members were defined by break points on the plots of the cumulative numberNC vs. the Southworth-HawkinsD discriminant. For the break points were considered the

L. Neslusan; J. Svoren; V. Porub?an

1995-01-01

338

Determination of magnetic moments and orbital occupancy in the spin chain compound Ca3Co2O6  

NASA Astrophysics Data System (ADS)

The one-dimensional cobaltate Ca3Co2O6 exhibits a number of intriguing phenomena, including several metamagnetic steps as a function of applied magnetic field. Although it has attracted a considerable amount of research, the origin of the magnetism has not yet been fully determined. We report a measurement of the spin density in Ca3Co2O6 using magnetic Compton scattering. The bulk spin moment was determined to be 3.78 ± 0.05?B at 7 T, confirming the existence of a large unquenched Co orbital moment of 1.4 ± 0.1 ?B. In combination with molecular orbital calculations, the results reveal that double occupation of the dx^2-y^2,xy orbital is responsible for the observed large unquenched orbital moment. Fitting the model to the experimental data shows that there is an induced oxygen moment of 0.8 ± 0.1 ?B. Unexpectedly, further comparison with KKR-SPA electronic structure calculations strongly indicates the existence of a Fermi surface.

Duffy, Jonathan; Butchers, Matthew; Taylor, Jonathan; Dugdale, Stephen; Haynes, Tom; Agrestini, Stefano; Lees, Martin

2011-03-01

339

Initial results from ground-based testing of an atomic oxygen sensor designed for use in earth orbit  

Microsoft Academic Search

Many sensors have been applied to the problem of measuring neutral atomic oxygen fluxes in low Earth orbit. The techniques used to date tend to suffer from several key disadvantages, variously: large mass and power budgets, large size, high cost, the ability to make only one measurement and poor time resolution. In this article preliminary results from ground-based testing of

J. J. Osborne; G. T. Roberts; A. R. Chambers; S. B. Gabriel

1999-01-01

340

A combined effective fragment potential-fragment molecular orbital method. I. The energy expression and initial applications  

Microsoft Academic Search

The effective fragment potential (EFP) method, a model potential for treating solvent effects and other intermolecular interactions, is interfaced with an electronic structure method, the fragment molecular orbital (FMO) method, that is able to retain high accuracy for ab initio calculations on large molecular systems. The accuracy of the total energies in this novel combined FMO\\/EFP method is assessed by

Takeshi Nagata; Dmitri G. Fedorov; Kazuo Kitaura; Mark S. Gordon

2009-01-01

341

A combined effective fragment potential–fragment molecular orbital method. I. The energy expression and initial applications  

Microsoft Academic Search

The effective fragment potential (EFP) method, a model potential for treating solvent effects and other intermolecular interactions, is interfaced with an electronic structure method, the fragment molecular orbital (FMO) method, that is able to retain high accuracy for ab initio calculations on large molecular systems. The accuracy of the total energies in this novel combined FMO\\/EFP method is assessed by

Takeshi Nagata; Dmitri G. Fedorov; Kazuo Kitaura; Mark S. Gordon

2009-01-01

342

Determination of the area and mass distribution of orbital debris fragments  

NASA Technical Reports Server (NTRS)

An important factor in modeling the orbital debris environment is the loss rate of debris due to atmospheric drag and lunisolar perturbations. An accurate knowledge of the area-to-mass ratio of debris fragments is required to calculate the effects of atmospheric drag. It is shown here that the orbital elements as a function of time can be used to invert any propagation algorithm to yield the area-to-mass ratio of an orbiting object. From these calculations and the observed radar cross-section of the object, the mass can be calculated to an accuracy of about 30 percent. It is shown that the mass is related to the effective cross-section area by a power-law relation, but for a given area the mass distribution is very broad. An expression is given for the cumulative mass distribution.

Badhwar, G. D.; Anz-Meador, P. D.

1988-01-01

343

Determining the nature of orbits in disk galaxies with non spherical nuclei  

E-print Network

We investigate the regular or chaotic nature of orbits of stars moving in the meridional plane $(R,z)$ of an axially symmetric galactic model with a flat disk and a central, non spherical and massive nucleus. In particular, we study the influence of the flattening parameter of the central nucleus on the nature of orbits, by computing in each case the percentage of chaotic orbits, as well as the percentages of orbits of the main regular families. In an attempt to maximize the accuracy of our results upon distinguishing between regular and chaotic motion, we use both the Fast Lyapunov Indicator (FLI) and the Smaller ALingment Index (SALI) methods to extensive samples of orbits obtained by integrating numerically the equations of motion as well as the variational equations. Moreover, a technique which is based mainly on the field of spectral dynamics that utilizes the Fourier transform of the time series of each coordinate is used for identifying the various families of regular orbits and also to recognize the secondary resonances that bifurcate from them. Varying the value of the flattening parameter, we study three different cases: (i) the case where we have a prolate nucleus (ii) the case where the central nucleus is spherical and (iii) the case where an oblate massive nucleus is present. Furthermore, we present some additional findings regarding the reliability of short time (fast) chaos indicators, as well as a new method to define the threshold between chaos and regularity for both FLI and SALI, by using them simultaneously. Comparison with early related work is also made.

Euaggelos E. Zotos; Nicolaos D. Caranicolas

2014-04-15

344

Direct and quantitative determination of the orbital ordering in CeB6 by X-ray diffraction  

Microsoft Academic Search

Results of non-resonant X-ray Bragg diffraction by CeB6 are reported. This material has been described in terms of a simple antiferro-quadrupolar order below TQ = 3.2 K. We determine for the first time, directly and quantitatively the orbital ordering in this material. In particular, we find direct evidence for a simultaneous ordering of a quadrupole (QP) and a hexadecapole (HDP)

Y. Tanaka; U. Staub; K. Katsumata; S. W. Lovesey; J. E. Lorenzo; Y. Narumi; V. Scagnoli; S. Shimomura; Y. Tabata; Y. Onuki; Y. Kuramoto; A. Kikkawa; T. Ishikawa; H. Kitamura

2004-01-01

345

Orbit determination accuracies using satellite-to-satellite tracking. [applicable to the Tracking and Data Relay Satellite system  

NASA Technical Reports Server (NTRS)

The results of the ATS-6/GEOS-3 and the ATS-6/NIMBUS-6 satellite-to-satellite tracking orbit determination experiments are reported. The tracking systems used in these experiments differ from the Tracking and Data Relay Satellite System (TDRSS), primarily in the use of one rather than two synchronous relay satellites. However, the simulations mentioned indicate that the insights gained from the experiments with regard to proper data reduction techniques and expected results are applicable to the TDRSS.

Vonbun, F. O.; Argentiero, P. D.; Schmid, P. E.

1978-01-01

346

Ionosphere Plasma State Determination in Low Earth Orbit from International Space Station Plasma Monitor  

NASA Technical Reports Server (NTRS)

A plasma diagnostic package is deployed on the International Space Station (ISS). The system - a Floating Potential Measurement Unit (FPMU) - is used by NASA to monitor the electrical floating potential of the vehicle to assure astronaut safety during extravehicular activity. However, data from the unit also reflects the ionosphere state and seems to represent an unutilized scientific resource in the form of an archive of scientific plasma state data. The unit comprises a Floating Potential probe and two Langmuir probes. There is also an unused but active plasma impedance probe. The data, at one second cadence, are collected, typically for a two week period surrounding extravehicular activity events. Data is also collected any time a visiting vehicle docks with ISS and also when any large solar events occur. The telemetry system is unusual because the package is mounted on a television camera stanchion and its data is impressed on a video signal that is transmitted to the ground and streamed by internet to two off center laboratory locations. The data quality has in the past been challenged by weaknesses in the integrated ground station and distribution systems. These issues, since mid-2010, have been largely resolved and the ground stations have been upgraded. Downstream data reduction has been developed using physics based modeling of the electron and ion collecting character in the plasma. Recursive algorithms determine plasma density and temperature from the raw Langmuir probe current voltage sweeps and this is made available in real time for situational awareness. The purpose of this paper is to describe and record the algorithm for data reduction and to show that the Floating probe and Langmuir probes are capable of providing long term plasma state measurement in the ionosphere. Geophysical features such as the Appleton anomaly and high latitude modulation at the edge of the Auroral zones are regularly observed in the nearly circular, 51 deg inclined, 400 km altitude ISS orbit. Evidence of waves in the ion collection current data is seen in geographic zones known to exhibit the spread-F phenomenon. An anomaly in the current collection characteristic of the cylindrical probe appears also too be organized by the geomagnetic field.

Kramer, Leonard

2014-01-01

347

Determination of the orbital parameters of the M 51 system using a genetic algorithm  

Microsoft Academic Search

Using an efficient method based on genetic algorithms, we have searched for an optimum set of parameters for the interaction between NGC 5194 (M 51) and NGC 5195. The preferred model is one where the time of closest passage was 900 Myr ago. The orbit of NGC 5195 is almost perpendicular to the plane of the sky, and is slightly

M. Wahde; K. J. Donner

2001-01-01

348

A new determination of lunar orbital parameters, precession constant and tidal acceleration from LLR measurements  

Microsoft Academic Search

An analysis of Lunar Laser Ranging (LLR) observations from January 1972 until April 2001 has been performed, and a new solution for the lunar orbital motion and librations has been constructed that has been named S2001. With respect to prior solutions, improvements in the statistical treatment of the data, new nutation and libration models and the addition of the positions

J. Chapront; M. Chapront-Touzé; G. Francou

2002-01-01

349

Determining the dimensionality of bipartite orbital-angular-momentum entanglement using multi-sector phase masks  

E-print Network

The Shannon dimensionality of orbital angular momentum (OAM) entanglement produced in spontaneous parametric down-conversion can be probed by using multi-sector phase analysers. We demonstrate a spatial light modulator-based implementation of these analysers, and use it to measure a Schmidt number of about 50.

D. Giovannini; F. M. Miatto; J. Romero; S. M. Barnett; J. P. Woerdman; M. J. Padgett

2012-07-10

350

Comparison of Different Algorithms of Orbit Determination Using Radar Measurements Acquired  

Microsoft Academic Search

Efficient solution of the problem of warning of collisions between important spacecraft and other orbiting satellites requires expanding of the catalog of tracked satellites (currently comprising about 15,000 satellites) by an order of magnitude or more. This is a very difficult scientific and technical task. One of the major aspects is the creation of software tools capable of automatic maintenance

K. Alfriend; Z. Khutorovsky; S. Sukhanov; N. Sbytov; S. Kamensky

2009-01-01

351

Orbit Determination During Spacecraft Emergencies with Sparse Tracking Data - THEMIS and TDRS-3 Lessons Learned  

NASA Technical Reports Server (NTRS)

This paper provides an overview of the lessons learned from the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center s (GSFC) Flight Dynamics Facility s (FDF) support of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft emergency in February 2007, and the Tracking and Data Relay Satellite-3 (TDRS-3) spacecraft emergency in March 2006. A successful and timely recovery from both of these spacecraft emergencies depended on accurate knowledge of the orbit. Unfortunately, the combination of each spacecraft emergency with very little tracking data contributed to difficulties in estimating and predicting the orbit and delayed recovery efforts in both cases. In both the THEMIS and TDRS-3 spacecraft emergencies, numerous factors contributed to problems with obtaining nominal tracking data measurements. This paper details the various causative factors and challenges. This paper further enumerates lessons learned from FDF s recovery efforts involving the THEMIS and TDRS-3 spacecraft emergencies and scant tracking data, as well as recommendations for improvements and corrective actions. In addition, this paper describes the broad range of resources and complex navigation methods employed within the FDF for supporting critical navigation activities during all mission phases, including launch, early orbit, and on-orbit operations.

Morinelli, Patrick J.; Ward, Douglas T.; Blizzard, Michael R.; Mendelsohn, Chad R.

2008-01-01

352

12 CFR 563b.460 - How do I determine the initial balances of liquidation sub-accounts?  

Code of Federal Regulations, 2011 CFR

...false How do I determine the initial balances of liquidation sub-accounts? 563b...460 How do I determine the initial balances of liquidation sub-accounts? ...You determine the initial sub-account balance for a savings account held by an...

2011-01-01

353

12 CFR 192.460 - How do I determine the initial balances of liquidation sub-accounts?  

...false How do I determine the initial balances of liquidation sub-accounts? 192...460 How do I determine the initial balances of liquidation sub-accounts? ...You determine the initial sub-account balance for a savings account held by an...

2014-01-01

354

12 CFR 192.460 - How do I determine the initial balances of liquidation sub-accounts?  

Code of Federal Regulations, 2012 CFR

...false How do I determine the initial balances of liquidation sub-accounts? 192...460 How do I determine the initial balances of liquidation sub-accounts? ...You determine the initial sub-account balance for a savings account held by an...

2012-01-01

355

12 CFR 563b.460 - How do I determine the initial balances of liquidation sub-accounts?  

...true How do I determine the initial balances of liquidation sub-accounts? 563b...460 How do I determine the initial balances of liquidation sub-accounts? ...You determine the initial sub-account balance for a savings account held by an...

2014-01-01

356

12 CFR 563b.460 - How do I determine the initial balances of liquidation sub-accounts?  

Code of Federal Regulations, 2013 CFR

...true How do I determine the initial balances of liquidation sub-accounts? 563b...460 How do I determine the initial balances of liquidation sub-accounts? ...You determine the initial sub-account balance for a savings account held by an...

2013-01-01

357

12 CFR 563b.460 - How do I determine the initial balances of liquidation sub-accounts?  

Code of Federal Regulations, 2012 CFR

...false How do I determine the initial balances of liquidation sub-accounts? 563b...460 How do I determine the initial balances of liquidation sub-accounts? ...You determine the initial sub-account balance for a savings account held by an...

2012-01-01

358

12 CFR 192.460 - How do I determine the initial balances of liquidation sub-accounts?  

Code of Federal Regulations, 2013 CFR

...false How do I determine the initial balances of liquidation sub-accounts? 192...460 How do I determine the initial balances of liquidation sub-accounts? ...You determine the initial sub-account balance for a savings account held by an...

2013-01-01

359

12 CFR 563b.460 - How do I determine the initial balances of liquidation sub-accounts?  

Code of Federal Regulations, 2010 CFR

...false How do I determine the initial balances of liquidation sub-accounts? 563b...460 How do I determine the initial balances of liquidation sub-accounts? ...You determine the initial sub-account balance for a savings account held by an...

2010-01-01

360

Discovery and Orbital Determination of the Transient X-Ray Pulsar GRO J1750-27  

NASA Technical Reports Server (NTRS)

We report on the discovery and hard X-ray (20 - 70 keV) observations of the 4.45 s period transient X-ray pulsar GRO J1750-27 with the BATSE all-sky monitor on board CGRO. A relatively faint out- burst (less than 30 mcrab peak) lasting at least 60 days was observed during which the spin-up rate peaked at 38 pHz/s and was correlated with the pulsed intensity. An orbit with a period of 29.8 days was found. The large spin-up rate, spin period, and orbital period together suggest that accretion is occurring from a disk and that the outburst is a "giant" outburst typical of a Be/X-ray transient system. No optical counterpart has yet been reported.

Scott, D. M.; Finger, M. H.; Wilson, R. B.; Koh, D. T.; Prince, T. A.; Vaughan, B. A.; Chakrabarty, D.

1997-01-01

361

Discovery and Orbital Determination of the Transient X-Ray Pulsar GRO J1750-27  

NASA Technical Reports Server (NTRS)

We report on the discovery and hard X-ray (20-70 keV) observations of the 4.45 second period transient X-ray pulsar GRO J1750-27 with the BATSE all-sky monitor on board CCRO. A relatively faint outburst (< 30 mCrab peak) lasting at least 60 days was observed during which the spin-up rate peaked at 38 pHz/sec and was correlated with the pulsed intensity. An orbit with a period of 29.8 days was found. The large spin-up rate, spin period and orbital period together suggest that accretion is occurring from a disk and that the outburst is a 'giant' outburst typical of a Be/X-ray transient system. No optical counterpart has been reported yet.

Scott, D. M.; Finger, M. H.; Wilson, R. B.; Koh, D. T.; Prince, T. A.; Vaughan, B. A.; Chakrabarty, D.

1997-01-01

362

Social determinants of health in Canada: Are healthy living initiatives there yet? A policy analysis  

PubMed Central

Introduction Preventative strategies that focus on addressing the social determinants of health to improve healthy eating and physical activity have become an important strategy in British Columbia and Ontario for combating chronic diseases. What has not yet been examined is the extent to which healthy living initiatives implemented under these new policy frameworks successfully engage with and change the social determinants of health. Methods Initiatives active between January 1, 2006 and September 1, 2011 were found using provincial policy documents, web searches, health organization and government websites, and databases of initiatives that attempted to influence to nutrition and physical activity in order to prevent chronic diseases or improve overall health. Initiatives were reviewed, analyzed and grouped using the descriptive codes: lifestyle-based, environment-based or structure-based. Initiatives were also classified according to the mechanism by which they were administered: as direct programs (e.g. directly delivered), blueprints (or frameworks to tailor developed programs), and building blocks (resources to develop programs). Results 60 initiatives were identified in Ontario and 61 were identified in British Columbia. In British Columbia, 11.5% of initiatives were structure-based. In Ontario, of 60 provincial initiatives identified, 15% were structure-based. Ontario had a higher proportion of direct interventions than British Columbia for all intervention types. However, in both provinces, as the intervention became more upstream and attempted to target the social determinants of health more directly, the level of direct support for the intervention lessened. Conclusions The paucity of initiatives in British Columbia and Ontario that address healthy eating and active living through action on the social determinants of health is problematic. In the context of Canada's increasingly neoliberal political and economic policy, the public health sector may face significant barriers to addressing upstream determinants in a meaningful way. If public health cannot directly affect broader societal conditions, interventions should be focused around advocacy and education about the social determinants of health. It is necessary that health be seen for what it is: a political matter. As such, the health sector needs to take a more political approach in finding solutions for health inequities. PMID:22889402

2012-01-01

363

Minimal topological actions do not determine the measurable orbit equivalence class  

Microsoft Academic Search

We construct a minimal topological action $\\\\wp$ of a non-amenable group on a\\u000aCantor set $C$, which is non-uniquely ergodic and furthermore there exist\\u000aergodic invariant measures $\\\\mu_1$ and $\\\\mu_2$ such that $(\\\\wp,C,\\\\mu_1)$ and\\u000a$(\\\\wp,C,\\\\mu_2)$ are not orbit equivalent measurable equivalence relations.

Tullio Ceccherini-Silberstein; Gábor Elek

2008-01-01

364

Determination of the Orbital Moment and Crystal-Field Splitting in LaTiO3  

Microsoft Academic Search

Utilizing a sum rule in a spin-resolved photoelectron spectroscopic experiment with circularly polarized light, we show that the orbital moment in LaTiO3 is strongly reduced from its ionic value, both below and above the Néel temperature. Using Ti L2,3 x-ray absorption spectroscopy as a local probe, we found that the crystal-field splitting in the t2g subshell is about 0.12 0.30eV.

M. W. Haverkort; Z. Hu; A. Tanaka; G. Ghiringhelli; H. Roth; M. Cwik; T. Lorenz; C. Schüßler-Langeheine; S. V. Streltsov; A. S. Mylnikova; V. I. Anisimov; C. de Nadai; N. B. Brookes; H. H. Hsieh; H.-J. Lin; C. T. Chen; T. Mizokawa; Y. Taguchi; Y. Tokura; D. I. Khomskii; L. H. Tjeng

2005-01-01

365

An exact inversion method for the determination of spin–orbit potentials from scattering data  

Microsoft Academic Search

:   A generalized Newton–Sabatier inversion method which permits extraction from scattering data of central and spin-orbit potentials\\u000a is presented. The inversion method originally developed by Sabatier and further elaborated by Hooshyar and Richardson, has\\u000a been reformulated to lead to physically reasonable solutions and to allow for its numerical implementation. Numerical problems\\u000a due to the occurrence of singularities in the transformation

H. Leeb

1998-01-01

366

Role of heavy-ion nuclear reactions in determining on-orbit single event error rates  

Microsoft Academic Search

Simulations show that neglecting ion-ion interaction processes (both particles having Z>1) results in an underestimation of the total on-orbit single event upset error rate by more than two orders of magnitude for certain technologies. The inclusion of ion-ion nuclear reactions leads to dramatically different SEU error rates for CMOS devices containing high Z materials compared with direct ionization by the

Christina L. Howe; Robert A. Weller; Robert A. Reed; Marcus H. Mendenhall; Ronald D. Schrimpf; Kevin M. Warren; Dennis R. Ball; Lloyd W. Massengill; Kenneth A. LaBel; Nadim F. Haddad

2005-01-01

367

On the simultaneous improvement of a satellite orbit and determination of sea surface topography using altimeter data  

NASA Technical Reports Server (NTRS)

A method is presented in satellite altimetry that attempts to simultaneously determine the geoid and sea surface toography with minimum wavelengths of about 500 km and to reduce the radial orbit errors caused by geopotential uncertainties. The modeling of these errors is made using the linearized Lagrangian perturbation theory. Observation equations are developed using sea surface heights and crossover discrepancies as observables. A minimum variance solution with prior information can then provide estimates of parametrs representing the sea surface topography and corrections to the orbit. The potential of the method is demonstrated in a solution where simulated geopotential errors and the Levitus sea surface topography are used to generate the observables for a Seasat 3 day arc. The simulation results suggest that the method can be used to efficiently process real altimeter data.

Engelis, Theodossios

1988-01-01

368

Determination of the orbit spaces of non-coregular compact linear groups with one relation among the basic polynomial invariants in the $\\\\hat P$-matrix approach  

Microsoft Academic Search

Invariant functions under the transformations of a compact linear group $G$ acting in $\\\\real^n$ can be expressed in terms of functions defined in the orbit space of $G$. We develop a method to determine the isotropy classes of the orbit spaces of all the real linear groups whose integrity bases (IB) satisfy only one independent relation. The method is tested

G. Sartori; G. Valente

2000-01-01

369

Spacecraft preliminary orbit determination using tracking measurements obtained from the Tracking and Data Relay Satellite System (TDRSS) and the Ground Spaceflight Tracking and Data Network (GSTDN)  

NASA Technical Reports Server (NTRS)

In order to validate the operational and computational capabilities of the Preliminary Orbit Determination System (PODS), tests were performed using tracking measurements for several systems including the ERB satellite, the SMM, the STS and Landsat-4. POD procedures are utilized to generate a state vector following an unplanned orbital perturbation or spacecraft maneuver, when an estimation process such as a differential correction orbit determination cannot obtain a solution. Results are presented to demonstrate POD for several situations involving different qualities of a priori target state vectors, data type combinations, data arc lengths, and mixtures of single-TDRS, dual-TDRS, and GSTDN measurements. The system's ability to determine accurately the state vector for the spacecraft and the effectiveness of the solution screening process are discussed. It is shown that PODS is capable of determining a spacecraft vector when differential correction orbit determination processes fail.

Kirschner, S. M.; Beri, A. C.; Broaddus, S. R.; Doll, C. E.

1990-01-01

370

Manned Venus Orbiting Mission  

NASA Technical Reports Server (NTRS)

Manned orbiting stopover round trips to Venus are studied for departure dates between 1975 and 1986 over a range of trip times and stay times. The use of highly elliptic parking orbits at Venus leads to low initial weights in Earth orbit compared with circular orbits. For the elliptic parking orbit, the effect of constraints on the low altitude observation time on the initial weight is shown. The mission can be accomplished with the Apollo level of chemical propulsion, but advanced chemical or nuclear propulsion can give large weight reductions. The Venus orbiting mission weights than the corresponding Mars mission.

Willis, E. A., Jr.

1967-01-01

371

A combined effective fragment potential-fragment molecular orbital method. I. The energy expression and initial applications  

NASA Astrophysics Data System (ADS)

The effective fragment potential (EFP) method, a model potential for treating solvent effects and other intermolecular interactions, is interfaced with an electronic structure method, the fragment molecular orbital (FMO) method, that is able to retain high accuracy for ab initio calculations on large molecular systems. The accuracy of the total energies in this novel combined FMO/EFP method is assessed by comparisons with the conventional quantum mechanics (QM)/EFP method. The test cases are water clusters, a peptide, and a dianionic protein (treated with full QM and FMO) combined with water clusters (treated with EFP) at the RHF, B3LYP, and MP2 levels of theory. The basis sets employed range from minimal to augmented double zeta plus polarization. The energy differences between FMO/EFP and the conventional QM/EFP methods are within "chemical accuracy" (1 kcal/mol?4 kJ/mol).

Nagata, Takeshi; Fedorov, Dmitri G.; Kitaura, Kazuo; Gordon, Mark S.

2009-07-01

372

Initial results from ground-based testing of an atomic oxygen sensor designed for use in earth orbit  

NASA Astrophysics Data System (ADS)

Many sensors have been applied to the problem of measuring neutral atomic oxygen fluxes in low Earth orbit. The techniques used to date tend to suffer from several key disadvantages, variously: large mass and power budgets, large size, high cost, the ability to make only one measurement and poor time resolution. In this article preliminary results from ground-based testing of a novel atomic oxygen sensor based on a semiconducting metal oxide are reported. Such sensors are simple and relatively cheap while also requiring small power and mass budgets and, most importantly, are reusable. The sensors have been used in laboratory experiments to investigate the axial variation of atomic oxygen flux in a pulsed laser atomic oxygen source; the results compare well with readings taken with a carbon-coated quartz crystal microbalance. A small instrument based on these sensors has been designed and built for application on the UK's STRV-1c microsatellite.

Osborne, J. J.; Roberts, G. T.; Chambers, A. R.; Gabriel, S. B.

1999-05-01

373

The dynamics of global positioning system orbits and the determination of precise ephemerides  

NASA Technical Reports Server (NTRS)

The suggestion made on the basis of the analytical orbit perturbation theory that the errors in the ephemerides of the GPS satellites are due mostly to resonant effects that can be corrected by adjusting a few parameters in a empirical acceleration formula is tested using simulations and actual data analysis. Data from the Spring 1985 Experiment were used to calculate improved ephemerides, and these ephemerides were used in the estimation of the coordinates of GPS stations within the continental United States, previously positioned with VLBI. The results of this test support the idea that the errors are mostly of a resonant nature and can be corrected.

Colombo, Oscar L.

1989-01-01

374

Space Shuttle orbit determination using empirical force modeling of attitude maneuvers for the German MOMS-02/D2 mission  

NASA Technical Reports Server (NTRS)

In the spring of 1993, the MOMS-02 (modular Optoelectronic Multispectral Scanner) camera, as part of the second German Spacelab mission aboard STS-55, successfully took digital threefold stereo images of the surface of the Earth. While the mission is experimental in nature, its primary goals are to produce high quality maps and three-dimensional digital terrain models of the Earth's surface. Considerable improvement in the quality of the terrain model can be attained if information about the position and attitude of the camera is included during the adjustment of the image data. One of the primary sources of error in the Shuttle's position is due to the significant attitude maneuvers conducted during the course of the mission. Various arcs, using actual Tracking and Data Relay Satellite (TDRSS) Doppler data of STS-55, were processed to determine how effectively empirical force modeling could be used to solve for the radial, transverse, and normal components of the orbit perturbations caused by these routine maneuvers. Results are presented in terms of overlap-orbit differences in the three components. Comparisons of these differences, before and after the maneuvers are estimated, show that the quality of an orbit can be greatly enhanced with this technique, even if several maneuvers are present. Finally, a discussion is made of some of the difficulties encountered with this approach, and some ideas for future studies are presented.

Vonbraun, C.; Reigber, Christoph

1994-01-01

375

The effect of initial velocity on manually controlled remote docking of an orbital maneuvering vehicle (OMV) to a space station  

NASA Technical Reports Server (NTRS)

Simulated docking maneuvers were performed to assess the effect of initial velocity on docking failure rate, mission duration, and total impulse (fuel consumption). The effect of the removal of the range and rate displays was also examined. Since duration and impulse decrease and increase respectively with increases in initial velocity, two parameters were created by subtracting a reference value from each. These values were termed 'reserve time' and 'radial impulse'. Naive subjects were capable of achieving a high success rate in performing simulated docking maneuvers without extensive experience, and failure rate did not significantly increase with increased velocity. The amount of time pilots reserved for final approach increased with starting velocity. Piloting of docking maneuvers was not significantly affected in any way by the removal of range and rate displays. Values for reserve time, and radial impulse were lowest for docking maneuvers begun at the lowest initial velocity.

Brody, Adam R.

1989-01-01

376

Nonconservative force model parameter estimation strategy for TOPEX/Poseidon precision orbit determination  

NASA Technical Reports Server (NTRS)

The TOPEX/Poseidon spacecraft was launched on August 10, 1992 to study the Earth's oceans. To achieve maximum benefit from the altimetric data it is to collect, mission requirements dictate that TOPEX/Poseidon's orbit must be computed at an unprecedented level of accuracy. To reach our pre-launch radial orbit accuracy goals, the mismodeling of the radiative nonconservative forces of solar radiation, Earth albedo an infrared re-radiation, and spacecraft thermal imbalances cannot produce in combination more than a 6 cm rms error over a 10 day period. Similarly, the 10-day drag modeling error cannot exceed 3 cm rms. In order to satisfy these requirements, a 'box-wing' representation of the satellite has been developed in which, the satellite is modelled as the combination of flat plates arranged in the shape of a box and a connected solar array. The radiative/thermal nonconservative forces acting on each of the eight surfaces are computed independently, yielding vector accelerations which are summed to compute the total aggregate effect on the satellite center-of-mass. Select parameters associated with the flat plates are adjusted to obtain a better representation of the satellite acceleration history. This study analyzes the estimation of these parameters from simulated TOPEX/Poseidon laser data in the presence of both nonconservative and gravity model errors. A 'best choice' of estimated parameters is derived and the ability to meet mission requirements with the 'box-wing' model evaluated.

Luthcke, S. B.; Marshall, J. A.

1992-01-01

377

International Low-Earth-Orbit Spacecraft Materials Test Program Initiated for Better Prediction of Durability and Performance  

NASA Technical Reports Server (NTRS)

Spacecraft in low Earth orbit (LEO) are subjected to many components of the environment, which can cause them to degrade much more rapidly than intended and greatly shorten their functional life. The atomic oxygen, ultraviolet radiation, and cross contamination present in LEO can affect sensitive surfaces such as thermal control paints, multilayer insulation, solar array surfaces, and optical surfaces. The LEO Spacecraft Materials Test (LEO-SMT) program is being conducted to assess the effects of simulated LEO exposure on current spacecraft materials to increase understanding of LEO degradation processes as well as to enable the prediction of in-space performance and durability. Using ground-based simulation facilities to test the durability of materials currently flying in LEO will allow researchers to compare the degradation evidenced in the ground-based facilities with that evidenced on orbit. This will allow refinement of ground laboratory test systems and the development of algorithms to predict the durability and performance of new materials in LEO from ground test results. Accurate predictions based on ground tests could reduce development costs and increase reliability. The wide variety of national and international materials being tested represent materials being functionally used on spacecraft in LEO. The more varied the types of materials tested, the greater the probability that researchers will develop and validate predictive models for spacecraft long-term performance and durability. Organizations that are currently participating in the program are ITT Research Institute (USA), Lockheed Martin (USA), MAP (France), SOREQ Nuclear Research Center (Israel), TNO Institute of Applied Physics (The Netherlands), and UBE Industries, Ltd. (Japan). These represent some of the major suppliers of thermal control and sensor materials currently flying in LEO. The participants provide materials that are exposed to selected levels of atomic oxygen, vacuum ultraviolet radiation, contamination, or synergistic combined environments at the NASA Lewis Research Center. Changes in characteristics that could affect mission performance or lifetime are then measured. These characteristics include changes in mass, solar absorptance, and thermal emittance. The durability of spacecraft materials from U.S. suppliers is then compared with those of materials from other participating countries. Lewis will develop and validate performance and durability prediction models using this ground data and available space data. NASA welcomes the opportunity to consider additional international participants in this program, which should greatly aid future spacecraft designers as they select materials for LEO missions.

Rutledge, Sharon K.

1999-01-01

378

Orbital geometry determined by orthogonal high-order harmonic polarization components  

SciTech Connect

We study the polarization state of high-order harmonics produced by linearly polarized light interacting with two-center molecules. By generating high-harmonic 'polarization maps' from Radon transformations of excited electronic wave functions, we show that the polarization of the harmonic radiation can be linked to the geometry of the molecular orbital. While in the Radon transformation the plane-wave approximation for the rescattered electron is implicitly assumed, numerical solutions of the two-dimensional time-dependent Schro{center_dot}{center_dot}dinger equation, in which this approximation is not made, confirm the validity of this topological connection. We also find that measuring two orthogonal amplitude components of the harmonics provides a method for quantum tomography that substantially improves the quality of reconstructed molecular states.

Hijano, Eliot [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); Serrat, Carles [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); DTDI, Universitat de Vic, Carrer de la Laura 13, E-08500 Vic (Barcelona) (Spain); Gibson, George N. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Biegert, Jens [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); ICREA-Institucio Catalana de Recerca i Estudis Avancats, E-08010 Barcelona (Spain)

2010-04-15

379

Comet C/2011 W3 (Lovejoy): Orbit Determination, Outbursts, Disintegration of Nucleus, Dust-tail Morphology, and Relationship to New Cluster of Bright Sungrazers  

NASA Astrophysics Data System (ADS)

We describe the physical and orbital properties of C/2011 W3. After surviving perihelion passage, the comet was observed to undergo major physical changes. The permanent loss of the nuclear condensation and the formation of a narrow spine tail were observed first at Malargue, Argentina, on December 20 and then systematically at Siding Spring, Australia. The process of disintegration culminated with a terminal fragmentation event on December 17.6 UT. The postperihelion dust tail, observed for ~3 months, was the product of activity over <2 days. The nucleus' breakup and crumbling were probably caused by thermal stress due to the penetration of the intense heat pulse deep into the nucleus' interior after perihelion. The same mechanism may be responsible for cascading fragmentation of sungrazers at large heliocentric distances. The delayed response to the hostile environment in the solar corona is at odds with the rubble-pile model, since the residual mass of the nucleus, estimated at ~1012 g (equivalent to a sphere 150-200 m across) just before the terminal event, still possessed nontrivial cohesive strength. The high production rates of atomic oxygen, observed shortly after perihelion, are compatible with a subkilometer-sized nucleus. The spine tail—the product of the terminal fragmentation—was a synchronic feature, whose brightest part contained submillimeter-sized dust grains, released at velocities of up to 30 m s-1. The loss of the nuclear condensation prevented an accurate orbital-period determination by traditional techniques. Since the missing nucleus must have been located on the synchrone, whose orientation and sunward tip have been measured, we compute the astrometric positions of this missing nucleus as the coordinates of the points of intersection of the spine tail's axis with the lines of forced orbital-period variation, derived from the orbital solutions based on high-quality preperihelion astrometry from the ground. The resulting orbit gives 698 ± 2 yr for the osculating orbital period, showing that C/2011 W3 is the first member of the expected new, 21st-century cluster of bright Kreutz-system sungrazers, whose existence was predicted by these authors in 2007. From the spine tail's evolution, we determine that its measured tip, populated by dust particles 1-2 mm in diameter, receded antisunward from the computed position of the missing nucleus. The bizarre appearance of the comet's dust tail in images taken only hours after perihelion with the coronagraphs on board the SOHO and STEREO spacecraft is readily understood. The disconnection of the comet's head from the tail released before perihelion and an apparent activity attenuation near perihelion have a common cause—sublimation of all dust at heliocentric distances smaller than about 1.8 solar radii. The tail's brightness is strongly affected by forward scattering of sunlight by dust. From an initially broad range of particle sizes, the grains that were imaged the longest had a radiation-pressure parameter ? ~= 0.6, diagnostic of submicron-sized silicate grains and consistent with the existence of the dust-free zone around the Sun. The role and place of C/2011 W3 in the hierarchy of the Kreutz system and its genealogy via a 14th-century parent suggest that it is indirectly related to the celebrated sungrazer X/1106 C1, which, just as the first-generation parent of C/2011 W3, split from a common predecessor during the previous return to perihelion.

Sekanina, Zdenek; Chodas, Paul W.

2012-10-01

380

COMET C/2011 W3 (LOVEJOY): ORBIT DETERMINATION, OUTBURSTS, DISINTEGRATION OF NUCLEUS, DUST-TAIL MORPHOLOGY, AND RELATIONSHIP TO NEW CLUSTER OF BRIGHT SUNGRAZERS  

SciTech Connect

We describe the physical and orbital properties of C/2011 W3. After surviving perihelion passage, the comet was observed to undergo major physical changes. The permanent loss of the nuclear condensation and the formation of a narrow spine tail were observed first at Malargue, Argentina, on December 20 and then systematically at Siding Spring, Australia. The process of disintegration culminated with a terminal fragmentation event on December 17.6 UT. The postperihelion dust tail, observed for {approx}3 months, was the product of activity over <2 days. The nucleus' breakup and crumbling were probably caused by thermal stress due to the penetration of the intense heat pulse deep into the nucleus' interior after perihelion. The same mechanism may be responsible for cascading fragmentation of sungrazers at large heliocentric distances. The delayed response to the hostile environment in the solar corona is at odds with the rubble-pile model, since the residual mass of the nucleus, estimated at {approx}10{sup 12} g (equivalent to a sphere 150-200 m across) just before the terminal event, still possessed nontrivial cohesive strength. The high production rates of atomic oxygen, observed shortly after perihelion, are compatible with a subkilometer-sized nucleus. The spine tail-the product of the terminal fragmentation-was a synchronic feature, whose brightest part contained submillimeter-sized dust grains, released at velocities of up to 30 m s{sup -1}. The loss of the nuclear condensation prevented an accurate orbital-period determination by traditional techniques. Since the missing nucleus must have been located on the synchrone, whose orientation and sunward tip have been measured, we compute the astrometric positions of this missing nucleus as the coordinates of the points of intersection of the spine tail's axis with the lines of forced orbital-period variation, derived from the orbital solutions based on high-quality preperihelion astrometry from the ground. The resulting orbit gives 698 {+-} 2 yr for the osculating orbital period, showing that C/2011 W3 is the first member of the expected new, 21st-century cluster of bright Kreutz-system sungrazers, whose existence was predicted by these authors in 2007. From the spine tail's evolution, we determine that its measured tip, populated by dust particles 1-2 mm in diameter, receded antisunward from the computed position of the missing nucleus. The bizarre appearance of the comet's dust tail in images taken only hours after perihelion with the coronagraphs on board the SOHO and STEREO spacecraft is readily understood. The disconnection of the comet's head from the tail released before perihelion and an apparent activity attenuation near perihelion have a common cause-sublimation of all dust at heliocentric distances smaller than about 1.8 solar radii. The tail's brightness is strongly affected by forward scattering of sunlight by dust. From an initially broad range of particle sizes, the grains that were imaged the longest had a radiation-pressure parameter {beta} {approx_equal} 0.6, diagnostic of submicron-sized silicate grains and consistent with the existence of the dust-free zone around the Sun. The role and place of C/2011 W3 in the hierarchy of the Kreutz system and its genealogy via a 14th-century parent suggest that it is indirectly related to the celebrated sungrazer X/1106 C1, which, just as the first-generation parent of C/2011 W3, split from a common predecessor during the previous return to perihelion.

Sekanina, Zdenek; Chodas, Paul W., E-mail: Zdenek.Sekanina@jpl.nasa.gov, E-mail: Paul.W.Chodas@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)

2012-10-01

381

Orbit Design of Earth-Observation Satellite  

NASA Astrophysics Data System (ADS)

The purpose of this study is to design a reliable orbit for a medium-resolution scientific satellite to observe Earth for developmental issues such as water resources, agricultural, and industrial. To meet this objective this study firstly, defines the mission, secondly, determines mission constraints, thirdly, design the attitude and orbit control system. As for the observation requirements, and the revisit time are provided as a function of the orbital parameters. Initial orbital parameters are obtained by optimal analysis between observation characteristics and attitude and orbit maintenance costs. Long term station-keeping strategies will be provided for the proposed solutions. Impulsive control will be investigated to provide a reliable and affordable attitude and orbit control system.

Owis, Ashraf

382

On the determination of the last stable orbit for circular general relativistic binaries at the third post-Newtonian approximation  

E-print Network

We discuss the analytical determination of the location of the Last Stable Orbit (LSO) in circular general relativistic orbits of two point masses. We use several different ``resummation methods'' (including new ones) based on the consideration of gauge-invariant functions, and compare the results they give at the third post-Newtonian (3PN) approximation of general relativity. Our treatment is based on the 3PN Hamiltonian of Jaranowski and Sch\\"afer. One of the new methods we introduce is based on the consideration of the (invariant) function linking the angular momentum and the angular frequency. We also generalize the ``effective one-body'' approach of Buonanno and Damour by introducing a non-minimal (i.e. ``non-geodesic'') effective dynamics at the 3PN level. We find that the location of the LSO sensitively depends on the (currently unknown) value of the dimensionless quantity $\\oms$ which parametrizes a certain regularization ambiguity of the 3PN dynamics. We find, however, that all the analytical methods we use numerically agree between themselves if the value of this parameter is $\\oms\\simeq-9$. This suggests that the correct value of $\\oms$ is near -9 (the precise value $\\oms^*\\equiv-{47/3}+{41/64}\\pi^2=-9.3439...$ seems to play a special role). If this is the case, we then show how to further improve the analytical determination of various LSO quantities by using a ``Shanks'' transformation to accelerate the convergence of the successive (already resummed) PN estimates.

Thibault Damour; Piotr Jaranowski; Gerhard Schaefer

2000-05-10

383

42 CFR 476.94 - Notice of QIO initial denial determination and changes as a result of a DRG validation.  

Code of Federal Regulations, 2011 CFR

...initial denial determination and changes as a result of a DRG validation. 476.94 Section...initial denial determination and changes as a result of a DRG validation. (a) Notice of...determination. (b) Notice of changes as a result of a DRG validation. The QIO...

2011-10-01

384

42 CFR 476.94 - Notice of QIO initial denial determination and changes as a result of a DRG validation.  

Code of Federal Regulations, 2010 CFR

...initial denial determination and changes as a result of a DRG validation. 476.94 Section...initial denial determination and changes as a result of a DRG validation. (a) Notice of...determination. (b) Notice of changes as a result of a DRG validation. The QIO...

2010-10-01

385

Asthma Severity According to Global Initiative for Asthma and Its Determinants: An International Study  

Microsoft Academic Search

Background: The identification of the factors associated with severe asthma may shed some light on its etiology and on the mechanisms of its development. We aimed to describe asthma severity using the Global Initiative for Asthma (GINA) classification and to investigate its determinants in a cross-sectional, population-based sample in Europe. Methods: In the European Community Respiratory Health Survey II (1999–2002),

Lucia Cazzoletti; Alessandro Marcon; Angelo Corsico; Christer Janson; Deborah Jarvis; Isabelle Pin; Simone Accordini; Massimiliano Bugiani; Isa Cerveri; David Gislason; Amund Gulsvik; Roberto de Marco

2010-01-01

386

Gravity and Orbits: Orbits  

NSDL National Science Digital Library

This Science Object is the third of three Science Objects in the Gravity and Orbits SciPack. It provides an understanding of how gravitational forces influence the motion of an object in orbit. When a force acts toward a single center, an object's forward motion and its motion toward that center can combine to create a curved path around the center. Gravity governs the motion of all objects in the solar system. The Sun's gravitational pull holds the Earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them. Learning Outcomes:? Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.? Explain how an object orbits a planet in terms of trajectories and free fall.? Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.

National Science Teachers Association (NSTA)

2006-11-01

387

The Determination and Long Term Integration of the Orbits of Caliban and Sycorax. 1.6  

NASA Technical Reports Server (NTRS)

The first 2 irregular satellites of Uranus, Caliban and Sycorax, were discovered in late 1997. Subsequently, pre-discovery observations of both satellites were found on plates taken by D. Cruikshank in June of 1984. Recently, P. Nicholson, D. Tholen, and W. Offutt provided observations which they made in late 1998 at Palomar Mountain, Mauna Kea, and Cloudcroft, respectively. I fit a numerical integration perturbed by the Sun, Jupiter, Saturn, and Neptune to the set of available observations. For the 47 observations of Caliban the respective rms values of the Delta alpha (cos delta) and Delta delta residuals axe 0".60 and 0".32, and for the 103 observations of Sycorax the analogous values are 0".57 and 0".59. I extended the integration to span a 6000 year period and computed osculating orbital elements at yearly intervals. An included table contains the mean values of the elements over the 6000 years, the sidereal period, and the precession periods of the argument of periapsis and longitude of the ascending node. The osculating elements (except for a) exhibit a significant long period oscillation with a period roughly half that of the argument of periapsis.

Jacobson, R. A.

1999-01-01

388

Precise Orbit Determination for GEOSAT Follow-On Using Satellite Laser Ranging Data and Intermission Altimeter Crossovers  

NASA Technical Reports Server (NTRS)

The U.S. Navy's GEOSAT Follow-On Spacecraft was launched on February 10, 1998 and the primary objective of the mission was to map the oceans using a radar altimeter. Following an extensive set of calibration campaigns in 1999 and 2000, the US Navy formally accepted delivery of the satellite on November 29, 2000. The spacecraft is tracked by satellite laser ranging (SLR) and Doppler (Tranet-style) beacons. Although a limited amount of GPS data were obtained, the primary mode of tracking remains satellite laser ranging. In this paper, we report on progress in orbit determination for GFO using GFO/GFO and TOPEX/GFO altimeter crossovers. We have tuned the nonconservative force model for GFO and the gravity model using SLR, Doppler and altimeter crossover data spanning over one year. Preliminary results show that the predicted radial orbit error from the gravity field covariance to 70x70 on GEOSAT was reduced from 2.6 cm in EGM96 to 1.9 cm with the addition of only five months of the GFO SLR and GFO/GFO crossover data. Further progress is possible with the addition of more data, particularly the TOPEX/GFO crossovers. We will evaluate the tuned GFO gravity model (a derivative of EGM96) using altimeter data from the GEOSAT mission. In January 2000, a limited quantity of GPS data were obtained. We will use these GPS data in conjunction with the SLR and altimeter crossover data obtained over the same time span to compute quasi-reduced dynamic orbits which will also aid in the evaluation of the tuned GFO geopotential model.

Lemoine, F. G.; Rowlands, D. D.; Luthcke, S. B.; Zelensky, N. P.; Chinn, D. S.; Pavlis, D. E.; Marr, G. C.

2001-01-01

389

Determination of the initial beam parameters in Monte Carlo linac simulation  

SciTech Connect

For Monte Carlo linac simulations and patient dose calculations, it is important to accurately determine the phase space parameters of the initial electron beam incident on the target. These parameters, such as mean energy and radial intensity distribution, have traditionally been determined by matching the calculated dose distributions with the measured dose distributions through a trial and error process. This process is very time consuming and requires a lot of Monte Carlo simulation experience and computational resources. In this paper, we propose an easy, efficient, and accurate method for the determination of the initial beam parameters. We hypothesize that (1) for one type of linacs, the geometry and material of major components of the treatment head are the same; the only difference is the phase space parameters of the initial electron beam incident on the target, and (2) most linacs belong to a limited number of linac types. For each type of linacs, Monte Carlo treatment planning system (MC-TPS) vendors simulate the treatment head and calculate the three-dimensional (3D) dose distribution in water phantom for a grid of initial beam energies and radii. The simulation results (phase space files and dose distribution files) are then stored in a data library. When a MC-TPS user tries to model their linac which belongs to the same type, a standard set of measured dose data is submitted and compared with the calculated dose distributions to determine the optimal combination of initial beam energy and radius. We have applied this method to the 6 MV beam of a Varian 21EX linac. The linac was simulated using EGSNRC/BEAM code and the dose in water phantom was calculated using EGSNRC/DOSXYZ. We have also studied issues related to the proposed method. Several common cost functions were tested for comparing measured and calculated dose distributions, including {chi}{sup 2}, mean absolute error, dose difference at the penumbra edge point, slope of the dose difference of the lateral profile, and the newly proposed {kappa}{sub {alpha}} factor (defined as the fraction of the voxels with absolute dose difference less than {alpha}%). It was found that the use of the slope of the lateral profile difference or the difference of the penumbra edge points may lead to inaccurate determination of the initial beam parameters. We also found that in general the cost function value is very sensitive to the simulation statistical uncertainty, and there is a tradeoff between uncertainty and specificity. Due to the existence of statistical uncertainty in simulated dose distributions, it is practically impossible to determine the best energy/radius combination; we have to accept a group of energy/radius combinations. We have also investigated the minimum required data set for accurate determination of the initial beam parameters. We found that the percent depth dose curves along or only a lateral profile at certain depth for a large field size is not sufficient and the minimum data set should include several lateral profiles at various depths as well as the central axis percent depth dose curve for a large field size.

Aljarrah, Khaled; Sharp, Greg C.; Neicu, Toni; Jiang, Steve B. [Department of Physics, University of Massachusetts Lowell, Lowell, Massachusetts (United States); Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts (United States)

2006-04-15

390

Orbital evolution of a test particle around a black hole: Indirect determination of the self force in the post Newtonian approximation  

E-print Network

Comparing the corrections to Kepler's law with orbital evolution under a self force, we extract the finite, already regularized part of the latter in a specific gauge. We apply this method to a quasi-circular orbit around a Schwarzschild black hole of an extreme mass ratio binary, and determine the first- and second-order conservative gravitational self force in a post Newtonian expansion. We use these results in the construction of the gravitational waveform, and revisit the question of the relative contribution of the self force and spin-orbit coupling.

Lior M. Burko

2006-04-06

391

The orbit of asteroid (99942) Apophis as determined from optical and radar observations  

NASA Astrophysics Data System (ADS)

The results of improving the orbit accuracy for the asteroid Apophis and the circumstances of its approach to Earth in 2029 are described. Gravitational perturbations from all of the major planets and Pluto, Ceres, Pallas, and Vesta are taken into account in the equations of motion of the asteroid. Relativistic perturbations from the Sun and perturbations due to the oblateness of the Sun and Earth and due to the light pressure are also included in the model. Perturbations from the Earth and Moon are considered separately. The coordinates of the perturbing bodies are calculated using DE405. The phase correction and the gravitational deflection of light are taken into account. The numerical integration of the equations of motion and equations in variations is performed by the 15th-order Everhart method. The error of the numerical integration over the 2005 2029 interval, estimated using forward and backward computations, is not more than 3 × 10-11 AU. Improved coordinates and velocities at epoch JD2454200.5 (April 10, 2007) were obtained applying the weighted leastsquares fit. For the period from March 15, 2004, to August 16, 2006, 989 optical and 7 radar observations were used. The resulting system represents the optical observations with an error of 0.37 (66 conditional equations were rejected). The residuals of the radar observations are an order, or more, smaller than their errors. The system of Apophis’ elements and the estimates of their precision obtained in this study are in perfect agreement with the results published by other authors. The minimum Apophis-Earth distance is about 38 200 km on April 13, 2029. This estimate agrees to within 20 km with those calculated based on other published systems of elements. The effect of some model components on the minimum distance is estimated.

Vinogradova, T. A.; Kochetova, O. M.; Chernetenko, Yu. A.; Shor, V. A.; Yagudina, E. I.

2008-08-01

392

Experimentally determined weight matrix definitions of the initiator and TBP binding site elements of promoters.  

PubMed

The basal elements of class II promoters are: (i) a-30 region, recognized by TATA binding protein (TBP); (ii) an initiator (Inr) surrounding the start site for transcription; (iii) frequently a downstream (+10 to +35) element. To determine the sequences that specify an Inr, we performed a saturation mutagenesis of the Inr of the SV40 major late promoter (SV40-MLP). The transcriptional activity of each mutant was determined both in vivo and in vitro. An excellent correlation between transcriptional activity and closeness of fit to the optimal Inr sequence, 5'-CAG/TT-3', was found to exist both in vivo and in vitro. Employing a neural network technique we generated from these data a weight matrix definition of an Inr that can be used to predict the activity of a given sequence as an Inr. Using saturation mutagenesis data of TBP binding sites we likewise generated a weight matrix definition of the -30 region element. We conclude the following: (i) Inrs are defined by the nucleotides immediately surrounding the transcriptional start site; (ii) most, if not all, Inrs are recognized by the same general transcription factor(s). We propose that the mechanism of transcription initiation is fundamentally conserved, with the formation of pre-initiation complexes involving the concurrent binding of general transcription factors to the -30, Inr and, possibly, downstream elements of class II promoters. PMID:8628688

Kraus, R J; Murray, E E; Wiley, S R; Zink, N M; Loritz, K; Gelembiuk, G W; Mertz, J E

1996-04-15

393

Determination of secondary structure in the initiation region of ovalbumin mRNA.  

PubMed Central

We have analyzed the secondary structure in the region surrounding the initiation codons of both cellular and synthetic versions of ovalbumin mRNA. RNase V1 cleavage sites and structure-dependent, chemically modified bases in cellular ovalbumin mRNA were determined by reverse transcription of hen poly A(+) RNA using ovalbumin-specific, synthetic DNA primers. These results indicate an extensive region of unpaired nucleotides preceding the initiation codon and a region of base-paired nucleotides including and following the initiation codon. A synthetic ovalbumin mRNA (SP65.OV) was prepared by run-off transcription of a cloned ovalbumin cDNA (pSP65.OV). Identical regions of hen ovalbumin and SP65.OV mRNAs gave identical patterns of structure-dependent base modifications. A computer program for determining RNA secondary structure was used to find a 5'-region structure for ovalbumin mRNA that is consistent with our data. Images PMID:3205742

Liarakos, C D; Maddox, R P; Hilscher, K A; Bishop, J R; McGuire, D K; Kopper, R A

1988-01-01

394

The NOVA-2 postlaunch orbit adjustment process  

NASA Astrophysics Data System (ADS)

The NOVA-2 satellite was the last of three `drag free' spacecraft to be placed into the Transit Navigation Systems's constellation of satellites. After its launch from Vandenburg Air Force Base into an initial 510 x 170 nmi near poar orbit, an intensive two-week operations schedule was implemented to : raise the orbit approximately 450 nmi to within .015 sec of desired period, trim eccentricity to within .003, trim inclination to within .006 degrees of requirement, freeze the phase of the spacecraft in orbit relative to the other two `drag free' satellites, dump extra fuel by deliberately fual wasting burns, and transition the spacecraft from a slow spin mode to gravity gradient. This paper will briefly discuss the concept of a `drag free' satellite, the selection of the orbit plane in the constellations, and the derivation of the required final orbit parameters. The paper will also discuss peripheral support needed to assist the OATS (Orbit Adjust and Transfer System) ground software, including attitude determination and maneuvers, orbit determination, and orbit prediction through the burns. However, the specific focus of this paper is on the design and execution of the nine OATS burns that accomplished the orbital maneuvers.

Heyler, Gene A.

395

A study to explore the use of orbital remote sensing to determine native arid plant distribution  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. A theory has been developed of a method for determining the reflectivities of natural areas from ERTS-1 data. This method requires the following measurements: (1) ground truth reflectivity data from two different calibration areas; (2) radiance data from ERTS-1 MSS imagery for the same two calibration areas; and (3) radiance data from ERTS-1 MSS imagery for the area(s) in which reflectivity is to be determined. The method takes into account sun angle effects and atmospheric effects on the radiance seen by the space sensor. If certain assumptions are made, the ground truth data collection need not be simultaneous with the ERTS-1 overflight. The method allows the calculation of a conversion factor for converting ERTS-1 MSS radiance measurements of a given overflight to reflectivity values. This conversion factor can be used to determine the reflectivity of any area in the general vicinity of the calibration areas which has a relatively similar overlying atmosphere. This method, or some modification of it, may be useful in ERTS investigations which require the determination of spectral signatures of areas from spacecraft data.

Mcginnies, W. G. (principal investigator); Haase, E. F.; Musick, H. B. (compiler)

1973-01-01

396

Techniques for the determination of mass properties of earth-to-orbit transportation systems  

NASA Technical Reports Server (NTRS)

One estimating technique involves trending whereby projections of overall mass properties of vehicles are determined with few inputs. The second technique involves trending of individual subsystems using equations of the form KXN to the nth power or KX. Some constants and exponentials are provided for sample subsystems. Mass properties are reported in a format recommended by mil spec - 38310.

Macconochie, I. O.; Klich, P. J.

1978-01-01

397

Determining the in-plane orientation of the ground-state orbital of CeCu2Si2.  

PubMed

We have successfully determined the hitherto unknown sign of the B(4)(4) Stevens crystal-field parameter of the tetragonal heavy-fermion compound CeCu(2)Si(2) using vector q-dependent nonresonant inelastic x-ray scattering experiments at the cerium N(4,5) edge. The observed difference between the two different directions, q?[100] and q?[110], is due to the anisotropy of the crystal-field ground state in the (001) plane and is observable only because of the utilization of higher than dipole transitions possible in nonresonant inelastic x-ray scattering. This approach allows us to go beyond the specific limitations of dc magnetic susceptibility, inelastic neutron scattering, and soft x-ray spectroscopy, and provides us with a reliable information about the orbital state of the 4f electrons relevant for the quantitative modeling of the quasiparticles and their interactions in heavy-fermion systems. PMID:23006099

Willers, T; Strigari, F; Hiraoka, N; Cai, Y Q; Haverkort, M W; Tsuei, K-D; Liao, Y F; Seiro, S; Geibel, C; Steglich, F; Tjeng, L H; Severing, A

2012-07-27

398

Second-order p-iterative solution of the Lambert/Gauss problem. [algorithm for efficient orbit determination  

NASA Technical Reports Server (NTRS)

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.

Boltz, F. W.

1984-01-01

399

Small Mercury Relativity Orbiter  

NASA Technical Reports Server (NTRS)

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.

Bender, Peter L.; Vincent, Mark A.

1989-01-01

400

An orbital determination of Triton with the use of a revised pole model  

NASA Astrophysics Data System (ADS)

In this paper, we used the 3108 Earth-based astrometric observations from the Natural Satellite Data Center over more than 30 yr time span from 1975 to 2006 for determining the epoch state vectors of the Neptunian largest satellite Triton. These observations almost contain all modern photo and CCD observations available. In integrating perturbation equation, the barycentric frame of Neptune-Triton system is adopted, and in considering the oblateness perturbation due to Neptune, a revised pole model describing the precession of the Neptune's pole is used in our calculation.

Zhang, H. Y.; Shen, K. X.; Dourneau, G.; Harper, D.; Qiao, R. C.; Xi, X. J.; Cheng, X.; Yan, D.; Li, S. N.; Wang, S. H.

2014-02-01

401

Determination of burst initiation location and tear propagation velocity during air burst testing of latex condoms  

NASA Astrophysics Data System (ADS)

The stress testing of latex condoms by an air burst procedure has been slow in gaining industry acceptance because questions have been raised regarding the influence of the test apparatus on the likelihood of breakage occurring where the condom is attached to the inflation device. It was desired to locate the areas at which the condoms tend to burst and thus corroborate or disprove these claims. Several factors associated with the bursting condom demanded the use of special instrumentation to detect arid study the burst initiation process. Microsecond duration electronic flashes were used for the initial stages of the investigation. Although the absolute point of initiation of a given burst could not be photographed, these high speed studies tend to indicate that the most likely place for high quality condoms to break is not where they are attached to the inflation device but at an intermediate area between the base and the tip of the condom. In addition, tear propagation characteristics and velocities were determined with a delayed-flash technique, a double-slit strip method and a rotating drum framing camera.

Davidhazy, Andrew

1991-04-01

402

Detector positioning for the initial subcriticality level determination in accelerator-driven systems  

SciTech Connect

Within the GUINEVERE project (Generation of Uninterrupted Intense Neutrons at the lead Venus Reactor) carried out at SCK-CEN in Mol, the continuous deuteron accelerator GENEPI-3C was coupled to the VENUS-F fast simulated lead-cooled reactor. Today the FREYA project (Fast Reactor Experiments for hYbrid Applications) is ongoing to study the neutronic behavior of this Accelerator Driven System (ADS) during different phases of operation. In particular the set-up of a monitoring system for the subcriticality of an ADS is envisaged to guarantee safe operation of the installation. The methodology for subcriticality monitoring in ADS takes into account the determination of the initial subcriticality level, the monitoring of reactivity variations, and interim cross-checking. At start-up, the Pulsed Neutron Source (PNS) technique is envisaged to determine the initial subcriticality level. Thanks to its reference critical state, the PNS technique can be validated on the VENUS-F core. A detector positioning methodology for the PNS technique is set up in this paper for the subcritical VENUS-F core, based on the reduction of higher harmonics in a static evaluation of the Sjoestrand area method. A first case study is provided on the VENUS-F core. This method can be generalised in order to create general rules for detector positions and types for full-scale ADS. (authors)

Uyttenhove, W.; Van Den Eynde, G.; Baeten, P.; Kochetkov, A.; Vittiglio, G.; Wagemans, J. [SCKCEN, Belgian Nuclear Research Centre, Boeretang 200, BE-2400 Mol (Belgium); Lathouwers, D.; Kloosterman, J. L.; Van Der Hagen, T. J. H. H.; Wols, F. [Delft Univ. of Technology, Mekelweg 15, NL-2629 JB Delft (Netherlands); Billebaud, A.; Chabod, S.; Thybault, H. E. [LPSC-CNRS-IN2P3/UJF/INPG, 53, Avenue des Martyrs, 38026 Grenoble Cedex (France); Lecouey, J. L.; Ban, G.; Lecolley, F. R.; Marie, N.; Steckmeyer, J. C. [LPC Caen, ENSICAEN/Unicersit de Caen/CNRS-IN2P3, Caen (France); Dessagne, P.; Kerveno, M. [IPHC-DRS/UdS/CNRS-IN2P3, Strasbourg (France); Mellier, F. [CEA/DEN/DER/SPEX/LPE, Cadarache 13108 Saint-Paul-les-Durance (France)

2012-07-01

403

Asteroids in Retrograde Orbits: Interesting Cases  

NASA Astrophysics Data System (ADS)

We present the most interesting examples of the orbital evolution of asteroids in retrograde orbits (i > 90°). First, we used the latest observational data to determine nominal and averaged orbital elements of these objects. Next, the equations of motion of these asteroids were integrated backward 1 My, taking into account the propagation of observational errors. We used so-called 'cloning' procedure to reproduce the reliability of initial data. We obtained some possible scenarios of the orbit inversion in the past, what is often caused by the long-term influence of outer planets. For two most interesting cases (Apollo and Amor type) we did additional calculations: 100 My in the future. Additionally, we investigated the potential influence of Yarkovski/YORP effects on the long-time orbital evolution.

Kankiewicz, Pawe?; W?odarczyk, Ireneusz

2014-12-01

404

A new method of preliminary orbit determination from three or more observations on a short arc. (Russian Title: ????? ????? ??????????? ??????????????? ?????? ?? ???? ? ????? ??????????? ?? ???????? ????)  

NASA Astrophysics Data System (ADS)

A new method is suggested for finding the preliminary orbit of a small celestial body from its three or more pairs of angular measurements at three times. The method is based on using the approach that we previously developed for constructing the intermediate orbit from minimal number of observations. This intermediate orbit allows for most of the perturbations in the motion of the body under study. The method proposed uses the Herget's algorithmic scheme that makes it possible to involve additional observations as well. The methodical error of orbit computation by the proposed method is two orders smaller than the corresponding error of the commonly used approach based on the construction of the unperturbed Keplerian orbit. The new method is especially efficient if applied to high-accuracy observational data covering short orbital arcs.

Shefer, V. A.

2011-07-01

405

Preliminary Orbit Determination System (PODS) for Tracking and Data Relay Satellite System (TDRSS)-tracked target Spacecraft using the homotopy continuation method  

NASA Technical Reports Server (NTRS)

The Preliminary Orbit Determination System (PODS) provides early orbit determination capability in the Trajectory Computation and Orbital Products System (TCOPS) for a Tracking and Data Relay Satellite System (TDRSS)-tracked spacecraft. PODS computes a set of orbit states from an a priori estimate and six tracking measurements, consisting of any combination of TDRSS range and Doppler tracking measurements. PODS uses the homotopy continuation method to solve a set of nonlinear equations, and it is particularly effective for the case when the a priori estimate is not well known. Since range and Doppler measurements produce multiple states in PODS, a screening technique selects the desired state. PODS is executed in the TCOPS environment and can directly access all operational data sets. At the completion of the preliminary orbit determination, the PODS-generated state, along with additional tracking measurements, can be directly input to the differential correction (DC) process to generate an improved state. To validate the computational and operational capabilities of PODS, tests were performed using simulated TDRSS tracking measurements for the Cosmic Background Explorer (COBE) satellite and using real TDRSS measurements for the Earth Radiation Budget Satellite (ERBS) and the Solar Mesosphere Explorer (SME) spacecraft. The effects of various measurement combinations, varying arc lengths, and levels of degradation of the a priori state vector on the PODS solutions were considered.

Kirschner, S. M.; Samii, M. V.; Broaddus, S. R.; Doll, C. E.

1988-01-01

406

Initial Motion and Bedload Transport Distance Determined by Particle Tracking in a Large Regulated River  

NASA Astrophysics Data System (ADS)

Reservoir releases on large regulated rivers are increasingly being used to rejuvenate riverine habitat downstream of dams. Determining the effective flow level is complicated by the trade-off between mobilizing bed particles and retaining coarse sediment in rivers with low sediment supply. This study determined mobilization and transport distance of bed particles using motion-sensing radio transmitting particles that approximated the reach-average D84 grain size. The distribution of shear stress at initial motion varied substantially between flood events, and suggests that the sequence of flood events and the history of underthreshold flows may be an important determinant of bed strength and thus particle mobility. In addition, particle activity was greatest on the rising limb of each flood and was maximized at near bank-full flow. Travel distances did not vary between floods when scaled by transport event duration, and a negative exponential distribution was a good fit to the data. Results of this study provide important insight into individual particle movement, which can be used to inform flow releases and understand the effects of flood magnitude on particle mobility and transport.

May, C. L.; Smith Pryor, B.; Lisle, T. E.

2012-12-01

407

42 CFR 476.85 - Conclusive effect of QIO initial denial determinations and changes as a result of DRG validations.  

Code of Federal Regulations, 2010 CFR

...denial determinations and changes as a result of DRG validations. 476.85 Section...denial determinations and changes as a result of DRG validations. A QIO initial denial determination or change as a result of DRG validation is final and...

2010-10-01

408

45 CFR 1705.8 - Appeal of an initial adverse agency determination on correction or amendment of the record.  

Code of Federal Regulations, 2010 CFR

...Section 1705.8 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL COMMISSION ON LIBRARIES AND INFORMATION SCIENCE PRIVACY REGULATIONS § 1705.8 Appeal of an initial adverse agency determination on...

2010-10-01

409

45 CFR 1705.8 - Appeal of an initial adverse agency determination on correction or amendment of the record.  

Code of Federal Regulations, 2011 CFR

...Section 1705.8 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL COMMISSION ON LIBRARIES AND INFORMATION SCIENCE PRIVACY REGULATIONS § 1705.8 Appeal of an initial adverse agency determination on...

2011-10-01

410

45 CFR 1705.8 - Appeal of an initial adverse agency determination on correction or amendment of the record.  

Code of Federal Regulations, 2013 CFR

... Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL COMMISSION ON LIBRARIES AND INFORMATION SCIENCE PRIVACY REGULATIONS § 1705.8 Appeal of an initial adverse agency determination on correction or...

2013-10-01

411

20 CFR 418.1230 - What is the effective date of an income-related monthly adjustment amount initial determination...  

Code of Federal Regulations, 2010 CFR

...1230 Employees' Benefits SOCIAL SECURITY ADMINISTRATION MEDICARE...reduced as a result of a major life-changing event, our initial determination...a result of one or more of the events described in §...

2010-04-01

412

13 CFR 121.1001 - Who may initiate a size protest or request a formal size determination?  

Code of Federal Regulations, 2012 CFR

...Other interested parties. (4) For SBA's Small Business Innovation Research (SBIR) Program, the following entities may protest...will be used to determine size, and SBA will initiate the process to remove from the database the small business...

2012-01-01

413

13 CFR 121.1001 - Who may initiate a size protest or request a formal size determination?  

Code of Federal Regulations, 2011 CFR

...Other interested parties. (4) For SBA's Small Business Innovation Research (SBIR) Program, the following entities may protest...will be used to determine size, and SBA will initiate the process to remove from the database the small business...

2011-01-01

414

13 CFR 121.1001 - Who may initiate a size protest or request a formal size determination?  

...Other interested parties. (4) For SBA's Small Business Innovation Research (SBIR) program and Small Business Technology Transfer...will be used to determine size, and SBA will initiate the process to remove from the database the small business...

2014-01-01

415

13 CFR 121.1001 - Who may initiate a size protest or request a formal size determination?  

Code of Federal Regulations, 2013 CFR

... (4) For SBA's Small Business Innovation Research (SBIR) Program, the following...determine size, and SBA will initiate the process to remove from the database the small... (4) For SBA's Small Business Innovation Research (SBIR) program and Small...

2013-01-01

416

49 CFR 1515.5 - Appeal of Initial Determination of Threat Assessment based on criminal conviction, immigration...  

Code of Federal Regulations, 2010 CFR

...based on criminal conviction, immigration status, or mental capacity. (a) Scope. This section applies to applicants appealing from an Initial Determination of Threat Assessment that was based on one or more of the following: (1) TSA has...

2010-10-01

417

49 CFR 1515.5 - Appeal of Initial Determination of Threat Assessment based on criminal conviction, immigration...  

Code of Federal Regulations, 2011 CFR

...based on criminal conviction, immigration status, or mental capacity. (a) Scope. This section applies to applicants appealing from an Initial Determination of Threat Assessment that was based on one or more of the following: (1) TSA has...

2011-10-01

418

49 CFR 7.35 - When and how is the twenty day time limit for rendering an initial determination tolled?  

...2014-10-01 false When and how is the twenty day time limit for rendering an initial determination...Transportation PUBLIC AVAILABILITY OF INFORMATION Time Limits § 7.35 When and how is the twenty day time limit for rendering an initial...

2014-10-01

419

Phase identity of the maize leaf is determined after leaf initiation  

PubMed Central

The vegetative development of the maize shoot can be divided into juvenile and adult phases based on the types of leaves produced at different times in shoot development. Models for the regulation of phase change make explicit predictions about when the identity of these types of leaves is determined. To test these models, we examined the timing of leaf type determination in maize. Clones induced in transition leaf primordia demonstrated that the juvenile and adult regions of these leaves do not become clonally distinct until after the primordium is 700 ?m in length, implying that these cell fates were undetermined at this stage of leaf development. Adult shoot apices were cultured in vitro to induce rejuvenation. We found that leaf primordia as large as 3 mm in length can be at least partially rejuvenated by this treatment, and the location of rejuvenated tissue is correlated with the maturation pattern of the leaf. The amount and distribution of juvenile tissue in rejuvenated leaves suggests that rejuvenation occurs nearly simultaneously in all leaf primordia. In vitro culture rejuvenated existing leaf primordia and the P0 primordium, but did not change the identity of subsequent primordia or the total number of leaves produced by the shoot. This result suggests that leaf identity can be regulated independently of the identity of the shoot apical meristem, and it implies that vegetative phase change is not initiated by a change in the identity of the shoot apical meristem. PMID:10973480

Orkwiszewski, Joseph A. J.; Poethig, R. Scott

2000-01-01

420

Theoretical determination of anisotropic thermal conductivity for initially defect-free and defective TATB single crystals  

NASA Astrophysics Data System (ADS)

The anisotropic thermal conductivity was determined for initially defect-free and defective crystals of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), a material that exhibits a graphitic-like packing structure with stacked single-molecule-thick layers, using the reverse non-equilibrium molecular dynamics method and an established TATB molecular dynamics force field. Thermal conduction in TATB is predicted to be substantially higher and more anisotropic than in other related organic molecular explosives, with conduction along directions nominally in the plane of the molecular layers at least 68% greater than conduction along the direction exactly perpendicular to the layers. Finite-size effects along the conduction directions were assessed. The conductivity along directions nominally in the plane of the molecular layers was found to be insensitive to the supercell length along the conduction direction—a result commensurate with the estimated phonon mean free path, ˜6 Å. A small decrease in the conductivity normal to the layers was found for longer supercells and is likely due to increased phonon scattering as a result of dynamic structural transitions in the crystal. The thermal conductivity of TATB crystals containing vacancy defects was also determined and the variation of conductivity with crystal density was found to be both linear and anisotropic, with the introduction of vacancy defects leading to a greater percentage reduction in conduction for the direction perpendicular to the molecular layers.

Kroonblawd, Matthew P.; Sewell, Thomas D.

2014-11-01

421

Use of nose cap and fuselage pressure orifices for determination of air data for space shuttle orbiter below supersonic speeds  

NASA Technical Reports Server (NTRS)

Wind tunnel pressure measurements were acquired from orifices on a 0.1 scale forebody model of the space shuttle orbiter that were arranged in a preliminary configuration of the shuttle entry air data system (SEADS). Pressures from those and auxiliary orifices were evaluated for their ability to provide air data at subsonic and transonic speeds. The orifices were on the vehicle's nose cap and on the sides of the forebody forward of the cabin. The investigation covered a Mach number range of 0.25 to 1.40 and an angle of attack range from 4 deg. to 18 deg. An air data system consisting of nose cap and forebody fuselage orifices constitutes a complete and accurate air data system at subsonic and transonic speeds. For Mach numbers less than 0.80 orifices confined to the nose cap can be used as a complete and accurate air data system. Air data systems that use only flush pressure orifices can be used to determine basic air data on other aircraft at subsonic and transonic speeds.

Larson, T. J.; Siemers, P. M., III

1980-01-01

422

A comparison of operationally determined atmospheric densities from satellite orbit solutions and the exospheric temperature from the Jacchia-Roberts model  

NASA Technical Reports Server (NTRS)

Operational orbit determination by the Flight Dynamics Division at the Goddard Space Flight Center has yielded a data base of orbit solutions covering the onset of solar cycle 22. Solutions for nine satellites include an estimated drag adjustment parameter (rho sub 1) determined by the Goddard Trajectory Determination System (GTDS). The rho sub 1 is used to evaluate correlations between density variations and changes in the following: 10.7-centimeter wavelength solar flux (F sub 10.7), the geomagnetic index A sub p, and two exospheric temperatures (T sub c and T sub infinity) adapted from the Jacchia-Roberts atmospheric density model in GTDS. T sub c depends on the daily and 81-day centered mean F sub 10.7; T sub infinity depends on T sub c and the geomagnetic index K sub p values. The highest correlations are between density and T sub infinity. Correlations with T sub c and F sub 10.7 are lower by 9 and 10 percent, respectively. For most cases, correlations with A sub p are considerably lower; however, significant correlations with A sub p were found for some high-inclination, moderate-altitude orbits. Results from this analysis enhance the understanding of the drag model and the accommodation of atmospheric density variations in the operational orbit determination support. The degree of correlation demonstrates the sensitivity of the orbit determination process to drag variations and to the input parameters that characterize aspects of the atmospheric density model. To this extent, the degree of correlation provides a measure of performance for methods of selecting or modeling the thermospheric densities using the solar F sub 10.7 and geomagnetic data as input to the process.

Ward, D. T.; Smith, E. A.; Phenneger, M. C.

1990-01-01

423

Translation initiation rate determines the impact of ribosome stalling on bacterial protein synthesis.  

PubMed

Ribosome stalling during translation can be caused by a number of characterized mechanisms. However, the impact of elongation stalls on protein levels is variable, and the reasons for this are often unclear. To investigate this relationship, we examined the bacterial translation elongation factor P (EF-P), which plays a critical role in rescuing ribosomes stalled at specific amino acid sequences including polyproline motifs. In previous proteomic analyses of both Salmonella and Escherichia coli efp mutants, it was evident that not all proteins containing a polyproline motif were dependent on EF-P for efficient expression in vivo. The ?- and ?-subunits of ATP synthase, AtpA and AtpD, are translated from the same mRNA transcript, and both contain a PPG motif; however, proteomic analysis revealed that AtpD levels are strongly dependent on EF-P, whereas AtpA levels are independent of EF-P. Using these model proteins, we systematically determined that EF-P dependence is strongly influenced by elements in the 5'-untranslated region of the mRNA. By mutating either the Shine-Dalgarno sequence or the start codon, we find that EF-P dependence correlates directly with the rate of translation initiation where strongly expressed proteins show the greatest dependence on EF-P. Our findings demonstrate that polyproline-induced stalls exert a net effect on protein levels only if they limit translation significantly more than initiation. This model can be generalized to explain why sequences that induce pauses in translation elongation to, for example, facilitate folding do not necessarily exact a penalty on the overall production of the protein. PMID:25148683

Hersch, Steven J; Elgamal, Sara; Katz, Assaf; Ibba, Michael; Navarre, William Wiley

2014-10-10

424

Orbital changes during hypersonic aerocruise  

NASA Technical Reports Server (NTRS)

A novel mathematical approach that allows the analysis of orbital changes occurring during an aerocruise maneuver to be conducted in two distinct stages is presented. In the first stage, the aerodynamic turn is determined using a nondimensional form of the equations of motion that is free of singularities, and the way in which speed, altitude, angle of attack, and thrust direction should be chosen to maximize the aerodynamic turn for a given propellant expenditure is demonstrated. In the second analysis stage, the aerodynamic turn is translated into changes in the orbital elements with respect to the equatorial plane; analytic solutions for the initial arguments of latitude that maximize the change in inclination and in the longitude of the ascending node are given. As the initial inclination decreases toward zero, the optimal location moves from the apex toward the node.

Mease, Kenneth D.; Vinh, Nguyen X.; Lee, Jaemyong

1987-01-01

425

15 CFR 930.38 - Consistency determinations for activities initiated prior to management program approval.  

Code of Federal Regulations, 2010 CFR

...other than development projects initiated prior to management program approval...federal development project decisions described...are made following management program approval and...related to development projects initiated prior...

2010-01-01