Sample records for initial orbit determination

  1. A Comprehensive Comparison Between Angles-Only Initial Orbit Determination Techniques

    E-print Network

    Schaeperkoetter, Andrew Vernon

    2012-02-14

    During the last two centuries many methods have been proposed to solve the angles-only initial orbit determination problem. As this problem continues to be relevant as an initial estimate is needed before high accuracy orbit determination...

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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.

  3. Viking satellite orbit determination

    Microsoft Academic Search

    C. E. Hildebrand; E. J. Christensen; D. H. Boggs; G. H. Born; H. Hokikian; J. F. Jordan; W. B. Howard

    1977-01-01

    During the summer of 1976, the two Viking spacecraft, each consisting of an orbiter-lander combination, were inserted into orbit about Mars. The paper describes the experiences of the Viking Satellite Orbit Determination Team in determining Mars centered ephemerides of the orbiters and positions of the landers from the two-way Doppler and range data, and synthesizes the different phases of the

  4. Interplanetary orbit determination

    Microsoft Academic Search

    K. H. Rourke; N. Jerath; C. H. Acton; W. G. Breckenridge; J. K. Campbell; C. S. Christensen; A. J. Donegan; H. M. Koble; N. A. Mottinger; G. C. Rinker

    1979-01-01

    A general description of the Viking interplanetary orbit determination activity extending from launch to Mars encounter is given. The emphasis is on the technical fundamentals of the problem, basic strategies and data types used, quantitative results, and specific conclusions derived from the inflight experience. Special attention is given to the use of the spacecraft-based optical measurements and their first application

  5. ICESat Precision Orbit Determination

    Microsoft Academic Search

    H. Rim; S. Yoon; C. E. Webb; Y. Kim; B. E. Schutz

    2003-01-01

    Following the successful launch of the Ice, Cloud and land Elevation Satellite (ICESat) on January 13, 2003, 00:45 UTC, the GPS receiver on ICESat was turned on successfully on Jan. 17, 2003. High quality GPS data were collected since then to support Precision Orbit Determination (POD) activities. ICESat carries Geoscience Laser Altimeter System (GLAS) to measure ice-sheet topography and associated

  6. Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis

    NASA Technical Reports Server (NTRS)

    Slojkowski, Steven E.

    2014-01-01

    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.

  7. Orbit Determination of the Lunar Reconnaissance Orbiter

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    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.

  8. Orbit determination in satellite geodesy

    Microsoft Academic Search

    G. Beutler; T. Schildknecht; U. Hugentobler; W. Gurtner

    2003-01-01

    For centuries orbit determination in Celestial Mechanics was a synonym for the determination of six so-called Keplerian elements of the orbit of a minor planet or a comet based on a short series of (three or more) astrometric places observed from one or more observatories on the Earth's surface. With the advent of the space age the problem changed considerably

  9. Spitzer Orbit Determination During In-orbit Checkout Phase

    NASA Technical Reports Server (NTRS)

    Menon, Premkumar R.

    2004-01-01

    The Spitzer Space Telescope was injected into heliocentric orbit on August 25, 2003 to observe and study astrophysical phenomena in the infrared range of frequencies. The initial 60 days was dedicated to Spitzer's "In-Orbit Checkout (IOC)" efforts. During this time high levels of Helium venting were used to cool down the telescope. Attitude control was done using reaction wheels, which in turn were de-saturated using cold gas Nitrogen thrusting. Dense tracking data (nearly continuous) by the Deep Space network (DSN) were used to perform orbit determination and to assess any possible venting imbalance. Only Doppler data were available for navigation. This paper deals with navigation efforts during the IOC phase. It includes Dust Cover Ejection (DCE) monitoring, orbit determination strategy validation and results and assessment of non-gravitational accelerations acting on Spitzer including that due to possible imbalance in Helium venting.

  10. Mars Science Laboratory Orbit Determination

    NASA Technical Reports Server (NTRS)

    Kruizinga, Gerhard L.; Gustafson, Eric D.; Thompson, Paul F.; Jefferson, David C.; Martin-Mur, Tomas J.; Mottinger, Neil A.; Pelletier, Frederic J.; Ryne, Mark S.

    2012-01-01

    This paper describes the orbit determination process, results and filter strategies used by the Mars Science Laboratory Navigation Team during cruise from Earth to Mars. The new atmospheric entry guidance system resulted in an orbit determination paradigm shift during final approach when compared to previous Mars lander missions. The evolving orbit determination filter strategies during cruise are presented. Furthermore, results of calibration activities of dynamical models are presented. The atmospheric entry interface trajectory knowledge was significantly better than the original requirements, which enabled the very precise landing in Gale Crater.

  11. Orbit Determination Issues for Libration Point Orbits

    NASA Technical Reports Server (NTRS)

    Beckman, Mark; Bauer, Frank (Technical Monitor)

    2002-01-01

    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.

  12. Orbit Determination in Satellite Geodesy

    Microsoft Academic Search

    G. Beutler; U. Hugentobler; T. Schildknecht

    2002-01-01

    For centuries orbit determination in Celestial Mechanics was a synonym for the determination of the six Keplerian elements of a minor planet or a comet in the solar system based on a short time series of (three or more) astrometric places observed from one or more observatories on the Earth surface. With the advent of the space age the problem

  13. Precise orbit determination for GRACE

    NASA Astrophysics Data System (ADS)

    Kang, Z.; Nagel, P.; Pastor, R.

    2003-04-01

    The twin, co-orbiting GRACE (Gravity Recovery and Climate Experiment) satellites were launched in March 2002. The primary objective of the GRACE mission is to determine the Earth's gravity field and its temporal variations with unprecedented accuracy. To satisfy this objective as well as other applications (e.g. atmospheric profiling by radio occultation), accurate orbits for GRACE are required. This paper describes several results related to the use of the data collected by the GRACE GPS receiver, high precision accelerometer observations and precise attitude data from star trackers in the application of the GRACE Precise Orbit Determination (POD). The orbit accuracy is assessed using a number of tests, which include analysis of GPS tracking observation residuals, Satellite Laser Ranging (SLR) residuals, K-Band Ranging (KBR) residuals and external orbit comparisons. The results show that an accuracy of better than 5 cm in each direction for GRACE orbits can be obtained. The relative accuracy of the two GRACE satellites is about 1 cm in position and 10 micrometers per second in velocity.

  14. Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis

    NASA Technical Reports Server (NTRS)

    Slojkowski, Steven E.

    2014-01-01

    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.

  15. TDRS orbit determination by radio interferometry

    Microsoft Academic Search

    Michael S. Pavloff

    1994-01-01

    In support of a NASA study on the application of radio interferometry to satellite orbit determination, MITRE developed a simulation tool for assessing interferometry tracking accuracy. The Orbit Determination Accuracy Estimator (ODAE) models the general batch maximum likelihood orbit determination algorithms of the Goddard Trajectory Determination System (GTDS) with the group and phase delay measurements from radio interferometry. ODAE models

  16. Orbit determination for ISRO satellite missions

    Microsoft Academic Search

    Ch. Sreehari Rao; S. K. Sinha

    1985-01-01

    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,

  17. Triple Difference Approach to Low Earth Orbiter Precision Orbit Determination

    Microsoft Academic Search

    Jay-Hyoun Kwon; Dorota A. Grejner-Brzezinska; Jae-Hong Yom; Lee-Dong Cheon

    2003-01-01

    A precise kinematic orbit determination (P-KOD) procedure for Low Earth Orbiter(LEO) using the GPS ion-free triple differenced carrier phases is presented. Because the triple differenced observables provide only relative information, the first epoch's positions of the orbit should be held fixed. Then, both forward and backward filtering was executed to mitigate the effect of biases of the first epoch's position.

  18. Mars Science Laboratory Orbit Determination

    NASA Technical Reports Server (NTRS)

    Kruizinga, Gerhard; Gustafson, Eric; Jefferson, David; Martin-Mur, Tomas; Mottinger, Neil; Pelletier, Fred; Ryne, Mark; Thompson, Paul

    2012-01-01

    Mars Science Laboratory (MSL) Orbit Determination (OD) met all requirements with considerable margin, MSL OD team developed spin signature removal tool and successfully used the tool during cruise, A novel approach was used for the MSL solar radiation pressure model and resulted in a very accurate model during the approach phase, The change in velocity for Attitude Control System (ACS) turns was successfully calibrated and with appropriate scale factor resulted in improved change in velocity prediction for future turns, All Trajectory Correction Maneuvers were successfully reconstructed and execution errors were well below the assumed pre-fight execution errors, The official OD solutions were statistically consistent throughout cruise and for OD solutions with different arc lengths as well, Only EPU-1 was sent to MSL. All other Entry Parameter Updates were waived, EPU-1 solution was only 200 m separated from final trajectory reconstruction in the B-plane

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

    NASA Technical Reports Server (NTRS)

    Welch, Bryan W.

    2007-01-01

    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.

  20. Landsat-4 orbit determination using TDRSS

    NASA Astrophysics Data System (ADS)

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

    1995-08-01

    This paper presents the results of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite (TDRS) 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 provide useful experience for the Earth Observing System (EOS) series of satellites. The filtered and smoothed PFS orbit solutions were compared with the definitive GTDS orbit solutions for Landsat-4; the root-mean-square (RMS) solution difference was 6.6 meters.

  1. Precise Orbit Determination for FORMOSAT-3/COSMIC and Gravity Application

    NASA Astrophysics Data System (ADS)

    Hwang, C.; Tseng, T.; Lin, T.; Fu, C.; Svehla, D.

    2006-12-01

    The orbits of FORMOSAT-3/COSMIC (FC) are determined using the GPS data at a 5-s sampling rate. Both reduced dynamic and kinematic solutions are employed. GPS data from only one antenna is used. The average RMS orbital differences between the reduced dynamic and the kinematic solutions for FM1 to FM6 is 6 cm in each coordinate component. The RMS orbital difference at the overlapped arc is regarded as the internal orbital accuracy. Typical RMS overlapping differences from the reduced and kinematic solutions are about 5 cm. While the reduced dynamic orbit is smooth and free from outliers in most cases, the kinematic solution yields large orbit errors when the satellite attitude values are large or missing. Expected orbital improvement can be achieved by combining GPS data from the two POD antennae. As an external accuracy assessment, we numerically integrate FC orbits using the initial state vectors from the GPS solutions and modeled perturbing forces acting on FC satellites. The RMS differences between GPS-determined and numerically integrated orbits are about 10 cm. For gravity application, we model the centers of mass of the six FC satellites and their time variations by considering the consumption of fuel and motion of solar panels. We will also present experimental determinations of gravity harmonic coefficients using kinematic orbits of FC in different scenarios. The result of a combination solution of gravity harmonic coefficients using FC and GRACE data will also be presented.

  2. Precise Orbit Determination for FORMOSAT-3/COSMIC and Gravity Application

    NASA Astrophysics Data System (ADS)

    Hwang, C.; Tseng, T.; Lin, T.; Fu, C.; Svehla, D.

    2005-05-01

    The orbits of FORMOSAT-3/COSMIC (FC) are determined using the GPS data at a 5-s sampling rate. Both reduced dynamic and kinematic solutions are employed. GPS data from only one antenna is used. The average RMS orbital differences between the reduced dynamic and the kinematic solutions for FM1 to FM6 is 6 cm in each coordinate component. The RMS orbital difference at the overlapped arc is regarded as the internal orbital accuracy. Typical RMS overlapping differences from the reduced and kinematic solutions are about 5 cm. While the reduced dynamic orbit is smooth and free from outliers in most cases, the kinematic solution yields large orbit errors when the satellite attitude values are large or missing. Expected orbital improvement can be achieved by combining GPS data from the two POD antennae. As an external accuracy assessment, we numerically integrate FC orbits using the initial state vectors from the GPS solutions and modeled perturbing forces acting on FC satellites. The RMS differences between GPS-determined and numerically integrated orbits are about 10 cm. For gravity application, we model the centers of mass of the six FC satellites and their time variations by considering the consumption of fuel and motion of solar panels. We will also present experimental determinations of gravity harmonic coefficients using kinematic orbits of FC in different scenarios. The result of a combination solution of gravity harmonic coefficients using FC and GRACE data will also be presented.

  3. Determination of GPS orbits to submeter accuracy

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  4. An approach to autonomous, onboard orbit determination

    NASA Technical Reports Server (NTRS)

    Mease, K. D.; Ryne, M. S.; Wood, L. J.

    1984-01-01

    An orbit determination subsystem that will operate as an integral part of an autonomous, onboard navigation system is presented and analyzed. The navigation system is required to interface solely with the downlink telemetry stream and uplink command stream of an existing class of geostationary satellites. In particular, the orbit will be determined from a set of onboard sensors, which previously were used only for attitude determination. The design of the orbit determination subsystem is described in detail. The rationale behind the choice of each component of the design is given. Finally, the performance of the orbit determination subsystem, under a variety of assumptions, is determined by a combination of numerical simulation and analytical methods.

  5. Landsat4 orbit determination using TDRSS

    Microsoft Academic Search

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

    1995-01-01

    This paper presents the results of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite (TDRS) 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 provide useful experience for the Earth Observing

  6. Zero initial partial derivatives of satellite orbits with respect to force parameters nullify the mathematical basis of the numerical integration method for the determination of standard gravity models from space geodetic measurements

    NASA Astrophysics Data System (ADS)

    Xu, Peiliang

    2015-04-01

    Satellite orbits have been routinely used to produce models of the Earth's gravity field. The numerical integration method is most widely used by almost all major institutions to determine standard gravity models from space geodetic measurements. As a basic component of the method, the partial derivatives of a satellite orbit with respect to the force parameters to be determined, namely, the unknown harmonic coefficients of the gravitational model, have been first computed by setting the initial values of partial derivatives to zero. In this talk, we first design some simple mathematical examples to show that setting the initial values of partial derivatives to zero is generally erroneous mathematically. We then prove that it is prohibited physically. In other words, setting the initial values of partial derivatives to zero violates the physics of motion of celestial bodies. To conclude, the numerical integration method, as is widely used today by major institutions to produce standard satellite gravity models, is simply incorrect mathematically. As a direct consequence, further work is required to confirm whether the numerical integration method can still be used as a mathematical foundation to produce standard satellite gravity models. More details can be found in Xu (2009, Sci China Ser D-Earth Sci, 52, 562-566).

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

    Microsoft Academic Search

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

    1990-01-01

    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

  8. Spacecraft orbit determination using GPS navigation solutions

    Microsoft Academic Search

    Jae-Cheol Yoon; Byoung-Sun Lee; Kyu-Hong Choi

    2000-01-01

    The orbit determination using the GPS navigation solutions for the KOMPSAT-1 spacecraft has been studied. The Cowell method of special perturbation theories was employed to develop a precision orbit propagation, and the perturbations due to geopotential, the gravity of the Sun and the Moon, solid Earth tides, ocean tides, the Earth's dynamic polar motion, solar radiation pressure, and atmospheric drag

  9. Mars Exploration Rover cruise orbit determination

    NASA Technical Reports Server (NTRS)

    Portock, Brian; Baird, Darren; Graat, Eric; McElrath, Tim; Watkins, Michael; Wawrzyniak, Geoff

    2004-01-01

    This paper will describe the results of the orbit determination process for each mission, MER-A and MER-B, during their cruise phase to Mars ending with there final approach to Mars atmospheric entry.

  10. Re-determination of Phoebe's orbit

    NASA Astrophysics Data System (ADS)

    Shen, K. X.; Harper, D.; Qiao, R. C.; Dourneau, G.; Liu, J. R.

    2005-07-01

    In order to improve the orbit of Phoebe, the ninth satellite of the Saturnian system, 101 new observations were made by our research team in 2003, using a CCD detector of large size (2048×2048 pixels) mounted on the 1.56 m astrometric reflector at the Sheshan Station of Shanghai Astronomical Observatory. We fitted a numerical integration of its orbit to all of the collected Earth-based astrometric observations from 1904 to 2003, including the newest precise data sets from Qiao & Tang and from Peng et al. A new set of initial conditions of Phoebe has been obtained, leading to an improved orbit of this satellite.

  11. Advances in SLR orbit determination

    NASA Astrophysics Data System (ADS)

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

    Since LAGEOS II was launched from the space shuttle in October 1992, the Global Tracking Network has provided an extensive set of Satellite Laser Ranging data which supplement the 20 year record of LAGEOS I. The contrasting behavior of small unmodeled along-track accelerations in the orbits of each satellite can be used to help explain the sources of these perturbations. LAGEOS II's 52 degree inclination provides gravity and tidal sensitivity to improve on the advances from LAGEOS I in a shorter time, as LAGEOS II's nodal precession period is about one half that of LAGEOS I's three year period. The combination of data from the two LAGEOS satellites, together with observations from other geodetic satellites, such as ETALON I and II, allows better definition of polar motion and length-of-day, which can now be resolved at sub-daily intervals during periods of concentrated tracking. The geometry added by LAGEOS II has also been found to improve station positioning accuracy for studies of regional deformation in the vicinity of the laser observatories. The improved SLR global reference frame can now be used to accurately define orbit and station positions from a variety of space and conventional geodetic methods.

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    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

  13. Orbit determination for next generation space clocks

    NASA Astrophysics Data System (ADS)

    Duchayne, L.; Mercier, F.; Wolf, P.

    2009-09-01

    We study the requirements on orbit determination compatible with operation of next generation space clocks at their expected uncertainty. Using the ACES (Atomic Clock Ensemble in Space) mission as an example, we develop a relativistic model for time and frequency transfer to investigate the effects of orbit determination errors. For the orbit error models considered we show that the required uncertainty goal can be reached with relatively modest constraints on the orbit determination of the space clock, which are significantly less stringent than expected from “naive” estimates. Our results are generic to all space clocks and represent a significant step towards the generalized use of next generation space clocks in fundamental physics, geodesy, and time/frequency metrology.

  14. The GEOS-3 orbit determination investigation

    NASA Technical Reports Server (NTRS)

    Pisacane, V. L.; Eisner, A.; Yionoulis, S. M.; Mcconahy, R. J.; Black, H. D.; Pryor, L. L.

    1978-01-01

    The nature and improvement in satellite orbit determination when precise altimetric height data are used in combination with conventional tracking data was determined. A digital orbit determination program was developed that could singly or jointly use laser ranging, C-band ranging, Doppler range difference, and altimetric height data. Two intervals were selected and used in a preliminary evaluation of the altimeter data. With the data available, it was possible to determine the semimajor axis and eccentricity to within several kilometers, in addition to determining an altimeter height bias. When used jointly with a limited amount of either C-band or laser range data, it was shown that altimeter data can improve the orbit solution.

  15. Lunar orbiter ranging data: initial results.

    PubMed

    Mulholland, J D; Sjogren, W L

    1967-01-01

    Data from two Lunar Orbiter spacecraft have been used to test the significance of corrections to the lunar ephemeris. Range residuals of up to 1700 meters were reduced by an order of magnitude by application of the corrections, with most of the residuals reduced to less than 100 meters. Removal of gross errors in the ephemeris reveals residual patterns that may indicate errors in location of observing stations, as well as the expected effects of Lunar nonsphericity. PMID:17799149

  16. Satellite-to-satellite tracking orbit determination

    Microsoft Academic Search

    B. T. Fang

    1978-01-01

    In the 1980's, low-earth-satellite orbits will be determined from one-way or relayed range and range-rate measurements to high-altitude orbiting spacecraft such as the two geo-synchronous satellites in the NASA Tracking and Data Relay Satellite System (TDRSS) and the 24 twelve-hour period, 63 deg inclination spacecraft in the DOD Global Positioning System (GPS). In this study, error analysis methods for satellite-to-satellite

  17. GPS orbit processing in support of low earth orbiter precise orbit determination

    Microsoft Academic Search

    I. Romero; H. Boomkamp; J. Dow; C. Garcia

    2003-01-01

    There are currently an increasing number of LEO missions incorporating dual frequency GPS receivers for Satellite to Satellite Tracking. The majority of LEO precise orbit determination (POD) strategies rely on high quality GPS orbits and clocks such as those supplied by the IGS Final product. The availability of these products may not satisfy operational requirements due to their ten day

  18. Mars Exploration Rovers orbit determination filter strategy

    NASA Technical Reports Server (NTRS)

    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

    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.

  19. Mars Exploration Rovers orbit determination filter strategy

    NASA Technical Reports Server (NTRS)

    McElrath, Timothy P.; Watkins, Michael M.; Portock, Brian M.; Graat, Eric J; Baird, Darren T; Wawrzyniak, Geoffrey G.; Attiyah, Amy A.; Guinn, Joseph R.; Antreasian, Peter G.; Baalke, Ronald C.; Taber, William L.

    2004-01-01

    The successful delivery of the Mars Exploration Rover (MER) landers to well within 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 analyze the results in ways that had never been previously attempted for an interplanetary mission. In addition to achieving sub-kilometer Mars-relative orbit determination knowledge, the filter strategy and process detected unexpected error sources, while at the same time proving robust by indicating thecorrect solution. Consequently, MER orbit determination set a new standard for interplanetary navigation.

  20. Kinematic Precise Orbit Determination for Gravity Field Determination

    Microsoft Academic Search

    D. Švehla; M. Rothacher

    In this paper we first present approaches and results in precise orbit determination (POD) for satellites in Low Earth Orbit\\u000a (LEO) based on one or two frequency GPS measurements and, secondly, we focus on the relations between kinematic POD and gravity\\u000a field determination. Using GPS measurements of the CHAMP satellite we show that it is possible to estimate kinematic positions

  1. Automated GPS-based operational orbit determination

    NASA Astrophysics Data System (ADS)

    Meek, Matthew Cameron

    Satellite operations depend on being able to generate accurate predictions of a spacecraft's orbit in a very short period of time, typically a few hours, after observations are made. The satellite ephemeris generated in this process is used by mission controllers for planning operations such as vehicle pointing and orbit adjust generation. The research described in this dissertation, investigates the methods and parameterizations necessary to achieve a fast and accurate ephemeris. To accomplish these investigations, an automated system is used. Two distinct spacecraft missions are discussed. They each have specific goals that must be met by their operational orbit determination systems. The first is ICESat, a scientific satellite that is part of NASA's Earth Observation System (EOS), and is operated by the Laboratory for Atmospheric and Space Physics (LASP). The primary OD requirement for ICESat is to provide predictions accurate to 10 meters cross-track for 48 hours to accomplish instrument pointing planning. The second mission is Quick-Bird, a commercial imaging satellite that is owned and operated by Digital Globe, Inc. QuickBird requires post-processed orbits with 3 meters (1sigma) accuracy in total position and 30 day orbit predictions to accomplish imagery planning. A variety of measurement processing schemes and error corrections are explored for each of these spacecraft. It is shown that it is possible to achieve approximately one meter (1sigma) orbits for both spacecraft in a orbit determination system that is designed for use in spacecraft operations. In the ICESat case, it was found that using single-differenced measurements met the requirements while reducing both the processing time and the logistical load for importing external data. QuickBird benefitted from the addition of the DRVID method of ionospheric removal and from using double-differenced measurements.

  2. Preliminary orbit determination for lunar satellites.

    NASA Technical Reports Server (NTRS)

    Lancaster, E. R.

    1973-01-01

    Methods for the determination of orbits of artificial lunar satellites from earth-based range rate measurements developed by Koskela (1964) and Bateman et al. (1966) are simplified and extended to include range measurements along with range rate measurements. For illustration, a numerical example is presented.

  3. Autonomous landmark tracking orbit determination strategy

    NASA Technical Reports Server (NTRS)

    Miller, J. K.; Cheng, Y.

    2003-01-01

    In this paper, an orbit determination strategy is described that is fully autonomous and relies on a computer-based crater detection and identification algorithm that is suitable for both automation of the ground based navigation system and autonomous spacecraft based navigation.

  4. Topex orbit determination using GPS tracking system

    Microsoft Academic Search

    Hyung Jin Rim

    1992-01-01

    An extensive simulation study was performed to analyze several aspects of Topex Precise Orbit Determination (POD) using the Global Positioning System (GPS). Since the error modeling is the key to such an experiment, extensive investigation was performed based on real GPS data processing experience to create realistic measurement and dynamic error models for GPS. Double-differenced Topex-GPS phase measurements were evaluated

  5. Energy integral method for gravity field determination from satellite orbit coordinates

    Microsoft Academic Search

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

    2003-01-01

    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

  6. Precise Orbit Determination of QZS-1

    NASA Astrophysics Data System (ADS)

    Hugentobler, U.; Steigenberger, P.; Rodriguez-Solano, C.; Hauschild, A.

    2011-12-01

    QZS-1, the first satellite of the Japanese Quasi Zenith Satellite System (QZSS) was launched in September 2010. Transmission of the standard codes started in December 2010 and the satellite was declared healthy in June 2011. Five stations of the COoperative Network for GIOVE Observation (CONGO) were upgraded to provide QZSS tracking capability. These five stations provide the basis for the precise orbit determination (POD) of the QZS-1 spacecraft. The stability and consistency of different orbital arc lengths is analyzed based on orbit fit residuals, day boundary discontinuities, and Satellite Laser Ranging residuals. As QZS-1 simultaneously transmits navigation signals on three frequencies in the L1, L2, and L5 band, different ionosphere-free linear combinations can be formed. The differences of the orbits computed from these different observables (ionosphere-free linear combination of L1/L2 and L1/L5) as well as the stability of the differential code biases estimated within the POD are studied. Finally, results of the attitude determination based on the navigation signal transmission from two different antennas onboard QZS-1 are presented.

  7. Topex orbit determination using GPS tracking system

    NASA Astrophysics Data System (ADS)

    Rim, Hyung Jin

    An extensive simulation study was performed to analyze several aspects of Topex Precise Orbit Determination (POD) using the Global Positioning System (GPS). Since the error modeling is the key to such an experiment, extensive investigation was performed based on real GPS data processing experience to create realistic measurement and dynamic error models for GPS. Double-differenced Topex-GPS phase measurements were evaluated in relation to improving the Earth geopotential model, which is the dominant error source for Topex POD. The effect of model errors on the Topex orbit and gravity recovery accuracies was evaluated. Long arc and short arc gravity solutions were compared to understand the effect of the model errors in using the long arc and the short arc solutions for the gravity recovery. Limiting factors for the long arc and the short arc gravity recovery were identified. The effect of ambiguity parameters on the gravity recovery was analyzed. Since the number of ambiguity parameters are quite large, an algorithm was developed to handle the ambiguity parameters more efficiently. Subarc parameters and empirical parameters were tested to find an optimal set of parameters to be estimated for the gravity recovery. Several gravity models were obtained by combining Topex-GPS information with a nominal geopotential information. These combined gravity models were evaluated by the statistical comparison of the recovered geopotential model parameters and by the Topex orbit analysis. Significant improvement in the nominal geopotential model, especially for the low degree harmonics, was achieved. More than a factor of three improvement in Topex orbit accuracy was demonstrated using the recovered gravity model. Analysis associated with predicted Topex radial orbit errors using the solution covariance indicates error estimates for the orbit accuracy is realistic.

  8. Determining criteria for single stage to orbit

    NASA Technical Reports Server (NTRS)

    Thorpe, Douglas G.

    1991-01-01

    The criteria for single stage to orbit (SSTO) vehicles are determined. The Saturn 5 launch vehicle and Space Shuttle are examined to validate the assumptions and results. This velocity is then used to determine if the selected vehicle can achieve orbit and calculate its payload capacity. The Saturn 5 launch vehicle with the following stages is examined: (1) second stage (S2) with Space Shuttle Main Engines (SSME); (2) second stage (S2) with J2 engines; (3) third stage (S4B) with SSME; and (4) third stage (S4B) with J2 engines. The Space Shuttle with the following configurations is examined: (1) external tank with SSME; (2) external tank with J2 engines; and (3) Atlas rocket booster (current configuration).

  9. 19 CFR 210.42 - Initial determinations.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...effective date of the initial determination. The findings and recommendations...judge in the recommended determination issued pursuant to § 210...the Commission in reaching determinations on remedy and bonding by...a). (3) An initial determination filed pursuant to §...

  10. The JPL orbit determination software system

    NASA Technical Reports Server (NTRS)

    Ekelund, J. E.

    1979-01-01

    The Jet Propulsion Laboratory (JPL) orbit determination software system is described. Consisting of a set of computer programs, this system has been developed at JPL for the primary purpose of determining the flight path of deep-space mission spacecraft in NASA's planetary program. Secondary uses include science studies in celestial mechanics and extraterrestrial atmospherics. Attention is given to such features as the capability for processing 30 data types from up to 15 tracking stations, and for precise navigation to natural satellites of outer planets. In addition, the system contains models for such conditions as mascons, atmospheric drag, attitude control, and finite motor burns, to provide for extensive solve-on capabilities.

  11. Using Onboard Telemetry for MAVEN Orbit Determination

    NASA Technical Reports Server (NTRS)

    Lam, Try; Trawny, Nikolas; Lee, Clifford

    2013-01-01

    Determination of the spacecraft state has been traditional done using radiometric tracking data before and after the atmosphere drag pass. This paper describes our approach and results to include onboard telemetry measurements in addition to radiometric observables to refine the reconstructed trajectory estimate for the Mars Atmosphere and Volatile Evolution Mission (MAVEN). Uncertainties in the Mars atmosphere models, combined with non-continuous tracking degrade navigation accuracy, making MAVEN a key candidate for using onboard telemetry data to help complement its orbit determination process.

  12. Orbit determination via adaptive Gaussian swarm optimization

    NASA Astrophysics Data System (ADS)

    Kiani, Maryam; Pourtakdoust, Seid H.

    2015-02-01

    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.

  13. Formation Flying In Highly Elliptical Orbits Initializing the Formation

    NASA Technical Reports Server (NTRS)

    Mailhe, Laurie; Schiff, Conrad; Hughes, Steven

    2000-01-01

    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.

  14. I: PRECISE ORBIT DETERMINATION AND GRAVITY FIELD MODELLING: Strategies for Precise Orbit Determination of Low Earth Orbiters Using the GPS

    Microsoft Academic Search

    U. Hugentobler; G. Beutler

    2003-01-01

    Considerable experience accumulated during the past decade in strategies for processing GPS data from ground-based geodetic\\u000a receivers. First experience on the use of GPS observations from spaceborne receivers for orbit determination of satellites\\u000a on low altitude orbits was gained with the launch of TOPEX\\/POSEIDON ten years ago. The launch of the CHAMP satellite in July\\u000a 2000 stimulated a number of

  15. Integrated Adjustment of LEO and GPS in Precision Orbit Determination

    Microsoft Academic Search

    J. H. Geng; C. Shi; Q. L. Zhao; M. R. Ge; J. N. Liu

    At present, usually only the ground stations are used for the precise orbit determination (POD) of GPS satellites. The precise\\u000a orbits of Low Earth Orbiters (LEO) are determined with GPS orbits and clocks fixed. The integrated adjustment of LEO and GPS\\u000a for POD that is first reported in (Zhu et al., 2004),which means the orbits of GPS satellites and LEOs

  16. Mars Exploration Rover Cruise Orbit Determination

    NASA Technical Reports Server (NTRS)

    Portock, Brian; Baird, Darren; Graat, Eric; Guinn, Joseph; McElrath, Tim; Watkins, Michael

    2004-01-01

    The Mars Exploration Rover project consisted of two missions (MER-A: spirit rover and MER-B: opportunity rover) that launched spacecraft on June 10, 2003, and July 8, 2003, respectively. The spacecraft arrived at Mars approximately seven months later on January 4, 2004, and January 24, 2004. These spacecraft needed to be precisely navigated to a Mars atmospheric entry flight path angle of -11.5 deg +/-0.12 deg (3(sigma)) for MER-A and +/-0.14 deg (3(sigma)) for MER-B in order to satisfy the landing site delivery requirements. The orbit determination task of the navigation team needed to accurately determine the trajectory of the spacecraft, predict the trajectory to Mars atmospheric entry, and account for all possible errors sources so that the each spacecraft could be correctly targeted using five trajectory corrections along the way. This paper describes the orbit determination analysis which allowed MER-A to be targeted using only four trajectory correction maneuvers to an entry flight path angle of -11.49 deg +/-O.010 deg (3(sigma)) and MER-B to be targeted using only three trajectory correction maneuvers to an entry flight path angle of -11.47 +/-0.021 deg(3(sigma)).

  17. Real-time Sub-cm Differential Orbit Determination of two Low-Earth Orbiters with GPS Bias Fixing

    NASA Technical Reports Server (NTRS)

    Wu, Sien-Chong; Bar-Sever, Yoaz E.

    2006-01-01

    An effective technique for real-time differential orbit determination with GPS bias fixing is formulated. With this technique, only real-time GPS orbits and clocks are needed (available from the NASA Global Differential GPS System with 10-20 cm accuracy). The onboard, realtime orbital states of user satellites (few meters in accuracy) are used for orbit initialization and integration. An extended Kalman filter is constructed for the estimation of the differential orbit between the two satellites as well as a reference orbit, together with their associating dynamics parameters. Due to close proximity of the two satellites and of similar body shapes, the differential dynamics are highly common and can be tightly constrained which, in turn, strengthens the orbit estimation. Without explicit differencing of GPS data, double-differenced phase biases are formed by a transformation matrix. Integer-valued fixing of these biases are then performed which greatly strengthens the orbit estimation. A 9-day demonstration between GRACE orbits with baselines of approx.200 km indicates that approx.80% of the double-differenced phase biases can successfully be fixed and the differential orbit can be determined to approx.7 mm as compared to the results of onboard K-band ranging.

  18. CHAMP rapid orbit determination for GPS atmospheric limb sounding

    Microsoft Academic Search

    R. König; S. Zhu; Ch. Reigber; K.-H. Neumayer; H. Meixner; R. Galas; G. Baustert; P. Schwintzer

    2002-01-01

    In preparation of the CHAMP small satellite LEO (Low Earth Orbit) mission to be launched on July 15, 2000, the GeoForschungsZentrum Potsdam (GFZ) enhanced its high precision orbit determination capabilities in order to rapidly produce precise LEO and GPS (Global Positioning System) orbital products. These orbits shall be available at 3 hour intervals with a latency of 2 hours after

  19. CATALOG OF ORBIT DETERMINATION RESULTS FOR LINKED, AUTONOMOUS,

    E-print Network

    Born, George

    shown that Liaison Navigation works for Earth-Moon halo orbits.2 This catalog extends those resultsCATALOG 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

  20. Precise orbit determination of low Earth orbiters using undifferenced GPS data

    NASA Astrophysics Data System (ADS)

    Kuang, Cui-lin; Hou, Fen

    2006-10-01

    Although POD with GPS has been tested using data from various satellites (e.g. CHAMP, GRACE etc.) with different approaches, there are still many open issues concerning the optimum way to determine LEO satellite orbits with GPS. The emphasis of this paper is to develop an efficient method for precise orbit determination of LEOs. To avoid the need for reference measurements from ground-based reference receivers, the analysis is based on an undifferenced processing of GPS code and carrier-phase measurements. The idea was to combine the kinematic and dynamic approaches, by using them interactively, in separate solutions, fitting dynamic orbits to kinematic orbit. So a purely kinematic orbit for the LEOs is obtained simultaneously with the reduced-dynamic orbit. Testing results show the precise of PPP kinematic orbit is about 22cm, and the precise of reduced-dynamic orbit is about 9cm. Also the reduced-dynamic orbit is smoother than PPP kinematic orbit.

  1. Investigation of orbit determination using the GPS constellation

    Microsoft Academic Search

    Jean Francois Cretaux

    1993-01-01

    The Global Positioning System (GPS) and Landsat 5 orbits have been computed at CNES with the orbit determination software ZOOM. The strategy investigated is a semi-dynamic, semi-geometric strategy. For the first step, the GPS orbits were purely dynamically adjusted. Next a preliminary Landsat 5 spacecraft orbit was geometrically estimated (in a pre-processing phase) and then this orbit was dynamically adjusted.

  2. Application of two special orbits in the orbit determination of lunar satellites

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Hou, Xi-Yun; Tang, Jing-Shi; Liu, Lin

    2014-10-01

    Using inter-satellite range data, the combined autonomous orbit determination problem of a lunar satellite and a probe on some special orbits is studied in this paper. The problem is firstly studied in the circular restricted three-body problem, and then generalized to the real force model of the Earth-Moon system. Two kinds of special orbits are discussed: collinear libration point orbits and distant retrograde orbits. Studies show that the orbit determination accuracy in both cases can reach that of the observations. Some important properties of the system are carefully studied. These findings should be useful in the future engineering implementation of this conceptual study.

  3. GPS-based precision orbit determination - A Topex flight experiment

    Microsoft Academic Search

    William G. Melbourne; Edgar S. Davis

    1988-01-01

    Plans for a Topex\\/Poseiden flight experiment to test the accuracy of using GPS data for precision orbit determination of earth satellites are presented. It is expected that the GPS-based precision orbit determination will provide subdecimeter accuracies in the radial component of the Topex orbit when the extant gravity model is tuned for wavelengths longer than about 1000 kms. The concept,

  4. Toward decimeter Topex orbit determination using GPS

    NASA Astrophysics Data System (ADS)

    Wu, Sien-Chong; Yunck, Thomas P.; Hajj, George A.

    Several practical aspects of precision GPS-based Topex orbit determination are investigated. Multipath signals contaminating Topex pseudorange data are greatly reduced by placing the GPS antenna on a conducting backplate consisting of concentric choke rings to attenuate signals coming in from the Topex horizon and below, and by elevating it on a boom to keep it well above all reflecting surfaces. A proper GPS antenna cutoff view angle is chosen so that a sufficient number of GPS satellites with good geometry are in view while reception of reflected signals is minimized. The geometrical strength of the tracking data is optimized by properly selecting GPS satellites to be observed so as to provide data with moderate continuity, low PDOP, and common visibility with ground tracking sites. The tracking performance is greatly enhanced when three complementary sites are added to the minimum ground tracking network consisting of the three NASA DSN sites.

  5. Toward decimeter Topex orbit determination using GPS

    NASA Technical Reports Server (NTRS)

    Wu, Sien-Chong; Yunck, Thomas P.; Hajj, George A.

    1990-01-01

    Several practical aspects of precision GPS-based Topex orbit determination are investigated. Multipath signals contaminating Topex pseudorange data are greatly reduced by placing the GPS antenna on a conducting backplate consisting of concentric choke rings to attenuate signals coming in from the Topex horizon and below, and by elevating it on a boom to keep it well above all reflecting surfaces. A proper GPS antenna cutoff view angle is chosen so that a sufficient number of GPS satellites with good geometry are in view while reception of reflected signals is minimized. The geometrical strength of the tracking data is optimized by properly selecting GPS satellites to be observed so as to provide data with moderate continuity, low PDOP, and common visibility with ground tracking sites. The tracking performance is greatly enhanced when three complementary sites are added to the minimum ground tracking network consisting of the three NASA DSN sites.

  6. TDRSS tracking data and orbit determination evaluation

    NASA Technical Reports Server (NTRS)

    Campion, R. E.; Teles, J.; Pitt, P.

    1984-01-01

    TDRS-1 was launched on April 4, 1983. This paper presents preliminary results of TDRSS tracking data evaluation through September 1983. TDRSS tracking data evaluation is a summary of valid tracking data that characterizes data quality. TDRS-1 orbit accuracy is evaluated by using orbit consistency measured by comparing overlaps of TDRS-1 ephemerides produced from consecutive data arcs. TDRS-1 and user orbit accuracies and consistencies are also estimated. Orbit accuracy is estimated by comparing user orbits based on tracking data obtained both through the TDRSS and from ground-based tracking.

  7. OrbView-3 Initial On-Orbit Characterization

    NASA Technical Reports Server (NTRS)

    Ross, Kent; Blonski, Slawomir; Holekamp, Kara; Pagnutti, Mary; Zanoni, Vicki; Carver, David; Fendley, Debbie; Smith, Charles

    2004-01-01

    NASA at Stennis Space Center (SSC) established a Space Act Agreement with Orbital Sciences Corporation (OSC) and ORBIMAGE Inc. to collaborate on the characterization of the OrbView-3 system and its imagery products and to develop characterization techniques further. In accordance with the agreement, NASA performed an independent radiometric, spatial, and geopositional accuracy assessment of OrbView-3 imagery acquired before completion of the system's initial on-orbit checkout. OSC acquired OrbView-3 imagery over SSC from July 2003 through January 2004, and NASA collected ground reference information coincident with many of these acquisitions. After evaluating all acquisitions, NASA deemed two multispectral images and five panchromatic images useful for characterization. NASA then performed radiometric, spatial, and geopositional characterizations.

  8. Numerical determination of three-dimensional periodic orbits generated from vertical self-resonant satellite orbits

    Microsoft Academic Search

    I. A. Robin; V. V. Markellos

    1980-01-01

    The mechanism by which ‘vertical’ branches consisting of symmetric, three-dimensional periodic orbits bifurcate from families of plane orbits at ‘veertical self-resonant’ orbits is discussed, with emphasis on the relationship between symmetry properties and multiplicity, and methods for the numerical determination of such branches are described. As examples, eight new families of all symmetry classes which branch vertically from the familyf

  9. Testing A GPS Technique For Precise Low Earth Orbit Determination

    Microsoft Academic Search

    O. L. Colombo; D. D. Rowlands; D. Chin; S. Poulouse

    2002-01-01

    An orbit-determination procedure that combines kinematic and dynamic techniques has been tested using two full days of on-board GPS receiver data from TOPEX and from 21 IGS sites. The resulting orbits agree to better than: 4 cm (rms) in height, 20 cm (rms) in horizontal, and 2 cm bias in each, with the corresponding Goddard Precise Orbit Estimates (POE). These

  10. An Efficient LEO Precision Orbit Determination For GPS Meteorology

    Microsoft Academic Search

    T. Bae; D. Grejner-Brzezinska

    2006-01-01

    Numerous Low Earth Orbit (LEO) satellites, including TOPEX\\/POSEIDON, CHAMP and GRACE, have been launched for scientific purposes at altitudes ranging from 400 km to 1300 km. Because of highly complex dynamics in their orbits, coming from the Earth gravity field and the atmospheric drag, accurate and fast LEO orbit determination has been a great research challenge. To support GPS meteorology

  11. Long-term orbit determination and prediction for geodynamic investigations

    Microsoft Academic Search

    B. E. Douglas

    1976-01-01

    Comparison of artificial earth satellite orbits determined with different data types and\\/or force model parameters indicates that the error in such orbits is essentially short periodic with respect to the satellite motion. Therefore the mean elements of satellite orbits can be expected to be very precisely known. A precision of a few centimeters in mean semi-major axis and a few

  12. GPS as an orbit determination subsystems

    NASA Astrophysics Data System (ADS)

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

    1995-05-01

    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.

  13. Study on reduced-dynamic orbit determination of low Earth orbiters

    NASA Astrophysics Data System (ADS)

    Han, Bao-min

    2007-11-01

    Some orbit determination methods using onboard GPS Observations were discussed firstly in this paper, especially the principle and mathematical model of reduced-dynamic Precise Orbit Determination (POD) of Low Earth Satellite (LEO) based on undifferenced spaceborne dual-frequency GPS data. Then a weeklong (from July 28, 2003 to August 3,2003) dual-frequency onboard GPS observation from CHAMP satellite was computed using reduced-dynamic POD. Compared with TUM solutions, our CHAMP orbiting results of one week using reduced dynamic POD method are within 8 centimeters, which can meet the requirements of some higher precision orbit satellite orbits. In order to obtain high precision orbiting results, the impact of different gravity models and proper interval of pseudo-stochastic-pulses on the orbit determination accuracy were analyzed as well.

  14. A new method for determination of satellite orbits by transfer

    Microsoft Academic Search

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

    2009-01-01

    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

  15. EURECA 11 months in orbit: Initial post flight investigation results

    NASA Technical Reports Server (NTRS)

    Dover, Alan; Aceti, Roberto; Drolshagen, Gerhard

    1995-01-01

    This paper gives a brief overview of the European free flying spacecraft 'EURECA' and the initial post flight investigations following its retrieval in June 1993. EURECA was in low earth orbit for 11 months commencing in August 1992, and is the first spacecraft to be retrieved and returned to Earth since the recovery of LDEF. The primary mission objective of EURECA was the investigation of materials and fluids in a very low micro-gravity environment. In addition other experiments were conducted in space science, technology and space environment disciplines. The European Space Agency (ESA) has taken the initiative in conducting a detailed post-flight investigation to ensure the full exploitation of this unique opportunity.

  16. Ulysses orbit determination at high declinations

    NASA Astrophysics Data System (ADS)

    McElrath, Timothy P.; Lewis, George D.

    1995-05-01

    The trajectory of the Ulysses spacecraft caused its geocentric declination to exceed 60 deg South for over two months during the Fall of 1994, permitting continuous tracking from a single site. During this time, spacecraft operations constraints allowed only Doppler tracking data to be collected, and imposed a high radial acceleration uncertainty on the orbit determination process. The unusual aspects of this situation have motivated a re-examination of the Hamilton-Melbourne results, which have been used before to estimate the information content of Doppler tracking for trajectories closer to the ecliptic. The addition of an acceleration term to this equation is found to significantly increase the declination uncertainty for symmetric passes. In addition, a simple means is described to transform the symmetric results when the tracking pass is non-symmetric. The analytical results are then compared against numerical studies of this tracking geometry and found to be in good agreement for the angular uncertainties. The results of this analysis are applicable to the Near Earth Asteroid Rendezvous (NEAR) mission and to any other missions with high declination trajectories, as well as to missions using short tracking passes and/or one-way Doppler data.

  17. Ulysses orbit determination at high declinations

    NASA Technical Reports Server (NTRS)

    Mcelrath, Timothy P.; Lewis, George D.

    1995-01-01

    The trajectory of the Ulysses spacecraft caused its geocentric declination to exceed 60 deg South for over two months during the Fall of 1994, permitting continuous tracking from a single site. During this time, spacecraft operations constraints allowed only Doppler tracking data to be collected, and imposed a high radial acceleration uncertainty on the orbit determination process. The unusual aspects of this situation have motivated a re-examination of the Hamilton-Melbourne results, which have been used before to estimate the information content of Doppler tracking for trajectories closer to the ecliptic. The addition of an acceleration term to this equation is found to significantly increase the declination uncertainty for symmetric passes. In addition, a simple means is described to transform the symmetric results when the tracking pass is non-symmetric. The analytical results are then compared against numerical studies of this tracking geometry and found to be in good agreement for the angular uncertainties. The results of this analysis are applicable to the Near Earth Asteroid Rendezvous (NEAR) mission and to any other missions with high declination trajectories, as well as to missions using short tracking passes and/or one-way Doppler data.

  18. GPS single-frequency orbit determination for low Earth orbiting satellites

    Microsoft Academic Search

    Heike Bock; Adrian Jäggi; Rolf Dach; Stefan Schaer; Gerhard Beutler

    2008-01-01

    The determination of high-precision orbits for Low Earth Orbiting (LEO) satellites (e.g., CHAMP, GRACE, MetOp) is based on dual-frequency tracking data from onboard GPS receivers. The two frequencies allow it to eliminate the first order ionosphere effects on the level of the carrier phase measurement noise. Data screening and precise orbit determination (POD) procedures are optimized under the assumption of

  19. GPS single-frequency orbit determination for low Earth orbiting satellites

    Microsoft Academic Search

    H. Bock; A. Jäggi; R. Dach; S. Schaer; G. Beutler

    2009-01-01

    The determination of high-precision orbits for Low Earth Orbiting (LEO) satellites (e.g., CHAMP, GRACE, MetOp-A) is based on dual-frequency tracking data from on-board GPS (Global Positioning System) receivers. The two frequencies allow it to eliminate the first order ionosphere effects. Data screening and precise orbit determination (POD) procedures are optimized under the assumption of the availability of two frequencies.If only

  20. Kinematic and reduced-dynamic precise orbit determination of low earth orbiters

    Microsoft Academic Search

    D. Svehla; M. Rothacher

    2003-01-01

    Various methods for kinematic and reduced-dynamic precise orbit determination (POD) of Low Earth Orbiters (LEO) were developed based on zero- and double-differencing of GPS carrier-phase measurements with and without ambiguity resolution. In this paper we present the following approaches in LEO precise orbit determination: - zero-difference kinematic POD, - zero-difference dynamic POD, - double-difference kinematic POD with and without ambiguity

  1. Orbit determination and prediction study for Dynamic Explorer 2

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    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.

  2. A new method to determine low Earth orbit using GPS

    Microsoft Academic Search

    Zhi Zhang; Xu Yang

    1993-01-01

    In this paper, it is discussed to use Global Positioning Satellite (GPS) to determine low Earth orbit (LEO). The advantages which can be achieved from GPS are analyzed, while the shortcomings are also given. In dealing with the shortcomings, a direct-orbit-determination scheme is proposed in which the six orbital parameters are solved from the raw measurements, pseudo-ranges and pseudo-range rates,

  3. MicroGPS for Low-Cost Orbit Determination

    Microsoft Academic Search

    S. C. Wu; W. I. Bertiger; D. Kuang; S. M. Lichten; S. Nandi; L. J. Romans; J. M. Srinivasan

    1997-01-01

    This article presents a new technology for satellite orbit determination using a simple Global Positioning System (GPS) receiver (microGPS) with ultra-low cost, power, and mass. The capability of low-cost orbit determination with mi- croGPS for a low Earth-orbiting satellite, Student Nitric Oxide Explorer (SNOE), is demonstrated using actual GPS data from the GPS\\/Meteorology (MET) satellite. The measurements acquired by the

  4. Precise orbit determination of low Earth orbiters using undifferenced GPS data

    Microsoft Academic Search

    Cui-lin Kuang; Fen Hou

    2006-01-01

    Although POD with GPS has been tested using data from various satellites (e.g. CHAMP, GRACE etc.) with different approaches, there are still many open issues concerning the optimum way to determine LEO satellite orbits with GPS. The emphasis of this paper is to develop an efficient method for precise orbit determination of LEOs. To avoid the need for reference measurements

  5. 25 CFR 700.303 - Initial Commission determinations.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Initial Commission determinations. 700.303 Section...RELOCATION PROCEDURES Determination of Eligibility, Hearing... Initial Commission determinations. (a) Initial Commission Determination concerning...

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    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.

  7. The determination of the interplanetary orbits of Vikings 1 and 2

    Microsoft Academic Search

    K. H. Rourke; C. H. Acton; W. G. Breckenridge; J. K. Campbell; C. S. Christensen; A. J. Donegan; N. Jerath; N. A. Mottinger; G. C. Rinker; F. B. Winn

    1977-01-01

    A description is presented of the navigation-related events of the Viking Mars mission. Orbit determination system fundamentals are discussed, taking into account the trajectory models, observation models, radio data models, range considerations, optical data models, filter models, the orbit determination process, critical orbit determination inputs, and orbit determination errors. Attention is also given to questions of orbit determination strategy, orbit

  8. Benefits Derived From Laser Ranging Measurements for Orbit Determination of the GPS Satellite Orbit

    NASA Technical Reports Server (NTRS)

    Welch, Bryan W.

    2007-01-01

    While navigation systems for the determination of the orbit of the Global Position System (GPS) have proven to be very effective, the current research is examining methods to lower the error in the GPS satellite ephemerides below their current level. Two GPS satellites that are currently in orbit carry retro-reflectors onboard. One notion to reduce the error in the satellite ephemerides is to utilize the retro-reflectors via laser ranging measurements taken from multiple Earth ground stations. Analysis has been performed to determine the level of reduction in the semi-major axis covariance of the GPS satellites, when laser ranging measurements are supplemented to the radiometric station keeping, which the satellites undergo. Six ground tracking systems are studied to estimate the performance of the satellite. The first system is the baseline current system approach which provides pseudo-range and integrated Doppler measurements from six ground stations. The remaining five ground tracking systems utilize all measurements from the current system and laser ranging measurements from the additional ground stations utilized within those systems. Station locations for the additional ground sites were taken from a listing of laser ranging ground stations from the International Laser Ranging Service. Results show reductions in state covariance estimates when utilizing laser ranging measurements to solve for the satellite s position component of the state vector. Results also show dependency on the number of ground stations providing laser ranging measurements, orientation of the satellite to the ground stations, and the initial covariance of the satellite's state vector.

  9. Semi-Major Axis Knowledge and GPS Orbit Determination

    NASA Technical Reports Server (NTRS)

    Carpenter, J. Russell; Schiesser, Emil R.; Bauer, F. (Technical Monitor)

    2000-01-01

    In recent years spacecraft designers have increasingly sought to use onboard Global Positioning System receivers for orbit determination. The superb positioning accuracy of GPS has tended to focus more attention on the system's capability to determine the spacecraft's location at a particular epoch than on accurate orbit determination, per se. The determination of orbit plane orientation and orbit shape to acceptable levels is less challenging than the determination of orbital period or semi-major axis. It is necessary to address semi-major axis mission requirements and the GPS receiver capability for orbital maneuver targeting and other operations that require trajectory prediction. Failure to determine semi-major axis accurately can result in a solution that may not be usable for targeting the execution of orbit adjustment and rendezvous maneuvers. Simple formulas, charts, and rules of thumb relating position, velocity, and semi-major axis are useful in design and analysis of GPS receivers for near circular orbit operations, including rendezvous and formation flying missions. Space Shuttle flights of a number of different GPS receivers, including a mix of unfiltered and filtered solution data and Standard and Precise Positioning, Service modes, have been accomplished. These results indicate that semi-major axis is often not determined very accurately, due to a poor velocity solution and a lack of proper filtering to provide good radial and speed error correlation.

  10. Semi-Major Axis Knowledge and GPS Orbit Determination

    NASA Technical Reports Server (NTRS)

    Carpenter, J. Russell; Schiesser, Emil R.; Bauer, F. (Technical Monitor)

    2000-01-01

    In recent years spacecraft designers have increasingly sought to use onboard Global Positioning System receivers for orbit determination. The superb positioning accuracy of GPS has tended to focus more attention on the system's capability to determine the spacecraft's location at a particular epoch than on accurate orbit determination, per se. The determination of orbit plane orientation and orbit shape to acceptable levels is less challenging than the determination of orbital period or semi-major axis. It is necessary to address semi-major axis mission requirements and the GPS receiver capability for orbital maneuver targeting and other operations that require trajectory prediction. Failure to determine semi-major axis accurately can result in a solution that may not be usable for targeting the execution of orbit adjustment and rendezvous maneuvers. Simple formulas, charts, and rules of thumb relating position, velocity, and semi-major axis are useful in design and analysis of GPS receivers for near circular orbit operations, including rendezvous and formation flying missions. Space Shuttle flights of a number of different GPS receivers, including a mix of unfiltered and filtered solution data and Standard and Precise Positioning Service modes, have been accomplished. These results indicate that semi-major axis is often not determined very accurately, due to a poor velocity solution and a lack of proper filtering to provide good radial and speed error correlation.

  11. TOPEX/Poseidon precision orbit determination production and expert system

    NASA Technical Reports Server (NTRS)

    Putney, Barbara; Zelensky, Nikita; Klosko, Steven

    1993-01-01

    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.

  12. Strategies for high-precision Global Positioning System orbit determination

    NASA Technical Reports Server (NTRS)

    Lichten, Stephen M.; Border, James S.

    1987-01-01

    Various strategies for the high-precision orbit determination of the GPS satellites are explored using data from the 1985 GPS field test. Several refinements to the orbit determination strategies were found to be crucial for achieving high levels of repeatability and accuracy. These include the fine tuning of the GPS solar radiation coefficients and the ground station zenith tropospheric delays. Multiday arcs of 3-6 days provided better orbits and baselines than the 8-hr arcs from single-day passes. Highest-quality orbits and baselines were obtained with combined carrier phase and pseudorange solutions.

  13. Phenomenological determination of the orbital angular momentum.

    SciTech Connect

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

    2009-01-01

    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.

  14. Phenomenological Determination of the Orbital Angular Momentum

    SciTech Connect

    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

    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.

  15. Investigation of orbit determination using the GPS constellation

    NASA Astrophysics Data System (ADS)

    Cretaux, Jean Francois

    The Global Positioning System (GPS) and Landsat 5 orbits have been computed at CNES with the orbit determination software ZOOM. The strategy investigated is a semi-dynamic, semi-geometric strategy. For the first step, the GPS orbits were purely dynamically adjusted. Next a preliminary Landsat 5 spacecraft orbit was geometrically estimated (in a pre-processing phase) and then this orbit was dynamically adjusted. The data used for this treatment were collected during the Spring 1985 experiment from ten sites in the continental United States. At the same time, data were collected by the GPSPAC receiver on board the Landsat 5 spacecraft. To test our orbit determination process on GPS, newer data coming from the GIG'91 campaign were used. The pseudo-range measurements, smoothed by the carrier phase measurement, were used for the GPS orbit determination. Moreover, we have also introduced in our software an empirical dynamical model inferred from Hill's equations. The processing of the GPS and Landsat 5 data have allowed us to validate this model. For the GPS satellite, a precision of 2 to 3 meters in the 3 directions was achieved with the Spring 1985 experiment. For the Landsat 5 satellite, we obtained a precision of 4 to 5 meters with the strategy described here. We have also evaluated the impact of the ground network and of the GPS orbits on the low satellite orbit. This research shows that global coverage and precise ground station locations are necessary to have precise GPS orbits and therefore to compute a precise low satellite orbit. With the GIG'91 campaign, a precision of less than one meter in the overlap tests, and measurement residuals of a few centimeters were achieved on the GPS orbits. Therefore, sub-metric precision on a low satellite orbit can reasonably be expected.

  16. GPS as an orbit determination subsystems

    Microsoft Academic Search

    Richard Fennessey; Pat Roberts; Robin Knight; Bart Vanvolkinburg

    1995-01-01

    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

  17. Definitive orbit determination for the HEAO2 spacecraft

    Microsoft Academic Search

    R. L. Smith; M. K. Mallick

    1984-01-01

    Precise ephemerides for the High Energy Astronomy Observatory-2 (HEAO-2) were computed to assist in the Charles Stark Draper Laboratory development of an onboard orbit determination technique. Weighted least-squares, batch orbit solutions were calculated using a high-precision earth gravity model and an approximate model for intermittent spacecraft thrusting. With these improvements, orbit solution consistencies at the 50- to 100-meter level were

  18. TOPEX\\/Poseidon precision orbit determination production and expert system

    Microsoft Academic Search

    Barbara Putney; Nikita Zelensky; Steven Klosko

    1993-01-01

    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

  19. Efficient methods for determining precise orbits of low Earth orbiters using the Global Positioning System

    Microsoft Academic Search

    Heike Bock

    2003-01-01

    The main part of this work dealt with the development and evaluation of efficient methods for precise orbit determination of LEOs. A kinematic approach using GPS zero-difference observations was developed (program LEOKIN) and a procedure for generation of dynamic and reduced-dynamic orbits was presented (program SATORB). The procedures have been tested using long GPS data series gathered by two LEO

  20. Precise Orbit Determination of Low Earth Orbiters with GPS Point Positioning

    Microsoft Academic Search

    Sunil B. Bisnath; Richard B. Langley

    2001-01-01

    Precise orbit determination (POD) of low earth orbiters (LEOs) with GPS is becoming a standard practice in the space science community. The need for such information has been growing rapidly due to such scientific applications as radio occultation and ever increasing demands from engineering applications such as space - based earth sensor positioning. The conventional GPS - based POD strategies

  1. Precision Assessment of Near Real Time Precise Orbit Determination for Low Earth Orbiter

    Microsoft Academic Search

    Jong-Yeoun Choi; Sang-Jeong Lee

    2011-01-01

    The precise orbit determination (POD) of low earth orbiter (LEO) has complied with its required positioning accuracy by the double-differencing of observations between International GNSS Service (IGS) and LEO to eliminate the common clock error of the global positioning system (GPS) satellites and receiver. Using this method, we also have achieved the 1 m positioning accuracy of Korea Multi-Purpose Satellite

  2. Orbit determination strategy using single-frequency GPS data

    Microsoft Academic Search

    Yoola Hwang

    2003-01-01

    This thesis presents an orbit solution determined by various ionospheric error correction schemes for LEO (Low Earth Orbit) satellites carrying single frequency GPS receiver. A scale factor, dependent on satellite altitude, was applied to the model-based ionosphere correction method. The direct-calibration method, DRVID (Differenced Range Versus Integrated Doppler), used the difference of group delay and phase advance to correct for

  3. Precise Orbit Determination and Cal\\/Val for GOCE

    Microsoft Academic Search

    Henno Boomkamp; John Dow; Michiel Otten

    In its position as IGS analysis centre, the ESOC navigation Office has extensive expertise in the processing of GPS data for precise orbit determination purposes. On-going developments in this area include the gradual implementation of real-time processing, and the possible incorporation of GPS data from low Earth orbiting satellites in IGS product generation. From this position, and its close interaction

  4. The possible effect of reaction wheel unloading on orbit determination for Chang'E-1 lunar mission

    NASA Astrophysics Data System (ADS)

    Jianguo, Yan; Jingsong, Ping; Fei, Li

    During the flight of 3-axis stabilized lunar orbiter i e SELENE main orbiter Chang E-1 due to the overflow of the accumulated angular momentum the reaction-wheel will be unloaded during certain period so as to release the angular momentum for initialization Then the momentum wheel will be reloaded for satellite attitude measurement and control Above action will not only change the attitude but also change the orbit of the spacecraft Assuming the reaction-wheel unloading is carried out twice a day according to the current engineering designation and plan for SELENE main orbiter and Chang E-1 missions considering the algebra configuration of the tracking stations the Moon and the lunar orbiter the orbit determination is simulated for 14 days evolution of lunar orbiter In the simulation the satellite orbit is generated using GEODYNII code Based on the generated orbit the common view time period of the satellite by VLBI and USB network in every day is computed the orbit determination is processed for all the arcs of the orbit The orbit determination result of 28 orbits in 14 days is provided The orbits cover most of the possible geometrical configuration among orbiter the Moon and the tracking network The analysis here can benefit the tracking designation and plan for Chang E-1 mission

  5. Precise orbit determination for NASA's Earth Observing System using GPS

    NASA Technical Reports Server (NTRS)

    Williams, Bobby G.

    1988-01-01

    A precision orbit determination technique for NASA's Earth Observing System (EOS) is discussed. The technique exploits the redundant geometric information from GPS carrier phase and P-code pseudorange measurements and minimizes the requirements for precision dynamical modeling. Performance estimates for the application of the technique to the orbit geometry planned for the EOS platforms show that decimeter accuracies of orbit position may be obtained. The sensitivity of the predicted orbit uncertainties to model errors for station locations, nongravitational platform accelerations, and earth gravity are presented.

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

    NASA Astrophysics Data System (ADS)

    Löcher, Anno; Kusche, Jürgen

    2014-05-01

    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.

  7. 32 CFR 300.8 - Initial determinations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...ACT PROGRAM FOIA Request Processing § 300.8 Initial determinations...for fee waivers or expedited processing. By this regulation...primary responsibility for processing the request. (b) The...essentially meaningless set of words and phrases, or even...

  8. CHAMP precise orbit determination including external attitude information

    NASA Astrophysics Data System (ADS)

    Patiño, E.; van den Ijssel, J.; Visser, P.

    2003-04-01

    The CHAMP satellite was launched on 15 July 2000 into a near polar orbit around the Earth at an altitude of approximately 450 km. The main purpose of this mission is, besides the determination of the Earth's magnetic field and atmospheric parameters, the recovery of the Earth's gravitational field, an objective that would not be reached without a very accurate orbit. CHAMP orbits calculated at the Delft Institute for Earth-Oriented Space Research (DEOS) present an orbit accuracy at the sub-decimeter level. In order to improve the orbit accuracy, the external attitude information of the CHAMP satellite has been included in the orbit computation. However, preliminary tests have shown that using the quaternion data instead of a simple earthpointing model does not improve the orbit accuracy. The analysis of quaternion data shows that there are many data gaps and that the satellite attitude shows "strange behaviour" during several days. Therefore an extensive study has been conducted to see what is happening in the quaternion data. In this paper we present results for a period of the 35 days in May and June 2001. For this period we compute artificial quaternions for the data gaps using two different methods. First, quaternions are computed from precise orbits obtained without quaternion information and, second, by means of numerical interpolation. New CHAMP orbits will also be computed using these artificial quaternions and it will be assessed if this improves the orbit accuracy.

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

    NASA Astrophysics Data System (ADS)

    Tukaram Aghav, Sandip; Achyut Gangal, Shashikala

    2014-06-01

    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.

  10. Study on reduced-dynamic orbit determination of low Earth orbiters

    Microsoft Academic Search

    Bao-min Han

    2007-01-01

    Some orbit determination methods using onboard GPS Observations were discussed firstly in this paper, especially the principle and mathematical model of reduced-dynamic Precise Orbit Determination (POD) of Low Earth Satellite (LEO) based on undifferenced spaceborne dual-frequency GPS data. Then a weeklong (from July 28, 2003 to August 3,2003) dual-frequency onboard GPS observation from CHAMP satellite was computed using reduced-dynamic POD.

  11. 20 CFR 410.620 - Notice of initial determination.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...false Notice of initial determination. 410.620 Section...BENEFITS (1969- ) Determinations of Disability, Other Determinations, Administrative Review...620 Notice of initial determination. Written notice...

  12. Real-time on-board orbit determination with DORIS

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  13. Contribution of SLR tracking data to GNSS orbit determination

    NASA Astrophysics Data System (ADS)

    Urschl, Claudia; Beutler, Gerhard; Gurtner, Werner; Hugentobler, Urs; Schaer, Stefan

    GNSS orbits derived from microwave tracking data may be validated using SLR range measurements. Recent validation results show mean range residuals of several centimeters, as well as significant seasonal variations for the two GPS satellites that are equipped with retroreflector arrays. These differences may be assigned to orbit or observation modeling problems, or both. In order to study this issue, we analyzed several time series of SLR range residuals. GNSS microwave orbits from three IGS analysis centers differing in arc-length, in orbit modeling, and in attitude modeling were validated. The range residuals derived from the various GNSS orbits show similar periodic variations, which are correlated with eclipsing seasons and the sun's elevation above the orbital plane, indicating orbit or attitude modeling deficiencies. Moreover, we address the question, whether it would make sense to perform a combined analysis of microwave and SLR data for GNSS orbit determination, assuming that the existing modeling problems can be solved. With the available low number of SLR observations no significant improvement of the orbit accuracy is found. An a priori variance-covariance analysis shows an improvement of the situation, if continuous SLR tracking data of already a very small number of globally distributed SLR sites would be available.

  14. Kinematic and reduced-dynamic precise orbit determination of low earth orbiters

    NASA Astrophysics Data System (ADS)

    Švehla, D.; Rothacher, M.

    2003-06-01

    Various methods for kinematic and reduced-dynamic precise orbit determination (POD) of Low Earth Orbiters (LEO) were developed based on zero- and double-differencing of GPS carrier-phase measurements with and without ambiguity resolution. In this paper we present the following approaches in LEO precise orbit determination: - zero-difference kinematic POD, - zero-difference dynamic POD, - double-difference kinematic POD with and without ambiguity resolution, - double-difference dynamic POD with and without ambiguity resolution, - combined GPS/SLR reduced-dynamic POD. All developed POD approaches except the combination of GPS/SLR were tested using real CHAMP data (May 20-30, 2001) and independently validated with Satellite Laser Ranging (SLR) data over the same 11 days. With SLR measurements, additional combinations are possible and in that case one can speak of combined kinematic or combined reduced-dynamic POD. First results of such a combined GPS/SLR POD will be presented, too. This paper shows what LEO orbit accuracy may be achieved with GPS using different strategies including zerodifference and double-difference approaches. Kinematic versus dynamic orbit determination is presently an interesting issue that will also be discussed in this article.Key words. POD, kinematic orbit, dynamic orbit, LEO, CHAMP, ambiguity resolution, GPS, SLR

  15. Status of Precise Orbit Determination for Jason-2 Using GPS

    NASA Technical Reports Server (NTRS)

    Melachroinos, S.; Lemoine, F. G.; Zelensky, N. P.; Rowlands, D. D.; Pavlis, D. E.

    2011-01-01

    The JASON-2 satellite, launched in June 2008, is the latest follow-on to the successful TOPEX/Poseidon (T/P) and JASON-I altimetry missions. JASON-2 is equipped with a TRSR Blackjack GPS dual-frequency receiver, a laser retroreflector array, and a DORIS receiver for precise orbit determination (POD). The most recent time series of orbits computed at NASA GSFC, based on SLR/DORIS data have been completed using both ITRF2005 and ITRF2008. These orbits have been shown to agree radially at 1 cm RMS for dynamic vs SLRlDORIS reduced-dynamic orbits and in comparison with orbits produced by other analysis centers (Lemoine et al., 2010; Zelensky et al., 2010; Cerri et al., 2010). We have recently upgraded the GEODYN software to implement model improvements for GPS processing. We describe the implementation of IGS standards to the Jason2 GEODYN GPS processing, and other dynamical and measurement model improvements. Our GPS-only JASON-2 orbit accuracy is assessed using a number of tests including analysis of independent SLR and altimeter crossover residuals, orbit overlap differences, and direct comparison to orbits generated at GSFC using SLR and DORIS tracking, and to orbits generated externally at other centers. Tests based on SLR and the altimeter crossover residuals provide the best performance indicator for independent validation of the NASAlGSFC GPS-only reduced dynamic orbits. For the ITRF2005 and ITRF2008 implementation of our GPS-only obits we are using the IGS05 and IGS08 standards. Reduced dynamic versus dynamic orbit differences are used to characterize the remaining force model error and TRF instability. We evaluate the GPS vs SLR & DORIS orbits produced using the GEODYN software and assess in particular their consistency radially and the stability of the altimeter satellite reference frame in the Z direction for both ITRF2005 and ITRF2008 as a proxy to assess the consistency of the reference frame for altimeter satellite POD.

  16. Methods and progress on kinematic orbit determination of LEOs based on GPS

    Microsoft Academic Search

    Jiang-Fei Wu; Peng Du; Lei Wang; Cheng Huang

    2006-01-01

    The basic principles and methods of kinematic orbit determination of low earth orbiters (LEOs) based on GPS are discussed. It points out the merits and demerits of kinematic orbit determination methods. The characteristics of resolution of kinematic orbit determination methods are analyzed, and the corresponding processing strategies are provided. The latest progress of kinematic orbit determination of LEOs based on

  17. Precision orbit determination of altimetric satellites

    Microsoft Academic Search

    C. K. Shum; John C. Ries; Byron D. Tapley

    1994-01-01

    The ability to determine accurate global sea level variations is important to both detection and understanding of changes in climate patterns. Sea level variability occurs over a wide spectrum of temporal and spatial scales, and precise global measurements are only recently possible with the advent of spaceborne satellite radar altimetry missions. One of the inherent requirements for accurate determination of

  18. Orbit Determination and Navigation Software Testing for the Mars Reconnaissance Orbiter

    NASA Technical Reports Server (NTRS)

    Pini, Alex

    2011-01-01

    During the extended science phase of the Mars Reconnaissance Orbiter's lifecycle, the operational duties pertaining to navigation primarily involve orbit determination. The orbit determination process utilizes radiometric tracking data and is used for the prediction and reconstruction of MRO's trajectories. Predictions are done twice per week for ephemeris updates on-board the spacecraft and for planning purposes. Orbit Trim Maneuvers (OTM-s) are also designed using the predicted trajectory. Reconstructions, which incorporate a batch estimator, provide precise information about the spacecraft state to be synchronized with scientific measurements. These tasks were conducted regularly to validate the results obtained by the MRO Navigation Team. Additionally, the team is in the process of converting to newer versions of the navigation software and operating system. The capability to model multiple densities in the Martian atmosphere is also being implemented. However, testing outputs among these different configurations was necessary to ensure compliance to a satisfactory degree.

  19. Orbit Determination Accuracy for Comets on Earth-Impacting Trajectories

    NASA Technical Reports Server (NTRS)

    Kay-Bunnell, Linda

    2004-01-01

    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.

  20. GPS-based precise orbit determination of the very low Earth-orbiting gravity mission GOCE

    Microsoft Academic Search

    P. N. A. M. Visser; J. van den Ijssel

    2000-01-01

    A prerequisite for the success of future gravity missions like the European Gravity field and steady-state Ocean Circulation Explorer (GOCE) is a precise orbit determination (POD). A detailed simulation study has been carried out to assess the achievable orbit accuracy based on satellite-to-satellite tracking (SST) by the US global positioning system (GPS) and in conjunction the implications for gravity field

  1. GPS-based precise orbit determination of the very low Earth-orbiting gravity mission GOCE

    Microsoft Academic Search

    P. N. A. M. Visser; J. van den IJssel

    2000-01-01

    .  ?A prerequisite for the success of future gravity missions like the European Gravity field and steady-state Ocean Circulation\\u000a Explorer (GOCE) is a precise orbit determination (POD). A detailed simulation study has been carried out to assess the achievable\\u000a orbit accuracy based on satellite-to-satellite tracking (SST) by the US global positioning system (GPS) and in conjunction\\u000a the implications for gravity field

  2. Orbit Determination of Low-Earth-Orbit Spacecraft using Code Information of Global Positioning System Signals

    Microsoft Academic Search

    S. Purivigraipong; S. Kuntanapreeda

    This paper presents the study of the orbit determination of near-circular, low-Earth orbit (LEO) spacecraft using information of global position system (GPS) signals. The perturbed forces caused by Geo-potential and atmospheric drag was studied and investigated. An analytical formulation of Geo- potential was described in the form of the extensive spherical harmonics. The Earth's rotation was taken into account in

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  4. Evaluation of Improved Spacecraft Models for GLONASS Orbit Determination

    NASA Astrophysics Data System (ADS)

    Weiss, J. P.; Sibthorpe, A.; Harvey, N.; Bar-Sever, Y.; Kuang, D.

    2010-12-01

    High-fidelity spacecraft models become more important as orbit determination strategies achieve greater levels of precision and accuracy. In this presentation, we assess the impacts of new solar radiation pressure and attitude models on precise orbit determination (POD) for GLONASS spacecraft within JPLs GIPSY-OASIS software. A new solar radiation pressure model is developed by empirically fitting a Fourier expansion to solar pressure forces acting on the spacecraft X, Y, Z components using one year of recent orbit data. Compared to a basic “box-wing” solar pressure model, the median 24-hour orbit prediction accuracy for one month of independent test data improves by 43%. We additionally implement an updated yaw attitude model during eclipse periods. We evaluate the impacts of both models on post-processed POD solutions spanning 6-months. We consider a number of metrics such as internal orbit and clock overlaps as well as comparisons to independent solutions. Improved yaw attitude modeling reduces the dependence of these metrics on the “solar elevation” angle. The updated solar pressure model improves orbit overlap statistics by several mm in the median sense and centimeters in the max sense (1D). Orbit differences relative to the IGS combined solution are at or below the 5 cm level (1D RMS).

  5. Orbit Determination with Mixture Observations of Multiple Objects

    NASA Astrophysics Data System (ADS)

    Wang, X.

    2014-11-01

    In the operational orbit determination with optical measurements of space objects, some observations of different objects are tagged as the same object. For this kind of data, the orbit improvement according to the tag is failed because of the composition of multiple objects. A method is proposed from the view of maximum likelihood, and it combines the orbit improvement and identification by employing the EM (Expectation Maximum) method. In the implementation of this method, a robust estimation is also given. Corresponding numerical simulations show that the method is feasible, effective, and convenient.

  6. GRAIL Orbit Determination for the Science Phase and Extended Mission

    NASA Technical Reports Server (NTRS)

    Ryne, Mark; Antreasian, Peter; Broschart, Stephen; Criddle, Kevin; Gustafson, Eric; Jefferson, David; Lau, Eunice; Ying Wen, Hui; You, Tung-Han

    2013-01-01

    The Gravity Recovery and Interior Laboratory Mission (GRAIL) is the 11th mission of the NASA Discovery Program. Its objective is to help answer funda-mental questions about the Moon's internal structure, thermal evolution, and collisional history. GRAIL employs twin spacecraft, which fly in formation in low altitude polar orbits around the Moon. An improved global lunar gravity field is derived from high-precision range-rate measurements of the distance between the two spacecraft. The purpose of this paper is to describe the strategies used by the GRAIL Orbit Determination Team to overcome challenges posed during on-orbit operations.

  7. Comparison of GPS-based Orbit Determination Strategies

    Microsoft Academic Search

    E. Gill; O. Montenbruck

    2004-01-01

    Orbit determination strategies for the on-ground trajectory reconstruction of Low Earth Orbit satellites are compared. The analyzed strategies involve different GPS measurement types comprising navigation solution, single or dual-frequency pseudorange, as well as carrier phase measurements. Furthermore, different processing techniques such as kinematic or reduced-dynamic processing are addressed. Two sample sets of GPS BlackJack measurements are employed, that were obtained

  8. GOCE: precise orbit determination for the entire mission

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  9. An Efficient LEO Precision Orbit Determination For GPS Meteorology

    NASA Astrophysics Data System (ADS)

    Bae, T.; Grejner-Brzezinska, D.

    2006-12-01

    Numerous Low Earth Orbit (LEO) satellites, including TOPEX/POSEIDON, CHAMP and GRACE, have been launched for scientific purposes at altitudes ranging from 400 km to 1300 km. Because of highly complex dynamics in their orbits, coming from the Earth gravity field and the atmospheric drag, accurate and fast LEO orbit determination has been a great research challenge. To support GPS meteorology that requires an accurate orbit in near real-time, an efficient LEO dynamic orbit determination method was developed using the triple-differenced GPS phase observations. The dynamic approach requires careful modeling of the atmospheric drag force which is the most dominant nonconservative force. In addition, the empirical force modeling, which is similar to the stochastic process noise in the reduced-dynamic approach, absorbs most of the remaining unmodeled forces. The two frequencies of the empirical forces, that is, once- and twice-per-revolution, are modeled in this study. Also after a thorough testing of the most suitable size of the arc length for the atmospheric drag parameters, the scaling factors for the drag force are estimated every hour. To test the developed algorithms, 24 hours of CHAMP data on February 15, 2003 were used with the geopotential model of EIGEN2 (degree and order up to 120). The estimated orbit solutions are compared with the published Rapid Science Orbit (RSO), and the SLR residuals are also computed as an independent validation of the orbit solution. In addition to the conventional methods of orbit comparison, new consistency testing method between orbit solutions was suggested and performed in this study. The CHAMP orbit is successfully estimated in this study to support the GPS meteorology using a new method that is precise as well as fast and efficient. With the careful modeling, the dynamic solution shows an agreement within ~8 cm in position and ~0.12 mm/s in velocity of RSO. The computation time of the dynamic solution for the 26-hour arc is 2.5 hours on a general PC platform. The hypothesis testing indicates that the estimated dynamic solution of this study is statistically consistent with the published RSO. Also, the SLR residual test shows that the CHAMP orbit solution estimated in this study is comparable to solutions determined at other analysis centers, such as JPL and GFZ.

  10. Precise orbit determination and rapid orbit recovery supported by time synchronization

    NASA Astrophysics Data System (ADS)

    Guo, Rui; Zhou, JianHua; Hu, XiaoGong; Liu, Li; Tang, Bo; Li, XiaoJie; Wu, Shan

    2015-06-01

    In order to maintain optimal signal coverage, GNSS satellites have to experience orbital maneuvers. For China's COMPASS system, precise orbit determination (POD) as well as rapid orbit recovery after maneuvers contribute to the overall Positioning, Navigation and Timing (PNT) service performance in terms of accuracy and availability. However, strong statistical correlations between clock offsets and the radial component of a satellite's positions require long data arcs for POD to converge. We propose here a new strategy which relies on time synchronization between ground tracking stations and in-orbit satellites. By fixing satellite clock offsets measured by the satellite station two-way synchronization (SSTS) systems and receiver clock offsets, POD and orbital recovery performance can be improved significantly. Using the Satellite Laser Ranging (SLR) as orbital accuracy evaluation, we find the 4-hr recovered orbit achieves about 0.71 m residual root mean square (RMS) error of fit SLR data, the recovery time is improved from 24-hr to 4-hr compared with the conventional POD without time synchronization support. In addition, SLR evaluation shows that for 1-hr prediction, about 1.47 m accuracy is achieved with the new proposed POD strategy.

  11. Evaluation of semiempirical atmospheric density models for orbit determination applications

    NASA Technical Reports Server (NTRS)

    Cox, C. M.; Feiertag, R. J.; Oza, D. H.; Doll, C. E.

    1994-01-01

    This paper presents the results of an investigation of the orbit determination performance of the Jacchia-Roberts (JR), mass spectrometer incoherent scatter 1986 (MSIS-86), and drag temperature model (DTM) atmospheric density models. Evaluation of the models was performed to assess the modeling of the total atmospheric density. This study was made generic by using six spacecraft and selecting time periods of study representative of all portions of the 11-year cycle. Performance of the models was measured for multiple spacecraft, representing a selection of orbit geometries from near-equatorial to polar inclinations and altitudes from 400 kilometers to 900 kilometers. The orbit geometries represent typical low earth-orbiting spacecraft supported by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD). The best available modeling and orbit determination techniques using the Goddard Trajectory Determination System (GTDS) were employed to minimize the effects of modeling errors. The latest geopotential model available during the analysis, the Goddard earth model-T3 (GEM-T3), was employed to minimize geopotential model error effects on the drag estimation. Improved-accuracy techniques identified for TOPEX/Poseidon orbit determination analysis were used to improve the Tracking and Data Relay Satellite System (TDRSS)-based orbit determination used for most of the spacecraft chosen for this analysis. This paper shows that during periods of relatively quiet solar flux and geomagnetic activity near the solar minimum, the choice of atmospheric density model used for orbit determination is relatively inconsequential. During typical solar flux conditions near the solar maximum, the differences between the JR, DTM, and MSIS-86 models begin to become apparent. Time periods of extreme solar activity, those in which the daily and 81-day mean solar flux are high and change rapidly, result in significant differences between the models. During periods of high geomagnetic activity, the standard JR model was outperformed by DTM. Modification of the JR model to use a geomagnetic heating delay of 3 hours, as used in DTM, instead of the 6.7-hour delay produced results comparable to or better than the DTM performance, reducing definitive orbit solution ephermeris overlap differences by 30 to 50 percent. The reduction in the overlap differences would be useful for mitigating the impact of geomagnetic storms on orbit prediction.

  12. Orbit determination and gravity field recovery from tracking data to the Lunar Reconnaissance Orbiter

    NASA Astrophysics Data System (ADS)

    Maier, Andrea; Baur, Oliver

    2015-04-01

    The Lunar Reconnaissance Orbiter (LRO), launched in 2009, is well suited for the estimation of the long wavelengths of the lunar gravity field due to its low altitude of 50 km. Further, the orbit of LRO was polar for two years providing global coverage. The satellite has been primarily tracked via S-band (mainly two-way Doppler range-rates and two-way radiometric ranges) from the dedicated station in White Sands and from the Universal Space Network (USN). Due to the onboard altimeter the orbital precision requirement in the radial direction was rigorously defined as 1m. Because simulation studies before LRO's launch showed that this precision could not be reached with S-band observations alone, it was decided to additionally track LRO via optical laser ranges. It is worthwhile to point out that LRO is the first spacecraft in interplanetary space routinely tracked with optical one-way laser ranges. Gravity field recovery from orbit perturbations is intrinsically related to precise orbit determination. This is why considerable effort was made to find the optimum settings for orbit modeling. For a time span of three months we conducted a series of orbit overlapping tests based on Doppler observations to find the optimum arc length and the optimum set of empirical parameters. The analysis of observation residuals and orbit overlap differences showed that the estimated orbits are most precise when subdividing the time span into 2.5 days and estimating one constant empirical acceleration in along track direction. These settings were then used to analyze 13 months of Doppler data to LRO. The processing of the optical one-way laser was difficult due to the involvement of two non-synchronous clocks in one measurement (one clock at the ground station and one clock onboard LRO). The NASA software GEODYN, which was used for orbit determination and parameter estimation, models the LRO clock using a drift rate (first-order term) and an aging rate (second-order term). It seems, however, that this clock parametrization is not able to fully capture the signature posed on the measurement due to the two clocks. The precision of the orbits based solely on laser ranges is considerably lower compared to the Doppler-only orbits. For this reason, our lunar gravity field solution, which was estimated up to degree and order 60, is based solely on Doppler range-rates.

  13. Orbit determination of space objects based on sparse optical data

    E-print Network

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

    2010-12-23

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  15. Efficient methods for determining precise orbits of low Earth orbiters using the Global Positioning System

    NASA Astrophysics Data System (ADS)

    Bock, Heike

    The main part of this work dealt with the development and evaluation of efficient methods for precise orbit determination of LEOs. A kinematic approach using GPS zero-difference observations was developed (program LEOKIN) and a procedure for generation of dynamic and reduced-dynamic orbits was presented (program SATORB). The procedures have been tested using long GPS data series gathered by two LEO satellites, namely CHAMP and SAC-C. An external comparison was available for the time interval of the eleven days of the IGS CHAMP test campaign (May 20 to 30, 2001). The orbit solution generated at the Technical University of Munich (TUM), Germany, using the Bernese GPS Software was used for this purpose. The TUM-solution is believed to be one of the best solutions contributing to the IGS test campaign. Comparisons with this solution showed that both our best kinematic trajectory and a post-fit reduced-dynamic orbit based on this kinematic solution compare within an RMS error per coordinate (of a Helmert transformation) of about 10 cm with the TUM-solutions. This indicates that LEO orbits with a quality of about 10 cm result from our analyses. The goal of developing efficient methods for precise orbit determination of LEOs is therefore achieved with the zero-difference kinematic point positioning procedure in LEOKIN and the program SATORB to generate reduced-dynamic orbits. It is worth mentioning that the procedure, when using only code observations as input, results in reduced-dynamic orbits with a qualitiy of already 30 cm RMS.

  16. Precise Orbit Determination of BeiDou Navigation Satellite System

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    China has been developing its own independent satellite navigation system since decades. Now the COMPASS system, also known as BeiDou, is emerging and gaining more and more interest and attention in the worldwide GNSS communities. The current regional BeiDou system is ready for its operational service around the end of 2012 with a constellation including five Geostationary Earth Orbit satellites (GEO), five Inclined Geosynchronous Orbit satellites (IGSO) and four Medium Earth orbit (MEO) satellites in operation. Besides the open service with positioning accuracy of around 10m which is free to civilian users, both precise relative positioning, and precise point positioning are demonstrated as well. In order to enhance the BeiDou precise positioning service, Precise Orbit Determination (POD) which is essential of any satellite navigation system has been investigated and studied thoroughly. To further improving the orbits of different types of satellites, we study the impact of network coverage on POD data products by comparing results from tracking networks over the Chinese territory, Asian-Pacific, Asian and of global scale. Furthermore, we concentrate on the improvement of involving MEOs on the orbit quality of GEOs and IGSOs. POD with and without MEOs are undertaken and results are analyzed. Finally, integer ambiguity resolution which brings highly improvement on orbits and positions with GPS data is also carried out and its effect on POD data products is assessed and discussed in detail. Seven weeks of BeiDou data from a ground tracking network, deployed by Wuhan University is employed in this study. The test constellation includes four GEO, five IGSO and two MEO satellites in operation. The three-day solution approach is employed to enhance its strength due to the limited coverage of the tracking network and the small movement of most of the satellites. A number of tracking scenarios and processing schemas are identified and processed and overlapping orbit differences are utilized to qualify the estimated orbits and clocks. 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. For the current tracking network, deploying tracking stations on the eastern side, for example in New Zealand and/or in Hawaii, will significantly reduce along-track biases of GEOs on the same side. The involvement of MEOs and ambiguity-fixing also make the orbits better but rather moderate. Key words: BeiDou, precise orbit determination (POD), tracking network, ambiguity-fixing

  17. Testing A GPS Technique For Precise Low Earth Orbit Determination

    NASA Astrophysics Data System (ADS)

    Colombo, O. L.; Rowlands, D. D.; Chin, D.; Poulouse, S.

    An orbit-determination procedure that combines kinematic and dynamic techniques has been tested using two full days of on-board GPS receiver data from TOPEX and from 21 IGS sites. The resulting orbits agree to better than: 4 cm (rms) in height, 20 cm (rms) in horizontal, and 2 cm bias in each, with the corresponding Goddard Precise Orbit Estimates (POE). These POE, produced by NASA for the TOPEX Geophysical Data Records, are based only on laser tracking data, so they can be used as a totally independent control on GPS-based orbits. The combined procedure has two main steps: (1) A preliminary 24-hour kinematic trajectory, precise to a few meters, is obtained from double-differenced pseudo-range data, using long-baseline kinematic software. A one-day orbit is fitted to this trajectory, at the meter level, using the classical dynamic approach (here, as implemented in GEODYN). (2) The fitted orbit is used to help correct cycle slips in the very precise carrier phase data. The phase data, in turn, is used to get a better kinematic trajectory. A new orbit is dynamically fitted to this trajectory. This orbit is the final product. With the kinematic method, one can process GPS data very efficiently, but the result lacks high accuracy in the case of a fast-moving spacecraft, as the GPS satellites stay in view too briefly to collect enough data from them. With the dynamic approach, it is much easier and efficient to use trajectory coordinates as data, rather than the original GPS observations. and one can filter out very effectively kinematic trajectory errors, to estimate a highly precise orbit. By combining both techniques as outlined here, one can have both the high precision of the dynamic, and the efficient data processing of the kinematic, while being able to use, for each, software al ready at hand.

  18. Filter Strategies for Mars Science Laboratory Orbit Determination

    NASA Technical Reports Server (NTRS)

    Thompson, Paul F.; Gustafson, Eric D.; Kruizinga, Gerhard L.; Martin-Mur, Tomas J.

    2013-01-01

    The Mars Science Laboratory (MSL) spacecraft had ambitious navigation delivery and knowledge accuracy requirements for landing inside Gale Crater. Confidence in the orbit determination (OD) solutions was increased by investigating numerous filter strategies for solving the orbit determination problem. We will discuss the strategy for the different types of variations: for example, data types, data weights, solar pressure model covariance, and estimating versus considering model parameters. This process generated a set of plausible OD solutions that were compared to the baseline OD strategy. Even implausible or unrealistic results were helpful in isolating sensitivities in the OD solutions to certain model parameterizations or data types.

  19. The Effect of Equatorial Spread F on Relative Orbit Determination of GRACE Using Differenced GPS Observations

    Microsoft Academic Search

    Kyoung-Min Roh; Hermann Luehr; Sang-Young Park; Jung-Ho Cho

    2009-01-01

    In this paper, relative orbit of Low Earth Orbit satellites is determined using only GPS measurements and the effects of Equatorial Spread-F (ESF), that is one of biggest ionospheric irregularities, are investigated. First, relative orbit determiation process is constructed based on doubly differenced GPS observations. In order to see orbit determination performance, relative orbit of two GRACE satellites is estimated

  20. (42355) Typhon Echidna: Scheduling observations for binary orbit determination

    NASA Astrophysics Data System (ADS)

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

    2008-09-01

    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)×10 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 76-16+14 and 42-9+8 km, respectively. These numbers give an average bulk density of only 0.44-0.17+0.44 gcm, consistent with very low bulk densities recently reported for two other small transneptunian binaries.

  1. GRAIL Science Data System Orbit Determination : Approach, Strategy, and Performance

    NASA Technical Reports Server (NTRS)

    Fahnestock, Eugene; Asmar, Sami; Park, Ryan; Strekalov, Dmitry; Yuan, Dah-Ning; Harvey, Nate; Kahan, Daniel; Konopliv, Alex; Kruizinga, Gerhard; Oudrhiri, Kamal; Paik, Meegyeong

    2013-01-01

    This paper details orbit determination techniques and strategies employed within each stage of the larger iterative process of preprocessing raw GRAIL data into the gravity science measurements used within gravity field solutions. Each orbit determination pass used different data, corrections to them, and/or estimation parameters. We compare performance metrics among these passes. For example, for the primary mission, the magnitude of residuals using our orbits progressed from approximately or equal to19.4 to 0.077 approximately or equal to m/s for inter-satellite range rate data and from approximately or equal to 0.4 to approximately or equal to 0.1 mm/s for Doppler data.

  2. On-orbit performance of Gravity Probe B orbit determination and drag-free translation control

    NASA Astrophysics Data System (ADS)

    Li, J.; Bencze, W. J.; Debra, D. B.; Galal, K.; Hanuschak, G.; Keiser, G. M.; Mester, J.; Shestople, P.; Small, H.

    The Gravity Probe B GP-B Relativity Mission is a fundamental physics experiment to test Einstein s theory of General Relativity based on observations of gyros in a satellite in a 642 km circular polar orbit around the Earth The GP-B satellite is designed to test two predictions of Einstein s theory the geodetic effect and the frame-dragging effect to an extremely high accuracy Drag-free translation control is implemented to minimize support forces and support induced torques on the gyros One of the four redundant gyros is used as the proof mass and the propellant of the drag-free control system is derived from the exhaust gas boil-off from the helium dewar of the GP-B satellite The GP-B orbit is determined primarily from the measurements of the GPS receiver onboard the satellite and verified independently with the ground-based laser ranging data The force biases in both the attitude and translation control system and the gyro suspension system are also estimated in the ground processing of the orbit data and compensated in the drag-free control system This paper describes the design and implementation of the orbit determination and drag-free translation control system of the GP-B mission and shows the on-orbit performance from the launch on April 20 2004 to the depletion of the helium on September 29 2005

  3. Cassini orbit determination performance during the first eight orbits of the Saturn satellite tour

    NASA Technical Reports Server (NTRS)

    Antreasian, P. G.; Bordi, J. J.; Criddle, K. E.; Ionasescu, R.; Jacobson, R. A.; Jones, J. B.; MacKenzie, R. A.; Meek, M. C.; Pelletier, F. J.; Roth, D. C.; Roundhill, I. M.; Stauch, J.

    2005-01-01

    From June 2004 through July 2005, the Cassini/Huygens spacecraft has executed nine successful close-targeted encounters by three major satellites of the Saturnian system. Current results show that orbit determination has met design requirements for targeting encounters, Hugens descent, and predicting science instrument pointing for targetd satellite encounters. This paper compares actual target dispersion against, the predicte tour covariance analyses.

  4. Orbit Determination for Mars Global Surveyor During Mapping

    NASA Technical Reports Server (NTRS)

    Lemoine, F. G.; Rowlands, D. D.; Smith, D. E.; Pavlis, D. E.; Chinn, D. S.; Luthcke, S. B.; Neumann, G. A.

    1999-01-01

    The Mars Global Surveyor (MGS) spacecraft reached a low-altitude circular orbit on February 4, 1999, after the termination of the second phase of aerobraking. The MGS spacecraft carries the Mars Orbiter Laser Altimeter (MOLA) whose primary goal is to derive a global, geodetically referenced 0.2 deg x 0.2 deg topographic grid of Mars with a vertical accuracy of better than 30 meters. During the interim science orbits in the' Hiatus mission phase (October - November 1997), and the Science Phasing Orbits (March - April, 1998, and June - July 1998) 208 passes of altimeter data were collected by the MOLA instrument. On March 1, 1999 the first ten orbits of MOLA altimeter data from the near-circular orbit were successfully returned from MGS by the Deep Space Network (DSN). Data will be collected from MOLA throughout the Mapping phase of the MCS mission, or for at least one Mars year (687 days). Whereas the interim orbits of Hiatus and SPO were highly eccentric, and altimeter data were only collected near periapsis when the spacecraft was below 785 km, the Mapping orbit of MGS is near circular, and altimeter data will be collected continuously at a rate of 10 Hz. The proper analysis of the altimeter data requires that the orbit of the MGS spacecraft be known to an accuracy comparable to that of the quality of the altimeter data. The altimeter has an ultimate precision of 30 cm on mostly flat surfaces, so ideally the orbits of the MGS spacecraft should be known to this level. This is a stringent requirement, and more realistic goals of orbit error for MGS are ten to thirty meters. In this paper we will discuss the force and measurement modelling required to achieve this objective. Issues in force modelling include the proper modelling of the gravity field of Mars, and the modelling of non-conservatives forces, including the development of a 'macro-model', in a similar fashion to TOPEX/POSEIDON and TDRSS. During Cruise and Aerobraking, the high gain antenna (HGA) was stowed on the +X face of the spacecraft. On March 29, 1999 the HGA will be deployed on a meter long boom which will remain Earth-pointing while the instrument panel (including the MOLA instrument) remains pointed at nadir. The tracking data must be corrected for the regular motion of the high gain antenna with respect to the center of mass, and the success of the MGS determination during Mapping will depend on correctly accounting for this offset in the measurement model.

  5. Implementation of a low-cost, commercial orbit determination system

    NASA Technical Reports Server (NTRS)

    Corrigan, Jim

    1994-01-01

    This paper describes the implementation and potential applications of a workstation-based orbit determination system developed by Storm Integration, Inc. called the Precision Orbit Determination System (PODS). PODS is offered as a layered product to the commercially-available Satellite Tool Kit (STK) produced by Analytical Graphics, Inc. PODS also incorporates the Workstation/Precision Orbit Determination (WS/POD) product offered by Van Martin System, Inc. The STK graphical user interface is used to access and invoke the PODS capabilities and to display the results. WS/POD is used to compute a best-fit solution to user-supplied tracking data. PODS provides the capability to simultaneously estimate the orbits of up to 99 satellites based on a wide variety of observation types including angles, range, range rate, and Global Positioning System (GPS) data. PODS can also estimate ground facility locations, Earth geopotential model coefficients, solar pressure and atmospheric drag parameters, and observation data biases. All determined data is automatically incorporated into the STK data base, which allows storage, manipulation and export of the data to other applications. PODS is offered in three levels: Standard, Basic GPS and Extended GPS. Standard allows processing of non-GPS observation types for any number of vehicles and facilities. Basic GPS adds processing of GPS pseudo-ranging data to the Standard capabilities. Extended GPS adds the ability to process GPS carrier phase data.

  6. Evaluation of semiempirical atmospheric density models for orbit determination applications

    Microsoft Academic Search

    C. M. Cox; R. J. Feiertag; D. H. Oza; C. E. Doll

    1994-01-01

    This paper presents the results of an investigation of the orbit determination performance of the Jacchia-Roberts (JR), mass spectrometer incoherent scatter 1986 (MSIS-86), and drag temperature model (DTM) atmospheric density models. Evaluation of the models was performed to assess the modeling of the total atmospheric density. This study was made generic by using six spacecraft and selecting time periods of

  7. Mars Science Laboratory Orbit Determination Data Pre-Processing

    NASA Technical Reports Server (NTRS)

    Gustafson, Eric D.; Kruizinga, Gerhard L.; Martin-Mur, Tomas J.

    2013-01-01

    The Mars Science Laboratory (MSL) was spin-stabilized during its cruise to Mars. We discuss the effects of spin on the radiometric data and how the orbit determination team dealt with them. Additionally, we will discuss the unplanned benefits of detailed spin modeling including attitude estimation and spacecraft clock correlation.

  8. Automated Orbit Determination System (AODS) requirements definition and analysis

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    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.

  9. Capabilities of a single TDRS to support user orbit determination

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  10. Orbit Determination of Hayabusa during Close Proximity Phase

    NASA Astrophysics Data System (ADS)

    Ikeda, Hitoshi; Kominato, Takashi; Matsuoka, Masatoshi; Ohnishi, Takafumi; Yoshikawa, Makoto

    In September 2005, Hayabusa (MUSES-C) spacecraft successfully had a rendezvous with asteroid 25143 Itokawa. After the arrival, Hayabusa made detailed observations of the asteroid during its rendezvous period (about three months). As the results of various kinds of scientific analysis, a variety of physical parameters of Itokawa (e.g. size, volume, mass, and density) were derived. As to the orbit determination of Hayabusa spacecraft, during the cruise phase, the radiometric (2-way X-band range and Doppler) data were used for analysis. On the other hand, during the approach phase or rendezvous phase, we could obtain the optical data by means of star tracker or optical navigation camera, thus both the radiometric and the optical data were used for orbit determination. The present paper will report on the results of the orbit determination of Hayabusa during the close proximity phase. We will also mention about the mass estimation of Itokawa in this period. The data used in this analysis are 2-way X-band Doppler data and the position data, which were calculated from optical navigation camera's data. As well as the large orbital maneuvers and the gravitational acceleration of Itokawa, the effect of solar radiation pressure, and the effect of attitude control are also taken into account for the calculation. As to the gravity model of Itokawa, a spherical-harmonics gravity model or a polyhedron gravity model are used depending on the situation.

  11. Expected orbit determination performance for the TOPEX/Poseidon mission

    SciTech Connect

    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

    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.

  12. American Institute of Aeronautics and Astronautics Autonomous Lunar Orbit Determination using Star

    E-print Network

    Psiaki, Mark L.

    to determine the six elements of a spacecraft's orbit about the Moon. There already exist autonomous orbitAmerican Institute of Aeronautics and Astronautics 1 Autonomous Lunar Orbit Determination using.Y. 14853-7501 A method has been developed for performing autonomous Lunar orbit determination based

  13. Orbit Determination Support for the Microwave Anisotropy Probe (MAP)

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

    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.

  16. Precise Orbit Determination for a New Horizons KBO

    NASA Astrophysics Data System (ADS)

    Benecchi, Susan

    2013-10-01

    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.

  17. Real-Time Sub-cm Differential Orbit Determination of Two Low-Earth Orbiters with GPS Bias Fixing

    Microsoft Academic Search

    Sien-Chong Wu

    2006-01-01

    An effective technique for real-time differential orbit determination of two low Earth orbiters with GPS bias fixing is formulated. With this technique, only moderate- quality GPS orbit and clock states (e.g., as available in real-time from the NASA Global Differential GPS System with 10-20 cm accuracy) are needed to seed the process. The onboard, real-time orbital states of user satellites

  18. Precision GPS orbit determination strategies for an earth orbiter and geodetic tracking system

    Microsoft Academic Search

    Stephen M. Lichten; Willy I. Bertiger; James S. Border

    1988-01-01

    Data from two 1985 GPS field tests were processed and precise GPS orbits were determined. With a combined carrier phase and pseudorange, the 1314-km repeatability improves substantially to 5 parts in 10 to the 9th (0.6 cm) in the north and 2 parts in 10 to the 8th (2-3 cm) in the other components. To achieve these levels of repeatability

  19. Capabilities of a single TDRS to support user orbit determination

    Microsoft Academic Search

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

    1988-01-01

    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

  20. Orbit Determination Support for the Microwave Anisotropy Probe (MAP)

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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.

  1. Orbit Determination Support for the Microwave Anisotropy Probe (MAP)

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  2. Enhanced orbit determination filter sensitivity analysis: Error budget development

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  3. Preliminary GPS orbit determination results for the Extreme Ultraviolet Explorer

    NASA Technical Reports Server (NTRS)

    Gold, Kenn; Bertiger, Willy; Wu, Sien; Yunck, Tom

    1993-01-01

    A single-frequency Motorola Global Positioning System (GPS) receiver was launched with the Extreme Ultraviolet Explorer mission in June 1992. The receiver utilizes dual GPS antennas placed on opposite sides of the satellite to obtain full GPS coverage as it rotates during its primary scanning mission. A data set from this GPS experiment has been processed at the Jet Propulsion Laboratory with the GIPSY-OASIS 2 software package. The single-frequency, dual antenna approach and the low altitude (approximately 500 km) orbit of the satellite create special problems for the GPS orbit determination analysis. The low orbit implies that the dynamics of the spacecraft will be difficult to model, and that atmospheric drag will be an important error source. A reduced-dynamic solution technique was investigated in which ad hoc accelerations were estimated at each time step to absorb dynamic model error. In addition, a single-frequency ionospheric correction was investigated, and a cycle-slip detector was written. Orbit accuracy is currently better than 5 m. Further optimization should improve this to about 1 m.

  4. Preliminary GPS orbit determination results for the Extreme Ultraviolet Explorer

    NASA Astrophysics Data System (ADS)

    Gold, Kenn; Bertiger, Willy; Wu, Sien; Yunck, Tom

    A single-frequency Motorola Global Positioning System (GPS) receiver was launched with the Extreme Ultraviolet Explorer mission in June 1992. The receiver utilizes dual GPS antennas placed on opposite sides of the satellite to obtain full GPS coverage as it rotates during its primary scanning mission. A data set from this GPS experiment has been processed at the Jet Propulsion Laboratory with the GIPSY-OASIS 2 software package. The single-frequency, dual antenna approach and the low altitude (approximately 500 km) orbit of the satellite create special problems for the GPS orbit determination analysis. The low orbit implies that the dynamics of the spacecraft will be difficult to model, and that atmospheric drag will be an important error source. A reduced-dynamic solution technique was investigated in which ad hoc accelerations were estimated at each time step to absorb dynamic model error. In addition, a single-frequency ionospheric correction was investigated, and a cycle-slip detector was written. Orbit accuracy is currently better than 5 m. Further optimization should improve this to about 1 m.

  5. Gravity Recovery and Interior Laboratory Mission (GRAIL) Orbit Determination

    NASA Technical Reports Server (NTRS)

    You, Tung-Han; Antreasian, Peter; Broschart, Stephen; Criddle, Kevin; Higa, Earl; Jefferson, David; Lau, Eunice; Mohan, Swati; Ryne, Mark; Keck, Mason

    2012-01-01

    Launched on 10 September 2011 from the Cape Canaveral Air Force Station, Florida, the twin-spacecraft Gravity Recovery and Interior Laboratory (GRAIL) has the primary mission objective of generating a lunar gravity map with an unprecedented resolution via the Ka-band Lunar Gravity Ranging System (LGRS). After successfully executing nearly 30 maneuvers on their six-month journey, Ebb and Flow (aka GRAIL-A and GRAIL-B) established the most stringent planetary formation orbit on 1 March 2012 of approximately 30 km x 90 km in orbit size. This paper describes the orbit determination (OD) filter configurations, analyses, and results during the Trans-Lunar Cruise, Orbit Period Reduction, and Transition to Science Formation phases. The maneuver reconstruction strategies and their performance will also be discussed, as well as the navigation requirements, major dynamic models, and navigation challenges. GRAIL is the first mission to generate a full high-resolution gravity field of the only natural satellite of the Earth. It not only enables scientists to understand the detailed structure of the Moon but also further extends their knowledge of the evolutionary histories of the rocky inner planets. Robust and successful navigation was the key to making this a reality.

  6. A demonstration of TDRS orbit determination using differential tracking observables from GPS ground receivers

    Microsoft Academic Search

    Stephen M. Lichten; Charles D. Edwards; Lawrence E. Young; Sumita Nandi; Charles Dunn; Bruce J. Haines

    1993-01-01

    A Global Positioning System (GPS) flight receiver provides a means of precisely determining orbits for satellites in low to moderate altitude orbits. Above 5000 km altitude, however, relatively few GPS satellites are visible. We present a new approach to orbit determination for satellites at higher altitudes. Modification of GPS ground receivers enables a beacon from the orbiter to be tracked

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

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

    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.

  8. (42355) Typhon-Echidna: Scheduling Observations for Binary Orbit Determination

    E-print Network

    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

    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.

  9. (42355) Typhon-Echidna: Scheduling Observations for Binary Orbit Determination

    E-print Network

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

    2008-01-01

    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.

  10. CODE's new solar radiation pressure model for GNSS orbit determination

    NASA Astrophysics Data System (ADS)

    Arnold, D.; Meindl, M.; Beutler, G.; Dach, R.; Schaer, S.; Lutz, S.; Prange, L.; So?nica, K.; Mervart, L.; Jäggi, A.

    2015-05-01

    The Empirical CODE Orbit Model (ECOM) of the Center for Orbit Determination in Europe (CODE), which was developed in the early 1990s, is widely used in the International GNSS Service (IGS) community. For a rather long time, spurious spectral lines are known to exist in geophysical parameters, in particular in the Earth Rotation Parameters (ERPs) and in the estimated geocenter coordinates, which could recently be attributed to the ECOM. These effects grew creepingly with the increasing influence of the GLONASS system in recent years in the CODE analysis, which is based on a rigorous combination of GPS and GLONASS since May 2003. In a first step we show that the problems associated with the ECOM are to the largest extent caused by the GLONASS, which was reaching full deployment by the end of 2011. GPS-only, GLONASS-only, and combined GPS/GLONASS solutions using the observations in the years 2009-2011 of a global network of 92 combined GPS/GLONASS receivers were analyzed for this purpose. In a second step we review direct solar radiation pressure (SRP) models for GNSS satellites. We demonstrate that only even-order short-period harmonic perturbations acting along the direction Sun-satellite occur for GPS and GLONASS satellites, and only odd-order perturbations acting along the direction perpendicular to both, the vector Sun-satellite and the spacecraft's solar panel axis. Based on this insight we assess in the third step the performance of four candidate orbit models for the future ECOM. The geocenter coordinates, the ERP differences w. r. t. the IERS 08 C04 series of ERPs, the misclosures for the midnight epochs of the daily orbital arcs, and scale parameters of Helmert transformations for station coordinates serve as quality criteria. The old and updated ECOM are validated in addition with satellite laser ranging (SLR) observations and by comparing the orbits to those of the IGS and other analysis centers. Based on all tests, we present a new extended ECOM which substantially reduces the spurious signals in the geocenter coordinate z (by about a factor of 2-6), reduces the orbit misclosures at the day boundaries by about 10 %, slightly improves the consistency of the estimated ERPs with those of the IERS 08 C04 Earth rotation series, and substantially reduces the systematics in the SLR validation of the GNSS orbits.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  12. Aiming at a 1-cm Orbit for Low Earth Orbiters: Reduced-Dynamic and Kinematic Precise Orbit Determination

    Microsoft Academic Search

    P. N. A. M. Visser; J. van den Ijssel

    2003-01-01

    The computation of high-accuracy orbits is a prerequisite for the success of Low Earth Orbiter (LEO) missions such as CHAMP, GRACE and GOCE. The mission objectives of these satellites cannot be reached without computing orbits with an accuracy at the few cm level. Such a level of accuracy might be achieved with the techniques of reduced-dynamic and kinematic precise orbit

  13. Orbit/Attitude Determination and Control for the UMRSAT Mission

    NASA Astrophysics Data System (ADS)

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

    2008-08-01

    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.

  14. Error assessment of an autonomous real-time precision orbit determination program for a low-earth-orbit satellite using GPS observation data

    NASA Astrophysics Data System (ADS)

    Jo, Jung Hyun

    2002-09-01

    An autonomous, real-time, precision orbit determination (ARTPOD) program for low-Earth-orbit (LEO) satellites using the Global Positioning System (GPS) is planned and developed. Numerical simulations are used to assess the anticipated accuracy of LEO satellite tracking using GPS observation data. The GPS observation data for a particular LEO satellite, CHAMP (Challenging Mini-satellite Payload), is processed with the ARTPOD program and results are compared with those from a current reference level Precision Orbit Determination (POD) program. A set of gravitational and non-gravitational force model and measurement errors is applied to provide anticipated levels of orbit error in the estimation process. Non-differenced LEO-GPS pseudo measurements are used to improve the GPS data model and the Earth geopotential model. The latter is the dominant error source for LEO Precision Orbit Determination (POD). Several representations of the gravitation model are evaluated to find the optimum model based on two criteria: performance and size of program. A batch filter and an extended Kalman filter are used to provide statistical best state estimates. The design of ARTPOD is evaluated to determine its suitability for autonomous, real-time operation. Results presented show that the batch filter and extended Kalman filter are successfully implemented in ARTPOD. These two filters converged in the worst case scenario based on initial state. The final orbit was estimated within anticipated errors with nominal initial state. Various combinations of initial state and estimate state vector are tested to improve the ARTPOD design. The results by four different methods of obit improvement is shown.

  15. A new procedure for the solution of the classical problem of minimal orbit determination from three lines of sight

    Microsoft Academic Search

    R. H. Gooding

    1996-01-01

    A new method has been developed for obtaining multiple solutions of the classical angles-only initial-orbit-determination problem. The method operates by a higher-order Newton correction of the assumed values for two of the unknown ranges, with the author's universal Lambert algorithm at the heart of the procedure. The observations are permitted to span several revolutions when the orbit is elliptic, and

  16. A New Procedure for the Solution of the Classical Problem of Minimal Orbit Determination from Three Lines of Sight

    Microsoft Academic Search

    R. H. Gooding

    1996-01-01

    A new method has been developed for obtaining multiple solutions of the classical angles-only initial-orbit-determination problem. The method operates by a higher-order Newton correction of the assumed values for two of the unknown ranges, with the author's universal Lambert algorithm at the heart of the procedure. The observations are permitted to span several revolutions when the orbit is elliptic, and

  17. Precise Orbit Determination for a New Horizons KBO

    NASA Astrophysics Data System (ADS)

    Benecchi, Susan

    2014-10-01

    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.

  18. Dynamical Determination of the Innermost Stable Circular Orbit of Binary Neutron Stars

    E-print Network

    Pedro Marronetti; Matthew D. Duez; Stuart L. Shapiro; Thomas W. Baumgarte

    2004-02-20

    We determine the innermost stable circular orbit (ISCO) of binary neutron stars (BNSs) by performing dynamical simulations in full general relativity. Evolving quasiequilibrium (QE) binaries that begin at different separations, we bracket the location of the ISCO by distinguishing stable circular orbits from unstable plunges. We study Gamma=2 polytropes of varying compactions in both corotational and irrotational equal-mass binaries. For corotatonal binaries we find an ISCO orbital angular frequency somewhat smaller than that determined by applying turning-point methods to QE initial data. For the irrotational binaries the initial data sequences terminate before reaching a turning point, but we find that the ISCO frequency is reached prior to the termination point. Our findings suggest that the ISCO frequency varies with compaction but does not depend strongly on the stellar spin. Since the observed gravitational wave signal undergoes a transition from a nearly periodic ``chirp'' to a burst at roughly twice the ISCO frequency, the measurement of its value by laser interferometers (e.g LIGO) will be important for determining some of the physical properites of the underlying stars

  19. Radiation force modeling for ICESat precision orbit determination

    NASA Astrophysics Data System (ADS)

    Webb, Charles Edward

    2007-12-01

    Precision orbit determination (POD) for the Ice, Cloud and land Elevation Satellite (ICESat) relies on an epoch-state batch filter, in which the dynamic models play a central role. Its implementation in the Multi-Satellite Orbit Determination Program (MSODP) originally included a box-and-wing model, representing the TOPEX/Poseidon satellite, to compute solar radiation forces. This "macro-model" has been adapted to the ICESat geometry, and additionally, extended to the calculation of forces induced by radiation reflected and emitted from the Earth. To determine the area and reflectivity parameters of the ICESat macro-model surfaces, a high-fidelity simulation of the radiation forces in low-Earth orbit was first developed, using a detailed model of the satellite, called the "micro-model". In this effort, new algorithms to compute such forces were adapted from a Monte Carlo Ray Tracing (MCRT) method originally designed to determine incident heating rates. After working with the vendor of the Thermal Synthesizer System (TSS) to implement these algorithms, a modified version of this software was employed to generate solar and Earth radiation forces for all ICESat orbit and attitude geometries. Estimates of the macro-model parameters were then obtained from a least-squares fit to these micro-model forces, applying an algorithm that also incorporated linear equality and inequality constraints to ensure feasible solutions. Three of these fitted solutions were selected for post-launch evaluation. Two represented conditions at the start and at the end of the mission, while the third comprised four separate solutions, one for each of the nominal satellite attitudes. In addition, three other sets of macro-model parameters were derived from area-weighted averaging of the micro-model reflectivities. They included solar-only and infrared-only spectral parameters, as well as a set combining these parameters. Daily POD solutions were generated with each of these macro-model sets, for eight-day intervals in four different ICESat mapping campaigns. As a group, the fitted parameters slightly outperformed the averaged parameters, based on a variety of metrics. Their impact on POD accuracy, however, was limited to the sub-millimeter level, as measured by independent satellite laser ranging (SLR) residuals. As a result, no change to the nominal macro-model parameters is recommended.

  20. Galileo orbit determination from launch through the first earth flyby

    NASA Technical Reports Server (NTRS)

    Pollmeier, V. M.; Kallemeyn, P. H.

    1991-01-01

    The data types used in the Galileo orbit determination process and the primary effects on the spacecraft for the first two trajectory legs of the mission are discussed. These types are: two-way coherent Doppler, two-way range, and delta differential one-way range. Attention is given to four primary nongravitational accelerations that affect the Galileo spacecraft: Delta(V) from TCMs, the Delta(V) from attitude updates, the Delta(V) from thruster maintenance events, and solar radiation pressure.

  1. Galileo orbit determination for the Venus and Earth-1 flybys

    NASA Technical Reports Server (NTRS)

    Kallemeyn, P. H.; Haw, R. J.; Pollmeier, V. M.; Nicholson, F. T.; Murrow, D. W.

    1992-01-01

    This paper presents the orbit determination strategy and results in navigating the Galileo spacecraft from launch through its Venus and first earth flybys. Many nongravitational effects were estimated, including solar radiation pressure, small velocity impulses from attitude changes and eight trajectory correction maneuvers. Tracking data consisted of S-Band Doppler and range. The fitting of Doppler was difficult since one of the cpacecraft's two antennas was offset from the spin axis, thus producing the sinusoidal velocity fluctuation seen in the data. Finally, Delta Differential One-way Range data was used during the last three months of the earth approach to help deliver the spacecraft to within desired accuracy.

  2. Orbital period determination in an eclipsing dwarf nova HT Cas

    NASA Astrophysics Data System (ADS)

    B?kowska, Karolina; Olech, Arkadiusz

    2014-09-01

    HT Cassiopeiae was discovered over seventy years ago (Hoffmeister 1943). Unfortunately, for 35 years this object did not receive any attention, until the eclipses of HT Cas were observed by Bond. After a first analysis, Patterson (1981) called HT Cas "a Rosetta stone among dwarf novae". Since then, the literature on this star is still growing, reaching several dozens of publications. We present an orbital period determination of HT Cas during the November 2010 super-outburst, but also during a longer time span, to check its stability.

  3. JASON-1 Precise Orbit Determination (POD)with SLR and DORIS Tracking

    NASA Technical Reports Server (NTRS)

    Zelensky, N. P.; Luthcke, S. B.; Rowlands, D. D.; Beckley, B. D.; Lemoine, Frank G.; Wang, Y. M.; Chinn, D. S.; Williams, T. A.

    2002-01-01

    Jason-1, the TOPEX/POSEIDON (T/P) radar altimeter follow-on, is intended to continue measurement of the ocean surface with the same, if not better accuracy. T/P has demonstrated that, the time variation of ocean topography can be determined with an accuracy of a few centimeters, thanks to the availability of highly accurate orbits based on SLR and DORIS tracking. For verification and cross-calibration, Jason-1, was initially injected into the T/P orbit, flying just 72 seconds ahead of T/P. This configuration lasted over 21 Jason cycles. In mid-August T/P was maneuvered into its final tandem configuration, a parallel groundtrack, in order to improve the combined coverage. Preliminary investigations using cycles 1-9, shown at the June 2002 SWT, indicated that nominal Jason orbits can achieve the 2-3 cm accuracy objective, however several puzzling aspects of SLR and DORIS measurement modeling were also observed. This paper presents recent analysis of Jason SLR+DORIS POD spanning more than 20 cycles, and revisits several of the more puzzling issues, including estimation of the Laser Retroreflector Array (LRA) offset. The accuracy of the orbits and of the measurement modeling are evaluated using several tests, including SLR, DORIS, and altimeter crossover residual analysis, altimeter collinear analysis, and direct comparison with GPS and other orbits. T/P POD results over the same period are used as a reference.

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

    E-print Network

    Psiaki, Mark L.

    they orbit. This system provides autonomy or near autonomy and could be used for gravity recovery at the Moon to recover a gravity model on the far side of the Moon 4 . The planned Lunar Reconnaissance Orbiter mission 6 . One difficulty of gravity/orbit determination systems for orbits about the Moon or about

  5. Fast initialization of a silicon spin qubit via an excited orbital state

    NASA Astrophysics Data System (ADS)

    Simmons, C. B.; Prance, J. R.; van Bael, B. J.; Koh, Teck Seng; Shi, Zhan; Savage, D. E.; Lagally, M. G.; Joynt, R.; Friesen, Mark; Coppersmith, S. N.; Eriksson, M. A.

    2011-03-01

    We present data showing the initialization and measurement of individual electron spins in a silicon quantum dot. Spectroscopy of the electronic excited states of the dot reveals a relatively low-lying excited orbital state that is much more strongly coupled to the reservoir than the ground orbital state. As a function of an applied magnetic field, Zeeman splitting is observed for both the ground and the excited orbital states. By tuning a gate voltage, electron spins can be preferentially loaded into the quantum dot via any of these spin-split orbital states. Loading at either of the excited orbital states is measured to be over an order of magnitude faster than loading at directly into the orbital ground state. We use single-shot readout to measure the spin state of the loaded electrons. We observe two clear peaks in the fraction of spin-up electrons that are loaded, and these peaks correlate with loading through the spin-up ground or excited orbitals.

  6. A method of astronomical autonomous orbit and attitude determinations for satellites

    NASA Astrophysics Data System (ADS)

    Lin-lin, Li; Hui-xian, Sun

    2003-10-01

    A method of realtime autonomous orbit determination for earth satellites using the extended Kalman filtering is proposed. The observed quantities are: the satellite-sun direction vector measured by a sun sensor, the satellite-earth and satellite-moon direction vectors measured by an ultraviolet sensor, and the geocentric distance measured by a radar altimeter. At the same time the satellite attitude to the earth is also determined. Results of our simulation of the autonomous orbit determination show that the precision of the orbit determinations is better than 200 m. The effects of the sampling period, orbital inclination, orbital eccentricity and orbital altitude on the precision of orbit determination are analyzed and compared, and certain principles helpful for improving the precision of orbit determination are suggested.

  7. Aiming at a 1-cm Orbit for Low Earth Orbiters: Reduced-Dynamic and Kinematic Precise Orbit Determination

    Microsoft Academic Search

    P. N. A. M. Visser; J. Van Den Ijssel

    2003-01-01

    The computation of high-accuracy orbits is a prerequisite for the success of Low Earth Orbiter (LEO) missions such as CHAMP,\\u000a GRACE and GOCE. The mission objectives of these satellites cannot be reached without computing orbits with an accuracy at\\u000a the few cm level. Such a level of accuracy might be achieved with the techniques of reduced-dynamic and kinematic precise\\u000a orbit

  8. Filter parameter tuning analysis for operational orbit determination support

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  9. Accuracy assessment of TDRSS-based TOPEX\\/Poseidon orbit determination

    Microsoft Academic Search

    D. H. Oza; D. T. Bolvin; C. M. Cox; M. V. Samii; C. E. Doll

    1995-01-01

    Orbit determination results are obtained for the Ocean Topography Experiment (TOPEX)\\/Poseidon spacecraft by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) using a batch-least-squares estimator available in the Goddard Trajectory Determination System (GTDS) to process Tracking and Data Relay Satellite (TDRS) System (TDRSS) measurements. The GTDS orbit solutions are compared with the definitive Precision Orbit Determination (POD) orbit

  10. Tracking and Data Relay Satellite (TDRS) tracking and orbit determination

    NASA Technical Reports Server (NTRS)

    Teles, J.; Samii, M.; Nakai, Y.

    1986-01-01

    Analysis results were derived using the Goddard Trajectory Determination System to determine the orbit of TDRS-East. A batch weighted least-squares algorithm is used to fit the Bilateration Ranging Transponder system tracking measurements. Six state parameters (position and velocity components) and the solar radiation pressure coefficient are estimated. The solutions are obtained by fitting the data over 34 hr arcs that overlap by 10 hr. Ephemerides are generated over the 34 hr arcs and then compared over the overlapping regions. The position differences indicate the consistency of the solutions and give a measure of their accuracy. The effect of the modeling of perturbative forces (solar radiation pressure, nonspherical geopotential field) on these results are studied. Error analysis is performed using the ORAN program to estimate the effect of force-model errors and measurement-related errors on the TDRS-East ephemeris.

  11. VIIRS On-Orbit Optical Anomaly - Investigation, Analysis, Root Cause Determination and Lessons Learned

    NASA Technical Reports Server (NTRS)

    Iona, Glenn; Butler, James; Guenther, Bruce; Graziani, Larissa; Johnson, Eric; Kennedy, Brian; Kent, Criag; Lambeck, Robert; Waluschka, Eugne; Xiong, Xiaoxiong

    2012-01-01

    A gradual, but persistent, decrease in the optical throughput was detected during the early commissioning phase for the Suomi National Polar-Orbiting Partnership (SNPP) Visible Infrared Imager Radiometer Suite (VIIRS) Near Infrared (NIR) bands. Its initial rate and unknown cause were coincidently coupled with a decrease in sensitivity in the same spectral wavelength of the Solar Diffuser Stability Monitor (SDSM) raising concerns about contamination or the possibility of a system-level satellite problem. An anomaly team was formed to investigate and provide recommendations before commissioning could resume. With few hard facts in hand, there was much speculation about possible causes and consequences of the degradation. Two different causes were determined as will be explained in this paper. This paper will describe the build and test history of VIIRS, why there were no indicators, even with hindsight, of an on-orbit problem, the appearance of the on-orbit anomaly, the initial work attempting to understand and determine the cause, the discovery of the root cause and what Test-As-You-Fly (TAYF) activities, can be done in the future to greatly reduce the likelihood of similar optical anomalies. These TAYF activities are captured in the lessons learned section of this paper.

  12. GPS clock correction estimation for near real-time orbit determination applications

    Microsoft Academic Search

    H. Bock; R. Dach; Y. Yoon; O. Montenbruck

    2009-01-01

    Precise orbit determination for low Earth orbiting (LEO) satellites using the global positioning system (GPS) is usually done in a post-processing mode introducing GPS satellite orbits and clock corrections. Depending on the mission objectives, the latency and required accuracy of precise LEO orbit information can vary significantly. Near real-time (NRT) orbits for certain geodetic missions (e.g. atmospheric sounding or altimetry)

  13. GPS-based Orbit Determination for LEO Using AKF Bidirectional Filter

    Microsoft Academic Search

    Xian-Ping Qin; Yuan-Xi Yang

    2010-01-01

    In the paper, the principle of GPS-based orbit determination for low earth orbiter (LEO) using adaptive Kalman filtering (AKF) is introduced. The difference of AKF with reduced dynamic technique (RDT) in LEO precise orbit determination (POD) is analyzed. The arithmetic of using bidirectional filter to improve AKF and RDT POD is put forward. Adopting AKF bidirectional filter and RDT bidirectional

  14. ERS-1 orbit determination at D-PAF

    NASA Astrophysics Data System (ADS)

    Reigber, Ch.; Massmann, F.-H.; Raimondo, J. C.; Rajasenan, C.; Gerstl, M.

    1994-05-01

    The German Processing and Archiving Facility for ERS-1 (D-PAF) is in change of computing routinely preliminary (PRL) and precise (PRC) orbits. These tasks are performed since the launch of ERS-1 on July 17, 1991. On a weekly basis PRL orbits are computed from laser quick-look and radar altimeter fast-delivery data and disseminated within short time. The PRC orbits are generated after reception of the laser full-rate data. The presentation focuses on the models used in the preliminary and precise orbit generation and puts particular emphasis on the discussion of the orbit quality in the different orbit phases since launch.

  15. Computer-based instruction and reference documentation system for the orbit determination program

    NASA Technical Reports Server (NTRS)

    Hintz, G. R.; Ryne, M.; Watkins, M.; Kenney, M.; Overoye, D.

    2003-01-01

    The Orbit Determination Program set has been used at the Jet Propulsion Laboratory for nearly half a century to enable precision navigation of interplanetary and earth-orbiting missions and to support a myriad of scientific investigations.

  16. Evaluation and modeling of autonomous attitude thrust control for the Geostation Operational Environmental Satellite (GOES)-8 orbit determination

    NASA Technical Reports Server (NTRS)

    Forcey, W.; Minnie, C. R.; Defazio, R. L.

    1995-01-01

    The Geostationary Operational Environmental Satellite (GOES)-8 experienced a series of orbital perturbations from autonomous attitude control thrusting before perigee raising maneuvers. These perturbations influenced differential correction orbital state solutions determined by the Goddard Space Flight Center (GSFC) Goddard Trajectory Determination System (GTDS). The maneuvers induced significant variations in the converged state vector for solutions using increasingly longer tracking data spans. These solutions were used for planning perigee maneuvers as well as initial estimates for orbit solutions used to evaluate the effectiveness of the perigee raising maneuvers. This paper discusses models for the incorporation of attitude thrust effects into the orbit determination process. Results from definitive attitude solutions are modeled as impulsive thrusts in orbit determination solutions created for GOES-8 mission support. Due to the attitude orientation of GOES-8, analysis results are presented that attempt to absorb the effects of attitude thrusting by including a solution for the coefficient of reflectivity, C(R). Models to represent the attitude maneuvers are tested against orbit determination solutions generated during real-time support of the GOES-8 mission. The modeling techniques discussed in this investigation offer benefits to the remaining missions in the GOES NEXT series. Similar missions with large autonomous attitude control thrusting, such as the Solar and Heliospheric Observatory (SOHO) spacecraft and the INTELSAT series, may also benefit from these results.

  17. Evaluation and modeling of autonomous attitude thrust control for the Geostation Operational Environmental Satellite (GOES)-8 orbit determination

    NASA Astrophysics Data System (ADS)

    Forcey, W.; Minnie, C. R.; Defazio, R. L.

    1995-05-01

    The Geostationary Operational Environmental Satellite (GOES)-8 experienced a series of orbital perturbations from autonomous attitude control thrusting before perigee raising maneuvers. These perturbations influenced differential correction orbital state solutions determined by the Goddard Space Flight Center (GSFC) Goddard Trajectory Determination System (GTDS). The maneuvers induced significant variations in the converged state vector for solutions using increasingly longer tracking data spans. These solutions were used for planning perigee maneuvers as well as initial estimates for orbit solutions used to evaluate the effectiveness of the perigee raising maneuvers. This paper discusses models for the incorporation of attitude thrust effects into the orbit determination process. Results from definitive attitude solutions are modeled as impulsive thrusts in orbit determination solutions created for GOES-8 mission support. Due to the attitude orientation of GOES-8, analysis results are presented that attempt to absorb the effects of attitude thrusting by including a solution for the coefficient of reflectivity, C(R). Models to represent the attitude maneuvers are tested against orbit determination solutions generated during real-time support of the GOES-8 mission. The modeling techniques discussed in this investigation offer benefits to the remaining missions in the GOES NEXT series. Similar missions with large autonomous attitude control thrusting, such as the Solar and Heliospheric Observatory (SOHO) spacecraft and the INTELSAT series, may also benefit from these results.

  18. Cassini Orbit Determination Performance (July 2008 - December 2011)

    NASA Technical Reports Server (NTRS)

    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

    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.

  19. Primary Wegener's granulomatosis of the orbital apex with initial optic nerve infiltration.

    PubMed

    Shunmugam, Manoharan; Morley, Ana M S; Graham, Elizabeth; D'Cruz, David; O'Sullivan, Eoin; Malhotra, Raman

    2011-01-01

    Wegener's granulomatosis can involve the orbit and sometimes the optic nerve. This usually occurs as a result of contiguous spread from affected sinuses or extraocular muscles, or from a vasculitic posterior optic neuropathy. However, we present an unusual case of isolated orbital apex infiltrative disease in a patient with known Wegener's granulomatosis. This initially caused painless optic neuropathy and progressed to painful ophthalmoplegia and blindness. Optic nerve biopsy, performed to exclude methotrexate-induced lymphoma, confirmed optic nerve infiltration. The condition was refractory to high-dose pulsed methylprednisolone but the patient gained symptomatic relief from rituximab. Wegener's granulomatosis should be considered in cases of isolated posterior optic neuropathy, and close attention should be placed on imaging the orbital apex. PMID:21281075

  20. 42 CFR 405.928 - Effect of the initial determination.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Effect of the initial determination. 405.928 Section 405.928...INSURANCE FOR THE AGED AND DISABLED Determinations, Redeterminations, Reconsiderations...Medicare (Part A and Part B) Initial Determinations § 405.928 Effect of the...

  1. 28 CFR 301.305 - Initial determination.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...305 Judicial Administration FEDERAL PRISON INDUSTRIES, INC., DEPARTMENT OF JUSTICE INMATE ACCIDENT COMPENSATION ...delegated by the Board of Directors of Federal Prison Industries, Inc., pursuant to 28 CFR 0.99. In determining the claim,...

  2. 28 CFR 301.305 - Initial determination.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...305 Judicial Administration FEDERAL PRISON INDUSTRIES, INC., DEPARTMENT OF JUSTICE INMATE ACCIDENT COMPENSATION ...delegated by the Board of Directors of Federal Prison Industries, Inc., pursuant to 28 CFR 0.99. In determining the claim,...

  3. 13 Years of TOPEX/POSEIDON Precision Orbit Determination and the 10-fold Improvement in Expected Orbit Accuracy

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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.

  4. Precise SAR satellite orbit parameters determination based on Ground Control Points

    Microsoft Academic Search

    Bin Pan; Ling Liu

    2010-01-01

    Aim to solve the georeferencing problem of spaceborne SAR imagery, accounting for the orbit physics model and the impact of the earth perturbations, some description models such as four parameters model and polynomial model could be applied to determine the satellite orbit parameters. However the orbit state vectors solved by 5 satellite state vectors supplied by header file in SAR

  5. Evaluation of Landsat4 orbit determination accuracy using batch least-squares and sequential methods

    Microsoft Academic Search

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

    1993-01-01

    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

  6. Comparison of ERBS orbit determination accuracy using batch least-squares and sequential methods

    Microsoft Academic Search

    D. H. Oza; T. L. Jones; S. M. Fabien; G. D. Mistretta; R. C. Hart; C. E. Doll

    1991-01-01

    The Flight Dynamics Div. (FDD) at NASA-Goddard commissioned a study to develop the Real Time Orbit Determination\\/Enhanced (RTOD\\/E) system as a prototype system for sequential orbit determination of spacecraft on a DOS based personal computer (PC). An overview is presented of RTOD\\/E capabilities and the results are presented of a study to compare the orbit determination accuracy for a Tracking

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

    Microsoft Academic Search

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

    1993-01-01

    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

  8. Precise orbit determination of a maneuvered GEO satellite using CAPS ranging data

    Microsoft Academic Search

    Yong Huang; Xiaogong Hu; Cheng Huang; Qiangwen Yang; Wenhai Jiao

    2009-01-01

    Wheel-off-loadings and orbital maneuvers of the GEO satellite result in additional accelerations to the satellite itself.\\u000a Complex and difficult to model, these time varying accelerations are an important error source of precise orbit determination\\u000a (POD). In most POD practices, only non-maneuver orbital arcs are treated. However, for some applications such as satellite\\u000a navigation RDSS services, uninterrupted orbital ephemeris is demanded,

  9. Kinematic and highly reduced-dynamic LEO orbit determination for gravity field estimation

    Microsoft Academic Search

    A. Jäggi; G. Beutler; H. Bock; U. Hugentobler

    Kinematic positions of low Earth orbiting satellites equipped with spaceborne GPS receivers are widely used as input for subsequent\\u000a gravity field estimation procedures. Positions relying on reduced-dynamic orbit determination, however, are often considered\\u000a as inappropriate for this task, because they depend to some extent on the gravity field model underlying the orbit estimation.\\u000a We review the principles of reduced-dynamic orbit

  10. Dawn Orbit Determination Team: Trajectory Modeling and Reconstruction Processes at Vesta

    NASA Technical Reports Server (NTRS)

    Abrahamson, Matthew J.; Ardito, Alessandro; Han, Dongsuk; Haw, Robert; Kennedy, Brian; Mastrodemos, Nick; Nandi, Sumita; Park, Ryan; Rush, Brian; Vaughan, Andrew

    2013-01-01

    The Dawn spacecraft spent over a year in orbit around Vesta from July 2011 through August 2012. In order to maintain the designated science reference orbits and enable the transfers between those orbits, precise and timely orbit determination was required. Challenges included low-thrust ion propulsion modeling, estimation of relatively unknown Vesta gravity and rotation models, track-ing data limitations, incorporation of real-time telemetry into dynamics model updates, and rapid maneuver design cycles during transfers. This paper discusses the dynamics models, filter configuration, and data processing implemented to deliver a rapid orbit determination capability to the Dawn project.

  11. Improved solution accuracy for TDRSS-based TOPEX\\/Poseidon orbit determination

    Microsoft Academic Search

    C. E. Doll; G. D. Mistretta; R. C. Hart; D. H. Oza; D. T. Bolvin; C. M. Cox; M. Nemesure; D. J. Niklewski; M. V. Samii

    1994-01-01

    Orbit determination results are obtained by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) using a batch-least-squares estimator available in the Goddard Trajectory Determination System (GTDS) and an extended Kalman filter estimation system to process Tracking and Data Relay Satellite (TDRS) System (TDRSS) measurements. GTDS is the operational orbit determination system used by the FDD in support of

  12. First Attempts At Using COSMIC Data For GPS Orbit Determination

    Microsoft Academic Search

    H. Boomkamp

    2006-01-01

    The COSMIC mission represents the first constellation of Low Earth Orbiting satellites with GPS receivers. Although these receivers are typically intended for positioning of the LEO satellites themselves and for collecting GPS occultation measurements, they can also be exploited as orbiting tracking stations for the higher GPS constellation. The LEO working group of the International GNSS Service investigates the potential

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

    NASA Astrophysics Data System (ADS)

    Krisciunas, Kevin

    2010-08-01

    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.

  14. Low-cost autonomous orbit control about Mars: Initial simulation results

    NASA Astrophysics Data System (ADS)

    Dawson, S. D.; Early, L. W.; Potterveld, C. W.; Königsmann, H. J.

    1999-11-01

    Interest in studying the possibility of extraterrestrial life has led to the re-emergence of the Red Planet as a major target of planetary exploration. Currently proposed missions in the post-2000 period are routinely calling for rendezvous with ascent craft, long-term orbiting of, and sample-return from Mars. Such missions would benefit greatly from autonomous orbit control as a means to reduce operations costs and enable contact with Mars ground stations out of view of the Earth. This paper present results from initial simulations of autonomously controlled orbits around Mars, and points out possible uses of the technology and areas of routine Mars operations where such cost-conscious and robust autonomy could prove most effective. These simulations have validated the approach and control philosophies used in the development of this autonomous orbit controller. Future work will refine the controller, accounting for systematic and random errors in the navigation of the spacecraft from the sensor suite, and will produce prototype flight code for inclusion on future missions. A modified version of Microcosm's commercially available High Precision Orbit Propagator (HPOP) was used in the preparation of these results due to its high accuracy and speed of operation. Control laws were developed to allow an autonomously controlled spacecraft to continuously control to a pre-defined orbit about Mars with near-optimal propellant usage. The control laws were implemented as an adjunct to HPOP. The GSFC-produced 50 × 50 field model of the Martian gravitational potential was used in all simulations. The Martian atmospheric drag was modeled using an exponentially decaying atmosphere based on data from the Mars-GRAM NASA Ames model. It is hoped that the simple atmosphere model that was implemented can be significantly improved in the future so as to approach the fidelity of the Mars-GRAM model in its predictions of atmospheric density at orbital altitudes. Such additional work would take the form of solar flux (F10.7) and diurnal density dependencies. The autonomous controller is a-derivative of the proprietary and patented Microcosm Earth-orbiting control methodology which will be implemented on the upcoming Surrey Satellite Technology (SSTL) UoSAT-12 and the NASA EO-1 spacecraft missions. This work was funded by the NASA Jet Propulsion Laboratory under a Phase I SBIR (96.1 07.02 9444) and by internal Microcosm R&D funds as well as earlier supporting work done under a variety of USAF Research Laboratory-sponsored contracts [1, 2, 4, 12].

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  16. Operational Rapid Precise Orbit Determination For The Low Earth Orbiter Champ

    Microsoft Academic Search

    G. Michalak; G. Baustert; R. Koenig; Ch. Reigber

    2002-01-01

    The geophysical satellite CHAMP of the GeoForschungsZentrum Potsdam (GFZ) launched on July 15, 2000, into a 450 km high, near circular, near polar orbit carries a GPS flight receiver. For the support of the atmospheric sounding and ionospheric processors as well as of the magnetic\\/electric field system of the CHAMP Science Data System the Rapid Science Orbit (RSO) is routinely

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

  18. Orbit determination of the Comet Rendezvous/Asteroid Flyby mission - Post-rendezvous phases

    NASA Technical Reports Server (NTRS)

    Miller, James K.; Wood, Lincoln J.; Weeks, Connie J.

    1989-01-01

    Orbit determination during the post-rendezvous phases of the Comet Rendezvous/Asteroid Flyby mission is described. The orbit determination process is discussed, with emphasis placed on optical imaging of landmarks and Doppler tracking. Rotational dynamics are introduced for the cometary nucleus. State estimation errors are given for spacecraft trajectory prediction and cometary nucleus attitude prediction. Estimation errors are also given for parameters that describe the cometary nucleus such as moments of inertia and gravity harmonics. The orbit determination performance in support of science observations while in orbit about the nucleus is described.

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

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

    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.

  20. Dawn Orbit Determination Team: Modeling and Fitting of Optical Data at Vesta

    NASA Technical Reports Server (NTRS)

    Kennedy, Brian; Abrahamson, Matt; Ardito, Alessandro; Haw, Robert; Mastrodemos, Nicholas; Nandi, Sumita; Park, Ryan; Rush, Brian; Vaughan, Andrew

    2013-01-01

    The Dawn spacecraft was launched on September 27th, 2007. Its mission is to consecutively rendezvous with and observe the two largest bodies in the main asteroid belt, Vesta and Ceres. It has already completed over a year's worth of direct observations of Vesta (spanning from early 2011 through late 2012) and is currently on a cruise trajectory to Ceres, where it will begin scientific observations in mid-2015. Achieving this data collection required careful planning and execution from all Dawn operations teams. Dawn's Orbit Determination (OD) team was tasked with reconstruction of the as-flown trajectory as well as determination of the Vesta rotational rate, pole orientation and ephemeris, among other Vesta parameters. Improved knowledge of the Vesta pole orientation, specifically, was needed to target the final maneuvers that inserted Dawn into the first science orbit at Vesta. To solve for these parameters, the OD team used radiometric data from the Deep Space Network (DSN) along with optical data reduced from Dawn's Framing Camera (FC) images. This paper will de-scribe the initial determination of the Vesta ephemeris and pole using a combination of radiometric and optical data, and also the progress the OD team has made since then to further refine the knowledge of Vesta's body frame orientation and rate with these data.

  1. Expected orbit determination performance for the TOPEX\\/Poseidon mission

    Microsoft Academic Search

    R. S. Nerem; Barbara H. Putney; J. A. Marshall; Francis J. Lerch; Erricos C. Pavlis; Steven M. Klosko; Scott B. Luthcke; Girish B. Patel; Ronald G. Williamson; Nikita P. Zelensky

    1993-01-01

    Each of the components required for the computation of precise orbits for the TOPEX\\/Poseidon (T\\/P) spacecraft - gravity field modeling, nonconservative force modeling, and satellite tracking technologies - is examined. The research conducted in the Space Geodesy Branch at Goddard Space Flight Center in preparation for meeting the 13-cm radial orbit accuracy requirement for the T\\/P mission is outlined. New

  2. TERRASAR-X RAPID AND PRECISE ORBIT DETERMINATION

    Microsoft Academic Search

    M. Wermuth; A. Hauschild; O. Montenbruck; A. Jäggi

    TerraSAR-X is a German Synthetic Aperture Radar (SAR) satellite that has been placed into orbit in mid 2007 and is since then collecting SAR imagery on a routine basis. To support the TerraSAR-X navigation needs, the satellite is equipped with two independent GPS receiver systems. The German Space Operation Center is providing several orbit products with different latencies and accuracy

  3. Advanced stellar compass onboard autonomous orbit determination, preliminary performance.

    PubMed

    Betto, Maurizio; Jørgensen, John L; Jørgensen, Peter S; Denver, Troelz

    2004-05-01

    Deep space exploration is in the agenda of the major space agencies worldwide; certainly the European Space Agency (SMART Program) and the American NASA (New Millennium Program) have set up programs to allow the development and the demonstration of technologies that can reduce the risks and the cost of deep space missions. From past experience, it appears that navigation is the Achilles heel of deep space missions. Performed on ground, this imposes considerable constraints on the entire system and limits operations. This makes it is very expensive to execute, especially when the mission lasts several years and, furthermore, it is not failure tolerant. Nevertheless, to date, ground navigation has been the only viable solution. The technology breakthrough of advanced star trackers, like the advanced stellar compass (ASC), might change this situation. Indeed, exploiting the capabilities of this instrument, the authors have devised a method to determine the orbit of a spacecraft autonomously, onboard, and without a priori knowledge of any kind. The solution is robust and fast. This paper presents the preliminary performance obtained during the ground testing in August 2002 at the Mauna Kea Observatories. The main goals were: (1) to assess the robustness of the method in solving autonomously, onboard, the position lost-in-space problem; (2) to assess the preliminary accuracy achievable with a single planet and a single observation; (3) to verify the autonomous navigation (AutoNav) module could be implemented into an ASC without degrading the attitude measurements; and (4) to identify the areas of development and consolidation. The results obtained are very encouraging. PMID:15220158

  4. Real-Time and Post-Processed Orbit Determination and Positioning

    NASA Technical Reports Server (NTRS)

    Bar-Sever, Yoaz E. (Inventor); Bertiger, William I. (Inventor); Dorsey, Angela R. (Inventor); Harvey, Nathaniel E. (Inventor); Lu, Wenwen (Inventor); Miller, Kevin J. (Inventor); Miller, Mark A. (Inventor); Romans, Larry J. (Inventor); Sibthorpe, Anthony J. (Inventor); Weiss, Jan P. (Inventor); Garcia Fernandez, Miquel (Inventor); Gross, Jason (Inventor)

    2015-01-01

    Novel methods and systems for the accurate and efficient processing of real-time and latent global navigation satellite systems (GNSS) data are described. Such methods and systems can perform orbit determination of GNSS satellites, orbit determination of satellites carrying GNSS receivers, positioning of GNSS receivers, and environmental monitoring with GNSS data.

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

    Microsoft Academic Search

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

    1995-01-01

    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

  6. Determination of Eros physical parameters for near Earth asteroid rendezvous orbit phase navigation

    Microsoft Academic Search

    J. K. Miller; P. J. Antreasian; R. W. Gaskell; J. D. Giorgini; C. E. Helfrich; W. M. Owen; B. G. Williams; D. K. Yeomanst

    1999-01-01

    Navigation of the orbit phase of the Near Earth Asteroid Rendezvous (NEAR) mission will require determination of certain physical parameters describing the size, shape, gravity field, attitude and inertial properties of Eros. Prior to launch, little was kno-yn about Eros except for its orbit which could be determined with high precision from ground based telescope observations. Radar bounce and light

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

    NASA Technical Reports Server (NTRS)

    Fuchs, A. J. (editor)

    1979-01-01

    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.

  8. Orbit determination of low-altitude earth satellites using GPS RF Doppler

    Microsoft Academic Search

    S. C. Wu; V. J. Ondrasik

    1982-01-01

    This paper investigates the use of one type of GPS-signal derived measurement, the doubly differenced GPS RF Doppler, in the orbit determination of low-altitude earth satellites. This measurement is simple to make, is insensitive to clock errors and provides a continuous determination of the user satellite orbit. Analysis shows that, with a constellation of 18 GPS satellites and 13 ground

  9. Precise orbit determination for the GRACE mission using only GPS data

    Microsoft Academic Search

    Zhigui Kang; Byron Tapley; Srinivas Bettadpur; John Ries; Peter Nagel; Rick Pastor

    2006-01-01

    The GRACE (gravity recovery and climate experiment) satellites, launched in March 2002, are each equipped with a BlackJack GPS onboard receiver for precise orbit determination and gravity field recovery. Since launch, there have been significant improvements in the background force models used for satellite orbit determination, most notably the model for the geopotential. This has resulted in significant improvements to

  10. Satellite Orbit Determination Using a Single-Channel Global Positioning System Receiver

    Microsoft Academic Search

    Mark L. Psiaki

    2002-01-01

    A proposed satellite orbit determination system has been analyzed, one that uses measurements from a single-channel Global Positioning System (GPS) receiver. The purpose of this study is to predict the likely efficacy of a low-power autonomous orbit determination system. The system processes the pseudo range outputs of the receiver using an extended Kalman filter. The receiver cycles through different GPS

  11. Precise orbit determination for TOPEX/Poseidon using GPS-SST data

    NASA Astrophysics Data System (ADS)

    Kang, Z.; Schwintzer, P.; Reigber, Ch.; Zhu, S. Y.

    The TOPEX/Poseidon (T/P) altimeter satellite launched in August 1992 is equipped with an experimental Global Positioning System (GPS) receiver. The major goal of the GPS experiment is to demonstrate the GPS system for precise orbit determination of low Earth satellites. The GPS-SST data as obtained from the T/P onboard receiver have been processed in a dynamic orbit determination. In addition, the GPS ephemerides and GPS clock parameters as provided by IGS were used as fixed parameters. The orbit accuracy is assessed using a number of tests. These include external comparisons and analysis of data residuals and orbit overlaps. The orbit determination technique has yielded orbits with an estimated accuracy of about 3 cm in the radial component.

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

    NASA Astrophysics Data System (ADS)

    Farahanifar, Mohammad; Assadian, Nima

    2015-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Marr, G.

    2003-01-01

    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.

  14. An evaluation of Global Positioning System data for Landsat-4 orbit determination

    NASA Astrophysics Data System (ADS)

    Fang, B. T.; Seifert, E.

    1985-01-01

    The Navstar Global Positioning System (GPS) navigation data obtained from an experimental GPS receiver/processor package (GPSPAC) onboard the Landsat-4 spacecraft are evaluated for their accuracy and reliability for use in Landsat-4 orbit determination. Different orbit determination scenarios and methods are considered. The parameters estimated include a subset of three Landsat-4 clock parameters and an atmospheric drag coefficient, in addition to the orbital elements. It is found that Landsat-4 orbit solutions based on delta pseudorange data generally agree with the definitive solutions to the 50-meter level.

  15. VOLE POPULATION FLUCTUATIONS: FACTORS THAT INITIATE AND DETERMINE INTERVALS BETWEEN

    E-print Network

    Oli, Madan K.

    VOLE POPULATION FLUCTUATIONS: FACTORS THAT INITIATE AND DETERMINE INTERVALS BETWEEN THEM of the prairie vole (Microtus ochrogaster) in alfalfa, bluegrass, and tallgrass habitats in east-central Illinois across years. Key words: Microtus ochrogaster, population cycles, population fluctuations, prairie vole

  16. New technique for determining the shock initiation sensitivity of explosives

    Microsoft Academic Search

    1977-01-01

    A new technique for determining the shock initiation sensitivity of explosives is described. It involves a flyer plate impinging upon the test explosive to induce initiation of detonation. An electrically exploded foil propels the flyer plate, which is a thin disk of polyimide (Kapton) 1 mm in dia; the charging voltage applied to the capacitor discharge fireset is used to

  17. Dawn Orbit Determination Team : Trajectory Modeling and Reconstruction Processes at Vesta

    NASA Technical Reports Server (NTRS)

    Abrahamson, Matt; Ardito, Alessandro; Han, Don; Haw, Robert; Kennedy, Brian; Mastrodemos, Nicholas; Nandi, Sumita; Park, Ryan; Rush, Brian; Vaughan, Andrew

    2013-01-01

    The NASA Dawn spacecraft was launched on September 27, 2007 on a mission to study the asteroid belt's two largest objects, Vesta and Ceres. It is the first deep space orbiting mission to demonstrate solar-electric ion propulsion, providing the necessary delta-V to enable capture and escape from two extraterrestrial bodies. At this time, Dawn has completed its science campaign at Vesta and is currently on its journey to Ceres, where it will arrive in mid-2015. The spacecraft spent over a year in orbit around Vesta from July 2011 through August 2012, capturing science data during four dedicated orbit phases. In order to maintain the reference orbits necessary for science and enable the transfers between those orbits, precise and timely orbit determination was required. The constraints associated with low-thrust ion propulsion coupled with the relatively unknown a priori gravity and rotation models for Vesta presented unique challenges for the Dawn orbit determination team. While [1] discusses the prediction performance of the orbit determination products, this paper discusses the dynamics models, filter configuration, and data processing implemented to deliver a rapid orbit determination capability to the Dawn project.

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

    Microsoft Academic Search

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

    1993-01-01

    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

  19. Performance of OSC's initial Amtec generator design, and comparison with JPL's Europa Orbiter goals

    SciTech Connect

    Schock, A.; Noravian, H.; Or, C.; Kumar, V.

    1998-07-01

    The procedure for the analysis (with overpotential correction) of multitube AMTEC (Alkali Metal Thermal-to-Electrical Conversion) cells described in Paper IECEC 98-243 was applied to a wide range of multicell radioisotope space power systems. System design options consisting of one or two generators, each with 2, 3, or 4 stacked GPHS (General Purpose Heat Source) modules, identical to those used on previous NASA missions, were analyzed and performance-mapped. The initial generators analyzed by OSC had 8 AMTEC cells on each end of the heat source stack, with five beta-alumina solid electrolyte (BASE) tubes per cell. The heat source and converters in the Orbital generator designs are embedded in a thermal insulation system consisting of Min-K fibrous insulation surrounded by graded-length molybdenum multifoils. Detailed analyses in previous Orbital studies found that such an insulation system could reduce extraneous heat losses to about 10%. For the above design options, the present paper presents the system mass and performance (i.e., the EOM system efficiency and power output and the BOM evaporator and clad temperatures) for a wide range of heat inputs and load voltages, and compares the results with JPL's preliminary goals for the Europa Orbiter mission to be launched in November 2003. The analytical results showed that the initial 16-cell generator designs resulted in either excessive evaporator and clad temperatures and/or insufficient power outputs to meet the JPL-specified mission goals. The computed performance of modified OSC generators with different numbers of AMTEC cells, cell diameters, cell lengths, cell materials, BASE tube lengths, and number of tubes per cell are described in Paper IECEC.98.245 in these proceedings.

  20. The LAGEOS satellites orbital residuals determination and the way to extract gravitational and non-gravitational unmodeled perturbing effects

    Microsoft Academic Search

    D. M. Lucchesi

    2007-01-01

    Long-arc analysis of the orbits of geodetic satellites is a useful way to extract relevant information concerning the Earth structure, as well as to test relativistic gravity in Earth’s surroundings. The physical information is concentrated in the satellite orbital residuals that must be computed from the orbital elements determined during a very precise orbit determination procedure. However, the physical information

  1. The LAGEOS satellites orbital residuals determination and the way to extract gravitational and non-gravitational unmodeled perturbing effects

    Microsoft Academic Search

    D. M. Lucchesi

    2007-01-01

    Long-arc analysis of the orbits of geodetic satellites is a useful way to extract relevant information concerning the Earth structure, as well as to test relativistic gravity in Earth's surroundings. The physical information is concentrated in the satellite orbital residuals that must be computed from the orbital elements determined during a very precise orbit determination procedure. However, the physical information

  2. The LAGEOS satellites orbital residuals determination and the way to extract gravitational and non-gravitational unmodelled perturbing effects

    Microsoft Academic Search

    D. M. Lucchesi

    2006-01-01

    Long-arc analysis of the orbits of geodetic satellites is a useful way to extract relevant information concerning the Earth structure as well as to test relativistic gravity in Earth s surroundings The physical information is concentrated in the satellite orbital residuals that must be extracted from the orbital elements determined during the precise orbit determination procedure However the physical information

  3. The Effect of GPS Ephemeris on the Accuracy of Precise Orbit Determination of LEO Satellite-borne GPS

    Microsoft Academic Search

    Dong-Ju Peng; Bin Wu

    2009-01-01

    The satellite-borne GPS receivers dedicated to precise orbit determination are now being carried by more and more low earth orbit (LEO) satellites and the satellite-borne GPS has become one of the main means for the precise orbit determination of low earth orbit satellites. The accuracy of satellite-borne GPS precise orbit determination depends on the accuracies of the GPS ephemeris and

  4. Evaluation of orbit determination using dual-TDRS tracking

    Microsoft Academic Search

    D. H. Oza; M. Hodjatzadeh; M. S. Radomski; C. E. Doll; C. J. Gramling

    1990-01-01

    This paper describes the results of a study to evaluate the orbit determinatioin of Tracking and Data Relay Satellite System (TDRSS) user spacecraft within the dual-Tracking and Data Relay Satellite (TDRS) environment. Dense TDRSS tracking of the Earth Radiation Budget Satellite (ERBS) was acquired for the period August 16 through 22, 1989. This tracking information was processed to evaluate the

  5. Sub-Centimeter Precision Orbit Determination with GPS for Ocean Altimetry

    Microsoft Academic Search

    Willy Bertiger; Shailen D. Desai; Angie Dorsey; Bruce J. Haines; Nate Harvey; Da. Kuang; Ant Sibthorpe; Jan P. Weiss

    2010-01-01

    We assess the accuracy of JPL's estimated OSTM\\/Jason-2 Global Positioning System (GPS)-determined orbits based on residuals to independent satellite laser ranging (SLR) data, compared with orbits produced by different software from different data (SLR\\/DORIS), Geophysical Data Record version C (GDR-C) orbits, and altimeter crossover tests. All of these tests are consistent with sub-cm radial accuracy: high elevation SLR residual standard

  6. Rapid orbit determination of LEO satellites using IGS clock and ephemeris products

    Microsoft Academic Search

    Oliver Montenbruck; Eberhard Gill; Remco Kroes

    2005-01-01

    Different types of GPS clock and orbit data provided by the International GPS Service (IGS) have been used to assess the accuracy\\u000a of rapid orbit determination for satellites in low Earth orbit (LEO) using spaceborne GPS measurements. To avoid the need\\u000a for reference measurements from ground-based reference receivers, the analysis is based on an undifferenced processing of\\u000a GPS code and

  7. Impact of GPS satellite antenna offsets on GPS-based precise orbit determination

    Microsoft Academic Search

    Z. Kang; B. Tapley; J. Ries; S. Bettadpur; P. Nagel

    2007-01-01

    Since the successful demonstration of GPS-based Precise Orbit Determination (POD) on TOPEX\\/Poseidon in 1992, GPS-based POD for Low-Earth Orbiters (LEO) such as the CHAMP and GRACE satellites has become a popular method. The orbit accuracy of GPS-based POD has been improved from 3cm to 1cm in the radial direction. In order to achieve higher-accuracy results, it is necessary to understand

  8. The impact of GPS ephemeris on the accuracy of precise orbit determination for LEO using GPS

    Microsoft Academic Search

    D. J. Peng; B. Wu

    2008-01-01

    Today more and more Low Earth orbiting satellites (LEOs) of new scientific missions are equipped with a GPS receiver for precise orbit determination (POD), on-board GPS has become one of the main POD approaches. However, the on-board GPS POD accuracy obviously relies on the accuracy of GPS orbit and clock products. Based on the zero-difference dynamic POD approach of SHORDE-III

  9. Evaluation of Landsat-4 orbit determination accuracy using batch least-squares and sequential methods

    NASA Astrophysics Data System (ADS)

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

    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 (TDRS) 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), 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 May 18-24, 1992, timeframe, during which intensive TDRSS tracking data for Landsat-4 were available. During this period, there were two separate orbit-adjust maneuvers on one of the TDRSS spacecraft (TDRS-East) and one small orbit-adjust maneuver for Landsat-4. 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 generally less than 30 meters after the filter had reached steady state.

  10. Evaluation of Landsat-4 orbit determination accuracy using batch least-squares and sequential methods

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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 (TDRS) 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), 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 May 18-24, 1992, timeframe, during which intensive TDRSS tracking data for Landsat-4 were available. During this period, there were two separate orbit-adjust maneuvers on one of the TDRSS spacecraft (TDRS-East) and one small orbit-adjust maneuver for Landsat-4. 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 generally less than 30 meters after the filter had reached steady state.

  11. Comparison of ERBS orbit determination accuracy using batch least-squares and sequential methods

    NASA Technical Reports Server (NTRS)

    Oza, D. H.; Jones, T. L.; Fabien, S. M.; Mistretta, G. D.; Hart, R. C.; Doll, C. E.

    1991-01-01

    The Flight Dynamics Div. (FDD) at NASA-Goddard commissioned a study to develop the Real Time Orbit Determination/Enhanced (RTOD/E) system as a prototype system for sequential orbit determination of spacecraft on a DOS based personal computer (PC). An overview is presented of RTOD/E capabilities and the results are presented of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite System (TDRSS) user spacecraft obtained using RTOS/E on a PC with the accuracy of an established batch least squares system, the Goddard Trajectory Determination System (GTDS), operating on a mainframe computer. RTOD/E was used to perform sequential orbit determination for the Earth Radiation Budget Satellite (ERBS), and the Goddard Trajectory Determination System (GTDS) was used to perform the batch least squares orbit determination. The estimated ERBS ephemerides were obtained for the Aug. 16 to 22, 1989, timeframe, during which intensive TDRSS tracking data for ERBS were available. Independent assessments were made to examine the consistencies of results obtained by the batch and sequential methods. Comparisons were made between the forward filtered RTOD/E orbit solutions and definitive GTDS orbit solutions for ERBS; the solution differences were less than 40 meters after the filter had reached steady state.

  12. Improved solution accuracy for Landsat4 (TDRSS-user) orbit determination

    Microsoft Academic Search

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

    1994-01-01

    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

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

    NASA Technical Reports Server (NTRS)

    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

    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.

  14. A method of autonomous orbit determination for satellite using star sensor

    NASA Astrophysics Data System (ADS)

    Ma, Jianbo; Xu, Jin; Cao, Zhibin

    2005-05-01

    In this paper a method of autonomous orbit determination using star sensor is studied. By building relatively consummate dynamical models which simulate attitude motion of satellite and observation from satellite to background stars, the simulant computation of this method is executed, and it is shown that the method of autonomous orbit determination is feasible. Academic and calculation analyses have been done for the relation between the direction of star sensor with respect to statellite-body coordinate system and the accuracy of autonomous orbit determination.

  15. The SLR Contribution to Precise Orbit Determination in the GPS Era

    Microsoft Academic Search

    Scott B. Luthcke; David D. Rowlands; Frank G. Lemoine

    Precise Orbit Determination (POD) of Low Earth Orbiting (LEO) geodetic satellites has long relied on the high accuracy and robust tracking data provided by the global Satellite Laser Ranging (SLR) network. In fact, for nearly three decades SLR has been the primary tracking data for numerous high-profile geodetic satellites such as LAGEOS and TOPEX\\/Poseidon. Over the past decade significant advances

  16. ORBIT DETERMINATION USING GPS CONSIDERING DIRECT SOLAR RADIATION PRESSURE MODEL FOR THE TOPEX\\/POSEIDON SATELLITE

    Microsoft Academic Search

    Paula Cristiane Pinto Raimundo; Helio Koiti Kuga; Rodolpho Vilhena De Moraes

    Abstract.The main target here is to determine the orbit of an artificial satellite, using signals of the GPS constellation and least squares algorithms through sequential Givens rotations as the method of estimation, with the aim of improving the performance of the orbit estimation process and, at the same time, minimizing the computational procedure cost. Perturbations up to ,high order geopotential

  17. Hybrid precision orbit determination for low altitude satellites by GPS tracking

    Microsoft Academic Search

    Seung-Woo Lee

    2002-01-01

    A numerical simulation study was performed in order to investigate the effects of process noise modeling on state estimates of a Low Earth Orbiting (LEO) satellite in the GPS-based hybrid Precise Orbit Determination (POD) strategy. The use of simulated data enabled the creation of the simulated data with three different correlation types of the unknown forces, which were constant in

  18. Lunar satellite orbit determination analysis and quality assessment from Lunar Prospector tracking data and SELENE simulations

    Microsoft Academic Search

    Sander Goossens; Koji Matsumoto

    2007-01-01

    Low lunar satellite orbit accuracy is assessed by means of the analysis of tracking data residuals, orbit overlap statistics and covariance propagation. A full-scale determination of a degree and order 75 spherical harmonics lunar gravity field model from 3 months of Lunar Prospector tracking data shows the influence of processing strategies for gravity field modelling. Despite large differences in gravity

  19. Shape of the Moon from the Orbiter Determination of its Gravitational Field

    Microsoft Academic Search

    C. L. Goudas; Z. Kopal

    1966-01-01

    AN analysis of the perturbations of the American Orbiter 1, revolving since August 14 in a 200 min orbit close to the Moon, has led to a satisfactory determination of the principal characteristics of the lunar gravitational field1, and it is of interest to compare these with previous predictions based on plausible physical assumptions. In a previous investigation2 one of

  20. Expected orbit determination performance for the TOPEX\\/Poseidon mission

    Microsoft Academic Search

    R. Steven Nerem; Barbara H. Putney; J. Andrew Marshall; Francis J. Lerch; Erricos C. Pavlis; Steven M. Klosko; Scott B. Luthcke; Girish B. Patel; Ronald G. Williamson; Nikita P. Zelensky

    1993-01-01

    The research that has been conducted in the Space Geodesy Branch at NASA\\/Goddard Space Flight Center in preparation for meeting the 13-cm radial orbit accuracy requirement for the TOPEX\\/Poseidon (T\\/P) mission is described. New developments in modeling the Earth's gravitational field and modeling the complex nonconservative forces acting on T\\/P are highlighted. The T\\/P error budget is reviewed, and a

  1. Determination of shuttle orbiter center of gravity from flight measurements

    NASA Technical Reports Server (NTRS)

    Hinson, E. W.; Nicholson, J. Y.; Blanchard, R. C.

    1991-01-01

    Flight measurements of pitch, yaw, and roll rates and the resultant rotationally induced linear accelerations during three orbital maneuvers on Shuttle mission space transportation system (STS) 61-C were used to calculate the actual orbiter center-of-gravity location. The calculation technique reduces error due to lack of absolute calibration of the accelerometer measurements and compensates for accelerometer temperature bias and for the effects of gravity gradient. Accuracy of the technique was found to be limited by the nonrandom and asymmetrical distribution of orbiter structural vibration at the accelerometer mounting location. Fourier analysis of the vibration was performed to obtain the power spectral density profiles which show magnitudes in excess of 10(exp 4) ug (sup 2)/Hz for the actual vibration and over 500 ug (sup 2)/Hz for the filtered accelerometer measurements. The data from this analysis provide a characterization of the Shuttle acceleration environment which may be useful in future studies related to accelerometer system application and zero-g investigations or processes.

  2. Orbit determination of close binary systems using lucky imaging

    NASA Astrophysics Data System (ADS)

    Rica, F. M.; Barrena, R.; Vázquez, G.; Henríquez, J. A.; Hernández, F.

    2012-01-01

    We present relative positions of visual binaries observed in 2009 with the FastCam 'lucky-imaging' camera mounted on the 1.5-m Carlos Sánchez Telescope at the Observatorio del Teide. We obtained 424 CCD observations (averaged in 198 mean relative positions) of 157 binaries with angular separations in the range 0.14-15.40 arcsec, with a median separation of 0.51 arcsec. For a given system, each CCD image represents the sum of the best 10-25 per cent images from 1000-5000 short-exposure frames. Derived internal errors were 7 mas in ? and 1?2 (9 mas) in ?. When comparing to systems with very well known orbits, we find that the rms deviation in ? residuals is 23 mas, while the rms deviation in ? residuals is 0?73/?. We confirmed 18 Hipparcos binaries and we report new companions to BVD 36 A and J 621 B. For binaries with preliminary orbital parameters, the relative radial velocity was estimated as well. We also present four new revised orbits computed for LDS 873, BU 627 A-BC, BU 628 and HO 197 AB. This work discusses the first results on visual binaries using the FastCam lucky-imaging camera.

  3. GPS orbit determination at the National Geodetic Survey

    NASA Technical Reports Server (NTRS)

    Schenewerk, Mark S.

    1992-01-01

    The National Geodetic Survey (NGS) independently generates precise ephemerides for all available Global Positioning System (GPS) satellites. Beginning in 1991, these ephemerides were produced from double-differenced phase observations solely from the Cooperative International GPS Network (CIGNET) tracking sites. The double-difference technique combines simultaneous observations of two satellites from two ground stations effectively eliminating satellite and ground receiver clock errors, and the Selective Availability (S/A) signal degradation currently in effect. CIGNET is a global GPS tracking network whose primary purpose is to provide data for orbit production. The CIGNET data are collected daily at NGS and are available to the public. Each ephemeris covers a single week and is available within one month after the data were taken. Verification is by baseline repeatability and direct comparison with other ephemerides. Typically, an ephemeris is accurate at a few parts in 10(exp 7). This corresponds to a 10 meter error in the reported satellite positions. NGS is actively investigating methods to improve the accuracy of its orbits, the ultimate goal being one part in 10(exp 8) or better. The ephemerides are generally available to the public through the Coast Guard GPS Information Center or directly from NGS through the Geodetic Information Service. An overview of the techniques and software used in orbit generation will be given, the current status of CIGNET will be described, and a summary of the ephemeris verification results will be presented.

  4. Laser ranging network performance and routine orbit determination at D-PAF

    NASA Technical Reports Server (NTRS)

    Massmann, Franz-Heinrich; Reigber, C.; Li, H.; Koenig, Rolf; Raimondo, J. C.; Rajasenan, C.; Vei, M.

    1993-01-01

    ERS-1 is now about 8 months in orbit and has been tracked by the global laser network from the very beginning of the mission. The German processing and archiving facility for ERS-1 (D-PAF) is coordinating and supporting the network and performing the different routine orbit determination tasks. This paper presents details about the global network status, the communication to D-PAF and the tracking data and orbit processing system at D-PAF. The quality of the preliminary and precise orbits are shown and some problem areas are identified.

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

    NASA Astrophysics Data System (ADS)

    Adhya, Sima

    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.

  6. Spin parameters of Low Earth Orbiting satellites Larets and Stella determined from Satellite Laser Ranging data

    NASA Astrophysics Data System (ADS)

    Kucharski, D.; Lim, H.-C.; Kirchner, G.; Koidl, F.

    2014-01-01

    Satellite Laser Ranging (SLR) measurements contain information about the spin parameters of the fully passive, geodetic satellites. In this paper we spectrally analyze the SLR data of 5 geodetic satellites placed on the Low Earth Orbits: GFZ-1, WESTPAC, Larets, Starlette, Stella, and successfully retrieve the frequency signal from Larets and Stella only. The obtained signals indicate an exponential increase of the spin period of Larets: T = 0.860499·exp(0.0197066·D) [s], and Stella: T = 13.5582·exp(0.00431232·D) [s], where D is in days since launch. The initial spin periods calculated from the first month of the SLR observations are: Larets: Tinitial = 0.8239 s, Stella: Tinitial = 13.2048 s. Analysis of the apparent effects indicates the counter-clockwise spin direction of the satellites. The twice more heavy Stella lost its rotational energy more than four times slower than Larets. Fitting the spin model to the observed spin trends allows determination of the spin axis orientation evolution for Larets and Stella before their rotational period becomes equal to the orbital period.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  8. Determining Mars parking orbits which ensure tangential periapsis burns at arrival and departure

    NASA Technical Reports Server (NTRS)

    Desai, Prasun N.; Buglia, James J.

    1992-01-01

    A method is presented which finds Mars parking orbits which allow tangential periapsis burns at both arrival and departure. This method accounts for the actual geometry at both arrival and departure between the hyperbolic asymptotes and the orbital plane, along with the precession effects caused by the oblateness of Mars. Thus, realistic Delta-V values (and hence initial low-earth orbit masses) are obtained for these orbits. The results obtained from the present method compare very well with a trajectory integration program while only requiring CPU times of about one minute. Therefore, due to the computational efficiency and accuracy, the present method would be an ideal tool to use in preliminary mission design, since it provides the opportunity to incorporate realistic Mars parking orbits effects.

  9. Precise orbit determination for the FORMOSAT-3/COSMIC satellite mission using GPS

    NASA Astrophysics Data System (ADS)

    Hwang, Cheinway; Tseng, Tzu-Pang; Lin, Tingjung; Švehla, Dražen; Schreiner, Bill

    2009-05-01

    The joint Taiwan-US mission FORMOSAT-3/ COSMIC (COSMIC) was launched on April 17, 2006. Each of the six satellites is equipped with two POD antennas. The orbits of the six satellites are determined from GPS data using zero-difference carrier-phase measurements by the reduced dynamic and kinematic methods. The effects of satellite center of mass (COM) variation, satellite attitude, GPS antenna phase center variation (PCV), and cable delay difference on the COSMIC orbit determination are studied. Nominal attitudes estimated from satellite state vectors deliver a better orbit accuracy when compared to observed attitude. Numerical tests show that the COSMIC COM must be precisely calibrated in order not to corrupt orbit determination. Based on the analyses of the 5 and 6-h orbit overlaps of two 30-h arcs, orbit accuracies from the reduced dynamic and kinematic solutions are nearly identical and are at the 2-3 cm level. The mean RMS difference between the orbits from this paper and those from UCAR (near real-time) and WHU (post-processed) is about 10 cm, which is largely due to different uses of GPS ephemerides, high-rate GPS clocks and force models. The kinematic orbits of COSMIC are expected to be used for recovery of temporal variations in the gravity field.

  10. Dawn Orbit Determination Team: Trajectory and Gravity Prediction Performance During Vesta Science Phases

    NASA Technical Reports Server (NTRS)

    Kennedy, Brian; Abrahamson, Matt; Ardito, Alessandro; Han, Dongsuk; Haw, Robert; Mastrodemos, Nicholas; Nandi, Sumita; Park, Ryan; Rush, Brian; Vaughan, Andrew

    2013-01-01

    The Dawn spacecraft was launched on September 27th, 2007. Its mission is to consecutively rendezvous with and observe the two largest bodies in the asteroid belt, Vesta and Ceres. It has already completed over a year's worth of direct observations of Vesta (spanning from early 2011 through late 2012) and is currently on a cruise trajectory to Ceres, where it will begin scientific observations in mid-2015. Achieving this data collection required careful planning and execution from all spacecraft teams. Dawn's Orbit Determination (OD) team was tasked with accurately predicting the trajectory of the Dawn spacecraft during the Vesta science phases, and also determining the parameters of Vesta to support future science orbit design. The future orbits included the upcoming science phase orbits as well as the transfer orbits between science phases. In all, five science phases were executed at Vesta, and this paper will describe some of the OD team contributions to the planning and execution of those phases.

  11. Precise orbit determination of low-Earth satellites using SST data

    Microsoft Academic Search

    Z. Kang; P. Schwintzer; Ch. Reigber; S. Y Zhu

    1997-01-01

    The Satellite-to-Satellite Tracking (SST) in the high-low and\\/or low-low configuration is presently considered as being the most promising method for precise orbit determination and global gravity field recovery. Particularly, the use of the GPS system for orbit determination in the high-low configuration has been extensively studied and successfully tested on TOPEX\\/Poseidon. Recently, many space missions (e.g. CHAMP, STEP) have shown

  12. Precise orbit determination for TOPEX\\/Poseidon using GPS-SST data

    Microsoft Academic Search

    Z. Kang; P. Schwintzer; Ch. Reigber; S. Y. Zhu

    1995-01-01

    The TOPEX\\/Poseidon (T\\/P) altimeter satellite launched in August 1992 is equipped with an experimental Global Positioning System (GPS) receiver. The major goal of the GPS experiment is to demonstrate the GPS system for precise orbit determination of low Earth satellites. The GPS-SST data as obtained from the T\\/P onboard receiver have been processed in a dynamic orbit determination. In addition,

  13. Landsat4 (TDRSS-user) orbit determination using batch least-squares and sequential methods

    Microsoft Academic Search

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

    1992-01-01

    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

  14. An evaluation of Global Positioning System data for Landsat4 orbit determination

    Microsoft Academic Search

    B. T. Fang; E. Seifert

    1985-01-01

    The Navstar Global Positioning System (GPS) navigation data obtained from an experimental GPS receiver\\/processor package (GPSPAC) onboard the Landsat-4 spacecraft are evaluated for their accuracy and reliability for use in Landsat-4 orbit determination. Different orbit determination scenarios and methods are considered. The parameters estimated include a subset of three Landsat-4 clock parameters and an atmospheric drag coefficient, in addition to

  15. Satellite orbit determination using triple-differenced GPS carrier phase in pure kinematic mode

    Microsoft Academic Search

    S. H. Byun

    2003-01-01

    .  ?A new algorithm and computer program, KODAC (Kinematic Orbit Determination And Comparison), was developed for precise satellite\\u000a orbit determination using a kinematic approach with the ionospheric-free triple-differenced (TD) global positioning system\\u000a (GPS) carrier phase as the main observable. Epoch-by-epoch satellite positions are estimated by assuming that the GPS satellite\\u000a ephemerides, ground station positions, and the time series of wet tropospheric

  16. Precise Orbit Determination for the GEOSAT Follow-On Spacecraft

    NASA Technical Reports Server (NTRS)

    Lemoine, Frank G.; Rowlands, David D.; Zelensky, Nikita P.; Luthcke, Scott B.; Cox, Christopher M.; Marr, Gregory C.

    1999-01-01

    The US Navy's GEOSAT Follow-On spacecraft was launched on February 10, 1998 with its primary mission objective to map the oceans using a radar altimeter. The spacecraft tracking complement consists of GPS receivers, a laser retroreflector and Doppler beacons. Since the GPS receivers have not yet returned reliable data, the only means of providing high-quality precise orbits has been though satellite laser ranging (SLR). SLR has tracked the spacecraft since April 22, 1998, and an average of 7 passes per day have been obtained from US and foreign stations. Since the predicted radial orbit error due to the gravity field is only two to three cm, the largest contributor to the high SLR residuals (10 cm) is the mismodelling of the non-conservative forces. The SLR residuals show a clear correlation with beta prime (solar elevation) angle, peaking in mid-August 1998 when the beta prime angle reached -80 to -90 degrees. We report in this paper on the analysis of the GFO tracking data (SLR, Doppler, and if available GPS) using GEODYN, and on the tuning of the non-conservative force model and the gravity model using these data.

  17. Orbit Determination of Mixed Observations of Multiple Objects1,2

    NASA Astrophysics Data System (ADS)

    Xin, WANG

    2015-04-01

    In the conventional orbit determination with optical measurements of space objects, some observations of different objects may be marked as the same object. For this kind of data, the process of orbit determination will be failed to converge or completely erroneous because of the composition of multiple objects. Here, a method is proposed from the viewing point of maximum likelihood, which combines the orbit improvement and object identification by employing the EM (Expectation Maximum) method, and in the implementation of this method, a robust estimation will be given. Corresponding numerical simulations indicate that this method is feasible, effective, and convenient.

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

    NASA Technical Reports Server (NTRS)

    Wu, Jiun-Tsong; Yunck, Thomas P.

    1992-01-01

    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.

  19. Determination of the passive attitude motion of the "Mir" orbital station, based on magnetic field strength measurement data.

    NASA Astrophysics Data System (ADS)

    Sarychev, V. A.; Sazonov, V. V.; Belyaev, M. Yu.; Efimov, N. I.; Lapshina, I. L.

    1995-02-01

    The technique is described for determining the passive attitude motion of the "Mir" orbital station by means of processing onboard measurements of the Earth's magnetic field strength vector. The measurement data, collected on a time interval of about two hours, are processed jointly by means of the least squares method using the integration of the station attitude motion equations. The estimations of initial conditions of the attitude motion and of aerodynamic parameters are obtained as a result of such processing. Possibilities are foreseen for estimating the station's tensor of inertia and for eliminating a constant error component from measurement data. Examples are given to determine the real passive motion of the station.

  20. Study of geopotential error models used in orbit determination error analysis

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

  1. Orbit determination with the two-body integrals. II

    NASA Astrophysics Data System (ADS)

    Gronchi, G. F.; Farnocchia, D.; Dimare, L.

    2011-07-01

    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 by radar observations. We write polynomial equations for this problem, which can be solved 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. This paper continues the research started in Gronchi et al. (Celest. Mech. Dyn. Astron. 107(3):299-318, 2010), where the angular momentum and the energy integrals were used. The use of 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.

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

    NASA Astrophysics Data System (ADS)

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

    1994-05-01

    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.

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

    ERIC Educational Resources Information Center

    O'Brien, John

    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…

  4. Precise orbit determination of low-earth satellites using SST data

    NASA Astrophysics Data System (ADS)

    Kang, Z.; Schwintzer, P.; Reigber, Ch.; Zhu, S. Y.

    The Satellite-to-Satellite Tracking (SST) in the high-low and/or low-low configuration is presently considered as being the most promising method for precise orbit determination and global gravity field recovery. Particularly, the use of the GPS system for orbit determination in the high-low configuration has been extensively studied and successfully tested on TOPEX/Poseidon. Recently, many space missions (e.g. CHAMP, STEP) have shown increased interest in implementing GPS-based orbit determination schemes. The along track orbit accuracy in high-low case is not good. To improve this accuracy, we have investigated the orbit determination using both the high-low SST observations between GPS and low-Earth satellites and the low-low SST observations between low-Earth satellites. The study and analyses are based on a deterministic simulation approach. The simulated data between GPS and low-Earth satellites are carrier phases and pseudoranges. The range and range rate between low-Earth satellite are simulated. This paper presents results of an orbit determination study for satellites at 500 km altitude as an example.

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

    NASA Astrophysics Data System (ADS)

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

    1993-02-01

    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.

  6. LEO range-sum data simulation method and multi-LEO combined orbit determination modeling with its weighting algorithm

    Microsoft Academic Search

    Deyong Zhao; Hongmei Yu

    2010-01-01

    For multi-LEO orbit determination based on Bi-satellite Positioning System (BPS), trajectory error of positioning satellites becomes bottle-neck which improves orbit determination precision of LEOs, so we can take combined orbit determination strategy of BPS and user satellites (LEOs) to ameliorate precision. This paper constructs a basic method of range sum observation data simulation for single Low Earth Orbit (LEO) precise

  7. U.S. initiatives in the international effort to mitigate the orbital debris environment

    Microsoft Academic Search

    George M. Levin

    1996-01-01

    Following release of the 1989 'Report on Orbital Debris' by the Interagency Group (Space) for the National Security Council, NASA undertook a series of extensive bilateral discussions with the major spacefaring nations on the topic of orbital debris. These discussions led to a greater understanding of both the cause and the effect of orbital debris. As a result of these

  8. Initial data for binary black holes in quasi-circular orbit: The conformal thin-sandwich puncture method

    NASA Astrophysics Data System (ADS)

    Hannam, Mark D.

    Numerical relativists have been trying to simulate astrophysically realistic binary black hole collisions for over fifteen years. It is believed that prior to collision the two black holes will be in a slowly decaying circular orbit. Any simulation begins with initial data, but it is not clear whether the orbits represented by current initial data for very close black holes are quasi-stable or even quasi-circular. To construct initial data we must make choices for freely-specifiable quantities and choose boundary conditions. All of these choices should be compatible with the physical system we wish to describe. The physical significance of the freely-specifiable data in York's conformal thin-sandwich (CTS) decomposition is clearer than in previous decompositions of the initial value equations of general relativity. The CTS system has already been used to construct data for quasi-equilibrium binary black hole configurations. These implementations used excision methods, which require boundary conditions on the excision surface. An alternative method that avoids inner boundary conditions is Brandt and Brugmann's puncture method. I combine the CTS decomposition and the puncture method. I show that this method is numerically feasible, but that it may not be possible to identify which of the resulting data sets represent binary black holes in quasi-circular orbits. I also consider two methods for locating quasi-circular orbits, the effective-potential and mass-comparison methods. I find that both methods agree when applied to CTT puncture initial data sets.

  9. Summary of the orbit determination of NOZOMI spacecraft for all the mission period

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Makoto; Kawaguchi, Jun'Ichiro; Yamakawa, Hiroshi; Kato, Takaji; Ichikawa, Tsutomu; Ohnishi, Takafumi; Ishibashi, Shiro

    2005-07-01

    Japanese first Mars explorer NOZOMI, which was launched in July 1998, suffered several problems during the operation period of more than five years. It could have reached near Mars at the end of 2003, but it was not put into the orbit around Mars. Although NOZOMI was not able to execute its main mission, it provided us a lot of good experiences from the point of the orbit determination of spacecraft. One of the most difficult works was the orbit determination for the period without the telemetry. In this period, for the most of the time the high gain antenna did not point to the earth because of a constraint of the attitude. Therefore, the quality of the tracking data was not good, and for some period it was impossible to get the tracking data at all. Under such critical condition, we managed to get the solution of the orbit, and in a near-miraculous way, we were able to control NOZOMI and execute two earth swingbys successfully. Other issues related to the orbit determination are the spin modulation, the solar radiation pressure, the small force related to the attitude change, and the solar conjunction. We tried to solve these issues by the conventional way using range and Doppler data. However, we also tried the new method, that is the orbit determination by using the Delta-VLBI method (VLBI: Very Long Baseline Interferometry). In addition to this, we tried optical observations of NOZOMI at the earth swingbys.

  10. Contribution of SLR tracking data to GNSS orbit validation and determination

    NASA Astrophysics Data System (ADS)

    Urschl, C.; Beutler, G.; Gurtner, W.; Hugentobler, U.; Schaer, S.

    GNSS orbits derived from microwave tracking data may be validated using SLR range measurements Recent validation results show mean range residuals of several centimeters for both GPS and GLONASS satellites as well as significant seasonal variations for the two GPS satellites that are equipped with retro-reflector arrays These differences may be assigned to orbit or observation modeling problems or both In order to study this issue we analyze several time series of SLR range residuals Dependencies on the SLR sites and the observation scenario are discussed GNSS microwave orbits differing in arc-length in orbit modeling and in attitude modeling are compared The resulting orbit differences show periodic variations too which are correlated with eclipsing seasons and the sun s elevation above the orbital plane Moreover we address the question whether it would make sense to perform a combined analysis of microwave and SLR data for GNSS orbit determination With the available low number of SLR observations no significant improvement of the orbit accuracy can be found A variance-covariance analysis shows an improvement of the situation if continuous SLR tracking data of a very small number of globally distributed SLR sites were available

  11. Onboard orbit determination using GPS observations based on the unscented Kalman filter

    NASA Astrophysics Data System (ADS)

    Choi, Eun-Jung; Yoon, Jae-Cheol; Lee, Byoung-Sun; Park, Sang-Young; Choi, Kyu-Hong

    2010-12-01

    Spaceborne GPS receivers are used for real-time navigation by most low Earth orbit (LEO) satellites. In general, the position and velocity accuracy of GPS navigation solutions without a dynamic filter are 25 m (1 ?) and 0.5 m/s (1 ?), respectively. However, GPS navigation solutions, which consist of position, velocity, and GPS receiver clock bias, have many abnormal excursions from the normal error range for space operation. These excursions lessen the accuracy of attitude control and onboard time synchronization. In this research, a new onboard orbit determination algorithm designed with the unscented Kalman filter (UKF) was developed to improve the performance. Because the UKF is able to obtain the posterior mean and covariance accurately by using the second-order Taylor series expansion through the sampled sigma points that are propagated by using the true nonlinear system, its performance can be better than that of the extended Kalman filter (EKF), which uses the linearized state transition matrix to predict the covariance. The dynamic models for orbit propagation applied perturbations due to the 40 × 40 geo-potential, the gravity of the Sun and Moon, solar radiation pressure, and atmospheric drag. The 7(8)th-order Runge-Kutta numerical integration was applied for orbit propagation. Two types of observations, navigation solutions and C/A code pseudorange, can be used at the user's discretion. The performances of the onboard orbit determination were verified using real GPS data of the CHAMP and KOMPSAT-2 satellites. The results of the orbit determination were compared with the precision orbit ephemeris (POE) of the CHAMP and KOMPSAT-2 satellites. The comparison of the orbit determination results using EKF and UKF shows that orbit determination using the UKF yields better results than that using the EKF. In addition, the estimation of the accuracy using the C/A code pseudorange is better than that using the navigation solutions. The absolute position and velocity accuracies of the UKF using GPS C/A code pseudorange were 12.098 m and 0.0159 m/s in the case of the CHAMP satellite, and 8.172 m and 0.0085 m/s in the case of the KOMPSAT-2 satellite. Moreover, the abnormal excursions of navigation solutions can be eliminated. These results verify that onboard orbit determination using GPS C/A code pseudorange, which is based on the UKF can provide more stable and accurate orbit information in the spaceborne GPS receiver.

  12. Long arc orbit determination for Mariner 9 using combined radio and optical data types

    NASA Technical Reports Server (NTRS)

    Born, G. H.; Mohan, S. N.

    1974-01-01

    Results of postflight orbit determination for the Mariner 9 trajectory (Mariner-Mars 1971 mission) using Doppler data combined with optical data in the form of TV photographs of the natural satellites and Mars' surface features. It is shown that the combined data yield a solution which is a factor of 3 to 5 better than that obtained from Doppler-only solutions for the node of the orbit relative to the plane perpendicular to the Earth-Mars line. Consequently, these optical data types have a demonstrated potential to significantly improve planetary orbiter navigation accuracies.

  13. Phase center modeling for LEO GPS receiver antennas and its impact on precise orbit determination

    Microsoft Academic Search

    Adrian Jäggi; R. Dach; O. Montenbruck; U. Hugentobler; H. Bock; G. Beutler

    2009-01-01

    Most satellites in a low-Earth orbit (LEO) with demanding requirements on precise orbit determination (POD) are equipped with\\u000a on-board receivers to collect the observations from Global Navigation Satellite systems (GNSS), such as the Global Positioning\\u000a System (GPS). Limiting factors for LEO POD are nowadays mainly encountered with the modeling of the carrier phase observations,\\u000a where a precise knowledge of the

  14. Zero-difference and single-difference precise orbit determination for LEO using GPS

    Microsoft Academic Search

    DongJu Peng; Bin Wu

    2007-01-01

    Various methods for precise orbit determination (POD) of low earth orbiters (LEO) are briefly introduced in this paper. Based\\u000a on the software named SHORD-III developed by our institute, single-difference (SD) and zero-difference (ZD) dynamic POD based\\u000a on LEO carrying an on-board GPS receiver is mainly discussed. The approaches are tested using real GRACE data (November 5–25,\\u000a 2002) and independently validated

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

    NASA Technical Reports Server (NTRS)

    Shank, D.; Pajerski, R.

    1986-01-01

    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.

  16. 42 CFR 405.926 - Actions that are not initial determinations.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...that are not initial determinations and are not appealable...to— (a) Any determination for which CMS has...ALJ's, or MAC's determination or decision to reopen...reopen an initial determination, redetermination...decision; (m) Determinations that CMS or...

  17. Improving FermiI Orbit Determination and Prediction in an Uncertain Atmospheric Drag Environment

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

    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 spacecrafts 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.

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

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

    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.

  19. 19 CFR 210.66 - Initial determination concerning temporary relief; Commission action thereon.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...investigation, unless the Commission modifies, reverses, or sets aside the initial determination...c) The Commission will not modify, reverse, or set aside an initial determination...the Commission determines to modify, reverse, or set aside the initial...

  20. 19 CFR 210.66 - Initial determination concerning temporary relief; Commission action thereon.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...investigation, unless the Commission modifies, reverses, or sets aside the initial determination...c) The Commission will not modify, reverse, or set aside an initial determination...the Commission determines to modify, reverse, or set aside the initial...

  1. Particle filter using a new resampling approach applied to LEO satellite autonomous orbit determination with a magnetometer

    NASA Astrophysics Data System (ADS)

    Wu, Jinjie; Liu, Kun; Wei, Jingbo; Han, Dapeng; Xiang, Junhua

    2012-12-01

    Particle filter (PF) is widely used in nonlinear and non-Gaussian systems. Resampling is one of the significant steps in PF. However, PF using conventional resampling approaches may lead to divergent solutions because of the degeneracy phenomenon or sample impoverishment associated with a multidimensional system. In this article, an efficient alternative to conventional resampling approaches, called adaptive partial systematic resampling (APSR) with Markov chain Monte Carlo move and intelligent roughening is proposed for satellite orbit determination using a magnetometer. The results of the new resampling approach are compared with conventional resampling approaches and with unscented Kalman filter (UKF) for various initial errors in position and velocity, measurement sampling periods, and measurement noises to evaluate and verify the performance of the new resampling approach. The results of the new resampling approach in all cases are significantly better than the results of conventional resampling approaches. The velocity accuracy of the orbit determination of APSR is slightly poorer than UKF for relatively small initial errors, and small Gaussian measurement noise. However, the proposed approach yields more robust and stable convergence than UKF under large initial errors, long measurement sampling period, large Gaussian measurement noise, or non-Gaussian noise.

  2. The Skads Survey : Bias Determination And Orbital Distribution

    Microsoft Academic Search

    Robert Jedicke; B. Gladman; D. Davis

    2006-01-01

    The Sub-Kilometer Asteroid Diameter Survey (SKADS) (see Davis et al. 2006, this conference) covered 8.6 square degrees of sky and detected 1277 main belt asteroids to a limiting magnitude (at which the efficiency is 50%) of roughly R=23. By planting synthetic objects directly into the images we have determined the detection efficiency of moving objects as a function of their

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

    PubMed Central

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

    2013-01-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    The Solar Dynamics Observatory (SDO) was launched on February 11, 2010 from Kennedy Space Center on an Atlas V launch vehicle into a geosynchronous transfer orbit. SDO carries a suite of three scientific instruments, whose observations are intended to promote a more complete understanding of the Sun and its effects on the Earth's environment. After a successful launch, separation, and initial Sun acquisition, the launch and flight operations teams dove into a commissioning campaign that included, among other things, checkout and calibration of the fine attitude sensors and checkout of the Kalman filter (KF) and the spacecraft s inertial pointing and science control modes. In addition, initial calibration of the science instruments was also accomplished. During that process of KF and controller checkout, several interesting observations were noticed and investigated. The SDO fine attitude sensors consist of one Adcole Digital Sun Sensor (DSS), two Galileo Avionica (GA) quaternion-output Star Trackers (STs), and three Kearfott Two-Axis Rate Assemblies (hereafter called inertial reference units, or IRUs). Initial checkout of the fine attitude sensors indicated that all sensors appeared to be functioning properly. Initial calibration maneuvers were planned and executed to update scale factors, drift rate biases, and alignments of the IRUs. After updating the IRU parameters, the KF was initialized and quickly reached convergence. Over the next few hours, it became apparent that there was an oscillation in the sensor residuals and the KF estimation of the IRU bias. A concentrated investigation ensued to determine the cause of the oscillations, their effect on mission requirements, and how to mitigate them. The ensuing analysis determined that the oscillations seen were, in fact, due to an oscillation in the IRU biases. The low frequencies of the oscillations passed through the KF, were well within the controller bandwidth, and therefore the spacecraft was actually 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.

  7. U.S. initiatives in the international effort to mitigate the orbital debris environment

    NASA Astrophysics Data System (ADS)

    Levin, George M.

    1996-10-01

    Following release of the 1989 'Report on Orbital Debris' by the Interagency Group (Space) for the National Security Council, NASA undertook a series of extensive bilateral discussions with the major spacefaring nations on the topic of orbital debris. These discussions led to a greater understanding of both the cause and the effect of orbital debris. As a result of these discussions, the major spacefaring nations have taken definitive steps to redesign their launch vehicles and spacecraft so as to mitigate the production of orbital debris. In 1993 the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), and Japan formed a multilateral Inter- Agency Orbital Debris Coordination Committee (IADC). Since that time the Russian Space Agency (RSA), the Chines National Space Agency (CNSA), the French National Space Agency (CNES), the British National Space Agency (BNSA), and the Indian Space Agency (ISRO) have jointed the IADC. In 1994 orbital debris discussions began in the United Nations under the auspices of the Scientific and Technical Subcommittee of the Committee on the Peaceful Uses of Outer Space (UNCOPUOS). In 1995 UNCOPUOS adopted a multi-year program for studying orbital debris. In 1993 the White House Office of Science and Technology Policy (OSTP) and the National Security Council (NSC) undertook an interagency review to revise and update the 1989 'Report on Orbital Debris.' In November 1995 Dr. John H. Gibbons, the Assistant to the President for Science and Technology, released the 'Interagency Report on Orbital Debris -- 1995.'

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

    SciTech Connect

    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

    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.

  9. Orbit determination accuracies using satellite-to-satellite tracking

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    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.

  10. Radio metric orbit determination for the Giotto mission to Comet Halley

    NASA Technical Reports Server (NTRS)

    Wood, L. J.; Mottinger, N. A.; Jordan, J. F.

    1983-01-01

    An international fleet of five spacecraft will fly past Comet Halley as it travels through the inner solar system in early 1986. This paper discusses orbit determination problems associated with the Giotto spacecraft, sponsored by the European Space Agency. The large number of spin axis precession maneuvers required to maintain the desired spacecraft attitude creates a new kind of radio metric orbit determination problem for this mission. This paper investigates the accuracy with which the Giotto spacecraft orbit can be determined relative to the earth or the sun, and establishes the sensitivity of this accuracy to the selection of the parameters to be estimated, the form of estimator used, the number of tracking stations employed, the length of the data arc, the selection of data types processed, and the levels of various error sources.

  11. Introduction of empirical parameters deduced from the Hill's equations for satellite orbit determination.

    NASA Astrophysics Data System (ADS)

    Cretaux, J.-F.; Nouel, F.; Valorge, C.; Janniere, P.

    1994-05-01

    The theory of perturbations suggests that, in the calculation of ephemerides, most errors due to mismodeling of the forces acting on a spacecraft are of a resonant nature. Colombo (1986; 1989) has shown that they can be corrected by adjusting a certain number of parameters relative to a simple empirical force inferred from the so-called Hill's equations in spite of the complexity of the error causes: mismodeling of the gravitational field, radiation pressure etc. This principle can not be extended to all types of orbits and are valid only for circular ones (ex: geostationary or low Earth orbit). This force was introduced into an orbit determination software and it was tested on the orbits of the LAGEOS, STARLETTE, SPOT2, TOPEX and finally GPS satellites.

  12. Pinhole cameras as sensors for atomic oxygen in orbit: Application to attitude determination of the LDEF

    NASA Technical Reports Server (NTRS)

    Peters, Palmer N.; Gregory, John C.

    1992-01-01

    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, information on the spacecraft attitude relative to the orbital velocity can be obtained, provided that corrections are properly made for thermal spreading and a corotating atmosphere. The Long Duration Exposure Facility (LDEF) orientation, uncorrected for a corotating atmosphere, was determined to be yawed 8.0 +/- 0.4 degrees from its nominal attitude, with an estimated +/- 0.35 degree oscillation in yaw. The integrated effect of inclined orbit and corotating 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 corotating atmosphere. The measured thermal spreading is consistent with major exposure occurring during high solar activity, which occurred late during the LDEF mission.

  13. Phase Function Determination in Support of Orbital Debris Size Estimation

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    1992-08-01

    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.

  16. Automated orbit determination using tracking and data relay satellite (TDRS) data

    NASA Technical Reports Server (NTRS)

    Shank, D. E.; Waligora, S. R.

    1986-01-01

    A prototype for an onboard satellite orbit determination system has been developed at the Goddard Space Flight Center (GSFC) to aid in the research and development of onboard navigation. Two versions of the system, one for laboratory investigation and one for ground demonstration, are being used to gain insight into the feasibility and practicality of microprocessor-based automated orbit determination. This paper describes the mathematical modeling and the software structure of each system and presents the results of laboratory evaluation in terms of computational accuracy and real-time processing performance.

  17. New method for on-orbit-determination of parameters for guidance, navigation and control

    NASA Astrophysics Data System (ADS)

    Clemen, Carsten

    2002-07-01

    For most scientific satellite missions it is required that the attitude control system works with the greatest possible accuracy to achieve the missions objectives. Therefore it is necessary to know the non-linear system "satellite" with its different parameters e.g. the moments of inertia, the thruster parameters, mass, etc. as exactly as possible. But in most cases these parameters cannot be determined on earth so it has to be done on-orbit. For that reason an applicable estimation method must be found which is robust against all kinds of disturbances acting on the satellite: disturbing torques, noise and offset of the satellites sensors and actuators. Another condition is that only the measurements of the satellite sensors (attitude and angular velocity) can be used for determination. Because of these constraints and the complex non-linear behaviour of the satellite linear and conventional non-linear methods cannot be used for the estimation. A new method must be used. The idea is to compare the sensor measurements which are influenced by the just mentioned disturbances and the results of a computer-aided simulation of the non-disturbed satellite. With the difference between the measured and simulated sensor informations a cost function is determined. In an iteration loop the parameter values are estimated by varying them until this function reaches its minimum. This is performed with the simplex-method by NELDER and MEAD. Here the applicability and accuracy of this method is proved exemplarily by estimating the parameters of a satellites thruster system. This method delivers the parameters sufficiently exact independent from initialized errors in the simulation and disturbances on the real satellite. This method is also applicable to other parameters like for example the moments of inertia or the solar pressure torque, etc.

  18. 42 CFR 498.20 - Notice and effect of initial determinations.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...MEDICARE PROGRAM AND FOR DETERMINATIONS THAT AFFECT THE PARTICIPATION...Reconsidered, and Revised Determinations § 498.20 Notice and effect of initial determinations. (a) Notice of initial determination —(1) General...

  19. Accurate orbit determination strategies for the tracking and data relay satellites

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  20. The Determination of the Orbit Spaces of Compact Coregular Linear Groups

    E-print Network

    Vittorino Talamini

    2015-03-26

    Some aspects of phase transitions can be more conveniently studied in the orbit space of the action of the symmetry group. After a brief review of the fundamental ideas of this approach, I shall concentrate on the mathematical aspect and more exactly on the determination of the equations defining the orbit space and its strata. I shall deal only with compact coregular linear groups. The method exposed has been worked out together with prof. G. Sartori and it is based on the solution of a matrix differential equation. Such equation is easily solved if an integrity basis of the group is known. If the integrity basis is unknown one may determine anyway for which degrees of the basic invariants there are solutions to the equation, and in all these cases also find out the explicit form of the solutions. The solutions determine completely the stratification of the orbit spaces. Such calculations have been carried out for 2, 3 and 4-dimensonal orbit spaces. The method is of general validity but the complexity of the calculations rises tremendously with the dimension $q$ of the orbit space. Some induction rules have been found as well. They allow to determine easily most of the solutions for the $(q+1)$-dimensional case once the solutions for the $q$-dimensional case are known. The method exposed is interesting because it allows to determine the orbit spaces without using any specific knowledge of group structure and integrity basis and evidences a certain hidden and yet unknown link with group theory and invariant theory.

  1. Precision in the orbit determination of the TOPEX\\/POSEIDON satellite using GPS and recursive least squares method

    Microsoft Academic Search

    R. Vilhena de Moraes; H. Kuga; A. Silva

    2002-01-01

    The Global Positioning System is a powerful and low cost process to compute orbits for some artificial Earth satellites. The aim of this work is to consider a low computer cost procedure to determine the orbit of an artificial satellite using data from an onboard GPS receiver. Pseudoranges are used in the measurement equations for the orbit estimator. The least

  2. An improved majority voting algorithm and its application in GPS-based precise orbit determination of LEOs

    Microsoft Academic Search

    Bao-min Han; Yuan-xi Yang; Xiuying Zhu

    2006-01-01

    Precise Orbit Determination (POD) of Low Earth Orbiter satellites (LEOs) based on Point Positioning (PPP) technique utilizing dual-frequency spaceborne GPS observations has become one of the best POD methods at present. Quality control of raw spaceborne GPS observations is very complex but critical for achieving high orbiting accuracy. Among the various existing methods for detecting outliers, the majority-voting algorithm used

  3. Precise orbit determination of BeiDou constellation based on BETS and MGEX network.

    PubMed

    Lou, Yidong; Liu, Yang; Shi, Chuang; Yao, Xiuguang; Zheng, Fu

    2014-01-01

    Chinese BeiDou Navigation Satellite System is officially operational as a regional constellation with five Geostationary Earth Orbit (GEO) satellites, five Inclined Geosynchronous Satellite Orbit (IGSO) satellites and four Medium Earth Orbit (MEO) satellites. Observations from the BeiDou Experimental Tracking Stations (BETS) and the IGS Multi-GNSS Experiment (MGEX) network from 1 January to 31 March 2013 are processed for orbit determination of the BeiDou constellation. Various arc lengths and solar radiation pressure parameters are investigated. The reduced set of ECOM five-parameter model produces better performance than the full set of ECOM nine-parameter model for BeiDou IGSO and MEO. The orbit overlap for the middle days of 3-day arc solutions is better than 20?cm and 14?cm for IGSO and MEO in RMS, respectively. Satellite laser ranging residuals are better than 10?cm for both IGSO and MEO. For BeiDou GEO, the orbit overlap of several meters and satellite laser ranging residuals of several decimetres can be achieved. PMID:24733025

  4. 20 CFR 405.210 - How to request review of an initial determination.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...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...

  5. 20 CFR 405.210 - How to request review of an initial determination.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...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...

  6. Mitigation of ionospheric scintillation effects in kinematic LEO precise orbit determination

    NASA Astrophysics Data System (ADS)

    Zehentner, Norbert; Mayer-Gürr, Torsten

    2015-04-01

    Kinematic orbit determination for Low Earth Orbiting satellites is one of the core elements in gravity field recovery from GNSS tracked satellites. The accuracy of the kinematic orbit positions directly determines the achievable accuracy in terms of gravity field results. We apply a precise point positioning approach based on raw GNSS observations, without using any linear combinations. This method requires to take every effect directly into account, as non of the effects is eliminated by forming differences or linear combinations. For example, the ionospheric influence is taken into account by estimating the slant TEC, including higher order terms and corrections for ionospheric bending. Our approach preserves the original high measurement accuracy of the phase observations. The remaining factors reducing the achieved accuracy are not or incorrectly modeled systematic effects. The GOCE mission revealed one of these systematic effects: ionospheric scintillations. These are small and short term irregularities in the Earth's ionosphere which cause errors in GNSS observations. GOCE gravity field results showed a huge systematic effect along the geomagnetic equator. GOCE was flying in a sun-synchronous dusk-dawn orbit, which means that the satellite orbit is nearly stationary with respect to the Earth's ionosphere. As it is hardly possible to realistically model ionospheric irregularities they can not be corrected from the raw observations. We introduce an observation weighting method based on the rate of TEC index to reduce the influence of observations affected by ionospheric scintillations. This weighting scheme in combination with variance component estimation greatly reduces the influence of ionospheric scintillation on the kinematic orbit and in turn also on the gravity field result. We will show that by using the introduced weighting scheme the error in GOCE kinematic orbits is almost removed, without removing observations.

  7. Arrival and departure impulsive Delta V determination for precessing Mars parking orbits

    NASA Technical Reports Server (NTRS)

    Desai, Prasun N.; Buglia, James J.

    1992-01-01

    An attempt is made to develop a method for realistic estimation of the initial LEO mass. The method takes into account the actual geometry between the inbound and outbound hyperbolic asymptotes and the parking orbit, along with precession effects caused by the oblateness of Mars, in calculating the arrival and departure Delta V values. Three mission scenarios alternative to the arbitrarily assumed two tangential periapsis burns are described: a tangential periapsis arrival and an in-plane departure; an in-plane arrival and in-plane departure; and a tangential periapsis arrival and a 3D departure. Results obtained by the method under consideration compared well with a trajectory integration code, where the differences in the initial LEO orbit mass were within one percent, for all three cases. The method is considered to be an ideal tool for preliminary mission design, since it reduces the analysis computation time with minimal loss in accuracy.

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

    USGS Publications Warehouse

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

    1982-01-01

    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.

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

    E-print Network

    Psiaki, Mark L.

    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

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

    NASA Technical Reports Server (NTRS)

    Daly, J. K.

    1974-01-01

    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.

  11. Implementing a 50x50 gravity field model in an orbit determination system

    Microsoft Academic Search

    Daniel J. Fonte Jr.

    1993-01-01

    The Kepler problem treats the earth as if it is a spherical body of uniform density. In actuality, the earth's shape deviates from a sphere in terms of latitude (described by zonal harmonics), longitude (sectorial harmonics), and combinations of both latitude and longitude (tesseral harmonics). Operational Orbit Determination (OD) systems in the 1960's focused on the effects of the first

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

    E-print Network

    , Newport News, VA 23606, USA Abstract Thomas Jefferson National Accelerator Facility (Jefferson Lab) usesEMPIRICALLY DETERMINED RESPONSE MATRICES FOR ON-LINE ORBIT AND ENERGY CORRECTION AT THOMAS JEFFERSON NATIONAL ACCELERATOR FACILITY* A. Hofler, D. Bryan , L. Harwood, M. Joyce, V. Lebedev , TJNAF

  13. Reduced-dynamic technique for precise orbit determination of low earth satellites

    Microsoft Academic Search

    Sien-Chong Wu; Thomas P. Yunck; Catherine L. Thornton

    1988-01-01

    A reduced-dynamic technique for precise orbit determination of low earth satellites is described. This technique optimally combines the conventional dynamic technique with the nondynamic technique which uses differential GPS continuous carrier phase to define the state transition. A Kalman filter formulation for this reduced-dynamic technique is given. A covariance analysis shows that when neither the dynamic nor the nondynamic technique

  14. A system for autonomous navigation and attitude determination in geostationary orbit

    Microsoft Academic Search

    P. Maute; O. Defonte

    1990-01-01

    The results of a joint CNES-Aerospatiale study leading to an autonomous navigation and three-axis attitude determination system are presented. The principles, software architecture, preprocessing, navigator, orbit control, and hardware configuration of the system are described. The optimization process is described as well with attention given to sensor architecture and operational modes. It is found that the presence of an additional

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  16. Lunar Reconnaissance Orbiter Camera Narrow Angle Cameras: Laboratory and Initial Flight Calibration

    Microsoft Academic Search

    D. C. Humm; M. Tschimmel; B. W. Denevi; S. Lawrence; P. Mahanti; T. N. Tran; P. C. Thomas; E. Eliason; M. S. Robinson

    2009-01-01

    The Lunar Reconnaissance Orbiter Camera (LROC) has two identical Narrow Angle Cameras (NACs). Each NAC is a monochrome pushbroom scanner, providing images with a pixel scale of 50 cm from a 50-km orbit. A single NAC image has a swath width of 2.5 km and a length of up to 26 km. The NACs are mounted to acquire side-by-side imaging

  17. DETERMINING THE INITIAL HELIUM ABUNDANCE OF THE SUN

    SciTech Connect

    Serenelli, Aldo M. [Max Planck Institute for Astrophysics, Karl Schwarzschild Str. 1, Garching D-85471 (Germany); Basu, Sarbani, E-mail: aldos@mpa-garching.mpg.d [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States)

    2010-08-10

    We determine the dependence of the initial helium abundance and the present-day helium abundance in the convective envelope of solar models (Y {sub ini} and Y {sub surf}, respectively) on the parameters that are used to construct the models. We do so by using reference standard solar models (SSMs) to compute the power-law coefficients of the dependence of Y {sub ini} and Y {sub surf} on the input parameters. We use these dependencies to determine the correlation between Y {sub ini} and Y {sub surf} and use this correlation to eliminate uncertainties in Y {sub ini} from all solar model input parameters except the microscopic diffusion rate. We find an expression for Y {sub ini} that depends only on Y {sub surf} and the diffusion rate. By adopting the helioseismic determination of solar surface helium abundance, Y {sup surf} {sub sun} = 0.2485 {+-} 0.0035, and an uncertainty of 20% for the diffusion rate, we find that the initial solar helium abundance, Y {sup ini} {sub sun}, is 0.278 {+-} 0.006 independently of the reference SSMs (and particularly on the adopted solar abundances) used in the derivation of the correlation between Y {sub ini} and Y {sub surf}. When non-SSMs with extra mixing are used, then we derive Y {sup ini} {sub sun} = 0.273 {+-} 0.006. In both cases, the derived Y {sup ini} {sub sun} value is higher than that directly derived from solar model calibrations when the low-metallicity solar abundances (e.g., by Asplund et al.) are adopted in the models.

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    The Engineering Orbit Analysis Unit at GE Valley Forge used an Intel Hypercube Parallel Processor to investigate the performance and gain experience of parallel processors with a multi-satellite orbit determination problem. A general study was selected in which major blocks of computation for the multi-satellite orbit computations were used as units to be assigned to the various processors on the Hypercube. Problems encountered or successes achieved in addressing the orbit determination problem would be more likely to be transferable to other parallel processors. The prime objective was to study the algorithm to allow processing of observations later in time than those employed in the state update. Expertise in ephemeris determination was exploited in addressing these problems and the facility used to bring a realism to the study which would highlight the problems which may not otherwise be anticipated. Secondary objectives were to gain experience of a non-trivial problem in a parallel processor environment, to explore the necessary interplay of serial and parallel sections of the algorithm in terms of timing studies, to explore the granularity (coarse vs. fine grain) to discover the granularity limit above which there would be a risk of starvation where the majority of nodes would be idle or under the limit where the overhead associated with splitting the problem may require more work and communication time than is useful.

  4. Determination of kinematic state of an orbiting multibody using GNSS signals

    NASA Astrophysics Data System (ADS)

    Palmerini, Giovanni B.; Gasbarri, Paolo; Toglia, Chiara

    2009-06-01

    Precise attitude determination of the members of a free-flying multibody system is a not so immediate task, due essentially to the large motion of its appendages coupled with their relevant flexibility effects. In fact, sensors used to this aim in current projects, such as optical encoders usually positioned near the joints of each arm, are almost blind to these effects, and clusters of specific redundant sensors should, therefore, be required in order to reconstruct both elastic deformations and rigid motion. Satellite navigation systems (GNSS) offer a suitable and reliable solution to this problem. To exploit the phase of the signal, instead of the traditional pseudo random code, ensures a very high accuracy of the order of magnitude of centimeter. Such a process requires the solution of an initial ambiguity problem, related to the number of integer wavelength included in the length of the member. The aim of the paper is to investigate the capability of this GNSS based technique to reconstruct the kinematics of a flexible multibody system orbiting around the Earth. This analysis requires a simulation including both the multibody dynamics and the navigation system constellation to define the satellites lines-of-sight at each time step. Concerning multibody equations of motion, a Newtonian formulation is adopted in this work. A special attention is required about the choice of the state variables. As the internal forces are associated to the relative displacements between the bodies, which are small fractions of the distance of the multibody spacecraft from the center of the Earth, the task of obtaining these forces from inertial coordinates could be impossible from a numerical point of view. So, the problem is reformulated in such a way that the equation of motion of the system contains global equations, with no internal forces, and local equations, with internal forces. In the latter, only quantities of the same order of the spacecraft dimensions are present. Accuracies achievable in LEO orbit with current GPS and upcoming Galileo systems are evaluated to show the interest of the proposed technique.

  5. Determining Mars parking orbits which ensure in-plane arrival and departure burns

    NASA Technical Reports Server (NTRS)

    Desai, Prasun N.; Buglia, James J.

    1992-01-01

    A numerical method to find suitable Mars parking orbits is developed which takes into account geometries associated with the asymptotes, along with the nodal precession caused by the oblateness of Mars. A selected orbital plane which contains the arrival asymptote precesses through the stay time to the plane also containing the departure asymptote. The parking orbit is co-planar with both the arrival and departure asymptotes and only in-plane burns are required at both Mars arrival and departure. The need for a plane change at Mars departure to achieve the proper velocity vector for earth return is eliminated. The method requires very little computation time to determine a set of all possible inclinations and right ascensions of the ascending nodes.

  6. Impact of GPS satellite antenna offsets on GPS-based precise orbit determination

    NASA Astrophysics Data System (ADS)

    Kang, Z.; Tapley, B.; Ries, J.; Bettadpur, S.; Nagel, P.

    Since the successful demonstration of GPS-based Precise Orbit Determination (POD) on TOPEX/Poseidon in 1992, GPS-based POD for Low-Earth Orbiters (LEO) such as the CHAMP and GRACE satellites has become a popular method. The orbit accuracy of GPS-based POD has been improved from 3 cm to 1 cm in the radial direction. In order to achieve higher-accuracy results, it is necessary to understand and try to reduce the impact of various error sources on the orbits. One of them is the GPS satellite antenna offset. Currently, most GPS data processing institutions are using relative GPS satellite antenna offsets, and there are big differences (meter level) between the antenna offsets. In addition, accurate antenna offset values can be only estimated from processing GPS data currently with an accuracy of cm to dm levels. In this paper, we studied the impact of GPS satellite antenna offsets on GPS-based POD using the different offsets. The results show that the antenna offsets have large effects (a few cm) on the GPS onboard receiver antenna estimation and relatively small effects (about one cm) on the satellite orbit accuracy.

  7. Determination of the SNPP VIIRS SDSM screen transmittance from both yaw maneuver and regular on-orbit data

    NASA Astrophysics Data System (ADS)

    Lei, Ning; Chen, Xuexia; Xiong, Xiaoxiong

    2014-09-01

    The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (SNPP) satellite carries out radiometric calibration of its reflective solar bands primarily through observing a sunlit onboard solar diffuser (SD). The SD bidirectional reflectance distribution function (BRDF) degrades over time. The degradation factor is determined by an onboard solar diffuser stability monitor (SDSM) which observes the Sun through a pinhole screen and the sunlit SD. The transmittance of the SDSM pinhole screen over a range of solar angles was determined prelaunch and used initially to determine the BRDF degradation factor. The degradation factor versus time curves were found to have a number of very large unphysical undulations likely due to the inaccuracies in the prelaunch determined SDSM screen transmittance. To validate and if necessary to refine both the SD and the SDSM screen transmittances, satellite yaw maneuvers were carried out. With the yaw maneuver data determined SDSM screen transmittance, the computed BRDF degradation factor curves still have large unphysical ripples, indicating that the projected solar horizontal angular step size in the yaw maneuver data is too large to resolve the transmittance at a fine angular scale. We develop a methodology to use both the yaw maneuver and regular on-orbit data to determine the SDSM screen transmittance at a fine angular scale with a relative error standard deviation from 0.00029 (672 nm; detector 5) to 0.00074 (926 nm; detector 8). With the newly determined SDSM screen transmittance, the computed BRDF degradation factor behaves much more smoothly over time.

  8. Precise orbit determination of DORIS satellites: comparison of reduced-dynamical and dynamical orbit modeling and the verification of the nominal satellite models

    NASA Astrophysics Data System (ADS)

    Stepanek, P.; Rodriguez-Solano, C.; Hugentobler, U.; Filler, V.

    2012-12-01

    The reduced-dynamical modeling is currently used by the routine solutions of the GOP analysis center, which allows to a similar accuracy as the other analysis centers utilizing a precise non-conservative force modeling. The GOP works with a modified version of the Bernese GPS Software that doesn`t include the modeling of non-conservative forces but uses an empirical and pseudo-stochastic orbit modeling. This limitation is now overcome by the new scientific modification of the software, which opens the unique possibility to apply both approaches using the same software platform. The precise dynamical LEO orbit modeling includes the nominal attitude models and the satellite macro-models, which interact with the solar radiation, the Earth radiation and the atmosphere. The focus of this study is the analysis of the comparison between these two different approaches for LEO satellite orbit determination. Moreover, the need of employing empirical parameters, e.g. once-per-revolution along- and cross-track parameters, will be analyzed to verify the quality of the nominal satellite models. Finally, the impact of increasing complexity models will be discussed. All the presented studies are based on the comparison of estimated DORIS orbits with the multi-technique orbits estimated by other groups as well as on the internal arc overlaps and the orbit validation using SLR data. Not only orbit estimated with fixed network are analyzed but also the impact of the orbit models on the free-network solutions is investigated.

  9. Two-site autonomous orbit determination: the 2003 GEO observation campaign from Collepardo and Mallorca

    NASA Astrophysics Data System (ADS)

    Porfilio, M.; Piergentili, F.; Graziani, F.

    In September 2003 the Group of Astrodynamics of the University of Rome ``La Sapienza'' (GAUSS) carried out a two-site observation campaign devoted to the autonomous orbit determination of objects in the geosynchronous region. Two 40 cm aperture Ritchey-Chrétien devices were employed: the f/7.5 ``Collepardo Automatic Telescope'' (CAT, located in Collepardo, Italy) and a f/5 tube of the ``Observatori Astronòmic de Mallorca'' (OAM, located in Mallorca, Spain). The baseline between the sites is 916 km. 3 s long, 1 minute apart exposures were simultaneously taken in sidereal tracking mode, looking at the same arcs of the GEO ring; the fields of view allowed to see a few satellites in two successive frames from both sites, thus providing two positions: the Lambert theorem has been exploited to determining the orbits. A first order approximation of the targets angular motion has been used to fix synchronism errors. Of course, the longer the time interval between positions, the lower the effect of measurements errors. Nevertheless, the only way to have quite distant points would be tracking the satellite, which is typically not suitable for a surveillance campaign, thus not interesting from a practical standpoint. Currently, in the Measurement Working Group of the Inter-Agency Space Debris Co-ordination Committee (IADC), the orbits of the objects detected during GEO optical observation campaigns, are estimated under the assumption of null eccentricity. This is the only way, if one telescope is used and if only a few observations are available. Obviously, the hypothesis of circular orbit provides excellent results for actually geostationary satellites and definitely incorrect estimates for high eccentricity objects. The systematic cooperation of couples of observatories, would provide good orbit determination, for instance, for GTO debris. In the paper the results of the orbit determination from the September 2003 campaign are reported. More in detail, the outcomes of some classical methods for solving the Lambert theorem, are compared with the least squares improved solutions, with the circular orbit assumption results and with the TLEs.

  10. Evaluation and modeling of autonomous attitude thrust control for the Geostation Operational Environmental Satellite (GOES)-8 orbit determination

    Microsoft Academic Search

    W. Forcey; C. R. Minnie; R. L. Defazio

    1995-01-01

    The Geostationary Operational Environmental Satellite (GOES)-8 experienced a series of orbital perturbations from autonomous attitude control thrusting before perigee raising maneuvers. These perturbations influenced differential correction orbital state solutions determined by the Goddard Space Flight Center (GSFC) Goddard Trajectory Determination System (GTDS). The maneuvers induced significant variations in the converged state vector for solutions using increasingly longer tracking data spans.

  11. Recent improvements in DORIS orbit determination and station coordinates estimation at CNES/CLS Analysis Center

    NASA Astrophysics Data System (ADS)

    Soudarin, L.; Capdeville, H.; Lemoine, J.-M.; Schaeffer, P.

    2012-04-01

    At the end of 2011, the CNES/CLS Analysis Center has entirely re-processed the whole DORIS data set for orbit determination and tracking station coordinate estimation. In addition to SPOT-2, -3, -4, -5, Topex/Poseidon and Envisat, the DORIS/DGXX measurements of Jason-2 and Cryosat-2 are included in the products delivered to the IDS (combined multi-satellite weekly SINEX, orbits in sp3 format). The new processing was motivated by upgrades brought to the GINS/DYNAMO software and the availability of new models. Changes with respect to the previous processing set up for the IDS-3 realization (IDS solution contributing to ITRF2008 computation) are: - a priori reference system defined by DPOD2008 (also used for discontinuities and data rejection) and IERS EOP series aligned on ITRF2008; - trospospheric delays derived from GMF/GPT model; - EIGEN-6S gravity model. Attitude laws implemented in GINS have been revised. A new macro-model tuned by GRGS is now used for Jason-2. The objective of this presentation is to show the impact of this reprocessing on the orbit determination and the terrestrial reference frame. Post-fit residuals, orbit comparison, estimated dynamical parameters are discussed, as well as station positioning performances. Residual signals at draconitic and beta-prime periods are also examined, especially in the geocenter time series.

  12. TOPAS a new GPS adjustment system for multistation positioning and orbit determination

    NASA Astrophysics Data System (ADS)

    Landau, Herbert

    A new software package is presented for positioning with the Global Positioning System in a multistation/multisession network approach. The program allows the determination of satellite orbits, clock and atmospheric parameters and terrestrial positions by using raw undifferenced carrier phase and code measurements in a sequential approach. All parameters are modelled and determined in an optimal filtering/smoothing technique based on U-D factorization methods resulting in precise terrestrial positions and satellite orbits. The paper describes the software product and the method principally applied. Results of applications of TOPAS to different networks (DOENAV and GINFEST) are presented showing single-day repeatablities of about 5 cm in all components for baselines of 100 to 1600 km length. Comparisons between results obtained by using broadcast and precise ephemeris data and results derived from measurement improved orbital information are made. This shows the influence of the orbit improvement technique used by TOPAS on precise point positioning. Repeatability analysis of multi-day solutions results in accuracies of 0.01 to 0.03 ppm for baselines of 600 to 700 km length.

  13. Topex/Jason combined GPS/DORIS orbit determination in the tandem phase

    NASA Astrophysics Data System (ADS)

    Willis, P.; Haines, B.; Bar-Sever, Y.; Bertiger, W.; Muellerschoen, R.; Kuang, D.; Desai, S.

    2003-04-01

    In December 2001, the Jason-1 satellite was launched to extend the long-term success of the TOPEX/POSEIDON (T/P) oceanographic mission. The goals for the Jason-1 mission represent both a significant challenge and a rare opportunity for precise orbit determination (POD) analysts. Like its predecessor, Jason-1 carries three types of POD systems: a GPS receiver, a DORIS receiver and a laser retro-reflector. In view of the 1-cm goal for radial orbit accuracy, several major improvements have been made to the POD systems: 1) the GPS "BlackJack" TurboRogue Space Receiver (TRSR) tracks up to 12 GPS spacecraft using advanced codeless tracking techniques; 2) a newly developed DORIS receiver can track two ground beacons simultaneously with lower noise. In addition, the satellite itself features more straightforward attitude behavior, and a symmetric shape, simplifying the orbit determination models compared to T/P. On the other hand, the area-to-mass ratio for Jason-1 is larger, implying larger potential surface-force errors. This paper presents Jason-1 POD results obtained at JPL using the GIPSY-OASIS II (GOA) software package. Results from standard tests (orbit overlaps, laser control points) suggest that 1 to 2 cm radial orbit precision is already being achieved using the JPL reduced-dynamic estimation approach. We also report new DORIS POD strategies that make full profit of the additional number of common DORIS observations due to the T/P·Jason-1 tandem mode of orbit as well the additional dual-channel capability of the upgraded JASON receiver (allowing simultaneous tracking of two ground stations). New information on the satellite's time scale is availed through this new estimation strategy. Results show that a significant improvement to DORIS-based orbits could be gained using this strategy. Building on these results, we have extended the GIPSY/OASIS 11 software capability to more fully exploit the combined benefit of both GPS and DORIS measurements from T/P and Jason-1 in their preliminary tandem mode. POD test results are used to demonstrate the accuracy of these orbits and to compare results in different cases: DORIS-alone, and GPS and DORIS together in both single- and multi-satellite modes. On the other, we have demonstrated and explained an anomalous behavior of the on-board oscillator when crossing the South Atlantic Anomaly region. Finally, plans for future software enhancements, processing strategies and modeling improvements are presented.

  14. Error assessment of an autonomous real-time precision orbit determination program for a low-earth-orbit satellite using GPS observation data

    Microsoft Academic Search

    Jung Hyun Jo

    2002-01-01

    An autonomous, real-time, precision orbit determination (ARTPOD) program for low-Earth-orbit (LEO) satellites using the Global Positioning System (GPS) is planned and developed. Numerical simulations are used to assess the anticipated accuracy of LEO satellite tracking using GPS observation data. The GPS observation data for a particular LEO satellite, CHAMP (Challenging Mini-satellite Payload), is processed with the ARTPOD program and results

  15. Flight dynamics facility operational orbit determination support for the ocean topography experiment

    NASA Technical Reports Server (NTRS)

    Bolvin, D. T.; Schanzle, A. F.; Samii, M. V.; Doll, C. E.

    1991-01-01

    The Ocean Topography Experiment (TOPEX/POSEIDON) mission is designed to determine the topography of the Earth's sea surface across a 3 yr period, beginning with launch in June 1992. The Goddard Space Flight Center Dynamics Facility has the capability to operationally receive and process Tracking and Data Relay Satellite System (TDRSS) tracking data. Because these data will be used to support orbit determination (OD) aspects of the TOPEX mission, the Dynamics Facility was designated to perform TOPEX operational OD. The scientific data require stringent OD accuracy in navigating the TOPEX spacecraft. The OD accuracy requirements fall into two categories: (1) on orbit free flight; and (2) maneuver. The maneuver OD accuracy requirements are of two types; premaneuver planning and postmaneuver evaluation. Analysis using the Orbit Determination Error Analysis System (ODEAS) covariance software has shown that, during the first postlaunch mission phase of the TOPEX mission, some postmaneuver evaluation OD accuracy requirements cannot be met. ODEAS results also show that the most difficult requirements to meet are those that determine the change in the components of velocity for postmaneuver evaluation.

  16. Overview of Differential VLBI Observations of Lunar Orbiters in SELENE (Kaguya) for Precise Orbit Determination and Lunar Gravity Field Study

    NASA Astrophysics Data System (ADS)

    Hanada, Hideo; Iwata, Takahiro; Liu, Qinghui; Kikuchi, Fuyuhiko; Matsumoto, Koji; Goossens, Sander; Harada, Yuji; Asari, Kazuyoshi; Ishikawa, Toshiaki; Ishihara, Yoshiaki; Noda, Hirotomo; Tsuruta, Seiitsu; Petrova, Natalia; Kawano, Nobuyuki; Sasaki, Sho; Sato, Kaori; Namiki, Noriyuki; Kono, Yusuke; Iwadate, Kenzaburo; Kameya, Osamu; Shibata, Katsunori M.; Tamura, Yoshiaki; Kamata, Shunichi; Yahagi, Yukihiro; Masui, Wataru; Tanaka, Koji; Maejima, Hironori; Hong, Xiaoyu; Ping, Jinsong; Shi, Xian; Huang, Qian; Aili, Yusufu; Ellingsen, Simon; Schlüter, Wolfgang

    2010-07-01

    The Japanese lunar explorer SELENE (Kaguya), which was launched on September 14th, 2007, was the target of VLBI observations over the period November 2007 to June 2009. These observations were made in order to improve the lunar gravity field model, in particular the lower degree coefficients and the model near the limb. Differential VLBI Radio sources, called VRAD instruments, were on-board the subsatellites, Rstar (Okina) and Vstar (Ouna), and the radio signals were observed by the Japanese VERA (VLBI Exploration of Radio Astrometry) network, and an international VLBI network. Multi-frequency and same-beam VLBI techniques were utilized and were essential aspects of the successful observing program. Multi-frequency VLBI was employed in order to improve the accuracy of the orbit determination obtained from the phase delay from the narrow-band satellite signals, while the same-beam VLBI method was used to resolve the cycle ambiguity which is inherent in the multi-frequency VLBI method. The observations were made at three S-band frequencies (2212, 2218 and 2287 MHz), and one X-band frequency (8456 MHz). We have succeeded in correlating the recorded signals from Okina/Ouna, and we obtained phase delays with an accuracy of several pico-seconds at S-band.

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

    NASA Technical Reports Server (NTRS)

    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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

  19. Orbit Determination (OD) Error Analysis Results for the Triana Sun-Earth L1 Libration Point Mission and for the Fourier Kelvin Stellar Interferometer (FKSI) Sun-Earth L2 Libration Point Mission Concept

    NASA Technical Reports Server (NTRS)

    Marr, Greg C.

    2003-01-01

    The Triana spacecraft was designed to be launched by the Space Shuttle. The nominal Triana mission orbit will be a Sun-Earth L1 libration point orbit. Using the NASA Goddard Space Flight Center's Orbit Determination Error Analysis System (ODEAS), orbit determination (OD) error analysis results are presented for all phases of the Triana mission from the first correction maneuver through approximately launch plus 6 months. Results are also presented for the science data collection phase of the Fourier Kelvin Stellar Interferometer Sun-Earth L2 libration point mission concept with momentum unloading thrust perturbations during the tracking arc. The Triana analysis includes extensive analysis of an initial short arc orbit determination solution and results using both Deep Space Network (DSN) and commercial Universal Space Network (USN) statistics. These results could be utilized in support of future Sun-Earth libration point missions.

  20. Two-site orbit determination: The 2003 GEO observation campaign from Collepardo and Mallorca

    Microsoft Academic Search

    Manfredi Porfilio; Fabrizio Piergentili; Filippo Graziani

    2006-01-01

    In September 2003 the Group of Astrodynamics of the University of Rome “La Sapienza” (GAUSS) carried out a two-site optical observation campaign addressed to the orbit determination of objects in the geosynchronous region without a priori information. Two 40cm aperture Ritchey-Chrétien telescopes were employed: the f\\/7.5 “Collepardo Automatic Telescope” (CAT, located in Collepardo, Italy) and an f\\/5 tube of the

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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.

  2. The GPS Topex\\/Poseidon precise orbit determination experiment - Implications for design of GPS global networks

    Microsoft Academic Search

    Ulf J. Lindqwister; Stephen M. Lichten; Edgar S. Davis; Harold L. Theiss

    1993-01-01

    Topex\\/Poseidon, a cooperative satellite mission between United States and France, aims to determine global ocean circulation patterns and to study their influence on world climate through precise measurements of sea surface height above the geoid with an on-board altimeter. To achieve the mission science aims, a goal of 13-cm orbit altitude accuracy was set. Topex\\/Poseidon includes a Global Positioning System

  3. Single frequency GPS measurements in real-time artificial satellite orbit determination

    Microsoft Academic Search

    A. P. M. Chiaradia; H. K. Kuga; A. F. B. A. Prado

    2003-01-01

    A simplified and compact algorithm with low computational cost providing an accuracy around tens of meters for artificial satellite orbit determination in real-time and on-board is developed in this work. The state estimation method is the extended Kalman filter. The Cowell's method is used to propagate the state vector, through a simple Runge–Kutta numerical integrator of fourth order with fixed

  4. Initial Mars Upper Atmospheric Structure Results from the Accelerometer Science Experiment aboard Mars Reconnaissance Orbiter

    NASA Astrophysics Data System (ADS)

    Keating, G. M.; Bougher, S. W.; Theriot, M. E.; Tolson, R. H.; Blanchard, R. C.; Zurek, R. W.; Forbes, J. M.; Murphy, J.

    2006-12-01

    Designed for aerobraking, Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005, achieved Mars Orbital Insertion (MOI), March 10, 2006, and successfully completed aerobraking on August 30, 2006. Atmospheric density decreases exponentially with increasing height. By small propulsive adjustments of the apoapsis orbital velocity, periapsis altitude was fine tuned to the density surface that safely used the atmosphere of Mars to aerobrake over 445 orbits, providing 890 vertical structures. MRO periapsis precesses from near the South Pole at 6pm LST to near the equator at 3am LST. Meanwhile, apoapsis is brought dramatically from 40,000km at MOI to 480 km at aerobraking completion (ABX). Without aerobraking this would have required an additional 400kg of fuel. After ABX, two small propulsive orbital adjustment maneuvers September 5, 2006 and September 11, 2006 established the final Primary Science Orbit (PSO). Each of the 445 aerobraking orbits provides, a pair of vertical structures inbound toward periapsis and outbound from periapsis, with a distribution of density, scale heights, temperatures, and pressures along the orbital path, providing key in situ insight into various upper atmosphere (> 100 km) processes. One of the major questions for scientists studying Mars is: Where did the water go? Honeywell's substantially improved electronics package for its IMU (QA-2000 accelerometer, gyro, electronics) maximized accelerometer sensitivities at the requests of The George Washington University, JPL, and Lockheed Martin. The improved accelerometer sensitivities allowed density measurements to exceed 200km, at least 40 km higher than with Mars Odyssey (MO). This extends vertical structures from MRO into the neutral lower exosphere, a region where various processes may allow atmospheric gasses to escape. Over the eons, water may have been lost in both the lower atmosphere and the upper atmosphere, thus the water balance throughout the entire atmosphere from subsurface to exosphere may be equally critical. Comparisons of accelerometer data from Mars Global Surveyor (MGS), MO and MRO will help characterize key temporal and spatial cycles. During the Odyssey Aerobraking we discovered a very strong winter polar warming near 100km, where temperatures were found to be up to 100K higher than expected near the North Pole. However, with MRO we detected only a very weak winter polar warming at the South Pole. It is expected that the polar warming results from cross equatorial meridional flow from the summer hemisphere into the winter hemisphere with adiabatic heating near the winter pole. The discovery from MRO of a very weak winter warming near aphelion in the southern winter polar region compared to the very strong winter warming near perihelion in the northern winter polar region is apparently due to a weaker input of solar energy into the meridional circulation resulting in less adiabatic heating near aphelion in the winter polar region. Results are also shown of global scale measurements of non- migrating tides and of global density and temperature distributions.

  5. A demonstration of unified TDRS/GPS tracking and orbit determination

    NASA Technical Reports Server (NTRS)

    Haines, B.; Lichten, S.; Srinivasan, J.; Young, L.

    1995-01-01

    We describe results from an experiment in which TDRS and GPS satellites were tracked simultaneously from a small (3 station) ground network in the western United States. We refer to this technique as 'GPS-like tracking' (GLT) since the user satellite - in this case TDRS - is essentially treated as a participant in the GPS constellation. In the experiment, the TDRS K(sub space-to-ground link (SGL) was tracked together with GPS L-band signals in enhanced geodetic-quality GPS receivers (TurboRogue). The enhanced receivers simultaneously measured and recorded both the TDRS SGL and the GPS carrier phases with sub-mm precision, enabling subsequent precise TDRS orbit determination with differential GPS techniques. A small number of calibrated ranging points from routine operations at the TDRS ground station (White Sands, NM) were used to supplement the GLT measurements in order to improve determination of the TDRS longitude. Various tests performed on TDRS ephemerides derived from data collected during this demonstration - including comparisons with the operational precise orbit generated by NASA Goddard Space Flight Center - provide evidence that the TDRS orbits have been determined to better than 25 m with the GLT technique.

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

    NASA Technical Reports Server (NTRS)

    Peters, Palmer N.; Gregory, John C.

    1991-01-01

    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.

  7. Kinematic and reduced-dynamic precise orbit determination of CHAMP satellite over one year using spaceborne GPS phase zero-differences only

    Microsoft Academic Search

    D. Svehla; M. Rothacher

    2003-01-01

    Using zero-difference GPS carrier-phase measurements only, without any differencing in space or time domain, precise orbit determination (POD) of Low Earth Orbiters (LEO) can be performed. Among all space geodetic techniques (SLR, DORIS, VLBI, etc.) only GPS allows purely kinematic orbit determination where kinematic positions of the satellite are estimated independently of any force model or orbit altitude. Since the

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    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.

  9. Desaturation Maneuvers and Precise Orbit Determination for the BepiColombo Mission

    E-print Network

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

    2012-02-28

    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.

  10. 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

    Munoz, Douglas Perry

    of positions that the eyes can take in the orbits delimits the extent of visual exploration by head-fixed subjects, keeping the eyes centered in the orbits may indeed per-mit flexible orienting responsesAbstract In previous studies of saccadic eye movement reaction time, the manipulation of initial

  11. Low Earth Orbiter Satellite Precise Orbit Determination and its Precision Analysis from Satellite-Borne GPS with LP Estimation

    Microsoft Academic Search

    Zheng Zuoya; Dang Yamin; Lu Xiushan; Tian Maoyi

    2009-01-01

    To get high precise low earth orbiter (LEO) satellite orbit from satellite-borne GPS data, the satellite-borne GPS carrier phase measurements must be used, but there are still remnant cycle-slips after GPS data pre-processing. Least Square is an optimal method to solve parameters if the residual obeys to normal distribution, but it is difficult to process data with systematic error, LP

  12. 78 FR 44971 - Certain Robotic Toys and Components Thereof; Commission Determination Not To Review an Initial...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-25

    ...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...

  13. Desaturation Maneuvers and Precise Orbit Determination for the BepiColombo Mission

    E-print Network

    Alessi, Elisa Maria; Milani, Andrea; Tommei, Giacomo

    2012-01-01

    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 interva...

  14. Precise Orbit Determination for LEO Spacecraft Using GNSS Tracking Data from Multiple Antennas

    NASA Technical Reports Server (NTRS)

    Kuang, Da; Bertiger, William; Desai, Shailen; Haines, Bruce

    2010-01-01

    To support various applications, certain Earth-orbiting spacecrafts (e.g., SRTM, COSMIC) use multiple GNSS antennas to provide tracking data for precise orbit determination (POD). POD using GNSS tracking data from multiple antennas poses some special technical issues compared to the typical single-antenna approach. In this paper, we investigate some of these issues using both real and simulated data. Recommendations are provided for POD with multiple GNSS antennas and for antenna configuration design. The observability of satellite position with multiple antennas data is compared against single antenna case. The impact of differential clock (line biases) and line-of-sight (up, along-track, and cross-track) on kinematic and reduced-dynamic POD is evaluated. The accuracy of monitoring the stability of the spacecraft structure by simultaneously performing POD of the spacecraft and relative positioning of the multiple antennas is also investigated.

  15. Precision in the orbit determination of the TOPEX/POSEIDON satellite using GPS and recursive least squares method

    NASA Astrophysics Data System (ADS)

    Vilhena de Moraes, R.; Kuga, H.; Silva, A.

    The Global Positioning System is a powerful and low cost process to compute orbits for some artificial Earth satellites. The aim of this work is to consider a low computer cost procedure to determine the orbit of an artificial satellite using data from an onboard GPS receiver. Pseudoranges are used in the measurement equations for the orbit estimator. The least squares method with Givens rotations can be used to estimate the orbital parameters when the configuration of visible satellites is changing. Orbit and data are computed by numerical integration taking into account orbital perturbations for the user and GPS satellites. The procedure was tested using actual batches of one orbital period for the TOPEX/POSEIDON satellite (two hours of orbital period), force modelling due to the geopotential up to order 50 with coefficients given by the JGM -2 model, measurements of pseudoranges in one frequency L1 (code) and least squares method improved with Givens rotations. When compared with the reference Precision Orbit Ephemeris (POE) of JPL/NASA, results indicate that precision better than 10 m is easily obtained, even with short batches of data (one orbital period). Standard deviation of about 5 m resulted for the residuals. Precision considering other geopotential model, such as JGM -3, is studied. In this work it is also considered different sample rates for the observations and suggested improvements including the influence of the satellite attitude and a simple model for solar radiation pressure perturbations.

  16. Evaluation of LANDSAT-D Orbit Determination Using a Filter/Smoother (PREFER)

    NASA Technical Reports Server (NTRS)

    Gibbs, B. P.

    1982-01-01

    Simulated range and range rate data for five tracking stations were first generated using batch least squares orbit determination (GTDS). Then GTDS was used (in the differential correction mode) to produce a nominal trajectory which was input to PREFER. The GTDS differential correction (DC) run was made using models which differed from those used to produce the simulated data. These model differences were chosen to be fairly realistic approximations to the errors in the models actually used for operational orbit determination. Several different simulation runs were made with different types of model errors in order to determine the sensitivity to these errors. The nominal trajectory and the simulated measurement data were input to PREFER to produce a smoothed ephemeris file. Numerous runs of PREFER were made in which parameters describing the statistics of the model errors were varied. The likelihood function computed by the Kalman filter determined the ""best'' choice of input parameters. There was strong negative correlation between the likelihood function and the errors in the smoothed ephemeris.

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

    NASA Astrophysics Data System (ADS)

    Paredes-Gil, Katherine; Jaque, Pablo

    2015-01-01

    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.

  18. Orbital Pseudotumor: Uncommon Initial Presentation of IgG4-Related Disease

    PubMed Central

    Carbone, Teresa; Azêdo Montes, Ricardo; Andrade, Beatriz; Lanzieri, Pedro; Mocarzel, Luis

    2015-01-01

    IgG4-related disease (IgG4-RD) encompasses a group of fibroinflammatory conditions recognized in recent times. The main clinical features include variable degrees of tissue fibrosis, tumorlike expansions, perivascular lymphocytic infiltration rich in IgG4-positive plasma cells, and elevated serum IgG4. A case has been reported of an elderly patient with an unexplained unilateral exophthalmia; biopsy was performed and revealed lymphocytic infiltration, suggesting IgG4-RD. High serum levels of IgG4, in association with a good response to steroid therapy and to the exclusion of other diagnoses, confirmed the hypothesis of orbital pseudotumor by IgG4-RD. PMID:25838962

  19. Modeling of Non-Gravitational Forces for Precise and Accurate Orbit Determination

    NASA Astrophysics Data System (ADS)

    Hackel, Stefan; Gisinger, Christoph; Steigenberger, Peter; Balss, Ulrich; Montenbruck, Oliver; Eineder, Michael

    2014-05-01

    Remote sensing satellites support a broad range of scientific and commercial applications. The two radar imaging satellites TerraSAR-X and TanDEM-X provide spaceborne Synthetic Aperture Radar (SAR) and interferometric SAR data with a very high accuracy. The precise reconstruction of the satellite's trajectory is based on the Global Positioning System (GPS) measurements from a geodetic-grade dual-frequency Integrated Geodetic and Occultation Receiver (IGOR) onboard the spacecraft. The increasing demand for precise radar products relies on validation methods, which require precise and accurate orbit products. An analysis of the orbit quality by means of internal and external validation methods on long and short timescales shows systematics, which reflect deficits in the employed force models. Following the proper analysis of this deficits, possible solution strategies are highlighted in the presentation. The employed Reduced Dynamic Orbit Determination (RDOD) approach utilizes models for gravitational and non-gravitational forces. A detailed satellite macro model is introduced to describe the geometry and the optical surface properties of the satellite. Two major non-gravitational forces are the direct and the indirect Solar Radiation Pressure (SRP). The satellite TerraSAR-X flies on a dusk-dawn orbit with an altitude of approximately 510 km above ground. Due to this constellation, the Sun almost constantly illuminates the satellite, which causes strong across-track accelerations on the plane rectangular to the solar rays. The indirect effect of the solar radiation is called Earth Radiation Pressure (ERP). This force depends on the sunlight, which is reflected by the illuminated Earth surface (visible spectra) and the emission of the Earth body in the infrared spectra. Both components of ERP require Earth models to describe the optical properties of the Earth surface. Therefore, the influence of different Earth models on the orbit quality is assessed. The scope of the presentation is a detailed analysis of the orbit improvements due to sophisticated non-gravitational force and satellite macro models for the satellite TerraSAR-X.

  20. Determine ISS Soyuz Orbital Module Ballistic Limits for Steel Projectiles Hypervelocity Impact Testing

    NASA Technical Reports Server (NTRS)

    Lyons, Frankel

    2013-01-01

    A new orbital debris environment model (ORDEM 3.0) defines the density distribution of the debris environment in terms of the fraction of debris that are low-density (plastic), medium-density (aluminum) or high-density (steel) particles. This hypervelocity impact (HVI) program focused on assessing ballistic limits (BLs) for steel projectiles impacting the enhanced Soyuz Orbital Module (OM) micrometeoroid and orbital debris (MMOD) shield configuration. The ballistic limit was defined as the projectile size on the threshold of failure of the OM pressure shell as a function of impact speeds and angle. The enhanced OM shield configuration was first introduced with Soyuz 30S (launched in May 2012) to improve the MMOD protection of Soyuz vehicles docked to the International Space Station (ISS). This test program provides HVI data on U.S. materials similar in composition and density to the Russian materials for the enhanced Soyuz OM shield configuration of the vehicle. Data from this test program was used to update ballistic limit equations used in Soyuz OM penetration risk assessments. The objective of this hypervelocity impact test program was to determine the ballistic limit particle size for 440C stainless steel spherical projectiles on the Soyuz OM shielding at several impact conditions (velocity and angle combinations). This test report was prepared by NASA-JSC/ HVIT, upon completion of tests.

  1. 20 CFR 410.621 - Effect of initial determination.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 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,...

  2. Orbit Determination of Chang'e-3 and Positioning of the Lander and the Rover

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Chang, S.; Li, P.; Hu, X.

    2014-12-01

    The Chang'E-3 (CE-3) lunar probe of China was launched on 2 December 2013. After about 112 h of flight, it was captured by the Moon on 6 December, and entered a polar, near circular lunar orbit with an altitude of approximately 100 km. The probe's flight on 100 km*100 km and 100 km*15 km orbit lasted about 4 days respectively, then the probe soft landed on the east of Sinus Iridum area at 13:11 UTC on 14 December successfully. Results on precision orbit determination and positioning of the lander and the rover are presented here. We describe the data, modeling and methods used to achieve position knowledge. In addition to the radiometric X-band range and Doppler tracking data, Delta Differential One-way Ranging (?DOR) data are also used in the calculation, which shows that they can improve the accuracy of the orbit reconstruction. Total position overlap differences are about 20 m and 30 m for the 100 km*100 km and 100 km*15 km lunar orbit respectively, increased by ~50 % with respect to CE-2. A kinematic statistical method is applied to determine the position of the lander and relative position of the rover with respect to the lander. The location of the lander is computed as: 44.1216º N, 19.5124º W and -2632.0 m in the lunar Mean Axes coordinate system. The position difference of the lander is better than 50 m compared to the result of the LRO photograph. From 15 to 21 December, the rover walked around the lander, and took photos of each other at the parking point A, B, C, D, E (max distance from the lander is about 25 m). The delta VLBI phase delay data are used to compute the relative position of the rover at the parking points, and the accuracy of the relative position can reach to 1-2 m comparing with the results of visual method.

  3. An orbit determination algorithm by means of the satellite-borne GPS data and Kalman filter

    NASA Astrophysics Data System (ADS)

    Ra, Pei-zhang; Xiong, Yong-ging

    2006-04-01

    Using the Kalman filter algorithm, we have processed on-board GPS data of Shenzhou 4. The research focuses on three problems, namely, the selection criteria for the model error variance matrix of the Kalman filter, the effects of GPS signal interruption or runs of outliers on the recursive filtering, and the method to monitor the filter running status (normal or divergent). The aim is to evaluate the reliability of long-time stationary running of this algorithm used for on-board autonomous orbit determination

  4. Precise Relative Orbit Determination of Low Earth Orbit Formation Flights Using GPS Pseudorange and Carrier-Phase Measurements

    Microsoft Academic Search

    Egemen Imre; Phil Palmer; Yoshi Hashida

    Formation flying is emerging as an important technology on achieving the tight mission requirements of imaging and remote sensing systems, especially radio interferometry and synthetic aperture radar (SAR) applications. A higher absolute and relative position and orbit knowledge is always sought in these kinds of applications. Such requirements can be met to a large extent by manipulation of GPS data.

  5. Lunar Reconnaissance Orbiter Camera Narrow Angle Cameras: Laboratory and Initial Flight Calibration

    NASA Astrophysics Data System (ADS)

    Humm, D. C.; Tschimmel, M.; Denevi, B. W.; Lawrence, S.; Mahanti, P.; Tran, T. N.; Thomas, P. C.; Eliason, E.; Robinson, M. S.

    2009-12-01

    The Lunar Reconnaissance Orbiter Camera (LROC) has two identical Narrow Angle Cameras (NACs). Each NAC is a monochrome pushbroom scanner, providing images with a pixel scale of 50 cm from a 50-km orbit. A single NAC image has a swath width of 2.5 km and a length of up to 26 km. The NACs are mounted to acquire side-by-side imaging for a combined swath width of 5 km. The NAC is designed to fully characterize future human and robotic landing sites in terms of scientific and resource merit, trafficability, and hazards. The North and South poles will be mapped at 1-meter-scale poleward of 85.5 degrees latitude. Stereo coverage is achieved by pointing the NACs off-nadir, which requires planning in advance. Read noise is 91 and 93 e- and the full well capacity is 334,000 and 352,000 e- for NAC-L and NAC-R respectively. Signal-to-noise ranges from 42 for low-reflectance material with 70 degree illumination to 230 for high-reflectance material with 0 degree illumination. Longer exposure times and 2x binning are available to further increase signal-to-noise with loss of spatial resolution. Lossy data compression from 12 bits to 8 bits uses a companding table selected from a set optimized for different signal levels. A model of focal plane temperatures based on flight data is used to command dark levels for individual images, optimizing the performance of the companding tables and providing good matching of the NAC-L and NAC-R images even before calibration. The preliminary NAC calibration pipeline includes a correction for nonlinearity at low signal levels with an offset applied for DN>600 and a logistic function for DN<600. Flight images taken on the limb of the Moon provide a measure of stray light performance. Averages over many lines of images provide a measure of flat field performance in flight. These are comparable with laboratory data taken with a diffusely reflecting uniform panel.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

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

    PubMed Central

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

    2011-01-01

    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

  8. Determinants of breastfeeding initiation among mothers in Kuwait

    PubMed Central

    2010-01-01

    Background Exclusive breastfeeding is recommended as the optimal way to feed infants for the first six months of life. While overall breastfeeding rates are high, exclusive breastfeeding is relatively uncommon among Middle Eastern women. The objective of this study was to identify the incidence of breastfeeding amongst women in the six governorates of Kuwait and the factors associated with the initiation of breastfeeding. Methods A sample of 373 women (aged 17-47 years), recruited shortly after delivery from four hospitals in Kuwait, completed a structured, interviewer-administered questionnaire. Multivariate logistic regression analysis was used to identify those factors independently associated with the initiation of breastfeeding. Results In total, 92.5% of mothers initiated breastfeeding and at discharge from hospital the majority of mothers were partially breastfeeding (55%), with only 30% of mothers fully breastfeeding. Prelacteal feeding was the norm (81.8%) and less than 1 in 5 infants (18.2%) received colostrum as their first feed. Only 10.5% of infants had been exclusively breastfed since birth, the remainder of the breastfed infants having received either prelacteal or supplementary infant formula feeds at some time during their hospital stay. Of the mothers who attempted to breastfeed, the majority of women (55.4%) delayed their first attempt to breastfeed until 24 hours or more after delivery. Breastfeeding at discharge from hospital was positively associated with paternal support for breastfeeding and negatively associated with delivery by caesarean section and with the infant having spent time in the Special Care Nursery. Conclusions The reasons for the high use of prelacteal and supplementary formula feeding warrant investigation. Hospital policies and staff training are needed to promote the early initiation of breastfeeding and to discourage the unnecessary use of infant formula in hospital, in order to support the establishment of exclusive breastfeeding by mothers in Kuwait. PMID:20667112

  9. Validity of repeated initial rise thermoluminescence kinetic parameter determinations

    SciTech Connect

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

    1990-01-01

    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.

  10. 20 CFR 418.1310 - When may you request that we make a new initial determination?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...you request that we make a new initial determination? 418.1310 Section 418.1310...Income-Related Monthly Adjustment Amount Determinations and the Administrative Review Process...you request that we make a new initial determination? (a) You may request that we...

  11. Accurate Determination of Comet and Asteroid Orbits Leading to Collision With Earth

    NASA Technical Reports Server (NTRS)

    Roithmayr, Carlos M.; Kay-Bunnell, Linda; Mazanek, Daniel D.; Kumar, Renjith R.; Seywald, Hans; Hausman, Matthew A.

    2005-01-01

    Movements of the celestial bodies in our solar system inspired Isaac Newton to work out his profound laws of gravitation and motion; with one or two notable exceptions, all of those objects move as Newton said they would. But normally harmonious orbital motion is accompanied by the risk of collision, which can be cataclysmic. The Earth s moon is thought to have been produced by such an event, and we recently witnessed magnificent bombardments of Jupiter by several pieces of what was once Comet Shoemaker-Levy 9. Other comets or asteroids may have met the Earth with such violence that dinosaurs and other forms of life became extinct; it is this possibility that causes us to ask how the human species might avoid a similar catastrophe, and the answer requires a thorough understanding of orbital motion. The two red square flags with black square centers displayed are internationally recognized as a warning of an impending hurricane. Mariners and coastal residents who know the meaning of this symbol and the signs evident in the sky and ocean can act in advance to try to protect lives and property; someone who is unfamiliar with the warning signs or chooses to ignore them is in much greater jeopardy. Although collisions between Earth and large comets or asteroids occur much less frequently than landfall of a hurricane, it is imperative that we learn to identify the harbingers of such collisions by careful examination of an object s path. An accurate determination of the orbit of a comet or asteroid is necessary in order to know if, when, and where on the Earth s surface a collision will occur. Generally speaking, the longer the warning time, the better the chance of being able to plan and execute action to prevent a collision. The more accurate the determination of an orbit, the less likely such action will be wasted effort or, what is worse, an effort that increases rather than decreases the probability of a collision. Conditions necessary for a collision to occur are discussed, and warning times for long-period comets and near-Earth asteroids are presented.

  12. 42 CFR 405.704 - Actions which are initial determinations.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...number of days of inpatient hospital benefits utilized during a spell of illness or for purposes of the inpatient psychiatric hospital...payment requirement; (10) The beginning and ending of a spell of illness, including a determination made under the...

  13. 42 CFR 405.704 - Actions which are initial determinations.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...number of days of inpatient hospital benefits utilized during a spell of illness or for purposes of the inpatient psychiatric hospital...payment requirement; (10) The beginning and ending of a spell of illness, including a determination made under the...

  14. 20 CFR 418.1345 - Is reopening of an initial or reconsidered determination made by us ever appropriate?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...initial or reconsidered determination made by us ever appropriate? 418.1345 Section...initial or reconsidered determination made by us ever appropriate? We may reopen an initial or reconsidered determination made by us when the conditions for reopening are...

  15. Satellite Material Type and Phase Function Determination in Support of Orbital Debris Size Estimation

    NASA Astrophysics Data System (ADS)

    Hejduk, M.; Cowardin, H.; Stansbery, E.

    2012-09-01

    In performing debris surveys of deep-space orbital regions, the considerable volume of the area to be surveyed and the increased orbital altitude suggest optical telescopes as the most efficient survey instruments; but to proceed this way, methodologies for debris object size estimation using only optical tracking and photometric information are needed. Basic photometry theory indicates that size estimation should be possible if satellite albedo and shape are known. One method for estimating albedo is to try to determine the object's material type photometrically, as one can determine the albedos of common satellite materials in the laboratory. Examination of laboratory filter photometry (using Johnson BVRI filters) on a set of satellite material samples indicates that most material types can be separated at the 1-sigma level via B-R versus R-I color differences with a relatively small amount of required resampling, and objects that remain ambiguous can be resolved by B-R versus B-V color differences and solar radiation pressure differences. To estimate shape, a technique advanced by Hall et al. (2007), based on phase-brightness density curves and not requiring any a priori knowledge of attitude, has been modified slightly to try to make it more resistant to the specular characteristics of different materials and to reduce the number of samples necessary to make robust shape determinations. Working from a gallery of idealized debris shapes, the modified technique identifies most shapes within this gallery correctly, also with a relatively small amount of resampling. These results are, of course, based on relatively small laboratory investigations and simulated data, and expanded laboratory experimentation and further investigation with in situ survey measurements will be required in order to assess their actual efficacy under survey conditions; but these techniques show sufficient promise to justify this next level of analysis.

  16. Single frequency GPS measurements in real-time artificial satellite orbit determination

    NASA Astrophysics Data System (ADS)

    Chiaradia, orbit determination A. P. M.; Kuga, H. K.; Prado, A. F. B. A.

    2003-07-01

    A simplified and compact algorithm with low computational cost providing an accuracy around tens of meters for artificial satellite orbit determination in real-time and on-board is developed in this work. The state estimation method is the extended Kalman filter. The Cowell's method is used to propagate the state vector, through a simple Runge-Kutta numerical integrator of fourth order with fixed step size. The modeled forces are due to the geopotential up to 50th order and degree of JGM-2 model. To time-update the state error covariance matrix, it is considered a simplified force model. In other words, in computing the state transition matrix, the effect of J 2 (Earth flattening) is analytically considered, which unloads dramatically the processing time. In the measurement model, the single frequency GPS pseudorange is used, considering the effects of the ionospheric delay, clock offsets of the GPS and user satellites, and relativistic effects. To validate this model, real live data are used from Topex/Poseidon satellite and the results are compared with the Topex/Poseidon Precision Orbit Ephemeris (POE) generated by NASA/JPL, for several test cases. It is concluded that this compact algorithm enables accuracies of tens of meters with such simplified force model, analytical approach for computing the transition matrix, and a cheap GPS receiver providing single frequency pseudorange measurements.

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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.

  18. Orbit correction in an orbit separated cyclotron

    NASA Astrophysics Data System (ADS)

    Plostinar, C.; Rees, G. H.

    2014-04-01

    The orbit separated proton cyclotron (OSC) described in [1] differs in concept from that of a separated orbit cyclotron (SOC) [2]. Synchronous acceleration in an OSC is based on harmonic number jumps and orbit length adjustments via reverse bending. Four-turn acceleration in the OSC enables it to have four times fewer cryogenic-cavity systems than in a superconducting linac of the same high beam power and energy range. Initial OSC studies identified a progressive distortion of the spiral beam orbits by the off-axis, transverse deflecting fields in its accelerating cavities. Compensation of the effects of these fields involves the repeated use of a cavity field map, in a 3-D linac tracking code, to determine the modified arc bends required for the OSC ring. Subsequent tracking studies confirm the compensation scheme and show low emittance growth in acceleration.

  19. GPS interferometric attitude and heading determination: Initial flight test results

    NASA Technical Reports Server (NTRS)

    Vangraas, Frank; Braasch, Michael

    1991-01-01

    Attitude and heading determination using GPS interferometry is a well-understood concept. However, efforts have been concentrated mainly in the development of robust algorithms and applications for low dynamic, rigid platforms (e.g., shipboard). This paper presents results of what is believed by the authors to be the first realtime flight test of a GPS attitude and heading determination system. The system is installed in Ohio University's Douglas DC-3 research aircraft. Signals from four antennas are processed by an Ashtech 3DF 24-channel GPS receiver. Data from the receiver are sent to a microcomputer for storage and further computations. Attitude and heading data are sent to a second computer for display on a software generated artificial horizon. Demonstration of this technique proves its candidacy for augmentation of aircraft state estimation for flight control and navigation as well as for numerous other applications.

  20. GPS interferometric attitude and heading determination - Initial flight test results

    NASA Technical Reports Server (NTRS)

    Van Graas, Frank; Braasch, Michael

    1992-01-01

    Attitude and heading determination using GPS interferometry is a well-understood concept. However, efforts have been concentrated mainly in the development of robust algorithms and applications for low-dynamic, rigid platforms (e.g., shipboard). This paper presents results of what is believed to be the first real-time flight test of a GPS attitude and heading determination system. Signals from four antennas are processed by a 24-channel GPS receiver. Data from the receiver are sent to a microcomputer for storage and further computations. Attitude and heading data are sent to a second computer for display on a software-generated artificial horizon. Demonstration of this technique proves its candidacy for augmentation of aircraft state estimation for flight control and navigation, as well as for numerous other applications.

  1. JASON-1 Precise Orbit Determination (POD) Through the Combination and Comparison of GPS, SLR, DORIS and Altimeter Crossover Data

    NASA Technical Reports Server (NTRS)

    Luthcke, Scott B.; Zelensky, N. P.; Rowlands, D. D.; Lemoine, F. G.; Chinn, D. S.; Williams, T. A.

    2002-01-01

    Jason-1, launched on December 7,2001, is continuing the time series of centimeter level ocean topography observations as the follow-on to the highly successful TOPEX/POSEIDON (T/P) radar altimeter satellite. The precision orbit determination (POD) is a critical component to meeting the ocean topography goals of the mission. T P has demonstrated that the time variation of ocean topography can be determined with an accuracy of a few centimeters, thanks to the availability of highly accurate orbits based primarily on SLR+DORIS tracking. The Jason-1 mission is intended to continue measurement of the ocean surface with the same, if not better accuracy. Fortunately, Jason- 1 POD can rely on four independent tracking data types available including near continuous tracking data from the dual frequency codeless BlackJack GPS receiver. Orbit solutions computed using individual and various combinations of GPS, SLR, DORIS and altimeter crossover data types have been determined from over 100 days of Jason-1 tracking data, The performance of the orbit solutions and tracking data has been evaluated. Orbit solution evaluation and comparison has provided insight into possible areas of refinement. Several aspects of the POD process are examined to obtain orbit improvements including measurement modeling, force modeling and solution strategy. The results of these analyses will be presented.

  2. JASON-1 Precise Orbit Determination (POD) Through the Combination and Comparison of GPS, SLR, DORIS and Altimeter Crossover Data

    NASA Technical Reports Server (NTRS)

    Luthcke, S. B.; Zelensky, N. P.; Lemoine, Frank G.; Chinn, D. S.; Williams, T. A.

    2002-01-01

    Jason-1, launched on December 7, 2001, is continuing the time series of centimeter level ocean topography observations as the follow-on to the highly successful TOPEX/POSEIDON (T/P) radar altimeter satellite. The precision orbit determination (POD) is a critical component to meeting the ocean topography goals of the mission. T/P has demonstrated that the time variation of ocean topography can be determined with an accuracy of a few centimeters, thanks to the availability of highly accurate orbits based primarily on SLR+DORIS tracking. The Jason-1 mission is intended to continue measurement of the ocean surface with the same, if not better accuracy. Fortunately, Jason-1 POD can rely on four independent tracking data types available including near continuous tracking data from the dual frequency codeless BlackJack GPS receiver. Orbit solutions computed using individual and various combinations of GPS, SLR, DORIS and altimeter crossover data types have been determined from over 100 days of Jason-1 tracking data. The performance of the orbit solutions and tracking data has been evaluated. Orbit solution evaluation and comparison has provided insight into possible areas of refinement. Several aspects of the POD process are examined to obtain orbit improvements including measurement modeling, force modeling and solution strategy. The results of these analyses will be presented.

  3. 31 CFR 29.404 - Initial benefit determinations and reconsideration by the Benefits Administrator.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...Administrator. (a) Initial benefit determinations. The Benefits Administrator will process applications for Federal Benefit Payments and determine the eligibility for and the amount and form of Federal Benefit Payments....

  4. Applications of singular value analysis and partial-step algorithm for nonlinear orbit determination

    NASA Astrophysics Data System (ADS)

    Ryne, Mark S.; Wang, Tseng-Chan

    An adaptive method in which cruise and nonlinear orbit determination problems can be solved using a single program is presented. It involves singular value decomposition augmented with an extended partial step algorithm. The extended partial step algorithm constrains the size of the correction to the spacecraft state and other solve-for parameters. The correction is controlled by an a priori covariance and a user-supplied bounds parameter. The extended partial step method is an extension of the update portion of the singular value decomposition algorithm. It thus preserves the numerical stability of the singular value decomposition method, while extending the region over which it converges. In linear cases, this method reduces to the singular value decomposition algorithm with the full rank solution. Two examples are presented to illustrate the method's utility.

  5. Theory of an experiment in an orbiting space laboratory to determine the gravitational constant.

    NASA Technical Reports Server (NTRS)

    Vinti, J. P.

    1972-01-01

    An experiment is discussed for determining the gravitational constant with the aid of an isolated system consisting of an artificial satellite moving around an artificial planet. The experiment is to be conducted in a spherical laboratory traveling in an orbit around the earth. Difficulties due to the gravity-gradient term are considered, and the three-tunnel method proposed by Wilk (1969) is examined. The rotation of the sphere is discussed together with aspects of the reference systems used, the equations of motion of the spacecraft and of the test objects, the field from the earth's gravity gradient at the test object, higher harmonic terms in the gravity gradient force, gravitational effects of the spacecraft itself, and a computer simulation.

  6. Utilization of analytical methods for orbit determination in high accuracy geodetic positioning

    NASA Astrophysics Data System (ADS)

    Georgiev, N.

    The technique developed by Georgiev (1979) to permit highly accurate (0.7-2-m) forecasting of satellite positions over intervals of 2-5 days is described and demonstrated. The technique determines the intermediate orbit analytically, estimates the perturbations due to gravitational and nongravitational effects by the numerical procedure of Everhardt, and solves the resulting problem by the generalized method of two fixed centers (Aksenov, 1977). Sample results are presented in tables and graphs and discussed in terms of zonal, tesseral, and sectorial harmonics and atmospheric effects (important at altitudes up to 1200 km). The accuracy of the method is shown to be excellent, even when the flattening of earth is taken into account.

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

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    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.

  8. Determination of On-Orbit Cabin Air Loss from the International Space Station (ISS)

    NASA Technical Reports Server (NTRS)

    Williams, David E.; Leonard, Daniel J.; Smith, Patrick J.

    2004-01-01

    The International Space Station (ISS) loses cabin atmosphere mass at some rate. Due to oxygen partial pressures fluctuations from metabolic usage, the total pressure is not a good data source for tracking total pressure loss. Using the nitrogen partial pressure is a good data source to determine the total on-orbit cabin atmosphere loss from the ISS, due to no nitrogen addition or losses. There are several important reasons to know the daily average cabin air loss of the ISS including logistics planning for nitrogen and oxygen. The total average daily cabin atmosphere loss was estimated from January 14 to April 9 of 2003. The total average daily cabin atmosphere loss includes structural leakages, Vozdukh losses, Carbon Dioxide Removal Assembly (CDRA) losses, and other component losses. The total average daily cabin atmosphere loss does not include mass lost during Extra-Vehicular Activities (EVAs), Progress dockings, Space Shuttle dockings, calibrations, or other specific one-time events.

  9. Physical Properties of Fireball-Producing Earth-Impacting Meteoroids and Orbit Determination through Shadow Calibration of the Buzzard Coulee Meteorite Fall

    NASA Astrophysics Data System (ADS)

    Milley, Ellen Palesa

    The physical properties of the meteoroid population were investigated through combining data from a number of fireball camera networks. PE values, as a measure of meteoroid strength, were calculated and linked with other observational criteria (Tisserand parameter, meteor shower identification). The historic divisions for fireball types based on the PE criterion were not observed in the large data set, but a correlation with source region was recognized. Meteor showers demonstrated different amounts of variation in PE values potentially related to the materials found in each parent comet. The trajectory and pre-fall orbit for the Buzzard Coulee meteoroid were determined through the calibration of shadows cast by the fireball. The method of using shadows to triangulate a trajectory was developed and evaluated. The best fit trajectory was coupled with an initial velocity of 18.0 km/s to compute the heliocentric orbit. Buzzard Coulee fell from a modestly inclined near-Earth Apollo orbit. It is the 12th fallen meteorite to be associated with an orbit.

  10. Solar panel orientation derived from DORIS and GPS precise orbit determination

    NASA Astrophysics Data System (ADS)

    Gobinddass, Marie-Line; Willis, Pascal; Haines, Bruce

    Solar radiation pressure is currently a limiting factor in Precise Orbit Determination. To cope with model uncertainties, solar radiation pressure models are usually rescaled with an empirical Cr parameter. All DORIS data available from all satellites since 1993 have been reprocessed by estimating Cr coefficients on a daily basis. These time series usually show a signal depending on the satellite. Lower orbiting satellites (SPOTs and Envisat) show larger variations, especially around 11-year maximum, with a clear annual signal. Higher-altitude DORIS satellites used for altimetry (TOPEX/Poseidon, Jason-1, -2) show a better consistency. We focus here on the only 2 significant discontinuities observed in all the Cr time series: A 20% change in January 2008 for SPOT-5 and a 7% change on July, 1993 for TOPEX/Poseidon. While the SPOT-5 disconti-nuity, can be totally explained by an effective solar panel re-orientation done by CNES for this satellite (40 degrees over a few days), no similar explanation has been provided until now for TOPEX/Poseidon. Early GPS data for this satellite will be re-processed to determine whether a similar discontinuity in Cr is detected. As July 27, 1993 was the first day of solar panel re-orientation, we propose the hypothesis of a small mis-alignment of the TOPEX/Poseidon solar panel before this epoch. Consequences of ignoring these discontinuities for SPOT-5 and TOPEX/Poseidon for the DORIS geodetic results (tracking station coordinates, geocenter mo-tion) are investigated. Easy way to overcome these problems in future DORIS reprocessing activities of the International DORIS Service (IDS) are also discussed.

  11. Detection of Bone Metastases in Initial Staging of Orbital Embryonal Rhabdomyosarcoma by Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography

    PubMed Central

    Ozcan Kara, Pelin; Kara Gedik, Gonca; Sari, Oktay

    2011-01-01

    Rhabdomyosarcoma is the most common form of soft tissue sarcoma in young children. In soft tissue sarcomas, isolated metastases are seen in the lung, soft tissue, and bone. The optimal management of these tumors depends on the site, size, and grade of the local growth, and accurate staging of the disease when first seen. Although detection of the primary site of disease is usually accomplished well with conventional techniques, the performance of fluorodexyglucose (FDG) positron emission tomography/computed tomography (PET/CT) may be useful to determine metastases that are not clinically evident. We describe a case of early detection of distant metastases by FDG PET/CT in a young patient diagnosed with orbital embryonal rhabdomyosarcoma. Conflict of interest:None declared. PMID:23487301

  12. Development Strategy of Orbit Determination System for Korea's Lunar Mission: Lessons from ESA, JAXA, ISRO and CNSA's Experiences

    NASA Astrophysics Data System (ADS)

    Song, Young-Joo; Ahn, Sang-il; Sim, Eun-Sup

    2014-09-01

    In this paper, a brief but essential development strategy for the lunar orbit determination system is discussed to prepare for the future Korea's lunar missions. Prior to the discussion of this preliminary development strategy, technical models of foreign agencies for the lunar orbit determination system, tracking networks to measure the orbit, and collaborative efforts to verify system performance are reviewed in detail with a short summary of their lunar mission history. Covered foreign agencies are European Space Agency, Japan Aerospace Exploration Agency, Indian Space Research Organization and China National Space Administration. Based on the lessons from their experiences, the preliminary development strategy for Korea's future lunar orbit determination system is discussed with regard to the core technical issues of dynamic modeling, numerical integration, measurement modeling, estimation method, measurement system as well as appropriate data formatting for the interoperability among foreign agencies. Although only the preliminary development strategy has been discussed through this work, the proposed strategy will aid the Korean astronautical society while on the development phase of the future Korea's own lunar orbit determination system. Also, it is expected that further detailed system requirements or technical development strategies could be designed or established based on the current discussions.

  13. Next Generation of Telescopes or Dynamics Required to Determine if Exo-Moons have Prograde or Retrograde Orbits

    E-print Network

    Lewis, Karen M

    2014-01-01

    We survey the methods proposed in the literature for detecting moons of extrasolar planets in terms of their ability to distinguish between prograde and retrograde moon orbits, an important tracer of moon formation channel. We find that most moon detection methods, in particular, sensitive methods for detecting moons of transiting planets, cannot observationally distinguishing prograde and retrograde moon orbits. The prograde and retrograde cases can only be distinguished where dynamical evolution of the orbit due to e.g. three body effects is detectable, where one of the two cases is dynamically unstable or where new observational facilities which can implement a technique capable of differentiating the two cases, come on line. In particular, directly imaged planets are promising targets as repeated spectral and photometric measurements, required to determine moon orbit direction, could also be conducted with the primary interest of characterising the planet itself.

  14. High Fidelity Non-Gravitational Force Models for Precise and Accurate Orbit Determination of TerraSAR-X

    NASA Astrophysics Data System (ADS)

    Hackel, Stefan; Montenbruck, Oliver; Steigenberger, -Peter; Eineder, Michael; Gisinger, Christoph

    Remote sensing satellites support a broad range of scientific and commercial applications. The two radar imaging satellites TerraSAR-X and TanDEM-X provide spaceborne Synthetic Aperture Radar (SAR) and interferometric SAR data with a very high accuracy. The increasing demand for precise radar products relies on sophisticated validation methods, which require precise and accurate orbit products. Basically, the precise reconstruction of the satellite’s trajectory is based on the Global Positioning System (GPS) measurements from a geodetic-grade dual-frequency receiver onboard the spacecraft. The Reduced Dynamic Orbit Determination (RDOD) approach utilizes models for the gravitational and non-gravitational forces. Following a proper analysis of the orbit quality, systematics in the orbit products have been identified, which reflect deficits in the non-gravitational force models. A detailed satellite macro model is introduced to describe the geometry and the optical surface properties of the satellite. Two major non-gravitational forces are the direct and the indirect Solar Radiation Pressure (SRP). Due to the dusk-dawn orbit configuration of TerraSAR-X, the satellite is almost constantly illuminated by the Sun. Therefore, the direct SRP has an effect on the lateral stability of the determined orbit. The indirect effect of the solar radiation principally contributes to the Earth Radiation Pressure (ERP). The resulting force depends on the sunlight, which is reflected by the illuminated Earth surface in the visible, and the emission of the Earth body in the infrared spectra. Both components of ERP require Earth models to describe the optical properties of the Earth surface. Therefore, the influence of different Earth models on the orbit quality is assessed within the presentation. The presentation highlights the influence of non-gravitational force and satellite macro models on the orbit quality of TerraSAR-X.

  15. GPS satellite-to-satellite tracking for TOPEX/Poseidon precise orbit determination and gravity field model improvement

    NASA Astrophysics Data System (ADS)

    Schwintzer, P.; Kang, Z.; Reigber, Ch.; Zhu, S. Y.

    1995-10-01

    Satellite-to-satellite tracking (SST) between the high-altitude GPS satellites and a low-flying spacecraft, was realized for geodetic applications with the American/French altimeter mission TOPEX/Poseidon. This tracking scenario has already been tested by experimental GPS receivers with reduced performance on Landsat-4 and Landsat-5 some 10 years ago. Because of its capability to provide continuous data coverage, GPS space-based tracking for precise orbit restitution is superior to any ground-based tracking system. To investigate the accuracy potential offered by this observation system, the EPOS (Earth Parameter and Orbit System) software of GFZ Potsdam was extended to process GPS-SST data for precise TOPEX/Poseidon orbit determination and gravity field model improvement. The used observations are undifferenced pseudo-ranges and carrier phases as obtained from the on-board GPS receiver. In a two step approach the dynamic orbit determination method is applied with the precomputed ephemerides and clock parameters of the GPS satellites introduced as fixed parameters. The comparisons with precise TOPEX/Poseidon orbits computed by JPL in a different approach but using the same observations, and those computed by CNES/GRGS from DORIS-doppler and laser tracking data, reveal a homogeneous radial orbit consistency of about 3 cm and a total agreement of the adjusted satellite positions from different solutions within 12 cm. GPS-SST data covering one TOPEX/Poseidon orbit repeat cycle (10 days) are then incorporated into the normal equation system of the GRIM4 global gravity field model. As predictable from the very small observation residuals in the orbit adjustments, the contribution of this data set to the overall quality of the GRIM4 model is perceivable but not very significant, due to the relatively large altitude of the satellite.

  16. Analysis of Scaling Parameters of the Batch Unscented Transformation for Precision Orbit Determination using Satellite Laser Ranging Data

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Hyuk; Park, Sang-Young; Kim, Young-Rok; Park, Eun-Seo; Jo, Jung-Hyun; Lim, Hyung-Chul; Park, Jang-Hyun; Park, Jong-Uk

    2011-09-01

    The current study analyzes the effects of the scaling parameters of the batch unscented transformation on precision satellite orbit determination. Satellite laser ranging (SLR) data are used in the orbit determination algorithm, which consists of dynamics model, observation model and filtering algorithm composed of the batch unscented transformation. TOPEX/Poseidon SLR data are used by utilizing the normal point (NP) data observed from ground station. The filtering algorithm includes a repeated series of processes to determine the appropriate scaling parameters for the batch unscented transformation. To determine appropriate scaling parameters, general ranges of the scaling parameters of , , k, are established. Depending on the range settings, each parameter was assigned to the filtering algorithm at regular intervals. Appropriate scaling parameters are determined for observation data obtained from several observatories, by analyzing the relationship between tuning prope! rties of the scaling parameters and estimated orbit precision. The orbit determination of satellite using the batch unscented transformation can achieve levels of accuracy within several tens of cm with the appropriate scaling parameters. The analyses in the present study give insights into the roles of scaling parameters in the batch unscented transformation method.

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

    SciTech Connect

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

    2001-08-15

    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.

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

    E-print Network

    Cleveland, Durand Ennis

    1972-01-01

    vector. t n r 1 r2 Fig. 3. Position vector at central time Derivation [3, 10, 13] The two position vectors, along with their corresponding times tl and t , are given by r =xi+y j+zXat tl (9g) '+ '+ r=xr+yj+zkat t2. Expansion of equation (97..., the f and g equations may be used to find the velocity vector, From (191) and (192) E ? E u - B 2 1 (220) The values f and g may be found by f 1 - ? [1 ? cos (E ? E )j, a r 2 1 (221) and 50 g = 5t ? /a [E ? E ? sin (E ? E )], /3 2 1 2 1 I/ P...

  19. A Comprehensive Comparison Between Angles-Only Initial Orbit Determination Techniques 

    E-print Network

    Schaeperkoetter, Andrew Vernon

    2012-02-14

    suffered no adverse effects when additional observation sites were used and when the observation intervals were unequal. Lastly for the case when the observer is in space, it was found that typically the Gooding method performed the best if a good estimate...

  20. FM stars II: a Fourier view of pulsating binary stars - determining binary orbital parameters photometrically for highly eccentric cases

    NASA Astrophysics Data System (ADS)

    Shibahashi, Hiromoto; Kurtz, Donald W.; Murphy, Simon J.

    2015-07-01

    Continuous and precise space-based photometry has made it possible to measure the orbital frequency modulation of pulsating stars in binary systems with extremely high precision over long time spans. Frequency modulation caused by binary orbital motion manifests itself as a multiplet with equal spacing of the orbital frequency in the Fourier transform. The amplitudes and phases of the peaks in these multiplets reflect the orbital properties, hence the orbital parameters can be extracted by analysing such precise photometric data alone. We derive analytically the theoretical relations between the multiplet properties and the orbital parameters, and present a method for determining these parameters, including the eccentricity and the argument of periapsis, from a quintuplet or a higher order multiplet. This is achievable with the photometry alone, without spectroscopic radial velocity measurements. We apply this method to Kepler mission data of KIC 8264492, KIC 9651065, and KIC 10990452, each of which is shown to have an eccentricity exceeding 0.5. Radial velocity curves are also derived from the Kepler photometric data. We demonstrate that the results are in good agreement with those obtained by another technique based on the analysis of the pulsation phases.

  1. A comparison of operationally determined atmospheric densities from satellite orbit solutions and the exospheric temperature from the Jacchia-Roberts model

    Microsoft Academic Search

    D. T. Ward; E. A. Smith; M. C. Phenneger

    1990-01-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  3. A homotopy continuation method for general preliminary orbit determination and special application to the Tracking and Data Relay Satellite System

    NASA Technical Reports Server (NTRS)

    Smith, R. L.; Huang, C. Y.

    1985-01-01

    A recent mathematical technique for solving systems of equations is applied in a very general way to the orbit determination problem. The use of this technique, the homotopy continuation method, was motivated by the possible need to perform preliminary orbit determination in the Tracking and Data Relay Satellite System (TDRSS), using range and Doppler tracking alone. In the formulation studied here, a set of six tracking observations is continuously transformed from a set with known solutions to the given set with unknown solutions, and the corresponding orbit state vector is followed from the a priori orbit state to the solution orbit states. A modular numerical algorithm is developed to follow the state vector. The technique is formulated and then tested, using both real and simulated tracking, with positive results. Direct comparisons show that the basic method has a much larger radius of convergence than standard or simply modified Newton-Raphson methods. An extension of the basic method is formulated that is expected to produce a global method.

  4. Metrology, attitude, and orbit determination for spaceborne interferometric synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Duren, Riley M.; Wong, Ed; Breckenridge, Bill; Shaffer, Scott J.; Duncan, Courtney; Tubbs, Eldred F.; Salomon, Phil M.

    1998-07-01

    The Shuttle Radar Topography Mission (SRTM), scheduled for an 11 day Space Shuttle flight in 1999, will use an Interferometric Synthetic Aperture Radar instrument to produce a near-global digital elevation map of the earth's land surface with 16 m absolute vertical height accuracy at 30 meter postings. SRTM will achieve the required interferometric baseline by extending a receive-only radar antenna on a 60 meter deployable mast from the shuttle payload bay. Continuous measurement of the interferometric baseline length, attitude, and position is required at the 2 mm, 9 arcsec, and 1 m levels, respectively, in order to obtain the desired height accuracy. The attitude and orbit determination avionics (AODA) subsystem will provide these functions for SRTM. The AODA flight sensor complement includes electro-optical metrology sensor, a star tracker, an inertial reference unit, GPS receivers, plus supporting electronics and computers. AODA ground processing computers will support SRTM system performance evaluation during the mission and baseline reconstruction after the mission. The final AODA data products will be combined with the radar data to reconstruct the height information necessary for topographic map generation. A description of the AODA system architecture, error budgets, and the major issues involved with measuring large space structures are presented.

  5. 32 CFR 320.8 - Appeal of initial adverse agency determination on correction or amendment.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...Department of Defense (Continued) OFFICE OF THE SECRETARY OF DEFENSE (CONTINUED) PRIVACY PROGRAM NATIONAL GEOSPATIAL-INTELLIGENCE AGENCY (NGA) PRIVACY § 320.8 Appeal of initial adverse agency determination on correction or...

  6. 32 CFR 320.8 - Appeal of initial adverse agency determination on correction or amendment.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...Department of Defense (Continued) OFFICE OF THE SECRETARY OF DEFENSE (CONTINUED) PRIVACY PROGRAM NATIONAL GEOSPATIAL-INTELLIGENCE AGENCY (NGA) PRIVACY § 320.8 Appeal of initial adverse agency determination on correction or...

  7. 32 CFR 320.8 - Appeal of initial adverse agency determination on correction or amendment.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...Department of Defense (Continued) OFFICE OF THE SECRETARY OF DEFENSE (CONTINUED) PRIVACY PROGRAM NATIONAL GEOSPATIAL-INTELLIGENCE AGENCY (NGA) PRIVACY § 320.8 Appeal of initial adverse agency determination on correction or...

  8. 40 CFR 179.110 - Determination by Administrator to review initial decision.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    Within 10 days following the expiration of the time for filing exceptions (including any extensions), the Administrator may file with the hearing clerk, and serve on the parties, a notice of the Administrator's determination to review the initial...

  9. 42 CFR 405.904 - Medicare initial determinations, redeterminations and appeals: General description.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Medicare initial determinations, redeterminations...904 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES MEDICARE PROGRAM FEDERAL HEALTH...

  10. 42 CFR 405.904 - Medicare initial determinations, redeterminations and appeals: General description.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 false Medicare initial determinations, redeterminations...904 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES MEDICARE PROGRAM FEDERAL HEALTH...

  11. 42 CFR 405.904 - Medicare initial determinations, redeterminations and appeals: General description.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Medicare initial determinations, redeterminations...904 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES MEDICARE PROGRAM FEDERAL HEALTH...

  12. 42 CFR 405.904 - Medicare initial determinations, redeterminations and appeals: General description.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Medicare initial determinations, redeterminations...904 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES MEDICARE PROGRAM FEDERAL HEALTH...

  13. 42 CFR 405.904 - Medicare initial determinations, redeterminations and appeals: General description.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 false Medicare initial determinations, redeterminations...904 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES MEDICARE PROGRAM FEDERAL HEALTH...

  14. 49 CFR 7.31 - What time limits apply to DOT with respect to initial determinations?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 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...

  15. Pioneer 10 and 11 orbit determination analysis shows no discrepancy with Newton-Einstein laws of gravity

    NASA Astrophysics Data System (ADS)

    Modenini, D.; Tortora, P.

    2014-07-01

    The present work describes our investigation of the navigation anomaly of the Pioneer 10 and 11 probes which became known as the Pioneer Anomaly. It appeared as a linear drift in the Doppler data received by the spacecraft, which has been ascribed to an approximately constant Sunward acceleration of about 8.5×10-13 km/s2. Since then, the existence of the anomaly has been confirmed independently by several groups and a large effort was devoted to find its origin. Recently, different analyses were published where the authors claimed the acceleration due to anisotropic thermal emission to be the most likely cause of the unexplained acceleration. Here we report the methodology and the results of an independent study carried out in the last years, aimed at supporting the thermal origin of the anomaly. This work consists of two main parts: thermal modeling of the spacecraft throughout its trajectory, and orbit determination analysis. Based on existing documentation and published telemetry data, we built a thermal finite element model of the spacecraft, whose complexity has been constrained to a degree allowing for sensitivity analysis, leading to the computation of its formal uncertainty. The trajectory analysis and orbit determination were carried out using NASA/JPL's Orbit Determination Program, and our results show that orbital solutions are achieved that do not require the addition of any "unknown" acceleration other than that of thermal origin.

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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.

  17. Proposal of application of same beam VLBI measurements in precision orbit determination of lunar orbiter and return capsule and lunar gravity field simulation in Chang’E-3 mission

    Microsoft Academic Search

    Jianguo Yan; Fei Li; Qinghui Liu; Jinsong Ping; Zhen Zhong; Jinling Li

    2011-01-01

    High accuracy differenced phase delay can be obtained by observing multiple point frequencies of two spacecraft using the same beam Very Long Baseline Interferometry (VLBI) technology. Its contribution in lunar spacecraft precision orbit determination has been performed during the Japanese lunar exploration mission SELENE. In consideration that there will be an orbiter and a return capsule flying around the moon

  18. 20 CFR 418.1230 - What is the effective date of an income-related monthly adjustment amount initial determination...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...adjustment amount initial determination that is based on a more...Monthly Adjustment Amount Determinations Using A More Recent Tax...adjustment amount initial determination that is based on a more...January 1, 2007, our initial determination is effective on...

  19. Orbital moment determination of simple transition metal oxides using magnetic X-ray diffraction

    Microsoft Academic Search

    W. Neubeck; C. Vettier; F. de Bergevin; F. Yakhou; D. Mannix; L. Ranno; T. Chatterji

    2001-01-01

    Non-resonant magnetic X-ray scattering (NRXMS) is a unique tool allowing the separation of the spin and orbital moment density contributions to the total magnetization density. This method has been successfully applied to the simple transition metal oxides: MnO, CoO and CuO. It is common habit to consider the orbital moment of these oxides to be quenched by the cubic crystal

  20. Nonconservative force model parameter estimation strategy for TOPEX\\/Poseidon precision orbit determination

    Microsoft Academic Search

    S. B. Luthcke; J. A. Marshall

    1992-01-01

    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

  1. Diplopia and variable ptosis as the sole initial findings in a case of orbital plasmacytoma and multiple myeloma.

    PubMed

    Galea, Martin; McMillan, Nigel; Weir, Clifford

    2015-05-01

    Plasmacytomas are monoclonal plasma cell tumors. They represent 3% of all orbital tumors. We present an unusual case of orbital plasmacytoma and advanced multiple myeloma where the sole presenting symptoms were those of diplopia and ptosis. Clinical examination revealed right hypertropia and variable left upper lid ptosis but no proptosis. The visual acuity and the rest of the ocular examination were normal in both eyes. An MRI scan of the brain and orbits revealed a frontal bone lesion consistent with a plasmacytoma. A bone marrow biopsy showed a light chain multiple myeloma with free lambda light chains. Although the literature reports diplopia and ptosis as being clinical features of orbital plasmacytomas, to our knowledge this is the first reported case where these symptoms were the only presenting features, despite widespread disease. PMID:24164055

  2. Analytical second-order drag theory with application for lifetime determination of artificial satellites in low earth orbits

    Microsoft Academic Search

    F. A. Abd El-salam; L. Sehnal

    2005-01-01

    A second-order atmospheric drag theory based on the usage of TD88 model is constructed. It is developed to the second order in terms of TD88 small parameters Kn,j. The short periodic perturbations, of all orbital elements, are evaluated. The secular perturbations of the semi-major axis and of the eccentricity are obtained. The theory is applied to determine the lifetime of

  3. The Use of Laser Altimetry in the Orbit and Attitude Determination of Mars Global Surveyor

    NASA Technical Reports Server (NTRS)

    Rowlands, D. D.; Pavlis, D. E.; Lemoine, F. G.; Neumann, G. A.; Luthcke, S. B.

    1999-01-01

    Altimetry from the Mars Observer Laser Altimeter (MOLA) which is carried on board Mars Global Surveyor (MGS) has been analyzed for the period of the MOS mission known as Science Phasing Orbit 1 (SPO-1). We have used these altimeter ranges to improve orbit and attitude knowledge for MGS. This has been accomplished by writing crossover constraint equations that have been derived from short passes of MOLA data. These constraint equations differ from traditional Crossover constraints and exploit the small foot print associated with laser altimetry.

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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.

  5. Accurate orbit determination strategies for the tracking and data relay satellites

    Microsoft Academic Search

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

    1995-01-01

    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

  6. Orbit determination error analysis and station-keeping for liberation point trajectories

    Microsoft Academic Search

    Steven Craig Gordon

    1991-01-01

    In the elliptic restricted three-body problem (ER3BP), the two primary masses are assumed to be in known elliptic orbits about their common center of mass. The third (infinitesimal) mass may be positioned near one of the five known Lagrange points located in the coordinate system rotating with the primaries. The bounded motion of the infinitesimal mass relative to a Lagrange

  7. Near-real time orbit determination for the GPS, CHAMP, GRACE, TerraSAR-X, and TanDEM-X satellites

    Microsoft Academic Search

    Grzegorz Michalak; Rolf Koenig

    2010-01-01

    The GFZ German Research Centre for Geosciences developed a near-real time (NRT) orbit gen-eration system for GPS and Low Earth Orbiting (LEO) satellites to support radio occultation data processing for the CHAMP, GRACE, Terra-SAR-X and the upcoming TanDEM-X mis-sions and fast baseline determination for the TanDEM-X mission. Precise NRT orbits are being generated for the CHAMP and GRACE-A satellites since

  8. 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)

    Microsoft Academic Search

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

    1990-01-01

    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

  9. J-Adaptive estimation with estimated noise statistics. [for orbit determination

    NASA Technical Reports Server (NTRS)

    Jazwinski, A. H.; Hipkins, C.

    1975-01-01

    The J-Adaptive estimator described by Jazwinski and Hipkins (1972) is extended to include the simultaneous estimation of the statistics of the unmodeled system accelerations. With the aid of simulations it is demonstrated that the J-Adaptive estimator with estimated noise statistics can automatically estimate satellite orbits to an accuracy comparable with the data noise levels, when excellent, continuous tracking coverage is available. Such tracking coverage will be available from satellite-to-satellite tracking.

  10. Onboard orbit determination using GPS observations based on the unscented Kalman filter

    Microsoft Academic Search

    Eun-Jung Choi; Jae-Cheol Yoon; Byoung-Sun Lee; Sang-Young Park; Kyu-Hong Choi

    2010-01-01

    Spaceborne GPS receivers are used for real-time navigation by most low Earth orbit (LEO) satellites. In general, the position and velocity accuracy of GPS navigation solutions without a dynamic filter are 25m (1?) and 0.5m\\/s (1?), respectively. However, GPS navigation solutions, which consist of position, velocity, and GPS receiver clock bias, have many abnormal excursions from the normal error range

  11. Precision Orbit Determination Standards for the Jason Series of Altimeter Missions

    Microsoft Academic Search

    L. Cerri; J. P. Berthias; W. I. Bertiger; B. J. Haines; F. G. Lemoine; F. Mercier; J. C. Ries; P. Willis; N. P. Zelensky; M. Ziebart

    2010-01-01

    The Jason-1 altimeter satellite and its follow-on mission Jason-2\\/OSTM were launched in December 2001 and June 2008, respectively, to provide the scientific community with a high-accuracy continuous record of observations of the ocean surface topography. Both missions carry on board three state-of-the-art tracking systems (DORIS, GPS, SLR) to meet the requirement of better-than-1.5 cm radial accuracy for the operational orbit

  12. Determination of the area and mass distribution of orbital debris fragments

    Microsoft Academic Search

    Gautam D. Badhwar; Phillip D. Anz-Meador

    1989-01-01

    An important factor in modeling the orbital debris environment is the loss rate of debris due to atmospheric drag and luni\\/solar perturbations. An accurate knowledge of the area-to-mass ratio of debris fragments is required for the calculation of the effect of atmospheric drag. In general, this factor is unknown and assumed values are used. However, this ratio can be calculated

  13. Magnitude determination using initial P waves: A single-station Yih-Min Wu,1

    E-print Network

    Wu, Yih-Min

    Magnitude determination using initial P waves: A single-station approach Yih-Min Wu,1 Hsin-Yi Yen,1 the magnitudes of earthquakes and the properties of the first three seconds of the P waves at a single station within 100-km epicentral distance, we found a linear correlation between the magnitudes

  14. The fertilizing value of livestock waste is hardly determined considering its initial variability, the

    E-print Network

    Paris-Sud XI, Université de

    it is exchanged, manure is mainly in this form. The quantity of solid waste can be estimated with the classicalThe fertilizing value of livestock waste is hardly determined considering its initial variability measurements of liquid waste outflows and Near Infrared spectrometry technique have been implemented

  15. 20 CFR 418.3615 - Will we mail you a notice of the initial determination?

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 false Will we mail you a notice of the...418.3615 Will we mail you a notice of the initial...determination? (a) We will mail a written notice of...you at your last known address. Generally, we will not send a notice if...

  16. 20 CFR 418.3615 - Will we mail you a notice of the initial determination?

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 false Will we mail you a notice of the...418.3615 Will we mail you a notice of the initial...determination? (a) We will mail a written notice of...you at your last known address. Generally, we will not send a notice if...

  17. 20 CFR 418.3615 - Will we mail you a notice of the initial determination?

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 false Will we mail you a notice of the...418.3615 Will we mail you a notice of the initial...determination? (a) We will mail a written notice of...you at your last known address. Generally, we will not send a notice if...

  18. 20 CFR 418.3615 - Will we mail you a notice of the initial determination?

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 false Will we mail you a notice of the...418.3615 Will we mail you a notice of the initial...determination? (a) We will mail a written notice of...you at your last known address. Generally, we will not send a notice if...

  19. 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)

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

    1990-01-01

    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.

  20. 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 Astrophysics Data System (ADS)

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

    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.

  1. The Synergy of Direct Imaging and Astrometry for Orbit Determination of Exo-Earths

    NASA Astrophysics Data System (ADS)

    Shao, Michael; Catanzarite, Joseph; Pan, Xiaopei

    2010-09-01

    The holy grail of exoplanet searches is an exo-Earth, an Earth mass planet in the habitable zone (HZ) around a nearby star. Mass is one of the most important characteristics of a planet and can only be measured by observing the motion of the star around the planet-star center of gravity. The planet's orbit can be measured either by imaging the planet at multiple epochs or by measuring the position of the star at multiple epochs by space-based astrometry. The measurement of an exoplanet's orbit by direct imaging is complicated by a number of factors. One is the inner working angle (IWA). A space coronagraph or interferometer imaging an exo-Earth can separate the light from the planet from the light from the star only when the star-planet separation is larger than the IWA. Second, the apparent brightness of a planet depends on the orbital phase. A single image of a planet cannot tell us whether the planet is in the HZ or distinguish whether it is an exo-Earth or a Neptune-mass planet. Third is the confusion that may arise from the presence of multiple planets. With two images of a multiple planet system, it is not possible to assign a dot to a planet based only on the photometry and color of the planet. Finally, the planet-star contrast must exceed a certain minimum value in order for the planet to be detected. The planet may be unobservable even when it is outside the IWA, such as when the bright side of the planet is facing away from us in a "crescent" phase. In this paper we address the question: "Can a prior astrometric mission that can identify which stars have Earth-like planets significantly improve the science yield of a mission to image exo-Earths?" In the case of the Occulting Ozone Observatory, a small external occulter mission that cannot measure spectra, we find that the occulter mission could confirm the orbits of ~4 to ~5 times as many exo-Earths if an astrometric mission preceded it to identify which stars had such planets. In the case of an internal coronagraph we find that a survey of the nearest ~60 stars could be done with a telescope half the size if an astrometric mission had first identified the presence of Earth-like planets in the HZ and measured their orbital parameters.

  2. THE SYNERGY OF DIRECT IMAGING AND ASTROMETRY FOR ORBIT DETERMINATION OF EXO-EARTHS

    SciTech Connect

    Shao, Michael; Catanzarite, Joseph; Pan Xiaopei, E-mail: michael.shao@jpl.nasa.go, E-mail: joseph.catanzarite@jpl.nasa.go, E-mail: xiaopei.pan@jpl.nasa.go [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr, Pasadena, CA 91109 (United States)

    2010-09-01

    The holy grail of exoplanet searches is an exo-Earth, an Earth mass planet in the habitable zone (HZ) around a nearby star. Mass is one of the most important characteristics of a planet and can only be measured by observing the motion of the star around the planet-star center of gravity. The planet's orbit can be measured either by imaging the planet at multiple epochs or by measuring the position of the star at multiple epochs by space-based astrometry. The measurement of an exoplanet's orbit by direct imaging is complicated by a number of factors. One is the inner working angle (IWA). A space coronagraph or interferometer imaging an exo-Earth can separate the light from the planet from the light from the star only when the star-planet separation is larger than the IWA. Second, the apparent brightness of a planet depends on the orbital phase. A single image of a planet cannot tell us whether the planet is in the HZ or distinguish whether it is an exo-Earth or a Neptune-mass planet. Third is the confusion that may arise from the presence of multiple planets. With two images of a multiple planet system, it is not possible to assign a dot to a planet based only on the photometry and color of the planet. Finally, the planet-star contrast must exceed a certain minimum value in order for the planet to be detected. The planet may be unobservable even when it is outside the IWA, such as when the bright side of the planet is facing away from us in a 'crescent' phase. In this paper we address the question: 'Can a prior astrometric mission that can identify which stars have Earth-like planets significantly improve the science yield of a mission to image exo-Earths?' In the case of the Occulting Ozone Observatory, a small external occulter mission that cannot measure spectra, we find that the occulter mission could confirm the orbits of {approx}4 to {approx}5 times as many exo-Earths if an astrometric mission preceded it to identify which stars had such planets. In the case of an internal coronagraph we find that a survey of the nearest {approx}60 stars could be done with a telescope half the size if an astrometric mission had first identified the presence of Earth-like planets in the HZ and measured their orbital parameters.

  3. The dynamics of global positioning system orbits and the determination of precise ephemerides

    NASA Technical Reports Server (NTRS)

    Colombo, Oscar L.

    1989-01-01

    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.

  4. Determination of M2 ocean tide parameters from satellite orbit perturbations

    Microsoft Academic Search

    Clyde C. Goad; Bruce C. Douglas

    1977-01-01

    A sequence of 80 mean inclinations obtained from successive 2-day orbital arcs of a U.S. Navy navigation satellite (1967-92A) has been used to obtain M2 ocean tide parameters. By assuming solid tide parameters of k2=0.30 and delta2=0° the implied observation equation on terms of order 2 and degree 2, 4, 6, ..., is (3.8''+\\/-0.60) ×10-2 sin [wt+(331°+\\/-10°)]= (0.99''\\/cm) ×10-2 C22+

  5. What really went wrong? Root cause determination study and improvement initiative results.

    PubMed

    Kiihne, Gregg M

    2008-11-15

    Many incident investigations stop before identifying the real root cause or all root causes. In 2004 with the implementation of a new corporate-wide incident reporting electronic database, an evaluation was made possible as to the quality of incident investigations and reports at all sites within the case study organization. After reviewing almost 1,000 incident reports, the Occupational and Process Safety expertise teams in this organization determined a need for improvement in the determination of the real Root Causes of the incidents and development of appropriate Corrective Actions. A communication and training initiative across multiple functional groups ensued to enable all sites within the organization to better understand why incidents were happening and to develop Corrective Actions to successfully prevent recurrence of the same or related incidents. This paper will give a brief background of the initiative, demonstrate what activities were undertaken and illustrate the success of this approach. PMID:18374484

  6. Determination of dynamic fracture-initiation toughness using a novel impact bend test procedure

    Microsoft Academic Search

    T. Yokoyama

    1993-01-01

    A novel impact bend test procedure is described for determining the dynamic fracture-initiation toughness, K[sub Id], at a loading rate (stress intensity factor rate), K[sub I], of the order of 10[sup 6] MPa [radical]m\\/s. A special arrangement of the split Hopkinson pressure bar is adopted to measure accurately dynamic loads applied to a fatigue-precracked bend specimen. The dynamic stress intensity

  7. Geostationary Orbit Surveillance Using the Unscented Kalman Filter and the Analytical Orbit Model

    NASA Astrophysics Data System (ADS)

    Roh, Kyoung-Min; Park, Eun-Seo; Choi, Byung-Kyu

    2011-09-01

    A strategy for geostationary orbit (or geostationary earth orbit [GEO]) surveillance based on optical angular observations is presented in this study. For the dynamic model, precise analytical orbit model developed by Lee et al. (1997) is used to improve computation performance and the unscented Kalman filer (UKF) is applied as a real-time filtering method. The UKF is known to perform well under highly nonlinear conditions such as surveillance in this study. The strategy that combines the analytical orbit propagation model and the UKF is tested for various conditions like different level of initial error and different level of measurement noise. The dependencies on observation interval and number of ground station are also tested. The test results shows that the GEO orbit determination based on the UKF and the analytical orbit model can be applied to GEO orbit tracking and surveillance effectively.

  8. 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)

    Sekanina, Zdenek; Chodas, Paul W.

    2012-10-01

    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.

  9. COMET C/2011 W3 (LOVEJOY): ORBIT DETERMINATION, OUTBURSTS, DISINTEGRATION OF NUCLEUS, DUST-TAIL MORPHOLOGY, AND RELATIONSHIP TO NEW CLUSTER OF BRIGHT SUNGRAZERS

    SciTech Connect

    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

    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.

  10. A qualitative study of determinants of PTSD treatment initiation in veterans.

    PubMed

    Sayer, Nina A; Friedemann-Sanchez, Greta; Spoont, Michele; Murdoch, Maureen; Parker, Louise E; Chiros, Christine; Rosenheck, Robert

    2009-01-01

    Although there are effective treatments for Posttraumatic Stress Disorder (PTSD), many PTSD sufferers wait years to decades before seeking professional help, if they seek it at all. An understanding of factors affecting treatment initiation for PTSD can inform strategies to promote help-seeking. We conducted a qualitative study to identify determinants of PTSD treatment initiation among 44 U.S. military veterans from the Vietnam and Afghanistan/Iraq wars; half were and half were not receiving treatment. Participants described barriers to and facilitators of treatment initiation within themselves, the post-trauma socio-cultural environment, the health care and disability systems, and their social networks. Lack of knowledge about PTSD was a barrier that occurred at both the societal and individual levels. Another important barrier theme was the enduring effect of experiencing an invalidating socio-cultural environment following trauma exposure. In some cases, system and social network facilitation led to treatment initiation despite individual-level barriers, such as beliefs and values that conflicted with help-seeking. Our findings expand the dominant model of service utilization by explicit incorporation of factors outside the individual into a conceptual framework of PTSD treatment initiation. Finally, we offer suggestions regarding the direction of future research and the development of interventions to promote timely help-seeking for PTSD. PMID:19821647

  11. Trajectory determination support and analysis for ISEE-3 from halo orbit to escape from the earth/moon system

    NASA Technical Reports Server (NTRS)

    Joyce, J. B.; Schanzle, A. F.

    1984-01-01

    The analyses performed in altering the ISEE-3 spacecraft path from a liberation point to a helicocentric orbit for intercepting the Giacobini-Zimmer cometary tail are reviewed. The initial calculations considered the expected accuracy, the best temporal lengths to be used for the calculations and the maneuver points. The early maneuvers were also constrained to a maximum number of crossings of the terrestrial magnetotail for data collection purposes. Three earth-based tracking stations trajectory data collection schedules were projected, and programs were prepared for comparing tracking data with predictions. Delta- V maneuvers were set for perigee locations in order to conserve fuel. A 21-day span was selected for tracking, expect during maneuver periods. Accuracies of 0.1-10 km and 0.3-2.0 cm/sec were obtained.

  12. Determining Spent Nuclear Fuel's Plutonium Content, Initial Enrichment, Burnup, and Cooling Time

    SciTech Connect

    Cheatham, Jesse R [ORNL] [ORNL; Francis, Matthew W [ORNL] [ORNL

    2011-01-01

    The Next Generation of Safeguards Initiative is examining nondestructive assay techniques to determine the total plutonium content in spent nuclear fuel. The goal of this research was to develop new techniques that can independently verify the plutonium content in a spent fuel assembly without relying on an operator's declarations. Fundamentally this analysis sought to answer the following questions: (1) do spent fuel assemblies contain unique, identifiable isotopic characteristics as a function of their burnup, cooling time, and initial enrichment; (2) how much variation can be seen in spent fuel isotopics from similar and dissimilar reactor power operations; and (3) what isotopes (if any) could be used to determine burnup, cooling time, and initial enrichment? To answer these questions, 96,000 ORIGEN cases were run that simulated typical two-cycle operations with burnups ranging from 21,900 to 72,000 MWd/MTU, cooling times from 5 to 25 years, and initial enrichments between 3.5 and 5.0 weight percent. A relative error coefficient was determined to show how numerically close a reference solution has to be to another solution for the two results to be indistinguishable. By looking at the indistinguishable solutions, it can be shown how a precise measurement of spent fuel isotopics can be inconclusive when used in the absence of an operator's declarations. Using this Method of Indistinguishable Solutions (MIS), we evaluated a prominent method of nondestructive analysis - gamma spectroscopy. From this analysis, a new approach is proposed that demonstrates great independent forensic examination potential for spent nuclear fuel by examining both the neutron emissions of Cm-244 and the gamma emissions of Cs-134 and Eu-154.

  13. Prevalence and determinants of smoking initiation among school students in Bosnia and Herzegovina.

    PubMed

    Racic, Maja; Tanovic, Sanja; Joksimovic, Vedrana R; Joksimovic, Bojan N; Ristic, Sinisa

    2014-11-26

    Abstract Background: Tobacco smoking amongst the young is a matter of public health concern because of the immediate and long-term health consequences associated with tobacco use, such as asthma, cancers, and cardiovascular diseases. The purpose of this study was to identify the determinants of smoking initiation among a sample of high school students in Bosnia and Herzegovina. Methods: The study was conducted among 198 high school students in Zvornik, Bosnia and Herzegovina, during April 2013. A self-administered, pre-tested, structured, close-ended questionnaire was used for data collection. Results: Fourth grade students mainly initiated smoking in high school (45%), while the majority of third and second grade students initiated smoking in primary school. Among students who smoke, an average duration of the smoking habit was <2 years. A multivariate analysis showed that males were 5.27 times more likely to have initiated smoking. For every unit increase in pro-smoking attitude towards smoking, students were 5.3 times more likely to have initiated smoking. Those with parents and friends who are smokers were 6.106 and 5.175 times, respectively, more likely to have initiated smoking. Conclusion: This study indicates that a high proportion of 15-18 year olds in the town of Zvornik are current smokers. Gender, age, and parent and peer influence were identified as important associations with smoking. Interventions should not only be confined to the secondary school environment but they should also extend to their places of residence so that influences in the home environment and social surroundings that contribute to tobacco use are also tackled. PMID:25427060

  14. International Low-Earth-Orbit Spacecraft Materials Test Program Initiated for Better Prediction of Durability and Performance

    NASA Technical Reports Server (NTRS)

    Rutledge, Sharon K.

    1999-01-01

    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.

  15. Orbital angular momentum in electron diffraction and its use to determine chiral crystal symmetries

    E-print Network

    Juchtmans, Roeland

    2015-01-01

    In this work we present an alternative way to look at electron diffraction in a transmission electron microscope. In stead of writing the scattering amplitude in Fourier space as a set of plane waves, we use the cylindrical Fourier transform to describe the scattering amplitude in a basis of orbital angular momentum (OAM) eigenstates. We show how working in this framework can be very convenient when investigating e.g. rotation and screw axis symmetries. For the latter we find selection rules on the OAM-coefficients that unambiguously reveal the handedness of the screw axis. Detecting the OAM-coefficients of the scattering amplitude thus offers the possibility to detect the handedness of crystals without the need for dynamical simulations, the thickness of the sample nor the exact crystal structure. We propose an experimental setup to measure the OAM-components where an image of the crystal is taken after inserting a spiral phase plate in the diffraction plane and perform mulsti-slice simulations on $\\alpha$-q...

  16. Determination of Vancomycin Pharmacokinetics in Neonates To Develop Practical Initial Dosing Recommendations

    PubMed Central

    Kim, Julianne; Iaboni, Dolores C.; Walker, Scott E.; Elligsen, Marion; Dunn, Michael S.; Allen, Vanessa G.; Simor, Andrew

    2014-01-01

    Variability in neonatal vancomycin pharmacokinetics and the lack of consensus for optimal trough concentrations in neonatal intensive care units pose challenges to dosing vancomycin in neonates. Our objective was to determine vancomycin pharmacokinetics in neonates and evaluate dosing regimens to identify whether practical initial recommendations that targeted trough concentrations most commonly used in neonatal intensive care units could be determined. Fifty neonates who received vancomycin with at least one set of steady-state levels were evaluated retrospectively. Mean pharmacokinetic values were determined using first-order pharmacokinetic equations, and Monte Carlo simulation was used to evaluate initial dosing recommendations for target trough concentrations of 15 to 20 mg/liter, 5 to 20 mg/liter, and ?20 mg/liter. Monte Carlo simulation revealed that dosing by mg/kg of body weight was optimal where intermittent dosing of 9 to 12 mg/kg intravenously (i.v.) every 8 h (q8h) had the highest probability of attaining a target trough concentration of 15 to 20 mg/liter. However, continuous infusion with a loading dose of 10 mg/kg followed by 25 to 30 mg/kg per day infused over 24 h had the best overall probability of target attainment. Initial intermittent dosing of 9 to 15 mg/kg i.v. q12h was optimal for target trough concentrations of 5 to 20 mg/liter and ?20 mg/liter. In conclusion, we determined that the practical initial vancomycin dose of 10 mg/kg vancomycin i.v. q12h was optimal for vancomycin trough concentrations of either 5 to 20 mg/liter or ?20 mg/liter and that the same initial dose q8h was optimal for target trough concentrations of 15 to 20 mg/liter. However, due to large interpatient vancomycin pharmacokinetic variability in neonates, monitoring of serum concentrations is recommended when trough concentrations between 15 and 20 mg/liter or 5 and 20 mg/liter are desired. PMID:24614381

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

    NASA Technical Reports Server (NTRS)

    Lemoine, F. G.; Rowlands, D. D.; Luthcke, S. B.; Zelensky, N. P.; Chinn, D. S.; Pavlis, D. E.; Marr, G. C.

    2001-01-01

    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.

  18. Determination of dynamic fracture-initiation toughness using a novel impact bend test procedure

    SciTech Connect

    Yokoyama, T. (Osaka Univ. (Japan). Faculty of Engineering Okayama Univ. of Science (Japan). Dept. of Mechanical Engineering)

    1993-11-01

    A novel impact bend test procedure is described for determining the dynamic fracture-initiation toughness, K[sub Id], at a loading rate (stress intensity factor rate), K[sub I], of the order of 10[sup 6] MPa [radical]m/s. A special arrangement of the split Hopkinson pressure bar is adopted to measure accurately dynamic loads applied to a fatigue-precracked bend specimen. The dynamic stress intensity factor history for the bend specimen is evaluated by means of a dynamic finite element technique. The onset of crack initiation is detected using a string gage attached on the side of the specimen near a crack tip. The value of K[sub Id] is determined from the critical dynamic stress intensity factor at crack initiation. A series of dynamic fracture tests is carried out on a 7075-T6 aluminum alloy, a Ti-6246 alloy and an AISI 4340 steel. The K[sub Id] values obtained for the three structural materials are compared with the corresponding values obtained under quasi-static loading conditions.

  19. Orbit determination modelling analysis using GPS including perturbations due to geopotential coefficients of high degree and order, solar radiation pressure and luni-solar attraction

    NASA Astrophysics Data System (ADS)

    Vilhena de Moraes, Rodolpho; Cristiane Pardal, Paula; Koiti Kuga, Helio

    The problem of orbit determination consists essentially of estimating parameter values that completely specify the body trajectory in the space, processing a set of information (measure-ments) from this body. Such observations can be collected through a conventional tracking network on Earth or through sensors like GPS. The Global Positioning System (GPS) is a powerful and low cost way to allow the computation of orbits for artificial Earth satellites. The Topex/Poseidon satellite is normally used as a reference for analyzing this system for space positioning. The orbit determination of artificial satellites is a nonlinear problem in which the disturbing forces are not easily modeled, like geopotential and direct solar radiation pressure. Through an onboard GPS receiver it is possible to obtain measurements (pseudo-range and phase) that can be used to estimate the state of the orbit. One intends to analyze the modeling of the orbit of an artificial satellite, using signals of the GPS constellation and least squares algorithms as a method of estimation, with the aim of analyzing the performance of the orbit estimation process. Accuracy is not the main goal; one pursues to verify how differences of modeling can affect the final accuracy of the orbit determination. To accomplish that, the following effects were considered: perturbations up to high degree and order for the geopoten-tial coefficients; direct solar radiation pressure, Sun attraction, and Moon attraction. It was also considered the position of the GPS antenna on the satellite body that, lately, consists of the influence of the satellite attitude motion in the orbit determination process. Although not presenting the ultimate accuracy, pseudo-range measurements corrected from ionospheric effects were considered enough to such analysis. The measurements were used to feed the batch least squares orbit determination process, in order to yield conclusive results about the orbit modeling issue. An application has been done, using such GPS data, for orbit determination of the Topex/Poseidon satellite, whose accurate ephemerides are freely available at Internet. It is shown that from a poor but acceptable modeling up to all effects included, the accuracy can vary from about 30m to 8m. Test results for short period (2 hours) and for long period (24 hours) are also shown.

  20. Burkitt Lymphoma with Initial Clinical Presentation due to Infiltration of the Central Nervous System and Eye Orbits

    PubMed Central

    Camilo, Gustavo Bittencourt; Machado, Dequitier Carvalho; de Oliveira, Celso Estevão; Lacerda, Letícia da Silva; de Oliveira, Romulo Varella; de França Silva, Monique; Lopes, Agnaldo José

    2014-01-01

    Patient: Male, 17 Final Diagnosis: Burkitt lymphoma Symptoms: Anisocoria, ipsilateral ptosis, opthalmoparesis, paresis Medication: — Clinical Procedure: — Specialty: Oncology Objective: Unusual clinical course Background: Burkitt lymphoma rarely affects the central nervous system and ocular region. Under these conditions, computed tomography and (particularly) magnetic resonance imaging of the skull increase the diagnostic accuracy, as they objectively show the topography of lesions and the effect of neoplasia on structures. Case Report: We report here the case of a 17-year-old male whose initial clinical manifestations were related to neurological impairment and to the ocular musculature and ocular innervation. The diagnosis of Burkitt lymphoma with leukemization and infiltration of the central nervous system was confirmed. Conclusions: In this case, it is important to recognize that the neuroimaging findings were fundamentally important in indicating the initial form of the disease and in directing the appropriate clinical management. PMID:25243420

  1. Dosimetry Determines the Initial OH Radical Concentration in Fast Photochemical Oxidation of Proteins (FPOP)

    NASA Astrophysics Data System (ADS)

    Niu, Ben; Zhang, Hao; Giblin, Daryl; Rempel, Don L.; Gross, Michael L.

    2015-05-01

    Fast photochemical oxidation of proteins (FPOP) employs laser photolysis of hydrogen peroxide to give OH radicals that label amino acid side-chains of proteins on the microsecond time scale. A method for quantitation of hydroxyl radicals after laser photolysis is of importance to FPOP because it establishes a means to adjust the yield of •OH, offers the opportunity of tunable modifications, and provides a basis for kinetic measurements. The initial concentration of OH radicals has yet to be measured experimentally. We report here an approach using isotope dilution gas chromatography/mass spectrometry (GC/MS) to determine quantitatively the initial •OH concentration (we found ~0.95 mM from 15 mM H2O2) from laser photolysis and to investigate the quenching efficiencies for various •OH scavengers.

  2. Integer Ambiguity Resolution for Low Earth Orbiting Spacecraft

    Microsoft Academic Search

    Y. T. Yoon; G. L. Kruizinga; K. Gold; G. Born; S. R. Nerem; M. M. Watkins

    2001-01-01

    This study is an attempt to resolve GPS integer phase ambiguities for two low Earth orbiting (LEO) spacecrafts, SAC-C and CHAMP. Integer ambiguity resolution holds great promise for improving orbit determination accuracy and reference frame realization using geodetic satellites. We initiated this study by examining the statistical distribution of the wide lane and narrow lane double-differenced GPS phase biases for

  3. The orbit of asteroid (99942) Apophis as determined from optical and radar observations

    NASA Astrophysics Data System (ADS)

    Vinogradova, T. A.; Kochetova, O. M.; Chernetenko, Yu. A.; Shor, V. A.; Yagudina, E. I.

    2008-08-01

    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.

  4. Method and apparatus for determining when to initiate cleaning of turbocharger turbine blades

    SciTech Connect

    Miller, R. A.; Condrac, E. J.

    1985-10-22

    A method and apparatus for determining when to initiate the cleaning of the turbine blades of a turbocharger is disclosed. The performance of the compressor portion of the turbocharger is monitored and upon a degradation in performance being detected it is indicated that fouling of the turbine blades has occurred. In response to this indication a water injection system is energized for supplying atomized water under high pressure to the exhaust gas powering the turbocharger to effectively clean the turbine blades. Means are provided for decreasing the speed of the turbocharger during the cleaning cycle to allow for an effective cleaning operation.

  5. A novel impact three-point bend test method for determining dynamic fracture-initiation toughness

    Microsoft Academic Search

    T. Yokoyama; K. Kishida

    1989-01-01

    A novel impact three-point bend test method has been developed for determining the dynamic fracture-initiation toughness,K\\u000a Id, over the range of loading rates\\u000a $$10^5 MPa\\\\sqrt m \\/s \\\\leqslant K_I \\\\leqslant 10^5 MPa\\\\sqrt m \\/s$$\\u000a . The split-Hopkinson pressure-bar technique is used to measure dynamic loads applied to a bend specimen with a fatigue precrack.\\u000a The stress-intensity-factor histories for the bend

  6. Gravity and Orbits: Orbits

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2006-11-01

    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.

  7. Application of orbital angular momentum to simultaneous determination of tilt and lateral

    E-print Network

    Dainty, Chris

    spectrum of a laser beam. Our theory explains the symmetries and properties of the spectrum under the influence of misalignments. We apply the theory to establish a reliable and efficient method for determining]. The phase of an optical vortex varies in a "screw-like" manner along the beam's axis of propagation

  8. GNSS antenna for precise orbit determination including S\\/C interference predictions

    Microsoft Academic Search

    Mikael Ohgren; Magnus Bonnedal; Per Ingvarson

    2011-01-01

    In this paper we present the antenna developed for the Sentinel-1 SAR, Sentinel-2 optical, and Sentinel-3 radar altimeter missions. These earth observation ESA missions require GNSS to localise measurements and to determine sea levels with cm accuracy as part of a radar altimeter system. A dual frequency GNSS antenna with good coverage, low loss and very low interference has been

  9. Automation of orbit determination functions for National Aeronautics and Space Administration (NASA)-supported satellite missions

    Microsoft Academic Search

    H. Mardirossian; K. Heuerman; A. Beri; M. V. Samii; C. E. Doll

    1989-01-01

    The Flight Dynamics Facility (FDF) at Goddard Space Flight Center (GSFC) provides spacecraft trajectory determination for a wide variety of National Aeronautics and Space Administration (NASA)-supported satellite missions, using the Tracking Data Relay Satellite System (TDRSS) and Ground Spaceflight and Tracking Data Network (GSTDN). To take advantage of computerized decision making processes that can be used in spacecraft navigation, the

  10. Determining the in-plane orientation of the ground-state orbital of CeCu2Si2.

    PubMed

    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

    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

  11. Limitations for near-real-time orbit and clock products and first results of a normal equation stacking approach for orbit and clock determination

    NASA Astrophysics Data System (ADS)

    Schoenemann, E.; Alfaro, P.; Springer, T.; Becker, M.; Dow, J.; Zandbergen, R.

    2009-04-01

    The Navigation Support Office at the European Space Operations Centre (ESA/ESOC) in Darmstadt, as one of the IGS-AC's, performs routinely precise orbit and clock estimation. We contribute to the common IGS-products, as ultra-rapid, rapid and final orbits and clocks, with latencies of 3 hours, 17 hours and 13 days. Furthermore, we are deeply involved in the IGS Real Time Pilot Project, to which we contribute with an experimental solution. Monitoring tasks, as for hazard mitigation and earth observation desire highly accurate orbits and clocks in near-real-time. Evaluating the products currently available in near-real-time, shows that the predicted orbits (ultra-rapid) provide an adequate accuracy whereas clocks are the weak point. The quality of the prediction of clocks is decreasing rapidly and techniques to keep the prediction time short and to use adequate models are essential. There are different methods for near-real-time clock estimation, delivering more or less middling results. Common for all methods are issues like time delays and data gaps, degrading the already weak network configuration. We analysed these issues and their influences on the near-real-time products, based on recorded real-time and other observation data modified to include gaps, jumps and other potential pitfalls. The poster will present an extract of our analyses, showing the impact of data gaps on selected sites, as well as the impact of different network configurations. One of our current research areas is the definition an implementation of a new method to derive the clocks and orbits by stacking normal equations in quasi-real-time (5 minute batches solutions). These method, and some preliminary results, will be presented. We expect this approach to offer accuracies comparable to the IGS non real-time products (in an ideal scenario with a good and reliable real-time network) but with a delay of minutes.

  12. Near-parabolic comets observed in 2006-2010. The individualized approach to 1/a-determination and the new distribution of original and future orbits

    NASA Astrophysics Data System (ADS)

    Królikowska, Ma?gorzata; Dybczy?ski, Piotr A.

    2013-10-01

    Dynamics of a complete sample of small perihelion distance near-parabolic comets discovered in the years 2006-2010 are studied (i.e. of 22 comets of qosc < 3.1 au). First, osculating orbits are obtained after a very careful positional data inspection and processing, including where appropriate, the method of data partitioning for determination of pre- and post-perihelion orbit for tracking then its dynamical evolution. The non-gravitational acceleration in the motion is detected for 50 per cent of investigated comets, in a few cases for the first time. Different sets of non-gravitational parameters are determined from pre- and post-perihelion data for some of them. The influence of the positional data structure on the possibility of the detection of non-gravitational effects and the overall precision of orbit determination is widely discussed. Secondly, both original and future orbits were derived by means of numerical integration of swarms of virtual comets obtained using a Monte Carlo cloning method. This method allows us to follow the uncertainties of orbital elements at each step of dynamical evolution. The complete statistics of original and future orbits that includes significantly different uncertainties of 1/a-values is presented, also in the light of our results obtained earlier. Basing on 108 comets examined by us so far, we conclude that only one of them, C/2007 W1 Boattini, seems to be a serious candidate for an interstellar comet. We also found that 53 per cent of 108 near-parabolic comets escaping in the future from the Solar system, and the number of comets leaving the Solar system as so called Oort spike comets (i.e. comets suffering very small planetary perturbations) is 14 per cent. A new method for cometary orbit quality assessment is also proposed by means of modifying the original method, introduced by Marsden, Sekanina & Everhart. This new method leads to a better diversification of orbit quality classes for contemporary comets.

  13. The NOVA-2 postlaunch orbit adjustment process

    NASA Astrophysics Data System (ADS)

    Heyler, Gene A.

    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.

  14. Identification of molecular determinants of primary and metastatic tumour re-initiation in breast cancer.

    PubMed

    Ross, Jason B; Huh, Doowon; Noble, Lisa B; Tavazoie, Sohail F

    2015-05-01

    Through in vivo selection of multiple ER-negative human breast cancer populations for enhanced tumour-forming capacity, we have derived subpopulations that generate tumours more efficiently than their parental populations at low cell numbers. Tumorigenic-enriched subpopulations exhibited increased expression of LAMA4, FOXQ1 and NAP1L3—genes that are also expressed at greater levels by independently derived metastatic subpopulations. These genes promote metastatic efficiency. FOXQ1 promotes LAMA4 expression, and LAMA4 enhances clonal expansion following substratum detachment in vitro, tumour re-initiation in multiple organs, and disseminated metastatic cell proliferation and colonization. The promotion of cancer cell proliferation and tumour re-initiation by LAMA4 requires ?1-integrin. Increased LAMA4 expression marks the transition of human pre-malignant breast lesions to malignant carcinomas, and tumoral LAMA4 overexpression predicts reduced relapse-free survival in ER-negative patients. Our findings reveal common features that govern primary and metastatic tumour re-initiation and identify a key molecular determinant of these processes. PMID:25866923

  15. Determination of burst initiation location and tear propagation velocity during air burst testing of latex condoms

    NASA Astrophysics Data System (ADS)

    Davidhazy, Andrew

    1991-04-01

    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.

  16. Detector positioning for the initial subcriticality level determination in accelerator-driven systems

    SciTech Connect

    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

    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)

  17. Kinematic and reduced-dynamic precise orbit determination of CHAMP satellite over one year using spaceborne GPS phase zero-differences only

    NASA Astrophysics Data System (ADS)

    Svehla, D.; Rothacher, M.

    2003-04-01

    Using zero-difference GPS carrier-phase measurements only, without any differencing in space or time domain, precise orbit determination (POD) of Low Earth Orbiters (LEO) can be performed. Among all space geodetic techniques (SLR, DORIS, VLBI, etc.) only GPS allows purely kinematic orbit determination where kinematic positions of the satellite are estimated independently of any force model or orbit altitude. Since the accuracy of the kinematic orbit determination depends only on the quality of the GPS measurements and the GPS orbit/clock accuracy, kinematic POD is an alternative to the classical dynamic or reduced-dynamic approach, where accuracy is limited by the quality of the dynamic models, e.g., gravity field, air-drag, solar radiation, etc. Highly accurate kinematic positions and kinematic velocities together with the variance-covariance information can be used as pseudo-observations in gravity field recovery and for the assessment of dynamical models in (reduced-)dynamic POD. Kinematic and reduced-dynamic orbits for CHAMP were determined over a time span of one year in order to compare the advantages and disadvantages of both approaches. It will be shown, that by using consistent GPS satellite orbits and clocks, highly accurate kinematic and reduced-dynamic LEO POD can be performed using zero-difference phase measurements only. Although kinematic and dynamic approaches are conceptually completely different, they show differences of only 1-2 cm (RMS) for the CHAMP satellite. Based on SLR observations the accuracy of the CHAMP kinematic and reduced-dynamic orbits are assessed over the analyzed period of one year. Using zero-difference kinematic POD it can be shown that the variance-covariance information represents very well the accuracy of kinematic positions. Accuracy assessment and limitations of spaceborne kinematic velocities and acceleration will be addressed as well. Comparing kinematic and reduced-dynamic LEO POD as well as residuals of SLR observations we obtain a nice playground to test various phenomena like multipath in the CHAMP code/phase measurements, CHAMP attitude, CHAMP GPS antenna phase center location -- results will be presented for a period of one year --, the polarization effect for a spaceborne CHAMP and a ground GPS antenna -- comparison with a fast rotating GPS antenna on the ground will be shown --, as well as the influence of special and general relativistic effects on the CHAMP kinematic/dynamic orbit results.

  18. Small Mercury Relativity Orbiter

    NASA Technical Reports Server (NTRS)

    Bender, Peter L.; Vincent, Mark A.

    1989-01-01

    The accuracy of solar system tests of gravitational theory could be very much improved by range and Doppler measurements to a Small Mercury Relativity Orbiter. A nearly circular orbit at roughly 2400 km altitude is assumed in order to minimize problems with orbit determination and thermal radiation from the surface. The spacecraft is spin-stabilized and has a 30 cm diameter de-spun antenna. With K-band and X-band ranging systems using a 50 MHz offset sidetone at K-band, a range accuracy of 3 cm appears to be realistically achievable. The estimated spacecraft mass is 50 kg. A consider-covariance analysis was performed to determine how well the Earth-Mercury distance as a function of time could be determined with such a Relativity Orbiter. The minimum data set is assumed to be 40 independent 8-hour arcs of tracking data at selected times during a two year period. The gravity field of Mercury up through degree and order 10 is solved for, along with the initial conditions for each arc and the Earth-Mercury distance at the center of each arc. The considered parameters include the gravity field parameters of degree 11 and 12 plus the tracking station coordinates, the tropospheric delay, and two parameters in a crude radiation pressure model. The conclusion is that the Earth-Mercury distance can be determined to 6 cm accuracy or better. From a modified worst-case analysis, this would lead to roughly 2 orders of magnitude improvement in the knowledge of the precession of perihelion, the relativistic time delay, and the possible change in the gravitational constant with time.

  19. Sociocultural Determinants of Tobacco Smoking Initiation among University Students in Bucaramanga, Colombia, 2012

    PubMed Central

    Afanador, Laura del Pilar Cadena; Radi, Daniel Sebastián Salazar; Pinto, Luis Enrique Vásquez; Pinzón, Cristian Eduardo Pérez; Carreño, Manuel Felipe Castro

    2014-01-01

    Background: Tobacco smoking is the leading cause of preventable mortality. The prevalence of smoking in adolescents in high schools ranges from 23.5% to 41%, respectively. In Colombia, these figures are similar and students entering the University are exposed to initiate smoking. The purpose of this study was to establish the determinants associated with the initiation of tobacco smoking among university students. Methods: A case–control paired by sex and age study design was used. The study population was the students of a private university of Bucaramanga, Santander, Colombia. The final sample consisted of 167 cases and 314 controls randomly select undergraduate university students. Data analysis was performed using a Logistic regression model adjusted by gender and age; using the initiation of tobacco smoking as the dependent variable, and as independent variables relationship with parents, history of parental smoking, university social environment, being away from hometown, steady girlfriend/boyfriend who smokes, alcohol consumption, physical activity, and Francis Score. Results: The social environment (odds ratio [OR]: 32.70, 7.40-144.55), being away from hometown (OR: 3.06, 1.55-6.07), history of steady girlfriend/boyfriend who smoke (OR: 2.87, 1.43-5.76), a bad relationship with the father (OR: 8.01, 2.01-31.83), history of tobacco consumption of the mother (OR: 2.66, 1.37-5.17) and alcohol consumption (OR: 4.79, 1.91-12.00) appeared as determinants of initiation of tobacco smoking. As protector factors we found media advertisement (OR: 0.19, 0.05-0.71), light physical activity 2-3 times a week (OR: 0.33, 0.12-0.88), and a high result in Francis score (OR: 0.95, 0.919-0.99). Conclusions: University efforts for tobacco-free policies should focus on preventive advertisement, promoting physical activity and awareness among young students of social environmental factors that could influence their decision to start smoking tobacco. PMID:25317292

  20. 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

    2011-10-01

    ...determination and changes as a result of a DRG validation. 476.94 Section 476.94 Public...determination and changes as a result of a DRG validation. (a) Notice of initial denial determination...retrospective review, (excluding DRG validation and post procedure review),...