For comprehensive and current results, perform a real-time search at Science.gov.

1

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

2

A practical algorithm is proposed for determining the orbit of a geostationary orbit (GEO) satellite using single-epoch measurements from a Global Positioning System (GPS) receiver under the sparse visibility of the GPS satellites. The algorithm uses three components of a state vector to determine the satellite's state, even when it is impossible to apply the classical single-point solutions (SPS). Through consideration of the characteristics of the GEO orbital elements and GPS measurements, the components of the state vector are reduced to three. However, the algorithm remains sufficiently accurate for a GEO satellite. The developed algorithm was tested on simulated measurements from two or three GPS satellites, and the calculated maximum position error was found to be less than approximately 40 km or even several kilometers within the geometric range, even when the classical SPS solution was unattainable. In addition, extended Kalman filter (EKF) tests of a GEO satellite with the estimated initial state were performed to validate the algorithm. In the EKF, a reliable dynamic model was adapted to reduce the probability of divergence that can be caused by large errors in the initial state. PMID:25835299

Kim, Ghangho; Kim, Chongwon; Kee, Changdon

2015-01-01

3

Initial results of precise orbit and clock determination for COMPASS navigation satellite system

NASA Astrophysics Data System (ADS)

The development of the COMPASS satellite system is introduced, and the regional tracking network and data availability are described. The precise orbit determination strategy of COMPASS satellites is presented. Data of June 2012 are processed. The obtained orbits are evaluated by analysis of post-fit residuals, orbit overlap comparison and SLR (satellite laser ranging) validation. The RMS (root mean square) values of post-fit residuals for one month's data are smaller than 2.0 cm for ionosphere-free phase measurements and 2.6 m for ionosphere-free code observations. The 48-h orbit overlap comparison shows that the RMS values of differences in the radial component are much smaller than 10 cm and those of the cross-track component are smaller than 20 cm. The SLR validation shows that the overall RMS of observed minus computed residuals is 68.5 cm for G01 and 10.8 cm for I03. The static and kinematic PPP solutions are produced to further evaluate the accuracy of COMPASS orbit and clock products. The static daily COMPASS PPP solutions achieve an accuracy of better than 1 cm in horizontal and 3 cm in vertical. The accuracy of the COMPASS kinematic PPP solutions is within 1-2 cm in the horizontal and 4-7 cm in the vertical. In addition, we find that the COMPASS kinematic solutions are generally better than the GPS ones for the selected location. Furthermore, the COMPASS/GPS combinations significantly improve the accuracy of GPS only PPP solutions. The RMS values are basically smaller than 1 cm in the horizontal components and 3-4 cm in the vertical component.

Zhao, Qile; Guo, Jing; Li, Min; Qu, Lizhong; Hu, Zhigang; Shi, Chuang; Liu, Jingnan

2013-05-01

4

A Comprehensive Comparison Between Angles-Only Initial Orbit Determination Techniques

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

Schaeperkoetter, Andrew Vernon

2012-02-14

5

Adaptive interplanetary orbit determination

NASA Astrophysics Data System (ADS)

This work documents the development of a real-time interplanetary orbit determination monitoring algorithm for detecting and identifying changes in the spacecraft dynamic and measurement environments. The algorithm may either be utilized in a stand-alone fashion as a spacecraft monitor and hypothesis tester by navigators or may serve as a component in an autonomous adaptive orbit determination architecture. In either application, the monitoring algorithm serves to identify the orbit determination filter parameters to be modified by an offline process to restore the operational model accuracy when the spacecraft environment changes unexpectedly. The monitoring algorithm utilizes a hierarchical mixture-of-experts to regulate a multilevel bank organization of extended Kalman filters. Banks of filters operate on the hierarchy top-level and are composed of filters with configurations representative of a specific environment change called a macromode. Fine differences, or micromodes, within the macromodes are represented by individual filter configurations. Regulation is provided by two levels of single-layer neural networks called gating networks. A single top-level gating network regulates the weighting among macromodes and each bank uses a gating network to regulate member filters internally. Experiments are conducted on the Mars Pathfinder cruise trajectory environment using range and Doppler data from the Deep Space Network. The experiments investigate the ability of the hierarchical mixture-of-experts to identify three environment macromodes: (1) unmodeled impulsive maneuvers, (2) changes in the solar radiation pressure dynamics, and (3) changes in the measurement noise strength. Two methods of initializing the gating networks are examined in each experiment. One method gives the neurons associated with all filters equivalent synaptic weight. The other method places greater weight on the operational filter initially believed to model the spacecraft environment. The results will show that the equal synaptic weight initialization method is superior to the one favoring the operational filter and that processing range and Doppler data together is superior to processing Doppler data alone. When processing range and Doppler with an equally initialized hierarchy, all three macromodes are definitively identified by the top-level gating network weights. Additionally, in the case of multiple successive macromode changes, the hierarchy is generally able to recover from one macromode and identify a change to another macromode.

Crain, Timothy Price

6

NASA Astrophysics Data System (ADS)

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

Shefer, V. A.

2010-12-01

7

Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis

NASA Technical Reports Server (NTRS)

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

Slojkowski, Steven E.

2014-01-01

8

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

9

Lunar Prospector Orbit Determination Results

NASA Technical Reports Server (NTRS)

The orbit support for Lunar Prospector (LP) consists of three main areas: (1) cislunar orbit determination, (2) rapid maneuver assessment using Doppler residuals, and (3) routine mapping orbit determination. The cislunar phase consisted of two trajectory correction maneuvers during the translunar cruise followed by three lunar orbit insertion burns. This paper will detail the cislunar orbit determination accuracy and the real-time assessment of the cislunar trajectory correction and lunar orbit insertion maneuvers. The non-spherical gravity model of the Moon is the primary influence on the mapping orbit determination accuracy. During the first two months of the mission, the GLGM-2 lunar potential model was used. After one month in the mapping orbit, a new potential model was developed that incorporated LP Doppler data. This paper will compare and contrast the mapping orbit determination accuracy using these two models. LP orbit support also includes a new enhancement - a web page to disseminate all definitive and predictive trajectory and mission planning information. The web site provides definitive mapping orbit ephemerides including moon latitude and longitude, and four week predictive products including: ephemeris, moon latitude/longitude, earth shadow, moon shadow, and ground station view periods. This paper will discuss the specifics of this web site.

Beckman, Mark; Concha, Marco

1998-01-01

10

Orbit Determination of the Lunar Reconnaissance Orbiter

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

11

Orbit Determination Issues for Libration Point Orbits

NASA Technical Reports Server (NTRS)

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

Beckman, Mark; Bauer, Frank (Technical Monitor)

2002-01-01

12

Precise orbit determination for GRACE

NASA Astrophysics Data System (ADS)

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.

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

2003-04-01

13

Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis

NASA Technical Reports Server (NTRS)

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

Slojkowski, Steven E.

2014-01-01

14

Thirteenth satellite of Jupiter. [orbit determination

NASA Technical Reports Server (NTRS)

The discovery, observations, and attempts to determine the orbit of Jupiter XIII are described. It is found that the orbit is very similar to the orbits of Jupiter VI, VII, and X. An ephemeris is provided for the 1975 opposition.

Kowal, C. T.; Aksnes, K.; Marsden, B. G.; Roemer, E.

1975-01-01

15

Single Frequency GPS Orbit Determination for Low Earth Orbiters

NASA Technical Reports Server (NTRS)

A number of missions in the future are planning to use GPS for precision orbit determination. Cost considerations and receiver availability make single frequency GPS receivers attractive if the orbit accuracy requirements can be met.

Bertiger, Willy; Wu, Sien-Chong

1996-01-01

16

Low thrust orbit determination program

NASA Technical Reports Server (NTRS)

Logical flow and guidelines are provided for the construction of a low thrust orbit determination computer program. The program, tentatively called FRACAS (filter response analysis for continuously accelerating spacecraft), is capable of generating a reference low thrust trajectory, performing a linear covariance analysis of guidance and navigation processes, and analyzing trajectory nonlinearities in Monte Carlo fashion. The choice of trajectory, guidance and navigation models has been made after extensive literature surveys and investigation of previous software. A key part of program design relied upon experience gained in developing and using Martin Marietta Aerospace programs: TOPSEP (Targeting/Optimization for Solar Electric Propulsion), GODSEP (Guidance and Orbit Determination for SEP) and SIMSEP (Simulation of SEP).

Hong, P. E.; Shults, G. L.; Huling, K. R.; Ratliff, C. W.

1972-01-01

17

Circular orbits and spin in black-hole initial data

The construction of initial data for black-hole binaries usually involves the choice of free parameters that define the spins of the black holes and essentially the eccentricity of the orbit. Such parameters must be chosen carefully to yield initial data with the desired physical properties. In this paper, we examine these choices in detail for the quasiequilibrium method coupled to apparent-horizon/quasiequilibrium boundary conditions. First, we compare two independent criteria for choosing the orbital frequency, the "Komar-mass condition" and the "effective-potential method," and find excellent agreement. Second, we implement quasi-local measures of the spin of the individual holes, calibrate these with corotating binaries, and revisit the construction of non-spinning black hole binaries. Higher-order effects, beyond those considered in earlier work, turn out to be important. Without those, supposedly non-spinning black holes have appreciable quasi-local spin; furthermore, the Komar-mass condition and effective potential method agree only when these higher-order effects are taken into account. We compute a new sequence of quasi-circular orbits for non-spinning black-hole binaries, and determine the innermost stable circular orbit of this sequence.

Matthew Caudill; Gregory B. Cook; Jason D. Grigsby; Harald P. Pfeiffer

2006-09-01

18

Simulation of precise orbit determination of lunar orbiters

NASA Astrophysics Data System (ADS)

Based on the ongoing Chinese lunar exploration mission, i.e. the "Chang'e 1" project, precise orbit determination of lunar orbiters is analyzed for the actual geographical distribution and observational accuracy of the Chinese united S-band (USB) observation and control network as well as the very long baseline interferometry (VLBI) tracking network. The observed data are first simulated, then solutions are found after including the effects of various error sources and finally compared. We use the space data analysis software package, GEODYN, developed at Goddard Space Flight Center, NASA, USA. The primary error source of the flight orbiting the moon is the lunar gravity field. Therefore, the (formal) error of JGL165P1, i.e. the model of the lunar gravity field with the highest accuracy at present, is first discussed. After simulating the data of ranging and velocity measurement as well as the VLBI data of the time delay and time delay rate, precise orbit determination is carried out when the error of the lunar gravity field is added in. When the orbit is determined, the method of reduced dynamics is adopted with the selection of appropriate empirical acceleration parameters to absorb the effect of errors in the lunar gravity field on the orbit determination. The results show that for lunar missions like the "Chang'e 1" project, that do not take the lunar gravity field as their main scientific objective, the method of reduced dynamics is a simple and effective means of improving the accuracy of the orbit determination of the lunar orbiters.

Hu, Xiao-gong; Huang, Cheng; Huang, Yong

2005-10-01

19

Simulation of precise orbit determination of lunar orbiters

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

Xiao-Gong Hu; Cheng Huang; Yong Huang

2005-01-01

20

Determination of GPS orbits to submeter accuracy

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

21

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

22

Orbit determination using synthetic aperture radar

NASA Technical Reports Server (NTRS)

The use of synthetic aperture radar (SAR) images to estimate orbital parameters is studied. The SAR image formation process which requires the ability to repeatedly transmit identical signals and accurately sense the return echoes from a region of terrain is described. The orbit determination capabilities of the SAR system's observables are investigated. Five SAR observations were collected from a simulated shuttle orbit, which was circular with a latitude of 220 km and along-track velocity of 7.7 km/sec, to obtain along-track and line-of-sight direction position measurements; the simulation reveals that only three SAR observations were required to determine the position of the spacecraft to within 100 m. A prototype SAR orbit determination system was developed. The system consists of a VAX 11/780 time-shared computer, a frame buffer, topographic maps, and software for line-pixel location of an object within a SAR image and for orbit determination. The prototype is applied to the processing of a single short arc of Shuttle Imaging-Radar-B (SIR-B) data. It is observed that the SAR data is useful as orbit determination or tracking data; however, the low SNRs in the SIR-B data made feature identification difficult.

Taber, W. L.; Synnott, S. P.; Riedel, J. E.

1986-01-01

23

NASA Technical Reports Server (NTRS)

The Chandra X-ray Observatory (CXO, formerly AXAF) is the third of the four NASA great observatories. It was launched from Kennedy Space Flight Center on 23 July 1999 aboard the Space Shuttle Columbia and was successfully inserted in a 330 x 72,000 km orbit by the Inertial Upper Stage (IUS). Through a series of five Integral Propulsion System burns, CXO was placed in a 10,000 x 139,000 km orbit. After initial on-orbit checkout, Chandra's first light images were unveiled to the public on 26 August, 1999. The CXO Pointing Control and Aspect Determination (PCAD) subsystem is designed to perform attitude control and determination functions in support of transfer orbit operations and on-orbit science mission. After a brief description of the PCAD subsystem, the paper highlights the PCAD activities during the transfer orbit and initial on-orbit operations. These activities include: CXO/IUS separation, attitude and gyro bias estimation with earth sensor and sun sensor, attitude control and disturbance torque estimation for delta-v burns, momentum build-up due to gravity gradient and solar pressure, momentum unloading with thrusters, attitude initialization with star measurements, gyro alignment calibration, maneuvering and transition to normal pointing, and PCAD pointing and stability performance.

Quast, Peter; Tung, Frank; West, Mark; Wider, John

2000-01-01

24

The GEOS-3 orbit determination investigation

NASA Technical Reports Server (NTRS)

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.

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

1978-01-01

25

Lunar Prospector mapping-phase orbit determination

NASA Astrophysics Data System (ADS)

This paper details the model method and results for lunar satellite orbit determination OD with the newly developed OD software PASAX Lunar Prospector LP one-week S-band two-way doppler and range observations during the norminal mission will be used for the OD Prior to the OD LP orbital variation during this week will be analysed During the OD the accuracy for the OD and the orbit prediction will be investigated in great details Orbit determination comparison with different gravity field different planetary ephemeredes and different strategies will be examined The OD results on two extreme geometries i e when the orbit plane is perpendicular or parallel to the Earth-Moon line will be discussed Comparing the orbit on the overlap period indicates that the OD accuracy is on meters level The range rate O-C residual is about 0 5mm s close to the actual measurement noise The position difference of orbit solutions produced by PASAX and GEODYN softwares is within 2m 1-Sigma

Wang, J. S.; Chen, J. R.; Ma, P. B.; Wang, Y. R.; Li, J. S.; Chen, C. G.; Jiang, J. C.

26

Lunar Prospector mapping-phase orbit determination

This paper details the model method and results for lunar satellite orbit determination OD with the newly developed OD software PASAX Lunar Prospector LP one-week S-band two-way doppler and range observations during the norminal mission will be used for the OD Prior to the OD LP orbital variation during this week will be analysed During the OD the accuracy for

J. S. Wang; J. R. Chen; P. B. Ma; Y. R. Wang; J. S. Li; C. G. Chen; J. C. Jiang

2006-01-01

27

Galileo Orbit Determination for the Ida Encounter

This paper summarizes orbit determination activities leading Up its encounter with asteroid 243-Ida on August 28, 1993. In addition to the nominal 2-way S-band range and Doppler radio metric data obtained from the Deep Space Network several navigational aids were brought together make this encounter successful. These include a comprehensive ground-based observation campaign of the asteroid during rhe four years prior to the flyby to improve Ida's ephemeris significantly, and the Optical Navigation picture campaign which helped decrease considerably the uncertainties of Galileo's position relative to Ida. Details in the modeling of Galileo's orbit and in the navigational tools described above will be explained, and the results of several key orbit solutions will be given. the encounter, reconstructions of Galileo's orbit with respect to Ida were performed using several SS1 science images of the asteroid that were returned to Earth from September 1993 through late April 1994. The final d...

Nicho Ls On' P. G. Antreasian; F. T. Nicholson; P. H. Kdlemeyn; S. Bhiiskaran; R. J. Hawl; P. Htdamek

28

Algorithms for Autonomous GS Orbit Determination and Formation Flying

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

29

Precision orbit determination software validation experiment

This paper presents the results of an experiment which was designed to ascertain the level of agreement between GEODYN and UTOPIA, two completely independent computer programs used for precision orbit determination, and to identify the sources which limit the agreement. For a limited set of models and a seven-day data set arc length, the altitude components of the ephemeris obtained

B. E. Schutz; B. D. Tapley; R. J. Eanes; J. G. Marsh; R. G. Williamson; T. V. Martin

1980-01-01

30

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

31

Tethered body problems and relative motion orbit determination

NASA Technical Reports Server (NTRS)

Selected problems dealing with orbiting tethered body systems have been studied. In addition, a relative motion orbit determination program was developed. Results from these tasks are described and discussed. The expected tethered body motions were examined, analytically, to ascertain what influence would be played by the physical parameters of the tether, the gravity gradient and orbit eccentricity. After separating the motion modes these influences were determined; and, subsequently, the effects of oscillations and/or rotations, on tether force, were described. A study was undertaken, by examining tether motions, to see what type of control actions would be needed to accurately place a mass particle at a prescribed position relative to a main vehicle. Other applications for tethers were studied. Principally these were concerned with the producing of low-level gee forces by means of stabilized tether configurations; and, the initiation of free transfer trajectories from tether supported vehicle relative positions.

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

1972-01-01

32

Precision orbit determination software validation experiment

NASA Technical Reports Server (NTRS)

This paper presents the results of an experiment which was designed to ascertain the level of agreement between GEODYN and UTOPIA, two completely independent computer programs used for precision orbit determination, and to identify the sources which limit the agreement. For a limited set of models and a seven-day data set arc length, the altitude components of the ephemeris obtained by the two programs agree at the sub-centimeter level throughout the arc.

Schutz, B. E.; Tapley, B. D.; Eanes, R. J.; Marsh, J. G.; Williamson, R. G.; Martin, T. V.

1980-01-01

33

Orbit determination via adaptive Gaussian swarm optimization

NASA Astrophysics Data System (ADS)

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

Kiani, Maryam; Pourtakdoust, Seid H.

2015-02-01

34

Information measures for statistical orbit determination

NASA Astrophysics Data System (ADS)

The current Situational Space Awareness (SSA) is faced with a huge task of tracking the increasing number of space objects. The tracking of space objects requires frequent and accurate monitoring for orbit maintenance and collision avoidance using methods for statistical orbit determination. Statistical orbit determination enables us to obtain estimates of the state and the statistical information of its region of uncertainty given by the probability density function (PDF). As even collision events with very low probability are important, accurate prediction of collisions require the representation of the full 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. In order to obtain an accurate representation of the PDF that incorporates higher order statistical information, we propose the use of nonlinear estimation methods such as the Particle Filter. 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. Moreover, during longer state propagations, we propose to represent the final state vector as a compressed probability mass function (PMF). Multivariate PDF compressions are computationally costly and could potentially be numerically intractable. We tackle this issue by decorrelating the nonlinear multivariate state PMFs using an improved nonlinear factor analysis (NFA) that uses a multilayer perceptron (MLP) network to model the state nonlinearities and obtain the sources that also incorporates the Fast Independent Component Analysis (FastICA [a faster computational method for ICA]) to obtain the independent and decorrelated states. Methods such as the Principal Component Analysis (PCA) are based on utilizing moments that only incorporate the second order statistics, hence will not suffice in maintaining maximum information content. On the other hand, the Independent Component Analysis (ICA) is a non-Gaussian decorrelator that is based on a linear mapping scheme, that does not incorporate the non-linear information. The PDF compressions are achieved by implementing the fast-Fourier Transform (FFT) and the wavelet transform (WT) to construct a smaller subset of data for data allocation and transmission cost reduction. The accuracy of tracking the space objects as well as reduced costs will help increase the capability of tracking the increased number of space objects. We use statistical information measures such as the Kolmogorov-Smirnov (K-S) test and the Kullback-Leibler Divergence (KLD) metric to quantify the accuracy of the reconstructed state vector and the cost reduction is measured by the number of terms required to represent the states. A performance plot illuminates the performances of the transforms over a range of compression rates. Simulations are performed on real and simulated data to demonstrate the approach for this work.

Mashiku, Alinda K.

35

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

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

36

NASA Astrophysics Data System (ADS)

This contribution deals with Precise Orbit Determination of the Lunar Reconnaissance Orbiter, which is tracked with optical laser ranges in addition to radiometric Doppler range-rates and range observations. The optimum parameterization is assessed by overlap analysis tests that indicate the inner precision of the computed orbits. Information about the very long wavelengths of the lunar gravity field is inferred from the spacecraft positions. The NASA software packages GEODYN II and SOLVE were used for orbit determination and gravity field recovery [1].

Maier, A.; Baur, O.; Krauss, S.

2014-04-01

37

OrbView-3 Initial On-Orbit Characterization

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

38

Sequential Orbit Determination with the Cubed-Sphere Gravity Model

transformation scale factor = generic parameter = offset scale factor used in the unscented transformation provides rapid evaluation of the gravity field for more efficient orbit propagation. This paper characterizes the improved computational efficiency of sequential orbit determination, specifically the extended

Born, George

39

Toward decimeter Topex orbit determination using GPS

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

40

Reduced-Dynamic Technique For Determination Of Orbits

NASA Technical Reports Server (NTRS)

Orbits determined more accurately than in dynamic or geometric method. Report discusses reduced-dynamic technique for use of signals from satellites in Global Positioning System (GPS) to determine orbit of satellite in low orbit around Earth. Formed from combination of dynamic and geometric (nondynamic) tracking techniques, and combines advantages of both to increase accuracy of estimated orbit under conditions in which neither clearly superior.

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

1989-01-01

41

Orbit Determination of Space Debris: Correlation of Optical Observations

NASA Astrophysics Data System (ADS)

When a piece of space debris is observed by optical telescopes, angular and angular-rate information can be precisely estimated from the track using basic kinematics. However range and range-rate information is to a large extent undetermined, other than by a few weak physical constraints. The standard approach in performing an orbit determination between two separate tracks of data is the least squares approach. This approach, however, presupposes a nominal estimation of the true orbit that is later corrected by the least squares algorithm. Since such an initial estimate is not known a priori for a single pass, this approach is ill-suited to deal with the increase in uncorrelated tracks expected as new telescopes come online within the next few years. The approach we describe here takes a more global perspective. After computing the admissible region, the set of all points possible belonging to a given track, for each of the two tracks, we then dynamically evolve or regress these two-dimensional regions into a common coordinate system and finally search for possible intersections. By utilizing this process, large reductions can be made to the uncertainty in the topocentric range, range-rate space. Once candidate solutions are found a standard least squares approximation can refine the initial orbit produced by our method. This paper discusses some of the complications and advantages associated with performing these intersections.

Maruskin, J.; Scheeres, D.; Alfriend, K.

42

WINCS/SWATS Initial On-Orbit Performance Results

NASA Astrophysics Data System (ADS)

The Winds-Ions-Neutral Composition Suite (WINCS) instrument, also know as the Small Wind and Temperature Spectrometer (SWATS), was designed and developed jointly by the Naval Research Laboratory (NRL) and NASA/Goddard Space Flight Center (GSFC) for ionosphere-thermosphere investigations in orbit between 120 and 550 km altitude. The WINCS design provides the following measurements in a single package with a low Size, Weight, and Power (SWaP): 7.6 x 7.6 x 7.1 cm outer dimensions, 0.75 kg total mass, and about 1.3 Watt total power: neutral winds, neutral temperature, neutral density, neutral composition, ion drifts, ion temperature, ion density and ion composition. Initial on-orbit results of the first flight of the instrument will be presented. The flight, scheduled for Aug 2013, is on the International Space Station as STP-H4 the instrument complement and will be in a 51.6° inclination circular orbit at 400 km altitude. The instrument will also be on the Space Environment Nano-Satellite Experiment (SENSE) and the STPSat-3 satellites, both expected to launch in the fall of 2013.

Nicholas, A. C.; Stephan, A. W.; Finne, T. T.; Herrero, F.

2013-12-01

43

GPS as an orbit determination subsystems

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

44

Testing A GPS Technique For Precise Low Earth Orbit Determination

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

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

2002-01-01

45

Satellite orbit determination and power subsystem design

One of the most important problems in mission planning and satellite command and control is being able to accurately predict orbital motion, because the trajectory of a spacecraft is a fundamental design parameter with major implications for all subsystems. The purpose of this paper is to present, first, the simulation of the satellite orbit analysis based on data collected from

S. Chouraqui; M. Bekhti; C. I. Underwood

2003-01-01

46

MicroGPS for Low-Cost Orbit Determination

NASA Astrophysics Data System (ADS)

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 microGPS 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 microGPS receiver will be snapshots of carrier Doppler and ambiguous pseudorange. Among the challenges in orbit determination are the resolution of the pseudorange ambiguity; the estimation of the measurement time tag drift, which effects the in-track orbit position solution; and the convergence of the orbit solution from a cold start with essentially no knowledge of the orbit. The effects of data gaps and Doppler data quality are investigated. An efficient data acquisition scenario for SNOE is derived.

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

1997-07-01

47

Orbit determination and prediction study for Dynamic Explorer 2

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

48

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

49

On the Determination of the Orbits of Comets

NASA Astrophysics Data System (ADS)

Preface; 1. General view of the method; 2. On the motion of the point of intersection of the radius vector and cord; 3. On the comparison of the parabolic cord with the space which answers to the mean velocity of the earth in the same time; 4. Of the reduction of the second longitude of the comet; 5. On the proportion of the three curtate distances of the comet from the earth; 6. Of the graphical declination of the orbit of the earth; 7. Of the numerical quantities to be prepared for the construction or computation of the comet's orbit; 8. Determination of the distances of the comet from the earth and the sun; 9. Determination of the elements of the orbit from the determined distances; 10. Determination of the place of the comet from the earth and sun; 11. Determination of the distances of the comet from the earth and sun; 12. Determination of the comet's orbit; 13. Determination of the place of the comet; 14. Application of the graphical method to the comet of 1769; 15. Application of the distances found; 16. Determination of the place of the comet, for another given time; 17. Application of the trigonometrical method to the comet of 1769; 18. Determination of the elements of the orbit of the comet of 1769; Example of the graphical operation for the orbit of the comet of 1769; Example of the trigonometrical operation for the orbit of the comet of 1769; Conclusion; La Place's general method for determining the orbits of comets; Determination of the two elements of the orbit; Application of La Place's method of finding the approximate perihelion distance; Application of La Place's method for correcting the orbit of a comet, to the comet of 1769; Explanation and use of the tables; Tables; Appendix; Plates.

Englefield, Henry

2013-06-01

50

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

NASA Technical Reports Server (NTRS)

While navigation systems for the determination of the orbit of the Global Position System (GPS) have proven to be very effective, the current 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.

Welch, Bryan W.

2007-01-01

51

Semi-Major Axis Knowledge and GPS Orbit Determination

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

52

Semi-Major Axis Knowledge and GPS Orbit Determination

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

53

TOPEX/Poseidon precision orbit determination production and expert system

NASA Technical Reports Server (NTRS)

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

Putney, Barbara; Zelensky, Nikita; Klosko, Steven

1993-01-01

54

Astrodynamics. Volume 1 - Orbit determination, space navigation, celestial mechanics.

NASA Technical Reports Server (NTRS)

Essential navigational, physical, and mathematical problems of space exploration are covered. The introductory chapters dealing with conic sections, orientation, and the integration of the two-body problem are followed by an introduction to orbit determination and design. Systems of units and constants, as well as ephemerides, representations, reference systems, and data are then dealt with. A detailed attention is given to rendezvous problems and to differential processes in observational orbit correction, and in rendezvous or guidance correction. Finally, the Laplacian methods for determining preliminary orbits, and the orbit methods of Lagrange, Gauss, and Gibbs are reviewed.

Herrick, S.

1971-01-01

55

Initial observations from the Lunar Orbiter Laser Altimeter (LOLA)

As of June 19, 2010, the Lunar Orbiter Laser Altimeter, an instrument on the Lunar Reconnaissance Orbiter, has collected over 2.0 × 109 measurements of elevation that collectively represent the highest resolution global ...

Smith, David Edmund

56

The Importance of Semi-Major Axis Knowledge in the Determination of Near-Circular Orbits

NASA Technical Reports Server (NTRS)

Modem orbit determination has mostly been accomplished using Cartesian coordinates. This usage has carried over in recent years to the use of GPS for satellite orbit determination. The unprecedented positioning accuracy of GPS has tended to focus attention more on the system's capability to locate the spacecraft's location at a particular epoch than on its accuracy in determination of the orbit, per se. As is well-known, the latter depends on a coordinated knowledge of position, velocity, and the correlation between their errors. Failure to determine a properly coordinated position/velocity state vector at a given epoch can lead to an epoch state that does not propagate well, and/or may not be usable for the execution of orbit adjustment maneuvers. For the quite common case of near-circular orbits, the degree to which position and velocity estimates are properly coordinated is largely captured by the error in semi-major axis (SMA) they jointly produce. Figure 1 depicts the relationships among radius error, speed error, and their correlation which exist for a typical low altitude Earth orbit. Two familiar consequences are the relationship Figure 1 shows are the following: (1) downrange position error grows at the per orbit rate of 3(pi) times the SMA error; (2) a velocity change imparted to the orbit will have an error of (pi) divided by the orbit period times the SMA error. A less familiar consequence occurs in the problem of initializing the covariance matrix for a sequential orbit determination filter. An initial covariance consistent with orbital dynamics should be used if the covariance is to propagate well. Properly accounting for the SMA error of the initial state in the construction of the initial covariance accomplishes half of this objective, by specifying the partition of the covariance corresponding to down-track position and radial velocity errors. The remainder of the in-plane covariance partition may be specified in terms of the flight path angle error of the initial state. Figure 2 illustrates the effect of properly and not properly initializing a covariance. This figure was produced by propagating the covariance shown on the plot, without process noise, in a circular low Earth orbit whose period is 5828.5 seconds. The upper subplot, in which the proper relationships among position, velocity, and their correlation has been used, shows overall error growth, in terms of the standard deviations of the inertial position coordinates, of about half of the lower subplot, whose initial covariance was based on other considerations.

Carpenter, J. Russell; Schiesser, Emil R.

1998-01-01

57

NASA Astrophysics Data System (ADS)

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

Gan, Q. B.

2012-07-01

58

Ground-based phased array radar observations of Low Earth Orbit objects are addressed in this paper. Radar resources and radar data processing techniques are analysed with the aim of assessing the overall accuracy in orbit determination and propagation as a function of radar design trade-off parameters. The presented analysis is based on end-to-end simulation of both radar and orbital data processing

Massimo Sciotti; Piermario Besso; Tim Flohrer; Holger Krag

2011-01-01

59

Method of resolving radio phase ambiguity in satellite orbit determination

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

60

GPS-based precision orbit determination - A Topex flight experiment

NASA Technical Reports Server (NTRS)

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, design, flight receiver, antenna system, ground processing, and data processing of GPS are examined. Also, an accurate quasi-geometric orbit determination approach called nondynamic or reduced dynamic tracking which relies on the use of the pseudorange and the carrier phase measurements to reduce orbit errors arising from mismodeled dynamics is discussed.

Melbourne, William G.; Davis, Edgar S.

1988-01-01

61

NASA Astrophysics Data System (ADS)

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

Löcher, Anno; Kusche, Jürgen

2014-05-01

62

Precision orbit determination at the NASA Goddard Space Flight Center

NASA Technical Reports Server (NTRS)

This paper describes the GEODYN computer program developed by the Geodynamics Branch at the NASA Goddard Space Flight Center and outlines the procedure for accurate satellite orbit and tracking-data analyses. The capabilities of the program allow the development of gravity fields as large as 90 by 90, and a complete modeling of tidal parameters. It is also feasible to numerically integrate a continuous orbit of a satellite such as Lageos for up to 12 years. The evolution of the orbit can be studied, and, by comparison with locally determined orbits, force model improvements can be made. The GEODYN flow diagrams are presented.

Putney, B.; Kolenkiewicz, R.; Smith, D.; Dunn, P.; Torrence, M. H.

1990-01-01

63

32 CFR 300.8 - Initial determinations.

Code of Federal Regulations, 2014 CFR

...of Defense (Continued) OFFICE OF THE SECRETARY OF DEFENSE (CONTINUED) FREEDOM OF INFORMATION ACT PROGRAM DEFENSE LOGISTICS AGENCY FREEDOM OF INFORMATION ACT PROGRAM FOIA Request Processing § 300.8 Initial determinations....

2014-07-01

64

32 CFR 1907.24. - Initial determination.

Code of Federal Regulations, 2013 CFR

...ORDER 13526 Action on Challenges § 1907.24. Initial determination. (a) Formal challenges shall be directed to the CIA Information and Privacy Coordinator (Coordinator) who shall promptly forward the challenge to the C/CMCG for action....

2013-07-01

65

32 CFR 1907.24. - Initial determination.

Code of Federal Regulations, 2012 CFR

...ORDER 13526 Action on Challenges § 1907.24. Initial determination. (a) Formal challenges shall be directed to the CIA Information and Privacy Coordinator (Coordinator) who shall promptly forward the challenge to the C/CMCG for action....

2012-07-01

66

32 CFR 1907.24. - Initial determination.

Code of Federal Regulations, 2014 CFR

...ORDER 13526 Action on Challenges § 1907.24. Initial determination. (a) Formal challenges shall be directed to the CIA Information and Privacy Coordinator (Coordinator) who shall promptly forward the challenge to the C/CMCG for action....

2014-07-01

67

Autonomous Orbit Determination between a Lunar Satellite and a Distant Retrograde Orbit Probe

NASA Astrophysics Data System (ADS)

Currently, orbit determination of lunar satellites heavily rely on ground stations on the Earth. The observation data suffers from problems such as low accuracy and bad visibility. An efficient way to release the burden of the ground stations and to enhance the observation accuracy is to use the inter-satellite range data between two lunar satellites. However, a well-known problem of only using this type of data is the overall rotation of the orbital plane (undetermined orbit inclination, ascending nod and perigee). Some external reference sources should be introduced into the system to avoid the overall rotation. Recently, an interesting idea is to use a probe around the Earth-Moon CLP (collinear libration point) as the reference source. The orbit of the CLP probe is unknown a priori. It is determined simultaneously with the lunar satellite’s orbit by using the inter-satellite range data between them. There are many advantages of this idea, but also some problems. One main problem is caused by the strong instability of the motions around the CLPs. Probes usually need a frequent orbit control, but the accuracy of the orbit determination of the CLP probes from a short arc between two maneuvers is usually unsatisfied. In this contribution, another kind of special probe other than the CLP probe is considered. It lies on a DRO (distant retrograde orbit) around the Moon. The DROs usually have much better stability property than the CLP orbits, so DRO probes don’t need a frequent orbit control. At the same time, our studies show that the OD accuracy is comparable to that of the CLP probe. The work is firstly done in the CRTBP (circular restricted three-body problem) model, by studying the OD results of different amplitude (both in plane and out of plane) for the DROs. Then, the study is generated to the real force model of the Earth-Moon system.

Hou, Xiyun; Tang, Jingshi; Liu, Lin; Liu, Peng

68

GEODYN Orbit Determination of Dawn at Vesta using Image Constraints

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

69

Space Capsule Recovery Orbit Determination System and Performance

NASA Astrophysics Data System (ADS)

Space Capsule Recovery (SRE), a small satellite, completely recoverable capsule was launched by the Polar Satellite Launch Vehicle (PSLV-C7) from the Indian spaceport Sriharikota on 10th January 2007 at 04:09UT along with Indian Remore Sensing Satellite CARTOSAT-2 and two micro satellites namely Nano- Peheunsat and Lapantubsat. The satellite was put into an almost nominal orbit of (630 X 638)km with an inclination of 97.94deg. The main objective of the SRE missions was to conduct microgravity experiment, de- orbit and recover it in Indian waters. The spacecraft was de-boosted after the payload operations in the micro- gravity environment. This was achieved in two steps. SRE was first placed from the injected circular orbit to Repetitive Elliptical Orbit (REO) and subsequently de- boosted for reentry and recovery. This paper describes the S-band based orbit determination system for SRE and its performance during different phases of the mission. Comparison of the inertial navigation system (INS) and nominal orbit with the achieved/estimated orbit was made. Orbit determination system was executed successfully through out the mission. Relatively large residues were observed in measurements during OD process due to continuous thruster activity through out the mission.

Vighnesam, N. V.; Sonney, A.; Soni, P. K.

2008-08-01

70

Precision orbit determination using TOPEX/Poseidon TDRSS observations

NASA Technical Reports Server (NTRS)

The TOPEX/Poseidon (T/P) Mission carries a variety of packages to support experimental, precision and operational orbit determination. Included are a GPS transponder, laser retro-reflectors, the French-developed Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) Doppler tracking system and a Tracking Data Relay Satellite System (TDRSS) transponder. Presently, TDRSS tracking is used for operational orbit support and is processed with force and measurement modeling consistent with this purpose. However, the low noise and extensive geographical coverage of the TDRSS/TOPEX data allows an assessment of TDRSS Precision Orbit Determination (POD) capabilities by comparison to the T/P precision orbit determination. The Geodynamics (GEODYN) Orbit Determination System is used to process laser and DORIS data to produce the precision orbits for the T/P Project. GEODYN has been modified recently to support the TDRSS observations. TDRSS data analysis can now benefit from the extensive force modeling and reference frame stability needed to meet the orbit determination (OD) goals of the T/P Mission. This analysis has concentrated on the strongest of the TDRSS measurement types, its two-way average range rate. Both the TDRSS and T/P orbits have been assessed in combination with the global satellite laser ranging (SLR) data and by themselves. These results indicate that significant improvement in the TDRSS ephemerides is obtained when the T/P orbit is well determined by SLR, and the TDRSS/TOPEX Doppler link is used to position TDRSS. Meter-level TDRSS positioning uncertainty is achieved using this approach. When the TDRSS orbit location is provided by this approach, the two-way range rate from a single TDRSS (i.e. West only) can provide T/P orbits with sub-meter radial accuracies and two meter RMS total position agreement with SLR defined orbits. These preliminary results indicate improved modeling of the TDRSS measurement through the elimination of heretofore neglected effects like the motion of the T/P TDRSS antenna and improved modeling of ionospheric and atmospheric refractive effects, and the inclusion of TDRSS East in the analysis are warranted. Through these improvements, TDRSS can make a significant contribution to geopotential recovery and precision OD.

Teles, Jerome; Putney, B.; Phelps, J.; Mccarthy, J.; Eddy, W.; Klosko, S.

1993-01-01

71

Precise orbit determination of the Lunar Reconnaissance Orbiter and first gravity field results

NASA Astrophysics Data System (ADS)

The Lunar Reconnaissance Orbiter (LRO) was launched in 2009 and is expected to orbit the Moon until the end of 2014. Among other instruments, LRO has a highly precise altimeter on board demanding an orbit accuracy of one meter in the radial component. Precise orbit determination (POD) is achieved with radiometric observations (Doppler range rates, ranges) on the one hand, and optical laser ranges on the other hand. LRO is the first satellite at a distance of approximately 360 000 to 400 000 km from the Earth that is routinely tracked with optical laser ranges. This measurement type was introduced to achieve orbits of higher precision than it would be possible with radiometric observations only. In this contribution we investigate the strength of each measurement type (radiometric range rates, radiometric ranges, optical laser ranges) based on single-technique orbit estimation. In a next step all measurement types are combined in a joined analysis. In addition to POD results, preliminary gravity field coefficients are presented being a subsequent product of the orbit determination process. POD and gravity field estimation was accomplished with the NASA/GSFC software packages GEODYN and SOLVE.

Maier, Andrea; Baur, Oliver

2014-05-01

72

Orbit Determination Accuracy for Comets on Earth-Impacting Trajectories

NASA Technical Reports Server (NTRS)

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

Kay-Bunnell, Linda

2004-01-01

73

Precision orbit determination using TOPEX\\/Poseidon TDRSS observations

The TOPEX\\/Poseidon (T\\/P) Mission carries a variety of packages to support experimental, precision and operational orbit determination. Included are a GPS transponder, laser retro-reflectors, the French-developed Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) Doppler tracking system and a Tracking Data Relay Satellite System (TDRSS) transponder. Presently, TDRSS tracking is used for operational orbit support and is processed with force

Jerome Teles; B. Putney; J. Phelps; J. McCarthy; W. Eddy; S. Klosko

1993-01-01

74

GEOS-C orbit determination with satellite to satellite tracking

NASA Technical Reports Server (NTRS)

This report studies the feasibility of employing satellite to satellite tracking in lieu of ground based tracking to satisfy the orbit determination requirements of the GEOS-C mission. It is shown that with proper estimation procedures it is possible to obtain from S.S.T. data a GEOS-C orbit whose altitude error averages about 1 meter. The usefulness of this data type for geopotential recovery is also indicated.

Argentiero, P.; Garza-Robles, R.

1975-01-01

75

GEOS-C orbit determination with Satellite to Satellite Tracking

NASA Technical Reports Server (NTRS)

This report studies the feasibility of employing satellite to satellite tracking in lieu of ground based tracking to satisfy the orbit determination requirements of the GEOS-C mission. It is shown that with proper estimation procedures it is possible to obtain from Satellite to Satellite Tracking data a GEOS-C orbit whose altitude error averages about 1 meter. The usefulness of this data type for geopotential recovery is also indicated.

Argentiero, P.; Garza-Robles, R.

1975-01-01

76

Implementation of a low-cost, commercial orbit determination system

NASA Technical Reports Server (NTRS)

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

Corrigan, Jim

1994-01-01

77

One year of Galileo IOV orbit and clock determination

NASA Astrophysics Data System (ADS)

With activation of the fourth Galileo satellite, the Galileo In-Orbit Validation (IOV) phase was achieved in December 2012. The Galileo IOV constellation consists of Proto Flight Model (PFM) and Flight Model 2 (FM2) launched in October 2011 and FM3 and FM4 launched in October 2012. Although the satellites are transmitting navigation signals on all designated frequencies, transmission of the navigation message has not yet started. However, the availability of an orbit product is a prerequisite for most user applications. To support early applications of Galileo, IOV orbit and clock parameters are estimated from observations of the Cooperative Network for GNSS Observation (CONGO) and the Multi-GNSS Experiment (MGEX) of the International GNSS Service (IGS). The quality of these GNSS-only orbits as evaluated by internal consistency tests and Satellite Laser Ranging (SLR) residuals is in general on the one decimeter level. However, the orbits suffer from systematic errors depending on the elevation of the Sun above the orbital plane. These errors show up, e.g., as a bump in the Allan deviation of the estimated clock parameters at the orbital frequency. We started with the Galileo orbit and clock determination in January 2012 and 2013 for PFM/FM2 and FM3/FM4, respectively. The time period of more than one year for PFM/FM2 allows for a proper analysis of the systematic errors. The impact of including SLR observations for a combined GNSS+SLR orbit determination, namely a reduction of the systematic errors, is demonstrated. Finally, the performance of the different clocks on board the IOV satellites (Rubidium clocks and Hydrogen masers) is evaluated and compared with other state-of-the-art GNSS satellite clocks.

Steigenberger, Peter; Hackel, Stefan; Hugentobler, Urs; Montenbruck, Oliver

2013-04-01

78

GOCE: precise orbit determination for the entire mission

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

79

NASA Technical Reports Server (NTRS)

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

Weeks, C. J.

1986-01-01

80

Evaluation of semiempirical atmospheric density models for orbit determination applications

NASA Astrophysics Data System (ADS)

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.

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

1994-05-01

81

Evaluation of semiempirical atmospheric density models for orbit determination applications

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

82

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

83

Orbit determination of space objects based on sparse optical data

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

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

2010-12-23

84

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

85

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

86

NASA Astrophysics Data System (ADS)

Representing spacecraft orbit anomalies between two separate states is a challenging but an important problem in achieving space situational awareness for an active spacecraft. Incorporation of such a capability could play an essential role in analyzing satellite behaviors as well as trajectory estimation of the space object. A general way to deal with the anomaly problem is to add an estimated perturbing acceleration such as dynamic model compensation (DMC) into an orbit determination process based on pre- and post-anomaly tracking data. It is a time-consuming numerical process to find valid coefficients to compensate for unknown dynamics for the anomaly. Even if the orbit determination filter with DMC can crudely estimate an unknown acceleration, this approach does not consider any fundamental element of the unknown dynamics for a given anomaly. In this paper, a new way of representing a spacecraft anomaly using an interpolation technique with the Thrust-Fourier-Coefficients (TFCs) is introduced and several anomaly cases are studied using this interpolation method. It provides a very efficient way of reconstructing the fundamental elements of the dynamics for a given spacecraft anomaly. Any maneuver performed by a satellite transitioning between two arbitrary orbital states can be represented as an equivalent maneuver using an interpolation technique with the TFCs. Given unconnected orbit states between two epochs due to a spacecraft anomaly, it is possible to obtain a unique control law using the TFCs that is able to generate the desired secular behavior for the given orbital changes. This interpolation technique can capture the fundamental elements of combined unmodeled anomaly events. The interpolated orbit trajectory, using the TFCs compensating for a given anomaly, can be used to improve the quality of orbit fits through the anomaly period and therefore help to obtain a good orbit determination solution after the anomaly. Orbit Determination Toolbox (ODTBX) is modified to adapt this technique in order to verify the performance of this interpolation approach. Spacecraft anomaly cases are based on either single or multiple low or high thrust maneuvers and the unknown thrust accelerations are recovered and compared with the true thrust acceleration. The advantage of this approach is to easily append TFCs and its dynamics to the pre-built ODTBX, which enables us to blend post-anomaly tracking data to improve the performance of the interpolation representation in the absence of detailed information about a maneuver. It allows us to improve space situational awareness in the areas of uncertainty propagation, anomaly characterization and track correlation.

Ko, H.; Scheeres, D.

2014-09-01

87

Precise orbit determination of Beidou Satellites at GFZ

NASA Astrophysics Data System (ADS)

In December 2012 the Signal-In-Space Interface Control Document (ICD) of the BeiDou Navigation Satellite System (BeiDou system) was published. Currently the initial BeiDou regional navigation satellite system consisting of 14 satellites was completed, and provides observation data of five Geostationary-Earth-Orbit (GEO)satellites, five Inclined-GeoSynchronous-Orbit (IGSO) satellites and four Medium-Earth-Orbit (MEO) satellites. The Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences (GFZ) contributes as one of the analysis centers to the International GNSS Service (IGS) since many years. In 2012 the IGS began the "Multi GNSS EXperiment" (MGEX), which supports the new GNSS, such as Galileo, Compass, and QZSS. Based on tracking data of BeiDou-capable receivers from the MGEX and chinese BeiDou networks up to 45 global distributed stations are selected to estimate orbit and clock parameters of the GPS/BeiDou satellites. Some selected results from the combined GPS/BeiDou data processing with 10 weeks of data from 2013 are shown. The quality of the orbit and clock products are assessed by means of orbit overlap statistics, clock stabilities as well as an independent validation with SLR measurements. At the end an outlook about GFZ AC's future Multi-GNSS activities will be given.

Deng, Zhiguo; Ge, Maorong; Uhlemann, Maik; Zhao, Qile

2014-05-01

88

Precise Orbit Determination of BeiDou Navigation Satellite System

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

89

A Role for Improved Angular Observations in Geosynchronous Orbit Determination

NASA Astrophysics Data System (ADS)

The goal of this thesis is to show that improved angular observations can aid in the determination of satellite position and velocity in the geosynchronous orbit regime. Raven is a new sensor being developed by the U.S. Air Force Research Laboratory which should allow for angular observations of satellites to be made with a standard deviation of 1 arcsecond (which maps into approximately 170 meters at geosynchronous altitude); this is an order of magnitude improvement over traditional angular observation techniques and represents state of the art accuracy of angular observations for geosynchronous orbit determination work. Simulation studies are undertaken to show that these angular observations can be used in the orbit determination process both as the only cracking data source and as a supplement to other tracking data sources such as radar and radio transponder ranges. Results from the radio transponder range analysis are extended to cover Satellite Laser Ranging (SLR) and Global Positioning System (GPS) observation types as well. The studies target both space surveillance and owner/operator mission support aspects of orbit determination although the emphasis will be on mission support satellite operations. Parameters varied in the simulation studies include the number of observing stations, the density of the angular observations, and the number of nights of optical tracking. The data simulations are calibrated based on real data results from a geosynchronous satellite to ensure the integrity of the simulations and the accuracy of the results. The studies show that including the improved angular observations with traditional high accuracy range observations produces a significant improvement in orbit determination accuracy over the range observations alone. The studies also show single site geosynchronous orbit determination is an attractive alternative when combining improved angular and high accuracy range observations.

Sabol, Christopher Andrew

1998-12-01

90

The role of laser determined orbits in geodesy and geophysics

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

91

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

NASA Technical Reports Server (NTRS)

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.

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

92

Analysis of orbital configurations for geocenter determination with GPS and low-Earth orbiters

NASA Astrophysics Data System (ADS)

We use a series of simulated scenarios to characterize the observability of geocenter location with GPS tracking data. We examine in particular the improvement realized when a GPS receiver in low Earth orbit (LEO) augments the ground network. Various orbital configurations for the LEO are considered and the observability of geocenter location based on GPS tracking is compared to that based on satellite laser ranging (SLR). The distance between a satellite and a ground tracking-site is the primary measurement, and Earth rotation plays important role in determining the geocenter location. Compared to SLR, which directly and unambiguously measures this distance, terrestrial GPS observations provide a weaker (relative) measurement for geocenter location determination. The estimation of GPS transmitter and receiver clock errors, which is equivalent to double differencing four simultaneous range measurements, removes much of this absolute distance information. We show that when ground GPS tracking data are augmented with precise measurements from a GPS receiver onboard a LEO satellite, the sensitivity of the data to geocenter location increases by more than a factor of two for Z-component. The geometric diversity underlying the varying baselines between the LEO and ground stations promotes improved global observability, and renders the GPS technique comparable to SLR in terms of information content for geocenter location determination. We assess a variety of LEO orbital configurations, including the proposed orbit for the geodetic reference antenna in space mission concept. The results suggest that a retrograde LEO with altitude near 3,000 km is favorable for geocenter determination.

Kuang, Da; Bar-Sever, Yoaz; Haines, Bruce

2015-02-01

93

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

NASA Astrophysics Data System (ADS)

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.

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

94

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

95

An autonomous orbit determination method for MEO and LEO satellite

NASA Astrophysics Data System (ADS)

A reliable and secure navigation system and assured autonomous capability of satellite are in high demand in case of emergencies in space. This paper introduces a novel autonomous orbit determination method for Middle-Earth-Orbit and Low-Earth-Orbit (MEO and LEO) satellite by observing space objects whose orbits are known. Generally, the geodetic satellites, such as LAGEOS and ETALONS, can be selected as the space objects here. The precision CCD camera on tracking gimbal can make a series of photos of the objects and surrounding stars when MEO and LEO satellite encounters the space objects. Then the information processor processes images and attains sightings and angular observations of space objects. Several clusters of such angular observations are incorporated into a batch least squares filter to obtain an orbit determination solution. This paper describes basic principle and builds integrated mathematical model. The accuracy of this method is analyzed by means of computer simulation. Then a simulant experiment system is built, and the experimental results demonstrate the feasibility and effectiveness of this method. The experimental results show that this method can attain the accuracy of 150 meters with angular observations of 1 arcsecond system error.

Zhang, Hui; Wang, Jin; Yu, Guobin; Zhong, Jie; Lin, Ling

2014-09-01

96

Analysis of HY2A precise orbit determination using DORIS

NASA Astrophysics Data System (ADS)

HY2A is the first Chinese marine dynamic environment satellite. The payloads include a radar altimeter to measure the sea surface height in combination with a high precision orbit to be determined from tracking data. Onboard satellite tracking includes GPS, SLR, and the DORIS DGXX receiver which delivers phase and pseudo-range measurements. CNES releases raw phase and pseudo-range measurements with RINEX DORIS 3.0 format and pre-processed Doppler range-rate with DORIS 2.2 data format. However, the VMSI software package developed by Van Martin Systems, Inc which is used to estimate HY2A DORIS orbits can only process Doppler range-rate but not the DORIS phase data which are available with much shorter latency. We have proposed a method of constructing the phase increment data, which are similar to range-rate data, from RINEX DORIS 3.0 phase data. We compute the HY2A orbits from June, 2013 to August, 2013 using the POD strategy described in this paper based on DORIS 2.2 range-rate data and our reconstructed phase increment data. The estimated orbits are evaluated by comparing with the CNES precise orbits and SLR residuals. Our DORIS-only orbits agree with the precise GPS + SLR + DORIS CNES orbits radially at 1-cm and about 3-cm in the other two directions. SLR test with the 50° cutoff elevation shows that the CNES orbit can achieve about 1.1-cm accuracy in radial direction and our DORIS-only POD solutions are slightly worse. In addition, other HY2A DORIS POD concerns are discussed in this paper. Firstly, we discuss the frequency offset values provided with the RINEX data and find that orbit accuracy for the case when the frequency offset is applied is worse than when it is not applied. Secondly, HY2A DORIS antenna z-offsets are estimated using two kinds of measurements from June, 2013 to August, 2013. The results show that the measurement errors contribute a total of about 2-cm difference of estimated z-offset. Finally, we estimate HY2A orbits selecting 3 days with severe geomagnetic storm activity and SLR residuals suggest that estimating a drag coefficient every 6 h without any constraint is sufficient for maintaining orbit accuracy.

Gao, Fan; Peng, Bibo; Zhang, Yu; Evariste, Ngatchou Heutchi; Liu, Jihua; Wang, Xiaohui; Zhong, Min; Lin, Mingsen; Wang, Nazi; Chen, Runjing; Xu, Houze

2015-03-01

97

Precision orbit determination at the NASA Goddard Space Flight Center

The GEODYN Computer program has been developed by the Geodynamics Branch at the NASA Goddard Space Flight Center (GSFC) for accurate satellite orbit and tracking data analysis. The software is currently used for baseline solutions for the Crustal Dynamic Project (Smith et al. \\/1\\/), gravity field determination for the TOPEX\\/POSEIDON mission (Marsh et al. \\/2\\/), SEASAT and LAGEOS data analysis,

B. Putney; R. Kolenkiewicz; D. Smith; P. Dunn; M. H. Torrence

1990-01-01

98

Implementation of a low-cost, commercial orbit determination system

NASA Technical Reports Server (NTRS)

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.

Corrigan, Jim

1994-01-01

99

Modeling GPS satellite attitude variation for precise orbit determination

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

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

1996-01-01

100

Method of resolving radio phase ambiguity in satellite orbit determination

For satellite orbit determination, the most accurate observable available today is microwave radio phase, which can be differenced between observing stations and between satellites to cancel both transmitter- and receiver-related errors. For maximum accuracy, the integer cycle ambiguities of the doubly differenced observations must be resolved. To perform this ambiguity resolution, a bootstrapping strategy is proposed. This strategy requires the

Charles C. Councelman III; Richard I. Abbot

1989-01-01

101

Influence of close encounters on the determination of cometary orbits

It has been shown that the precise determination of the motion of P\\/Shajn-Schaldach over a long time interval is practically impossible due to repeated close encounters with Jupiter, and that it would remain so even if the orbit of the comet were known with a much greater accuracy. An attempt is made to understand to what extent the possibility of

A. Carusi; E. Perozzi; G. B. Valsecchi; E. Pittich

1988-01-01

102

The construction of initial-data sets representing binary black-hole configurations in quasicircular orbits is studied in the context of the conformal-imaging formalism. An effective-potential approach for locating quasicircular orbits is outlined for the general case of two holes of arbitrary size and with arbitrary spins. Such orbits are explicitly determined for the case of two equal-sized nonrotating holes, and the innermost

Gregory B. Cook

1994-01-01

103

NASA Astrophysics Data System (ADS)

It has been over half a century since the launch of the first artificial satellite Sputnik in 1957, which marks the beginning of the Space Age. During the past 50 years, with the development and innovations in various fields and technologies, satellite application has grown more and more intensive and extensive. This thesis is based on three major research projects which the author joined in. These representative projects cover main aspects of satellite orbit theory and application of precise orbit determination (POD), and also show major research methods and important applications in orbit dynamics. Chapter 1 is an in-depth research on analytical theory of satellite orbits. This research utilizes general transformation theory to acquire high-order analytical solutions when mean-element method is not applicable. These solutions can be used in guidance and control or rapid orbit forecast within the accuracy of 10-6. We also discuss other major perturbations, each of which is considered with improved models, in pursuit of both convenience and accuracy especially when old models are hardly applicable. Chapter 2 is POD research based on observations. Assuming a priori force model and estimation algorithm have reached their accuracy limits, we introduce empirical forces to Shenzhou-type orbit in order to compensate possible unmodeled or mismodeled perturbations. Residuals are analyzed first and only empirical force models with actual physical background are considered. This not only enhances a posteriori POD accuracy, but also considerably improves the accuracy of orbit forecast. This chapter also contains theoretical discussions on modeling of empirical forces, computation of partial derivatives and propagation of various errors. Error propagation helps to better evaluate orbital accuracy in future missions. Chapter 3 is an application of POD in space geodesy. GRACE satellites are used to obtain Antarctic temporal gravity field between 2004 and 2007. Various changes from traditional methods are implemented to better represent the regional temporal gravity field in this work. As a thesis in astrodynamics, this chapter will concentrate on orbit problems and estimation approaches. Although most details in geophysics are skipped, gravity field solutions will be displayed and the preliminary images of Antarctic mass flux will be revealed. These researches are summarized but not concluded in this thesis. Many problems have been left in all the aspects mentioned in this thesis and need to be studied in future researches, not to mention that the fast developing space technology keeps redefining our traditional knowledge with new concepts and elements. So future work and directions will be discussed at the end of the thesis, expecting further progress upon the present achievements.

Tang, J. S.

2011-03-01

104

Orbit Determination Support for the Microwave Anisotropy Probe (MAP)

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

105

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

106

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

107

Precise Orbit Determination for a New Horizons KBO

NASA Astrophysics Data System (ADS)

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

Benecchi, Susan

2013-10-01

108

NASA Astrophysics Data System (ADS)

A simple procedure is developed to determine orbital elements of an object orbiting in a central force field which contribute more than three independent celestial positions. By manipulation of formal three point Gauss method of orbit determination, an initial set of heliocentric state vectors r i and is calculated. Then using the fact that the object follows the path that keep the constants of motion unchanged, I derive conserved quantities by applying simple linear regression method on state vectors r i and . The best orbital plane is fixed by applying an iterative procedure which minimize the variation in magnitude of angular momentum of the orbit. Same procedure is used to fix shape and orientation of the orbit in the plane by minimizing variation in total energy and Laplace Runge Lenz vector. The method is tested using simulated data for a hypothetical planet rotating around the sun.

Mirtorabi, Taghi

2014-01-01

109

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

NASA Technical Reports Server (NTRS)

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

Herberg, Joseph R.; Folta, David C.

1993-01-01

110

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

NASA Astrophysics Data System (ADS)

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

Herberg, Joseph R.; Folta, David C.

1993-02-01

111

GPS-Based Navigation And Orbit Determination for the AMSAT AO-40 Satellite

NASA Technical Reports Server (NTRS)

The AMSAT OSCAR-40 (AO-40) spacecraft occupies a highly elliptical orbit (HEO) to support amateur radio experiments. An interesting aspect of the mission is the attempted use of GPS for navigation and attitude determination in HEO. Previous experiences with GPS tracking in such orbits have demonstrated the ability to acquire GPS signals, but very little data were produced for navigation and orbit determination studies. The AO-40 spacecraft, flying two Trimble Advanced Navigation Sensor (TANS) Vector GPS receivers for signal reception at apogee and at perigee, is the first to demonstrate autonomous tracking of GPS signals from within a HEO with no interaction from ground controllers. Moreover, over 11 weeks of total operations as of June 2002, the receiver has returned a continuous stream of code phase, Doppler, and carrier phase measurements useful for studying GPS signal characteristics and performing post-processed orbit determination studies in HEO. This paper presents the initial efforts to generate AO-40 navigation solutions from pseudorange data reconstructed from the TANS Vector code phase, as well as to generate a precise orbit solution for the AO-40 spacecraft using a batch filter.

Davis, George; Moreau, Michael; Carpenter, Russell; Bauer, Frank

2002-01-01

112

A fuzzy clustering application to precise orbit determination

In recent years, fuzzy logic techniques have been successfully applied in geodesy problems, in particular to GPS. The aim of this work is to test a fuzzy-logic method with an enhanced probability function as a tool to provide a reliable criteria for weighting scheme for satellite-laser-ranging (SLR) station observations, seeking to optimize their contribution to the precise orbit determination (POD)

Jesus Soto; M. Isabel Vigo Aguiar; Antonio Flores-Sintas

2007-01-01

113

Orbit Determination Support for the Microwave Anisotropy Probe (MAP)

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

114

Orbit Determination Support for the Microwave Anisotropy Probe (MAP)

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

115

Orbit determination with the tracking data relay satellite system

NASA Technical Reports Server (NTRS)

The possibility of employing the tracking data relay satellite system to satisfy the orbit determination demands of future applications missions is investigated. It is shown that when the relay satellites are continuously and independently tracked from ground stations it is possible, using six hour data arcs, to recover user satellite state with an average error of about 25 m radially, 260 m along track, and 20 m cross track. For this arc length, range sum data and range sum rate data are equally useful in determining orbits. For shorter arc lengths (20 min), range sum rate data is more useful than range sum data. When relay satellites are not continuously tracked, user satellite state can be recovered with an average error of about 140 m radially, 515 m along track, and 110 m cross track. These results indicate that the TDRS system can be employed to satisfy the orbit determination demands of applications missions, such as the MAGSAT and potential gradiometer missions, provided the relay satellites are continuously and independently tracked.

Argentiero, P.; Loveless, F.

1977-01-01

116

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

117

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

118

Gravity Recovery and Interior Laboratory Mission (GRAIL) Orbit Determination

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

119

Orbital metastasis as initial manifestation of a widespread papillary thyroid microcarcinoma.

Papillary thyroid carcinomas (PTCs), particularly microcarcinomas, rarely metastasise to the orbit. We report a case of a 49-year-old woman with a right supraorbital mass and unremarkable physical examination of the thyroid gland region. Orbital CT scan showed an expansile lytic lesion in the orbital plate of the frontal bone with a soft tissue component. An incision biopsy revealed metastatic well-differentiated thyroid carcinoma. Thyroid ultrasound was normal except for a subcentimetre nodule in the right lobe. The patient underwent total thyroidectomy where histopathology showed a subcentimetre follicular variant PTC. She subsequently received radioactive iodine therapy. Post-therapy whole body scan revealed metastatic thyroid tissues in the right orbital and posterior parietal, and left shoulder and hip areas. Although infrequent, metastatic thyroid carcinoma should be considered in patients with orbital metastasis even when neck examination is normal. In rare cases, this may be the initial manifestation of a widely metastatic papillary thyroid microcarcinoma. PMID:25819821

Pagsisihan, Daveric Ablis; Aguilar, Anthony Harvey Isabelo; Maningat, Ma Patricia Deanna Delfin

2015-01-01

120

NASA Technical Reports Server (NTRS)

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. Jason-1 is no exception and has set a 1 cm radial orbit accuracy goal, which represents a factor of two improvement over what is currently being achieved for T/P. The challenge to precision orbit determination (POD) is both achieving the 1 cm radial orbit accuracy and evaluating and validating the performance of the 1 cm orbit. Fortunately, Jason-1 POD can rely on four independent tracking data types including near continuous tracking data from the dual frequency codeless BlackJack GPS receiver. In addition, to the enhanced GPS receiver, Jason-1 carries significantly improved SLR and DORIS tracking systems along with the altimeter itself. We demonstrate the 1 cm radial orbit accuracy goal has been achieved using GPS data alone in a reduced dynamic solution. It is also shown that adding SLR data to the GPS-based solutions improves the orbits even further. In order to assess the performance of these orbits it is necessary to process all of the available tracking data (GPS, SLR, DORIS and altimeter crossover differences) as either dependent or independent of the orbit solutions. It was also necessary to compute orbit solutions using various combinations of the four available tracking data in order to independently assess the orbit performance. Towards this end, we have greatly improved orbits determined solely from SLR+DORIS data by applying the reduced dynamic solution strategy. In addition, we have computed reduced dynamic orbits based on SLR, DORIS and crossover data that are a significant improvement over the SLR and DORIS based dynamic solutions. These solutions provide the best performing orbits for independent validation of the GPS-based reduced dynamic orbits.

Luthcke, Scott B.; Zelensky, Nikita P.; Rowlands, David D.; Lemoine, Frank G.; Williams, Teresa A.

2003-01-01

121

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

NASA Technical Reports Server (NTRS)

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

Shores, P. W. (inventor)

1976-01-01

122

On-board orbit determination for applications satellites

NASA Technical Reports Server (NTRS)

An algorithm for satellite orbit determination is described which would be suitable for use with an on-board computer with limited core storage. The proposed filter is recursive on a pass-by-pass basis and features a fading memory to account for the effect of gravity field error. Only a single pass of Doppler data needs to be stored at any time and the data may be acquired from two reference beacons located within the Continental United States. The results of both simulated data and real data reductions demonstrate that the satellite's position can be determined to within one kilometer when a 4 x 4 recovery field is used.

Morduch, G. E.; Lefler, J. G.; Argentiero, P. D.; Garza-Robles, R.

1978-01-01

123

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

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.

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

124

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

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

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

2008-04-15

125

Numerical black hole initial data with low eccentricity based on post-Newtonian orbital parameters

Black hole binaries on non-eccentric orbits form an important subclass of gravitational wave sources, but it is a non-trivial issue to construct numerical initial data with minimal initial eccentricity for numerical simulations. We compute post-Newtonian orbital parameters for quasi-spherical orbits using the method of Buonanno, Chen and Damour (2006) and examine the resulting eccentricity in numerical simulations. Four different methods are studied resulting from the choice of Taylor-expanded or effective-one-body Hamiltonians, and from two choices for the energy flux. The eccentricity increases for unequal masses and for spinning black holes, but remains smaller than that obtained from previous post-Newtonian approaches. The effective-one-body Hamiltonian offers advantages for decreasing initial separation as expected, but in the context of this study also performs significantly better than the Taylor-expanded Hamiltonian for binaries with spin.

Benny Walther; Bernd Bruegmann; Doreen Mueller

2010-03-26

126

Modeling radiation forces acting on satellites for precision orbit determination

NASA Astrophysics Data System (ADS)

Models of the TOPEX/Poseidon spacecraft are developed by means of finite-element analyses for use in generating acceleration histories for various orbit orientations which account for nonconservative radiation forces. The acceleration profiles are developed with an analysis based on the use of the 'box-wing' model in which the satellite is modeled as a combination of flat plates. The models account for the effects of solar, earth-albedo, earth-IR, and spacecraft-thermal radiation. The finite-element analysis gives the total force and induced accelerations acting on the satellite. The plate types used in the analysis have parameters that can be adjusted to optimize model performance according to the micromodel analysis and tracking observations. Acceleration related to solar radiation pressure is modeled effectively, and the techniques are shown to be useful for the precise orbit determinations required for spacecraft such as the TOPEX/Poseidon.

Marshall, J. A.; Antreasian, P. G.; Rosborough, G. W.; Putney, B. H.

1992-08-01

127

Modeling radiation forces acting on satellites for precision orbit determination

NASA Technical Reports Server (NTRS)

Models of the TOPEX/Poseidon spacecraft are developed by means of finite-element analyses for use in generating acceleration histories for various orbit orientations which account for nonconservative radiation forces. The acceleration profiles are developed with an analysis based on the use of the 'box-wing' model in which the satellite is modeled as a combination of flat plates. The models account for the effects of solar, earth-albedo, earth-IR, and spacecraft-thermal radiation. The finite-element analysis gives the total force and induced accelerations acting on the satellite. The plate types used in the analysis have parameters that can be adjusted to optimize model performance according to the micromodel analysis and tracking observations. Acceleration related to solar radiation pressure is modeled effectively, and the techniques are shown to be useful for the precise orbit determinations required for spacecraft such as the TOPEX/Poseidon.

Marshall, J. A.; Antreasian, P. G.; Rosborough, G. W.; Putney, B. H.

1992-01-01

128

Automated Precision Orbit Determination for TOPEX/Poseidon with GPS

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

129

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

130

Improved initialization conditions and single impulsive maneuvers for -invariant relative orbits

NASA Astrophysics Data System (ADS)

The determination of the initial conditions for long-term bounded relative motion under natural perturbations is an important theme in satellite cluster flight. Considering the most significant perturbation of the geopotential, namely, the term, many researchers have proposed -mitigating initial conditions for satellite-bounded relative motion. To improve the existing -invariant conditions, two new methods for finding the correction factor are presented in this paper. In these two methods, Method 1 is obtained by minimizing the possible maximum drift in the along-track relative motion. However, Method 2 is designed by nullifying the rates of change of the bounds of the relative motion. Then the geometric character, such as the self-intersection of the -invariant relative orbits, is discussed. The conditions of 0, 1 and 2 (the possible maximum number) self-intersection points are also derived. Then, using Gauss's equations of planetary motion, an analytical optimal single-impulsive maneuver is deduced to guarantee the secular bounded relative motion under , too. Some numerical simulations are performed to validate the corresponding theoretical predictions. The results demonstrate that the proposed methods enhance performance for achieving the bounded relative motion under effects and can be used for future satellite cluster flight missions.

Dang, Zhaohui; Wang, Zhaokui; Zhang, Yulin

2015-03-01

131

Precise Orbit Determination for a New Horizons KBO

NASA Astrophysics Data System (ADS)

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

Benecchi, Susan

2014-10-01

132

Detection and orbit determination of tethered satellite systems

NASA Astrophysics Data System (ADS)

A systematic algorithm for determining which satellites are tether-connected is described. It is assumed that observations in the forms of range, azimuth and elevation data, for several satellites, including singles, two-satellite tethered systems, and three-satellite tethered systems are available. The detection process is performed using the dynamic model and a minimum variance batch filter to process simulated observations over a period of ten minutes. In the process, the estimated acceleration per unit length between pairs of satellites due to a tether is assumed to be constant during this "short arc" observation period. The values of acceleration per unit length are used as indicators of which pairs of satellites are connected. Use of the algorithm is illustrated by applying it to a set of nine satellites that includes two tethered pairs. For small librational motion of the tethered pairs, values of the constraint accelerations per unit length that are large relative to zero were obtained. On the other hand, values very close to zero were obtained for un-tethered pairs. These results indicate that non-librating, two-satellite tethered systems can be successfully identified (i.e. "detected") when perfect and small-level noise corrupted observations are available. However, identification of two-satellite tethered systems with the large libration angle, or those with a very short tether when medium and large levels of noise are present is more difficult. The detection of a three-satellite tethered system was also performed with the same algorithm. After detection of a two-satellite tethered system (or three-satellite) is performed, its orbit may be determined by using long arcs of observations (over one orbital period). In the long arc estimation process used herein, the constraint acceleration per unit length is considered to be a time-varying variable. For an exemplary set of satellites, results for long arc estimations were obtained. Since observation data for both satellites in a tethered system were used and few approximations of the tether dynamics were made, the results are very accurate. The orbital motion of the three-satellite tether system was found to be similar to that of two-satellite tether system when the librational motion was small. The major difference was that larger tether accelerations were present due to another tether connected body. It should be relatively easy to incorporate the new method for detection and motion determination developed in this study into a general orbit determination process. (Abstract shortened by UMI.)

Choe, Nammi Jo

133

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

NASA Technical Reports Server (NTRS)

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.

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

134

10 CFR 9.25 - Initial disclosure determination.

Code of Federal Regulations, 2011 CFR

...Initial disclosure determination. 9.25 Section 9.25 Energy NUCLEAR REGULATORY COMMISSION...Information Act Regulations § 9.25 Initial disclosure determination...to a reasonable alternative time frame for processing. For purposes...

2011-01-01

135

50 CFR 296.9 - Initial determination.

Code of Federal Regulations, 2014 CFR

...Section 296.9 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE CONTINENTAL SHELF FISHERMEN'S CONTINGENCY FUND § 296.9 Initial...

2014-10-01

136

50 CFR 296.9 - Initial determination.

Code of Federal Regulations, 2012 CFR

...Section 296.9 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE CONTINENTAL SHELF FISHERMEN'S CONTINGENCY FUND § 296.9 Initial...

2012-10-01

137

50 CFR 296.9 - Initial determination.

Code of Federal Regulations, 2010 CFR

...Section 296.9 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE CONTINENTAL SHELF FISHERMEN'S CONTINGENCY FUND § 296.9 Initial...

2010-10-01

138

50 CFR 296.9 - Initial determination.

Code of Federal Regulations, 2013 CFR

2013-10-01

139

50 CFR 296.9 - Initial determination.

Code of Federal Regulations, 2011 CFR

2011-10-01

140

The analyzation of satellite orbits using a modified-Gauss determination method

astronomical units) light travels in one mean sidereal day. With these preliminary steps, we are now ready to discuss the deter- mination method. 13 CHAPTER I I I THE DETERMINATION METHOD The method presented here for the determination of the orbit... in the Astronomical Journal in 1965. This method is dependent upon high-speed computers for calculation, and the program written in FORTRAN IV from the discussion in this chapter is available upon request. Initially it will be useful to review some of the basic...

Rupley, James Allen

1967-01-01

141

Filter parameter tuning analysis for operational orbit determination support

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

142

NASA Astrophysics Data System (ADS)

The value of the initial velocity of the stream meteoroids from the parent bodies is given by the physics of the outgassing of the cometary nuclei and by modeling the collisions between asteroids. In both cases the outflow speed of the meteoroid particles are small (Whipple 1951, Hughes 1977, 2000, Gustafson 1989, Jones 1995, Ma et al. 2002) and as result, the most meteoroid streams have similar orbits to either comets or asteroids. The formulae relating the changes of the orbital elements due to the small increment of the velocity were developed, among others by Plavec (1955), Pecina and Simek(1997), Williams (1996, 2001), Ma et al. (2001), Ma and Williams (2002). Assuming that the members of the observed meteor stream evolved dynamically under the influence of gravitational perturbations only, Pittich (1988), Harris and Hughes (1995), Williams (1996, 2001) estimated the initial velocity of the stream meteoroids. In their approach, Harris and Hughes have used the dispersion of the semimajor axes of the stream meteoroids. Williams proposed the method were used the mean orbit of the stream and the orbit of the identified parent body of the stream. The obtained results are not free from the discrepancy, explained partly by the particular orbital structure of the stream. However Kresak (1992) has strongly criticized the attempts to determine the initial velocities of the stream using the statistics of the meteor orbits. He argued that this is essentially impossible, because the dispersion of the initial velocities are masked by much larger measuring errors and also by the accumulated effects of planetary perturbations. In our paper, we decided to verify the reliability of the methods proposed by Harris and Hughes (1995), and by Williams (1996,2001). We made an numerical experiment consisting of the simulation of formation of several meteor streams and their dynamical evolution over 5000 years. We ejected meteoroids particles from the comets: Halley, Swift-Tuttle, Tempel-Tuttle. During the integration, the initial velocities of the stream members were estimated using the methods proposed by Hughes and Harris, and that by Williams. The results which we calculated till present, shows that the velocities obtained by the Williams method are to high when compared with the known velocities of the stream formation. On the other hand, the velocities obtained using Harris and Hughes method are to small. This work was supported by the KBN Project 2-P03-D-007-22.

Jopek, T. J.; Rudawska, R.; Dybczynski, P. A.

2005-08-01

143

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

144

Numerical black hole initial data with low eccentricity based on post-Newtonian orbital parameters

Black hole binaries on noneccentric orbits form an important subclass of gravitational wave sources, but it is a nontrivial issue to construct numerical initial data with minimal initial eccentricity for numerical simulations. We compute post-Newtonian orbital parameters for quasispherical orbits using the method of Buonanno, Chen and Damour, (2006) and examine the resulting eccentricity in numerical simulations. Four different methods are studied resulting from the choice of Taylor-expanded or effective-one-body Hamiltonians, and from two choices for the energy flux. For equal-mass, nonspinning binaries the approach succeeds in obtaining low-eccentricity numerical initial data with an eccentricity of about e=0.002 for rather small initial separations of D > or approx. 10M. The eccentricity increases for unequal masses and for spinning black holes, but remains smaller than that obtained from previous post-Newtonian approaches. The effective-one-body Hamiltonian offers advantages for decreasing initial separation as expected, but in the context of this study also performs significantly better than the Taylor-expanded Hamiltonian for binaries with spin. For mass ratio 4 ratio 1 and vanishing spin, the eccentricity reaches e=0.004. For mass ratio 1 ratio 1 and aligned spins of size 0.85M{sup 2} the eccentricity is about e=0.07 for the Taylor method and e=0.014 for the effective-one-body method.

Walther, Benny; Bruegmann, Bernd; Mueller, Doreen [Theoretical Physics Institute, University of Jena, 07743 Jena (Germany)

2009-06-15

145

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

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

146

NASA Astrophysics Data System (ADS)

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.

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

2012-09-01

147

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

148

NASA Technical Reports Server (NTRS)

Since its' launch on August 10, 1992, the TOPEX/Poseidon satellite hs successfully observed the earth's ocean circulation using a combination of precision orbit determination (POD) and dual-frequency radar altimetry.

Frauenholz, R. B.; Bhat, R. S.; Shapiro, B. E.; Leavitt, R. K.

1998-01-01

149

Analysis of filter tuning techniques for sequential orbit determination

NASA Technical Reports Server (NTRS)

This paper examines filter tuning techniques for a sequential orbit determination (OD) covariance analysis. Recently, there has been a renewed interest in sequential OD, primarily due to the successful flight qualification of the Tracking and Data Relay Satellite System (TDRSS) Onboard Navigation System (TONS) using Doppler data extracted onboard the Extreme Ultraviolet Explorer (EUVE) spacecraft. TONS computes highly accurate orbit solutions onboard the spacecraft in realtime using a sequential filter. As the result of the successful TONS-EUVE flight qualification experiment, the Earth Observing System (EOS) AM-1 Project has selected TONS as the prime navigation system. In addition, sequential OD methods can be used successfully for ground OD. Whether data are processed onboard or on the ground, a sequential OD procedure is generally favored over a batch technique when a realtime automated OD system is desired. Recently, OD covariance analyses were performed for the TONS-EUVE and TONS-EOS missions using the sequential processing options of the Orbit Determination Error Analysis System (ODEAS). ODEAS is the primary covariance analysis system used by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD). The results of these analyses revealed a high sensitivity of the OD solutions to the state process noise filter tuning parameters. The covariance analysis results show that the state estimate error contributions from measurement-related error sources, especially those due to the random noise and satellite-to-satellite ionospheric refraction correction errors, increase rapidly as the state process noise increases. These results prompted an in-depth investigation of the role of the filter tuning parameters in sequential OD covariance analysis. This paper analyzes how the spacecraft state estimate errors due to dynamic and measurement-related error sources are affected by the process noise level used. This information is then used to establish guidelines for determining optimal filter tuning parameters in a given sequential OD scenario for both covariance analysis and actual OD. Comparisons are also made with corresponding definitive OD results available from the TONS-EUVE analysis.

Lee, T.; Yee, C.; Oza, D.

1995-01-01

150

A method for the orbit determination accuracy improvement of a station with a limited motion antenna

A station with limited motion antenna is usually used for the on-orbit control of a geostationary satellite. In order to enhance the capability of running a satellite, it is important to improve the orbit determination accuracy of the singlestation system. This paper presents a method for the orbit determination accuracy improvement with tracking and ranging data from a single station.

Fenglei Wu; Jingyong Liu; Yongqing Liu; Yanning Li; Ping Zhu; Liming Du

2009-01-01

151

Application of variance component estimation to precise orbit determination for ERS-2

Variance component estimation (VCE) is applied to precise orbit determination (POD) of the ERS-2 satellite. Twenty 5-day long arcs in the early three months in 1998 were calculated using the SLR and PRARE data. In the data the adjacent arcs overlap for two days except the intervals for orbit maneuver. The effect of VCE orbit determination on the calculation is

Fei-Peng Zhang; Cheng Huang; Chu-Gang Feng; Xiao-Jun Dong; Xin-Hao Liao

2001-01-01

152

The construction of initial-data sets representing binary black-hole\\u000aconfigurations in quasi-circular orbits is studied in the context of the\\u000aconformal-imaging formalism. An effective-potential approach for locating\\u000aquasi-circular orbits is outlined for the general case of two holes of\\u000aarbitrary size and with arbitrary spins. Such orbits are explicitly determined\\u000afor the case of two equal-sized nonrotating holes, and the innermost

Gregory B. Cook

1994-01-01

153

Cassini Orbit Determination Performance (July 2008 - December 2011)

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

154

NSDL National Science Digital Library

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

Brieske, Joel A.

155

Point-to-point sub-orbital space tourism: Some initial considerations

NASA Astrophysics Data System (ADS)

Several public statements have been made about the possible, or even likely, extension of initial sub-orbital space tourism operations to encompass point-to-point travel. It is the purpose of this paper to explore some of the basic considerations for such a plan, in order to understand both its merits and its problems. The paper will discuss a range of perspectives, from basic physics to market segmentation, from ground segment logistics to spacecraft design considerations. It is important that these initial considerations are grasped before more detailed planning and design takes place.

Webber, Derek

2010-06-01

156

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

157

Orbital Moment Determination in (MnxFe1-x)3O4 Nanoparticles

Nanoparticles of (Mn{sub x}Fe{sub 1-x}){sub 3}O{sub 4} with a concentration ranging from x = 0 to 1 and a crystallite size of 14-15 nm were measured using X-ray absorption spectroscopy and X-ray magnetic circular dichroism to determine the ratio of the orbital moment to the spin moment for Mn and Fe. At low Mn concentrations, the Mn substitutes into the host Fe{sub 3}O{sub 4} spinel structure as Mn{sup 2+} in the tetrahedral A-site. The net Fe moment, as identified by the X-ray dichroism intensity, is found to increase at the lowest Mn concentrations then rapidly decrease until no dichroism is observed at 20% Mn. The average Fe orbit/spin moment ratio is determined to initially be negative and small for pure Fe{sub 3}O{sub 4} nanoparticles and quickly go to 0 by 5%-10% Mn addition. The average Mn moment is anti-aligned to the Fe moment with an orbit/spin moment ratio of 0.12 which gradually decreases with Mn concentration.

Pool, V. L.; Jolley, C.; Douglas, T.; Arenholz, E.; Idzerda, Y. U.

2010-10-22

158

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

NASA Astrophysics Data System (ADS)

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].

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

1999-11-01

159

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

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

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

160

A fuzzy clustering application to precise orbit determination

NASA Astrophysics Data System (ADS)

In recent years, fuzzy logic techniques have been successfully applied in geodesy problems, in particular to GPS. The aim of this work is to test a fuzzy-logic method with an enhanced probability function as a tool to provide a reliable criteria for weighting scheme for satellite-laser-ranging (SLR) station observations, seeking to optimize their contribution to the precise orbit determination (POD) problem. The data regarding the stations were provided by the International Laser Ranging Service (ILRS), NASA/Crustal Dynamics Data Information System (CDDIS) provided the satellite data for testing the method. The software for processing the data is GEODYN II provided by NASA/Goddard Space Flight Center (GSFC). Factors to be considered in the fuzzy-logic clustering are: the total number of LAGEOS passes during the past 12 months, the stability measure of short- and long-term biases, the percentage of LAGEOS normal points that were accepted in CSR weekly LAGEOS analysis, and the RMS uncertainty of the station coordinates. A fuzzy-logic statistical method allows classifying the stations through a clear `degree of belonging' to each station group. This degree of belonging translates into a suitable weight to be assigned to each station in the global solutionE The first tests carried out showed improvements in the RMS of the global POD solution as well as individual stations, to within a few millimeters. We expect further work would lead to further improvements.

Soto, Jesus; Vigo Aguiar, M. Isabel; Flores-Sintas, Antonio

2007-07-01

161

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

162

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

163

Procedure for the Determination of Orbits of Astronomical Bodies

ERIC Educational Resources Information Center

Presents a procedure for finding the elements of the orbit of an astronomical object from three or more observations. From a set of assumed elements an ephemeris is calculated and compared to the observations. (MLH)

Birnbaum, David

1977-01-01

164

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

165

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

166

Orbit determination and prediction of GEO satellite of BeiDou during repositioning maneuver

NASA Astrophysics Data System (ADS)

In order to establish a continuous GEO satellite orbit during repositioning maneuvers, a suitable maneuver force model has been established associated with an optimal orbit determination method and strategy. A continuous increasing acceleration is established by constructing a constant force that is equivalent to the pulse force, with the mass of the satellite decreasing throughout maneuver. This acceleration can be added to other accelerations, such as solar radiation, to obtain the continuous acceleration of the satellite. The orbit determination method and strategy are illuminated, with subsequent assessment of the orbit being determined and predicted accordingly. The orbit of the GEO satellite during repositioning maneuver can be determined and predicted by using C-Band pseudo-range observations of the BeiDou GEO satellite with COSPAR ID 2010-001A in 2011 and 2012. The results indicate that observations before maneuver do affect orbit determination and prediction, and should therefore be selected appropriately. A more precise orbit and prediction can be obtained compared to common short arc methods when observations starting 1 day prior the maneuver and 2 h after the maneuver are adopted in POD (Precise Orbit Determination). The achieved URE (User Range Error) under non-consideration of satellite clock errors is better than 2 m within the first 2 h after maneuver, and less than 3 m for further 2 h of orbit prediction.

Cao, Fen; Yang, XuHai; Li, ZhiGang; Sun, BaoQi; Kong, Yao; Chen, Liang; Feng, Chugang

2014-11-01

167

Precise orbit determination of GLONASS satellites at the European space agency

As an active Analysis Centre of the International GPS Service (IGS) the European Space Operations Centre (ESOC) joined the IGEX program for precise orbit determination of the GLONASS satellite constellation since its inception in 1998. This paper describes the orbit determination processing strategy, the specific GLONASS modelling issues implemented and a discussion of the processing results.

I. Romero; C. Garcia; R. Kahle; J. Dow; T. Martin-Mur

2002-01-01

168

NASA Technical Reports Server (NTRS)

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

Fuchs, A. J. (editor)

1979-01-01

169

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

NASA Technical Reports Server (NTRS)

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

Marr, G.

2003-01-01

170

FIRST ORBIT AND MASS DETERMINATIONS FOR NINE VISUAL BINARIES

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

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

2012-01-15

171

High order F and G power series for orbit determination.

NASA Astrophysics Data System (ADS)

The table of coefficients and exponents of the power series f and g up to derivatives of the 20th order is the main achievement of this paper. The accuracy of the calculation of orbits has been tested by tracing the motion of all planets of the Solar System. Special attention has been paid to high-eccentricity orbits in the two- or three-body problem. Power series from 10th up to 20th order have been used instead of other integration methods.

Bem, J.; Szczodrowska-Kozar, B.

1995-04-01

172

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

NASA Technical Reports Server (NTRS)

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.

Fang, B. T.; Seifert, E.

1985-01-01

173

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

174

42 CFR 405.921 - Notice of initial determination.

Code of Federal Regulations, 2011 CFR

...instructions. When a paper RA is mailed, it must comply with CMS manual instructions that parallel the HIPAA data content and coding requirements. (2) The notice of initial determination must contain: (i) The basis for any full or partial denial...

2011-10-01

175

20 CFR 410.620 - Notice of initial determination.

Code of Federal Regulations, 2011 CFR

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

2011-04-01

176

20 CFR 410.620 - Notice of initial determination.

Code of Federal Regulations, 2010 CFR

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

2010-04-01

177

Applications of square-root information filtering and smoothing in spacecraft orbit determination

NASA Technical Reports Server (NTRS)

The JPL (Jet Propulsion Laboratory) Orbit Determination Software System is a set of computer programs developed for the primary purpose of determining the flight path of deep-space mission spacecraft in NASA's Planetary Program and highly elliptical orbiting spacecraft in Earth orbit. The filtering processes available within the JPL Orbit Determination Software are discussed, and several examples are presented. In particular, solutions obtained by the Square Root Information Filter (SRIF) using Bierman's Estimation Subroutine Library (ESL) are discussed and compared with the solutions obtained by the singular value decomposition (SVD) technique. It is concluded that the SRIF filtering and smoothing algorithms are efficient and numerically stable for well-conditioned systems. The use of Bierman's ESL simplifies the task of maintaining the orbit determination software by providing efficient, tested filtering tools. For solving a large well-conditioned system (rank higher than 120), SRIF is approximately four times faster than SVD; however, for solving an ill-conditioned system, SVD is recommended.

Wang, Tseng-Chan; Collier, James B.; Ekelund, John E.; Breckheimer, Peter J.

1988-01-01

178

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

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

1993-01-01

179

For optimum utilization of satellite-borne instrumentation, it is necessary to know precisely the orbital position of the spacecraft. The objectives are: (1) to derive precise orbits with particular emphasis placed on the altimeter satellite SEASAT; and (2) to utilize the precise orbits, to improve upon atmospheric density determinations for satellite drag modelling purposes. The section on precise orbit determinations is

Derek Anthony Rothwell

1989-01-01

180

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

181

Orbit Determination with the two-body Integrals. III

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

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

2015-01-15

182

RESEARCH ARTICLE Open Access Determinants of smoking initiation among

RESEARCH ARTICLE Open Access Determinants of smoking initiation among women in five European Gritz11 , Mia Hashibe1,12* Abstract Background: The rate of smoking and lung cancer among women is rising in Europe. The primary aim of this study was to determine why women begin smoking in five

Paris-Sud XI, Université de

183

Lunar orbit determination in the presence of unmodeled accelerations

NASA Technical Reports Server (NTRS)

A technique for estimating the state of an artificial satellite in the presence of unmodeled accelerations is presented. The unmodeled acceleration is approximated by a first-order Gauss-Markov sequence which can be separated into a timewise-correlated component and a purely random component. Using this approximation, a sequential procedure for estimating the position, velocity, and the unmodeled acceleration is developed. The method is evaluated by reducing range-rate observations obtained by tracking the Apollo 10 and 11 spacecraft during the lunar-orbit phase of the mission. Numerical results are presented which show that the observation residual pattern lies within the observation noise standard deviation. The values of the estimated components of the unmodeled acceleration are repeatable from orbit to orbit within a given mission and from mission to mission when the same ground track is covered. Finally, the variation in the radial component of the unmodeled acceleration shows a high correlation with the reported location of the lunar surface mascons.

Ingram, D. S.; Tapley, B. D.

1974-01-01

184

Orbit determination of close binary systems using lucky imaging

NASA Astrophysics Data System (ADS)

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.

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

2012-01-01

185

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

186

NASA Astrophysics Data System (ADS)

The values of the initial velocity of the meteoroids ejected from the parent bodies are small and as a result, the most of the young meteoroid streams have similar orbits to their parent bodies. Assuming that the members of the observed meteor stream evolved under the influence of gravitational perturbations mostly, Pittich [1991, Proceedings of the Conference on Dynamic of Small Bodies of the Solar System, Polish-Slovak Conference, Warsaw, October 25 28, 1988, pp. 55-61], Williams [1996, Earth, Moon, Planets 72, 321 326; 2001, Proceedings of the Meteoroids 2001 conference, Kiruna, Sweden, August 6 10, 2001, pp. 33 42] estimated the ejection velocities of the stream meteoroids. Equation relating the ejection velocity ?? and the change ?a of the semi-major axis, Williams (2001), was applied with two slightly different variations. In the first one (M1) as ?a the difference between the mean orbit of the stream and the orbit of the parent body was substituted, in the second one (M2), as ?a the dispersion of semi-major axes around the mean orbit of the stream was used. The results obtained by these two methods are not free from discrepancies, partly explained by the particular orbital structure of the stream. Kresak [1992, Contrib. Astron. Obs. Skalnate Pleso 22, 123 130] strongly criticized the attempts to determine the initial velocities of the stream using the statistics of the meteor orbits. He argued that this is essentially impossible, because the dispersion of the initial velocities are masked by much larger measuring errors and by the accumulated effects of planetary perturbations. In our paper, we study the reliability of M1 and M2 methods. We made a numerical experiment consisting of formation of several meteor streams and their dynamical evolution over 5000 years. We ejected meteoroids particles from the comets: 1P/Halley, 2P/Encke, 55P/Tempel-Tuttle, 109P/Swift-Tuttle and from minor planets (3200) Phaethon and 2002 SY50. During the integration, the ejection velocities were estimated using both M1 and M2 methods. The results show that the velocities obtained by M1 method are unstable: too high or too low, when compared with the known ejection velocities at the time of the stream formation. On the other hand, the velocities obtained using M2 method are too small, mostly. In principle, M2 estimates the dispersion of the distribution of the ejection velocities around the mean value, not the mean value itself. Applying more accurate Equation relating ?? and ?a we decreased the bias of the results, but not their variation observed during the evolution of the streams and the parent bodies. We have found that the variability of the estimated ejection velocities was caused mainly by the gravitational changes of the semi-major axis and eccentricity of the parent body. In brief, we have found that the reliability of the results obtained by M1 or M2 method are low, and have to be used with great care.

Rudawska, R.; Jopek, T. J.; Dybczy?ski, P. A.

2005-12-01

187

The flux of long-period comets and the initial orbital distribution of the Oort cloud

NASA Astrophysics Data System (ADS)

Several simulations have been performed on the evolution of the Oort cloud of comets over the age of the solar system using 10 different stellar encounter sequences. An innermost part of the cloud was also introduced (semimajor axes between 1,100 and 3,000 au). Attention is focused on the observable comets, i.e., comets passing at less than 5 au from the Sun, the end of the integrations representing the present time. We apply fading laws to returning comets when comparing with observations, and we use a final period of 30 million years for the numerical experiments on the flux of passing stars. These simulations allow us to place constraints on the initial and/or present Oort cloud distribution of orbital energy, and, possibly, on the ecliptic inclination distribution of the cloud. Moreover, we may highlight the dependence of the observable Oort spike and the present Oort cloud on the stellar sequence. Indeed, some preliminary results have shown that the energy distribution of the final Oort cloud is critically dependent on the few strongest stellar encounters that obviously differ from one sequence to another. One of our main goals is to evaluate, what is the most concentrated initial Oort cloud allowing to obtain an observable Oort spike consistent with the observations (the total initial mass of the cloud being the same).

Fouchard, M.; Rickman, H.; Valsecchi, G.; Froeschlé, C.

2014-07-01

188

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

189

Precise orbit determination and gravity field improvement for the ERS satellites

The radial orbit error has long been the major error source in ERS-1 altimetry, crippled by having only satellite laser ranging for precise tracking and relying on insufficiently accurate general-purpose gravity field models. Altimeter crossovers are used very effectively as additional tracking data to laser ranging. The ERS Tandem Mission even provides the unique possibility to simultaneously determine orbits of

Remko Scharroo; Pieter Visser

1998-01-01

190

NASA Technical Reports Server (NTRS)

Program computes the thermal environment of a spacecraft in a lunar orbit. The quantities determined include the incident flux /solar and lunar emitted radiation/, total radiation absorbed by a surface, and the resulting surface temperature as a function of time and orbital position.

Head, D. E.; Mitchell, K. L.

1967-01-01

191

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

Aleksandar KOSTADINOV: Expected performance of Orbit Determination of the GALILEO Satellites (completed Jänner 2003) In March 2002 the European Union decided to finance the GALILEO orbits (MEOs) at 23600 km altitude. The launch of the first GALILEO satellites can be expected

Schuh, Harald

192

NASA Technical Reports Server (NTRS)

The Memory Test Experiment is a space test of a ferroelectric memory device on a low Earth orbit satellite that launched in November 2010. The memory device being tested is a commercial Ramtron Inc. 512K memory device. The circuit was designed into the satellite avionics and is not used to control the satellite. The test consists of writing and reading data with the ferroelectric based memory device. Any errors are detected and are stored on board the satellite. The data is sent to the ground through telemetry once a day. Analysis of the data can determine the kind of error that was found and will lead to a better understanding of the effects of space radiation on memory systems. The test is one of the first flight demonstrations of ferroelectric memory in a near polar orbit which allows testing in a varied radiation environment. The initial data from the test is presented. This paper details the goals and purpose of this experiment as well as the development process. The process for analyzing the data to gain the maximum understanding of the performance of the ferroelectric memory device is detailed.

MacLeond, Todd C.; Sims, W. Herb; Varnavas,Kosta A.; Ho, Fat D.

2011-01-01

193

Determination of the orbit of the CHAMP satellite based on the laser observations

NASA Astrophysics Data System (ADS)

This work presents the results of orbit determination of the CHAMP satellite from observations of 14 the best SLR stations for year 2002 All computations were based on the Earth combined gravity field model EIGEN-CG01C Reigber et al 2005 In computations was taken the orbital programme GEODYN-II created and accesibled by NASA The got RMS value of the orbit of the CHAMP satellite is better than 30 cm The obtained results show that the orbit of the CHAMP satellite is highly perturbed by the Earth s gravity field and by the atmosphere of the Earth

Lejba, P.

194

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

NASA Technical Reports Server (NTRS)

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 the Ocean Topography Experiment (TOPEX)/Poseidon spacecraft navigation and health and safety operations. The extended Kalman filter was implemented in an orbit determination analysis prototype system, closely related to the Real-Time Orbit Determination System/Enhanced (RTOD/E) system. In addition, the Precision Orbit Determination (POD) team within the GSFC Space Geodesy Branch generated an independent set of high-accuracy trajectories to support the TOPEX/Poseidon scientific data. These latter solutions use the geodynamics (GEODYN) orbit determination system with laser ranging and Doppler Orbitography and Radiopositioning integrated by satellite (DORIS) tracking measurements. The TOPEX/Poseidon trajectories were estimated for November 7 through November 11, 1992, the timeframe under study. Independent assessments were made of the consistencies of solutions produced by the batch and sequential methods. The batch-least-squares solutions were assessed based on the solution residuals, while the sequential solutions were assessed based on primarily the estimated covariances. The batch-least-squares and sequential orbit solutions were compared with the definitive POD orbit solutions. The solution differences were generally less than 2 meters for the batch-least-squares and less than 13 meters for the sequential estimation solutions. After the sequential estimation solutions were processed with a smoother algorithm, position differences with POD orbit solutions of less than 7 meters were obtained. The differences among the POD, GTDS, and filter/smoother solutions can be traced to differences in modeling and tracking data types, which are being analyzed in detail.

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

1994-01-01

195

A development and comparison of two methods of orbit determination

then there have been many contr1butions on' variations of the improvement procedures for the first approximat1on to the preliminary orbit. Gibbs and Encke 3 7 have developed methods for second and higher approximations to Gauss' method. A surv... R3 r3 r2 P2 P3 P3 P2 Pl F1 g ure 2 . Positions in Space The subscripts in F1gure 2 correspond to the three observ- ations. The only values known 1n this Figure are R; and the direction cosines of pl, 1 = 1, 2, 3. The basic problem...

Hughes, Harry Louis

1967-01-01

196

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

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

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

2006-01-01

197

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

198

Satellite orbit determination - A first-hand experience with the first Brazilian satellite SCD1

NASA Astrophysics Data System (ADS)

Under the Complete Brazilian Space Mission (MECB) project, the first Brazilian satellite SCDI was lofted on February 9, 1993 by a Pegasus rocket. This weather data collecting satellite was injected into a near-circular orbit of approximately 760 km altitude with an orbital inclination of 25 deg. The European Space Agency (ESA) kindly agreed to use their ground station facilities at Mas Palomas, Spain, to give tracking assistance to Brazil in the very first orbit of the satellite. However due to the failure of the clock in the launch vehicle, the Flight Mechanics group of INPE, Brazil, responsible for the flight dynamics software preparation and operation, had a great difficulty in determining the orbit at the injection point. This paper describes the difficulties faced by the group during that early phase, which critical decisions which had to be taken, how the hurdles were overcome, and how a very quick and good early orbit determination was achieved using the minimum data available.

Kuga, Helio K.; Kondapalli, Rama R.

1993-10-01

199

Precise Orbit Determination for the GEOSAT Follow-On Spacecraft

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

200

NASA Technical Reports Server (NTRS)

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

Escher, William J. D.

1992-01-01

201

Cryosat-2 precision orbit determination with Doris and satellite laser ranging

NASA Astrophysics Data System (ADS)

Cryosat-2 was successfully launched on April 8, 2010 to map the cryosphere with an advanced microwave altimeter system. The mission goal is to observe the freeboard of sea ice and the topography of ice sheets for a nominal period of 3 years. Precision orbit determination of Cryosat-2 relies on DORIS Doppler tracking and ground based satellite laser ranging. During this talk we will show preliminary results obtained by precision orbit determination. We will focus on the comparison of independently computed trajectories to those provided by the CNES to ESA's Cryosat-2 project, and we will use independent data acquired from Cryosat's SIRAL radar altimeter over ocean surfaces to assess orbit quality.

Visser, P. N.; Schrama, E. J.; Naeije, M.

2010-12-01

202

The M dwarf binary, Wolf 1062 (Gliese 748), has been observed with the Hubble Space Telescope (HST) Fine Guidance Sensor 3 in the transfer function scan mode to determine the apparent orbit. This is the first orbit defined fully and exclusively with HST, and is the most accurate definitive orbit for any resolved, noneclipsing system. The orbital period is 2.4490

Otto G. Franz; Todd J. Henry; Lawrence H. Wasserman; G. Fritz Benedict; Philip A. Ianna; J. Davy Kirkpatrick; Donald W. McCarthy Jr.; Arthur J. Bradley; Raynor L. Duncombe; Laurence W. Fredrick; Paul D. Hemenway; William H. Jefferys; Barbara E. McArthur; Edmund P. Nelan; Peter J. Shelus; Darrell B. Story; William F. van Altena; Arthur L. Whipple

1998-01-01

203

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

NASA Technical Reports Server (NTRS)

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

Hunter, J. A.

1979-01-01

204

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

205

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

NASA Technical Reports Server (NTRS)

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

Engelis, Theodossios

1987-01-01

206

A demonstration of high precision GPS orbit determination for geodetic applications

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

207

A high order method for orbital conjunctions analysis: Sensitivity to initial uncertainties

NASA Astrophysics Data System (ADS)

A high order method to quickly assess the effect that uncertainties produce on orbital conjunctions through a numerical high-fidelity propagator is presented. In particular, the dependency of time and distance of closest approach to initial uncertainties on position and velocity of both objects involved in a conjunction is studied. The approach relies on a numerical integration based on differential algebraic techniques and a high-order algorithm that expands the time and distance of closest approach in Taylor series with respect to relevant uncertainties. The modeled perturbations are atmospheric drag, using NRLMSISE-00 air density model, solar radiation pressure with shadow, third body perturbation using JPL's DE405 ephemeris, and EGM2008 gravity model. The polynomial approximation of the final position is used as an input to compute analytically the expansion of time and distance of closest approach. As a result, the analysis of a close encounter can be performed through fast, multiple evaluations of Taylor polynomials. Test cases with objects ranging from LEO to GEO regimes are considered to assess the performances and the accuracy of the proposed method.

Morselli, Alessandro; Armellin, Roberto; Di Lizia, Pierluigi; Bernelli Zazzera, Franco

2014-02-01

208

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

209

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

210

The values of the initial velocity of the meteoroids ejected from the parent bodies are small and as a result, the most of the young meteoroid streams have similar orbits to their parent bodies. Assuming that the members of the observed meteor stream evolved under the influence of gravitational perturbations mostly, Pittich [1991, Proceedings of the Conference on Dynamic of

R. Rudawska; T. J. Jopek; P. A. Dybczy?ski

2005-01-01

211

Orbit determination strategy and results for the Pioneer 10 Jupiter mission

NASA Technical Reports Server (NTRS)

Pioneer 10 is the first earth-based vehicle to encounter Jupiter and occult its moon, Io. In contributing to the success of the mission, the Orbit Determination Group evaluated the effects of the dominant error sources on the spacecraft's computed orbit and devised an encounter strategy minimizing the effects of these error sources. The encounter results indicated that: (1) errors in the satellite model played a very important role in the accuracy of the computed orbit, (2) encounter strategy was sound, (3) all mission objectives were met, and (4) Jupiter-Saturn mission for Pioneer 11 is within the navigation capability.

Wong, S. K.; Lubeley, A. J.

1974-01-01

212

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

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

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

2009-01-01

213

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

NASA Technical Reports Server (NTRS)

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

Shank, D.; Pajerski, R.

1986-01-01

214

Orbit and Gravity Determinations Using ROCSAT3\\/COSMIC GPS Data: Status 2004

The ROCSAT3\\/COSMIC (RC) mission is scheduled to be launched in late 2005 and contains a geodetic element in the mission. Each of the six satellites of RC is equipped with a POD GPS¡@antenna which yields data for precise orbit and gravity determinations. In view of the large number of satellites and orbital planes, simple satellite¡¦s simple geometry (cylindrical) and a

C. Hwang; C. Wang; L. Hwang; T. Lin; Y. Lee; L. Chang; S. Hsu

2004-01-01

215

Application of variance component estimation to precision orbit determination for ERS-2

The variance component estimation (VCE) method was applied to the precision orbit determination (POD) for ERS-2 satellite. Totally, 23 5-day-long maneuver-free arcs with 2 days overlap (when without orbit maneuver separation between the successive arcs) in the early three months of 1998 were computed using SLR and PRARE data. To inspect the effect of the VCE method on the POD

F. P. Zhang; C. Huang; C. G. Feng; X. J. Dong; X. H. Liao

2001-01-01

216

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

NASA Technical Reports Server (NTRS)

Orbit determination and prediction of the Fermi Gamma-ray Space Telescope trajectory is strongly impacted by the unpredictability and variability of atmospheric density and the 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.

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

2014-01-01

217

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

218

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

219

Orbit and attitude determination results during launch support operations for SBS-5

NASA Technical Reports Server (NTRS)

Presented are orbit and attitude determination results from the launch of Satellite Business Systems (SBS)-5 satellite on September 8, 1988 by Arianespace. SBS-5 is a (HS-376) spin stabilized spacecraft. The launch vehicle injected the spacecraft into a low inclination transfer orbit. Apogee motor firing (AMF) attitude was achieved with trim maneuvers. An apogee kick motor placed the spacecraft into drift orbit. Postburn, reorientation and spindown maneuvers were performed during the next 25 hours. The spacecraft was on-station 19 days later. The orbit and attitude were determined by both an extended Kalman filter and a weighted least squares batch processor. Although the orbit inclination was low and the launch was near equinox, post-AMF analysis indicated an attitude declination error of 0.034 deg., resulting in a saving of 8.5 pounds of fuel. The AMF velocity error was 0.4 percent below nominal. The post-AMF drift rate was determined with the filter only 2.5 hours after motor firing. The filter was used to monitor and retarget the reorientation to orbit normal in real time.

Hartman, K. R.; Iano, P. J.

1989-01-01

220

A review of GPS-based tracking techniques for TDRS orbit determination

NASA Technical Reports Server (NTRS)

This article evaluates two fundamentally different approaches to the Tracking and Data Relay Satellite (TDRS) orbit determination utilizing Global Positioning System (GPS) technology and GPS-related techniques. In the first, a GPS flight receiver is deployed on the TDRS. The TDRS ephemerides are determined using direct ranging to the GPS spacecraft, and no ground network is required. In the second approach, the TDRS's broadcast a suitable beacon signal, permitting the simultaneous tracking of GPS and Tracking and Data Relay Satellite System satellites by ground receivers. Both strategies can be designed to meet future operational requirements for TDRS-II orbit determination.

Haines, B. J.; Lichten, S. M.; Malla, R. P.; Wu, S.-C.

1993-01-01

221

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

222

Experimental study on the precise orbit determination of the BeiDou navigation satellite system.

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

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

2013-01-01

223

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

224

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

NASA Technical Reports Server (NTRS)

The Solar Dynamics Observatory (SDO) was launched on February 11, 2010 from Kennedy Space Center on an Atlas V launch vehicle into a geosynchronous transfer orbit. SDO carries a suite of three scientific instruments, whose observations are intended to promote a more complete understanding of the Sun and its effects on the Earth's environment. After a successful launch, separation, and initial Sun acquisition, the launch and flight operations teams dove into a commissioning campaign that included, among other things, checkout and calibration of the fine attitude sensors and checkout of the Kalman filter (KF) and the spacecraft s inertial pointing and science control modes. In addition, initial calibration of the science instruments was also accomplished. During that process of KF and controller checkout, several interesting observations were noticed and investigated. The SDO fine attitude sensors consist of one Adcole Digital Sun Sensor (DSS), two Galileo Avionica (GA) quaternion-output Star Trackers (STs), and three Kearfott Two-Axis Rate Assemblies (hereafter called inertial reference units, or IRUs). Initial checkout of the fine attitude sensors indicated that all sensors appeared to be functioning properly. Initial calibration maneuvers were planned and executed to update scale factors, drift rate biases, and alignments of the IRUs. After updating the IRU parameters, the KF was initialized and quickly reached convergence. Over the next few hours, it became apparent that there was an oscillation in the sensor residuals and the KF estimation of the IRU bias. A concentrated investigation ensued to determine the cause of the oscillations, their effect on mission requirements, and how to mitigate them. The ensuing analysis determined that the oscillations seen were, in fact, due to an oscillation in the IRU biases. The low frequencies of the oscillations passed through the KF, were well within the controller bandwidth, and therefore the spacecraft was actually following the oscillating biases, resulting in movement of the spacecraft on the order of plus or minus 20 arcsec. Though this level of error met the ACS attitude knowledge requirement of [35, 70, 70] arcsec, 3 sigma, the desire of the ACS and instrument teams was to remove as much of the oscillation as possible. The Kearfott IRUs have an internal temperature controller, designed to maintain the IRU temperature at a constant temperature of approximately 70 C, thus minimizing the change in the bias drift and scale factors of the mechanical gyros. During ground testing of the observatory, it was discovered that the 83-Hz control cycle of the IRU heaters put a tremendous amount of stress on the spacecraft battery. Analysis by the power systems team indicated that the constant charge/discharge on the battery due to the IRU thermal control cycle could potentially limit the life of the battery. After much analysis, the decision was made not to run the internal IRU heaters. Analysis of on orbit data revealed that the oscillations in the IRU bias had a connection to the temperature of the IRU; changes in IRU temperature resulted in changes in the amplitude and period of the IRU biases. Several mitigating solutions were investigated, the result of which was to tune the KF with larger IRU noise assumptions which allows the KF to follow and correct for the time-varying IRU biases.

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

2011-01-01

225

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

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

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

2013-02-01

226

NASA Astrophysics Data System (ADS)

Current SSA sensor tasking and scheduling is not centrally coordinated or optimized for either orbit determination quality or efficient use of sensor resources. By applying readily available capabilities for determining optimal tasking times and centrally generating de-conflicted schedules for all available sensors, both the quality of determined orbits (and thus situational awareness) and the use of sensor resources may be measurably improved. This paper provides an approach that is logically separated into two main sections. Part 1 focuses on the science of orbit determination based on tracking data and the approaches to tracking that result in improved orbit prediction quality (such as separating limited tracking passes in inertial space as much as possible). This part of the paper defines the goals for Part 2 of the paper which focuses on the details of an improved tasking and scheduling approach for sensor tasking. Centralized tasking and scheduling of sensor tracking assignments eliminates conflicting tasking requests up front and coordinates tasking to achieve (as much as possible within the physics of the problem and limited resources) the tracking goals defined in Part I. The effectivity of the proposed approach will be assessed based on improvements in the overall accuracy of the space catalog. Systems Tool Kit (STK) from Analytical Graphics and STK Scheduler from Orbit Logic are used for computations and to generate schedules for the existing and improved approaches.

Herz, A.; Stoner, F.

2013-09-01

227

Phase Function Determination in Support of Orbital Debris Size Estimation

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

228

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

229

NASA Technical Reports Server (NTRS)

Images produced by pinhole cameras using film sensitive to atomic oxygen provide information on the ratio of spacecraft orbital velocity to the most probable thermal speed of oxygen atoms, provided the spacecraft orientation is maintained stable relative to the orbital direction. Alternatively, 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.

Peters, Palmer N.; Gregory, John C.

1992-01-01

230

The orbit, atmospheric dynamics, and initial mass of the Park Forest meteorite

NASA Astrophysics Data System (ADS)

The fireball accompanying the Park Forest meteorite fall (L5) was recorded by ground-based videographers, satellite systems, infrasound, seismic, and acoustic instruments. This meteorite shower produced at least 18 kg of recovered fragments on the ground (Simon et al. 2004). By combining the satellite trajectory solution with precise ground-based video recording from a single site, we have measured the original entry velocity for the meteoroid to be 19.5 ± 0.3 km/s. The earliest video recording of the fireball was made near the altitude of 82 km. The slope of the trajectory was 29° from the vertical, with a radiant azimuth (astronomical) of 21° and a terminal height measured by infrared satellite systems of 18 km. The meteoroid's orbit has a relatively large semi-major axis of 2.53 ± 0.19 AU, large aphelion of 4.26 ± 0.38 AU, and low inclination. The fireball reached a peak absolute visual magnitude of -22, with three major framentation episodes at the altitudes of 37, 29, and 22 km. Acoustic recordings of the fireball airwave suggest that fragmentation was a dominant process in production of sound and that some major fragments from the fireball remained supersonic to heights as low as ˜10 km. Seismic and acoustic recordings show evidence of fragmentation at 42, 36, 29, and 17 km. Examination of implied energies/initial masses from all techniques (satellite optical, infrasound, seismic, modeling) leads us to conclude that the most probable initial mass was (11 ± 3) × 103 kg, corresponding to an original energy of ˜0.5 kt TNT (2.1 times 1012 J) and a diameter of 1.8 m. These values correspond to an integral bolometric efficiency of 7 ± 2%. Early fragmentation ram pressures of <1 MPa and major fragmentations occurring with ram pressures of 2-5 MPa suggest that meter-class stony near-Earth asteroids (NEAs) have tensile strengths more than an order of magnitude lower than have been measured for ordinary chondrites. One implication of this observation is that the rotation period for small, fast-rotating NEAs is likely to be >30 seconds.

Brown, P.; Pack, D.; Edwards, W. N.; Revelle, D. O.; Yoo, B. B.; Spalding, R. E.; Tagliaferri, E.

2004-11-01

231

Determination of binary asteroid orbits with a genetic-based algorithm

NASA Astrophysics Data System (ADS)

Aims: Over the past decade, discoveries of multiple and binary asteroid systems have played a significant role in our general understanding of small solar system bodies. Direct observations of satellites of asteroids are rare and difficult since they require the use of already over-subscribed facilities such as adaptive optics (AO) on large 8-10 m class telescopes and the Hubble Space Telescope (HST). The scarcity of data and the long temporal baseline of observations (up to 10 years) significantly complicate the determination of the mutual orbits of these systems. Methods: We implemented a new approach for determining the mutual orbits of directly-imaged multiple asteroids using a genetic-based algorithm. This approach was applied to several known binary asteroid systems (22 Kalliope, 3749 Balam, and 50 000 Quaoar) observed with AO systems and HST. This statistical method is fast enough to permit the search for an orbital solution across a large parameter space and without a priori information about the mutual orbit. Results: From 10 years of observation, we derived an orbital solution for Linus, companion of (22) Kalliope, with an accuracy close to the astrometric limit provided by the AO observations, assuming a purely Keplerian orbit. A search for non-Keplerian orbit confirmed that a J2 ~ 0 is the best-fitting solution. We show that the precession of the nodes could be detected without ambiguity, implying that Kalliope's primary may have an inhomogeneous internal structure. HST astrometric observations of Weywot, companion of the trans-Neptunian object (50 000) Quaoar, were used to derive its mass and its bulk density, which appears to be higher than the density of other TNOs. Finally, we derived a bundle of orbital solutions for (3749) Balam, with equally good fits, from the limited set of astrometric positions. They provide a realistic density between 1.3 and 3.7 g/cm3 for this S-type asteroid.

Vachier, F.; Berthier, J.; Marchis, F.

2012-07-01

232

The Landsat Data Continuity Mission (named Landsat 8 after on-orbit initialization and verifica-

rocket. As with previous partnerships, this collabo- ration between the U.S. Geological Survey (USGS responsible for the operations of the mission, including: health and safety of the space- craft; orbital

233

NASA Technical Reports Server (NTRS)

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 Orbit Determination Automation System (ODAS) was designed, developed, and implemented as a prototype system to automate orbit determination (OD) and orbit quality assurance (QA) functions performed by orbit operations. Based on a machine-resident generic schedule and predetermined mission-dependent QA criteria, ODAS autonomously activates an interface with the existing trajectory determination system using a batch least-squares differential correction algorithm to perform the basic OD functions. The computational parameters determined during the OD are processed to make computerized decisions regarding QA, and a controlled recovery process isactivated when the criteria are not satisfied. The complete cycle is autonomous and continuous. ODAS was extensively tested for performance under conditions resembling actual operational conditions and found to be effective and reliable for extended autonomous OD. Details of the system structure and function are discussed, and test results are presented.

Mardirossian, H.; Heuerman, K.; Beri, A.; Samii, M. V.; Doll, C. E.

1989-01-01

234

Effect of ITRF2000 on TOPEX/POSEIDON Orbit Determination and Mean Sea Level Time Series

NASA Astrophysics Data System (ADS)

The precision orbits produced by NASA for the TOPEX/POSEIDON altimeter satellite are based on a set of SLR and DORIS station coordinates determined in 1995 (CSR95L01 and CSR95D02). However, it is clear that this terrestrial reference system needs to be updated. In particular, the DORIS station velocities in CSR95D02 are not sufficiently well determined to accurately propagate the positions into the current years, much less into the Jason-1 follow-on mission. The ITRF2000 reference frame is a new solution for the SLR, DORIS and GPS tracking stations which is a significant improvement over previous solutions. The concern is that artificial trends can be introduced into the sea level observations from changes or errors in the reference system used for orbit determination. ITRF97 has a significant offset (2 cm) and drift (2 mm/yr) relative to the CSR system, so it was not adopted for the NASA orbit production. ITRF2000 has adopted the SLR determination of the terrestrial origin, which has substantially removed this offset and drift. By adopting ITRF2000, NASA and CNES should be able to adopt the same terrestrial reference frame for the transition from TOPEX/POSEIDON to Jason-1. The level of backward compatibility with the CSR95L01/D02 system is examined to determine if any significant artifacts in the sea level time series are introduced in the sea level time series based on the NASA orbits.

Ries, J. C.; Chambers, D. P.; Choi, K.; Eanes, R. J.

2001-12-01

235

NASA Technical Reports Server (NTRS)

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 Orbit Determination Automation System (ODAS) was designed, developed, and implemented as a prototype system to automate orbit determination (OD) and orbit quality assurance (QA) functions performed by orbit operations. Based on a machine-resident generic schedule and predetermined mission-dependent QA criteria, ODAS autonomously activates an interface with the existing trajectory determination system using a batch least-squares differential correction algorithm to perform the basic OD functions. The computational parameters determined during the OD are processed to make computerized decisions regarding QA, and a controlled recovery process is activated when the criteria are not satisfied. The complete cycle is autonomous and continuous. ODAS was extensively tested for performance under conditions resembling actual operational conditions and found to be effective and reliable for extended autonomous OD. Details of the system structure and function are discussed, and test results are presented.

Mardirossian, H.; Beri, A. C.; Doll, C. E.

1990-01-01

236

NASA Technical Reports Server (NTRS)

A method to determine satellite orbits using tracking data and a priori gravitational field is described. The a priori constraint on the orbit dynamics is determined by the covariance matrix of the spherical harmonic coefficients for the gravity model, so that the optimal combination of the measurements and gravitational field is achieved. A set of bin parameters is introduced to represent the perturbation of the gravitational field on the position of the satellite orbit. The covariance matrix of a conventional gravity model is transformed into that for the bin parameters by the variational partial derivatives. The covariance matrices of the bin parameters and the epoch state are combined to form the covariance matrix of the satellite positions at the measurement times. The combined matrix is used as the a priori information to estimate the satellite positions with measurements.

Wu, Jiun-Tsong; Wu, Sien-Chong

1992-01-01

237

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

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

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

2014-01-01

238

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

239

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

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

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

2014-01-01

240

NASA Astrophysics Data System (ADS)

Autonomous orbit determination of navigation constellation based on cross-link range is studied in this paper. Considering the characteristics of near-circular orbits of navigation satellites and onboard computing ability, a set of nonsingular orbital elements are selected as state variables. Since the state variables are slow variables on the whole, maximum integration step used in the proposed algorithm, it can expand to 60 minutes, which is much longer than that of other methods. Meanwhile, instead of solving high-order variable coefficient linear differential equations using numerical method, the state transition matrix can directly refer to the result of analytical method. These two improved aspects can reduce the calculation burden of onboard computers obviously. And then the improved extended Kalman filter (EKF) is utilized to estimate the satellite position and velocity vectors of the constellation by fusing cross-link range data and satellite orbital dynamic information. Simulation results show that the proposed algorithm is feasible to improve the calculation efficiency while the orbit determination accuracy is satisfied, which is very important for realtime onboard data processing.

Li, Hai-Sheng; Wang, Hai-Hong; Xu, Bo

2009-12-01

241

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

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

Morbidelli, Alessandro

242

33LRO Determines Lunar Cratering History The Lunar Reconnaissance Orbiter used millions of measurements of the lunar surface to establish the history of cratering on the surface. Problem 1 in kilometers/mm. Problem 2 - How many craters can you count that are larger than 70 kilometers in diameter

243

NASA Technical Reports Server (NTRS)

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

Daly, J. K.

1974-01-01

244

TOPEX orbit determination using GPS signals plus a sidetone ranging system

NASA Technical Reports Server (NTRS)

The GPS orbit determination was studied to see how well the radial coordinate for altimeter satellites such as TOPEX could be found by on board measurements of GPS signals, including the reconstructed carrier phase. The inclusion on altimeter satellites of an additional high accuracy tracking system is recommended. It is suggested that a sidetone ranging system is used in conjunction with TRANET 2 beacons.

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

1982-01-01

245

Unbiased orbit determination for the next generation asteroid\\/comet surveys

In the next generation surveys, the discovery of moving objects can be successful only if an observation strategy and the identication\\/orbit determination procedure are appropriate for the diverse apparent motions of the target sub-populations. The observations must accurately measure the displacement over a short interval of time; observations believed to belong to the same object have to be connected into

A. Milani; G. F. Gronchi; Z. Kne; M. E. Sansaturio; O. Arratia; L. Denneau; T. Grav; J. Heasley; R. Jedicke; J. Kubica

2005-01-01

246

Unbiased orbit determination for the next generation asteroid\\/comet surveys

In the next generation surveys, the discovery of moving objects can be successful only if an observation strategy and the identification\\/orbit determination procedure are appropriate for the diverse apparent motions of the target sub-populations. The observations must accurately measure the displacement over a short interval of time; observations believed to belong to the same object have to be connected into

A. Milani; G. F. Gronchi; Z. Knezevic; M. E. Sansaturio; O. Arratia; L. Denneau; T. Grav; J. Heasley; R. Jedicke; J. Kubica

2006-01-01

247

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

Psiaki, Mark L.

248

NASA Astrophysics Data System (ADS)

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

Shefer, V. A.

2011-07-01

249

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

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

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

2002-01-01

250

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

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

F. Tamburini; B. Thidé; A. Sponselli

2012-01-16

251

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

252

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

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

253

20 CFR 418.1320 - What is the effect of an initial determination?

Code of Federal Regulations, 2010 CFR

An initial determination is binding unless you request a reconsideration within the time period described in §§ 404.909 and 404.911 of this chapter or we revise the initial determination or issue a new initial...

2010-04-01

254

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

255

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

NASA Technical Reports Server (NTRS)

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 is clearly superior, the reduced-dynamic technique appreciably improves the orbit accuracy. Guidelines for selecting a near-optimum weighting for the combination are given. Sensitivity to suboptimal weighting is assessed.

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

1988-01-01

256

NASA Technical Reports Server (NTRS)

Accurate orbit determination and the recovery of geophysical parameters are presently attempted via methodologies which use differenced height measurements at the points where the ground tracks of the altimetric satellite orbits intersect. Such 'crossover measurements' could significantly improve the earth's gravity field model. Attention is given to a novel technique employing crossover measurements from two satellites carrying altimeter instruments; this method can observe zonal harmonics of the earth's geopotential which are weakly observed through single-satellite crossovers. This dual-satellite crossover technique will be applicable to data from such future oceanographic satellites as ERS-1.

Shum, C. K.; Schutz, B. E.; Tapley, B. D.; Zhang, B. H.

1990-01-01

257

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

258

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

259

NASA Astrophysics Data System (ADS)

The atmospheric mass density of the upper atmosphere from the spherical Starlette satellite's Precise Orbit Determination is first derived with Satellite Laser Ranging measurements at 815 to 1115 km during strong solar and geomagnetic activities. Starlette's orbit is determined using the improved orbit determination techniques combining optimum parameters with a precise empirical drag application to a gravity field. MSIS-86 and NRLMSISE-00 atmospheric density models are compared with the Starlette drag-derived atmospheric density of the upper atmosphere. It is found that the variation in the Starlette's drag coefficient above 800 km corresponds well with the level of geomagnetic activity. This represents that the satellite orbit is mainly perturbed by the Joule heating from geomagnetic activity at the upper atmosphere. This result concludes that MSIS empirical models strongly underestimate the mass density of the upper atmosphere as compared to the Starlette drag-derived atmospheric density during the geomagnetic storms. We suggest that the atmospheric density models should be analyzed with higher altitude acceleration data for a better understanding of long-term solar and geomagnetic effects.

Jeon, H. S.; Cho, S.; Kwak, Y. S.; Chung, J. K.; Park, J. U.; Lee, D. K.; Kuzmicz-Cieslak, M.

2011-04-01

260

TOPEX/POSEIDON operational orbit determination results using global positioning satellites

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

261

N-observations and radar orbits

NASA Astrophysics Data System (ADS)

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

Kristensen, Leif Kahl

2007-07-01

262

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

NASA Astrophysics Data System (ADS)

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 40 cm 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 "Observatori Astronòmic de Mallorca" (OAM, located in Mallorca, Spain). The baseline between the sites is about 1000 km. Three second long, 1 min apart exposures were simultaneously taken in sidereal tracking mode, looking at the same arcs of the geosynchronous ring. The size of the fields of view allowed to see a few satellites in two successive frames from both sites. The Lambert theorem has been exploited to determine the orbits, averaging the data with the least square method in the case that more than 2 points were available. Of course, the longer the time interval between the positions, the lower the effect of measuring errors. Nevertheless, the only way to have quite distant points would be tracking the satellite, but following-up is typically time demanding thus not suitable for a surveillance campaign, hence not very interesting from a practical standpoint. 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 solutions based on the measurements fitted with the least squares method, with the circular orbit assumption results, with the one-site complete orbit determination and with the TLEs.

Porfilio, Manfredi; Piergentili, Fabrizio; Graziani, Filippo

2006-01-01

263

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

264

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

NASA Technical Reports Server (NTRS)

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 stations, the 1300 km altitude of a user satellite (TOPEX) can be determined to 5 cm in 2 hours of tracking. Examination is made of the effects of employing fewer ground stations, of different solution strategies, and of introducing fictitious thrust parameters to alleviate the geopotential modeling error which is one of the major error sources.

Wu, S. C.; Ondrasik, V. J.

1982-01-01

265

20 CFR 259.1 - Initial determinations with respect to employer and employee status.

Code of Federal Regulations, 2010 CFR

...determinations with respect to employer and employee status. 259.1 Section 259.1 Employees' Benefits...FROM INITIAL DETERMINATIONS WITH RESPECT TO EMPLOYER STATUS AND EMPLOYEE STATUS § 259.1 Initial determinations with...

2010-04-01

266

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

267

NASA Astrophysics Data System (ADS)

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.

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

268

NASA Astrophysics Data System (ADS)

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.

Lei, Ning; Chen, Xuexia; Xiong, Xiaoxiong

2014-09-01

269

NASA Astrophysics Data System (ADS)

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.

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

270

An initial comparative assessment of orbital and terrestrial central power systems

NASA Technical Reports Server (NTRS)

A silicon photovoltaic orbital power system, which is constructed from an earth source of materials, is compared to likely terrestrial (fossil, nuclear, and solar) approaches to central power generation around the year 2000. A total social framework is used that considers not only the projection of commercial economics (direct or in internal costs), but also considers external impacts such as research and development investment, health impacts, resource requirements, environment effects, and other social costs.

Caputo, R.

1977-01-01

271

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

272

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

M. Porfilio; F. Piergentili; F. Graziani

2004-01-01

273

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

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

Manfredi Porfilio; Fabrizio Piergentili; Filippo Graziani

2006-01-01

274

A demonstration of unified TDRS/GPS tracking and orbit determination

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

275

Precise orbit determination of Multi-GNSS constellation including GPS GLONASS BDS and GALIEO

NASA Astrophysics Data System (ADS)

In addition to the existing American global positioning system (GPS) and the Russian global navigation satellite system (GLONASS), the new generation of GNSS is emerging and developing, such as the Chinese BeiDou satellite navigation system (BDS) and the European GALILEO system. Multi-constellation is expected to contribute to more accurate and reliable positioning and navigation service. However, the application of multi-constellation challenges the traditional precise orbit determination (POD) strategy that was designed usually for single constellation. In this contribution, we exploit a more rigorous multi-constellation POD strategy for the ongoing IGS multi-GNSS experiment (MGEX) where the common parameters are identical for each system, and the frequency- and system-specified parameters are employed to account for the inter-frequency and inter-system biases. Since the authorized BDS attitude model is not yet released, different BDS attitude model are implemented and their impact on orbit accuracy are studied. The proposed POD strategy was implemented in the PANDA (Position and Navigation Data Analyst) software and can process observations from GPS, GLONASS, BDS and GALILEO together. The strategy is evaluated with the multi-constellation observations from about 90 MGEX stations and BDS observations from the BeiDou experimental tracking network (BETN) of Wuhan University (WHU). Of all the MGEX stations, 28 stations record BDS observation, and about 80 stations record GALILEO observations. All these data were processed together in our software, resulting in the multi-constellation POD solutions. We assessed the orbit accuracy for GPS and GLONASS by comparing our solutions with the IGS final orbit, and for BDS and GALILEO by overlapping our daily orbit solution. The stability of inter-frequency bias of GLONASS and inter-system biases w.r.t. GPS for GLONASS, BDS and GALILEO were investigated. At last, we carried out precise point positioning (PPP) using the multi-constellation POD orbit and clock products, and analyzed the contribution of these POD products to PPP. Keywords: Multi-GNSS, Precise Orbit Determination, Inter-frequency bias, Inter-system bias, Precise Point Positioning

Dai, Xiaolei

2014-05-01

276

NASA Technical Reports Server (NTRS)

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

Peters, Palmer N.; Gregory, John C.

1991-01-01

277

Initial effects of nuclear weapon x-radiation on the LAMPSHADE orbital debris satellite shield

One-dimensional thermal-hydrodynamic calculations have been carried out to estimate the response of the lead bumper plate and tantalum liquidation screen of the LAMPSHADE orbital debris satellite shield. The mass loss fraction in the solid, liquid, and vapor phases as a function of time after irradiation for several typical incident x-ray spectra fluences were calculated using the PUFF-TFT code. The material losses did not exceed 2% and fracture and spallation were confined to the surface region with no apparent reduction in the performance of these components against incident debris. 4 refs., 5 figs., 3 tabs.

Smith, M.S.; Santoro, R.T.

1989-09-01

278

An initial comparative assessment of orbital and terrestrial central power systems

NASA Technical Reports Server (NTRS)

Orbital solar power plants, which beam power to earth by microwave, are compared with ground-based solar and conventional baseload power plants. Candidate systems were identified for three types of plants and the selected plant designs were then compared on the basis of economic and social costs. The representative types of plant selected for the comparison are: light water nuclear reactor; turbines using low BTU gas from coal; central receiver with steam turbo-electric conversion and thermal storage; silicon photovoltaic power plant without tracking and including solar concentration and redox battery storage; and silicon photovoltaics.

Caputo, R.

1977-01-01

279

NASA Technical Reports Server (NTRS)

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.

Marr, Greg C.

2003-01-01

280

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

281

Narrow bandgap conjugated polymers in combination with fullerene acceptors are under intense investigation in the field of organic photovoltaics (OPVs). The open circuit voltage, and thereby the power conversion efficiency, of the devices is related to the offset of the frontier orbital energy levels of the donor and acceptor components, which are widely determined by cyclic voltammetry. Inconsistencies have appeared in the use of the ferrocenium/ferrocene (Fc + /Fc) redox couple, as well as the values used for the absolute potentials of standard electrodes, which can complicate the comparison of materials properties and determination of structure/property relationships. PMID:21462372

Cardona, Claudia M; Li, Wei; Kaifer, Angel E; Stockdale, David; Bazan, Guillermo C

2011-05-24

282

Federal Register 2010, 2011, 2012, 2013, 2014

...Notice of Initial Determination Revising the List of Products Requiring Federal Contractor...initial determination proposes to revise the list required by Executive Order No. 13126...Procedural Guidelines for the Maintenance of the List of Products Requiring Federal...

2011-10-04

283

Code of Federal Regulations, 2010 CFR

...determinations with respect to employer or employee status. 259.3 Section 259.3 Employees' Benefits...FROM INITIAL DETERMINATIONS WITH RESPECT TO EMPLOYER STATUS AND EMPLOYEE STATUS § 259.3 Reconsideration of initial...

2010-04-01

284

NASA Astrophysics Data System (ADS)

The purpose of this research is to improve the knowledge of the physical properties of orbital debris, specifically the material type. Combining the use of the fast-tracking United States Air Force Research Laboratory (AFRL) telescopes with a common astronomical technique, spectroscopy, and NASA resources was a natural step toward determining the material type of orbiting objects remotely. Currently operating at the AFRL Maui Optical Site (AMOS) is a 1.6-meter telescope designed to track fast moving objects like those found in lower Earth orbit (LEO). Using the spectral range of 0.4 - 0.9 microns (4000 - 9000 angstroms), researchers can separate materials into classification ranges. Within the above range, aluminum, paints, plastics, and other metals have different absorption features as well as slopes in their respective spectra. The spectrograph used on this telescope yields a three-angstrom resolution; large enough to see smaller features mentioned and thus determine the material type of the object. The results of the NASA AMOS Spectral Study (NASS) are presented herein.

Jorgensen, Kira; Africano, John L.; Stansbery, Eugene G.; Kervin, Paul W.; Hamada, Kris M.; Sydney, Paul F.

2001-12-01

285

Orbit Determination and Sea Level Rise: How Astrodynamics Informs Us About the Climate

NASA Astrophysics Data System (ADS)

Advancements in satellite tracking systems, Earth-gravity field models, and the definition of the terrestrial reference frame have led to significant improvements in the orbit determination for low Earth orbit satellites over the last few decades. These improvements have allowed climate-driven variations in the hydrosphere to be detected for the first time. The monitoring of global mean sea level variations was not originally a goal of satellite altimeter missions such as TOPEX/Poseidon, but now they are measured with an accuracy of ˜4 mm every 10 days because of improvements in the orbit determination (radial component ˜1 cm) and other advances. Similarly, satellite gravity missions such as GRACE have allowed time-variable gravity to become a major scientific objective, with monthly estimates of changes in global ocean mass with an accuracy of 2 mm. Taking advantage of these measurements for climate change studies will require multidecadal time-series using multiple satellite missions that may be tracked by different techniques and methods as technology evolves. For this reason, maintenance and improvement of the terrestrial reference frame is a critical component of an overall plan to monitor the Earth's water reservoirs from space.

Nerem, R. S.; Chambers, D. P.

2009-10-01

286

The application of Encke's method to long arc orbit determination solutions

NASA Technical Reports Server (NTRS)

The Laser Geodynamics Satellite (LAGEOS) was launched on May 4, 1976 to provide geophysical measurements by means of laser ranging techniques. To date, over twelve years of laser range measurements have been collected from various tracking stations located around the world. Laser range measurements to LAGEOS have contributed to studies of earth rotation, plate tectonics, global baseline, and the gravity field as well as many other areas. Some of these studies are based upon the determination of a single, continuous orbit for LAGEOS for time spans on the order of several years. Current studies at the University of Texas Center for Space Research include the precision orbit determination of LAGEOS for arc lengths of up to 12.8 years which represents over 31,000 orbital revolutions. These long arc studies have led to the implementation of Encke's method to improve the convergence of the batch filter while reducing numerical integration errors. While the technique has been successfully applied to arc lengths of up to 12.8 years, the results presented focus on the solution of a six-year arc.

Lundberg, J. B.; Schutz, B. E.; Fields, R. K.; Watkins, M. M.

1990-01-01

287

NASA Astrophysics Data System (ADS)

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

Paredes-Gil, Katherine; Jaque, Pablo

2015-01-01

288

Orbital Pseudotumor: Uncommon Initial Presentation of IgG4-Related Disease

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.

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

2015-01-01

289

GPS-based orbit determination and point positioning under selective availability

NASA Technical Reports Server (NTRS)

Selective availability (SA) degrades the positioning accuracy for nondifferential users of the GPS Standard Positioning Service (SPS). The often quoted SPS accuracy available under normal conditions is 100 m 2DRMS. In the absence of more specific information, many prospective SPS users adopt the 100 m value in their planning, which exaggerates the error in many cases. SA error is examined for point positioning and dynamic orbit determination for an orbiting user. To minimize SA error, nondifferential users have several options: expand their field of view; observe as many GPS satellites as possible; smooth the error over time; and employ precise GPS ephemerides computed independently, as by NASA and the NGS, rather than the broadcast ephemeris. Simulations show that 3D point position error can be kept to 30 m, and this can be smoothed to 3 m in a few hours.

Bar-Sever, Yoaz E.; Yunck, Thomas P.; Wu, Sien-Chong

1990-01-01

290

11 CFR 9033.10 - Procedures for initial and final determinations.

Code of Federal Regulations, 2010 CFR

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

2010-01-01

291

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

George Blyholder; Michael Lawless

1990-01-01

292

20 CFR 418.1310 - When may you request that we make a new initial determination?

Code of Federal Regulations, 2010 CFR

... false When may you request that we make a new initial determination? 418.1310...418.1310 When may you request that we make a new initial determination? (a) You may request that we make a new initial determination in the...

2010-04-01

293

NASA Astrophysics Data System (ADS)

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

Shefer, V. A.

2013-12-01

294

NASA Astrophysics Data System (ADS)

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

Shoji, Mitsuo; Yoshioka, Yasunori; Yamaguchi, Kizashi

2014-07-01

295

NASA Technical Reports Server (NTRS)

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

Chato, David J.

1991-01-01

296

NASA Technical Reports Server (NTRS)

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.

Lyons, Frankel

2013-01-01

297

Representation of Probability Density Functions from Orbit Determination using the Particle Filter

NASA Technical Reports Server (NTRS)

Statistical orbit determination enables us to obtain estimates of the state and the statistical information of its region of uncertainty. In order to obtain an accurate representation of the probability density function (PDF) that incorporates higher order statistical information, we propose the use of nonlinear estimation methods such as the Particle Filter. The Particle Filter (PF) is capable of providing a PDF representation of the state estimates whose accuracy is dependent on the number of particles or samples used. For this method to be applicable to real case scenarios, we need a way of accurately representing the PDF in a compressed manner with little information loss. Hence we propose using the Independent Component Analysis (ICA) as a non-Gaussian dimensional reduction method that is capable of maintaining higher order statistical information obtained using the PF. Methods such as the Principal Component Analysis (PCA) are based on utilizing up to second order statistics, hence will not suffice in maintaining maximum information content. Both the PCA and the ICA are applied to two scenarios that involve a highly eccentric orbit with a lower apriori uncertainty covariance and a less eccentric orbit with a higher a priori uncertainty covariance, to illustrate the capability of the ICA in relation to the PCA.

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

2012-01-01

298

20 CFR 410.621 - Effect of initial determination.

Code of Federal Regulations, 2010 CFR

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

2010-04-01

299

NASA Astrophysics Data System (ADS)

The precise knowledge of the ephemerides of the geostationary satellites is a key point in mission control for the satellite control agencies both for planning manoeuvres and for checking their results. The major goal of the PASAGE project (Astrometric Positioning of Geostationary Satellites) is to use earth-based astrometric observations for obtaining precise ephemerides and the subsequent orbit determination. In order to carry out this special ground-based astrometric application, we have developed special algorithms and techniques that make it possible for us to achieve accuracies of a few tenths of an arc second in the geostationary satellite apparent topocentric positions, even from places with high light pollution.

Montojo, F. J.; López Moratalla, T.; Abad, C.; Muiños, J. L.

2008-12-01

300

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

Munoz, Douglas Perry

301

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

302

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

303

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

NASA Technical Reports Server (NTRS)

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

Lusignan, Bruce; Sivalingam, Shivan

1999-01-01

304

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

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

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

2011-01-01

305

Accurate Determination of Comet and Asteroid Orbits Leading to Collision With Earth

NASA Technical Reports Server (NTRS)

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.

Roithmayr, Carlos M.; Kay-Bunnell, Linda; Mazanek, Daniel D.; Kumar, Renjith R.; Seywald, Hans; Hausman, Matthew A.

2005-01-01

306

24 CFR 599.301 - Initial determination of threshold requirements.

Code of Federal Regulations, 2010 CFR

... (a) Two threshold requirements. Before rating and ranking an application, HUD will review it to determine if the application...Failure to meet threshold requirements —(1) No rating or ranking. An application that does not meet both of the...

2010-04-01

307

24 CFR 599.301 - Initial determination of threshold requirements.

Code of Federal Regulations, 2011 CFR

... (a) Two threshold requirements. Before rating and ranking an application, HUD will review it to determine if the application...Failure to meet threshold requirements —(1) No rating or ranking. An application that does not meet both of the...

2011-04-01

308

24 CFR 599.301 - Initial determination of threshold requirements.

Code of Federal Regulations, 2014 CFR

... (a) Two threshold requirements. Before rating and ranking an application, HUD will review it to determine if the application...Failure to meet threshold requirements —(1) No rating or ranking. An application that does not meet both of the...

2014-04-01

309

NASA Astrophysics Data System (ADS)

With the precise GPS ephemeris and clock error available, the iono- spheric delay is left as the dominant error source in the single-frequency GPS data. Thus, the removal of ionospheric effects is a ma jor prerequisite for an improved orbit reconstruction of LEO satellites based on the single-frequency GPS data. In this paper, the use of Global Ionospheric Maps (GIM) in kine- matic and dynamic orbit determinations for LEO satellites with single-frequency GPS pseudorange measurements is discussed first, and then, estimating the iono- spheric scale factor to remove the ionospheric effects from the C/A-code pseu- dorange measurements for both kinematic and dynamic orbit determinations is addressed. As it is known that the ionospheric delay of space-borne GPS sig- nals is strongly dependent on the orbit altitudes of LEO satellites, we select the real C/A-code pseudorange measurement data of the CHAMP, GRACE, TerraSAR-X and SAC-C satellites with altitudes between 300 km and 800 km as sample data in this paper. It is demonstrated that the approach to eliminating ionospheric effects in C/A-code pseudorange measurements by estimating the ionospheric scale factor is highly effective. Employing this approach, the accu- racy of both kinematic and dynamic orbits can be improved notably. Among those five LEO satellites, CHAMP with the lowest orbit altitude has the most remarkable improvements in orbit accuracy, which are 55.6% and 47.6% for kine- matic and dynamic orbits, respectively. SAC-C with the highest orbit altitude has the least improvements in orbit accuracy accordingly, which are 47.8% and 38.2%, respectively.

Peng, Dong-ju; Wu, Bin

2012-10-01

310

NASA Astrophysics Data System (ADS)

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

Shefer, V. A.

2009-11-01

311

NASA Technical Reports Server (NTRS)

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. [1], 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.

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

2012-01-01

312

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

313

GPS-Based Precision Orbit Determination for a New Era of Altimeter Satellites: Jason-1 and ICESat

NASA Technical Reports Server (NTRS)

Accurate positioning of the satellite center of mass is necessary in meeting an altimeter mission's science goals. The fundamental science observation is an altimetric derived topographic height. Errors in positioning the satellite's center of mass directly impact this fundamental observation. Therefore, orbit error is a critical Component in the error budget of altimeter satellites. With the launch of the Jason-1 radar altimeter (Dec. 2001) and the ICESat laser altimeter (Jan. 2003) a new era of satellite altimetry has begun. Both missions pose several challenges for precision orbit determination (POD). The Jason-1 radial orbit accuracy goal is 1 cm, while ICESat (600 km) at a much lower altitude than Jason-1 (1300 km), has a radial orbit accuracy requirement of less than 5 cm. Fortunately, Jason-1 and ICESat POD can rely on near continuous tracking data from the dual frequency codeless BlackJack GPS receiver and Satellite Laser Ranging. Analysis of current GPS-based solution performance indicates the l-cm radial orbit accuracy goal is being met for Jason-1, while radial orbit accuracy for ICESat is well below the 54x1 mission requirement. A brief overview of the GPS precision orbit determination methodology and results for both Jason-1 and ICESat are presented.

Luthcke, Scott B.; Rowlands, David D.; Lemoine, Frank G.; Zelensky, Nikita P.; Williams, Teresa A.

2003-01-01

314

Precise Orbit Determination of LAGEOS satellites: results on fundamental physics and perspectives

NASA Astrophysics Data System (ADS)

The LAGEOS satellites, launched for geodynamics and geophysics purposes, are offering also an outstanding test bench to fundamental physics. Indeed, their physical characteristics, as well as those of their orbits, and the availability of high--quality tracking data provided by the International Laser Ranging Service, allow for precise tests of gravitational theories. In this talk recent work on data analysis will be presented. A fairly large amount of LAGEOS and LAGEOS II Satellite Laser Ranging data has been analyzed with NASA/GSFC Geodyn II software, using a set of dedicated models for satellite dynamics, and the related post--fit residuals have been analyzed. In particular, general relativistic effects leave peculiar imprint on nodal longitude, argument of perigee and inclination behaviour, which have been used to obtain precise estimates of the related parameters. The most precise --- as today --- estimate of the effects on argument of perigee has been obtained, providing a direct measurement of the relativistic ``Schwarzschild'' precession in the field of the Earth. At the same time the constraints on a non--Newtonian (i.e. Yukawa--type) gravitational dynamics have been improved. The measurement error budget will be discussed, emphasizing the role of gravitational and, especially, of non--gravitational forces modeling on the overall precise orbit determination quality, as well as on future new measurements and constraints of the gravitational interaction.

Peron, Roberto; Lucchesi, David

2012-07-01

315

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

316

NASA Astrophysics Data System (ADS)

SLR Satellite Laser Ranging technique plays a key role in earth sciences The global SLR network has evolved into a powerful source of data for studies of the solid Earth and its ocean and atmospheric systems It is the most accurate space geodetic technique currently available to determine the geocentric position of an Earth satellite The SLR data processing work has been done in China since early 1980s and contributed to the solution of the position and velocity of global station network and earth orientation parameters in the following years Since 2004 GEODYN package has been introduced into Shanghai Astronomical Observatory SHAO of CAS for satellite POD data analysis As a developing and initial work of using this powerful software at SHAO in this paper the multi-SLR satellites observation data are processed simultaneously The orbit determination and earth orientation parameters solution are done from tracking data of multi-satellites Weighting methods are tested for the solution from each separate satellite The obtained results computed from above procedure are compared with the result from IERS standard value for some time span In addition the result computed from single satellite tracking data is also given as an example to show the advantage of the technique of multi-satellites data processing Additionally the time variation of low degree coefficients of earth gravity field in several years span is estimated the physical background of the result is analyzed and compared with the result of other literatures

Jianguo, Yan; Jingsong, Ping; Fei, Li

317

NASA Technical Reports Server (NTRS)

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.

Luthcke, Scott B.; Zelensky, N. P.; Rowlands, D. D.; Lemoine, F. G.; Chinn, D. S.; Williams, T. A.

2002-01-01

318

NASA Technical Reports Server (NTRS)

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.

Luthcke, S. B.; Zelensky, N. P.; Lemoine, Frank G.; Chinn, D. S.; Williams, T. A.

2002-01-01

319

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

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

320

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

P. Lejba; S. Schillak; E. Wnuk

2007-01-01

321

Federal Register 2010, 2011, 2012, 2013, 2014

...Investigation No. 337-TA-809] Certain Devices for Mobile Data Communication; Determination Not To Review an Initial Determination...States after importation of certain devices for mobile data communication by reason of infringement of certain...

2012-11-19

322

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

323

NASA Astrophysics Data System (ADS)

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.

Song, Young-Joo; Ahn, Sang-il; Sim, Eun-Sup

2014-09-01

324

NASA Astrophysics Data System (ADS)

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 the 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 the 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 online. In particular, directly imaged planets are promising targets because repeated spectral and photometric measurements, which are required to determine moon orbit direction, could also be conducted with the primary interest of characterizing the planet itself.

Lewis, Karen M.; Fujii, Yuka

2014-08-01

325

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

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

Cleveland, Durand Ennis

1972-01-01

326

NASA Astrophysics Data System (ADS)

With the availability of precise GPS ephemeris and clock solution, the ionospheric range delay is left as the dominant error sources in the post-processing of space-borne GPS data from single-frequency receivers. Thus, the removal of ionospheric effects is a major prerequisite for an improved orbit reconstruction of LEO satellites equipped with low cost single-frequency GPS receivers. In this paper, the use of Global Ionospheric Maps (GIM) in kinematic and dynamic orbit determination for LEO satellites with single-frequency GPS measurements is discussed first,and then, estimating the scale factor of ionosphere to remove the ionospheric effects in C/A code pseudo-range measurements in both kinematic and adynamia orbit defemination approaches is addressed. As it is known the ionospheric path delay of space-borne GPS signals is strongly dependent on the orbit altitudes of LEO satellites, we selected real space-borne GPS data from CHAMP, GRACE, TerraSAR-X and SAC-C satellites with altitudes between 300 km and 800 km as sample data in this paper. It is demonstrated that the approach of eliminating ionospheric effects in space-borne C/A code pseudo-range by estimating the scale factor of ionosphere is highly effective. Employing this approach, the accuracy of both kinematic and dynamic orbits can be improved notably. Among those five LEO satellites, CHAMP with the lowest orbit altitude has the most remarkable orbit accuracy improvements, which are 55.6% and 47.6% for kinematic and dynamic approaches, respectively. SAC-C with the highest orbit altitude has the least orbit accuracy improvements accordingly, which are 47.8% and 38.2%, respectively.

Peng, D. J.; Wu, B.

2012-01-01

327

NASA Astrophysics Data System (ADS)

We provide updated quasi-static and high-frequency analysis and calibration of the Radio and Plasma Wave (RPW) antenna system aboard the Solar Orbiter spacecraft, whose aim is to determine the dynamics of solarwind plasma and the electric and magnetic fields in the near-Sun heliosphere with a full suite of in-situ and remote sensing instruments. The mission is planned to be launched in 2017 with a spacecraft trajectory of partial co-rotation with the Sun. Finding the true reception properties of the RPW requires not only accurate modeling of the three cylindrical antennas forming the electric sensors, but also of the spacecraft body and attached hardware. As the spacecraft will be within 0.25 AU to the sun, the antennas will also be exposed to high solar radiation and subject to strong thermal stress loads which we consider as well. The current analysis is an important step forward as our models are based on the latest spacecraft specifications which are in an advanced development stage with much of the configuration having already been finalized by ESA. The current focus is on obtaining calibration results from numerical computation of the governing field equations, resulting in surface current distributions from which the effective axes and lengths and impedance matrices for the quasi-static range are derived. This improves the instrument's performance in both remote sensing as well as in-situ capabilities. This will also complement efforts to compare with experimental data that will soon be available, including results from anechoic chamber studies performed with scale models, providing an important benchmark for the numerical results. The current calibration results are to provide useful input to goniopolarimetry techniques like polarization analysis, direction finding and ray tracing, all of which depend crucially on the effective axes, thus providing significant improvements to the corresponding data analysis.Preliminary mesh of the Solar Orbiter used for numerical calculations.

Kapper, M.; Sampl, M.; Plettemeier, D.; Rucker, H. O.; Maksimovic, M.

2012-12-01

328

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

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

2001-08-15

329

NASA Technical Reports Server (NTRS)

A recent mathematical technique for solving systems of equations is applied in a very general way to the orbit determination problem. The study of this technique, the homotopy continuation method, was motivated by the possible need to perform early orbit determination with the Tracking and Data Relay Satellite System (TDRSS), using range and Doppler tracking alone. Basically, a set of six tracking observations is continuously transformed from a set with known solution to the given set of observations with unknown solutions, and the corresponding orbit state vector is followed from the a priori estimate to the solutions. A numerical algorithm for following the state vector is developed and described in detail. Numerical examples using both real and simulated TDRSS tracking are given. A prototype early orbit determination algorithm for possible use in TDRSS orbit operations was extensively tested, and the results are described. Preliminary studies of two extensions of the method are discussed: generalization to a least-squares formulation and generalization to an exhaustive global method.

Smith, R. L.; Huang, C.

1986-01-01

330

Federal Register 2010, 2011, 2012, 2013, 2014

...Grant of Summary Determination on the Merits; Termination of the Investigation AGENCY...determination of no importation on the merits and terminates the investigation. FOR...determination appropriately considers the merits, and the Commission affirms the...

2012-08-27

331

NASA Astrophysics Data System (ADS)

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

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

332

NASA Astrophysics Data System (ADS)

An analysis of Lunar Laser Ranging (LLR) observations from January 1972 until April 2001 has been performed, and a new solution for the lunar orbital motion and librations has been constructed that has been named S2001. With respect to prior solutions, improvements in the statistical treatment of the data, new nutation and libration models and the addition of the positions of the observing stations to the list of fitted parameters have been introduced. Globally, for recent observations, our rms (root mean square error) is within 2 to 3 centimeters in the lunar distance. Special attention has been paid to the determination of the correction to the IAU76 luni-solar constant of precession, and the value of the secular acceleration of the Moon's longitude due to the tidal forces. The main results are: - correction to the constant of precession: Delta p = -0.302 +/- 0.003 ''/cy, - tidal acceleration of the lunar longitude: Gamma = -25.858 +/- 0.003 ''/cy2. The positions and velocities of the stations have also been determined. The results are consistent with the ITRF2000 determinations from SLR observations. The lunar theory ELP is referred to a dynamical system and introduces the inertial mean ecliptic of J2000.0. The positioning of the reference system of the theory with respect to ICRS is performed (and also with respect to some useful JPL numerical integrations). Finally the orientation of the celestial axes with respect to the ICRS reference system has been derived as well as the offsets of the Celestial Ephemeris Pole.

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

2002-05-01

333

The Cooling Rate of an Active Aa Lava Flow Determined Using an Orbital Imaging Spectrometer

NASA Astrophysics Data System (ADS)

The surface temperature of an active lava flow is an important physical property to measure. Through its influence on lava crystallinity, cooling exerts a fundamental control on lava rheology. Remotely sensed thermal radiance data acquired by multispectral sensors such as Landsat Thematic Mapper and the Terra Advanced Spaceborne Thermal Emission and Reflection Radiometer, are of insufficient spectral and radiometric fidelity to allow for realistic determination of lava surface temperatures from Earth orbit. This paper presents results obtained from the analysis of active lava flows using hyperspectral data acquired by NASA's Earth Observing-1 Hyperion imaging spectrometer. The contiguous nature of the measured radiance spectrum in the 0.4-2.5 micron region means that, although sensor saturation most certainly occurs, unsaturated radiance data are always available from even the hottest, and most radiant, active lava flow surfaces. The increased number of wavebands available allows for the assumption of more complex flow surface temperature distributions in the radiance-to-temperature inversion processes. The technique is illustrated by using a hyperspectral image of the active lava lake at Erta Ale volcano, Ethiopia, a well characterized calibration target. We then go on to demonstrate how this approach can be used to constrain the surface cooling rate of an active lava flow at Mount Etna, Sicily, using three images acquired during a four day period in September 2004. The cooling rate of the active channel as determined from space falls within the limits commonly assumed in numerical lava flow models. The results provide insights into the temperature-radiance mixture modeling problem that will aid in the analysis of data acquired by future hyperspectral remote sensing missions, such as NASA's proposed HyspIRI mission.

Wright, Robert; Garbeil, Harold

2010-05-01

334

50 CFR 600.1004 - Accepting a request for, and determinations about initiating, a financed program.

Code of Federal Regulations, 2010 CFR

...OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE MAGNUSON-STEVENS ACT PROVISIONS Fishing Capacity Reduction Framework § 600.1004 Accepting a request for, and determinations about initiating, a financed program. (a) Accepting...

2010-10-01

335

50 CFR 600.1004 - Accepting a request for, and determinations about initiating, a financed program.

Code of Federal Regulations, 2011 CFR

...OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE MAGNUSON-STEVENS ACT PROVISIONS Fishing Capacity Reduction Framework § 600.1004 Accepting a request for, and determinations about initiating, a financed program. (a) Accepting...

2011-10-01

336

32 CFR 320.8 - Appeal of initial adverse agency determination on correction or amendment.

Code of Federal Regulations, 2010 CFR

...Defense 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...

2010-07-01

337

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

Code of Federal Regulations, 2010 CFR

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

2010-04-01

338

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

Code of Federal Regulations, 2010 CFR

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

2010-04-01

339

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

2014-10-01

340

NASA Astrophysics Data System (ADS)

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.

Modenini, D.; Tortora, P.

2014-07-01

341

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

342

Lifetimes of lunar satellite orbits

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

343

NASA Astrophysics Data System (ADS)

The formation of biofilms by water microorganisms such as Pseudomonas aeruginosa in spacecraft water systems has been a matter of concern for long-duration space flight. Crewed spacecraft plumbing includes internal surfaces made of 316L stainless steel. Experiments were therefore undertaken to compare the ability of P. aeruginosa to grow in suspension, attach to stainless steel and to grow on stainless steel in low gravity on the space shuttle. Four categories of cultures were studied during two space shuttle flights (STS-69 and STS-77). Cultures on the ground were held in static horizontal or vertical cylindrical containers or were tumbled on a clinostat and activated under conditions identical to those for the flown cultures. The containers used on the ground and in flight were BioServe Space Technologies’ Fluid Processing Apparatus (FPA), an open-ended test tube with rubber septa that allows robotic addition of bacteria to culture media to initiate experiments and the addition of fixative to conclude experiments. Planktonic growth was monitored by spectrophotometry, and biofilms were characterized quantitatively by epifluorescence and scanning electron microscopy. In these experiments it was found that: (1) Planktonic growth in flown cultures was more extensive than in static cultures, as seen repeatedly in the history of space microbiology, and closely resembled the growth of tumbled cultures. (2) Conversely, the attachment of cells in flown cultures was as much as 8 times that in tumbled cultures but not significantly different from that in static horizontal and vertical cultures, consistent with the notion that flowing fluid reduces microbial attachment. (3) The final surface coverage in 8 days was the same for flown and static cultures but less by a factor of 15 in tumbled cultures, where coverage declined during the preceding 4 days. It is concluded that cell attachment to 316L stainless steel in the low gravity of orbital space flight is similar to that found in stagnant cultures at 1 x g. Research was supported by NASA contract NAGW-1197 to the University of Colorado.

Todd, Paul; Pierson, Duane L.; Allen, Britt; Silverstein, JoAnn

344

Cooling rate of some active lavas determined using an orbital imaging spectrometer

NASA Astrophysics Data System (ADS)

The surface temperature of an active lava flow is an important physical property to measure. Through its influence on lava crystallinity, cooling exerts a fundamental control on lava rheology. Remotely sensed thermal radiance data acquired by multispectral sensors such as Landsat Thematic Mapper and the Terra Advanced Spaceborne Thermal Emission and Reflection Radiometer are of insufficient spectral and radiometric fidelity to allow for realistic determination of lava surface temperatures from Earth orbit. This paper presents results obtained from the analysis of active lava flows using hyperspectral data acquired by NASA's Earth Observing-1 Hyperion imaging spectrometer. The contiguous nature of the measured radiance spectrum in the 0.4-2.5 ?m region means that, although sensor saturation most certainly occurs, unsaturated radiance data are always available from even the hottest, and most radiant, active lava flow surfaces. The increased number of wave bands available allows for the assumption of more complex flow surface temperature distributions in the radiance-to-temperature inversion processes. The technique is illustrated by using a hyperspectral image of the active lava lake at Erta Ale volcano, Ethiopia, a well-characterized calibration target, a time series of three Hyperion images of an active lava flow acquired during a 4 day period at Mount Etna, Sicily, as well as a lava flow erupted at Nyamuragira, Democratic Republic of Congo. The results provide insights into the temperature-radiance mixture modeling problem that will aid in the analysis of data acquired by future hyperspectral remote sensing missions, such as NASA's proposed HyspIRI mission.

Wright, Robert; Garbeil, Harold; Davies, Ashley G.

2010-06-01

345

Federal Register 2010, 2011, 2012, 2013, 2014

...Investigation No. 337-TA-880 Certain Linear Actuators; Commission Determination Not...telephone (202) 205-3041. Copies of non- confidential documents filed in connection...United States after importation of certain linear actuators by reason of infringement...

2013-08-07

346

The Use of Laser Altimetry in the Orbit and Attitude Determination of Mars Global Surveyor

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

347

, Pasadena, CA 91109, USA d Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, dynamics Meteorology a b s t r a c t The Mars Reconnaissance Orbiter (MRO) performs radio occultation (RO the measurements with numerical simulations by the NASA Ames Mars General Circulation Model, which demonstrate

Spiga, Aymeric

348

NASA Technical Reports Server (NTRS)

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

Kramer, Leonard

2014-01-01

349

Code of Federal Regulations, 2010 CFR

...false Appeal of Initial Determination of Threat Assessment based on criminal conviction...APPEAL AND WAIVER PROCEDURES FOR SECURITY THREAT ASSESSMENTS FOR INDIVIDUALS § 1515.5 Appeal of Initial Determination of Threat Assessment based on criminal...

2010-10-01

350

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

351

Modeling radiation forces acting on TOPEX/Poseidon for precision orbit determination

NASA Technical Reports Server (NTRS)

Geodetic satellites such as GEOSAT, SPOT, ERS-1, and TOPEX/Poseidon require accurate orbital computations to support the scientific data they collect. Until recently, gravity field mismodeling was the major source of error in precise orbit definition. However, albedo and infrared re-radiation, and spacecraft thermal imbalances produce in combination no more than a 6-cm radial root-mean-square (RMS) error over a 10-day period. This requires the development of nonconservative force models that take the satellite's complex geometry, attitude, and surface properties into account. For TOPEX/Poseidon, a 'box-wing' satellite form was investigated that models the satellite as a combination of flat plates arranged in a box shape with a connected solar array. The nonconservative forces acting on each of the eight surfaces are computed independently, yielding vector accelerations which are summed to compute the total aggregate effect on the satellite center-of-mass. In order to test the validity of this concept, 'micro-models' based on finite element analysis of TOPEX/Poseidon were used to generate acceleration histories in a wide variety of orbit orientations. These profiles are then compared to the box-wing model. The results of these simulations and their implication on the ability to precisely model the TOPEX/Poseidon orbit are discussed.

Marshall, J. A.; Luthcke, S. B.; Antreasian, P. G.; Rosborough, G. W.

1992-01-01

352

Modeling radiation forces acting on TOPEX/Poseidon for precision orbit determination

NASA Astrophysics Data System (ADS)

Geodetic satellites such as GEOSAT, SPOT, ERS-1, and TOPEX/Poseidon require accurate orbital computations to support the scientific data they collect. Until recently, gravity field mismodeling was the major source of error in precise orbit definition. However, albedo and infrared re-radiation, and spacecraft thermal imbalances produce in combination no more than a 6-cm radial root-mean-square (RMS) error over a 10-day period. This requires the development of nonconservative force models that take the satellite's complex geometry, attitude, and surface properties into account. For TOPEX/Poseidon, a 'box-wing' satellite form was investigated that models the satellite as a combination of flat plates arranged in a box shape with a connected solar array. The nonconservative forces acting on each of the eight surfaces are computed independently, yielding vector accelerations which are summed to compute the total aggregate effect on the satellite center-of-mass. In order to test the validity of this concept, 'micro-models' based on finite element analysis of TOPEX/Poseidon were used to generate acceleration histories in a wide variety of orbit orientations. These profiles are then compared to the box-wing model. The results of these simulations and their implication on the ability to precisely model the TOPEX/Poseidon orbit are discussed.

Marshall, J. A.; Luthcke, S. B.; Antreasian, P. G.; Rosborough, G. W.

1992-06-01

353

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

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

2012-07-10

354

Thyroid-associated ophthalmopathy, a process in which the orbital tissues become inflamed and are remodeled, occurs with a variable presentation. In some patients, eye muscle enlargement predominates. In others, the connective\\/adipose tissue enlargement appears the more significant problem. Or- bital fibroblasts exhibit heterogeneous phenotypes in culture. Here we report that fibroblasts derived from the connective\\/ adipose tissue depot are distinct from

TERRY J. SMITH; LAURA KOUMAS; ANNEMARIE GAGNON; ANDREA BELL; GREGORY D. SEMPOWSKI; RICHARD P. PHIPPS; ALEXANDER SORISKY

355

Modified Kalman filter based autonomous orbit determination using horizon scanner measurements

With a pair of Horizon Scanners (HS) working as attitude sensors, four horizon points are obtained during each scan. A simplified non-linear model is developed for the horizon points using an appropriate choice of frame. The modified gain extended Kaiman filter is used to estimate the satellite position in the orbit reference frame based on the non-linear Horizon Scanner data.

K. Kasturirangan; M. S. Bhat

1996-01-01

356

VizieR Online Data Catalog: Orbit determination f & g power series (Bem+, 1995)

NASA Astrophysics Data System (ADS)

The table of coefficients and exponents of the power series f and g up to derivatives of the 20-th order is the main achievement of this paper. The accuracy of the calculation of orbits has been tested by tracing the motion of all planets of the solar system. (1 data file).

Bem, J.; Szczodrowska-Kozar, B.

1994-11-01

357

GPS attitude determination for a JPALS testbed: Integer initialization and testing

An attitude-based search algorithm was implemented for initial ambiguity resolution and integer determination, and then tested on a three-element equilateral array with baselines of 0.5m. Running the initialization algorithm at every epoch, it was found that the search algorithm gave efficient and reliable integer solutions for a static antenna array, but was sensitive to errors in a dynamic environment in

David S. De Lorenzo; Santiago Alban; Jennifer Gautier; Per Enge

2004-01-01

358

Appropriate distribution of time and energy between work and personal life poses a challenge to many working people. Unfortunately, many professionally active people experience work-family conflict. In order to minimize it, employees are offered various solutions aimed at reconciling professional and private spheres (work-life balance (WLB) initiatives). The authors attempt to answer what makes employees use WLB initiatives and what influences the decision to reject the available options. The review is based on the articles published after 2000, searched by Google Scholar and Web of Knowledge with use of the key words: work-life balance, work-family conflict, work-life balance initiatives, work-life balance initiatives use, use of WLB solutions. We focused on organizational and individual determinants of WLB initiatives use, such as organizational culture, stereotypes and values prevailing in the work environment that may result in stigmatization of workers - flexibility stigma. We discuss the reasons why supervisors and co-workers stigmatize their colleagues, and what are the consequences of experiencing such stigmatization. Among the individual determinants of WLB initiatives use, we have inter alia focused on the preference for integration vs. separation of the spheres of life. The presented material shows that social factors - cultural norms prevailing in a society, relationships in the workplace and individual factors, such as the level of self-control - are of equal importance for decisions of using WLB initiatives as their existence. Our conclusion is that little attention has been paid to the research on determinants of WLB initiatives use, especially to individual ones. PMID:24834699

Andysz, Aleksandra; Najder, Anna; Merecz-Kot, Dorota

2014-01-01

359

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

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

2012-01-01

360

J-Adaptive estimation with estimated noise statistics. [for orbit determination

NASA Technical Reports Server (NTRS)

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.

Jazwinski, A. H.; Hipkins, C.

1975-01-01

361

Determination of the area and mass distribution of orbital debris fragments

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

Gautam D. Badhwar; Phillip D. Anz-Meador

1989-01-01

362

AN ANALYTIC METHOD TO DETERMINE HABITABLE ZONES FOR S-TYPE PLANETARY ORBITS IN BINARY STAR SYSTEMS

With more and more extrasolar planets discovered in and around binary star systems, questions concerning the determination of the classical habitable zone have arisen. Do the radiative and gravitational perturbations of the second star influence the extent of the habitable zone significantly, or is it sufficient to consider the host star only? In this article, we investigate the implications of stellar companions with different spectral types on the insolation a terrestrial planet receives orbiting a Sun-like primary. We present time-independent analytical estimates and compare them to insolation statistics gained via high precision numerical orbit calculations. Results suggest a strong dependence of permanent habitability on the binary's eccentricity, as well as a possible extension of habitable zones toward the secondary in close binary systems.

Eggl, Siegfried; Pilat-Lohinger, Elke; Gyergyovits, Markus; Funk, Barbara [Institute for Astronomy, University of Vienna, Tuerkenschanzstr. 17, A-1180 Vienna (Austria); Georgakarakos, Nikolaos, E-mail: siegfried.eggl@univie.ac.at, E-mail: elke.pilat-lohinger@univie.ac.at [128 V. Olgas str., Thessaloniki 546 45 (Greece)

2012-06-10

363

THE SYNERGY OF DIRECT IMAGING AND ASTROMETRY FOR ORBIT DETERMINATION OF EXO-EARTHS

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.

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

364

Magnitude determination using initial P waves: A single-station Yih-Min Wu,1

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

Wu, Yih-Min

365

The Validity of Nutrition Screening Initiative DETERMINE Checklist Responses in Older Georgians

The Nutrition Screening Initiative DETERMINE Checklist (NSI) is used throughout the United States to assess nutrition risk of those requesting the services of the Older Americans Act Nutrition Program (OAANP). This study examined the ability of the NSI to evaluate nutrition risk by comparing the responses between NSI and matched comparable survey questions using the self-administered mail survey data that

Stephanie Sinnett; Rebecca Bengle; Arvine Brown; Anne P. Glass; Mary Ann Johnson; Jung Sun Lee

2010-01-01

366

RXTE dips yield better orbital period determination for MAXI J1659-152

NASA Astrophysics Data System (ADS)

We analyzed 32 RXTE/PCA observations of MAXI J1659-152 (Negoro et al. 2010, ATel #2873; Mangano et al. 2010, GCN #11296) from UT 2010 Sep 28 through to 2010 Oct 11. The total exposure is 72.5 ks. We produced light curves from PCU2 with 16-s bins over the full PCA range and over the 2-4.5 keV range. Since the average count rate of the source increases secularly because of the ongoing outburst, for each observation interval (corresponding to an RXTE orbit) we subtracted the mean count rate.

Belloni, T. M.; Muñoz-Darias, T.; Kuulkers, E.

2010-10-01

367

NASA Technical Reports Server (NTRS)

The destruction rates of a perfluoropolyether (PFPE) lubricant, Krytox 143AC, subjected to rolling contact with 440C steel in a spiral orbit tribometer at room temperature have been evaluated as a function of test environment. The rates in ultrahigh vacuum, 0.213 kPa (1.6 torr) oxygen and one atmosphere of dry nitrogen were about the same. Water vapor in the test environment-a few ppm in one atmosphere of nitrogen-reduced the destruction rate by up to an order of magnitude. A similar effect of water vapor was found for the destruction rate of Pennzane 2001A, an unformulated multiply alkylated cyclopentane (MAC) hydrocarbon oil.

Pepper, Stephen V.

2011-01-01

368

NASA Technical Reports Server (NTRS)

In the spring of 1993, the MOMS-02 (modular Optoelectronic Multispectral Scanner) camera, as part of the second German Spacelab mission aboard STS-55, successfully took digital threefold stereo images of the surface of the Earth. While the mission is experimental in nature, its primary goals are to produce high quality maps and three-dimensional digital terrain models of the Earth's surface. Considerable improvement in the quality of the terrain model can be attained if information about the position and attitude of the camera is included during the adjustment of the image data. One of the primary sources of error in the Shuttle's position is due to the significant attitude maneuvers conducted during the course of the mission. Various arcs, using actual Tracking and Data Relay Satellite (TDRSS) Doppler data of STS-55, were processed to determine how effectively empirical force modeling could be used to solve for the radial, transverse, and normal components of the orbit perturbations caused by these routine maneuvers. Results are presented in terms of overlap-orbit differences in the three components. Comparisons of these differences, before and after the maneuvers are estimated, show that the quality of an orbit can be greatly enhanced with this technique, even if several maneuvers are present. Finally, a discussion is made of some of the difficulties encountered with this approach, and some ideas for future studies are presented.

Vonbraun, C.; Reigber, Christoph

1994-01-01

369

NASA Astrophysics Data System (ADS)

The Be/X-ray binary transient pulsar EXO 2030+375 (Ps~ 42s) has been observed using the large area detectors (LADs) of the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma-Ray Observatory (CGRO). Beginning in May 1991, twenty-one outbursts were observed over four years. Thirteen outbursts between February 1992 and August 1993 occurred regularly at intervals of ~46 days, close to the orbital period determined by Parmar et al. (1989) using EXOSAT data. The pulse profile from the BATSE data was double-peaked and showed no significant energy- or luminosity-dependence in contrast to the EXOSAT observations of May-August 1985. An exponential model was used to fit the observed hard X-ray spectra from the thirteen consecutive outbursts. A possible hard-to-soft evolution of kT with integrated flux was seen during some of the brighter outbursts that appeared not to be solely related to the pulsar's mass accretion rate. When EXOSAT discovered this pulsar during a 'giant' outburst in May 1985 (Parmar et al. 1985), the X-ray luminosity was Lx=1.0 ? 1038 erg s-1 (1-20 keV), assuming a 5 kpc distance to the source (Parmar et al. 1989). The BATSE outbursts were found to be weaker (0.32>= Lx (1-20 keV) >=3.2 ? 1036 erg s-1) after extrapolating the observed flux (20-50 keV) to the EXOSAT energy band. Pulse phases derived from these thirteen outbursts were fit to two different models to determine a binary orbit. The new orbit was used to estimate 95% confidence limits for the mean peak spin frequency change during the outbursts observed with BATSE. This, and the mean peak flux, were compared to the spin-up rates and fluxes determined by EXOSAT from the 1985 'giant' outburst, where disk accretion was thought to have occurred.

Stollberg, Mark Thomas

370

Determination of laser damage initiation probability and growth on fused silica scratches

Current methods for the manufacture of optical components inevitably leaves a variety of sub-surface imperfections including scratches of varying lengths and widths on even the finest finishes. It has recently been determined that these finishing imperfections are responsible for the majority of laser-induced damage for fluences typically used in ICF class lasers. We have developed methods of engineering subscale parts with a distribution of scratches mimicking those found on full scale fused silica parts. This much higher density of scratches provides a platform to measure low damage initiation probabilities sufficient to describe damage on large scale optics. In this work, damage probability per unit scratch length was characterized as a function of initial scratch width and post fabrication processing including acid-based etch mitigation processes. The susceptibility of damage initiation density along scratches was found to be strongly affected by the post etching material removal and initial scratch width. We have developed an automated processing procedure to document the damage initiations per width and per length of theses scratches. We show here how these tools can be employed to provide predictions of the performance of full size optics in laser systems operating at 351 nm. In addition we use these tools to measure the growth rate of a damage site initiated along a scratch and compare this to the growth measured on an isolated damage site.

Norton, M A; Carr, C W; Cross, D A; Negres, R A; Bude, J D; Steele, W A; Monticelli, M V; Suratwala, T I

2010-10-26

371

Modified Kalman filter based autonomous orbit determination using horizon scanner measurements

NASA Astrophysics Data System (ADS)

With a pair of Horizon Scanners (HS) working as attitude sensors, four horizon points are obtained during each scan. A simplified non-linear model is developed for the horizon points using an appropriate choice of frame. The modified gain extended Kaiman filter is used to estimate the satellite position in the orbit reference frame based on the non-linear Horizon Scanner data. Through simulation studies it is shown that addition of one more scanner in the roll-yaw plane provides accurate estimates of the position. Under steady state conditions, simulation results show that estimates do not diverge even if there is a data break in the roll-yaw HS data. The achievable accuracies are of the order of 2 km with about 0.1 °(1?) noise in the horizon points.

Nagarajan, N.; Bhat, M. Seetharama; Kasturirangan, K.

1996-05-01

372

The value of the initial velocity of the stream meteoroids from the parent bodies is given by the physics of the outgassing of the cometary nuclei and by modeling the collisions between asteroids. In both cases the outflow speed of the meteoroid particles are small (Whipple 1951, Hughes 1977, 2000, Gustafson 1989, Jones 1995, Ma et al. 2002) and as

T. J. Jopek; R. Rudawska; P. A. Dybczynski

2005-01-01

373

Background: The identification of the factors associated with severe asthma may shed some light on its etiology and on the mechanisms of its development. We aimed to describe asthma severity using the Global Initiative for Asthma (GINA) classification and to investigate its determinants in a cross-sectional, population-based sample in Europe. Methods: In the European Community Respiratory Health Survey II (1999–2002),

Lucia Cazzoletti; Alessandro Marcon; Angelo Corsico; Christer Janson; Deborah Jarvis; Isabelle Pin; Simone Accordini; Massimiliano Bugiani; Isa Cerveri; David Gislason; Amund Gulsvik; Roberto de Marco

2010-01-01

374

NASA Astrophysics Data System (ADS)

We describe the physical and orbital properties of C/2011 W3. After surviving perihelion passage, the comet was observed to undergo major physical changes. The permanent loss of the nuclear condensation and the formation of a narrow spine tail were observed first at Malargue, Argentina, on December 20 and then systematically at Siding Spring, Australia. The process of disintegration culminated with a terminal fragmentation event on December 17.6 UT. The postperihelion dust tail, observed for ~3 months, was the product of activity over <2 days. The nucleus' breakup and crumbling were probably caused by thermal stress due to the penetration of the intense heat pulse deep into the nucleus' interior after perihelion. The same mechanism may be responsible for cascading fragmentation of sungrazers at large heliocentric distances. The delayed response to the hostile environment in the solar corona is at odds with the rubble-pile model, since the residual mass of the nucleus, estimated at ~1012 g (equivalent to a sphere 150-200 m across) just before the terminal event, still possessed nontrivial cohesive strength. The high production rates of atomic oxygen, observed shortly after perihelion, are compatible with a subkilometer-sized nucleus. The spine tail—the product of the terminal fragmentation—was a synchronic feature, whose brightest part contained submillimeter-sized dust grains, released at velocities of up to 30 m s-1. The loss of the nuclear condensation prevented an accurate orbital-period determination by traditional techniques. Since the missing nucleus must have been located on the synchrone, whose orientation and sunward tip have been measured, we compute the astrometric positions of this missing nucleus as the coordinates of the points of intersection of the spine tail's axis with the lines of forced orbital-period variation, derived from the orbital solutions based on high-quality preperihelion astrometry from the ground. The resulting orbit gives 698 ± 2 yr for the osculating orbital period, showing that C/2011 W3 is the first member of the expected new, 21st-century cluster of bright Kreutz-system sungrazers, whose existence was predicted by these authors in 2007. From the spine tail's evolution, we determine that its measured tip, populated by dust particles 1-2 mm in diameter, receded antisunward from the computed position of the missing nucleus. The bizarre appearance of the comet's dust tail in images taken only hours after perihelion with the coronagraphs on board the SOHO and STEREO spacecraft is readily understood. The disconnection of the comet's head from the tail released before perihelion and an apparent activity attenuation near perihelion have a common cause—sublimation of all dust at heliocentric distances smaller than about 1.8 solar radii. The tail's brightness is strongly affected by forward scattering of sunlight by dust. From an initially broad range of particle sizes, the grains that were imaged the longest had a radiation-pressure parameter ? ~= 0.6, diagnostic of submicron-sized silicate grains and consistent with the existence of the dust-free zone around the Sun. The role and place of C/2011 W3 in the hierarchy of the Kreutz system and its genealogy via a 14th-century parent suggest that it is indirectly related to the celebrated sungrazer X/1106 C1, which, just as the first-generation parent of C/2011 W3, split from a common predecessor during the previous return to perihelion.

Sekanina, Zdenek; Chodas, Paul W.

2012-10-01

375

We describe the physical and orbital properties of C/2011 W3. After surviving perihelion passage, the comet was observed to undergo major physical changes. The permanent loss of the nuclear condensation and the formation of a narrow spine tail were observed first at Malargue, Argentina, on December 20 and then systematically at Siding Spring, Australia. The process of disintegration culminated with a terminal fragmentation event on December 17.6 UT. The postperihelion dust tail, observed for {approx}3 months, was the product of activity over <2 days. The nucleus' breakup and crumbling were probably caused by thermal stress due to the penetration of the intense heat pulse deep into the nucleus' interior after perihelion. The same mechanism may be responsible for cascading fragmentation of sungrazers at large heliocentric distances. The delayed response to the hostile environment in the solar corona is at odds with the rubble-pile model, since the residual mass of the nucleus, estimated at {approx}10{sup 12} g (equivalent to a sphere 150-200 m across) just before the terminal event, still possessed nontrivial cohesive strength. The high production rates of atomic oxygen, observed shortly after perihelion, are compatible with a subkilometer-sized nucleus. The spine tail-the product of the terminal fragmentation-was a synchronic feature, whose brightest part contained submillimeter-sized dust grains, released at velocities of up to 30 m s{sup -1}. The loss of the nuclear condensation prevented an accurate orbital-period determination by traditional techniques. Since the missing nucleus must have been located on the synchrone, whose orientation and sunward tip have been measured, we compute the astrometric positions of this missing nucleus as the coordinates of the points of intersection of the spine tail's axis with the lines of forced orbital-period variation, derived from the orbital solutions based on high-quality preperihelion astrometry from the ground. The resulting orbit gives 698 {+-} 2 yr for the osculating orbital period, showing that C/2011 W3 is the first member of the expected new, 21st-century cluster of bright Kreutz-system sungrazers, whose existence was predicted by these authors in 2007. From the spine tail's evolution, we determine that its measured tip, populated by dust particles 1-2 mm in diameter, receded antisunward from the computed position of the missing nucleus. The bizarre appearance of the comet's dust tail in images taken only hours after perihelion with the coronagraphs on board the SOHO and STEREO spacecraft is readily understood. The disconnection of the comet's head from the tail released before perihelion and an apparent activity attenuation near perihelion have a common cause-sublimation of all dust at heliocentric distances smaller than about 1.8 solar radii. The tail's brightness is strongly affected by forward scattering of sunlight by dust. From an initially broad range of particle sizes, the grains that were imaged the longest had a radiation-pressure parameter {beta} {approx_equal} 0.6, diagnostic of submicron-sized silicate grains and consistent with the existence of the dust-free zone around the Sun. The role and place of C/2011 W3 in the hierarchy of the Kreutz system and its genealogy via a 14th-century parent suggest that it is indirectly related to the celebrated sungrazer X/1106 C1, which, just as the first-generation parent of C/2011 W3, split from a common predecessor during the previous return to perihelion.

Sekanina, Zdenek; Chodas, Paul W., E-mail: Zdenek.Sekanina@jpl.nasa.gov, E-mail: Paul.W.Chodas@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)

2012-10-01

376

NASA Astrophysics Data System (ADS)

The Large-Area Telescope (LAT) on the Fermi gamma-Ray Space Telescope is a pair-conversion gamma-ray telescope with unprecedented capability to image astrophysical gamma-ray sources between 20 MeV and 300 GeV. The pre-launch performance of the LAT, decomposed into effective area, energy and angular dispersions, were determined through extensive Monte Carlo (MC) simulations and beam tests. The point-spread function (PSF) characterizes the angular distribution of reconstructed photons as a function of energy and geometry in the detector. Here we present a set of likelihood analyses of LAT data based on the spatial and spectral properties of sources, including a determination of the PSF on orbit. We find that the PSF on orbit is generally broader than the MC at energies above 3 GeV and consider several systematic effects to explain this difference. We also investigated several possible spatial models for pair-halo emission around BL Lac AGN and found no evidence for a component with spatial extension larger than the PSF.

Roth, Marshall

377

We discuss the analytical determination of the location of the Last Stable Orbit (LSO) in circular general relativistic orbits of two point masses. We use several different ``resummation methods'' (including new ones) based on the consideration of gauge-invariant functions, and compare the results they give at the third post-Newtonian (3PN) approximation of general relativity. Our treatment is based on the 3PN Hamiltonian of Jaranowski and Sch\\"afer. One of the new methods we introduce is based on the consideration of the (invariant) function linking the angular momentum and the angular frequency. We also generalize the ``effective one-body'' approach of Buonanno and Damour by introducing a non-minimal (i.e. ``non-geodesic'') effective dynamics at the 3PN level. We find that the location of the LSO sensitively depends on the (currently unknown) value of the dimensionless quantity $\\oms$ which parametrizes a certain regularization ambiguity of the 3PN dynamics. We find, however, that all the analytical methods we use numerically agree between themselves if the value of this parameter is $\\oms\\simeq-9$. This suggests that the correct value of $\\oms$ is near -9 (the precise value $\\oms^*\\equiv-{47/3}+{41/64}\\pi^2=-9.3439...$ seems to play a special role). If this is the case, we then show how to further improve the analytical determination of various LSO quantities by using a ``Shanks'' transformation to accelerate the convergence of the successive (already resummed) PN estimates.

Thibault Damour; Piotr Jaranowski; Gerhard Schaefer

2000-05-10

378

NASA Technical Reports Server (NTRS)

Spacecraft in low Earth orbit (LEO) are subjected to many components of the environment, which can cause them to degrade much more rapidly than intended and greatly shorten their functional life. The atomic oxygen, ultraviolet radiation, and cross contamination present in LEO can affect sensitive surfaces such as thermal control paints, multilayer insulation, solar array surfaces, and optical surfaces. The LEO Spacecraft Materials Test (LEO-SMT) program is being conducted to assess the effects of simulated LEO exposure on current spacecraft materials to increase understanding of LEO degradation processes as well as to enable the prediction of in-space performance and durability. Using ground-based simulation facilities to test the durability of materials currently flying in LEO will allow researchers to compare the degradation evidenced in the ground-based facilities with that evidenced on orbit. This will allow refinement of ground laboratory test systems and the development of algorithms to predict the durability and performance of new materials in LEO from ground test results. Accurate predictions based on ground tests could reduce development costs and increase reliability. The wide variety of national and international materials being tested represent materials being functionally used on spacecraft in LEO. The more varied the types of materials tested, the greater the probability that researchers will develop and validate predictive models for spacecraft long-term performance and durability. Organizations that are currently participating in the program are ITT Research Institute (USA), Lockheed Martin (USA), MAP (France), SOREQ Nuclear Research Center (Israel), TNO Institute of Applied Physics (The Netherlands), and UBE Industries, Ltd. (Japan). These represent some of the major suppliers of thermal control and sensor materials currently flying in LEO. The participants provide materials that are exposed to selected levels of atomic oxygen, vacuum ultraviolet radiation, contamination, or synergistic combined environments at the NASA Lewis Research Center. Changes in characteristics that could affect mission performance or lifetime are then measured. These characteristics include changes in mass, solar absorptance, and thermal emittance. The durability of spacecraft materials from U.S. suppliers is then compared with those of materials from other participating countries. Lewis will develop and validate performance and durability prediction models using this ground data and available space data. NASA welcomes the opportunity to consider additional international participants in this program, which should greatly aid future spacecraft designers as they select materials for LEO missions.

Rutledge, Sharon K.

1999-01-01

379

Conversion of Osculating Orbital Elements to Mean Orbital Elements

NASA Technical Reports Server (NTRS)

Orbit determination and ephemeris generation or prediction over relatively long elapsed times can be accomplished with mean elements. The most simple and efficient method for orbit determination, which is also known as epoch point conversion, performs the conversion of osculating elements to mean elements by iterative procedures. Previous epoch point conversion methods are restricted to shorter elapsed times with linear convergence. The new method presented in this paper calculates an analytic initial guess of the unknown mean elements from a first order theory of secular perturbations and computes a transition matrix with accurate numerical partials. It thereby eliminates the problem of an inaccurate initial guess and an identity transition matrix employed by previous methods. With a good initial guess of the unknown mean elements and an accurate transition matrix, converging osculating elements to mean elements can be accomplished over long elapsed times with quadratic convergence.

Der, Gim J.; Danchick, Roy

1996-01-01

380

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

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

381

Code of Federal Regulations, 2010 CFR

...UNITED STATES INTERNATIONAL TRADE COMMISSION INVESTIGATIONS OF UNFAIR PRACTICES IN IMPORT TRADE ADJUDICATION AND ENFORCEMENT...investigation may request Commission review of an initial determination issued under §...

2010-04-01

382

GIOVE-B solar radiation pressure modeling for precise orbit determination

NASA Astrophysics Data System (ADS)

Previous studies have identified systematic errors in the orbit and clock estimates of the GIOVE and Galileo IOV satellites in the order of ± 20 cm. These errors are visible as periodic variations in the Satellite Laser Ranging (SLR) and clock residuals. For IOV, these variations could be attributed to the contribution of a stretched satellite body and it was shown that a simple a priori box model for the solar radiation pressure can significantly reduce these errors. GIOVE-B has similar dimensions as the IOV satellites but its orientation is different: for GIOVE-B the narrow side of the satellite points to the Earth rather than the longitudinal side. In addition, an extra plate carrying, amongst others, the laser retro reflector array is mounted on the spacecraft introducing shadowing effects. These features are considered with a simple box-plate model. This model reduces the periodic clock errors and the SLR residual RMS of GIOVE-B by a factor of two. Most importantly, the box-plate model reduces the SLR offset from 11 cm to less than 1 cm. The largest part of this reduction comes from considering the plate and its shadowing effects.

Steigenberger, Peter; Montenbruck, Oliver; Hugentobler, Urs

2015-03-01

383

Conservative force model performance for TOPEX/Poseidon precision orbit determination

NASA Astrophysics Data System (ADS)

The TOPEX/Poseidon spacecraft was launched on August 10, 1992 to study the Earth's oceans. To achieve maximum benefit from the altimetric data collected, mission requirements dictate that TOPEX/Poseidon's orbit must be computed at an unprecedented level of accuracy. In order to satisfy these requirements, a model which accounts for the satellite's complex geometry, attitude, and surface properties has been developed. This `box-wing' representation treats the spacecraft as the combination of flat plates arranged in the shape of a box and a connecetd solar array. The nonconservative forces acting on each of the eight surfaces are computed independently, yielding vector accelerations which are summed to compute the total aggregate effect on the satellite center-of-mass. Parameters associated with each flat plate were derived from a finite element analysis of the spacecraft. Certain parameters can be inferred from tracking data and have been adjusted to obtain a better representation of the satellite acceleration history. Changes in the nominal mission profile and the presence of an `anomalistic' force have complicated this tuning process. Model performance, parameter sensitivities, and the `anomalistic' force will be discussed.

Marshall, J. Andrew; Luthcke, Scott B.

384

Orbit Design of Earth-Observation Satellite

NASA Astrophysics Data System (ADS)

The purpose of this study is to design a reliable orbit for a medium-resolution scientific satellite to observe Earth for developmental issues such as water resources, agricultural, and industrial. To meet this objective this study firstly, defines the mission, secondly, determines mission constraints, thirdly, design the attitude and orbit control system. As for the observation requirements, and the revisit time are provided as a function of the orbital parameters. Initial orbital parameters are obtained by optimal analysis between observation characteristics and attitude and orbit maintenance costs. Long term station-keeping strategies will be provided for the proposed solutions. Impulsive control will be investigated to provide a reliable and affordable attitude and orbit control system.

Owis, Ashraf

385

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

Kim, Julianne; Iaboni, Dolores C.; Walker, Scott E.; Elligsen, Marion; Dunn, Michael S.; Allen, Vanessa G.; Simor, Andrew

2014-01-01

386

NSDL National Science Digital Library

This Science Object is the third of three Science Objects in the Gravity and Orbits SciPack. It provides an understanding of how gravitational forces influence the motion of an object in orbit. When a force acts toward a single center, an object's forward motion and its motion toward that center can combine to create a curved path around the center. Gravity governs the motion of all objects in the solar system. The Sun's gravitational pull holds the Earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them. Learning Outcomes:? Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.? Explain how an object orbits a planet in terms of trajectories and free fall.? Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.

National Science Teachers Association (NSTA)

2006-11-01

387

NASA Astrophysics Data System (ADS)

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.

Vilhena de Moraes, Rodolpho; Cristiane Pardal, Paula; Koiti Kuga, Helio

388

The bright southern binary star beta Centauri (HR 5267) has been observed with the Sydney University Stellar Interferometer (SUSI) and spectroscopically with the ESO CAT and Swiss Euler telescopes at La Silla. The interferometric observations have confirmed the binary nature of the primary component and have enabled the determination of the orbital parameters of the system. At the observing wavelength of 442 nm the two components of the binary system have a magnitude difference of 0.15. The combination of interferometric and spectroscopic data gives the following results: orbital period 357 days, semi-major axis 25.30 mas, inclination 67.4 degrees, eccentricity 0.821, distance 102.3 pc, primary and secondary masses M1 = M2 = 9.1 solar masses and absolute visual magnitudes of the primary and secondary M1V = -3.85 and M2V = -3.70. The high accuracy of the results offers a fruitful starting point for future asteroseismic modelling of the pulsating binary components.

Davis, J; Seneta, E B; Tango, W J; Booth, A J; O'Byrne, J W; Thorvaldson, E D; Ausseloos, M; Aerts, C; Uytterhoeven, K

2004-01-01

389

We discuss the analytical determination of the location of the Last Stable Orbit (LSO) in circular general relativistic orbits of two point masses. We use several different ``resummation methods'' (including new ones) based on the consideration of gauge-invariant functions, and compare the results they give at the third post-Newtonian (3PN) approximation of general relativity. Our treatment is based on the 3PN Hamiltonian of Jaranowski and Sch\\"afer. One of the new methods we introduce is based on the consideration of the (invariant) function linking the angular momentum and the angular frequency. We also generalize the ``effective one-body'' approach of Buonanno and Damour by introducing a non-minimal (i.e. ``non-geodesic'') effective dynamics at the 3PN level. We find that the location of the LSO sensitively depends on the (currently unknown) value of the dimensionless quantity $\\oms$ which parametrizes a certain regularization ambiguity of the 3PN dynamics. We find, however, that all the analytical methods...

Damour, Thibault Marie Alban Guillaume; Schäfer, G; Damour, Thibault; Jaranowski, Piotr; Schaefer, Gerhard

2000-01-01

390

NASA Astrophysics Data System (ADS)

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.

Niu, Ben; Zhang, Hao; Giblin, Daryl; Rempel, Don L.; Gross, Michael L.

2015-02-01

391

A study to explore the use of orbital remote sensing to determine native arid plant distribution

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. A theory has been developed of a method for determining the reflectivities of natural areas from ERTS-1 data. This method requires the following measurements: (1) ground truth reflectivity data from two different calibration areas; (2) radiance data from ERTS-1 MSS imagery for the same two calibration areas; and (3) radiance data from ERTS-1 MSS imagery for the area(s) in which reflectivity is to be determined. The method takes into account sun angle effects and atmospheric effects on the radiance seen by the space sensor. If certain assumptions are made, the ground truth data collection need not be simultaneous with the ERTS-1 overflight. The method allows the calculation of a conversion factor for converting ERTS-1 MSS radiance measurements of a given overflight to reflectivity values. This conversion factor can be used to determine the reflectivity of any area in the general vicinity of the calibration areas which has a relatively similar overlying atmosphere. This method, or some modification of it, may be useful in ERTS investigations which require the determination of spectral signatures of areas from spacecraft data.

Mcginnies, W. G. (principal investigator); Haase, E. F.; Musick, H. B. (compiler)

1973-01-01

392

Techniques for the determination of mass properties of earth-to-orbit transportation systems

NASA Technical Reports Server (NTRS)

One estimating technique involves trending whereby projections of overall mass properties of vehicles are determined with few inputs. The second technique involves trending of individual subsystems using equations of the form KXN to the nth power or KX. Some constants and exponentials are provided for sample subsystems. Mass properties are reported in a format recommended by mil spec - 38310.

Macconochie, I. O.; Klich, P. J.

1978-01-01

393

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

H. Mardirossian; K. Heuerman; A. Beri; M. V. Samii; C. E. Doll

1989-01-01

394

Long range orbital error estimation for applications satellites

NASA Technical Reports Server (NTRS)

A method of optimum orbital averaging was employed to study the long range accuracy potential of polar orbiting applications satellites. This approach involved the determination of the boundary conditions of one set of differential equations of motion by adjusting the initial conditions in a least square sense with the use of data generated by another set of differential equations of motion.

Bonavito, N. L.; Foreman, J. C.

1978-01-01

395

NASA Technical Reports Server (NTRS)

Measurements of Mars-orbit perturbations have been conducted in order to estimate the masses of the Ceres, Pallas, and Vesta asteroids. A full, least-squares adjustment of all ephemeris parameters, including the relevant asteroid masses, is compiled on the basis of observational data encompassing the highly accurate Viking Lander ranging data. The mass for Ceres, of 5.0 + or - 0.2 x 10 to the -10th solar masses, that for Pallas, of 1.4 + or - 0.2 x 10 to the -10th solar masses, and that for Vesta, of 1.5 + or - 0.3 x 10 to the -10th solar masses, respectively represent 15, 30, and 9 percent increases over Schubart's (1970, 1974, 1975) previous determinations.

Standish, E. Myles, Jr.; Hellings, Ronald W.

1989-01-01

396

A semiempirical molecular-orbital method (CAChe 4.9, PM5) was applied to delineate the relationship between the cytotoxicity (evaluated by 50% cytotoxic concentration, CC(50)) of twelve dihydroimidazole derivatives, their molecular weight and the eleven chemical parameters (descriptors) determined by CONFLEX/PM5 method. There was no correlation between the CC(50) value and heat of formation, dipole moment, E(HOMO), E(LUMO), absolute hardness (eta), absolute electron negativity (chi), reaction index (omega), length of substituted group in all cell lines tested. However, there was good correlation between the CC(50) and the log P, or molecular size in all cell lines used. Surface and volume calculated by this method are useful in evaluating the cytotoxicity of dihydroimidazole derivatives. PMID:20044611

Takekawa, Fumihiro; Sakagami, Hiroshi; Ishihara, Mariko

2009-12-01

397

NASA Technical Reports Server (NTRS)

To improve the orbits, all the positional observations of the comets were collected. The observations were selected and weighted according to objective mathematical criteria and the mean residuals a priori were calculated for both comets. We took into account nongravitational effects in the comets' motion using Marsden's method applied in two ways: either determining the three constant parameters, A(sub 1), A(sub 2), A(sub 3) or the four parameters A, eta, I, phi connected with the rotating nucleus of the comet. To link successfully all the observations, we had to assume for both comets that A(t) = A(sub O)exp(-B x t) where B was an additional nongravitational parameter.

Todorovic-Juchniewicz, Bozenna; Sitarski, Grzegorz

1992-01-01

398

NASA Astrophysics Data System (ADS)

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.

Królikowska, Ma?gorzata; Dybczy?ski, Piotr A.

2013-10-01

399

The NOVA-2 postlaunch orbit adjustment process

NASA Astrophysics Data System (ADS)

The NOVA-2 satellite was the last of three `drag free' spacecraft to be placed into the Transit Navigation Systems's constellation of satellites. After its launch from Vandenburg Air Force Base into an initial 510 x 170 nmi near poar orbit, an intensive two-week operations schedule was implemented to : raise the orbit approximately 450 nmi to within .015 sec of desired period, trim eccentricity to within .003, trim inclination to within .006 degrees of requirement, freeze the phase of the spacecraft in orbit relative to the other two `drag free' satellites, dump extra fuel by deliberately fual wasting burns, and transition the spacecraft from a slow spin mode to gravity gradient. This paper will briefly discuss the concept of a `drag free' satellite, the selection of the orbit plane in the constellations, and the derivation of the required final orbit parameters. The paper will also discuss peripheral support needed to assist the OATS (Orbit Adjust and Transfer System) ground software, including attitude determination and maneuvers, orbit determination, and orbit prediction through the burns. However, the specific focus of this paper is on the design and execution of the nine OATS burns that accomplished the orbital maneuvers.

Heyler, Gene A.

400

Within the GUINEVERE project (Generation of Uninterrupted Intense Neutrons at the lead Venus Reactor) carried out at SCK-CEN in Mol, the continuous deuteron accelerator GENEPI-3C was coupled to the VENUS-F fast simulated lead-cooled reactor. Today the FREYA project (Fast Reactor Experiments for hYbrid Applications) is ongoing to study the neutronic behavior of this Accelerator Driven System (ADS) during different phases of operation. In particular the set-up of a monitoring system for the subcriticality of an ADS is envisaged to guarantee safe operation of the installation. The methodology for subcriticality monitoring in ADS takes into account the determination of the initial subcriticality level, the monitoring of reactivity variations, and interim cross-checking. At start-up, the Pulsed Neutron Source (PNS) technique is envisaged to determine the initial subcriticality level. Thanks to its reference critical state, the PNS technique can be validated on the VENUS-F core. A detector positioning methodology for the PNS technique is set up in this paper for the subcritical VENUS-F core, based on the reduction of higher harmonics in a static evaluation of the Sjoestrand area method. A first case study is provided on the VENUS-F core. This method can be generalised in order to create general rules for detector positions and types for full-scale ADS. (authors)

Uyttenhove, W.; Van Den Eynde, G.; Baeten, P.; Kochetkov, A.; Vittiglio, G.; Wagemans, J. [SCKCEN, Belgian Nuclear Research Centre, Boeretang 200, BE-2400 Mol (Belgium); Lathouwers, D.; Kloosterman, J. L.; Van Der Hagen, T. J. H. H.; Wols, F. [Delft Univ. of Technology, Mekelweg 15, NL-2629 JB Delft (Netherlands); Billebaud, A.; Chabod, S.; Thybault, H. E. [LPSC-CNRS-IN2P3/UJF/INPG, 53, Avenue des Martyrs, 38026 Grenoble Cedex (France); Lecouey, J. L.; Ban, G.; Lecolley, F. R.; Marie, N.; Steckmeyer, J. C. [LPC Caen, ENSICAEN/Unicersit de Caen/CNRS-IN2P3, Caen (France); Dessagne, P.; Kerveno, M. [IPHC-DRS/UdS/CNRS-IN2P3, Strasbourg (France); Mellier, F. [CEA/DEN/DER/SPEX/LPE, Cadarache 13108 Saint-Paul-les-Durance (France)

2012-07-01